JP2005175097A - Wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wiring board in which signals do not jump over between parallel parts of a signal wiring conductor to propagate, high frequency signals are propagated well to a plurality of signal wiring conductors at an identical timing, and mounter electronic parts can normally be operated. <P>SOLUTION: The wiring board comprises a linear wiring conductor 2cs which is formed on the surface of an insulating layer 1b. The board is provided with the parallel parts which have at least a part formed with a plurality of bending parts and are parallel to each other by the plurality of bending parts, and a conductive layer 11 which is formed so as to be pinched inside the parallel parts on the surface of the insulating layer 1b and is electrically independent from the wiring conductor 2cs. <P>COPYRIGHT: (C)2005,JPO&amp;NCIPI

Description

  The present invention relates to a wiring board for mounting electronic components such as semiconductor elements.

  In general, along with the demand for downsizing and thinning of electronic devices such as mobile communication devices, wiring boards for mounting electronic components such as semiconductor elements used in such electronic devices are also small. There is a demand for reduction in size, thickness, and number of terminals. As a wiring board for realizing such miniaturization, thinning, and multi-terminal, for ball grid array packages (BGA) and chip scales that can be surface-mounted on the external electric circuit board via solder bumps. A wiring board for a package (CSP) has been put into practical use.

  Such a wiring substrate for a ball grid array package or a chip scale package is used for connecting an electronic component in which an electrode of the electronic component is connected to the central region of the upper surface of the insulating substrate in which a plurality of insulating layers are stacked via solder. The pads are provided in a grid-like arrangement, and external connection pads that are connected to the wiring conductors of the external electric circuit board via solder are provided in a grid-like arrangement over substantially the entire lower surface of the insulating substrate. A wiring conductor for electrically connecting the electronic component connecting pad and the external connecting pad is formed so as to extend vertically through the insulating layer of the insulating substrate and horizontally extend between the insulating layers. ing.

  And according to such a wiring board, it becomes an electronic device by mounting an electronic component on an insulating substrate so that its electrode is connected to an electronic component connecting pad via solder. The external connection pads are connected to the wiring conductors of the external electric circuit board via solder to be mounted on the external electric circuit board and the electronic components to be mounted are electrically connected to the external electric circuit; Become.

  Wiring conductors in such a wiring board are functionalized into wiring conductors for signals, grounds, and power supplies depending on applications.

  Among these, the signal wiring conductor functions as a conductive path for propagating an electric signal between an electronic component such as a semiconductor element and the external electric circuit board, and the insulating layer is directed from the central region to the outer peripheral region of the insulating substrate. A plurality of thin wire conductors formed so as to extend, and are electrically connected to a signal electronic component connection pad and an external connection pad by a through conductor penetrating the insulating layer.

  In addition, the wiring conductor for grounding and the wiring conductor for power supply function as a supply path for supplying the ground potential and the power supply potential to the electronic components mounted on the wiring board, respectively, and the signal wiring It has an electromagnetic shielding function for the conductor and a characteristic impedance adjustment function, and has a large-area conductor layer arranged so as to face the signal wiring conductor across the insulating layer, and penetrates through the insulating layer. The conductors are electrically connected to the grounding and power supply electronic component connection pads and the external connection pads, respectively.

In such a wiring board, the signal wiring conductors extending between the insulating layers are substantially the same by converting the signal propagation delay time in a plurality of wiring conductors to propagate signals at the same timing into the length of the wiring. In order to do this, for example, a part thereof may be formed to have a plurality of bent portions and to be folded back in a zigzag manner.
JP 2003-152290 A

  However, as described above, when a part of the signal wiring conductor has a plurality of bent portions and is formed so as to be folded and extended, the parallel portions parallel to each other by the plurality of bent portions are formed on a part of the wiring conductor. Is formed. In this way, when a high-frequency signal of, for example, 10 GHz or more is propagated to a signal wiring conductor having parallel portions parallel to each other, the signal may jump over and propagate between the parallel portions of the signal wiring conductor. As a result, the propagation delay times of signals in a plurality of wiring conductors to which signals should be propagated at the same timing are different, and the timings of the signals are shifted, thereby causing electronic components such as semiconductor elements to be mounted on the wiring board. Triggers the problem of being unable to operate normally.

