JPH0734506B2 - Multilayer printed wiring board - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer printed wiring board used by being incorporated in electronic or electric equipment.

2. Description of the Related Art In consideration of machinability of a multilayer printed wiring board, a base material forming a substrate of an inner circuit board, a base material forming an insulating layer (inner insulating layer) between the inner circuit boards, an inner layer There has been proposed a composite multilayer printed wiring board in which a glass non-woven fabric and a glass woven fabric are appropriately combined with a base material forming an insulating layer between the circuit board and the surface circuit.

In this regard, in the technique disclosed in Japanese Patent Laid-Open No. 61-40094, the circuit board substrate of the inner layer is composed of an epoxy resin-impregnated glass woven base material. Then, two kinds of epoxy resin-impregnated glass non-woven fabric base materials (inner layer insulation layers) having different compounding amounts of fillers are interposed between the surface layer epoxy resin-impregnated glass woven base material and the inner layer circuit board to be integrated. It has been transformed.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, since the above-mentioned multilayer printed wiring board uses the glass woven fabric substrate for the inner layer circuit board and the surface layer, when a plurality of the drilled holes are drilled, It is easy to cause the holes to be out of position This misalignment becomes more remarkable in the multilayer printed wiring boards stacked below. If the base material of the circuit board of the inner layer is replaced with a glass non-woven fabric, the drilling workability is improved, but the dimensional stability is reduced. Since the circuit on the inner layer and the circuit on the surface are electrically connected by the through holes after the multi-layering, it is a fatal problem that the circuit board of the inner layer undergoes a dimensional change during the manufacturing process.

Further, in the technique in the above publication, two types of fillers having different compounding amounts are used in combination as the epoxy resin-impregnated glass nonwoven fabric substrate which is the inner insulating layer in consideration of dimensional stability, interlayer adhesion, and generation of voids. However, the multi-layered work becomes complicated.

An object of the present invention is to use a glass woven fabric base material only as a surface layer, while using a glass non-woven fabric as a base material to be used for the inner layer, excellent in dimensional stability and interlayer adhesion (particularly for the inner layer circuit surface and the inner layer insulating layer). It is to provide a multilayer printed wiring board having good adhesion).

Means for Solving the Problems In order to solve the above problems, the multilayer printed wiring board according to the present invention employs the following integrated layer structure.

(A) The substrate 2 of the inner layer circuit board in which the surface of the circuit 1 is finely roughened by chemical treatment is made of a thermosetting resin-impregnated glass nonwoven fabric base material. The resin contains 30 to 50% by weight of inorganic filler.

(B) The insulating layer (surface insulating layer 4) of the surface circuit 3 is made of a thermosetting resin-impregnated glass woven fabric base material.

(C) The insulating layer between the surface insulating layer 4 and the inner circuit board (inner insulating layer 5) is made of a thermosetting resin-impregnated glass nonwoven fabric base material. The resin contains 5 to 20% by weight of inorganic filler.

In addition, when there are two or more inner layer circuit boards, the inner layer insulating layers 5 described above in (c) are also provided between the inner layer circuit boards.

The surface of the inorganic filler contained in the inner insulating layer is preferably treated with silane.

Action The adhesive force between the inner layer circuit board and the inner layer insulating layer 5 is due to the chemical bond in the portion where the surface of the substrate 2 is exposed. However, in the portion of the circuit 1, the resin of the inner insulating layer 5 flows at the time of heat and pressure molding to enter into fine irregularities on the surface of the circuit 1 due to the chemical treatment, and the anchoring effect causes a physical bond to make a close contact. I have power.

