JP2015189036A - Semiconductor device, light exposure head and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow contamination brought about by an adhesive to be prevented without lowering reliability of operation.SOLUTION: A rear face of a semiconductor light-emitting element array chip 35 is adhered to a front face of a printed wiring board 34 through an adhesive 41, and at an end part, opposing to an adjacent semiconductor light-emitting element array chip 35, of the semiconductor light-emitting element array chip 35 are arranged level difference parts 46 lower than a front face 42 on which light-emitting parts 43 are formed. This allows the whole of the rear face of the semiconductor light-emitting element array chip 35 to be connected to the printed wiring board 34 by the adhesive, and further allows the adhesive 41, which creeps up through a capillary phenomenon from a gap between the adjacent semiconductor light-emitting element array chips 35, to be flown to the level difference parts 46 to be let out, so that the adhesive can be suppressed from creeping up to the front face 42 on which the light emitting parts 43 are formed.

Description

  The present invention relates to a semiconductor device, an exposure head, and an image forming apparatus. For example, the present invention is suitably applied to a print head in which a plurality of light emitting element array chips are mounted side by side on a substrate.

  2. Description of the Related Art Conventionally, an LED print head used in an LED (Light Emitting Diode) printer or the like has a structure in which a plurality of semiconductor light emitting element array chips are mounted on a printed wiring board. A plurality of light emitting portions are arranged in a one-dimensional array on the surface of each semiconductor light emitting element array chip, and on the printed wiring board, for example, the light emitting portions are arranged in the main scanning direction at a constant arrangement pitch. A plurality of semiconductor light emitting element array chips are mounted in a straight line.

  Such an LED print head applies semiconductor adhesive on a printed wiring board, presses a semiconductor light emitting element array chip on the adhesive, and then cures the adhesive to thereby emit semiconductor light on the printed wiring board. The element array chip is fixed.

  Here, when the interval between adjacent semiconductor light emitting element array chips is narrow, the adhesive crawls up to the surface of the semiconductor light emitting element array chip from the gap between the adjacent semiconductor light emitting element array chips and contaminates the light emitting portion. As a result, there is a risk of causing problems such as reducing the amount of light or contaminating the wire bonding pads provided on the surface edge of the semiconductor light emitting element array chip to reduce the strength of wire bonding.

  Therefore, conventionally, by restricting the application area of the adhesive so that only the central portion of the back surface of the semiconductor light-emitting element array chip is bonded to the printed wiring board, the adhesive can crawl up to the surface of the semiconductor light-emitting element array chip. A print head that has been prevented has been proposed (see, for example, Patent Document 1).

JP 2011-131475 A

  However, if only the central portion of the back surface of the semiconductor light emitting element array chip is adhered to the printed wiring board, the back surface edge of the semiconductor light emitting element array chip is lifted from the printed wiring board. When wire bonding is performed, the end of the semiconductor light emitting element array chip may be broken and damaged, or the semiconductor light emitting element array chip may be inclined with respect to the printed wiring board.

  In addition, when the back end of the semiconductor light emitting element array chip is lifted from the printed circuit board, the heat propagation near the end of the semiconductor light emitting element array chip is slower than the vicinity of the center, and the temperature near the end is lower. There was a tendency to increase.

  Thus, limiting the adhesive application area prevents contamination of the semiconductor light emitting element array chip surface due to the adhesive, while increasing the possibility of chip breakage, tilting, temperature rise, etc. There was a problem that the operational reliability of the head was lowered.

  The present invention has been made in consideration of the above points, and an object of the present invention is to propose a semiconductor device, an exposure head, and an image forming apparatus that can prevent contamination by an adhesive without deteriorating operation reliability.

  In order to solve such a problem, the present invention includes a semiconductor chip having a plurality of semiconductor elements provided on the surface thereof, and a substrate on which the plurality of semiconductor chips are mounted side by side. The surface is bonded with an adhesive, and a step portion lower than the surface on which the semiconductor element is provided is provided at an end portion of the semiconductor chip facing an adjacent semiconductor chip.

  Thus, in the present invention, since the entire back surface of the semiconductor chip can be adhered to the substrate with an adhesive, it is possible to prevent damage or inclination of the semiconductor chip, an increase in temperature, etc. Even if the adhesive crawls up from the gap due to capillary action, the adhesive flows out to a stepped portion lower than the surface where the semiconductor element is provided, and escapes to the surface where the semiconductor element is provided. Crawling up can be suppressed.

  According to the present invention, it is possible to prevent damage and inclination of the semiconductor chip, an increase in temperature, and the like, and it is possible to prevent contamination of the surface of the semiconductor chip by the adhesive, and thus without reducing the operation reliability. A semiconductor device, an exposure head, and an image forming apparatus that can prevent contamination by an adhesive can be realized.

1 is a schematic cross-sectional view illustrating an overall configuration of an LED printer according to a first embodiment. It is a basic diagram which shows the structure of the LED print head in 1st Embodiment. It is an approximate line figure showing composition (1) of COB in a 1st embodiment. It is a basic diagram which shows the structure (2) of COB in 1st Embodiment. It is a basic diagram which shows the structure of COB for a comparison (straight line mounting). It is a basic diagram which shows a mode that the adhesive agent creeps up in COB for comparison (straight line mounting). It is a basic diagram which shows a mode that the adhesive agent in 1st Embodiment flows out to a level | step difference part. It is a basic diagram which shows the space | interval from the outermost light emission part in 1st Embodiment to a chip | tip end surface. It is a basic diagram which shows the structure (1) of the modification of 1st Embodiment. It is a basic diagram which shows a mode that the adhesive agent in the modification of 1st Embodiment flows out into a level | step difference part. It is a basic diagram which shows the structure (2) of the modification of 1st Embodiment. It is a basic diagram which shows the structure (1) of COB in 2nd Embodiment. It is a basic diagram which shows the structure (2) of COB in 2nd Embodiment. It is a basic diagram which shows the structure of COB for comparison (staggered mounting). It is a basic diagram which shows a mode that the adhesive agent climbs in COB for comparison (staggered mounting). It is a basic diagram which shows a mode that the adhesive agent in 2nd Embodiment flows out into a level | step difference part. It is a basic diagram which shows the structure of COB in 3rd Embodiment. It is a basic diagram which shows the radiation angle of the light radiated | emitted from the light emission part in 3rd Embodiment.

  Hereinafter, modes for carrying out the invention (hereinafter referred to as embodiments) will be described in detail with reference to the drawings.

[1. First Embodiment]
[1-1. Overall configuration of LED printer]
FIG. 1 shows an outline of the overall configuration of the LED printer. As shown in FIG. 1, the LED printer 1 has a substantially box-shaped housing 2. In the following description, the left side when viewed from the front of the housing 2 is the left side of the housing 2, and the right side when viewed from the front of the housing 2 is the right side of the housing 2. Further, the direction from the left side to the right side of the housing 2 is the right direction, the direction from the right side to the left side of the housing 2 is the left direction, the direction from the lower side to the upper side of the housing 2 is the upward direction, and the upper side of the housing 2 The direction from the lower side to the lower side is the downward direction, the direction from the back side to the front side of the housing 2 is the front direction, and the direction from the front side to the back side of the housing 2 is the back direction.

  In the housing 2, four process units 3A to 3D are provided for forming images of each color of yellow (Y), magenta (M), cyan (C), and black (K) using an electrophotographic method. It has been. The four process units 3 </ b> A to 3 </ b> D are arranged side by side in the front-rear direction along the conveyance path 4 of the recording medium P.

  Each of the process units 3A to 3D includes a photosensitive drum 5 as an image carrier, a charging device 6 that is disposed around the photosensitive drum 5 and charges the surface of the photosensitive drum 5, and a charged photosensitive drum. 5 has an exposure device 7 that selectively irradiates the surface of light 5 to form an electrostatic latent image. The exposure device 7 is equipped with an LED print head 8 (see FIG. 2), which will be described later, as a light source. Further, each of the process units 3A to 3D forms a toner image on the surface of the photosensitive drum 5 by supplying toner to the surface of the photosensitive drum 5 on which the electrostatic latent image is formed and developing the electrostatic latent image. A developing device 9 for cleaning, and a cleaning device 10 for removing toner remaining on the surface of the photosensitive drum 5. The photosensitive drum 5 is rotated in the clockwise direction in the drawing by a driving mechanism including a driving source and gears (not shown).

