JPH046897A - Manufacture of multilayer plate - Google Patents

Abstract

PURPOSE:To suppress the remaining of voids so as to get a multilayer plate, wherein dimension change and warps are small and a glass unwoven base material prepreg is used, by lowering the molding pressure when the viscosity of the resin within the prepreg is high, and flowing resin compulsively at high pressure when the resin viscosity is high so as to mold it. CONSTITUTION:A circuit is processed in a laminated board, whose both sides are lined with copper and which is obtained by piling up four piles of prepregs A, where glass unwoven fabric is used, and arranging a copper foil each on both sides, and heating and molding it under pressure, and then one ply each of prepreg A and further one ply each of prepreg B, on both sides of this inner layer circuit board, and a copper foil, at the outermost surface, are placed, and the initial molding pressure is set to 20-40kg/cm<2>, and then it is raised to 60-80kg/cm<2> after the resin within the prepreg fuses and reaches the lowest solvent viscosity and before sudden viscosity rise occurs, and after molding it is cooled at a pressure of 5-10kg/cm<2> so as to get a multilayer board.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for manufacturing a multilayer board on which semiconductor elements are mounted and used as an insulating substrate in electronic equipment.

BACKGROUND OF THE INVENTION In recent years, as demands for higher performance and smaller size of electronic devices have become stronger, multilayer boards on which semiconductor elements are mounted are required to have improved dimensional accuracy and to suppress warping and voids.

Multilayer boards are formed by impregnating a sheet-like base material with thermosetting resin.
The prepreg obtained by drying is combined with one or more inner layer circuit boards prepared in advance and stacked on top of each other, and then heated and pressurized to integrate them. The pressure control of this heating and pressure molding is as follows: (1) The initial low molding pressure is maintained until the final cooling step.

(2) The initial molding pressure is set to a low pressure, and the pressure is increased at a timing based on temperature, time, resin melt viscosity, etc., and the high pressure is maintained until the final cooling step.

This is the usual method.

Problems to be Solved by the Invention However, in forming a multilayer board, a prepreg using a glass nonwoven fabric as a sheet-like base material is combined with a pre-prepared inner layer circuit board as part or all of the prepreg, and then heated and pressure molded. When performing pressure control as described in (1) above, microvoids are likely to remain in the formed laminate. This tendency is more pronounced as the resin contains an inorganic filler. On the other hand, if the pressure control as described in (2) above is performed, distortion during molding remains inside the laminated plate, and warpage subsequently occurs.

The object of the present invention is to suppress the occurrence of warpage and the remaining voids in a multilayer board that is formed by heating and press-forming a part or all of a prepreg made of glass nonwoven fabric in combination with a pre-prepared inner layer circuit board. be.

Means for Solving the Problems In order to solve the above problems, the molding pressure was controlled as follows.

The initial molding pressure is 20 to 40 kg/cil.

After that, the resin in the prepreg melts, reaches the minimum melt viscosity, and before a sudden increase in viscosity occurs, the
/cm.

A pressure of 5 to 20 kg/c+fl is applied in the cooling process after molding.

Effect: In the method according to the present invention, the molding pressure is lowered when the resin viscosity in the prepreg is high to avoid the trapping of air bubbles that would occur if the resin was forced to flow under high pressure when the resin viscosity was high. .

However, if the initial pressure is lower than 20 kg/c-d, heat is not well conducted from the prepreg heating plate to the prepreg, and it takes time to raise the temperature and makes it difficult to raise the temperature uniformly.

By increasing the pressure when the melt viscosity of the resin is at its lowest, uniform resin flow is achieved, which leads to suppression of dimensional shrinkage. Air bubbles remaining inside are expelled outside with the smooth flow of resin. If the pressure at this time is low, voids will remain, and if it is too high, the glass nonwoven fabric will not be able to resist the flow of the resin and will be partially cut.

In the cooling process, the pressure is lowered to release the distortion that occurred during high-pressure molding. If the pressure at this time is high, the strain will not be released, which will cause warpage to occur later.

