JP4503578B2 - Printed wiring board - Google Patents

Description

The present invention relates to a printed wiring board having a plurality of wiring layers, and in particular, a printed circuit board that can improve electrical yield (interlayer connection) between wiring layers and wiring pattern formation to improve manufacturing yield, productivity, and the like. about the wiring board.

  With recent demands for reducing the size and weight of electronic devices, the various electronic components that make up these devices are also becoming increasingly smaller, lighter, and more functional. Among them, in semiconductor components, so-called area arrays are being developed in which a multi-pin narrow pitch and a surface area connection are made in an electrical connection portion.

  In an electronic device, a plurality of electronic components are used to provide a predetermined function. However, it can be said that the use of a printed wiring board is indispensable for mounting electronic components. The printed wiring board, which is an important component, is also made through the formation of through-holes (through-holes) and plating on the inner surface with the progress of smaller and lighter electronic components, narrowing of multi-pin pitch of semiconductor components and area array. The through-hole type printed wiring board for connection is becoming incapable of handling due to the wasteful mounting density.

  For this reason, an example of a conventional multilayer printed wiring board having interlayer connections other than through-holes used will be described with reference to FIG. This figure schematically shows a manufacturing process flow of a build-up type printed wiring board, in which the process proceeds in the order of (a), (b), (c), and (d).

  First, as shown in FIG. 5A, conductive patterns 72 are formed on both surfaces of the core plate 71, and through holes 73 are provided as interlayer connections as necessary. Next, as shown in FIG. 4B, the through hole 73 is filled with the insulating resin 74 and the insulating layer 75 is stacked on the core plate 71 to be formed. Here, via holes 76 for interlayer connection portions are provided in the insulating layer 75 as necessary. For this purpose, a method of forming by photolithography using a photosensitive resin, a method of forming a hole by laser processing after forming the insulating layer 75, or the like can be used.

  Further, a conductive layer 77 is formed and patterned as shown in FIG. Plating can be used for forming the conductive layer 77. Etching can be used for patterning. Vias 79 that form interlayer connections are formed in the via holes 76 by plating.

  In the case of further multilayering, an insulating layer 78 is laminated on the conductive layer 77 as shown in FIG. 4D, and thereafter, the conductive layer is similarly formed and patterned. That is, a multilayer printed wiring board is manufactured by repeating the process shown in FIG.

  In such a multilayer printed wiring board, at least a through hole for interlayer connection between inner layers is not required, and the component mounting density on the outer surface of the printed wiring board is increased as compared with the through hole substrate.

  However, such a multilayer printed wiring board is still a method of sequentially forming an insulating layer and a conductor layer on a core board as a manufacturing method, and from the viewpoint of manufacturing yield, productivity, etc. There are items to be improved.

  That is, the individual lamination processes are not necessarily simple processes, and such processes are accumulated in proportion to the multilayered printed wiring board. For this reason, the overall yield of the finished product is the product of the formation process yield of each layer, which causes a deterioration in yield. In particular, the formation of vias by plating not only makes it difficult to ensure the uniformity of plating thickness but tends to cause poor interlayer connection, but also due to non-uniform plating thickness, the formation of wiring patterns by etching is inaccurate and results in deterioration of yield. It becomes a factor. In addition, it is difficult to improve productivity because there are no steps to be performed in parallel because they are sequentially stacked. Furthermore, a special process called a hole filling process of the through hole of the core plate is required. For these reasons, it is generally difficult to reduce the price.

  In addition, vias exist on one side of the manufactured printed wiring board, and lands for component mounting cannot be provided at those portions. For this reason, it can be said that there is still room for improving component mounting efficiency and wiring efficiency.

The present invention has been made in consideration of the aforementioned circumstances, Oite the printed wiring board in which the wiring layers there are multiple, high reliability, and high reliability of the pattern formation of the electrical connection of the wiring layers to each other It is an object of the present invention to provide a printed wiring board capable of improving the production yield and productivity. Another object of the present invention is to provide a printed wiring board that further improves the density of component mounting and the wiring density.

In order to solve the above problems, a printed wiring board according to one embodiment of the present invention is provided on an insulating layer having a first surface and a second surface, and on the first surface of the insulating layer. A first wiring layer having a layered conductor; a second wiring layer provided on the second surface of the insulating layer; and the insulating layer and the second wiring reaching the layered conductor A conductive composition filling a hole penetrating the layer and protruding from the hole onto the upper surface of the second wiring layer; a first conductive pillar provided in contact with the conductive composition; and the second And a second conductive pillar made of the same material as the first conductive pillar, which is provided in contact with the wiring layer.

