JPH11140280A - Paste for filling through hole and printed circuit board using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a paste for filling a through hole, hardly causing peeling, etc., of a copper-plated layer from a hardened body formed in a filling step, and suppressing the generation, etc., of crack at a built-up layer, and further to provide a printed circuit board using the same. SOLUTION: This paste for filling a through hole comprises a metallic filler and an epoxy resin composition. The metallic filler has a spherical shape and is a copper powder, etc., having 0.5-20 μm average particle diameter. Especially, the copper powder subjected to a blackening treatment is preferable. The epoxy resin comprises 70-99 pts.wt. phenol novolak type epoxy resin and 1-30 pts.wt. bisphenol A type and bisphenol F type epoxy resin, and the epoxy resin composition is obtained by adding a hardening agent such as the imidazole-based one to the epoxy resin. Preferably, the heating temperature at a filling step is 120-170 deg.C and the heating temperature at a solder reflow step is 230-280 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paste for filling a through hole which is used to fill a through hole provided in a printed wiring board, and a printed wiring board using the same. The paste of the present invention is useful in dense printed wiring boards, especially in multilayer printed wiring boards,
It can be used in various information communication printed wiring boards exposed to severe use conditions, such as a U IC package.

[0002]

2. Description of the Related Art In recent years, for the purpose of improving the performance of electronic devices, various studies have been made on a printed wiring board, such as increasing the density of wiring using a photo process or increasing the number of layers by a build-up method. However, in a conventional printed wiring board, a through-hole is opened on the surface thereof, and no wiring can be formed on the through-hole. Therefore, avoiding through holes and routing wiring,
There are restrictions on the design, which hinders the increase in the density or the number of layers of the target wiring.

Therefore, recently, a resin paste has been filled in the through-hole, and wiring has been provided on the through-hole.
A method of building up an insulating layer to achieve high density or multilayer wiring has been developed and is receiving attention. Fillers are added to this paste to suppress thermal shrinkage during curing, and inorganic fillers such as silica are generally used (JP-A-2-284951, etc.). Further, a copper plating layer is formed on a wall surface of a through hole or the like in order to establish conduction between the front and back surfaces of the substrate (Japanese Patent Application Laid-Open No. H5-205).
No. 28919). When wiring is performed by an additive method on a printed circuit board having such a structure and an insulating layer is built up, a via hole cannot be formed on a through hole, and as shown in FIG. There must be.

[0004]

However, there is an increasing demand for higher density or multi-layer printed wiring boards, and it is also necessary to form via holes on through holes. For that purpose, it is necessary to form a copper plating layer also on the through hole. However, the conventional paste in which an inorganic filler such as silica is added to the resin has poor adhesion between the cured product generated in the filling process and the copper plating layer formed on the through-hole, and as shown in FIG. However, there are problems such as peeling off from the cured body or swelling of a part of the cured body to form a gap between the surface of the cured body and the copper plating layer. Further, the adhesion between the resin and the inorganic filler is insufficient, and air bubbles may be generated in the cured product itself.

On the other hand, a conductive paste obtained by adding a metal filler such as copper or silver to a resin (JP-A-8-31157, JP-A-7-14427, JP-B-8-2125)
No. 4) is also provided, and the use of this paste improves the adhesion between the cured body and the copper plating layer. However, the peeling and swelling of the copper plating layer on the through hole cannot be sufficiently suppressed, and a problem remains particularly in applications requiring high reliability in a severe use environment. In addition, the copper plating layer formed on the wall surface of the through hole and the cured body may be separated from each other to form a gap.

Further, due to the thermal shrinkage of the cured product in the solder reflow step, a tensile stress is generated in the build-up layer in the thickness direction, and a crack may be generated in the build-up layer. Further, depending on the composition of the paste and the like, the cured product generated in the solder reflow process becomes hard and brittle, and cracks may occur in the cured product itself.
Further, cracks may occur in the cured product in a heat cycle test or the like.