When the base material of the inner insulating layer 5 is a glass woven fabric, the physical binding force due to the anchoring effect is large, but when the base material is a glass nonwoven fabric, the binding force is not sufficiently large. This is presumed to be due to the following reasons. That is, since the glass non-woven fabric is bulky and has many voids, the resin that flows at the time of heat and pressure molding is preferentially used to fill the voids and does not sufficiently flow into the fine irregularities on the surface of the circuit 1 ( It is hard to flow in).
Based on such knowledge, in the multilayer printed wiring board according to the present invention, the resin of the inner insulating layer 5 contains an inorganic filler, which is sufficiently larger than the fine irregularities on the surface of the circuit 1. The material particles deform the metal foil forming the circuit 1 during the heat and pressure forming, and the metal particles are hard to be included. It is presumed that the anchoring effect is combined with the anchoring effect due to the resin flowing into the fine irregularities on the surface of the circuit 1, and the good adhesion between the circuit 1 and the inner insulating layer 5 can be maintained.

In this case, the anchoring effect cannot be exhibited unless the amount of the inorganic filler contained in the resin of the inner insulating layer 5 reaches 5% by weight. On the other hand, when the amount of the inorganic filler exceeds 20% by weight, the amount of the resin that binds the filler particles to each other is small and the filler particles are easily separated. Inorganic filler content 5-20
It is possible to secure good adhesion between the circuit 1 and the inner insulating layer 5 for the first time by setting the content in the range of wt%.

Further, if the content of the inorganic filler in the resin of the substrate 2 does not reach 30% by weight, the dimensional change cannot be sufficiently suppressed, and if it exceeds 50% by weight, the adhesive force between the substrate 2 and the circuit 1 decreases and the insulation Resistance becomes worse. Regarding the adhesion between the circuit 1 and the substrate 2,
Since the back surface of the metal foil forming the circuit 1 can be mechanically roughened to have large irregularities, the flowed resin easily flows in, and even if the content of the filler is higher than that of the inner insulating layer 5, the anchoring of the resin is performed. You can expect a sufficient effect.

Examples Hereinafter, examples of the present invention will be described together with comparative examples. An example of using hydrated alumina as the inorganic filler will be described.
It has been confirmed that the same tendency is exhibited when other inorganic fillers are used.

Examples 1 to 6 and Comparative Examples 1 to 4 (1) 3 wt% (A) and 5 wt% of hydrated alumina treated with epoxysilane (epoxysilane is 1% based on the weight of hydrated alumina), respectively. % (B), 10% by weight
(C), 15% by weight (D), 20% by weight (E), 25% by weight
(F), 35 wt% (G), 40 wt% (H), 45 wt%
A bisphenol type epoxy resin containing (I) and 55% by weight (J) was prepared. A glass non-woven fabric (41 g / m ² ) was impregnated with this varnish so that the resin content containing hydrated alumina was 88% by weight, and dried to obtain prepregs (A) to (J) corresponding to the above hydrated alumina content. Got

A varnish of the above epoxy resin containing no hydrated alumina,
Glass woven cloth (215 g /
m ² ) was impregnated and dried to obtain a prepreg (X).

(2) For each of the prepregs (F) to (J), a 35μ thick copper foil is placed on both sides of the 4 plies, and a 0.8mm thick double-sided copper clad laminate for inner layer circuit board is formed by heat and pressure molding. Obtained. The copper foil used was one in which the side facing the prepreg was mechanically roughened to give unevenness.

This double-sided copper-clad laminate was etched by a conventional method to form a circuit, and the surface of the circuit was finely roughened by blackening to obtain an inner layer circuit board.

(3) The inner insulating layer is selected from prepregs (A) to (F). A prepreg 1 ply selected from (A) to (F), a prepreg (X) 1 ply, and a 18 μm thick copper foil were placed in this order on both sides of the inner layer circuit board, and heat-press formed to integrate them. Thickness 1.6mm).

(4) The integrated composite plate was drilled according to a predetermined pattern, and through-hole plating for conducting the inner layer circuit and the surface copper foil was conducted by a conventional method.

(5) The copper foil on the surface was etched by a conventional method to form a surface circuit to obtain a printed wiring board having four layers of circuits.