  The present invention has been completed in view of such conventional problems, and its purpose is to allow signals to jump between parallel portions of signal wiring conductors in which parallel portions parallel to each other are formed by a plurality of bent portions. An object of the present invention is to provide a wiring board that can propagate a high frequency signal to a plurality of signal wiring conductors at the same timing without causing propagation, and can normally operate an electronic component to be mounted.

  The wiring board of the present invention has a linear wiring conductor formed on the surface of the insulating layer and having a plurality of bent portions at least partially and provided with parallel portions parallel to each other by the plurality of bent portions; It is characterized by comprising a conductor layer formed to be sandwiched between the parallel portions of the wiring conductor on the surface of the insulating layer and electrically independent from the wiring conductor.

  According to the wiring board of the present invention, the insulating layer sandwiched between the parallel portions of the wiring conductor having a plurality of bent portions at least partially and provided with parallel portions parallel to each other by the plurality of bent portions. Since a conductive layer electrically independent from the wiring conductor is formed on the surface, even when a high-frequency signal of, for example, 10 GHz or more is propagated to the wiring conductor in which the parallel portion is formed, A conductor layer formed inside acts as an electromagnetic barrier, and as a result, signals do not jump over the parallel parts of the wiring conductor and propagate to multiple signal wiring conductors. Can be successfully propagated at the same timing, and the mounted electronic component can be operated normally.

  Next, the wiring board of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a cross-sectional view showing an example in which the best mode for carrying out the wiring board of the present invention is applied to a wiring board for mounting a semiconductor element. Is a wiring conductor, and 3 is a semiconductor element.

  The insulating substrate 1 is made of, for example, an epoxy resin or bismaleimide triazine resin on the upper and lower surfaces of an insulating layer 1a formed by impregnating a glass fabric in which glass fibers are woven vertically and horizontally with a thermosetting resin such as epoxy resin or bismaleimide triazine resin. A plurality of insulating layers 1b made of thermosetting resin are laminated, and a mounting portion on which the semiconductor element 3 is mounted by flip chip connection is provided in the central region of the upper surface. A plurality of wiring conductors 2 made of a conductor layer such as a copper foil or a copper plating film are formed from the mounting portion to the lower surface.

  The insulating layer 1a constituting the insulating substrate 1 has a thickness of about 0.3 to 1.5 mm, and has a plurality of through holes 4 having a diameter of about 0.2 to 1.0 mm from the upper surface to the lower surface. . A conductive layer 2a made of copper foil as a part of the wiring conductor 2 is formed on the upper and lower surfaces, and a through conductor 2b made of a copper plating film as a part of the wiring conductor 2 is attached to the inner surface of each through-hole 4. The upper and lower conductor layers 2 a are electrically connected via the through conductor 2 b in the through hole 4.

  Such an insulating layer 1a is manufactured by thermally curing a sheet in which a glass fabric is impregnated with an uncured thermosetting resin, and then drilling the sheet from the upper surface to the lower surface. In addition, the conductor layer 2a on the upper and lower surfaces of the insulating layer 1a has a copper foil having a thickness of about 5 to 50 μm adhered to the entire upper and lower surfaces of the sheet for the insulating layer 1a, and this copper foil is etched after the sheet is cured. By doing so, a predetermined pattern is formed. Further, in the through conductor 2b on the inner surface of the through hole 4, after the through hole 4 is provided in the insulating layer 1a, a copper plating film having a thickness of about 5 to 50 μm is formed on the inner surface of the through hole 4 by an electroless plating method and an electrolytic plating method. Formed by precipitation.

  Further, the insulating layer 1a is filled with a resin column 5 made of a thermosetting resin such as an epoxy resin or a bismaleimide triazine resin in the through hole 4 thereof. The resin pillar 5 is for allowing the insulating layer 1b and the wiring conductor 2 to be formed immediately above and below the through hole 4 by closing the through hole 4, and penetrates the uncured paste-like thermosetting resin. The holes 4 are formed by filling the holes 4 by a screen printing method, thermally curing them, and then polishing the upper and lower surfaces thereof in a substantially flat manner. And the insulating layer 1b is laminated | stacked on the upper and lower surfaces of the insulating layer 1a containing this resin pillar 5. FIG.