According to is this, interlayer connection is made by a conductive composition filled in the hole formed in the insulating layer separating the wiring layer. Since it is not necessary to use a plating process, the reliability of interlayer connection is improved. The patterning of the wiring layer can be performed on the metal layer that can be manufactured with a uniform thickness irrespective of the interlayer connection, and therefore, a finer pattern can be formed with a high yield.

  As a result, the reliability of electrical connection between the wiring layers and the reliability of pattern formation can be improved, and the manufacturing yield can be improved.

According to the present invention can be improved Oite the printed circuit board wiring layer there are multiple electrical high reliability and patterning production yield achieving high reliability of the connection of the wiring layers to each other, and productivity . In addition to this, the density of component mounting and the wiring density can be further improved.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a cross-sectional view schematically showing a manufacturing process of a printed wiring board which is a premise of the printed wiring board according to an embodiment of the present invention. The process proceeds in the order of (a), (b), (c), and (d) in FIG.

  First, as shown in FIG. 2A, an insulating layer (100 μm thick glass epoxy plate in this example) 11 having metal layers (18 μm thick Cu foil) 12 and 13 on both sides is prepared. Next, as shown in FIG. 5B, the metal layers 12 and 13 on both sides are etched to form a pattern such as necessary wiring. At this time, in addition to the normal patterns 12b and 13b, patterns 12a and 13a (substantially circular shapes having a diameter of 300 μm in this example) as portions for performing interlayer connection are simultaneously formed at the same position. Note that a hole 14 (in this example, a diameter of 100 μm) is formed inside the pattern 13a on one surface. This is also formed simultaneously by etching. For easy understanding, the hole 14 is drawn larger than the actual size.

  Next, as shown in FIG. 2C, the hole 15 is formed in the insulating layer 11 by, for example, a carbon dioxide gas laser using the hole 14 as a mask. The hole 15 penetrates the insulating layer 11 and reaches the pattern 12a. Only the etching process and the laser process are used in the processes so far, and the etching process is also a mask forming process for the laser process, and can be performed efficiently. In addition, since the etching process is performed on the metal layer that is originally processed to have a uniform thickness, a fine pattern can be formed with a high yield. In addition, it can also machine with an NC machine instead of laser processing.

  Further, as shown in FIG. 4D, the formed holes 15 are filled with a conductive paste (in this example, a silver paste) 16 by screen printing. In this example, screen printing uses a screen plate in which a 10 μm emulsion is coated on 325 stainless screens per inch. A silver paste for silver through holes is used as a silver paste, and a flat squeegee is used as a squeegee for rubbing the screen plate. As a result, the conductive paste 16 is filled in the holes 15 until a protruding portion having a thickness of 5 to 15 μm is formed in the pattern 13a, and a good interlayer connection between the pattern 13a and the pattern 12a is formed.

  It should be noted that a method other than screen printing may be used for filling the hole 15 with the conductive paste. For example, a method using a dispenser can be used. The same applies to the following.

  As described above, the two-layer printed wiring board 25 as a premise can be obtained.

Next, FIG. 2 is a cross-sectional view schematically showing a process for manufacturing a multilayer wiring board using the printed wiring board according to the embodiment of the present invention . The components already described will be described with the same numbers. The process proceeds in the order of (a), (b), (c), and (d) in FIG.

  This printed wiring board is a four-layer printed wiring board using two of the two-layer printed wiring boards 25 described above.

  First, as shown in FIG. 1A, a printed wiring board 25 manufactured by the process shown in FIG. 1 is prepared. In this figure (a), it is shown upside down from FIG. 1 (d).

  Next, as shown in FIG. 2B, conductive bumps 21 are formed on the necessary portions of the conductive paste 16. The conductive bumps 21 can be formed, for example, by screen printing a conductive paste (for example, a paste in which silver fine particles are dispersed). Note that the conductive bumps 21 may be formed on a layer having no interlayer connection just like the pattern 13b. Such an embodiment shown in FIG. 2B is a useful material for manufacturing a multilayer wiring board, as will be described below.

  Next, as shown in FIG. 2C, a semi-cured prepreg (made of glass epoxy in this example) 22 is passed through the conductive bumps 21 and laminated.