The present invention solves the above-mentioned conventional problems, and has excellent adhesion between a cured product of a paste generated in a hole filling step and a copper plating layer formed on a through-hole, and a copper plating layer It is an object of the present invention to provide a paste for filling through holes, which does not cause peeling or swelling, and a printed wiring board using the paste. Further, when the paste of the present invention is used, peeling between the copper plating layer formed on the wall surface of the through hole and the cured body, and generation of cracks in the build-up layer in the solder reflow step can be sufficiently suppressed. Therefore, this paste can be used especially for a printed wiring board in an application requiring high reliability in a severe use environment.

[0008]

The paste for filling a through hole according to the first invention is a paste for filling a through hole which is used to fill a through hole of a printed wiring board. It consists of a 20 μm metal filler, an epoxy resin composition composed of an epoxy resin and a curing agent, and when the epoxy resin composition is 100 parts by weight, the epoxy resin is 90 to 90 parts by weight.
99.5 parts by weight, the curing agent is 0.5 to 10 parts by weight, the metal filler is 500 to 1000 parts by weight, and the viscosity of the paste at 25 ° C. is 2
0000 poise or less, the volatile matter of the paste by heating in the filling process is 1.0% or less, and the first cured body generated by heating in the filling process is heated and cooled in the solder reflow process. The shrinkage ratio of the generated second cured body in the length direction of the through hole is 0.1% or less. The contraction rate is represented by the following equation. Shrinkage (%) = (1st in the length direction of through hole
Length of cured body-length of second cured body in length direction of through hole) / length of first cured body in length direction of through hole × 100

[0009] In the first invention, 2 of the above “paste”
The viscosity at 5 ° C. is “20,000 poise or less”,
In particular, 15,000 poise or less, and 10,000 to 50
It is preferably 0 poise. This viscosity is 20,000
If the poise is exceeded, the workability when filling the paste into the through holes is greatly reduced. The volatile content of the paste in the filling process is “1.0% or less”, particularly preferably 0.2% or less. If this volatile content exceeds 1.0%, the copper plating layer on the through-hole may peel off or swell in a reliability test or the like, and air bubbles may be generated in the “first cured body”. Further, the copper plating layer formed on the wall surface of the through hole and the first cured body may be separated, and a gap may be generated.

Further, when the shrinkage ratio of the above-mentioned "second cured product" generated in the solder reflow step exceeds 0.1%, after the cooling in the solder reflow step or in a reliability test or the like thereafter, the build-up is performed. Cracks may occur in the up layer. In order to suppress such peeling and swelling of the copper plating layer, gaps in the through holes, and cracks in the build-up layer, the first
According to the present invention, a metal filler is added to a resin that hardly shrinks during curing at a particularly high ratio, and this is used as a paste for filling through holes. Further, this paste does not require a volatile solvent or the like. Therefore, the amount of volatile components at the time of curing in the filling process is extremely small, thereby suppressing the generation of bubbles in the first cured product.

As the "metal filler", a filler made of powder such as copper, silver, and a mixture thereof can be used. When the average particle size of these metal powders is less than 0.5 μm, the adhesion between the first cured product and the copper plating layer is reduced. On the other hand, when the average particle size exceeds 20 μm, the first cured product and the copper plating layer may peel off, and the copper plating layer may swell. When the amount of the metal filler added is less than 500 parts by weight, the water absorption of the first cured product increases. Further, the shrinkage of the second cured body in the solder reflow step increases, and cracks occur in the build-up layer. On the other hand, when the addition amount exceeds 1000 parts by weight, the viscosity of the paste increases, and the workability at the time of filling the paste into the through holes decreases.

The average particle size of the metal powder is preferably 3 to 15 μm,
Furthermore, the range of 5 to 10 μm is preferable. The addition amount of the metal filler is particularly preferably in the range of 500 to 800 parts by weight. When the average particle size of the metal powder and the amount of the metal filler added are in this range, the peel strength between the first cured product and the copper plating layer is higher, and cracks are also generated in the build-up layer in the solder reflow process. Can be suppressed sufficiently.

