JP2917579B2 - Multilayer printed wiring board - Google Patents

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 circuits in an outer layer and an inner layer.

[0002]

2. Description of the Related Art In a multilayer printed wiring board, an insulating layer of an inner circuit board is made of a glass woven cloth impregnated with an epoxy resin or a polyimide resin. Is generally made of a glass woven fabric. A composite type multilayer printed wiring board in which a glass woven fabric is partially replaced with a glass nonwoven fabric has also been proposed.

[0003]

However, in the case of using glass woven fabric, it is not possible to satisfactorily fill the unevenness formed by a portion with a circuit and a portion without a circuit on the surface of the inner circuit board with a resin, and voids are formed. Likely to happen. Also,
Since all layers are made of glass woven fabric, misalignment is likely to occur when drilling holes, and the wear of the drill blades is significant. May be invited. Although the composite type does not have such a problem, it has a large thermal expansion in the plane direction, and thus the reliability as a printed wiring board on which components are surface-mounted is put. The problem to be solved by the present invention is to suppress the generation of voids in the inner layer of the multilayer printed wiring board, improve the drill workability, and reduce the thermal expansion in the plane direction.

[0004]

In order to solve the above problems, in a multilayer printed wiring board according to the present invention, the insulating layer (a) of the outer layer circuit 1 is a glass woven fabric 2 impregnated with a thermosetting resin,
The insulating layer (b) constituting the inner layer circuit board 3 and the adhesive layer between the inner layer circuit board 3 and the insulating layer (a) are made of a thermosetting resin impregnated glass fiber / aromatic polyamide fiber mixed nonwoven fabric 4. (FIG. 1, wiring board of four-layer circuit). As for the circuit having more than four layers, as shown in FIG. 2, the insulating layer (a) of the outer layer circuit 1 is a glass woven fabric 2 impregnated with a thermosetting resin and the insulating layer constituting the inner layer circuit board 3 (B) The adhesive layer between the inner circuit board 3 and the insulating layer (a) and the adhesive layer between the inner circuit boards are a thermosetting resin-impregnated glass fiber / aromatic polyamide fiber mixed nonwoven fabric 4. .

[0005]

The multilayer printed wiring board according to the present invention uses a non-woven fabric for the inner layer, so that it has good drill workability. Since a large amount of resin can be held in the non-woven fabric, the unevenness formed by the circuit is filled with the resin. Thus, generation of voids can be suppressed. Aromatic polyamide fiber, which is a constituent material of the nonwoven fabric, has a negative coefficient of linear expansion and acts to suppress thermal expansion in the planar direction of the wiring board.

[0006]

【Example】

Example 1 A prepreg A was obtained by impregnating and drying 41 g / m ² of a mixed nonwoven fabric (glass fiber / aromatic polyamide fiber = 9/1 by weight ratio) with a bisphenol-type epoxy resin. Also, 21
A prepreg B was obtained by impregnating and drying a 5 g / m ² glass woven fabric in the same manner. A 35 μm thick copper foil was placed on both sides of the prepreg A4 ply, and a 0.8 mm thick double-sided copper-clad board was obtained by heating and pressing. This was processed by etching in a conventional manner to form a circuit, which was used as an inner circuit board. The circuit surface is subjected to a chemical treatment for the next bonding step. One ply of prepreg A on both sides of the inner layer circuit board, and further prepreg B
Was placed on one ply, a copper foil having a thickness of 18 μm was placed on the outermost surface, and integrated by heat and pressure molding. 1.6m in total thickness
m. Drill holes are drilled at predetermined positions, plated with through holes, and outer layer circuits are formed by etching.
It was a layered wiring board. The characteristics are shown in Table 1.