  Further, as shown in FIG. 4D, another printed wiring board 25a is placed so that the conductive paste 16 is on the inside and the conductive bumps 21 are interlayer connection (conductive pillar). Laminate on top. At this time, by heating and pressurizing and laminating, the prepreg 22 is cured, and the heads of the conductive bumps 21 are crushed and interlayer connection is made.

  As described above, a four-layer printed wiring board can be obtained.

  In this example, the first printed wiring board 25 and the second printed wiring board 25a can be separately manufactured in parallel. Therefore, unlike the build-up substrate, productivity can be improved by parallel manufacturing for each part.

  In addition, it is possible to perform electrical and optical inspections for each of these parts, and manufacturing can be performed by combining only good products, so that the yield is also improved. Further, since the conductive paste 16 is not protruded and only the patterned metal layer is present on the outer surface of the printed wiring board thus laminated (a so-called pad-on-via structure), a land for component mounting is provided. The position is not limited, and the component mounting density and wiring density can be further improved.

  Furthermore, if such a printed wiring board is applied to an electronic device, the degree of freedom of wiring is high, and therefore the pattern design time can be shortened.

As a modification of the printed wiring board in this example (reference example), it can take the form shown in Figure 3. The same reference numerals are given to the components already described in FIG.

  In this example, the conductive bump 21 is not used for the interlayer connection between the inner layers, and the necessary interlayer connection through the prepreg 22 is made by the conductive plating 301 formed on the inner surface of the through hole 302. It is. The through-hole 302 can be formed by drilling a through-hole with a drill after completing the entire lamination. The plating 301 can be copper plating.

  Even with such a through hole 302 and plating 301, any necessary interlayer connection can be achieved. FIG. 3 shows an example of connecting the uppermost wiring layer, the second wiring layer, and the lowermost wiring layer.

Next, FIG. 4 with a printed wiring board according to another embodiment of the present invention, FIG. 5 will be described with reference to FIG. FIG. 4 is a cross-sectional view schematically showing a printed wiring board according to another embodiment of the present invention together with a manufacturing process flow. The process proceeds in the order of (a), (b), (c), and (d) in FIG. FIG. 5 is a continuation diagram of FIG. 4, and is a cross-sectional view schematically showing a similar printed wiring board together with a manufacturing process flow. FIG. 5 (a), (b), FIG. The process proceeds in the order of (c). FIG. 6 is a continuation diagram of FIG. 5, and is a cross-sectional view schematically showing a similar printed wiring board together with a manufacturing process flow. FIG. 6 (c) is followed by FIGS. 6 (a), (b), The process proceeds in the order of (c) and (d).

  First, as shown in FIG. 4A, an insulating layer 31 (100 μm thick glass epoxy plate in this example) 31 having metal layers (in this example, 18 μm thick Cu foil) 32 and 33 on both sides is prepared. Next, as shown in FIG. 4B, the metal layer 33 on one side is etched to form a pattern such as necessary wiring. At this time, in addition to the normal pattern 33b, a pattern 33a (substantially circular shape with a diameter of 300 μm in this example) and a pattern 33c (same as this) are also formed simultaneously. Here, a hole 34 (in this example, a diameter of 100 μm) is formed in the pattern 33a. This is also formed simultaneously by etching.

  Next, as shown in FIG. 4C, the hole 35 is formed in the insulating layer 31 by, for example, a carbon dioxide gas laser using the hole 34 as a mask. The hole 35 penetrates the insulating layer 31 and reaches the metal layer 32.

  Next, as shown in FIG. 4D, the formed holes 35 are filled with a conductive paste (in this example, a silver paste) 36 by screen printing. In this example, screen printing uses a screen plate in which a 10 μm emulsion is coated on 325 stainless screens per inch. A silver paste for silver through holes is used as a silver paste, and a flat squeegee is used as a squeegee for rubbing the screen plate. Thereby, the conductive paste 36 is filled in the holes 15 until a protruding portion having a thickness of 5 to 15 μm is formed in the pattern 33 a, and a good interlayer connection between the pattern 33 a and the metal layer 32 is formed.

  Next, as shown in FIG. 4E, an insulating layer (prepreg) 37 and a metal layer (copper foil in this example) 38 are pressed and laminated on the surface where the conductive paste 36 protrudes. Thereby, the wiring layer becomes three layers.

