JPH1154937A - Insulation adhesive for multilayered printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printed wiring board with an insulation layer without glass cloth wherein layer insulation resin thickness varies a little. SOLUTION: In insulation adhesive formed by applying an insulation resin composition wherein borominated bisphenol type epoxy resin or borominated phenoxy resin of weight average molecular weight of 10000 or more of which boromination rate is 20% or more and bisphenol type epoxy resin of epoxy equivalent of 1000 or less are incorporated as essential elements to a copper foil 1, at least two resin layers are formed, flow in a resin layer 2 at the closest side to a copper foil is made practically zero, and a softening point of the outermost resin layer 3 is made 60 to 90 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an insulating adhesive suitable as an interlayer insulating material of a multilayer printed wiring board, and more particularly, it can secure a constant interlayer insulating layer thickness, is flame retardant, has excellent storage stability, and And an epoxy resin-based insulating adhesive which can be rapidly cured at a high temperature of 100 ° C. or higher.

[0002]

2. Description of the Related Art Conventionally, when a multilayer printed wiring board is manufactured, one or more prepreg sheets obtained by impregnating a glass cloth base material with an epoxy resin and semi-curing are laminated on an inner circuit board on which a circuit is formed. A process of laminating a copper foil thereon and integrally press-molding with a hot plate press is performed. The multilayer printed wiring board thus obtained is expensive due to the step of setting the glass cloth prepreg and the copper foil on the inner layer circuit board at the time of multilayer laminating press and the cost of the glass cloth prepreg. In addition, it is difficult to keep the thickness of the interlayer insulating resin constant because a molding method is employed in which a resin is caused to flow at the time of pressing to bury the space between the inner layer circuits and to expel voids by the resin flow. In addition, the presence of glass cloth between circuit layers may affect moisture absorption resistance and migration resistance depending on the degree of impregnation of the resin with the glass cloth.

In recent years, in order to solve these problems, a technique for manufacturing a multilayer printed wiring board using existing press equipment without using a glass cloth has been renewed.
However, in the pressing method, it is difficult to reduce the variation in the insulation thickness between circuit layers because there is no glass cloth substrate in the conventional technique.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a printed wiring board having a circuit interlayer insulating layer having no glass cloth and having a small variation in the thickness of the interlayer insulating resin which is a problem.

In the case of using a film-like interlayer insulating resin in a multilayer printed wiring board by a build-up method,
Since there is no glass cloth base material, there is a large variation in the interlayer thickness after press molding, and the range of molding conditions is small, so that molding is very difficult.

In such a process, when a roughened surface of a copper foil is coated with an insulating resin, if a resin having a high softening point is coated, the flow at the time of molding is small, and a flow amount sufficient to embed irregularities in an inner layer circuit is secured. It is difficult. In addition, if the softening point of the resin is lowered to increase the flow at the time of molding, the irregularities of the inner layer circuit can be buried, but the flow amount is too large and it is difficult to secure a constant insulating interlayer thickness. The present invention has been studied and completed in order to improve such a problem.

[0007]

The present invention relates to (1) a brominated bisphenol type epoxy resin or a brominated phenoxy resin (A) having a bromination ratio of 20% or more and a weight average molecular weight of 10,000 or more, and (2) an epoxy resin. In an insulating adhesive obtained by applying an insulating resin composition containing a bisphenol-type epoxy resin (B) having an equivalent weight of 1000 or less as an essential component to a copper foil, the resin layer is made two or more layers, and the resin layer on the most copper foil side is formed. With the flow substantially zero, the outermost resin layer has a softening point of 60.
To 90 ° C.