Conventional Example 1 A prepreg C was obtained by impregnating and drying bisphenol-type epoxy resin on a 41 g / m ² glass nonwoven fabric. A copper foil having a thickness of 35 μm was placed on both sides of the prepreg C4 ply, and a double-sided copper-clad board having a thickness of 0.8 mm was obtained by heating and pressing. This was processed by etching in a conventional manner to form a circuit, which was used as an inner circuit board. The circuit surface is subjected to a chemical treatment for the next bonding step. Pre-preg C on both sides of the inner circuit board
Was placed on one ply, prepreg B was further placed on one ply, and a copper foil having a thickness of 18 μm was placed on the outermost surface, and integrated by heating and pressing. The total thickness is 1.6 mm. Drill holes were drilled at predetermined positions, through-hole plating was performed, and outer layer circuits were formed by etching to obtain four-layer wiring boards. The characteristics are shown in Table 1.

Conventional Example 2 A copper foil having a thickness of 35 μm was placed on both sides of a prepreg B4 ply, and a double-sided copper-clad board having a thickness of 0.8 mm was obtained by heating and pressing. This was processed by etching in a conventional manner to form a circuit, which was used as an inner circuit board. The circuit surface is subjected to a chemical treatment for the next bonding step. Two layers of prepreg B were placed on both sides of the inner circuit board, and a copper foil having a thickness of 18 μm was placed on the outermost surface, and integrated by heating and pressing. The total thickness is 1.6 mm. Drill holes were drilled at predetermined positions, through-hole plating was performed, and outer layer circuits were formed by etching to obtain four-layer wiring boards. The characteristics are shown in Table 1.

[0009]

[Table 1]

In Table 1, the conditions for drilling are a drill diameter of 1.0 mm, 6000 rpm, and 50 μ / rev. Drill wear is measured after three multilayer printed wiring boards are drilled and 1500 holes are hit. The drill hole position accuracy was indicated by the degree of positional deviation from a predetermined position of the first and third sheets when three holes were drilled. The coefficient of thermal expansion is from 30 to 80 ° C., and was measured by the TMA method.

[0011]

As is clear from Table 1, the multilayer printed wiring board according to the present invention has low drill wear during drilling and small hole wall roughness, so that through-hole plating can be uniformly applied. it can. Since the occurrence of voids in the inner layer can also be suppressed, the reliability can be improved with respect to the increase in the density of the inner layer circuit. Since the thermal expansion in the plane direction is small, it is possible to suppress the occurrence of cracks due to the thermal shock of the soldered portion of the surface mounted component. In addition, glass fiber /
The aromatic polyamide fiber mixed nonwoven fabric is lighter than any of the glass woven fabric and the glass nonwoven fabric, and can reduce the weight of the multilayer printed wiring board.

[Brief description of the drawings]

FIG. 1 is an explanatory sectional view showing an embodiment according to the present invention.

FIG. 2 is an explanatory sectional view showing another embodiment according to the present invention.

[Explanation of symbols]

 1 is an outer layer circuit 2 is a glass woven cloth 3 is an inner layer circuit board 4 is a mixed nonwoven fabric

Claims (2)

(57) [Claims] 1. A multilayer printed wiring board having a circuit in an inner layer and an outer layer, wherein the insulating layer (a) of the outer layer circuit is a woven glass impregnated with a thermosetting resin, and the insulating layers (b) constituting the inner layer circuit board; And a multilayer printed wiring board in which an adhesive layer between the inner circuit board and the insulating layer (a) is a nonwoven fabric made of a thermosetting resin-impregnated glass fiber / aromatic polyamide fiber. 2. A multilayer printed wiring board having a circuit in an inner layer and an outer layer, wherein the insulating layer (a) of the outer layer circuit is a glass woven fabric impregnated with a thermosetting resin, and the insulating layers (b) constituting the inner layer circuit board; A multilayer printed wiring board, wherein the adhesive layer between the inner circuit board and the insulating layer (a) and the adhesive layer between the inner circuit boards are nonwoven fabrics mixed with a thermosetting resin-impregnated glass fiber / aromatic polyamide fiber.