JPH08228076A - Manufacture of multilayer printed wiring board - Google Patents

Abstract

PURPOSE: To provide a method of manufacturing a multilayer wiring board, in which a measling generated at the time of multilayer bonding is suppressed, when a required number of prepregs are superposed to the upper and lower sections of an internal-layer circuit board, and metallic foils are stacked on both sides of the prepregs and heated and pressure-molded. CONSTITUTION: In the manufacture of a multilayer printed wiring board, in which a required number of prepregs, in which a base material is impregnated with resin varnish, are superposed to the upper and lower sections of an internal-layer circuit board, in which circuit patterns are formed on the front and the rear, while metallic foils are stacked on both sides of the prepregs and heated and pressure-molded, the internal-layer circuit board is pressed at molding pressure of 40-60kg/cm<2> until the resin impregnated to the above- mentioned base material is melted, and pressed at 10-20kg/cm<2> until the resin is cured and cooled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a multilayer printed wiring board using an inner layer circuit board.

[0002]

2. Description of the Related Art Conventionally, in a multilayer printed wiring board, a required number of prepregs in which a base material such as glass cloth is impregnated with a resin varnish such as epoxy resin are provided above and below an inner layer circuit board having circuit patterns formed on the front and back sides. It is manufactured by stacking metal foil such as copper foil on both sides of the foil, and heat-pressing the foil.

In this method of manufacturing a multilayer printed wiring board, the pressure control of the heating and pressurizing is performed by setting the initial forming pressure to a low pressure, increasing the pressure at a timing with temperature, the melt viscosity of the resin as an index, and applying the high pressure. A control method is used in which pressure is applied and pressure is applied at a low pressure during the period when the resin is cured.

In this pressure control method, since the timing for changing the pressure varies depending on the thickness and circuit pattern of the inner layer circuit board that constitutes the multilayer printed wiring board to be heat-pressed and molded, and the number of prepregs, the pressure control method is varied. It was difficult to control it in the manufacturing method of a small amount of multilayer printed wiring boards.

If the timing of pressurization is impaired, the resin of the prepreg heated under pressure is melted and further hardened to cause curing shrinkage, or the resin shrinks further during the cooling stage, resulting in local distortion. However, peeling occurred at the intersection of the warp yarn and the weft yarn constituting the glass cloth base material, and the measling occurred.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object thereof is to stack a required number of prepregs above and below an inner layer circuit board, and further,
It is an object of the present invention to provide a method for manufacturing a multilayer printed wiring board, which suppresses the measling that occurs during the multi-layered bonding in which metal foils are superposed on both sides and subjected to heat and pressure molding.

[0007]

A method for manufacturing a multilayer printed wiring board according to a first aspect of the present invention is a prepreg in which a base material is impregnated with a resin varnish above and below an inner layer circuit board having a circuit pattern formed on the front and back. In the method for producing a multilayer printed wiring board, in which the required number of sheets are stacked, metal foils are stacked on both sides, and this is heated and pressed, the molding pressure is 40 to 60 kg / cm until the resin impregnated in the base material is melted. Press at ² , then 10-60 until the resin hardens and cools
It is characterized by pressurizing at kg / cm ² .

[0008]

According to the method for manufacturing a multilayer printed wiring board according to the present invention, a required number of prepregs in which a base material is impregnated with a resin varnish are stacked on top and bottom of an inner layer circuit board having circuit patterns formed on the front and back sides, and a metal foil is formed. Overlap on both sides,
In the method for producing a multilayer printed wiring board in which this is heat-pressed, a molding pressure is applied at 40 to 60 kg / cm ² until the resin impregnated in the base material is melted.
The heat transmitted from the hot platen to the prepreg through the metal plate has good conductivity, and the resin impregnated in the prepreg is uniformly melted and flows, and the bubbles contained in the melted resin are extruded by this flow. In addition, this pressure is 40kg / cm ²
If it is lower, the resin does not flow sufficiently, so that the molded multilayer printed wiring board is scratched. Furthermore, when the pressure is higher than 60 kg / cm ² , the resin flow becomes large, and further,
A load is applied to the base material and cracks occur, causing measling.

Further, thereafter, pressure is applied at 10 to 20 kg / cm ² until the resin is cured and cooled, so that the strain generated by the pressure is released. If this pressure is higher than 20 kg / cm ² , the strain cannot be released, a load is applied to the base material, cracks occur, and measling occurs. Further, if this pressure is lower than 10 kg / cm ² , the cooling action does not act uniformly and warpage occurs.

The present invention will be described in detail below with reference to an embodiment.

[0011]

【Example】

Example 1 100 μm thick glass cloth substrate (Nittobo Co., Ltd .: WEA)
116E) was impregnated with an epoxy resin and dried to obtain a prepreg in which the resin was semi-cured. Two pieces of this prepreg are piled up, copper foil of 70 μm is piled up on both sides, sandwiched between metal plates, placed between a pair of hot plates, and heated at a temperature of 180 ° C. and a pressure of 40 kg / cm ² for 90 minutes. Pressurized to obtain a double-sided copper clad laminate having a thickness of 0.2 mm.

Further, this double-sided copper clad laminate was subjected to an etching treatment to form an inner layer circuit pattern, and the formed inner layer circuit pattern was subjected to a blackening treatment to form an inner layer circuit board.

Then, the obtained inner layer circuit board is set to 0.15 m.
m of the above prepregs are stacked, and the thickness is 18μ
An object to be pressure-bonded with copper foil of m on its outside is sandwiched between a pair of metal plates, and a plurality of groups of objects to be sandwiched between the pair of metal plates are sandwiched between a pair of heating plates for heating. Pressure molding was performed.