FIG. 1 shows an example of the insulating adhesive for a multilayer printed wiring board according to the present invention. FIG. 1 shows the case where the resin is applied to two layers, (1) is a copper foil, (2) is a resin layer having substantially zero flow on the copper foil side, and (3) is a softening point of the outermost layer of 60 to 90.
It is a resin layer of ° C. In the case of three or more layers, the intermediate layer may have an intermediate performance between the two. In the present invention, the flow at the time of molding of the copper foil side resin layer (2) is substantially zero. The term “zero flow” means that the melt viscosity does not decrease even when the resin is melted when heated, and has no fluidity when a molding pressure is applied. The main component, a brominated epoxy resin or brominated phenoxy resin having a bromination ratio of 20% or more and a weight average molecular weight of 10,000 or more, reduces the resin flow during molding and maintains the thickness of the insulating layer, and the composition It is blended for the purpose of imparting flexibility to the composition and achieving flame retardancy of the obtained multilayer printed wiring board. Such epoxy resins or phenoxy resins include brominated bisphenol A type epoxy resins, brominated bisphenol F type epoxy resins, brominated phenoxy resins, and the like.
Type epoxy resins or brominated phenoxy resins are preferred.
The proportion of the high molecular weight epoxy resin or phenoxy resin is preferably 55 to 90% by weight based on the whole resin. When the amount is less than 55% by weight, the viscosity does not increase and the thickness of the non-flow resin cannot be maintained sufficiently. Therefore, it is difficult to secure the thickness of the insulating layer after lamination.
The outer circuit becomes less smooth. On the other hand, 90% by weight
If it is larger, the viscosity becomes too high, the application to the copper foil is not easy, and it may be difficult to maintain a predetermined resin thickness.

The high-molecular-weight epoxy resin alone has a low crosslinking density after curing and is too flexible, and has a low viscosity when dissolved in a solvent to form a varnish at a predetermined temperature for coating on a copper foil. And the workability during coating is not good. In order to improve such a defect, an epoxy equivalent of 10
No more than 00 bisphenol type epoxy resin is blended.
This mixing ratio is 10 to 45% by weight of the whole resin. Although the flow at the time of molding can be substantially reduced to zero by blending such a resin, when the flow after coating and drying is not zero, the reaction can be advanced by heating to reduce the flow to zero. However, it is set so that the curing does not proceed excessively and the adhesiveness to the second layer is not impaired.

The outermost resin layer (2) has a softening point of 60 to 90.
° C. That is, a brominated epoxy resin or brominated phenoxy resin having a bromination ratio of 20% or more and a weight average molecular weight of 10,000 or more and a bisphenol-type epoxy resin having an epoxy equivalent of 1000 or less are mixed to have a softening point of 60 to 90 ° C.
Adjust to In this way, a flow amount for embedding the unevenness of the inner layer circuit is secured. The type and amount of the bisphenol-type epoxy resin to be used are not particularly limited as long as the softening point of the mixed resin can be set to 60 to 90 ° C. However, if a large amount of the epoxy resin that is liquid at room temperature is mixed, the liquid epoxy resin is stained from the resin layer at room temperature, which is not preferable. Therefore, the amount of the liquid epoxy resin is preferably 10 to 45% by weight. Hereinafter, each component used in the copper foil side resin layer and the outermost resin layer will be described. The bromination ratio of the brominated epoxy resin or brominated phenoxy resin is 20% or more. Bromination rate 2
When it is less than 0%, the obtained multilayer printed wiring board cannot achieve the flame retardancy V-0.

The epoxy resin to be compounded is bisphenol A type epoxy resin, bisphenol F type epoxy resin or the like. If a brominated resin is used, the flame retardancy of the multilayer printed wiring board can be more effectively achieved. More specifically, epoxy equivalent of about 200, epoxy equivalent of 4
These are used alone or in combination in consideration of workability when applying about 50 to a copper foil.

Next, the epoxy resin curing agent is not particularly limited, such as an amine compound, an imidazole compound, and an acid anhydride. However, the imidazole compound can sufficiently cure the epoxy resin even if the compounding amount is small. It is preferable since the brominated epoxy resin can exhibit flame retardancy. The imidazole compound is solid at room temperature with a melting point of 130 ° C. or higher, has low solubility in epoxy resin,
Particularly preferred are those which reach a high temperature of 150 ° C. or higher and react quickly with the epoxy resin. Specifically, 2-methylimidazole, 2-phenylimidazole, 2-phenyl-
4-methylimidazole, bis (2-ethyl-4-methyl-imidazole), 2-phenyl-4-methyl-5-
Hydroxymethylimidazole, 2-phenyl-4,5
-Dihydroxymethyl imidazole or triazine addition type imidazole. These imidazoles are uniformly dispersed as fine powder in the epoxy resin varnish. Low compatibility with epoxy resin, so
At 00 ° C., the reaction does not proceed, so that good storage stability can be maintained.