As the metal filler, a filler made of copper powder having excellent affinity for copper plating is particularly preferable. In addition, copper powder has a spherical shape, a flake shape, a dendritic shape, etc.
There is no particular limitation as long as the viscosity at 25 ° C. of the obtained paste is 20,000 poise or less. However, in order to suppress the increase in the viscosity of the paste when added in large amounts,
It is preferable to use a filler whose spherical powder is at least half or more in amount. Further, it is more preferable to use a spherical copper powder soft-etched or a copper powder "blackened" as in the second invention. Due to this blackening treatment, a needle-like coating made of copper oxide is formed on the surface of the powder particles and roughened, and the adhesion between the resin and the copper powder is increased by the improvement of the anchor effect and the chemical affinity. . This suppresses the generation of bubbles in the first cured product, and improves the adhesion between the cured product and the copper plating layer.

Further, by treating the surface of the metal filler with a "silane coupling agent having an epoxy group" as in the third invention, the affinity between the epoxy resin and the metal filler can be increased. In particular, by using an epoxy silane having an epoxy group on the hydrophobic group side, the water absorption of the first cured product can be reduced.

Epoxy resins generally have less shrinkage during curing than other resins and are useful in pastes for filling through holes. In the first invention, the "epoxy resin composition" comprises an epoxy resin and a required amount of a curing agent. As the "curing agent", an acid anhydride or a catalyst-based one can be widely used. However, in order to reduce the viscosity of the paste and the water absorption of the first cured body, a catalyst system, for example, an imidazole-based curing agent is particularly preferable. The curing agent is used in an amount of 2 to 7 parts by weight, more preferably
It is preferable that the amount is about parts by weight.

In the fourth invention, the above-mentioned "phenol novolak type epoxy resin" has a smaller shrinkage at the time of curing and a relatively high Tg, and is useful in the application of a paste for filling through holes. However, in the paste composed of a phenol novolak type epoxy resin and a metal filler, the second cured product becomes hard and brittle, and there is a problem that cracks occur in the second cured product itself due to heat history such as a subsequent heat cycle. . Therefore, in the fourth invention, another type of epoxy resin having excellent flexibility is blended with the phenol novolak type epoxy resin. Thereby, the hardness of the second cured body is adjusted, and the occurrence of cracks in the cured body itself is suppressed.

As the epoxy resin having excellent flexibility, the above-mentioned "bisphenol A type epoxy resin" and the above "bisphenol F type epoxy resin" can be used. These bisphenol-type epoxy resins usually have a higher shrinkage ratio during curing and a lower Tg than phenol novolak-type epoxy resins. However, many have high flexibility, relatively low viscosity at room temperature, and low water absorption. Therefore, by blending a bisphenol-type epoxy resin with a phenol novolak-type epoxy resin, it is possible to obtain a paste having excellent workability for filling into through-holes and having appropriate hardness after curing in a solder reflow process. . The epoxy resin has sufficient heat resistance if its Tg is 125 ° C. or higher, particularly 130 ° C. or higher, and more preferably 140 ° C. or higher.

If the amount of the bisphenol type epoxy resin is less than 1 part by weight, the second cured product becomes too hard, and cracks may occur in the cured product itself. Further, the viscosity of the paste is high, and it is not easy to fill the through holes. On the other hand, if the amount exceeds 30 parts by weight, the shrinkage of the second cured product in the solder reflow step increases, and cracks may occur in the build-up layer. Further, the heat resistance of the epoxy resin also tends to decrease. This amount is preferably 5 to 25 parts by weight, particularly preferably 10 to 20 parts by weight. If the compounding amount is in this range, a paste that can be easily filled and has a small shrinkage ratio in the solder reflow step can be obtained.

When an epoxy resin is used as the resin component of the paste, as in the fifth invention, the heating temperature in the “filling step” is set to “120 to 170 ° C.”, and the heating temperature in the “solder reflow step” is set to “230”. ~ 28
0 ° C. ”. If the heating temperature in the filling step is less than 120 ° C., the epoxy resin is not sufficiently cured, which is not preferable. On the other hand, this heating temperature is 170 ° C
When cracks are exceeded, cracks in the build-up layer in the solder reflow step can be suppressed, but cracks may occur in the second cured body itself in a subsequent heat cycle test or the like. Further, if the heating temperature in the solder reflow step is lower than 230, an IC chip or the like cannot be mounted. On the other hand, if the heating temperature exceeds 280 ° C., the epoxy resin may be thermally degraded, which is not preferable.