  The insulating layer 1b laminated on the upper and lower surfaces of the insulating layer 1a has a plurality of through holes 6 each having a thickness of about 20 to 50 μm and a diameter of about 30 to 100 μm from the upper surface to the lower surface of each layer. These insulating layers 1b are for providing an insulating interval for wiring the wiring conductors 2 at high density, and the insulating layer 1b is formed of a copper plating film as a part of the wiring conductors 2 on the surface thereof. A through conductor 2 d made of a copper plating filler as a part of the wiring conductor 2 is deposited in the conductor layer 2 c and the through hole 6. The upper conductor layer 2c and the lower conductor layers 2a and 2c are electrically connected through the through conductors 2d in the through holes 6 so that high-density wiring can be formed in three dimensions.

  In such an insulating layer 1b, an uncured thermosetting resin film having a thickness of about 20 to 50 μm is stuck on the upper and lower surfaces of the insulating layer 1a, and this is thermoset and the through hole 6 is drilled by laser processing. Further, it is formed by sequentially stacking the next insulating layer 1b in the same manner. The conductor layer 2c deposited on the surface of each insulating layer 1b and the through conductor 2d deposited in the via hole 6 are formed on the surface of each insulating layer 1b and in the through hole 6 every time each insulating layer 1b is formed. A copper plating film having a thickness of about 5 to 50 μm is deposited on a predetermined pattern by a pattern forming method such as a known semi-additive method or subtractive method.

  Further, a solder resist layer 7 is deposited on the outermost insulating layer 1b. The solder resist layer 7 is made of, for example, an insulating material in which an inorganic powder filler such as silica or talc is dispersed in an acrylic-modified epoxy resin in an amount of about 30 to 70% by mass, and improves the electrical insulation reliability between the wiring conductors 2 on the surface layer. The function is to increase the bonding strength of the connection pads 2e and 2f described later to the insulating substrate 1.

  Such a solder resist layer 7 has a thickness of about 10 to 50 μm, and an uncured resin paste for the solder resist layer 7 having photosensitivity is applied to the outermost insulating layer by using a roll coater method or a screen printing method. It is formed by coating on 1b and drying it, and then exposing and developing to form openings that expose the connection pads 2e and 2f, and then thermally curing them. Alternatively, after an uncured resin film for the solder resist layer 7 is stuck on the uppermost insulating layer 1b, it is thermally cured, and then irradiated with laser light at positions corresponding to the connection pads 2e and 2f. Then, the cured resin film is partially removed to form openings that expose the connection pads 2e and 2f.

  The wiring conductor 2 formed from the mounting portion of the insulating substrate 1 to the lower surface is functionalized into wiring conductors for signals, grounds, and power supplies depending on applications. Among these, the signal wiring conductor 2 functions as a conductive path for propagating an electric signal between the electrode of the semiconductor element 3 and the external electric circuit board, and as shown in a plan view of the main part in FIG. A part of the insulating substrate 1 has a plurality of thin line-shaped wiring conductors 2cs extending from the central region toward the outer peripheral region with a plurality of bent portions. Since a part of the wiring conductor 2cs has a plurality of bent portions and is formed to be folded in this way, the signal propagation delay time in the plurality of signal wiring conductors 2 is converted into the length of the wiring. And approximately the same. In this case, the wiring conductor 2cs is provided with parallel portions parallel to each other by a plurality of bent portions.

  Further, the wiring conductor 2 for grounding and power supply has a function as a supply path for supplying the ground potential and the power supply potential to the semiconductor element 3 mounted on the wiring board, respectively, and also has a wiring conductor for signals. 2 has an electromagnetic shielding function and a characteristic impedance adjusting function, and has a large-area conductor layer disposed so as to face the signal wiring conductor 2 with the insulating layer 1b interposed therebetween. Thus, by arranging the conductor layer having a large area for grounding or power supply so as to face the signal wiring conductor 2, the signal wiring conductor 2 is electromagnetically shielded and has a predetermined characteristic impedance. Adjusted.