In applying two or more layers of the resin composition, when the first layer is applied and dried and then the second layer is applied, the first layer is almost uncured, so that the adhesion between the two layers is good. is there. Similarly, when the third layer is applied, adhesion to the second layer is good. In this way, even when the amount of heat received during drying of the initially applied layer increases, it is possible to apply the layers in layers. In addition, a resin having a small flow is applied to a copper foil, while a resin whose softening point is adjusted to 60 to 90 ° C. is applied to a release carrier, and these are pressure-bonded by a hot roll with the applied resin inside, and insulation bonding is performed. It is also possible to form an agent layer. When heated to 150 ° C. or higher during press molding, it reacts with the epoxy resin to obtain a uniform cured product.

In addition to the above components, fused silica, crystalline silica, calcium carbonate, aluminum hydroxide, alumina, clay, barium sulfate, mica, talc, and the like are used for improving the coefficient of linear expansion, heat resistance, and flame resistance. White carbon, E glass fine powder and the like may be blended in an amount of 40% by weight or less based on the resin component. If the content is more than 40% by weight, the viscosity of the interlayer insulating resin increases, and the embedding property between the inner layer circuits is reduced.

Further, a silane coupling agent such as epoxy silane or a titanate coupling agent for improving adhesion to a copper foil or an inner layer circuit board or improving moisture resistance, an antifoaming agent for preventing voids, Alternatively, a liquid or fine powder type flame retardant can be added.

As a solvent, an adhesive is applied to a copper foil and
After drying at <RTIgt; C-130 C, </ RTI> those that do not remain in the adhesive must be selected. For example, acetone,
Methyl ethyl ketone, toluene, xylene, n-hexane, methanol, ethanol, methyl cellosolve, ethyl cellosolve, methoxypropanol, cyclohexanone and the like are used.

The copper foil with an interlayer insulating adhesive is prepared by applying an adhesive varnish obtained by dissolving an adhesive component in a predetermined solvent at a predetermined concentration to an anchor surface of a copper foil, and then drying at 80 ° C. to 130 ° C. to form a first layer. Is prepared. Drying is performed so that the volatile component in the adhesive is 1.0% or less, preferably 0.1 to 0.5% with respect to the resin. When the content is less than 0.1%, the curing reaction proceeds, which may adversely affect the moldability. The resin thickness of the first layer (most copper foil side) is preferably 15 μm to 70 μm.
If the thickness is less than 15 μm, drying may be excessive. 70μ
When it is thicker than m, the volatile component in the resin tends to exceed 1.0%. When the second and subsequent layers are applied under the same conditions as described above, it is possible to ensure the properties of the resin such as tackiness, storage stability, and peel strength without variation due to the thickness.

The copper foil with an insulating adhesive is laminated on an inner circuit board by a normal vacuum press and cured, so that a multilayer printed wiring board having an outer circuit can be easily formed.

[0020]

【Example】

<Example 1> Brominated phenoxy resin (bromination ratio 25%,
100 parts by weight (weight average molecular weight: 30,000) (hereinafter, the blending amounts are all represented by parts by weight) and 40 parts of a bisphenol F type epoxy resin (epoxy equivalent: 175, Epicron 830 manufactured by Dainippon Ink and Chemicals, Inc.) are stirred into MEK. 5 parts by weight of 2-methylimidazole as a curing agent and a titanate-based coupling agent (KR-4 manufactured by Ajinomoto Co., Inc.)
6B) A resin varnish on the copper foil side was prepared by adding 0.3 parts by weight and 30 parts of calcium carbonate. Separately, brominated phenoxy resin (bromination ratio 25%, weight average molecular weight 30,000) 1
00 parts and a bisphenol F type epoxy resin (epoxy equivalent: 175, Epicron 83 manufactured by Dainippon Ink and Chemicals, Inc.)
0) 50 parts, 10 parts of a solid bisphenol A type epoxy resin having an epoxy equivalent of 450 (epoxy equivalent: 450, Epicoat 1001 manufactured by Yuka Shell Co., Ltd.) were stirred and dissolved in MEK, and 5 parts by weight of 2-methylimidazole was used as a curing agent. Part, titanate coupling agent (manufactured by Ajinomoto Co., Inc.)
KR-46B) 0.3 part by weight and 30 parts of calcium carbonate were added to prepare a copper foil side resin varnish having a softening point of 86 ° C.

