KR101376391B1 - Multilayer printed wiring board and double-sided printed wiring board - Google Patents

Abstract

Even if an insulating layer containing a glass woven fabric or a glass nonwoven fabric is used, a thin printed wiring board that can maintain the rigidity of the printed wiring board in the heat treatment process at the time of component mounting and can prevent migration by CAF is provided.
A printed wiring board provided with an insulation reinforcing layer containing a thermosetting resin having a minimum melt viscosity of at least 2000 Pa · s at an interface between an insulating substrate including a wiring circuit and an insulating layer.

Description

MULTILAYER PRINTED WIRING BOARD AND DOUBLE-SIDED PRINTED WIRING BOARD}

The present invention relates to a multilayer printed wiring board and a double-sided printed wiring board capable of maintaining rigidity and preventing generation of migration due to CAF even if the thickness of the interlayer insulating layer is reduced.

In recent years, even in the technical field of printed wiring boards, the flow of light and short is reduced in correspondence with mobile phones, mobile devices, or small electronic devices, which are end products, and thinner, higher density of wiring, and higher multilayers are required.

In order to reduce the thickness of the printed wiring board, there are various methods. In particular, in the multilayer printed wiring board, a wiring board capable of withstanding the stiffness in the thermal history at the time of component mounting to some extent is desired even if the thickness of the board is thin.

Basically, multilayer printed wiring boards are made of multilayer printed wiring boards by alternately stacking conductor layers and insulating layers. However, even when the thickness of the multilayer printed wiring boards is thin, the multilayer printed wiring board can withstand the heat during component mounting, and is called a 'bending' or 'warping'. As one of the methods which does not produce | generate, the method of strengthening rigidity using the "prepreg" which impregnated the thermosetting resin in the glass woven fabric or the glass nonwoven fabric is mentioned.

In the present situation, the thickness of the 'prepreg' has a thickness of 30 μm or less, but since the glass fiber diameter is not different from the previous one, the adjustment of the thickness of the 'prepreg' is the resin of the epoxy resin impregnated. It is done in quantity.

As a result, the thinning of the 'prepreg' means that the resin amount impregnated in the 'prepreg' is reduced because the thickness is adjusted by the amount of the resin impregnated in the 'prepreg' as described above. Therefore, in the case of a multilayer printed wiring board, it is only possible to fill the adjacent conductor layer, that is, the irregularities of the wiring circuit with resin, and it was difficult to completely prevent the long fibers of the glass woven or glass nonwoven fabric from contacting the wiring circuit with the resin. . As a result, when a glass cloth or a glass nonwoven fabric is in contact with the wiring circuit, for example, a problem arises in which a CAF (conductive anodic filament) occurs along the glass fiber depending on the use of the multilayer printed wiring board. there was. On the other hand, taking into account the stiffness, warpage and warping caused by the heat during component mounting, eliminating long fibers made of glass or glass nonwovens is virtually difficult because warpage and warpage tend to occur. There was a problem.

In addition, a technique of providing an insulating film of about 10 μm so as to suppress the migration occurring between the glass fiber base material and the wiring layer and improve the adhesion of the wiring pattern even when used at high voltage has been reported (for example, See Patent Document 1).

However, even if an insulating film is provided between the glass fiber base material and the wiring layer, the resin and insulating film impregnated with the glass fiber in the manufacturing process of the printed wiring board will melt both resins due to the heat and pressure of the laminating process (resin and insulating film At the same time, when the film thickness of the insulating film is thin, there is a problem that the glass fiber contacts the wiring layer.

[Patent Document 1] Japanese Patent Application Laid-Open No. 2001-244589

In view of the above problems, the present invention maintains the rigidity of the printed wiring board in the heat treatment step at the time of component mounting, even if an insulating layer containing a glass woven fabric or a glass nonwoven fabric is used as the insulating layer of the multilayer printed wiring board. It is an object of the present invention to provide a thin multilayer printed wiring board and a double-sided printed wiring board which can prevent migration caused by migration.

