JPH03219692A - Multilayer printed-wiring board and its manufacture - Google Patents

Abstract

PURPOSE:To enable a thermal coefficient of expansion of an insulation layer in thickness direction to be kept to a small value and a through-hole conduction reliability to be improved by setting a surface circuit and one surface of an inner-layer circuit to an insulation layer consisting of an aramid fiber non-woven cloth. CONSTITUTION:A resin-dipped glass fiber woven cloth layer 5 or a resin-dipped glass fiber non-woven cloth layer 5 is included between a circuit surface of an outer-layer plate 3 where a circuit 2 is formed on a single surface of a resin-dipped aramid fiber non-woven insulation layer 1 and an inner-layer plate 4 where the circuit 2 is formed on both surfaces of the resin-dipped aramid fiber non-woven cloth insulation layer 1 for forming one piece with heated press formation. The surface circuit is formed after that. In the case of a multilayer printed-wiring board with a four-layer circuit, the resin-included glass fiber woven layer 5 or the resin-included glass fiber non-woven cloth layer 5 is included between the circuit surfaces of two outer-layer plates 3 where the circuit 2 is formed on a single surface of the resin-dipped aramid fiber non-woven insulation layer 1 for forming one piece with heated press formation.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a multilayer printed wiring board and a method for manufacturing the same.

Conventional technology In recent years, as the performance of electronic devices has improved, the multilayer printed wiring boards used in these devices have been required to have higher signal speeds and higher wiring densities, and the accompanying surface mounting method for mounting components. There is a need to adapt to the transition.

Conventional multilayer printed wiring boards use glass fiber woven fabric or glass fiber nonwoven fabric impregnated with a thermosetting resin such as epoxy resin or polyimide as an insulating layer for circuits in the surface layer and inner layer. Therefore, the dielectric constant and coefficient of thermal expansion in the planar direction of the insulating layer are large, and the insulating layer cannot sufficiently cope with higher speed signals and surface mounting methods for mounting components.

In addition, in order to reduce the dielectric constant and thermal expansion coefficient in the plane direction, we used an aramid fiber woven fabric or aramid fiber nonwoven fabric that has a small dielectric constant and a negative linear thermal expansion coefficient in the length direction of I/11 fibers. It is also being considered to form an insulating layer by impregnating it with a thermosetting resin such as epoxy resin or polyimide. However, in this case, there is a problem that the coefficient of thermal expansion in the thickness direction of the insulating layer increases, and the reliability of conduction of the through holes is insufficient.

Problems to be Solved by the Invention The problems to be solved by the present invention are to satisfy the requirements for high signal speed and surface mounting of components by having a low dielectric constant and a low coefficient of thermal expansion in the plane direction of the insulating layer, and to achieve reliable through-hole conduction. An object of the present invention is to provide a multilayer printed wiring board with excellent properties.

Means for Solving the Problems In order to solve the above problems, in the multilayer printed wiring board according to the present invention, one surface layer circuit and one surface of the inner layer circuit are in contact with a resin-impregnated aramid fiber nonwoven fabric insulating layer. The other surface of the inner layer circuit is characterized in that it is in contact with a resin-impregnated glass fiber woven fabric insulating layer or a resin-impregnated glass fiber non-woven fabric insulating layer.

This multilayer printed wiring board is manufactured with a configuration as shown in FIG.

Resin-impregnated glass is inserted between the circuit surface of the outer layer board 3 in which the circuit 2 is formed on one side of the resin-impregnated aramid fiber non-woven fabric insulation layer 1 and the inner layer plate 4 in which the circuit 2 is formed on both sides of the resin-impregnated aramid fiber non-woven fabric insulation layer 1. Thereafter, circuits on six surfaces, which are integrated by heating and pressure molding with the fiber woven fabric M5 or the resin-impregnated glass fiber nonwoven fabric layer 5 interposed therebetween, are formed as appropriate.

In the case of a multilayer printed wiring board with four layers of circuits, the circuit 2 is formed on one side of the resin-impregnated aramid fiber nonwoven fabric N edge layer 1.
A resin-impregnated glass fiber woven fabric layer 5 or a resin-impregnated glass fiber non-woven fabric layer 5 is interposed between the circuit surfaces of the two outer layer boards 3 and integrated by heating and pressure molding.

Of course, when a plurality of inner plates 4 are used, a resin-impregnated glass fiber woven fabric layer 5 or a resin-impregnated glass fiber non-woven fabric layer 5 is interposed between the inner plates and they are integrated by heating and pressure molding.

