JPH03116894A - Multilayer printed wiring board - Google Patents

Abstract

PURPOSE:To obtain a multilayer printed wiring board which is excellent in dimensional stability and interlaminar adhesion by a method wherein specific inorganic filler is contained in the resin of an inner circuit board and also in the resin of an inner insulating layer. CONSTITUTION:Hydrated alumina is used as inorganic filler, a glass nonwoven cloth containing 30-50% by weight of hydrated alumina is impregnated with bisphenol type epoxy resin varnish, which is dried up to be served as a prepreg, and an a thick copper foil is laid on both sides of the prepreg, which is formed into a double side copper clad laminated board 2 which serves as an inner circuit board through a thermocompression forming process. A circuit is provided to the laminated body 2 through etching as usual, fine irregularities are provided to the surface of the circuit through a photographic processing to enable the board 2 to be served as an inner circuit board. A glass nonwoven cloth containing 5-20% by weight of hydrated alumina is impregnated with epoxy resin varnish, which is dried up into a prepreg which serves as an inner insulating layer 5, and the insulating layer 5 is piled on both the sides of the inner circuit board 2. The surface of filler filled into the inner insulating layer 5 is treated with a silane coupling agent.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a multilayer printed wiring board that is incorporated into electronic or electrical equipment.

Conventional technology Considering the machinability of multilayer printed wiring boards, the base material constituting the substrate of the inner layer circuit board, the base material constituting the insulating layer between the inner layer circuit boards (inner layer insulation layer), and the inner layer A composite multilayer printed wiring board has been proposed in which a glass nonwoven fabric and a glass woven fabric are appropriately combined as a base material that constitutes an insulating layer between the circuit board and the circuit on the surface.

In this regard, the technique disclosed in Japanese Patent Application Laid-Open No. 61-40094 consists of a substrate of an inner layer circuit board made of an epoxy resin-impregnated glass woven fabric base material.

Then, two types of epoxy resin-impregnated glass non-woven fabric base materials (inner layer insulating layer) having different amounts of filler are interposed between the epoxy resin-impregnated glass woven fabric base material of the surface layer and the circuit board of the inner layer. It has become.

Problems to be Solved by the Invention However, since the above-mentioned multilayer printed wiring board uses a glass woven fabric base material for the inner layer circuit board and the surface layer, when multiple sheets are stacked and drilled, the drill It is easy to cause the hole position to shift. This positional shift becomes more noticeable in multilayer printed wiring boards stacked below. If the base material of the inner layer circuit board is replaced with a glass nonwoven fabric, the drilling processability will be improved, but the dimensional stability will be reduced. Since the circuits on the inner layer and the circuit on the surface are connected to each other through through holes after multilayering, it is a fatal problem that the inner layer circuit board undergoes dimensional changes during the manufacturing process.

In addition, in the technology in the above publication, two types of fillers with different blending amounts are used in combination for the epoxy resin-impregnated glass nonwoven fabric base material that is the inner insulating layer, taking into consideration dimensional stability, interlayer adhesion, and void generation. However, the work of creating multiple layers becomes complicated.

The object of the present invention is to use a glass woven fabric base material only for the surface layer, and use a glass nonwoven fabric as the base material for the inner layer, while achieving excellent dimensional stability and interlayer adhesion (particularly between the inner layer circuit surface and the inner layer insulating layer). The objective is to provide a multilayer printed wiring board with 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 whose surface of the circuit 1 is made finely uneven by chemical treatment is composed of a glass nonwoven fabric substrate impregnated with a thermosetting resin. The resin contains 30-50% by weight of inorganic filler.

(b) v of surface circuit 3! ! , the Ii layer (surface insulating layer 4) is composed of a glass woven fabric base material impregnated with a thermosetting resin.

(c) The insulating layer (inner insulating layer 5) between the surface insulating layer 4 and the inner circuit board is composed of a glass nonwoven fabric substrate impregnated with a thermosetting resin. The resin contains 5 to 20% inorganic filler.

Furthermore, when there are two or more inner layer circuit boards, the inner layer insulating layer 5 described in (c) above is also formed between the inner layer circuit boards.

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

The adhesion between the working inner circuit board and the inner insulating layer 5 is due to chemical bonding in the exposed portion of the surface of the substrate 2. However, in the part of the circuit 1, the resin of the inner insulating layer 5 flows during heating and pressure molding and enters the fine irregularities caused by the chemical treatment on the surface of the circuit 1, resulting in physical bonding due to the cast #1 product effect. This gives the adhesive strength.

When the base material of the inner insulating layer 5 is a glass woven fabric, the physical bonding force due to the anchoring effect is large, but when the base material is a glass nonwoven fabric, this bonding force is not sufficiently large. This is presumed to be due to the following reasons. In other words, since the glass nonwoven fabric is bulky and has many voids, the resin that flows during heating and pressure molding is preferentially used to fill the voids, and does not flow sufficiently into the fine irregularities on the surface of the circuit 1 ( It is assumed that this is because it is difficult to flow into the water.
Based on such knowledge, the multilayer printed wiring board according to the present invention contains an inorganic filler in the resin of the inner insulating layer 5, and the filler is sufficiently large compared to the fine irregularities on the surface of the circuit 1. The material particles deform the metal foil constituting the circuit 1 during heating and pressure molding, and are embedded in it. It is presumed that this anchoring effect, combined with the anchoring effect caused by the resin flowing into the fine irregularities on the surface of the circuit 1, makes it possible to maintain good adhesion between the circuit 1 and the inner insulating layer 5.