Incidentally, a copper plating layer formed by electrolytic plating on the surface of the first cured body is JIS C6481.
The peel strength measured by “0.
8 kgf / cm or more ". If the peel strength between the first cured product and the copper plating layer is high, peeling and swelling of the copper plating layer can be sufficiently suppressed. Further, the water absorption of the first cured product is preferably “0.3% or less” as in the seventh invention. If the cured product has a low water absorption, the peel strength between the first cured product and the copper plating layer increases, and the peeling and swelling of the copper plating layer are more reliably prevented.

The paste for filling a through hole according to an eighth invention is a paste for filling a through hole used to fill a through hole of a printed wiring board, the paste comprising a metal filler having an average particle size of 0.5 to 20 μm; An epoxy resin composition comprising an epoxy resin and a curing agent. When the epoxy resin composition is 100 parts by weight, the amount of the epoxy resin is 90 to 99.5 parts by weight, and the amount of the curing agent is 0. 0.5 to 10 parts by weight, the metal filler is 500 to 1000 parts by weight, the viscosity of the paste at 25 ° C. is 20,000 poise or less, and the volatile content of the paste by heating in the filling process is 1 0.0% or less, and a film having a thickness of 100 μm made of the paste is heated at 150 ° C. for 5 hours to be cured. 5mm width using this film
When the temperature was increased from 23 ° C. to 270 ° C. in a state where a load of 5 g was applied in the length direction of the sample, and then lowered to 23 ° C., The shrinkage ratio in the length direction of the film calculated by the following formula is 0.1% or less.

In the eighth invention, the paste is not actually filled in the through-holes, cured, and the shrinkage in the solder reflow step is not evaluated. However, when the paste having a shrinkage of 0.1% or less measured by this method is filled in the through-hole, cured in the filling process, heated in the solder reflow process, and cooled, the copper plating layer peels off. It has been confirmed that swelling does not occur, and that gaps in the through holes and cracks in the build-up layer can be sufficiently suppressed. According to the eighth aspect, a paste that can be practically used and a paste that cannot be practically used can be easily separated by such a simple method. In addition, the above-mentioned rate of temperature rise and temperature fall is 1-5 ° C / min, especially 1-3 ° C /
Min, more preferably 2 ° C./min. Also, 27
After raising the temperature to 0 ° C., it is preferable to immediately lower the temperature.

In the printed wiring board according to the ninth aspect, the paste for filling the through-hole according to the first to eighth aspects is filled in the through-hole, heated and cured, and the copper plating layer is peeled off, swelled, and the through-hole is removed. The occurrence of cracks in the inside, bubbles in the first cured body, or cracks in the build-up layer in the solder reflow step is sufficiently suppressed. Therefore, the density and the number of layers in the printed wiring board can be easily increased, and in particular, a multilayer printed wiring board having excellent performance can be obtained.

In the paste for filling through holes of the present invention, a large amount of a metal filler, particularly a metal filler composed of spherical copper powder, is added to the epoxy resin composition. Therefore, the first cured body generated in the through hole by the hole filling step and the copper plating layer formed thereon are excellent in affinity. Further, in particular, by roughening the surface of the copper powder by a blackening treatment or the like, as shown schematically in FIG. 1, the adhesion between the particles of the copper powder and the epoxy resin has an anchor effect and This is enhanced by improving the chemical affinity, the generation of bubbles in the first cured body is suppressed, and the adhesion between the cured body and the copper plating layer is also enhanced. In FIG. 1, the surfaces of the copper powder particles have been oxidized by the blackening treatment. However, when the surface of the first cured body is polished by a buff or a belt sander, the surface of the copper powder particles near the surface is also polished to remove the oxide layer, thereby exposing metallic copper. Therefore, even when the blackened copper powder is used, the adhesion between the first cured product and the copper plating layer is not impaired at all.