Function In the multilayer printed wiring board according to the present invention, the circuit on one surface and one surface of the circuit on the inner layer are insulating layers made of aramid fiber nonwoven fabric, so that the dielectric constant can be reduced.

In particular, the circuit on the first surface has a great effect in responding to high-speed signals, and since it uses aramid fiber, it is extremely durable.
The coefficient of thermal expansion in the plane direction of the FIJ can be suppressed to a low level.

On the other hand, since the inner insulating layer includes a layer of glass fiber woven fabric or glass fiber nonwoven fabric, the coefficient of thermal expansion in the thickness direction of the insulating layer can also be suppressed to a small value, thereby increasing the reliability of through-hole conduction.

Examples The resins used to implement the multilayer printed wiring board according to the present invention are thermosetting resins such as epoxy resins, phenolic resins, and polyimides, and heat-resistant thermoplastic resins such as fluororesins, polyetherketones, and polyethersulfones. be. However, it is desirable to use the same type of resin for the aramid fiber nonwoven fabric and the glass fiber woven fabric or the nonwoven fabric to be impregnated in consideration of mutual adhesiveness.

The amount of resin impregnated into the aramid fiber nonwoven fabric is desirably adjusted to 40 to 70% by volume.

If the amount of impregnation is small, voids will occur in the insulating layer, or the adhesive strength between the metal foil forming the @ path and the insulating layer will be insufficient. On the other hand, if the amount of impregnation is too large, the coefficient of thermal expansion in the planar direction of the insulating layer will increase, making it difficult to support surface mounting of components.

The thickness ratio of the insulating layer made of resin-impregnated aramid fiber non-woven fabric and the insulating layer made of resin-impregnated glass fiber woven fabric or resin-impregnated glass fiber non-woven fabric is not particularly limited, but it depends on the dielectric constant of the insulating layer and It is determined as appropriate depending on which is more important: keeping the coefficient of thermal expansion in the planar direction low or ensuring through-hole conduction reliability. Keeping the dielectric constant and thermal expansion coefficient of the insulating layer low depends on the thickness of the insulating layer made of resin-impregnated aramid fiber nonwoven fabric.

Through-hole conduction reliability depends on the thickness of the insulating layer made of resin-impregnated glass fiber fabric or resin-impregnated glass fiber nonwoven fabric.

Example 1 (Manufacture of prepreg) Glass fiber woven fabric (basis weight 107 g/rd) was impregnated with bisphenol type epoxy resin varnish and dried.

Innnnn impregnated amount: 5 strands Also, the resin varnish was applied to an aramid fiber nonwoven fabric (basis weight: 6
0g/rrf) and dried to a resin impregnated amount of 60% by volume.
A prepreg CB) was obtained.

(Manufacture of outer layer board) Copper foil with a thickness of 35 μm was placed on both sides of 4 plies of prepreg (B), and this was molded under heat and pressure to obtain a double-sided network-covered laminate with a thickness of 0.4 wm. A copper foil circuit was formed on only one side using a standard etching method, and the circuit surface was blackened to form an outer layer board.

(Manufacture of inner layer board) Copper foil with a thickness of 70 μm was placed on both sides of the prepreg (B) 4-braid, and this was molded under heat and pressure to obtain a double-sided network-covered laminate with a thickness of 0.4 m. Copper foil circuits are formed on both sides using the standard etching method.

The circuit surface was blackened to form an inner layer board.

(Manufacture of multilayer printed wiring board) The two outer layer boards are placed facing each other with the circuit side facing inside, and the inner layer board is placed between them, and one prepreg A is interposed between the outer layer board and the inner layer board. , were integrated by heating and pressure molding to form a 1.6-thick multilayer printed wiring board.

Example 2 (Manufacture of outer layer board) Copper foil with a thickness of 35 μm was placed on both sides of two plies of prepreg (B), and this was molded under heat and pressure.

A double-sided steel clad laminate with a thickness of 0.2 m was obtained. A copper foil circuit was formed on only one side using a standard etching method, and the surface was blackened to form an outer layer board.

(Manufacture of multilayer printed wiring board) The two outer layer boards were placed facing each other with the circuit side facing inside, and the one inner layer board used in Example 1 was placed between them, and prepreg A was placed between the outer layer board and the inner layer board. Two pieces are interposed and integrated by heating and pressure molding.