In this case, the anchoring effect cannot be exhibited unless the amount of inorganic filler contained in the resin of the inner insulating layer 5 reaches 5% by weight. On the other hand, when the amount of inorganic filler exceeds 20%,
The resin content that binds the filler particles to each other is small (and the filler particles tend to peel off between each other).
By setting the amount within the range of 20% by weight, good adhesion between the circuit 1 and the inner insulating layer 5 can be ensured.

In addition, the inorganic filler content in the resin of substrate 2 is 30%
If it does not reach 50% by weight, dimensional changes cannot be sufficiently suppressed.
If it exceeds this, the adhesion between the substrate 2 and the circuit 1 will decrease, and the insulation resistance will also deteriorate. Regarding the adhesion between the circuit 1 and the substrate 2, even if the back surface of the metal foil constituting the circuit 1 has a large mechanically coarse filler content, a sufficient anchoring effect of the resin can be expected.

EXAMPLES Hereinafter, examples of the present invention will be described together with comparative examples. An example of using hydrated alumina as an inorganic filler will be explained.
It has been confirmed that the same direction of 1 is exhibited when other inorganic fillers are used.

Examples 1 to 6, Comparative Examples 1 to 4 (1) Hydrated alumina treated with epoxy silane (epoxy silane is 1% based on the weight of hydrated alumina), 3% by weight (A) and 5% by weight, respectively. % (B), 10% by weight (
C), 15% by weight (D), 20% by weight (E), 25% by weight (F), 35% by weight (G), 40% by weight (11), 4
A bisphenol type epoxy resin containing 5% by weight (1) and 55% by weight (J) was prepared. This varnish was impregnated into a glass nonwoven fabric (41g/r+()) so that the resin content including hydrated alumina was 88% by weight and dried.
I got it.

The above epoxy resin varnish that does not contain hydrated alumina,
A glass woven fabric (215
g/rrf) and dried to obtain a prepreg (X).

(2) For each of the prepregs (I') to (J), 35 μ thick copper foil was placed on both sides of the 4 plies, and 0.8 m thick double-sided copper foil for inner layer circuit board was formed by heat and pressure molding. A laminate was obtained. The copper foil used was one whose side facing the prepreg was mechanically roughened to have irregularities.

This double-sided copper-clad laminate was etched using a conventional method to form a circuit, and a blackening treatment was applied to form fine irregularities on the circuit surface to form an inner layer circuit board.

(3) Select the inner insulating layer from prepregs (8) to (F). One ply of prepreg selected from (8) to (F), one ply of prepreg (x), and 18 μm thick copper foil were placed in this order on both sides of the inner layer circuit board, and were integrally formed by heating and pressure forming ( Thickness: 1.6mm).

(4) Holes were drilled in the integrated composite board according to a predetermined pattern, and through-hole plating was performed using a conventional method to connect the circuit in the inner layer to the copper foil on the surface.

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

Table 1 and Table 2 show the combinations of prepreg types used for the inner insulating layer.

! Table 181 Table 2 Example 7 A four-layer printed wiring board was prepared in the same manner as in Example 2, except that the hydrated alumina was not treated with epoxy silane.

Comparative Example 5 The substrate of the inner layer circuit board was made of prepreg (X) 4Bly. The rest was a four-layer printed wiring board similar to Example 2.

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

Table Machining conditions Drill diameter: 1,0 mm Rotation speed: 60.00 Orpm Feed rate: 50 μ/rev Also, the relationship between the filler content of the inner insulating layer and beer strength (adhesion between the circuit surface of the inner layer and the inner insulating layer) is shown in Figure 2. FIG. 3 shows 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. The dimensional change is
It is shown as the rate of dimensional change in the diagonal direction of the sample before and after processing and nitching → 0.5/150 processing. Insulation resistance was measured after treatment in a pressure cooker (2 atm, 121''C) for 8 hours.

Effects of the Invention As described above, the multilayer printed wiring board according to the present invention uses a glass nonwoven fabric as the base material of the inner insulating layer and sets the content of the inorganic filler within a specific range, so that the inner layer circuit and Maintains good adhesion of the inner insulating layer. This adhesion can be further improved by treating the filler with a silane coupling agent. Furthermore, although glass nonwoven fabric is used as the base material for the substrate of the inner layer circuit board, it has good dimensional stability and excellent machinability, and its industrial value is extremely large.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing an example of a six-layer circuit of a multilayer printed wiring board according to the present invention, and FIG. 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. l is the circuit, 2 is the substrate, 3 is the surface circuit, 4 is the surface insulation layer, 5 is the inner insulation layer

Claims (3)

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