In the present invention, an insulating layer containing a glass woven fabric or a glass nonwoven fabric is disposed on an interlayer insulating layer of a multilayer printed wiring board, and at least an insulation reinforcing layer is provided at an interface between the insulating base including the wiring circuit and the insulating layer, Moreover, the said subject was solved by the multilayer printed wiring board which the said insulation reinforcement layer consists of a thermosetting resin which has a minimum melt viscosity of 2000 Pa * s or more.

That is, by providing an insulation reinforcement layer on the base material including a wiring circuit, it becomes possible to prevent the long fiber of a glass woven fabric or a glass nonwoven fabric from directly contacting a wiring circuit. In addition, since the insulation reinforcing layer has a minimum melt viscosity of 2000 Pa · s or more, the film is not melted with respect to heat during the lamination process and thus maintains the shape of the film, thereby preventing the glass woven or glass nonwoven fabric from directly contacting the wiring circuit. can do. In addition, since the minimum melt viscosity of the epoxy resin impregnated into the insulating layer (usually used insulating layer) is around 800 Pa · s, when the minimum melt viscosity of the insulation reinforcing layer is less than 2000 Pa · s, the minimum melt viscosity of the insulating layer As a result, the difference is reduced, and as a result, the insulation reinforcement layer cannot maintain the shape of the film, and the possibility of contact between the wiring circuit and the long fibers of the glass woven or glass nonwoven fabric is increased.

In particular, it is preferable that the thermosetting resin of the said insulation reinforcement layer has the elasticity modulus lower than the elasticity modulus of the epoxy resin impregnated into the insulating layer containing a glass woven fabric or a glass nonwoven fabric.

That is, since the insulation reinforcement layer becomes soft and elastic by lowering the elastic modulus of the thermosetting resin of the insulation reinforcement layer than that of the epoxy resin of the insulation layer, even if the thickness of the insulation reinforcement layer is considerably thinner ( For example, the effect which can endure reliability test, such as about 1 micrometer) cold-heat cycle test, is exhibited. That is, in the case of performing a cold cycle test (1000 cycles at a high temperature of 125 ° C. (30 minutes) and a low temperature of −65 ° C. (30 minutes) as one cycle), numerous cracks are generated in the insulating layer (prepreg), but the insulation reinforcing layer As a result, the cracks can be prevented from advancing to the wiring circuit surface, and as a result, migration caused by moisture entering the cracks can be prevented.

Moreover, it is preferable that especially the wiring circuit of the said multilayer printed wiring board, and the glass woven fabric or glass nonwoven fabric contained in an insulating layer are separated by the said resin reinforced layer and the resin impregnated into the said insulating layer.

That is, since the insulation reinforcement layer and the resin impregnated in the said insulating layer are interposed between a wiring circuit and an insulating layer, it becomes possible to completely prevent a glass woven fabric or a glass nonwoven fabric from contacting a wiring circuit.

In particular, as the multilayer flint wiring board, an insulating layer including a glass woven fabric or a glass nonwoven fabric as a solder resist is disposed on the outermost layer thereof, and at least at the interface between the insulating substrate including the outer layer wiring circuit and the insulating layer. It is preferable that a layer is provided.

That is, by using the insulating layer containing a glass woven fabric or a glass nonwoven fabric also as a soldering resist, it can suppress the "bending" and "twisting" of the multilayer printed wiring board aimed at thinning, preventing migration by CAF.

In particular, the multilayer printed wiring board includes a through plating through hole and / or a blind via hole, and an insulation reinforcement layer is formed on the inner wall of the conductor of the through plating through hole and the blind via hole. It is preferable that it is provided.

In other words, the resin-impregnated layer is interposed between the conductive inner wall of the through plating through hole and the blind via hole, and the glass woven fabric or the glass nonwoven fabric, so that the glass woven fabric or the glass nonwoven fabric is in contact with the inner wall of the conductor. It is possible to completely prevent that.