  Next, as shown in FIG. 5A, the metal layers 32 and 38 on both sides are etched to form a pattern such as necessary wiring. At this time, in addition to the normal patterns 32b and 38b, a pattern 32a (substantially circular shape with a diameter of 300 μm in this example), 32c (same), patterns 38a (same), 38c (same), and 38d as portions for performing interlayer connection. (Same) is formed at the same time. Here, holes 39 (in this example, a diameter of 100 μm) are formed inside the patterns 38a, 38c, and 38d. This is also formed simultaneously by etching.

  Next, as shown in FIG. 5B, holes 310a, 310b, and 310c are formed in the insulating layer 37 by, for example, a carbon dioxide gas laser using the hole 39 as a mask. These holes 310a, 310b, and 310c penetrate through the insulating layer 37, and possibly through the insulating layer 31, and reach the conductive paste 36, the pattern 33c, or the pattern 32c.

  Next, as shown in FIG. 5C, the formed holes 310a, 310b, and 310c are filled with conductive paste (silver paste in this example) 311a, 311b, and 311c by screen printing. In this example, screen printing uses a screen plate in which a 10 μm emulsion is coated on 325 stainless screens per inch. A silver paste for silver through holes is used as a silver paste, and a flat squeegee is used as a squeegee for rubbing the screen plate. Thus, the conductive pastes 311a, 311b, and 311c are filled in the holes 310a, 310b, and 310c until the protruding portions having a thickness of 5 to 15 μm are formed in the patterns 38a, 38c, and 38d, and the patterns 38a, 38c, and 38d are electrically conductive. Good interlayer connection with the conductive paste 36, the pattern 33c, or the pattern 32c is formed.

  As described above, a three-layer printed wiring board 51 can be obtained. Further, as shown in FIG. 5E, these three wiring layers can be connected to each other between the arbitrary wiring layers by the above-described etching, laser processing, and screen printing.

  The etching process and laser processing used in the above steps can be efficiently performed because the etching process is also a mask forming process for laser processing. In addition, since the etching process is performed on the metal layer that is originally processed to have a uniform thickness, a fine pattern can be formed with a high yield. In addition, it can also machine with an NC machine instead of laser processing. These effects are the same as those described for the printed wiring board shown in FIG. 1 having two wiring layers.

Next, the printed wiring board 6 layers with two sheets of printed wiring board 51 of the three layers described above.

  First, as shown in FIG. 4A, a printed wiring board 51 manufactured by the processes shown in FIGS. 4 and 5 is prepared. In this figure (a), it is shown upside down from FIG. 5 (c).

  Next, as shown in FIG. 4B, conductive bumps 312a are formed on the necessary portions of the conductive pastes 311a, 311b, 311c. The conductive bump 312a can be formed, for example, by screen printing a conductive paste (for example, a paste in which silver fine particles are dispersed). The conductive bump may be formed on a pattern that does not have an interlayer connection just like the pattern 38e (conductive bump 312b).

  Next, as shown in FIG. 3C, a semi-cured prepreg (made of glass epoxy in this example) 313 is passed through the conductive bumps 312a and 312b and laminated.

  Further, as shown in FIG. 4 (d), another printed wiring board 51a is connected to each other so that the conductive paste 311a (or 311b, 311c) is on the inner side and the conductive bumps 312a, 312b are connected to each other (interlayer connection). A conductive pillar is stacked thereon. At this time, the prepreg 313 is cured by heating and pressurizing and the heads of the conductive bumps 312a and 312b penetrating the prepreg 313 are crushed, and an interlayer connection is made.

  As described above, a six-layer printed wiring board can be obtained.

  In this example, the first printed wiring board 51 and the second printed wiring board 51a can be separately manufactured in parallel. Therefore, unlike the build-up substrate, productivity can be improved by parallel manufacturing for each part.

  In addition, it is possible to perform electrical and optical inspections for each of these parts, and manufacturing can be performed by combining only good products, so that the yield is also improved. Further, since the conductive paste 36, 311c is not protruded and only the patterned metal layer is present on the outer surface of the printed wiring board thus laminated, there is no restriction on the land position for component mounting. It is possible to further improve the mounting density and the wiring density. These effects are the same as those described for the printed wiring board shown in FIG. 2 having four wiring layers.

  Next, another process for manufacturing a multilayer wiring board using a printed wiring board according to an embodiment of the present invention will be described with reference to FIG. This figure is a cross-sectional view schematically showing another process for manufacturing a multilayer wiring board using a printed wiring board according to an embodiment of the present invention. is there.

  This printed wiring board is a six-layer printed wiring board using three of the two-layer printed wiring boards 25 described above.