  In addition, as shown in FIG. 1, these wiring conductors 2 are connected to electronic parts in which the portions exposed to the mounting portion of the insulating substrate 1 are electrically connected to each electrode of the semiconductor element 3 through solder 8. The connection pad 2e is connected to the external electric circuit board via the solder 9 at a portion exposed on the lower surface of the insulating base 1 to form a connection pad 2f for external connection. These connection pads 2 e and 2 f are arranged in a lattice pattern on the mounting portion and the lower surface of the insulating substrate 1, and the electrodes of the semiconductor element 3 and the connection pads 2 e are electrically connected via the solder 8. The semiconductor element 3 becomes a semiconductor device mounted on the mounting portion of the insulating substrate 1 by flip chip connection. By connecting the connection pads 2f in this semiconductor device to the wiring conductor of the external electric circuit board via the solder 9, the semiconductor element 3 Is electrically connected to the external electric circuit board. In the semiconductor device of this example, an example in which a protective resin 10 called an underfill is filled between the mounting portion of the insulating substrate 1 and the semiconductor element 3 is shown. After the semiconductor element 3 is mounted on the mounting portion of the insulating substrate 1 via the solder 8 by flip chip connection, the protective resin 10 is injected with an uncured thermosetting resin paste between the insulating substrate 1 and the semiconductor element 3. At the same time, the paste is filled by thermosetting. In order to mount the semiconductor element 3 on the mounting portion of the insulating substrate 1 by flip chip connection via the solder 8, a solder paste containing solder powder and flux is used for the connection pad 2e by a conventionally known screen printing method. The solder 8 is preliminarily formed on the connection pad 2e by heating it at a temperature of 220 to 260 ° C. to melt the solder powder, and the solder 8 and the electrode of the semiconductor element 3 A method of melting the solder 8 in the contacted state is employed.

  Further, in the wiring board of the present invention, as shown in FIG. 2, a conductor electrically independent of the wiring conductor 2cs is formed on the surface of the insulating layer 1b sandwiched inside the parallel portion of the signal wiring conductor 2cs. Layer 11 is formed. The conductor layer 11 is made of the same material as that of the wiring conductor 2cs, and is formed by the same method at the same time when the wiring conductor 2cs is formed. Thus, since the conductor layer 11 that is electrically independent of the wiring conductor 2cs is formed on the surface of the insulating layer 1b sandwiched between the parallel portions of the wiring conductor 2cs, the conductor layer 11 is connected to the wiring conductor 2cs. 2 cs acts as an electromagnetic barrier inside the parallel portion of 2cs, and as a result, even if a high-frequency signal exceeding 10 GHz is propagated to the wiring conductor 2cs, the signal propagates across the parallel portions of the wiring conductor 2cs. As a result, the signal propagation delay time in the plurality of signal wiring conductors 2 is made substantially the same to propagate the signal at the same timing, and the mounted semiconductor element can be operated normally.

  When the conductor layer 11 formed between the parallel portions of the signal wiring conductor 2cs is electrically connected to the wiring conductor 2 for grounding or power supply, the conductor layer 11 is 10 GHz or more to the wiring conductor 2cs. When a high frequency signal is propagated, it is possible to effectively prevent the resonance of the high frequency in the conductor layer 11 and to efficiently propagate the high frequency signal to the signal wiring conductor 2cs. Accordingly, it is preferable that the conductor layer 11 formed between the parallel portions of the signal wiring conductor 2cs is electrically connected to the grounding or power supply wiring conductor 2.

  Further, the conductor layer 11 formed between the parallel portions of the signal wiring conductor 2cs has a length less than a quarter of the wavelength of the signal propagating through the signal wiring conductor 2cs. The influence of the mismatch of characteristic impedance in the parallel portion of the wiring conductor 2cs is reduced, and a high-frequency signal can be propagated to the signal wiring conductor 2cs extremely efficiently. Accordingly, the length of the conductor layer 11 formed between the parallel portions of the signal wiring conductor 2cs is less than a quarter of the wavelength of the signal propagating through the signal wiring conductor 2cs. Is preferred.

  The wiring board of the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications can be made without departing from the gist of the present invention.

It is sectional drawing which shows the example of the best form for implementing the wiring board of this invention. It is a principal part enlarged plan view of the wiring board shown in FIG.

Explanation of symbols

1b: insulating layer 2cs: wiring conductor 11: conductor layer

Claims (1)

A linear wiring conductor formed on the surface of the insulating layer and having a plurality of bent portions at least in part and provided with parallel portions parallel to each other by the plurality of bent portions, and the surface of the insulating layer A wiring board comprising: a conductive layer electrically sandwiched between the wiring conductors and formed between the parallel portions of the wiring conductors.

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