Note that since cooling is performed via a press hot plate through which a coolant is passed, if the pressure in the cooling process is too low, the cooling time will be too long.

Next, the present invention will be explained in detail.

Example 1 A glass nonwoven fabric (41 g/rd) was impregnated with a bisphenol type epoxy resin containing an inorganic filler and dried to obtain a prepreg (A).

Separately, a glass woven fabric (215 g/rl ()) was impregnated with a bisphenol-type epoxy resin that does not contain fillers, and dried.
A prepreg (B) was obtained.

Layer 4 plies of prepreg (A), with 35μm on both sides.
One sheet of thick copper foil was placed on each sheet, sandwiched between mirror plates made of stainless steel, and molded under heat and pressure in a reduced pressure atmosphere.

The double-sided copper-clad laminate obtained above was subjected to a blackening treatment on the circuit surface using a conventional method to obtain an inner layer circuit board.

One ply of prepreg (A) is placed on each side of this inner layer circuit board, one ply of prepreg (B) is placed on each side, and one ply is placed on the top surface.
An 8 μm thick copper foil was placed, sandwiched between stainless steel mirror plates, and heated and pressed in a reduced pressure atmosphere.

The molding conditions were as follows.

(1) The initial molding pressure was set to 20 kg/cd, and the press hot platen temperature was set to 110°C.

(2) 45 minutes after starting heating and pressing under the conditions of (1) above, the molding pressure was increased to 80 kg/cij, and the press platen temperature was set to 175°C. (This setting was determined in advance by determining the time when the melt viscosity of the resin becomes the lowest.)

(3) After 75 minutes from setting the conditions in (2) above, reduce the pressure to 10 kg/cd and cool for 40 minutes to 1.6+ m
A multilayer board with a thickness of ++ was obtained.

Comparative Example 1 In Example 1, heating and pressure molding was performed at a molding pressure of 40 kg/cTi and a press temperature of 175°C, and the pressure during cooling was reduced to 1.
At 0 kg/d, a multilayer board with a thickness of 1.6 mm was obtained.

Comparative Example 2 In Example 1, heating and pressure molding was performed at a molding pressure of 80 kg/C'IiT and a press temperature of 175°C, and this pressure was maintained even during cooling to obtain a multilayer board with a thickness of Ta.

Comparative Example 3 In Example 1, conditions (1) and (2) are the same,
Even during cooling, the pressure (80 kg/cn) under condition (2) was maintained to obtain a multilayer board with a thickness of 1.6 mm.

Table 1 shows the characteristics of each multilayer board obtained above.

The size of the test piece is 300 x 300 cm.

*l Amount of dimensional change before and after enching the entire surface of the test piece and heat-treating it at 150°C for 30 minutes *2 Maximum value of the raised lids at the four corners measured by placing the test piece after heat treatment on a surface plate *3 0 Number of voids of 1+a or more/Length of cut surface 500 mm (part of layer formed of multilayer molded prepreg) Effects of the Invention As is clear from Table 1, according to the method according to the present invention, voids can be reduced. It is possible to manufacture a multilayer board using a glass nonwoven fabric base material prepreg, which suppresses the residual amount of glass, has small dimensional changes, and has small warpage.

Claims (1)

[Claims] 1. A method in which a prepreg obtained by impregnating and drying a sheet-like base material with an epoxy resin and one or more inner layer circuit boards prepared in advance are combined and stacked and integrated by heating and pressure molding, at least one sheet of the prepreg. uses glass nonwoven fabric as a sheet-like base material, the initial pressure of molding is 20 to 40 kg/cm^2, and the molding is performed after the resin in the prepreg reaches the minimum melt viscosity but before a rapid increase in viscosity occurs. A method for producing a multilayer board, characterized by increasing the pressure to 60 to 80 kg/cm^2, and then increasing the pressure to 5 to 20 kg/cm^2 during cooling. 2. 2. The method for manufacturing a multilayer board according to claim 1, wherein a glass nonwoven fabric is used as the prepreg sheet base material in contact with the surface of the inner layer circuit board.