  A paper cassette 11 for storing recording media P such as paper is provided in the housing 2, and the recording media P stored in the paper cassette 11 are separated one by one in the vicinity of the paper cassette 11. Thus, a hopping roller 12 is provided for conveyance. Further, in the housing 2, pinch rollers 13 and 14 and a recording medium P are sandwiched between the hopping roller 12 and the process units 3 </ b> A to 3 </ b> D in the conveyance path 4, and the recording medium is combined with the pinch rollers 13 and 14. Registration rollers 15 and 16 for correcting the skew of P and transporting them to the process units 3A to 3D are provided. The hopping roller 12 and the registration rollers 15 and 16 are rotated in conjunction with a driving source (not shown).

  Furthermore, a transfer roller 17 is provided in the housing 2 so as to be opposed to the photosensitive drum 5 with the conveyance path 4 interposed therebetween, below the photosensitive drum 5 of each of the process units 3A to 3D. The transfer roller 17 is made of semiconductive rubber or the like. In the LED printer 1, the potential of the photosensitive drum 5 and the potential of the transfer roller 17 are set so that the toner image on the photosensitive drum 5 is transferred onto the recording medium P.

  Further, a fixing device 18 is provided in the casing 2 on the downstream side of the transport path 4 from the process units 3A to 3D. Further, the recording medium P is stored in the casing on the downstream side of the transport path 4 from the fixing device 18. Discharge rollers 20, 21 and 22, 23 for discharging to a stacker 19 provided on the upper surface of the body 2 are provided.

  The LED printer 1 has such a configuration, and the recording media P stored in the paper cassette 11 are separated one by one by the hopping roller 12 and conveyed along the conveyance path 4. At this time, the recording medium P passes through the pinch rollers 13 and 14 and the registration rollers 15 and 16, and further passes through the four process units 3A to 3D in order. When the recording medium P sequentially passes through the four process units 3 </ b> A to 3 </ b> D, the toner image of each color is sequentially transferred by passing between the respective photosensitive drums 5 and the transfer roller 17. The recording medium P is heated and pressed by the fixing device 18 to fix the toner images of the respective colors, and is then discharged to the stacker 19 by the discharge rollers 20 to 23.

[1-2. Configuration of LED print head]
Next, the configuration of the LED print head 8 mounted on each exposure apparatus 7 of the process units 3A to 3D will be described. In FIG. 2, the external appearance of the LED print head 8 and its cross section are shown. As shown in FIG. 2, the LED print head 8 has a rod-shaped frame 30 having a substantially U-shaped cross section. The frame 30 is made of, for example, a resin such as aluminum, sheet metal, or liquid crystal polymer. Here, for the sake of easy understanding, the U-shaped opening side is the lower side of the frame 30 and the opposite side is the upper side.

  An opening 31 is formed along the longitudinal direction of the frame 30 on the lower side of the frame 30. Further, a hole 32 penetrating to the lower opening 31 is formed on the upper side of the frame 30 along the longitudinal direction of the frame 30. A COB (Chip On Board) 33 is incorporated in the frame 30 so as to fit into the lower opening 31. The COB 33 has a configuration in which a plurality of semiconductor light emitting element array chips 35 are arranged in a straight line along the longitudinal direction of the printed wiring board 34 on the surface of the rectangular printed wiring board 34. The COB 33 is incorporated so that the surface of the printed wiring board 34 faces the inside of the frame 30, and when incorporated, the semiconductor light emitting element array chip 35 on the surface faces the hole 32 on the upper side of the frame 30. It has become. The longitudinal direction of the COB 33 indicated by the arrow α is the main scanning direction, and the short direction of the COB 33 is the sub-scanning direction.

  Further, a rectangular parallelepiped rod lens array 36 is incorporated in the frame 30 so as to be inserted into the upper hole 32. The rod lens array 36 is for imaging the light emitted from the semiconductor light emitting element array chip 35 on the photosensitive drum 5 as an erecting equal-magnification image, and the semiconductor light emitting element array on the printed wiring board 34. One surface facing the chip 35 is separated from the semiconductor light emitting element array chip by a predetermined distance L, and the other surface side protrudes outward from the hole 32 of the frame 30. The distance L between the rod lens array 36 and the semiconductor light emitting element array chip 35 is designed and adjusted so that the rod lens array 36 is focused on the semiconductor light emitting element array chip 35.

  The LED print head 8 has such a configuration. In fact, each of the process units 3A to 3D is arranged such that the other surface of the rod lens array 33 protruding from the frame 30 faces the surface of the photosensitive drum 5. Can be attached to.

  Here, the printed wiring board 34 constituting the COB 33 and the semiconductor light emitting element array chip 35 provided on the printed wiring board 34 will be described in more detail. 3 and 4 show the external configuration of the COB 33. FIG. 3 is an enlarged view of the COB 33 and a part thereof. FIG. 4 is an enlarged view of the printed wiring board 34 and the semiconductor light-emitting element array in order to further enlarge a part of the COB 33 and simplify the explanation. The Au wire 40 that connects the chip 35 is omitted.

  As shown in FIGS. 3 and 4, on the surface of the printed wiring board 34, a plurality of rectangular plate-shaped semiconductor light emitting element array chips 35 using a conductive or insulating adhesive 41 are used for main scanning indicated by an arrow α. It is mounted in a straight line along the direction. On the surface 42 of each semiconductor light emitting element array chip 35, for example, a plurality of light emitting portions 43 made of light emitting diodes mainly composed of a GaAs compound semiconductor are, for example, 600 dpi (about 42.3 um pitch) or 1200 dpi (about 21.2 um pitch). ) Is arranged in a one-dimensional array at an arrangement pitch D1. The light emitting portion 43 can have an LED structure formed by pn junction of a P-type semiconductor and an N-type semiconductor, or a thyristor structure formed by PNPN junction or NPNP junction.

  The light emitting unit 43 is arranged along the main scanning direction near one end of both ends of the surface 42 of the semiconductor light emitting element array chip 35 in the sub scanning direction (short direction) perpendicular to the main scanning direction (longitudinal direction). A plurality of wire bonding pads 44 are formed at predetermined intervals along the main scanning direction near the other end opposite to the one end.

  The semiconductor light emitting element array chip 35 can be composed of a GaSa substrate, like the light emitting unit 43, and besides the light emitting unit 43, a shift register (not shown) or the like that sequentially shifts signals from an external drive circuit. It can also have functionality. Further, the semiconductor light emitting element array chip 35 may be an IC drive circuit substrate made of Si for controlling the light emitting unit 43. In this case, for example, a light emitting layer grown on a GaSa substrate made of a compound semiconductor is thinned to, for example, 5 μm or less, and then integrated on an IC drive circuit substrate using intermolecular force bonding. Thereafter, the light-emitting portion 43 is formed using thin film wiring that can be formed by the combined use of lithography technology and thin-film metal film formation technology, and at the same time, the IC drive circuit and the light-emitting portion 43 are electrically connected to each other on the GaSa substrate. What is necessary is just to integrate. The thickness of the semiconductor light emitting element array chip 35 can be set to 200 μm to 600 μm, for example.

  Further, in the present embodiment, as shown in FIG. 4, the semiconductor light emitting element array chip is provided at both ends in the main scanning direction of the semiconductor light emitting element array chip 35, that is, at both ends facing the adjacent semiconductor light emitting element array chip 35. A terrace-shaped stepped portion 46 having a stepped surface 45 lower than the surface 42 of 35 is formed.

  More specifically, an outermost light emitting portion 43 is formed at one end of the semiconductor light emitting element array chip 35 in the main scanning direction. In order to distinguish the outermost light emitting unit 43 from the other light emitting units 43, the outermost light emitting unit 43x is hereinafter referred to as the outermost light emitting unit 43x. Therefore, a region around the outermost light emitting portion 43x is left as it is at one end, and the one end side and the other end side in the sub-scanning direction of the outermost light emitting portion 43x are each one step lower than the surface. A terrace-shaped stepped portion 46 having a stepped surface 45 is formed. That is, the stepped portion 46 is formed so as to avoid the formation region of the outermost light emitting portion 43x. A similar stepped portion 46 is formed at the other end portion of the semiconductor light emitting element array chip 35 in the main scanning direction. Note that the stepped portion 46 is formed, for example, over 20 μm or more inward from both ends in the main scanning direction of the semiconductor light emitting element array chip 35, and is formed by dug down, for example, 20 μm to 200 μm from the surface of the semiconductor light emitting element array chip 35. ing.

