JPH0582971A - Multilayered printed wiring board - Google Patents

Abstract

PURPOSE:To improve the solder connection reliability between the surface mounted parts and circuit of a multilayered printed wiring board against thermal shocks and temperature rise-drop cycles encountered when the wiring board is used for many years. CONSTITUTION:The insulating later of the internal-layer circuit board of this multilayered printed wiring board is constituted of a piece of woven cloth 1 of aromatic polyamide fibers impregnated with an epoxy resin and the adhesive layer between the internal-layer circuit board and copper foil 2 which becomes a surface circuit is constituted of a piece of nonwoven cloth 3 of aromatic polyamide fibers impregnated with an epoxy resin. The nonwoven cloth 3 is used as adhesive layers when six or more layers of internal-layer circuit boards are stuck to each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer printed wiring board having a base material made of aromatic polyamide fiber as an insulating layer.

[0002]

2. Description of the Related Art In a multilayer printed wiring board, an insulating substrate of an inner layer circuit board is made of a glass woven cloth impregnated with epoxy resin, polyimide, etc., and an adhesive layer for adhering the inner layer circuit boards to each other is the epoxy resin or polyimide. It is generally composed of a glass woven fabric impregnated with the like.

[0003]

However, in a multilayer printed wiring board in which the conventional insulating layers are all made of epoxy resin or polyimide resin impregnated glass woven cloth, the insulating layer has a coefficient of thermal expansion in the plane direction of (12). ~ 18) ×
It is 10 to ⁶ / ° C. In recent years, surface mounting of leadless chip components has become the mainstream for component mounting on printed wiring boards, but the thermal expansion coefficient of leadless chip components is (2
7) × 10 ⁶ / ° C., and there is a problem that cracks occur at the solder joints of the mounted components due to mismatch with the thermal expansion coefficient of the insulating layer. The problem to be solved by the present invention is to bring the coefficient of thermal expansion in the plane direction of the multilayer printed wiring board close to the coefficient of thermal expansion of the leadless chip component to enhance the reliability of the solder joint of the leadless chip component. ..

[0004]

In order to solve the above-mentioned problems, in a multilayer printed wiring board according to the present invention, an epoxy resin-impregnated aromatic polyamide fiber woven fabric 1 is used as an insulating layer constituting one inner layer circuit board, Copper foil 2 which becomes the outer layer circuit adjacent to this
It is characterized in that the adhesive layer with is made of an epoxy resin-impregnated aromatic polyamide fiber nonwoven fabric 3. Further, the adhesive layer for adhering the inner circuit boards to each other and the adhesive layer between the inner circuit board and the outer copper foil are made of epoxy resin-impregnated aromatic polyamide fiber nonwoven fabric 3 and the insulating layer constituting the inner circuit board is made of epoxy resin. It is characterized in that it is the impregnated aromatic polyamide fiber woven fabric 1.

[0005]

According to the present invention, since the insulating layer is formed by impregnating an aromatic polyamide fiber base material having a negative linear expansion coefficient with an epoxy resin, the linear expansion coefficient of the insulating layer is set to the linear expansion coefficient of the chip component ( 2 to 7) × 10 ⁶ / ° C. can be approximated. There are two types of forms of the aromatic polyamide fiber base material: woven fabric and non-woven fabric. When a woven fabric is used, the dimensional change rate after the heat treatment process is small, but there is a problem that the circuit filling property as an adhesive layer is poor, and it is expensive. On the other hand, when a non-woven fabric is used, it is advantageous in terms of circuit filling property and cost, but there is a problem that the dimensional change rate after the heat treatment process becomes large. Therefore, by using an epoxy resin-impregnated aromatic polyamide fiber woven fabric as the insulating layer of the inner layer circuit board and an epoxy resin-impregnated aromatic polyamide fiber woven fabric as the adhesive layer, a multilayer print composed only of the epoxy resin-impregnated aromatic polyamide fiber woven fabric As compared with the wiring board, the circuit fillability of the inner layer circuit board and the surface smoothness of the multilayer printed wiring board are excellent. Further, by using the epoxy resin-impregnated aromatic polyamide fiber woven cloth for the insulating layer of the inner circuit board, the dimensional stability is superior to the multilayer printed wiring board composed only of the epoxy resin-impregnated aromatic polyamide fiber nonwoven fabric. Becomes

[0006]

EXAMPLES Example A commercially available aromatic polyamide fiber woven fabric was coated with a brominated bisphenol A type epoxy resin in an amount of 50 wt% by a conventional method.
% So as to obtain an epoxy resin-impregnated aromatic polyamide fiber woven fabric (prepreg A). Similarly, a commercially available aromatic polyamide fiber non-woven fabric was coated with a brominated bisphenol A type epoxy resin in an amount of 50 wt% by a conventional method.
To obtain an epoxy resin-impregnated aromatic polyamide fiber nonwoven fabric (prepreg B). Place prepreg A on both sides of 2-ply 35μm copper foil, sandwich it with a mirror plate, and heat and pressurize it by a conventional method to 0.4mm.
A thick double-sided copper clad plate was obtained. This was etched by a conventional method to form a circuit, and the circuit surface was blackened to obtain an inner layer circuit board having a thickness of 0.4 mm. Two plies of prepreg B were placed on both sides of the inner layer circuit board, 18 μm copper foil was further laid on both sides of the prepreg B, and they were integrated by heating and pressurizing by a conventional method. The total thickness is 0.8 mm. This was drilled according to a predetermined pattern, and through-hole plating was carried out by a conventional method. Then, an outer layer having a predetermined pattern was etched by a conventional method to obtain a multilayer printed wiring board having four layers.