Tables 1 and 2 show combinations of the types of prepreg used for the substrate of the inner layer circuit board and prepreg used for the inner insulating layer.

Example 7 A four-layer printed wiring board was prepared in the same manner as in Example 2 except that hydrated alumina was not treated with epoxysilane.

Comparative Example 5 The substrate of the inner layer circuit board was composed of prepreg (X) 4 plies. Others were the same as Example 2, and it was set as the 4-layer printed wiring board.

Table 3 shows the workability of Example 2 and Comparative Example 5 when three of them were stacked and drilled.

FIG. 2 shows the relationship between the filler content of the inner insulating layer and the peel strength (adhesion between the circuit surface of the inner layer and the inner insulating layer). The relationship between the filler content of the substrate of the inner layer circuit board, the dimensional change of the substrate and the insulation resistance is shown in FIG. The dimensional change is
Etching → The dimensional change rate in the diagonal direction of the sample before and after the 0.5 / 150 treatment is shown. The insulation resistance was measured after the pressure cooker (2 atm, 121 ° C.) treatment for 8 hours.

EFFECTS OF THE INVENTION As described above, the multilayer printed wiring board according to the present invention, while using the glass nonwoven fabric as the base material of the inner insulating layer, by setting the content of the inorganic filler to a specific range, the inner layer circuit and It maintains good adhesion of the inner insulating layer. This adhesion is further improved by treating the filler with a silane coupling agent. Further, while using a glass nonwoven fabric as the substrate of the substrate of the inner layer circuit board, the dimensional stability is good and the machinability is excellent, and the industrial value thereof is extremely large.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a 6-layer circuit of a multilayer printed wiring board according to the present invention, and FIG. 2 is a filler content and peel strength of the inner insulating layer (adhesion between the inner circuit surface and the inner insulating layer). ), And FIG. 3 is a curve diagram showing the relationship between the filler content of the substrate of the inner layer circuit board, the dimensional change rate, and the insulation resistance. 1 is a circuit, 2 is a substrate, 3 is a surface circuit, 4 is a surface insulating layer,
5 is the inner insulating layer

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hiromitsu Kimura 2-1-1, Nishishinjuku, Shinjuku-ku, Tokyo Minoru Kino, Examiner, Shin-Kindo Electric Co., Ltd. (56) , A) Japanese Unexamined Patent Publication No. 63-38298 (JP, A) Actual development No. 62-170678 (JP, U)

Claims (3)

[Claims] 1. A substrate of an inner layer circuit board whose circuit surface is finely roughened by a chemical treatment is composed of a thermosetting resin-impregnated glass nonwoven fabric base material, and an insulating layer (surface insulating layer) of a surface circuit is thermoset. Insulating layer between the surface insulating layer and the inner circuit board (inner insulating layer)
Is a thermosetting resin-impregnated glass non-woven fabric base material, which is integrated by heat and pressure molding, and contains 30 to 50% by weight of inorganic filler in the resin of the substrate of the inner layer circuit board. A multilayer printed wiring board containing 5 to 20% by weight of an inorganic filler in the resin of the inner insulating layer. 2. A substrate of an inner layer circuit board whose circuit surface is finely roughened by chemical treatment is composed of a thermosetting resin-impregnated glass nonwoven fabric base material, and an insulating layer (surface insulating layer) of the surface circuit is thermoset. Thermosetting resin impregnated glass non-woven fabric substrate, which is made of a thermosetting resin-impregnated glass woven fabric base material, and the insulating layer between the surface insulating layer and the inner layer circuit board and the insulating layer (inner layer insulating layer) between the inner circuit boards are The resin of the inner layer circuit board contains 30 to 50% by weight of the inorganic filler in the resin of the inner layer insulating layer. A multilayer printed wiring board containing 5 to 20% by weight of an inorganic filler. 3. The multilayer printed wiring board according to claim 1, wherein the surface of the filler of the inner insulating layer is treated with a silane coupling agent.