  As a method for forming such a stepped portion 46, when the semiconductor light emitting element array chip 35 is composed of a GaAs substrate, first, the stepped portion on the surface 42 of the rectangular plate-shaped semiconductor light emitting element array chip 35 cut out from the wafer. A region outside the region 46 is protected with a photoresist or the like. Next, the GaSa substrate is exposed by removing the passivation film or the interlayer insulating film in the region to be the stepped portion 46 using CF4 dry etching or the like. Then, the exposed GaSa substrate is etched by, for example, 20 μm to 200 μm by chemical dry etching using a chlorine-based gas or the like, or wet etching using an etchant made of a mixed solution of sulfuric acid, hydrogen peroxide solution, and water. By doing so, a stepped portion 46 is formed in the semiconductor light emitting element array chip 35. Finally, the photoresist protecting the surface 42 of the semiconductor light emitting element array chip 35 is removed.

  On the other hand, when the semiconductor light emitting element array chip 35 is constituted by an IC drive circuit substrate made of Si, it is designed so that a circuit is not formed in a region to be the stepped portion 46 of the semiconductor light emitting element array chip 35. In addition, as in the case where the semiconductor light emitting element array chip 35 is composed of a GaSa substrate, the outside of the region that becomes the stepped portion 46 of the surface 42 of the semiconductor light emitting element array chip 35 is protected with a photoresist or the like, and CF4 dry The Si substrate is exposed by removing the passivation film or the interlayer insulating film in the region to be the stepped portion 46 using etching or the like. Then, the exposed Si substrate is etched by 20 μm to 200 μm by chemical dry etching using a gas such as SF 6. By doing so, a stepped portion 46 is formed in the semiconductor light emitting element array chip 35. Finally, the photoresist protecting the surface 42 of the semiconductor light emitting element array chip 35 is removed.

  The semiconductor light emitting element array chip 35 in which the stepped portion 46 is formed in this way is formed on the printed wiring board 34 made of, for example, CEM3 (Composite epoxy material 3) or FR4 (Flame retardant 4) via an adhesive 41. Mounted in a straight line along the main scanning direction. At that time, the semiconductor light emitting element array chip is arranged such that the interval D2 between the outermost light emitting parts 43x of the adjacent semiconductor light emitting element array chips 35 is equal to the arrangement pitch D1 of the light emitting parts 43 on the semiconductor light emitting element array chip 35. 35 is mounted on the printed circuit board 34. For this reason, when the arrangement pitch D1 of the light emitting units 43 is 600 dpi (about 42.3 um pitch), the interval D3 between the adjacent semiconductor light emitting element array chips 35 is, for example, about 10 um, which is narrower than the arrangement pitch D1 at this time. When the arrangement pitch D1 of the portions 43 is 1200 dpi (about 21.2 um pitch), the interval D3 between the adjacent semiconductor light emitting element array chips 35 is, for example, about 5 um, which is narrower than the arrangement pitch D1 at this time.

  Further, the adhesive 41 can be transferred and formed on the printed wiring board 34 by using a stamp function provided in a die bonding apparatus (not shown), and the printed wiring board 34 is preliminarily formed by a dispenser apparatus (not shown). It can also be formed on top. At this time, the adhesive 41 is formed in contact with the entire back surface of the semiconductor light emitting element array chip 35. The semiconductor light emitting element array chip 35 is pressed onto the adhesive 41 formed (coated) on the printed wiring board 34 in this way, and then the adhesive 41 is cured, so that the entire back surface is printed on the printed wiring board. It is fixed by adhering to 34.

  Further, as described above, the wire bonding pads 44 for data input / output with the external drive circuit are formed on each semiconductor light emitting element array chip 35, while each semiconductor light emitting is formed on the printed wiring board 34. Wire bonding pads 47 for inputting / outputting data to / from the element array chip 35 are formed in pairs with the wire bonding pads 44 on each semiconductor light emitting element array chip 35. The wire bonding pads 47 on the printed wiring board 34 are formed at predetermined intervals in the sub-scanning direction with the wire bonding pads 44 on the semiconductor light emitting element array chips 35.

  As shown in FIG. 3, wire bonding pads 44 on each semiconductor light emitting element array chip 35 and wire bonding pads 47 on the printed wiring board 34 are connected using Au wires 40. The Further, a ROM (not shown) for writing data, a chip capacitor (not shown), a connector for data input / output (not shown) with the LED printer 1 side, etc. are mounted on the printed wiring board 34. Thus, the COB 33 for the LED print head 8 is configured. The COB 33 is incorporated into the frame 30 of the LED print head 8 as described above.

[1-3. Effects of the first embodiment]
Here, an effect obtained by forming the stepped portion 46 in the semiconductor light emitting element array chip 35 will be described. Here, the effects of the present embodiment will be described using a COB having a semiconductor light emitting element array chip without the stepped portion 46 as a comparison target.

  First, FIG. 5 shows a comparative COB 52 in which a semiconductor light emitting element array chip 50 without a step 46 is mounted on a printed wiring board 51. The comparison COB 52 has the same configuration as the COB 33 of the first embodiment except that the step portion 46 is not formed in the semiconductor light emitting element array chip 50.

  Briefly, the comparative COB 52 has a plurality of semiconductor light emitting element array chips 50 mounted in a straight line on the surface of the printed wiring board 51 using an adhesive 53. At that time, the semiconductor light emitting element array chip is arranged such that the interval D2 between the outermost light emitting parts 54x of the adjacent semiconductor light emitting element array chips 50 is equal to the arrangement pitch D1 of the light emitting parts 54 on the semiconductor light emitting element array chip 50. 50 is mounted on the printed circuit board 51. For this reason, when the arrangement pitch D1 of the light emitting portions 54 is 600 dpi (about 42.3 um pitch), the interval D3 between adjacent semiconductor light emitting element array chips 50 is, for example, about 10 um, and the arrangement pitch D1 of the light emitting portions is 1200 dpi (about 1200 dpi). 21.2 um pitch), the distance D3 between adjacent semiconductor light emitting element array chips 50 is, for example, about 5 um.

  Further, a plurality of wire bonding pads 55 and 56 are respectively formed on the semiconductor light emitting element array chip 50 and the printed wiring board 51, and the wire bonding pads 55 of the semiconductor light emitting element array chip 50 and the wires of the printed wiring board 51 are formed. A bonding pad 56 is connected by an Au wire 57.

  In the case of such a comparative COB 52, as shown in FIG. 6, the adhesive 53 crawls up to the surface of the semiconductor light-emitting element array chip 50 from the gap between the adjacent semiconductor light-emitting element array chips 50 by the capillary phenomenon. There arises a problem that the amount of light is reduced by contaminating 54, or the strength of wire bonding is reduced by contaminating the wire bonding pad 55.

  On the other hand, in the case of the COB 33 of the present embodiment, the interval between the semiconductor light emitting element array chips 35 is the same as that of the conventional COB 52 and the adhesive 41 is in contact with the entire back surface of the semiconductor light emitting element array chip 35. However, as shown in FIG. 7, a stepped portion 46 that is one step lower than the surface 42 of the semiconductor light emitting element array chip 35 is removed from the surface 41 of the semiconductor light emitting element array chip 35 with the adhesive 41 that crawls up through the gap between adjacent semiconductor light emitting element array chips 35. It is possible to prevent scooping up to the surface 42 by allowing the air to escape to the step surface 45 of the surface.

  Further, according to the COB 33 of the present embodiment, the entire back surface of the semiconductor light emitting element array chip 35 is bonded to the printed wiring board 34 without limiting the formation region of the adhesive 41 in contact with the back surface of the semiconductor light emitting element array chip 35. Therefore, it is possible to avoid a situation in which the end portion of the semiconductor light emitting element array chip 35 is lifted from the printed wiring board 34. Thereby, for example, when wire bonding is performed on the wire bonding pad 44, the end of the semiconductor light emitting element array chip 35 is broken or damaged, or the semiconductor light emitting element array chip 35 is damaged with respect to the printed wiring board 34. Inclination can be prevented.