Comparative Example 1 In the process of the above example, 1 ply of prepreg A was used instead of prepreg B, and the other examples were
In the same manner as described above, a 4-layer multilayer printed wiring board having a thickness of 0.8 mm was obtained.

Comparative Example 2 In the process of the above example, 4 plies of prepreg B were used in place of prepreg A, and the same procedure as in example 1 was carried out to obtain a 0.8-mm-thick 4-layer multilayer printed wiring board. It was

Conventional Example A commercially available glass fiber woven fabric was impregnated with a brominated bisphenol A type epoxy resin by a conventional method so that the resin adhesion amount was 40 wt%, and dried to obtain an epoxy resin-impregnated glass woven fabric (prepreg C). Obtained. Similarly, the resin adhesion amount is 45 wt%
A glass woven fabric (prepreg D) impregnated and dried to obtain an epoxy resin was obtained. Place 35μm copper foil on both sides of prepreg C with two plies, sandwich it with a mirror plate, and heat and pressurize by a conventional method to 0.4mm.
A thick double-sided copper clad plate was obtained. This was etched by a conventional method to form a circuit, and the circuit surface was blackened to obtain an inner layer circuit board having a thickness of 0.4 mm. One ply of prepreg D was placed on each side of the inner layer circuit board, and 18 μm copper foil was further laid on both sides of the prepreg D. The total thickness is 0.8 mm. This was drilled according to a predetermined pattern, and through-hole plating was performed by a conventional method. Then, an outer layer having a predetermined pattern was etched by a conventional method to obtain a multilayer printed wiring board having four layers.

Comparative Example 3 In the process of the above-mentioned conventional example, two plies of prepreg B were used in place of the prepreg D, and the other steps were the same as in the conventional example to obtain a multilayer printed wiring board of four layers having a thickness of 0.8 mm. It was

Table 1 shows the characteristics of the multilayer printed wiring boards in each of the examples, comparative examples and conventional examples.

[0012]

[Table 1]

(Note 1) The number of measurements n = 30, and the number is the number of voids in 30. (Note 2) The dimensional change rate of the inner layer circuit board in the finished multilayer printed wiring board product, based on the dimensions of the copper clad board for the inner layer circuit board. (Note 3) Coefficient of linear expansion only for the insulating layer without copper foil in the inner layer. (Note 4) Evaluation of surface copper migration of the outermost layer. (Note 5) Pressure cooker treatment: 121 ° C, 2 at
m ◯: No migration occurred ×: Migration occurred In the above example, the circuit has four layers, but two inner layer circuit boards are used and the inner layer circuit boards are pre-preg B.
The same effect could be confirmed in the case of the 6-layer circuit board adhered by.

[0014]

As described above, in the aromatic polyamide fiber-based multilayer printed wiring board according to the present invention, epoxy resin-impregnated aromatic polyamide fiber woven cloth is used for the insulating layer of the inner circuit board, and epoxy is used for the multilayer adhesive layer. Since it is decided to use a resin-impregnated aromatic polyamide fiber nonwoven fabric, compared to a multilayer printed wiring board using only an epoxy resin-impregnated aromatic polyamide fiber woven fabric, it has excellent circuit filling properties and surface smoothness.
Smaller dimensional change than a multilayer printed wiring board using only epoxy resin-impregnated aromatic polyamide fiber non-woven fabric, and smaller linear expansion coefficient than a conventional multilayer printed wiring board using only epoxy resin-impregnated glass woven fabric. Is excellent at. In addition to this, since the insulating layer in contact with the outermost copper foil is an epoxy resin-impregnated aromatic polyamide fiber nonwoven fabric, there is an effect that copper migration can be suppressed.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a layer structure when a multilayer printed wiring board is molded.

[Explanation of symbols]

 1 is woven fabric 2 is copper foil 3 is non-woven fabric

Claims (2)

[Claims] 1. An insulating layer constituting one inner layer circuit board is made of an epoxy resin-impregnated aromatic polyamide fiber woven cloth, and an adhesive layer with a copper foil adjacent to this which becomes an outer layer circuit is epoxy resin impregnated aromatic polyamide fiber. Multilayer printed wiring board made of non-woven fabric. 2. The insulating layer base material is aromatic polyamide fiber,
Epoxy resin impregnated aromatic polyamide fiber non-woven fabric is used for the adhesive layer that adheres the inner circuit boards to each other and the adhesive layer between the inner circuit board and the copper foil that forms the outer circuit. A multi-layer printed wiring board, which is made of a woven polyamide fiber group.