In addition, the present invention provides an insulating substrate including a wiring circuit provided on the front and back of the insulating substrate, wherein an insulating layer containing a glass woven fabric or a glass nonwoven fabric is disposed as a solder resist on the wiring circuit provided on the front and rear of the insulated substrate. The said subject is solved by the double-sided printed wiring board which consists of a thermosetting resin in which the insulation reinforcement layer is provided at least at the interface of an insulation layer, and the said insulation reinforcement layer has a minimum melt viscosity of 2000 Pa * s or more.

That is, by using the insulating layer containing a glass woven fabric or a glass nonwoven fabric as a soldering resist, it can suppress the "bending" and "twisting" of the double-sided printed wiring board which aimed at thinning, preventing migration by CAF.

In particular, it is preferable that the thermosetting resin of the insulation reinforcement layer of the said double-sided printed wiring board is lower than the elasticity modulus of the epoxy resin impregnated into the insulating layer containing a glass woven fabric or a glass nonwoven fabric.

That is, since the insulating reinforcing layer becomes soft and elastic by lowering the thermosetting resin elastic modulus of the insulating reinforcing layer than that of the epoxy resin of the insulating layer, even if the thickness of the insulating reinforcing layer is considerably thin (eg For example, about 1 micrometer) The effect which can endure reliability tests, such as a cold-heat cycle test, is exhibited. That is, in the case of performing a cold cycle test (1000 cycles at a high temperature of 125 ° C. (30 minutes) and a low temperature of −65 ° C. (30 minutes) as one cycle), numerous cracks are generated in the insulating layer (prepreg), but the insulation reinforcing layer As a result, the cracks can be prevented from advancing to the wiring circuit surface, and as a result, migration caused by moisture entering the cracks can be prevented.

In particular, it is preferable that the double-sided printed wiring board is provided with a through plating through hole and / or a blind via hole, and an insulation reinforcing layer is also provided on the inner walls of the conductors of the through plating through hole and the blind via hole.

In other words, the resin-impregnated layer is interposed between the conductive inner wall of the through plating through hole and the blind via hole, and the glass woven fabric or the glass nonwoven fabric, so that the glass woven fabric or the glass nonwoven fabric is in contact with the inner wall of the conductor. It becomes possible to suppress the thing completely.

In the present invention, since the insulating layer containing the glass woven fabric or the glass nonwoven fabric is disposed in the interlayer insulating layer or the solder resist, the warping and warping in the heat treatment process at the time of mounting the component includes the glass woven fabric or the glass nonwoven fabric. Since the insulation reinforcement layer is disposed on the substrate including the wiring circuit while suppressing contact with the insulating layer, the plate thickness prevents contact between the wiring circuit and the glass woven or glass nonwoven fabric and prevents migration by CAF. It is possible to provide a wired multilayer printed wiring board and a double-sided printed wiring board.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic sectional explanatory drawing of the six-layer through board | substrate which shows 1st Embodiment of this invention.
It is a schematic sectional explanatory drawing of the four-layer buildup board | substrate which shows 2nd Embodiment of this invention.
3 is a schematic cross-sectional explanatory diagram of a double-sided printed wiring board showing a third embodiment of the present invention.
It is a schematic sectional explanatory drawing of the double-sided printed wiring board before soldering resist formation in 3rd Embodiment of this invention.

First, in the first embodiment of the present invention, Fig. 1 shows a multilayer printed wiring board using a so-called 'prepreg' containing a glass woven or nonwoven fabric as an interlayer insulating layer of a 'six-layer through multilayer printed wiring board'. It demonstrates based on.

As shown in FIG. 1, the six-layer through substrate P has the insulating layers 1a to 1d disposed above and below the double-sided core substrate 11, and the inner layer wiring circuits 2a to 2d, respectively. The glass woven fabric or the glass nonwoven fabric 4 in which the insulation reinforcement layers 3a-3d are provided and contained in the insulation layers 1a-1d is in the insulation reinforcement layers 3a-3d and the insulation layers 1a-1d. The resin has a structure that is protected so as not to contact the inner layer wiring circuits 2a to 2d. In addition, the outermost wiring circuit 5 is formed in the outermost layer, and a through plating through hole 6 for connecting the inside and the outside of the six-layer through substrate P is formed.