  Furthermore, according to the COB 33 of the present embodiment, since the entire back surface of the semiconductor light emitting element array chip 35 is bonded to the printed wiring board 34 via the adhesive 41, the heat generated from the semiconductor light emitting element array chip 35 is Heat can be uniformly transmitted to the printed wiring board 34 through the entire back surface. That is, the heat dissipation of the semiconductor light emitting element array chip 35 can be ensured uniformly over the entire chip.

  Further, according to the COB 33 of the present embodiment, for example, even if the interval D3 between the adjacent semiconductor light emitting element array chips 35 is narrower than the comparison COB 52, the gap between adjacent semiconductor light emitting element array chips 35 (that is, the interval D3). ) Can be released to the stepped portion 46. Therefore, as shown in FIG. 8, the main scanning of the semiconductor light emitting element array chip 35 is started from the outermost light emitting portion 43x on the semiconductor light emitting element array chip 35 by the distance D3 between the adjacent semiconductor light emitting element array chips 35 being narrowed. Since the distance D4 to the end face in the direction (that is, the facing face) can be made wider than the comparative COB 52, a margin can be given to the end design of the semiconductor light emitting element array chip 35.

  As described so far, according to the COB 33 of the present embodiment, in the structure in which the semiconductor light emitting element array chip 35 is arranged in a line using the adhesive 41 on the printed wiring board 34, the semiconductor light emitting element array chip is mounted. Since the entire back surface of 35 can be adhered to the printed wiring board 34 by the adhesive 41, it is possible to prevent chip breakage, inclination, temperature rise, etc., and in addition, between adjacent semiconductor light emitting element array chips 35 Even if the adhesive 41 crawls up from the gap due to capillary action, the adhesive 41 is allowed to escape by flowing out to the stepped portion 46 that is one step lower than the surface 42 on which the light emitting portion 43 is provided. Can be prevented from climbing up to the surface 42 on which is provided.

  As described above, according to the COB 33 of the present embodiment, it is possible to prevent the semiconductor light emitting element array chip 35 from being damaged, tilted, and heated, and the surface 42 of the semiconductor light emitting element array chip 35 by the adhesive 41. Thus, contamination by the adhesive 41 can be prevented without deteriorating the operational reliability of the chip.

  In addition, according to the COB 33 of the present embodiment, even if the distance D3 between the adjacent semiconductor light emitting element array chips 35 is narrower than the conventional one, the adhesive 41 to the surface 42 of the semiconductor light emitting element array chip 35 can be applied. Since the creeping up can be sufficiently suppressed, the distance D3 between the adjacent semiconductor light emitting element array chips 35 is reduced, so that the outermost light emitting portion 43x on the semiconductor light emitting element array chip 35 and the semiconductor light emitting element array chip 35 in the main scanning direction are reduced. The distance D4 from the end face can be increased. Thereby, a margin can be given to the end design of the semiconductor light emitting element array chip 35.

[1-4. Modification of First Embodiment]
Here, FIG. 9 shows a modification of the first embodiment. In this modification, the formation position and the formation method of the stepped portion 46 are the same as those in the first embodiment described above, but the protruding corner (that is, the protruding corner) of the stepped portion 46 has an R shape.

  Specifically, on one end side of the semiconductor light emitting element array chip 35 in the main scanning direction, the two corners 60 and 61 located at the tip of the region around the outermost light emitting portion 43x that remains without being etched are formed in an R shape. The two corners 60 and 61 are similarly formed in an R shape on the other end side.

  By doing so, the area of the end surface in the main scanning direction of the semiconductor light emitting element array chip 35, that is, the area of the facing surface facing the adjacent semiconductor light emitting element array chip 35 can be reduced. As a result, the adhesive 41 that tends to scoop up between the opposing surfaces of the adjacent semiconductor light emitting element array chips 35 can easily flow out to the step surface 45.

  Further, on one end side of the semiconductor light emitting element array chip 35 in the main scanning direction, among the wall surfaces connecting the surface 42 and the step surface 45 of the semiconductor light emitting element array chip 35, a wall surface parallel to the sub scanning direction and the semiconductor light emitting element array Two corners 62 and 63 formed by the sub-scanning direction of the chip 35 and the end face perpendicular to each other are formed in an R shape. Similarly, the two corners 62 and 63 have an R shape on the other end side.

  Actually, when the semiconductor light emitting element array chips 35 are arranged in a straight line and mounted, the step portions 46 of the adjacent semiconductor light emitting element array chips 35 face each other. At this time, as shown in FIG. 10, the adhesive 41 scooping up to the step surface 45 flows to both ends in the sub-scanning direction along the wall surface of the step portion 46, and finally, the step surface 45. It flows out to the printed wiring board 34 side that is one step lower. That is, both ends of the stepped portion 46 in the sub-scanning direction are outlets for the adhesive 41.

  Therefore, in this modified example, the two corners 62 and 63 located in the vicinity of the exit of the stepped portion 46 are formed in an R shape so that the exit of the stepped portion 46 can be widened, and the adhesion that has risen up to the stepped surface 45 is obtained. The agent 41 can be easily flown out to the outlet of the stepped portion 46 and from the outlet to the outside. That is, according to this modification, it is possible to suppress creeping of the adhesive 41 onto the surface 42 of the semiconductor light emitting element array chip 35, as compared with the first embodiment described above. In this modification, the four corners 60 to 63 of the stepped portion 46 are R-shaped, but the remaining corners may be R-shaped.

  In the first embodiment described above, the stepped portion 46 is provided on each of the one end side and the other end side in the sub-scanning direction of the outermost light-emitting portion 43x. You may make it provide the level | step-difference part 46 only in the wide one end side among the one end side and the other end side of a direction.

  Furthermore, in the first embodiment described above, the angle of the wall surface connecting the surface 42 of the semiconductor light emitting element array chip 35 and the stepped surface 45 of the stepped portion 46 is not particularly mentioned. For example, FIG. ), The angle of the wall surface 65 may be perpendicular to the step surface 45, or may be an acute angle with respect to the step surface 45 as shown in FIG. By making an acute angle with respect to the stepped surface 45, it is possible to more reliably prevent the adhesive 41 from creeping up to the surface of the semiconductor light emitting element array chip.

[2. Second Embodiment]
Next, a second embodiment will be described. In the second embodiment, the mounting form of the semiconductor light emitting element array chip is different from that of the first embodiment. The outline of the overall configuration of the LED printer 1 and the basic configuration of the LED print head 8 are described. Since is the same as in the first embodiment, description thereof is omitted. Therefore, COB will be described in detail here.

[2-1. Configuration of COB]
12 and 13 show the external configuration of the COB 100 according to the second embodiment. 12 is an enlarged view of the COB 100 and a part thereof. FIG. 13 is an enlarged view of the printed wiring board 101 and the semiconductor light emitting device for further enlarging a part of the COB 100 and simplifying the explanation. The Au wire 103 for connecting to the array chip 102 is omitted.

  As shown in FIGS. 12 and 13, on the surface of the printed circuit board 101, a plurality of rectangular plate-shaped semiconductor light-emitting element array chips 102 using a conductive or insulating adhesive 104 are main-scanned indicated by an arrow α. It is mounted in a staggered pattern along the direction. At this time, the two adjacent semiconductor light emitting element array chips 102 are mounted such that end faces parallel to the main scanning direction are opposed to each other in the sub scanning direction.

  Each semiconductor light emitting element array chip 102 can be a GaSa substrate or an IC drive circuit substrate, as in the first embodiment. Further, the thickness of the semiconductor light emitting element array chip 102 can be set to 200 μm to 600 μm, for example. On the surface 105 of each semiconductor light emitting element array chip 102, for example, a plurality of light emitting portions 106 made of light emitting diodes mainly composed of a GaAs compound semiconductor are, for example, 600 dpi (about 42.3 um pitch) or 1200 dpi (about 21.2 um pitch). ) Is arranged in a one-dimensional array at an arrangement pitch D1.

  The light emitting units 106 are arranged along the main scanning direction on the surface 105 of the semiconductor light emitting element array chip 102 near the facing surface parallel to the main scanning direction facing the adjacent semiconductor light emitting element array chip 102. Further, the semiconductor light emitting element array chip 102 has extended portions 107 that are extended from, for example, 100 μm to 500 μm in the main scanning direction from the position of the outermost light emitting portion 106 x on both ends in the main scanning direction. A plurality of (for example, two) wire bonding pads 108 are provided at predetermined intervals along the main scanning direction near the opposite surfaces (referred to as non-opposing surfaces) of the extending portions 107 at both ends. Are formed with a gap. As described above, the wire bonding pad 108 is formed in the extended portion 107 extended in the main scanning direction, so that the length of the semiconductor light emitting element array chip 102 in the sub-scanning direction can be shortened. In addition, the number of chips that can be cut out from one wafer can be increased.

