JPS6218351B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a manufacturing method for suppressing warping of paper-based laminates.

Metal foil-covered laminates for printed circuits are subjected to repeated humidification and heat treatment during the circuit board manufacturing process, which causes warping or twisting of the laminate board, which often causes problems during circuit board manufacturing work or component assembly work. cause In particular, as substrate work sizes increase, circuit densities increase, processing processes become more automated, and heating process cycles increase, requirements for preventing warpage and twisting of substrates are becoming increasingly strict.

Paper-based single-sided metal foil-covered laminates have an asymmetrical structure in which one side is made of metal foil and the other side is made of a synthetic resin-impregnated base material, so the metal foil and the board are not easily connected during molding and circuit board manufacturing processes. Due to the difference in expansion and contraction, complex warping and twisting occur. That is, during humidification and heating, the substrate expands and the metal foil side becomes concavely warped, and conversely, during dehumidification and after heating, the substrate contracts and the metal foil side becomes convexly warped.

Conventional paper-based laminates coated with metal foil on one side have the drawback that they cannot meet the severe warping and twisting prevention requirements described above.The present invention solves the above drawbacks,
The purpose of the present invention is to provide a paper base laminate that exhibits particularly little twisting during circuit board manufacturing processes under severe humidification and heat treatment conditions.

The present invention is characterized in that when a prepreg obtained by impregnating and drying a paper base material with a synthetic resin is laminated and molded, the prepreg at the center in the thickness direction is brought into contact with the wire surfaces during paper base paper making. .

Paper base materials differ in paper density, fiber arrangement, and fine fiber content between the felt side and the wire side during papermaking, and in particular, many fine fibers coexist on the felt side. The present invention focuses on this point. That is, the contact between the felt surfaces of the prepregs causes large dimensional changes and large expansion during molding. In particular, the amount of change at the center in the thickness direction is remarkable. On the other hand, when the wire surfaces contact each other, there is little dimensional change during molding, there is little difference in expansion and contraction between the surface and the center in the thickness direction, and internal strain is small, so there is less twisting after molding and heat treatment. A laminate can be obtained.

Examples of the present invention will be described below.

Example 750g of synthetic cresol and 750g of tung oil were heated to 80-85°C in the presence of 0.9g of para-toluenesulfonic acid and reacted for 3 hours. Then 25% ammonia water 24
g, 300 g of 85% paraformaldehyde and 100 g of methanol were added, and the mixture was reacted at 80 to 85° C. for 4 hours. Next, the mixture was concentrated under reduced pressure and diluted with a toluene-methanol mixed solvent (mixing ratio 1:1) to obtain a tung oil-modified phenolic resin varnish with a resin content of 50%.

Next, the resulting varnish was impregnated into 1/mils high-density kraft paper and dried at 120°C, resulting in a resin content of 46%.
% prepreg was obtained. In this combination of 8 plies of prepreg, the two prepregs at the center in the thickness direction have their wire surfaces in contact with each other, and the second and third plies of prepreg from both surfaces have their felt surfaces in contact with each other, and each 1,
For the second ply of prepreg, the felt side and the wire side are in contact, and one surface is stacked with a sheet of 35μ thick copper foil coated with adhesive, and the temperature is
Heat and pressurize at 170℃ and pressure 100Kg/ ^cm2 for 60 minutes.
A single-sided copper-clad laminate with a thickness of 1.6 mm was obtained. The combined configuration of prepreg and copper foil is shown in Figure 1. 1 is prepreg, 2 is wire side, 3 is felt side, 4
is copper foil.

Comparative Example 1 As a combination configuration of the 8 plies of prepreg obtained in Example, the felt surfaces of the two prepregs in the center in the thickness direction were in contact with each other, and the felt surfaces and wire surfaces of the other prepregs were in contact with each other. A single-sided copper-clad laminate with a thickness of 1.6 mm was obtained in the same manner as in the example. The combined configuration of prepreg and copper foil is shown in Figure 2.

Comparative Example 2 A single-sided copper-clad laminate with a thickness of 1.6 mm was obtained in the same manner as in the example by combining the 8 plies of prepreg obtained in the example so that the felt surface and the wire surface were in contact with each other. FIG. 3 shows the combined configuration of prepreg and copper foil.

The dimensional changes of each laminate obtained in the above Examples and Comparative Examples are shown in FIG. 4, and the torsion is shown in FIG.

The dimensional changes in Figure 4 are determined by marking 250 x 250 mm on the 2nd and 4th ply of prepreg from the surface, in the prepreg state, after lamination molding,
It shows the amount of change in the lateral direction after E-3/160 processing. A shows the amount of change in Example, B shows the change in Comparative Example 1, and C shows the change in Comparative Example 2. Curve a shows the change in the second ply from the surface, and curve b shows the change in the fourth ply. Further, the twist in FIG. 5 shows the amount of twist of each laminate after E-3/160 treatment. It can be seen that the material according to the present invention has less dimensional change and less twist.

As described above, the present invention is a paper-based laminate in which the prepreg in the center of the thickness direction is arranged with the wire surfaces in contact with each other, thereby reducing dimensional changes inside the laminate during molding and reducing internal strain. It can reduce distortion caused by humidification and heat treatment in the subsequent circuit board manufacturing process, and has extremely high industrial value as it can be used to cope with larger circuit board work sizes and higher circuit densities. .

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the layer structure of prepreg in an example of the present invention, FIGS. 2 and 3 are cross-sectional views showing the layer structure of prepreg in a comparative example, and FIG.
The figures are curve diagrams showing dimensional changes of the laminates in Examples and Comparative Examples, and FIG. 5 is a bar graph showing twist. 1 is prepreg, 2 is wire side, 3 is felt side, 4 is copper foil.

Claims (1)

[Claims] 1. A laminate board characterized in that when a prepreg obtained by impregnating and drying a synthetic resin into a paper base material is laminated and molded, the wire surfaces of the prepreg in the center in the thickness direction are kept in contact with each other during paper base paper manufacturing. manufacturing method.