  As a manufacturing method, as shown in FIG. 2A, the printed wiring board 25 manufactured by the process shown in FIG. 1 and two pieces (25a, 25c) on which conductive bumps 21 necessary for the printed wiring board 25 are formed ). A layer in which the conductive paste 16 does not protrude is disposed in the outermost wiring layer, and semi-cured prepregs 61a and 61b are disposed between the printed wiring boards 25, 25b, and 25c.

  These arrangements are laminated by heating and pressing. As a result, as shown in FIG. 7 (b), the prepregs 61a and 61b are cured, and the heads of the conductive bumps 21 penetrating them are crushed to form an interlayer connection.

  As a result, a printed wiring board having six wiring layers can be obtained.

  Also in this example, the first printed wiring board 25, the second printed wiring board 25b, and the third printed circuit board 25c can be separately manufactured in parallel. Therefore, unlike the build-up substrate, productivity can be improved by parallel manufacturing for each part.

  In addition, it is possible to perform electrical and optical inspections for each of these parts, and manufacturing can be performed by combining only good products, so that the yield is also improved. Further, since the conductive paste 16 is not protruded and only the patterned metal layer is present on the outer surface of the printed wiring board laminated in this manner, there is no restriction on the land position for component mounting. The density and wiring density can be further improved. These effects are the same as those described for the printed wiring board shown in FIG. 2 having four wiring layers and FIG. 6 having six wiring layers.

Further, if an additional 2-layer printed wiring board 25 more placement (or 3-layer printed wiring board 51) of the as shown in FIG. 7, it is possible to obtain the 7 or more layers of the printed wiring board.

  As described above in detail, according to each embodiment, the interlayer connection is made of the conductive composition filled in the holes formed in the insulating layer separating the wiring layers, and there is no need to use a plating process. Improves reliability and patterning of wiring layers can be performed on metal layers that can be manufactured to a uniform thickness regardless of this interlayer connection, which enables high reliability of electrical connection between wiring layers And the reliability of pattern formation can be improved, and the manufacturing yield can be improved. In addition, the outer surface of the printed wiring board laminated in this way can be made to have only a patterned metal layer without protruding the conductive composition, thus limiting the land position for component mounting. It is possible to further improve the density of component mounting and wiring density.

Sectional drawing which shows typically the manufacturing process of the printed wiring board used as the premise of the printed wiring board which concerns on one Embodiment of this invention. Sectional drawing which shows typically the process which manufactures a multilayer wiring board using the printed wiring board which concerns on one Embodiment of this invention . Sectional drawing which shows typically the modification (reference example) of the multilayer wiring board shown in FIG. Sectional drawing which shows typically the printed wiring board which concerns on another embodiment of this invention with a manufacturing process flow. FIG. 5 is a continuation diagram of FIG. 4, and is a cross-sectional view schematically showing a printed wiring board according to another embodiment of the present invention together with a manufacturing process flow. FIG. 6 is a sectional view of FIG. 5 schematically showing a printed wiring board according to another embodiment of the present invention together with a manufacturing process flow. Sectional drawing which shows typically another process which manufactures a multilayer wiring board using the printed wiring board which concerns on one Embodiment of this invention. The figure which shows typically the manufacturing process flow of the printed wiring board of a buildup system.

Explanation of symbols

  11, 31, 37 ... insulating layer, 12, 13, 32, 33, 38 ... metal layer, 12a, 12b, 13a, 13b, 32a, 32b, 32c, 33a, 33b, 33c, 38a, 38b, 38c, 38d, 38e ... pattern, 14, 34, 39 ... hole, 15, 35, 310a, 310b, 310c ... hole, 16, 36, 311a, 311b, 311c ... conductive paste, 21, 312a, 312b ... conductive bump, 22, 61a, 61b, 313 ... prepreg, 25, 25a, 25b, 25c ... printed wiring board, 51, 51a ... printed wiring board, 301 ... plating, 302 ... through hole.

Claims (1)

An insulating layer having a first surface and a second surface;
A first wiring layer having a layered conductor provided on the first surface of the insulating layer;
A second wiring layer provided on the second surface of the insulating layer;
A conductive composition that fills a hole penetrating the insulating layer and the second wiring layer and reaches the upper surface of the second wiring layer from the hole, reaching the layered conductor;
A first conductive pillar provided on and in contact with the conductive composition;
A printed wiring board comprising: a second conductive pillar made of the same material as the first conductive pillar, provided in contact with the second wiring layer.

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