Here, as the insulating layers 1a to 1d, for example, an insulating layer having a thickness of 25 μm to 35 μm impregnated with an epoxy resin can be used. When the thickness of the insulating layers 1a to 1d becomes thin and the amount of resin contained in the insulating layer decreases, the effect of using the insulating reinforcement layer is further exerted. In the future, it is also possible to use an insulating layer having a thickness of 15 µm to 20 µm. In addition, if the thickness of the insulating layer is 40 µm or more, the amount of resin impregnated in the glass woven fabric or the like is large, so that there is no fear that the original wiring circuit and the glass woven fabric are in contact with each other, and the thickness of the insulating layer is thick. Thinning of the multilayer printed wiring board and the double-sided printed wiring board, which is also possible, cannot be achieved.

In addition, as the insulation reinforcing layers 3a to 3d, for example, epoxy resins and elastomers ('elastomers' are synthetic polymers such as silicone rubber, etc., and have an effect of imparting elasticity to resins such as epoxy). The thermosetting resin (for example, "primer resin" by Mitsui Kinzoku Co., Ltd.) etc. which are formed are used suitably. In particular, if the insulation reinforcement layers 3a to 3d have a minimum melt viscosity of 2000 Pa · s or more, even if the resin of the insulation layers 1a to 1d flows while being softened by heating and pressure in the lamination press step, the insulation reinforcement layer (3a-3d) can maintain the shape of a film | membrane at the minimum melt viscosity of the said thermosetting resin, and can prevent the glass woven fabric or the glass nonwoven fabric 4 from directly contacting an inner layer wiring circuit. In addition, since the minimum melt viscosity of the epoxy resin impregnated into the insulating layer (usually used insulating layer) is around 800 Pa · s, when the minimum melt viscosity of the insulation reinforcing layer is less than 2000 Pa · s, the minimum melt viscosity of the insulating layer As a result, the difference is reduced, and as a result, the insulation reinforcement layer cannot maintain the shape of the film, and the possibility of contact between the wiring circuit and the long fibers of the glass woven or glass nonwoven fabric is increased.

This means that in the case of the insulation reinforcement layer having a minimum melt viscosity of 1500 Pa · s, the shape of the film could not be maintained during the lamination step, but the insulation had a minimum melt viscosity of 10000 Pa · s, 20000 Pa · s, 30000 Pa · s, and 100,000 Pa · s. In the case of the reinforcement layer, all have been confirmed by the experimental result that the shape of the film of the insulation reinforcement layer was maintained without a problem after the lamination step. Therefore, in this invention, it is essential that the minimum melt viscosity of an insulation reinforcement layer is 2000 Pa * s or more.

As the elastic modulus of the thermosetting resins of the insulation reinforcing layers 3a to 3d, those having a lower elastic modulus than the epoxy resins of the insulating layers 1a to 1d, in particular those having an elastic modulus of 3 GPa or less, for example, are about 1 μm. Insulation reinforcement can prevent the crack from entering even if the thermosetting resin contained in an insulation reinforcement layer becomes thin by repeating the high temperature and low temperature test, such as a cold-heat cycle test which is a reliability test, for a thickness of an insulation reinforcement layer. Since the layer is in a state of soft elasticity, it is preferable because the effect to withstand reliability tests such as a cold heat cycle test is exhibited even if the thickness of the insulating reinforcement layer is as thin as possible.

In addition, by making the minimum melt viscosity of the insulation reinforcing layers 3a to 3d higher than the insulating layers 1a to 1d, it is possible to make the film thickness of the insulation reinforcing layers 3a to 3d thinner by a synergistic effect with the elastic modulus. (Increasing the thickness of the insulating reinforcement layer can prevent cracks from entering the cold-heat cycle test).

Therefore, thinning the thickness of the insulation reinforcing layers 3a to 3d also contributes to thinning the thickness of the multilayer printed wiring board (six-layer through substrate P), which is also a subject of the present invention. The thickness of the present insulating layers 1a to 1d is mainly 25 μm to 35 μm, but in the future, an insulating layer having a thickness of 15 μm to 20 μm may be used. In addition, it has been confirmed by the experiment that the thickness of an insulation reinforcement layer can fully exhibit an effect even about thickness of about 1 micrometer, for example.