Further, in the paste for filling through holes of the present invention, a metal filler is compounded in a high ratio, and
A phenol novolak type epoxy resin composed of bulky and rigid molecules is used. Therefore, the movement of molecules is restricted by steric hindrance at the time of curing, and the shrinkage ratio in the solder reflow step is extremely small, 0.1% or less, and the occurrence of cracks in the build-up layer is sufficiently suppressed. In addition, since a suitable amount of bisphenol-type epoxy resin consisting of linear and flexible molecules is used in combination, the workability of filling into through holes is excellent, and the obtained printed wiring board is used in equipment that incorporates it. Cracks do not occur in the second cured body itself due to a temperature change or the like.

The method of forming a copper plating layer on the surface of the cured product made of the paste of the present invention filled in the through holes is as follows. First, a paste is filled into a through hole provided in a printed board, an insulating resin is applied to both surfaces of the printed board and the through hole, and the insulating resin layer is polished by a buff or a belt sander. Then, a copper plating layer is formed on the entire front and back surfaces of the substrate by electroless plating, a plating resist is pasted on the copper plating layer, exposed and developed to form an opening on the through hole, and the opening is formed. Then, a copper plating layer is formed by an electrolytic plating method. Next, the resist is stripped, the remaining portion of the copper plating layer formed by the electroless method is removed, and a copper plating layer is formed on the through-hole.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to examples. Examples 1 to 7 and Comparative Examples 1 to 5 (1) Preparation of Paste and Measurement of Viscosity Filler and epoxy resin shown in Table 1 were used in a quantitative ratio shown in Table 1, and imidazole was used as a curing agent for the epoxy resin. -Based curing agent (trade name “2E4MZ” manufactured by Shikoku Chemicals Co., Ltd.)
-CN "), and mixed them to prepare a paste for filling through holes. 25 of this paste
The viscosity at ° C was measured by a rotating cylinder viscometer.

In Table 1, PN is phenol novolak type epoxy resin, and BPA is bisphenol A
Epoxy resin and BPF are bisphenol F epoxy resins. Further, when the amount of the epoxy resin is 100 parts by weight, the amount ratio of the bisphenol-type epoxy resin is about 8.4 parts by weight in Examples 1 to 3 and each comparative example, and about 26.6 parts in Examples 4 to 7. 3 parts by weight. Example 5
In Nos. To 7, the spherical copper powder was subjected to a surface treatment. The soft etching, the blackening treatment, and the treatment with the silane coupling agent were performed by a conventional method.

[0029]

[Table 1]

The fillers and epoxy resins used are as follows. (A) Filler Spherical copper powder, average particle size 5 μm; trade name “SFR-Cu-5 μm” manufactured by Japan Atomize Processing Co., Ltd. Spherical copper powder, average particle size 9 μm; trade name “Fukuda Metal Foil Powder Co., Ltd.” CU-FN-10 ”dendritic copper powder, average particle size 6 μm; Japan Energy Co., Ltd., trade name“ Den 4 ”spherical copper powder, average particle size 25 μm; Mitsui Kinzoku Mining Co., Ltd., trade name“ C0610 ”spherical Silica, average particle size 2 μm; trade name “SO-E3” manufactured by Tatsumori Corporation

(B) Epoxy resin Phenol novolak type epoxy resin; trade name "E-152" manufactured by Yuka Shell Co., Ltd. Bisphenol A type epoxy resin; trade name "E-
819 "bisphenol F type epoxy resin;
806 "(c) Surface treatment agent Epoxy silane coupling agent; brand name" KBM403 "manufactured by Shin-Etsu Chemical Co., Ltd.

(2) The volatile content of the paste and the water absorption of the cured product generated by heating corresponding to the filling process, and the peel strength between the cured product and the copper plating layer. The cured product was heated to 300 ° C. by a thermal mass-differential thermal analyzer. The volatile content of the above paste in each case was measured. The water absorption of the resulting cured product was measured in accordance with JIS K 6911. Furthermore, the core substrate (copper-clad laminate, 1
(00 × 100 mm), and the paste was applied to a thickness of about 300 μm, heated at 150 ° C. for 5 hours, and cured.
The resin component is soft-etched, and then about 100% on the cured body by electroless plating and electrolytic plating.
A copper plating layer having a thickness of μm is formed.
According to 6481, the peel strength of the copper plating layer from the cured product was measured.