The resin varnish is applied to the anchor surface of a copper foil (1) having a thickness of 18 μm by a comma coater so that the first layer has a dry resin thickness of 50 μm and the second layer has a dry resin thickness of 50 μm.
The layer was coated and dried to obtain a copper foil (3) with an insulating adhesive having a total resin thickness of 100 μm.

Further, the thickness of the base material is 0.1 mm, and the thickness of the copper foil is 35 μm.
The glass-epoxy double-sided copper-clad laminate was subjected to pattern processing to obtain an inner circuit board. After the surface of the copper foil was blackened, the copper foil with the insulating adhesive was set on both sides.

The set material is placed between the materials by 1.6.
mm stainless steel mirror plate, put 15 sets in one stage, raise temperature 3 ° C-10 ° C / min, pressure 10-30Kg / cm
^2. Under a condition of a vacuum degree of -760 to -730 mmHg, a vacuum press was used to heat mold at a temperature of 150 ° C. for 20 minutes to produce a multilayer printed wiring board.

<Example 2> Example 1 was repeated except that the outermost resin was 50 parts of a solid epoxy resin and the softening point was 70 ° C.
A multilayer printed wiring board was produced in the same manner as described above.

<Comparative Example 1> A copper foil with an insulating adhesive was used only in the resin layer on the side of the most copper foil in Example 1 and had a dry resin thickness of 100.
A multilayer printed wiring board was obtained in the same manner as in Example 1 except that the thickness was changed to μm. Comparative Example 2 A multilayer printed wiring board was obtained in the same manner as in Example 1 except that the outermost resin layer was made of a copper foil with an insulating adhesive and the dry resin thickness was 100 μm. <Comparative Example 3> Using a normal glass cloth prepreg having a thickness of 0.1 mm and a copper foil having a thickness of 18 μm,
A 1.6 mm stainless steel mirror plate is sandwiched between the materials.
15 sets are put in the stage, and the temperature is raised at 3 ° C./min, and the pressure is 35 kg /
cm ² , and a degree of vacuum of −760 to −730 mmHg,
Heat molding was performed using a vacuum press at a temperature of 170 ° C. for 80 minutes to produce a multilayer printed wiring board.

With respect to the obtained multilayer printed wiring board, a molding void, an interlayer thickness, and a resin flow amount around the board were measured. The results are shown in Table 1.

[0028]

[Table 1]

(Measurement method) Inner layer circuit board test piece: line width L / line interval width S = 120/180 (μm), clearance holes 1 mmφ and 3 mmφ 2 mm slit. 1. Molded voids: The presence or absence of voids in the above-mentioned pattern line portions and clearance holes was visually observed. 2. Insulation layer thickness on inner layer circuit: Observed by cross section, L / S = 120/180 μm at the observation site, measured the insulation layer thickness on the inner layer circuit of 2 mm slit part, 15 products obtained in one stage The absolute value of the difference between the inner and outermost ones and the central one was determined. 3. Resin flow around the product: Measure the length of resin flow flowing out of the inner circuit board.

[0030]

The insulating adhesive for a multilayer printed wiring board of the present invention can produce a printed wiring board having an insulating layer having no glass cloth and having a small variation in interlayer insulating resin thickness.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of an insulating adhesive for a multilayer printed wiring board according to the present invention.

[Explanation of symbols]

 1 copper foil 2 resin layer on the most copper foil side 3 outermost resin layer

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Tetsuji Yamamoto 2-5-8 Higashishinagawa, Shinagawa-ku, Tokyo Sumitomo Bakelite Co., Ltd.

Claims (2)

[Claims] 1. A brominated bisphenol type epoxy resin or brominated phenoxy resin (A) having a bromination ratio of 20% or more and a weight average molecular weight of 10,000 or more, and (2) a bisphenol type epoxy resin having an epoxy equivalent of 1,000 or less. In an insulating adhesive obtained by applying an insulating resin composition containing (B) as an essential component to a copper foil, the number of resin layers is two or more, and the flow of the resin layer on the copper foil side is substantially zero. An insulating adhesive, wherein the outer resin layer has a softening point of 60 to 90 ° C. 2. The method according to claim 1, wherein the epoxy curing agent is 2-methylimidazole, 2-phenylimidazole, 2-phenyl-4-.
An insulating adhesive which is one or more kinds of imidazole compounds selected from methyl-5-hydroxymethylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole and triazine addition type imidazole.