The molding conditions are shown in the profile diagram of FIG.
First, the pressure is 50 kg / cm ²And this pressure
The temperature of the product sandwiched between the metal plates is 150 ℃
Hold until reached. And the product temperature is 150 ℃
Pressure reaches 15kg / cm²Lowers the temperature
Is also lowered and cooled, and heat and pressure molding is performed to form a multilayer of 4 layers.
A printed wiring board was obtained.

In the figure, the broken line shows the pressure profile, and the solid line shows the temperature profile.

A test piece of 300 × 500 mm was prepared by using the obtained multilayer printed wiring board, the copper foil on the surface was removed by etching, and residual voids and measling generated at the intersections of the warp and weft of the glass cloth. Occurrence was confirmed by visual inspection and a magnifying glass, but no place where measling and residual voids were generated could be confirmed.

The surface roughness of the laminated plate obtained above was measured using Surfcom, manufactured by Tokyo Seimitsu Co., Ltd., and the maximum value was determined to be 3.0 to 4.0 mm. Table 1 shows the results.

Comparative Example 1 In the same manner as in Example 1, a double-sided copper-clad laminate having a thickness of 0.2 mm was formed and further subjected to etching treatment to obtain an inner layer circuit board having a signal circuit, a power supply circuit and a ground circuit. Formed.

Then, 0.15 m of the obtained inner layer circuit board
m of the above prepregs are stacked, and the thickness is 18μ
An object to be pressure-bonded with copper foil of m on its outside is sandwiched between a pair of metal plates, and a plurality of groups of objects to be sandwiched between the pair of metal plates are sandwiched between a pair of heating plates for heating. Pressure molding was performed.

The molding condition is that the pressure is 5 kg / cm ²
This pressure was maintained until the temperature of the product sandwiched between the metal plates reached 150 ° C.

When the temperature of the product reached 150 ° C., the pressure was increased to 50 kg / cm ² , the temperature was lowered and the product was cooled, and then the pressure was released to obtain a multilayer printed wiring board of four layers.

A test piece of 300 × 500 mm was prepared from the obtained laminated plate, and the copper foil on the surface was removed by etching in the same manner as in Example 1, and the residual voids and the intersection points of the warp and weft of the glass cloth were formed. When the occurrence of the measling was confirmed visually and with a magnifying glass, it was confirmed that the measling had occurred.

The surface roughness of the laminated plate obtained above was measured using Surfcom, manufactured by Tokyo Seimitsu Co., Ltd., and the maximum value was determined to be 3.6 to 4.3 mm. Table 1 shows the results.

Comparative Example 2 In the same manner as in Example 1, a double-sided copper clad laminate having a thickness of 0.2 mm was formed and further subjected to etching treatment to obtain an inner layer circuit board having a signal circuit, a power supply circuit and a ground circuit. Formed. The obtained inner layer circuit board was laminated with a plurality of 0.15 mm prepregs, and further a copper foil having a thickness of 18 μm was laminated on the outer side thereof, and a pressure body was sandwiched between paired metal plates. A plurality of sets of pressure bodies sandwiched by the metal plates to be formed were sandwiched between a pair of hot plates to perform heat and pressure molding.

The molding condition is that the pressure is 50 kg / cm.
This pressure was set to ^2, and this pressure was maintained until the temperature of the product sandwiched between the metal plates reached 150 ° C.

When the temperature of the product reached 150 ° C., the pressure was reduced to 30 kg / cm ² , the temperature was lowered and the product was cooled, and then the pressure was released to obtain a multilayer printed wiring board having four layers.

A test piece of 300 × 500 mm was prepared from the obtained laminated plate, and the copper foil on the surface was removed by etching in the same manner as in Example 1, and the residual voids and the intersection points of the warp and weft of the glass cloth were formed. When the occurrence of the measling was confirmed visually and with a magnifying glass, it was confirmed that the measling had occurred.

The surface roughness of the laminated plate obtained above was measured using Surfcom, manufactured by Tokyo Seimitsu Co., Ltd., and the maximum value was determined to be 3.4 to 4.3 mm. Table 1 shows the results.

[0029]

[Table 1]

As shown in the results of Table 1, it was confirmed that no measling occurred in Example 1 and that the surface roughness was better than in Comparative Examples 1 and 2.

[0031]

According to the method for producing a multilayer printed wiring board of the present invention, the molding pressure is applied at 40 to 60 kg / cm ² until the resin impregnated in the substrate is melted, and then the resin is cured and cooled. Since pressure is applied at 10 to 20 kg / cm ² until that time, it is possible to facilitate pressure control, reduce the occurrence of measling in the obtained multilayer printed wiring board, and further improve the surface roughness. it can.

[Brief description of drawings]

FIG. 1 is a temperature and pressure profile diagram according to an embodiment of the present invention.

[Explanation of symbols]

 1 Pressure profile 2 Temperature profile

Claims (1)

[Claims] 1. A required number of prepregs, in which a base material is impregnated with a resin varnish, are stacked on top and bottom of an inner layer circuit board having a circuit pattern formed on the front and back sides thereof, and metal foils are stacked on both sides of the prepreg, which are then heat-pressed. the method for manufacturing a multilayer printed wiring board that, pressurized with 40~60kg / cm ² until the molding pressure was impregnated into the base material resin is melted, then, 10-20 kg / cm ² until the resin is cooled and cured A method for manufacturing a multilayer printed wiring board, which comprises pressurizing.