  Further, as shown in FIG. 13, the extended portions 107 at both ends have a rectangular step surface 109 that is one step lower than the surface 105 at the end portion on the facing surface facing the adjacent semiconductor light emitting element array chip 102. A terrace-shaped stepped portion 110 is formed.

  More specifically, the step 110 is formed at the end of the extending portion 107 on the one end side of the semiconductor light emitting element array chip 102 on the opposite surface side, from the vicinity of the outermost light emitting portion 106x in the main scanning direction to the end of the extending portion 107. In the sub-scanning direction, it is formed over 20 μm or more inward from the facing surface of the extended portion 107, and in the depth direction, for example, 20 μm to 200 μm is dug down from the surface 105 of the semiconductor light emitting element array chip 102. ing. A similar stepped portion 110 is also formed in the extended portion 107 on the other end side of the semiconductor light emitting element array chip 102.

  As a method of forming such a stepped portion 110, when the semiconductor light emitting element array chip 102 is formed of a GaAs substrate, first, the stepped portion of the surface 105 of the rectangular plate-shaped semiconductor light emitting element array chip 102 cut out from the wafer is used. The outside of the region to be 110 is protected with a photoresist or the like. Next, the GaSa substrate is exposed by removing the passivation film or the interlayer insulating film in the region to be the stepped portion 110 using CF4 dry etching or the like. Then, the exposed GaSa substrate is etched by, for example, 20 μm to 200 μm by chemical dry etching using a chlorine-based gas or the like, or wet etching using an etchant made of a mixed solution of sulfuric acid, hydrogen peroxide solution, and water. By doing so, a stepped portion 110 is formed in the semiconductor light emitting element array chip 102. Finally, the photoresist protecting the surface 105 of the semiconductor light emitting element array chip 102 is removed.

  On the other hand, when the semiconductor light emitting element array chip 102 is constituted by an IC drive circuit substrate made of Si, it is designed so that no circuit is formed in a region to be the stepped portion 110 of the semiconductor light emitting element array chip 102. In addition, as in the case where the semiconductor light emitting element array chip 102 is made of a GaSa substrate, the outside of the region that becomes the stepped portion 110 of the surface 105 of the semiconductor light emitting element array chip 102 is protected with a photoresist or the like, and CF4 dry The Si substrate is exposed by removing the passivation film or the interlayer insulating film in the region to be the stepped portion 110 using etching or the like. Then, the exposed Si substrate is etched by 20 μm to 200 μm by chemical dry etching using a gas such as SF 6. By doing so, a stepped portion 110 is formed in the semiconductor light emitting element array chip 102. Finally, the photoresist protecting the surface 105 of the semiconductor light emitting element array chip 102 is removed.

  Furthermore, as shown in FIG. 13, the protruding corner of the stepped portion 110 may be an R shape. Specifically, on one end side of the semiconductor light emitting element array chip 102 in the main scanning direction, among the wall surfaces connecting the surface 105 and the step surface 109 of the semiconductor light emitting element array chip 102, the wall surface parallel to the main scanning direction and the semiconductor light emission. The corner 111 formed by the main scanning direction of the element array chip 102 and the end face perpendicular to the main scanning direction has an R shape, a wall surface parallel to the sub scanning direction, and a facing surface orthogonal to the sub scanning direction of the semiconductor light emitting element array chip 102 The corner 112 formed by the above is an R shape. Similarly, the two corners 111 and 112 have an R shape on the other end side.

  The semiconductor light emitting element array chips 102 in which the step portions 110 are formed in this way are mounted on the printed wiring board 101 in a staggered manner along the main scanning direction via the adhesive 104. In this case, the semiconductor light emitting element array chip 102 is adjacent in the sub-scanning direction. At this time, the semiconductors are arranged such that the distance D2 in the main scanning direction between the outermost light emitting portions 106x of the adjacent semiconductor light emitting element array chips 102 is equal to the arrangement pitch D1 of the light emitting portions 106 on the semiconductor light emitting element array chip 102. The light emitting element array chip 102 is mounted on the printed wiring board 101.

  In addition, it is desirable to mount the semiconductor light emitting element array chip 102 on the printed wiring board 101 so that the distance D5 in the sub-scanning direction of the light emitting portions 106 of the adjacent semiconductor light emitting element array chips 102 is as small as possible. This is because the positional relationship in the sub-scanning direction between the respective light emitting portions 106 of the semiconductor light emitting element array chips 102 mounted in a staggered manner and the rod lens array 36 is made as close as possible, thereby the light emitting portions of the semiconductor light emitting element array chip 102. This is to reduce the difference in light transmission efficiency in the rod lens array 36 between 106 as much as possible, and as a result, to reduce the light amount difference between the semiconductor light emitting element array chips 102 as much as possible.

  The adhesive 104 is formed so as to be in contact with the entire back surface of the semiconductor light emitting element array chip 102. The semiconductor light emitting element array chip 102 is pressed onto the adhesive 104 formed (coated) on the printed wiring board 101 in this way, and then the adhesive 104 is cured, so that the entire back surface is printed on the printed wiring board 101. It is fixed by adhering.

  Further, as described above, the wire bonding pads 108 for data input / output with the external drive circuit are formed on each semiconductor light emitting element array chip 102, while each semiconductor light emitting is formed on the printed wiring board 101. Wire bonding pads 113 for data input / output to the element array chip 102 are formed in pairs with the wire bonding pads 108 on each semiconductor light emitting element array chip 102. The wire bonding pads 113 on the printed wiring board 101 are formed at predetermined intervals in the sub-scanning direction from the wire bonding pads 108 on each semiconductor light emitting element array chip 102.

  Then, wire bonding pads 108 on each semiconductor light emitting element array chip 102 and wire bonding pads 113 on the printed circuit board 101 are connected using Au wires 103 (FIG. 12). Furthermore, a ROM (not shown) for writing data, a chip capacitor (not shown), a connector for data input / output (not shown) with the LED printer 1 side, and the like are mounted on the printed wiring board 101. Thus, the COB 100 for the LED print head 8 is configured. The COB 100 is incorporated in the frame 30 of the LED print head 8 as in the first embodiment.

[2-2. Effects of the second embodiment]
Here, the effect by forming the step part 110 in the semiconductor light emitting element array chip 102 mounted in a staggered manner will be described. Here, the effects of the present embodiment will be described using a COB having a semiconductor light emitting element array chip without the stepped portion 110 as a comparison target.

  First, FIG. 14 shows a comparative COB 122 in which the semiconductor light emitting element array chip 120 without the stepped portion 110 is mounted on the printed wiring board 121 in a staggered manner. The comparison COB 122 has the same configuration as the COB 100 of the second embodiment described above except that the step portion 110 is not formed on the semiconductor light emitting element array chip 120.

  Briefly, the comparative COB 122 has a plurality of semiconductor light emitting element array chips 120 mounted in a staggered manner on the surface of the printed wiring board 121 using an adhesive 123. At this time, the semiconductors are arranged such that the distance D2 in the main scanning direction between the outermost light emitting parts 124x of the adjacent semiconductor light emitting element array chips 120 is equal to the arrangement pitch D1 of the light emitting parts 124 on the semiconductor light emitting element array chip 120. The light emitting element array chip 120 is mounted on the printed wiring board 121.

  At this time, the semiconductor light emitting element array chip 120 may be mounted on the printed wiring board 121 so that the distance D5 in the sub-scanning direction of each light emitting portion 124 of the adjacent semiconductor light emitting element array chip 120 is as small as possible. desirable. For this reason, it is desirable that the distance D6 between adjacent semiconductor light emitting element array chips 120 is also as narrow as possible. In fact, the comparison COB 122 has an interval D6 between adjacent semiconductor light emitting element array chips 120 of, for example, between 10 μm and 50 μm. Designed to be

  Further, a plurality of wire bonding pads 126 and 127 are formed on the extended portion 125 of the semiconductor light emitting element array chip 120 and the printed wiring board 121, respectively. A wire bonding pad 127 of the substrate 121 is connected by an Au wire 128.