(3) Measurement of shrinkage rate due to heating and cooling corresponding to the solder reflow process The paste is cast on a synthetic resin sheet,
After forming a film having a thickness of 100 μm, the film was heated at 150 ° C. for 5 hours to cure the epoxy resin. Thereafter, a test piece having a length of 20 mm and a width of 5 mm was prepared from the film, and the distance between the chucks was set to 15 mm.
After the load was applied, the temperature was raised from 23 ° C. to 270 ° C. at a rate of 2 ° C./min by a thermomechanical analyzer (TMA), and then lowered to 23 ° C. at the same rate. Then, based on the obtained TMA chart, the shrinkage length [23 ° C. before temperature rise]
-Reading of length on chart at 23 ° C. after cooling (unit: μm)], and dividing the contracted length by the length of the specimen before heating. To determine the shrinkage.

The viscosity of the paste and the paste
Volatile content when cured by heating at 5 ° C. for 5 hours, the water absorption of the cured product cured by this heating, the peel strength of the copper plating layer on the cured product, and the rise of the cured product from 23 ° C. to 270 ° C. Table 2 shows the shrinkage ratio when the temperature was lowered to 23 ° C. again after the heating.

[0035]

[Table 2]

According to the results in Table 2, in Examples 1 to 7,
The viscosity of the paste is 3500-16000 poise,
The volatile content of the cured product is 0.20% or less, and the water absorption is 0.17 to
The peel strength between the cured product and the copper plating layer was 0.86 to 1.24 kgf / cm, which indicates that the paste for filling through holes has excellent characteristics. In addition, after the cured product was heated to 270 ° C., the shrinkage upon cooling was all less than 0.1%, and it is assumed that the occurrence of cracks and the like in the build-up layer was reliably suppressed. Further, in Examples 5 to 7 in which the surface treatment was applied to the copper powder, the peel strength was greater than 1 kgf / cm, and particularly in Example 6 in which soft etching and blackening were combined, the peel strength was 1. It is 24 kgf / cm.

On the other hand, in Comparative Example 1 using 150 parts by weight of spherical silica, the volatile component and the water absorption were high, swelling was observed in a part of the copper plating layer, and the peel strength was greatly reduced.
In Comparative Example 2 in which the amount of spherical copper powder added was less than the lower limit, although the peel strength was good, the water absorption was high, and
After heating to 0 ° C., the shrinkage upon cooling also greatly exceeds the upper limit. Furthermore, in Comparative Example 3 in which the amount of spherical copper powder added exceeded the upper limit, and in Comparative Example 4 in which dendritic copper powder instead of spherical powder was used, the paste became clumpy, and the property could not be evaluated. In Comparative Example 5, in which the average particle size of the spherical copper powder exceeded the upper limit, although the peel strength was good,
A part of the copper plating layer swelled and could not be put to practical use.

[0038]

According to the first aspect of the present invention, the first cured product formed by curing the through hole filling paste and the copper plating layer formed on the through hole have excellent adhesion, and the copper plating layer There is no occurrence of peeling, swelling, etc. Further, there is no gap between the copper plating layer formed on the wall surface of the through hole and the first cured body. Furthermore, the shrinkage in the length direction of the through-hole of the second cured body in the solder reflow step is small, and the occurrence of cracks in the build-up layer can be suppressed. Further, by using the specific epoxy resin composition in the fourth invention, not only the shrinkage ratio is small, but also the workability of filling the through holes is excellent, and a printed wiring board using this paste is incorporated. Cracks do not occur in the second cured body itself due to an environmental change or the like during use of the device. In addition, the eighth
According to the invention, it is possible to confirm that the paste has excellent performance according to the first invention by a simple method.

In the printed wiring board according to the ninth aspect of the present invention, the first cured body and the copper plating layer are not separated from each other in the through hole and on the through hole, and the build-up layer and the second cured body itself are not separated. In this case, the occurrence of cracks is also suppressed, and it is possible to easily increase the wiring density and increase the number of layers.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a state of a copper powder in a first cured body, particularly in the vicinity of an end surface of a through hole, when a filler made of a copper powder subjected to a blackening treatment and having a roughened surface is used.

FIG. 2 is a schematic diagram showing a state in which a copper plating layer is provided on an end surface of a through hole, and a via hole is formed thereon.