It is preferable that there is no insulation reinforcing layers 3a to 3d if it is merely for the purpose of thinning, but the thickness of the printed wiring board is reduced by using a substrate containing the glass woven fabric or the glass nonwoven fabric 4 in the insulating layers 1a to 1d. In order to achieve this, the insulation reinforcing layers 3a to 3d are essential in maintaining rigidity against warpage and warping of printed wiring boards and preventing migration by CAF due to heat during component mounting. .

Next, about the 2nd Embodiment of this invention, FIG. 2 which shows a multilayer printed wiring board using what is called a "prepreg" containing a glass woven fabric or a glass nonwoven fabric in an insulating layer as an interlayer insulation layer of a "four-layer buildup board." It demonstrates based on.

As shown in FIG. 2, the four-layer build-up substrate S is formed with an insulation reinforcement layer 13 formed on the inner layer wiring circuit 12 formed on the double-sided core substrate 11 and insulated from above and below. The layer 14 is disposed, and the glass woven fabric or the glass nonwoven fabric 15 included in the insulating layer 14 is formed of the inner layer wiring circuit 12 by the resin in the insulating reinforcing layer 13 and the insulating layer 14. The structure is protected so that it does not come into contact with it. In the insulating layer 14, the blind via hole 16 is provided with copper plating, including a hole, and a through plating through hole 17 which connects the inside and the outside of the four-layer build-up substrate S. ) Is formed.

As the insulation reinforcement layer 13, the same materials as those of the insulation reinforcement layers 3a to 3d in the first embodiment, those having the lowest melt viscosity and elastic modulus are used.

In addition, as the insulating layer 14, the thing of the same material and thickness as the insulating layers 1a-1d in the said 1st Embodiment is used.

Next, the 3rd Embodiment of this invention is demonstrated based on FIG. 3 which shows the double-sided printed wiring board using the so-called "prepreg" in which an insulating layer contains a glass woven fabric or a glass nonwoven fabric as a soldering resist of a "duplex board." do.

As shown in FIG. 3, the double-sided printed wiring board T includes the double-sided wiring circuit 27, the through-plated through-hole 25, and the blind via-hole 26 having the double-sided printed circuit board 21. An insulating reinforcement layer 28 is formed on the surface of the circuit 27, the through plating through hole 25, and the blind via hole 26, and an insulating layer 22 is disposed above and below as a solder resist. The glass woven fabric or the glass nonwoven fabric 23 included in the insulating layer 22 is formed by the resin in the insulating reinforcing layer 28 and the insulating layer 22, the double-sided wiring circuit 27, the through plating through hole 25, and the blinds. The structure is protected so as not to contact the via hole 26. In addition, an opening is appropriately formed in the insulating layer 22, and a component mounting pad 24 is formed.

In the case of using the so-called 'prepreg', which is the insulating layer 22, as the solder resist of the double-sided printed board 21 having the through plating through hole 25 and the blind via hole 26, as shown in FIG. Similarly, the insulating layer 22 is formed on the double-sided printed circuit board 21 having the insulating reinforcing layer 28 formed to cover the opening of the through plating through hole 25 and the blind via hole 26 together with the double-sided wiring circuit 27. ), The resin in the insulating layer 22 also flows in the through plating through hole 25 and the blind via hole 26, so that the through plating through hole 25 and the blind are shown in FIG. The insulation reinforcement layer 28 is also formed on the conductor inner wall of the via hole 26.

Here, as the insulation reinforcement layer 28 and the insulation layer 22, the same thing as the insulation reinforcement layers 3a-3d and the insulation layers 1a-1d in the said 1st Embodiment is used. In particular, when the modulus of elasticity of the insulating reinforcing layer 28 is 3 GPa or less, the insulating reinforcing layer 28 is more reliably followed on the inner walls of the conductors of the through plating through hole 25 and the blind via hole 26. When this insulation reinforcement layer 28 is formed in the conductor inner wall of the through-plating through-hole 25 and the blind via-hole 26, it has also been confirmed by experiment that no void was formed. In addition, biting the voids may cause the voids to expand and through-hole punctures, for example, when voids are formed due to heat or the like during component mounting.