  In the case of such a comparative COB 122, as shown in FIG. 15, the adhesive 123 crawls up to the surface of the semiconductor light emitting element array chip 120 from the gap between the adjacent semiconductor light emitting element array chips 120 by the capillary phenomenon, and the light emitting portion The problem arises that the amount of light is reduced by contaminating 124, or the strength of wire bonding is reduced by contaminating the wire bonding pad 126.

  On the other hand, in the COB 100 of the present embodiment, the interval D6 of the semiconductor light emitting element array chip 102 is the same as that of the conventional COB 122, and the adhesive 104 is in contact with the entire back surface of the semiconductor light emitting element array chip 102. Although having the structure, as shown in FIG. 16, the stepped portion lower than the surface 105 of the semiconductor light emitting element array chip 102 by the adhesive 104 that crawls up through the gap between the adjacent semiconductor light emitting element array chips 102 by the capillary phenomenon. It is possible to prevent scooping up to the surface 105 by escaping to the stepped surface 109 of 110.

  As described above, according to the COB 100 of the present embodiment, the entire back surface of the semiconductor light emitting element array chip 102 is printed without limiting the formation region of the adhesive 104 in contact with the back surface of the semiconductor light emitting element array chip 102. Since it can be bonded and fixed to the substrate 101, it is possible to avoid a situation in which the end of the semiconductor light emitting element array chip 102 is lifted from the printed wiring board 101. Accordingly, for example, when wire bonding is performed on the wire bonding pad 108, the end portion of the semiconductor light emitting element array chip 102 is broken or damaged, or the semiconductor light emitting element array chip 102 is damaged with respect to the printed wiring board 101. Inclination can be prevented.

  Furthermore, according to the COB 100 of the present embodiment, since the entire back surface of the semiconductor light emitting element array chip 102 is bonded to the printed wiring board 101 via the adhesive 104, the heat generated from the semiconductor light emitting element array chip 102 is Heat can be uniformly propagated to the printed wiring board 101 through the entire back surface. That is, the heat dissipation of the semiconductor light emitting element array chip 102 can be ensured uniformly over the entire chip.

  Furthermore, according to the COB 100 of the present embodiment, for example, even if the interval D6 between the adjacent semiconductor light emitting element array chips 102 is narrower than that of the comparative COB 122, the COB 100 is scooped from the gap between the adjacent semiconductor light emitting element array chips 102. The rising adhesive 104 can be released to the stepped portion 110. For this reason, the distance D6 between the light emitting portion 106 on the semiconductor light emitting element array chip 102 and the facing surface of the semiconductor light emitting element array chip 102 is reduced by the distance D6 between the adjacent semiconductor light emitting element array chips 102 (see FIG. 16). Can be made wider than that of the conventional COB 100, so that a margin can be given to the end design of the semiconductor light emitting element array chip 102.

  Furthermore, according to the COB 100 of the present embodiment, the corner 112 formed by the wall surface of the stepped portion 110 parallel to the sub-scanning direction and the end surface (opposing surface) orthogonal to the sub-scanning direction of the semiconductor light emitting element array chip 102. By adopting an R shape, the area of the facing surface facing the adjacent semiconductor light emitting element array chip 102 can be reduced, and the adhesive 104 can be further suppressed from rising up to the surface 105. Thus, the adhesive 104 that tends to scoop up between the opposing surfaces of the adjacent semiconductor light emitting element array chips 102 can easily flow out to the step surface 109.

  Further, the corner 111 formed by the wall surface of the stepped portion 110 parallel to the main scanning direction and the end surface perpendicular to the main scanning direction of the semiconductor light emitting element array chip 102 is formed into an R shape. In fact, when the semiconductor light emitting element array chips 102 are arranged side by side in a zigzag manner, the extending portions 107 of the adjacent semiconductor light emitting element array chips 102 are also arranged in a staggered manner. At this time, the stepped portion 110 of each extending portion 107 is opposed to the portion inside the extending portion 107 of the adjacent semiconductor light emitting element array chip 102 (that is, the portion where the light emitting portion 106 is provided) in the sub-scanning direction. become. The adhesive 104 scooping up to the step surface 109 flows along the wall surface of the step portion 110 to the end in the main scanning direction, and finally to the printed wiring board 101 side that is one step lower than the step surface 109. It will flow out. That is, the end of the stepped portion 110 in the main scanning direction is an outlet of the adhesive 104, respectively. Therefore, by making the corner 111 located in the vicinity of the exit of the stepped portion 110 into an R shape, the exit of the stepped portion 110 can be widened, and the adhesive 104 scooped up to the stepped surface 109 is removed from the exit of the stepped portion 110. And from this outlet to the outside.

  As described so far, according to the second embodiment, even in the structure in which the semiconductor light emitting element array chips 102 are mounted on the printed wiring board 101 in a zigzag manner using the adhesive 104, the first embodiment is implemented. The same effect as that of the embodiment can be obtained. That is, contamination by the adhesive can be prevented without deteriorating the operation reliability, and in addition, a margin can be given to the end design of the semiconductor light emitting element array chip 102.

[3. Third Embodiment]
Next, a third embodiment will be described. The third embodiment is an embodiment in which a step portion is added to the semiconductor light emitting element array chip 102 of the second embodiment. The outline of the overall configuration of the LED printer 1 and the LED print head 8 are described. Since the basic configuration is the same as that of the first and second embodiments, the description thereof is omitted. Therefore, COB will be described in detail here.

[3-1. Configuration of COB]
In FIG. 17, the external appearance and cross section of COB200 of 3rd Embodiment are shown. As shown in FIG. 17, a plurality of rectangular plate-shaped semiconductor light emitting element array chips 203 are formed on the surface of a printed wiring board 201 using a conductive or insulating adhesive 202 as in the second embodiment. They are mounted side by side in a staggered manner along the main scanning direction indicated by arrow α. At this time, the adjacent semiconductor light emitting element array chips 203 are mounted such that end faces parallel to the main scanning direction are opposed to each other in the sub scanning direction.

  Each semiconductor light emitting element array chip 203 can be a GaSa substrate or an IC drive circuit substrate, as in the second embodiment. Further, the thickness of the semiconductor light emitting element array chip 203 can be set to 200 μm to 600 μm, for example. On the surface 204 of each semiconductor light emitting element array chip 203, as in the second embodiment, a plurality of light emitting portions 205 are arranged at an arrangement pitch of, for example, 600 dpi (about 42.3 um pitch) or 1200 dpi (about 21.2 um pitch). Are arranged in a one-dimensional array.

  The light emitting units 205 are arranged along the main scanning direction on the surface 204 of the semiconductor light emitting element array chip 203 near the facing surface parallel to the main scanning direction facing the adjacent semiconductor light emitting element array chip 203. Further, the semiconductor light emitting element array chip 203 is extended at both ends in the main scanning direction, for example, from the position of the outermost light emitting portion 205x to the main scanning direction, for example, from 100 μm to 500 μm, as in the second embodiment. have. In the extended portions 206 at both ends of the semiconductor light emitting element array chip 203, a rectangular shape that is one step lower than the surface is formed at the end on the opposite side facing the adjacent semiconductor light emitting element array chip 203, as in the second embodiment. A terrace-shaped stepped portion 208 having a stepped surface 207 is formed.

  In addition, in the third embodiment, a terrace-shaped stepped portion having a rectangular stepped surface 209 that is one step lower than the surface 204 on the non-facing surface side opposite to the facing surface of the extended portions 206 at both ends. 210 is formed. The stepped portion 210 is formed from the non-facing surface of the extended portion 206 to almost the center in the sub-scanning direction, and is formed, for example, by digging 20 μm to 200 μm from the surface 204 of the semiconductor light emitting element array chip 203. That is, the extended portion 206 is formed with step portions 208 and 210 at both ends in the sub-scanning direction, respectively, and these two step portions 208 and 210 are divided in the sub-scanning direction by the wall portion 211 positioned therebetween. Has been.

  An inorganic or organic insulating film 212 is formed on the stepped surface 209 of the stepped portion 210 on the non-facing surface side, and a plurality of (for example, two) wire bonding pads 213 are formed on the insulating film 212 in the main scanning direction. Are formed at predetermined intervals along the line. The wire bonding pad 213 is formed so as to be lower than the surface 204 of the extended portion 206 (ie, the upper surface of the wall portion).