FIG. 3 is a schematic view showing a state in which a via hole is formed avoiding a through hole.

FIG. 4 is a schematic diagram showing a state of peeling and swelling between a plating layer and a first cured body.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1; Multilayer board, 2; Through hole, 3; Copper plating layer, 3
1; a portion where the copper plating layer was peeled off and swollen; 4; a roughened copper powder; 41; metallic copper; 42; an oxide layer; 5; a spherical silica; 6; a build-up layer;

Continued on the front page (51) Int.Cl. ⁶ Identification code FI H05K 1/09 H05K 1/09 D 3/40 3/40 K

Claims (9)

[Claims] 1. A paste for filling a through-hole used to fill a through-hole of a printed wiring board, the paste comprising a metal filler having an average particle size of 0.5 to 20 μm, an epoxy resin and a curing agent. An epoxy resin composition, wherein the epoxy resin composition is 100
When the amount is 90 parts by weight, the epoxy resin is 90-99.
5 parts by weight, the curing agent is 0.5 to 10 parts by weight, the metal filler is 500 to 1000 parts by weight, and the viscosity of the paste at 25 ° C. is 2,000.
0 poise or less, the volatile content of the paste by heating in the filling process is 1.0% or less, and the first cured product generated by heating in the filling process is heated and cooled in the solder reflow process. A paste for filling a through hole, wherein a shrinkage ratio of a generated second cured body in a length direction of the through hole is 0.1% or less. 2. The paste for filling a through hole according to claim 1, wherein the metal filler is a spherical copper powder subjected to blackening treatment. 3. The surface of the metal filler is treated with a silane coupling agent having an epoxy group.
Or the paste for filling through holes according to 2 above. 4. The epoxy resin comprises: (1) a phenol novolak type epoxy resin; and (2) bisphenol A
(1) is 70 to 99 parts by weight when containing at least one of the epoxy resin and the bisphenol F epoxy resin, and when the total amount of the above (1) and (2) is 100 parts by weight. And (2) is 1-3
The paste for filling a through hole according to any one of claims 1 to 3, which is 0 parts by weight. 5. The heating temperature in the filling step is 12 or less.
The paste for filling a through hole according to any one of claims 1 to 4, wherein the paste has a temperature of 0 to 170C and a heating temperature of 230 to 280C in the solder reflow step. 6. A JIS C 6481 of a copper plating layer formed on the surface of the first cured body by an electrolytic plating method.
The paste for filling a through hole according to any one of claims 1 to 5, wherein the peel strength measured by the method is 0.8 kgf / cm or more. 7. The paste for filling a through-hole according to claim 1, wherein the first cured product has a water absorption of 0.3% or less. 8. A paste for filling a through-hole used to fill a through-hole of a printed wiring board, the paste comprising a metal filler having an average particle size of 0.5 to 20 μm, an epoxy resin and a curing agent. An epoxy resin composition, wherein the epoxy resin composition is 100
When the amount is 90 parts by weight, the epoxy resin is 90-99.
5 parts by weight, the curing agent is 0.5 to 10 parts by weight, the metal filler is 500 to 1000 parts by weight, and the viscosity of the paste at 25 ° C. is 2,000.
0 poise or less, the volatile content of the paste by heating in the filling process is 1.0% or less, and a 100 μm-thick film made of the paste is cured at 150 ° C. for 5 hours.
The film was cured by heating for a period of time, and then a 5 mm wide specimen was prepared using this film. Then, the specimen was heated from 23 ° C. to 270 ° C. with a load of 5 g applied in the longitudinal direction of the specimen. A paste for filling a through-hole, wherein the shrinkage in the longitudinal direction of the film, calculated by the following equation, is 0.1% or less when the temperature is lowered to 23 ° C. after the heating. Shrinkage (%) = [length of specimen at 23 ° C. before heating to 270 ° C.-length of specimen at the time of cooling to 23 ° C. after heating to 270 ° C.] / Specimen length at 23 ° C before heating to 270 ° C x 100 9. A printed wiring board, wherein the paste for filling a through hole according to claim 1 is filled in a through hole, heated and cured.