The second insulation reinforcing layer 28 prevents migration by CAF as the surface of the wiring circuit in the XY direction, and suppresses the through hole puncture by pressing voids with respect to the interlayer connection in the Z direction such as through plating through holes. The effect is also confirmed.

On the other hand, in 1st and 2nd embodiment, although the arrangement | positioning of the soldering resist of the outermost layer was not demonstrated, so-called "prepreg" which contains a glass woven fabric or a glass nonwoven fabric in an insulating layer like 3rd embodiment, soldering resist Needless to say, it does not matter if it is arranged as.

1a, 1b, 1c, 1d, 14, 22: insulating layer
2a, 2b, 2c, 2d, 12: inner layer wiring circuit
3a, 3b, 3c, 3d, 13, 28: insulation reinforcement layer
4, 15, 23: glass woven or glass nonwoven
5: outer layer wiring circuit
6, 17, 25: Through plated through hole
11: double sided core substrate
16: blind via hole (copper plating is filled in the hole)
21: duplex printed circuit board
24: component mounting pad
26: blind buyer hall
27: double-sided wiring circuit
P: 6-layer through board
S: 4-layer buildup board
T: Duplex printed wiring board

Claims (9)

The insulating layer containing glass woven fabric or glass nonwoven fabric is arrange | positioned at the interlayer insulation layer of a multilayer printed wiring board, At least an insulation reinforcement layer is provided in the interface of the insulation base containing a wiring circuit, and the said insulation layer, and the said insulation The reinforcement layer has a minimum melt viscosity of 2000 Pa · s or more, and is made of a thermosetting resin having an elastic modulus of 3 Gpa or less. The multilayer printed wiring board according to claim 1, wherein the elastic modulus of the thermosetting resin of the insulation reinforcing layer is lower than the elastic modulus of the epoxy resin impregnated into the insulating layer containing the glass woven fabric or the glass nonwoven fabric. The multilayer printed wiring board according to claim 1, wherein the wiring circuit and the glass woven fabric or the glass nonwoven fabric included in the insulating layer are separated by the resin impregnated in the insulating reinforcing layer and the insulating layer. The multilayer printed wiring board according to claim 1, wherein the interlayer connection of the multilayer printed wiring board is a through plating through hole or a blind via hole. The insulating base material according to any one of claims 1 to 4, wherein an insulating layer including a glass woven fabric or a glass nonwoven fabric as a solder resist is disposed on the outermost layer of the multilayer printed wiring board, and an outer layer wiring circuit; At least the insulation reinforcement layer is provided in the interface of the said insulating layer, The multilayer printed wiring board characterized by the above-mentioned. The multilayer printed wiring board according to claim 4, wherein an insulation reinforcement layer is also provided on the inner wall of the conductor of the through-plated through hole or the blind via hole. An insulating layer containing a glass woven fabric or a glass nonwoven fabric is disposed as a solder resist on a wiring circuit provided on the front and back of the insulated substrate, and at least at an interface between the insulating substrate including the wiring circuit provided on the front and back of the insulated substrate and the insulating layer. A double-sided printed wiring board comprising an insulating reinforcing layer, wherein the insulating reinforcing layer has a minimum melt viscosity of 2000 Pa · s or more and a thermosetting resin having an elastic modulus of 3 Gpa or less. The double-sided printed wiring board according to claim 7, wherein the elastic modulus of the thermosetting resin of the insulation reinforcing layer is lower than the elastic modulus of the epoxy resin impregnated into the insulating layer containing the glass woven fabric or the glass nonwoven fabric. The said double-sided printed wiring board is provided with the through plating through hole or the blind via hole, and the insulation reinforcement layer is provided also in the conductor inner wall of the through plating through hole or the blind via hole. Duplex printed wiring board.

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