  Such stepped portions 208 and 210 can be formed by the same method as in the first and second embodiments, that is, by digging down by etching. Further, the step portions 208 and 210 can be simultaneously formed on the extended portion 206 of the semiconductor light emitting element array chip 203. When the step portions 208 and 210 are formed on both ends of the extended portion 206 in the sub-scanning direction, the portions left unetched between the two step portions 208 and 210 become the wall portions 211. .

  Here, the wire bonding pad 213 formed on the step portion 210 needs to be electrically connected to the light emitting portion 205. For this reason, the wall surface connecting the step surface 209 of the step portion 210 and the surface 204 of the semiconductor light emitting element array chip 203 has, for example, a slope shape inclined from the surface 204 to the step surface 209. A thin film wiring is formed on the slope-shaped wall surface, and the light emitting portion 205 and the wire bonding pad 213 are electrically connected by the thin film wiring. Incidentally, the slope-shaped wall surface can be formed of, for example, an organic insulating film that can be formed by photolithography. Alternatively, when the semiconductor light emitting element array chip 203 is composed of a GaSa substrate, when forming the stepped portion 210, the etching end face (that is, the wall surface) is sloped by adjusting the etching rate in the vertical and horizontal directions by wet etching. It can also be a shape. Further, when the semiconductor light emitting element array chip 203 is composed of a Si substrate, the etching end face (wall surface) can be formed into a slope shape by adjusting the etching rate in the vertical direction and the horizontal direction by dry etching.

  Further, as with the second embodiment, the protruding corner of the stepped portion 208 on the facing surface side may be an R shape. Further, the step portion 210 on the non-facing surface side is formed at the corner formed by the wall surface parallel to the main scanning direction of the step portion 210 on the non-facing surface side and the end surface perpendicular to the main scanning direction of the semiconductor light emitting element array chip 203. A hood 214 for preventing the adhesive 202 from entering the step surface 209 may be formed. In this way, the adhesive 202 that has flowed out onto the printed wiring board 201 from the stepped surface 207 on the facing surface side wraps around the stepped portion 210 on the non-facing surface side and crawls up to the stepped surface 209. It is possible to prevent the wire bonding pad 213 from being contaminated by the adhesive 202.

  The semiconductor light emitting element array chips 203 in which the step portions 208 and 210 are formed in this way are mounted on the printed wiring board 201 in a zigzag manner along the main scanning direction via the adhesive 202. At this time, each of the step portions 208 and 210 is opposed to the light emitting portion 205 located inside the extending portion 206 of the adjacent semiconductor light emitting element array chip in the sub-scanning direction.

  Further, when mounted in this way, the semiconductor light emitting element array chip 203 is placed on the printed wiring board 201 so that the distance D5 in the sub-scanning direction of the light emitting portions 205 of the adjacent semiconductor light emitting element array chips 203 is as small as possible. It is desirable to implement the above. For this reason, it is desirable to make the distance D6 between adjacent semiconductor light emitting element array chips 203 as small as possible. In practice, the distance D6 is, for example, about 10 μm to 50 μm.

  Also, the adhesive 202 can be transferred and formed on the printed wiring board 201 using a stamp function provided in a die bonding apparatus (not shown) as in the first and second embodiments. It can also be formed on the printed wiring board 201 in advance by an apparatus (not shown). At this time, the adhesive 202 is formed in contact with the entire back surface of the semiconductor light emitting element array chip 203.

  Further, as described above, the wire bonding pad 213 for data input / output with the external drive circuit is formed on the step portion 210 of each semiconductor light emitting element array chip 203, while the printed wiring board 201 is formed on the printed wiring board 201. A wire bonding pad 215 for inputting / outputting data to / from each semiconductor light emitting element array chip 203 is formed in a pair with a wire bonding pad 213 on the step portion 210 of each semiconductor light emitting element array chip 203. The wire bonding pads 215 on the printed wiring board 201 are formed at predetermined intervals in the sub-scanning direction from the wire bonding pads 213 on the step portions 210 of the respective semiconductor light emitting element array chips 203.

  Then, a wire bonding pad 213 on the step portion 210 of each semiconductor light emitting element array chip 203 and a wire bonding pad 215 to be paired on the printed wiring board 201 are connected using an Au wire 216. Here, it is desirable that the height of the substantially hemispherical ball portion 217 used for the connection portion between the wire bonding pad 213 and the Au wire 216 on the step portion 210 is lower than that of the wall portion 211. For this reason, it is desirable to make the depth from the surface 204 to the stepped surface 209 deeper than the height of the ball portion 217 so that the upper end of the ball portion 217 does not protrude upward from the upper surface of the wall portion 211. Therefore, in fact, the stepped portion 210 has a depth to the stepped surface 209 larger than the height of the ball portion 217, so that the upper end of the ball portion 217 does not protrude above the upper surface of the wall portion 211. It is like that.

  In the semiconductor light emitting element array chip 203, the thickness from the surface 204 to the stepped surface 209 is determined by adding the height of the ball portion 217 and the thickness of the wire bonding pad 215 in consideration of the thickness of the wire bonding pad 215. It is deeper than the length.

  Then, a ROM (not shown) for writing data, a chip capacitor (not shown), a connector for data input / output (not shown) with the LED printer 1 side, and the like are mounted on the printed wiring board 201. Thus, the COB 200 for the LED print head 8 is configured. The COB 200 is incorporated into the frame 30 of the LED print head 8 as in the first and second embodiments.

[3-2. Effects of the third embodiment]
Here, the effect of the third embodiment will be described. The effect of providing the stepped portion 208 on the opposite surface side of the extended portion 206 of the semiconductor light emitting element array chip 203 is the same as that of the second embodiment, and thus detailed description thereof is omitted.

  In the third embodiment, as described above, the step portion having the step surface 209 that is one step lower than the surface 204 not only on the facing surface side but also on the non-facing surface side of the extended portion 206 of the semiconductor light emitting element array chip 203. 210 is provided, and a wall portion 211 having the same height as the surface 204 is left between the step portion 208 on the facing surface side and the step portion 210 on the non-facing surface side. Then, the wire bonding pad 213 is formed on the step surface 209 on the non-facing surface side.

  Here, when the semiconductor light emitting element array chips 203 are actually arranged in a zigzag pattern, the extending portions 206 of the adjacent semiconductor light emitting element array chips 203 are also arranged in a staggered manner. That is, the extended portion 206 of each semiconductor light emitting element array chip 203 is opposed to the central portion (that is, the portion where the light emitting portion 205 is formed) of the adjacent semiconductor light emitting element array chip 203 in the sub-scanning direction. To be implemented.

  At this time, the ball portion 217 of the Au wire 216 formed on the wire bonding pad 213 of the step portion 210 located on the non-opposing surface side of the extended portion 206 is on the light emitting portion 205 side at a position facing the sub-scanning direction. From behind, it will be hidden behind the wall 211. As a result, the ball portion 217 of the Au wire 216 is positioned outside the radiation angle range of the light emitted from the light emitting portion 205 as shown in FIG. The incident light can be prevented from reaching the ball portion 217 of the Au wire 216 formed on the stepped portion 210 on the non-facing surface side and being reflected.

  Actually, when the light emitted from the light emitting portion 205 reaches the ball portion 217 of the Au wire 216 and is reflected, for example, an unintended portion of the photosensitive drum 5 is exposed by the reflected light, and as a result, printing is performed. As a result, streaks, lines, and the like are included, and print quality deteriorates. In other words, if it is possible to suppress the light emitted from the light emitting unit 205 from being reflected on the ball part 217 of the Au wire 216, it is possible to prevent streaks and lines from entering the printing result, and to achieve higher quality printing. Is possible.

  As described so far, according to the COB 200 of the third embodiment, in addition to obtaining the same effect as that of the second embodiment, the light from the light emitting unit 205 is reflected by the ball of the Au wire 216. Reflection to the portion 217 can be suppressed. The LED printer 1 mounted with the COB 200 can perform higher quality printing.