It was made into a multilayer printed wiring board of 1.6 m+/l.

Comparative Example 1 The two outer layer plates used in Example 1 were placed facing each other with the circuit side facing inside, and the inner layer plate used in Example 1 was placed between them. Prepreg B was placed between the outer layer plate and the inner layer plate. With two pieces in between. Integrated by heating and pressure molding, l. A multilayer printed wiring board with a thickness of 6 m and 1 m was used.

Comparative Example 2 (Manufacture of outer layer board) Copper foil with a thickness of 35 μm was placed on both sides of 2 plies of prepreg (A), and this was molded under heat and pressure to obtain a double-sided mesh laminate with a thickness of 0.4 mm. ．． A copper foil circuit was formed on only one side using a standard etching method, and the circuit surface was blackened to form an outer layer board.

(Manufacture of inner layer board) Copper foil with a thickness of 70 μm was placed on both sides of 2 plies of prepreg (A), and this was heated and pressed to obtain a double-sided steel clad laminate with a thickness of 0.4-. A copper foil circuit is formed on both sides using the standard etching method, and the circuit surface is blackened.
It was used as an inner layer plate.

(Manufacture of multilayer printed wiring board) The two outer layer boards are placed facing each other with the circuit side facing inside, and the one inner layer board is placed between them, with one sheet of prepreg A interposed between the outer layer board and the inner layer board. , and were integrated by heat and pressure molding to form a 1.6-thick multilayer printed wiring board.

For the multilayer printed wiring boards in the above examples and comparative examples, holes were drilled according to a predetermined pattern, and through-hole plating was performed to connect the circuits in the inner layer and the circuits on the surface. Thereafter, the copper foil on the surface was etched using a standard method to form a circuit on the surface.

Table 1 shows the characteristics of each of these multilayer printed wiring boards.

Table 1 In Table 1, the surface mount soldering reliability is determined by soldering an IC chip to a circuit on one surface at 80°C for 1 hour.
A thermal cycle test was conducted at ℃ for 1 hour, and the number of cycles until cracks appeared in the soldered part was determined. In addition, through-hole conduction reliability is measured at 260°C on a multilayer printed wiring board before components are mounted.

A hot oil test was conducted for 10 seconds (silicon oil) and -20°C for 20 seconds (silicon oil), and the number of cycles until the conduction resistance value of the through hole increased by 10% was determined.

Effects of the Invention As described above, the multilayer printed wiring board according to the present invention has a small dielectric constant and can handle high speed signals. Furthermore, the soldering reliability of surface mount components and the continuity reliability of through-holes during cooling and heating cycles are also excellent. Furthermore, since the surface insulating layer is made of non-woven fabric, the surface roughness is small.

Suitable for forming high-density thin wire circuits.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the process of making one circuit multilayered in an embodiment according to the present invention. 1: Resin-impregnated aramid fiber nonwoven fabric insulation layer 2: Circuit 3:
Outer layer board 4: Inner layer board 5: Resin-impregnated glass fiber woven fabric layer or resin-impregnated glass fiber non-woven fabric layer

Claims (3)

[Claims] (1) In a multilayer printed wiring board that has a circuit on the surface layer and an inner layer via an insulating layer, the circuit on the surface layer and one side of the circuit on the inner layer are in contact with the resin-impregnated aramid fiber nonwoven fabric insulating layer, and the circuit on the inner layer A multilayer printed wiring board characterized in that the other surface is in contact with a resin-impregnated glass fiber woven fabric insulating layer or a resin-impregnated glass fiber non-woven fabric insulating layer. (2) Between the circuit surface of the outer layer board, which has a circuit formed on one side of the resin-impregnated aramid fiber nonwoven fabric insulation layer, and the inner layer board, which has circuits formed on both sides of the resin-impregnated aramid fiber nonwoven fabric insulation layer,
A method for producing a multilayer printed wiring board, which comprises integrating a resin-impregnated glass fiber woven fabric layer or a resin-impregnated glass fiber non-woven fabric layer by heat and pressure molding. (3) A resin-impregnated glass fiber woven fabric layer or a resin-impregnated glass fiber non-woven fabric layer is interposed between the circuit surfaces of two outer layer boards in which a circuit is formed on one side of the resin-impregnated aramid fiber non-woven fabric insulating layer, and heated and pressurized. A method for manufacturing a multilayer printed wiring board, which is characterized by being integrated by molding.