  In the third embodiment described above, the stepped portion 210 having a stepped surface 209 that is one step lower than the surface 204 is provided on the non-facing surface side of the extended portion 206, and the wire bonding pad 213 is provided on the stepped surface 209. However, the present invention is not limited to this. For example, instead of the stepped portion 210, a concave portion (not shown) is formed on the non-opposing surface side of the extended portion 206, and wire bonding is performed at the bottom of the concave portion. By forming the pad 213, the ball portion 217 of the Au wire 216 may be hidden in the recess. In this case, the depth of the concave portion may be made deeper than the height of the ball portion 217. Even with such a structure, it is possible to suppress the light emitted from the light emitting portion 205 from being reflected by the ball portion 217 of the Au wire 216. In this case, a recess may be formed for each wire bonding pad 213, or the size of the recess may be increased to form a plurality of wire bonding pads 213 in one recess. May be.

  In the third embodiment described above, ball bonding is used as a bonding method for the Au wire 216 connected to the wire bonding pad 213, but stitch bonding may be used. When stitch bonding is used as described above, generally, the area of the wire bonding pad 213 needs to be formed larger than that when ball bonding is used. For this reason, the chip width of the semiconductor light emitting element array chip 203 is also larger than that in the case of using ball bonding, but on the other hand, the height of the stitch portion can be made lower than the height of the ball portion 217. The reflection of light can be further suppressed, and the depth of the stepped portion 210 can be reduced to about 10 μm, for example.

[4. Other Embodiments]
[4-1. Other Embodiment 1]
In the first to third embodiments described above, the present invention is applied to the LED print head 8 as an exposure head mounted on the LED printer 1, but the present invention is not limited to this, and light emission other than the LED is performed. The present invention can also be applied to an exposure head that uses an element. Further, for example, the present invention can be applied to a CIS (contact image sensor) as a read head mounted on a scanner or the like.

  When applied to the CIS, for example, a semiconductor light-receiving element array chip in which light-receiving elements are arranged in a one-dimensional array may be of a structure that is fixed on a printed wiring board via an adhesive. With such a CIS, the present invention can be applied in the same manner as in the first to third embodiments described above.

  Furthermore, in the first to third embodiments described above, the present invention is applied to the COBs 33, 100, and 200 as semiconductor devices. However, the present invention is not limited to this, and a semiconductor chip is fixed on a substrate via an adhesive. If the semiconductor device has such a structure, the present invention can be applied in the same manner as in the first to third embodiments described above. Moreover, as a semiconductor chip in this case, what is necessary is just to have a plurality of semiconductor elements provided on the surface.

  Furthermore, in the first to third embodiments described above, the present invention is applied to the LED printer 1 as an image forming apparatus. However, the present invention is not limited to this, and a printer equipped with an exposure head using a light emitting element other than an LED, The present invention can also be applied to image forming apparatuses such as scanners, facsimiles, MFPs (Multi Function Products) and copiers equipped with reading heads such as CIS.

  Furthermore, in the first to third embodiments described above, Au wires 40, 103, and 216 are used as the wires. However, the present invention is not limited thereto, and Cu wires or the like are used as long as they are conductive wires. It may be.

[4-2. Other Embodiment 2]
Furthermore, the present invention is not limited to the above-described first to third embodiments and other embodiments. That is, the scope of application of the present invention extends to embodiments in which some or all of the above-described embodiments and other embodiments are arbitrarily combined, and embodiments in which some are extracted.

  The present invention can be widely used in, for example, an exposure head and a reading head made of COB.

  DESCRIPTION OF SYMBOLS 1 ... LED printer, 7 ... Exposure apparatus, 8 ... LED print head, 9 ... Developing apparatus, 33, 52, 100, 122, 200 ... COB, 34, 51, 101, 121, 201 ... Print Wiring board, 35, 50, 102, 120, 203 ... Semiconductor light emitting element array chip, 40, 57, 103, 128, 216 ... Au wire, 41, 53, 104, 123, 202 ... Adhesive, 43, 54, 106, 124, 205... Light emitting part, 44, 47, 55, 56, 108, 113, 126, 127, 213, 215... Wire bonding pad, 46, 110, 208, 210. 107, 125, 206... Stretched portion, 217... Ball portion.

Claims (16)

A semiconductor chip provided with a plurality of semiconductor elements on the surface;
A board on which a plurality of the semiconductor chips are mounted side by side,
The back surface of the semiconductor chip and the surface of the substrate are bonded via an adhesive,
The said semiconductor chip has a level | step-difference part lower than the surface in which the said semiconductor element is provided in the edge part which opposes the adjacent semiconductor chip. Semiconductor device. The semiconductor device according to claim 1, wherein the step portion has a step surface lower than a surface of the semiconductor chip. On the surface of the plurality of semiconductor chips, the plurality of semiconductor elements are arranged along the longitudinal direction of the semiconductor chip,
The semiconductor device according to claim 2, wherein adjacent semiconductor chips are mounted side by side in a straight line on the substrate such that end faces in the longitudinal direction are opposed to each other. Since the endmost semiconductor elements are respectively formed at both ends in the longitudinal direction of the surface of the semiconductor chip, the stepped portions are formed at the ends in the longitudinal direction of the surface of the semiconductor chip. The semiconductor device according to claim 3, wherein the semiconductor device is formed so as to avoid a region in which is formed. The semiconductor device according to claim 4, wherein a corner of a region where the outermost semiconductor element is formed has an R shape. Of the wall surfaces connecting the step surface of the step portion and the surface of the semiconductor chip, an angle formed by a wall surface orthogonal to the longitudinal direction of the semiconductor chip and an end surface parallel to the longitudinal direction of the semiconductor chip is R The semiconductor device according to claim 4. On the surface of the plurality of semiconductor chips, the plurality of semiconductor elements are arranged along the longitudinal direction of the semiconductor chip,
The semiconductor device according to claim 2, wherein adjacent semiconductor chips are mounted side by side in a staggered manner on the substrate such that end faces in the short direction are opposed to each other. The semiconductor chip has stretched portions at both ends in the longitudinal direction, which are stretched outward in the longitudinal direction from the outermost semiconductor element,
In the extended portion, the stepped portion is formed on an end surface facing an adjacent semiconductor chip, and wire bonding for connecting to the substrate via a wire on a non-facing surface opposite to the end surface is performed. The semiconductor device according to claim 7, wherein a pad for forming is formed. Of the wall surfaces connecting the step surface of the step portion and the surface of the semiconductor chip, an angle formed by a wall surface parallel to the longitudinal direction of the semiconductor chip and an end surface orthogonal to the longitudinal direction of the semiconductor chip, and The semiconductor device according to claim 8, wherein corners formed by a wall surface orthogonal to the longitudinal direction of the semiconductor chip and an end surface parallel to the longitudinal direction of the semiconductor chip are each R-shaped. A step portion having a step surface lower than the surface on which the semiconductor element is provided is also formed on the non-facing surface side of the extending portion, and the wire bonding pad is formed on the step surface of the step portion. The semiconductor device according to claim 8. The stepped portion formed on the non-facing surface side of the extended portion has a depth from the surface of the semiconductor chip to the stepped surface that is higher than the height of the ball portion of the wire formed at the connection point with the wire bonding pad. The semiconductor device according to claim 10, which is deeper than the depth. The semiconductor device according to claim 10, wherein the stepped portion on the facing surface side and the stepped portion on the non-facing surface side of the extending portion are formed in the same process by a digging process by etching. The semiconductor device according to claim 1, wherein the semiconductor chip is mainly made of a GaSa substrate. The semiconductor device according to claim 1, wherein the semiconductor chip is configured by integrating semiconductor elements made of GaSa on an IC drive circuit substrate. A semiconductor chip provided on the surface with a plurality of light-emitting elements serving as light sources for exposure;
A board on which a plurality of the semiconductor chips are mounted side by side,
The back surface of the light emitting element chip and the surface of the substrate are bonded via an adhesive,
The light emitting element chip has a step portion lower than a surface on which the semiconductor element is provided at an end facing the adjacent semiconductor chip. An exposure apparatus having a substrate on which a plurality of semiconductor chips each provided with a plurality of light emitting elements serving as light sources for exposure are arranged and mounted;
A developing device that forms an image by developing a latent image obtained as a result of exposure by the exposure device;
The back surface of the light emitting element chip and the surface of the substrate are bonded via an adhesive,
The image forming apparatus, wherein the light emitting element chip has a step portion lower than a surface on which the semiconductor element is provided at an end portion facing an adjacent semiconductor chip.

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