JPH0412899B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for producing an epoxy resin laminate with excellent surface smoothness. Conventional technology As is well known, laminates are made by combining thermosetting resin with paper,
It is manufactured by impregnating and drying a sheet-like base material such as glass cloth, glass nonwoven fabric, or cotton cloth, stacking the required number of B-staged prepregs, and heating and pressurizing them to harden the resin. Problems to be Solved by the Invention Woven fabric is generally used as the surface substrate of epoxy resin laminates, but since woven fabric is woven with alternating warp and weft threads, the overlapping parts of warp threads and weft threads are thick. , the part between them becomes thinner, and the problem of partially different thickness cannot be avoided. Therefore, in the case of a laminate, local differences in the thickness of the woven fabric are directly traced, impairing the smoothness of the surface of the laminate. When using a laminate as a substrate for a printed circuit board, as the density of circuits has increased in recent years, it has become impossible to ignore the irregularities on the surface of the laminate due to the texture of the woven fabric as described above. , laminates with smoother surfaces are increasingly desired. An object of the present invention is to provide a laminate using glass cloth as a surface base material and having excellent surface smoothness. Means for Solving the Problems The present invention has been made to achieve the above object, and consists of a laminate in which a prepreg prepared by impregnating glass cloth with an epoxy resin composition and drying it to form a B stage is used on the surface of the prepreg layer. is characterized in that the thickness of the prepreg used on the surface thereof is 120 to 150% of the thickness of the glass cloth, and the weight average molecular weight of the B-staged resin is 1000 to 8000. Effects The present invention has the above-mentioned characteristics, so that the resin can fill in the unevenness caused by the texture of the glass cloth, thereby making it possible to obtain a laminate having extremely excellent surface smoothness. If the finished thickness of the prepreg is less than 120% of the thickness of the glass cloth, the amount of resin is too small.
If the unevenness of the glass cloth cannot be sufficiently filled, and if the amount exceeds 150%, the appearance of the prepreg will deteriorate, and the surface smoothness will deteriorate when both are made into a laminate. In addition, the weight average molecular weight of the prepreg resin is
If it is less than 1000, the resin in the glass cloth will flow too much during lamination molding, resulting in the glass cloth becoming uneven. On the other hand, the weight average molecular weight
If it is more than 8000, the resin will not flow during molding, making it impossible to obtain a good laminate. Example An example of the present invention will be described. Examples 1 to 5 100 parts by weight of epoxy resin (trade name Epon-828, manufactured by Yuka Ciel), 4 parts by weight of dicyandiamide, 2
A varnish containing 0.3 parts by weight of -ethyl-4-methylimidazole and having a solid content of 55% was prepared. This varnish was impregnated into a glass nonwoven fabric (weight 75 g/m ² ) and dried to produce a prepreg with a resin content of 77% by weight.
was created. In addition, the same varnish was impregnated into glass cloth and dried so that the finished thickness was 120 to 150% of the thickness of the glass cloth and the weight average molecular weight of the resin was 1000 to 8000. Five types of B-staged prepregs were produced. In addition, adjustment of the finished thickness of prepreg [] is as follows:
This was done by changing the size of the gap between the squeeze rolls through which the varnish-impregnated glass cloth was passed. Further, the weight average molecular weight was adjusted by changing the drying temperature and time. Details are shown in Table 2. After stacking 6 sheets of prepreg [ ] and placing one sheet of prepreg [ ] on both surfaces, 18 μ thick copper foil was placed on both surfaces, and the pressure was 35 Kg/cm ² and the temperature was 170°C for 90 minutes. A laminate was obtained by applying pressure and heating. Comparative Examples 1 to 7 Prepreg [] was produced in the same manner as in the example.
In addition, similar varnishes were impregnated into similar glass cloth and dried, and seven types were prepared with finished thicknesses ranging from 110% to 160% of the thickness of the glass cloth, and weight average molecular weights of the resins ranging from 900 to 10,000. A prepreg [] was prepared. A laminate was obtained using prepreg [] and prepreg [] in the same manner as in the example. Table 1 shows the results of measuring the surface roughness of the obtained laminate.

【table】

【table】

[Table] Effects of the Invention As described above, the present invention provides prepreg to be placed on the surface so that the finished thickness is 120 to 150% of the thickness of the glass cloth, and the weight average of the impregnated resin is By using a B-staged prepreg with a molecular weight of 1,000 to 8,000, a laminate with excellent surface smoothness could be obtained. This industrial value is extremely large.

Claims (1)

[Scope of Claims] 1. In the production of a laminate in which prepreg obtained by impregnating and drying a sheet-like base material with an epoxy resin composition is laminated and molded, the prepreg used for the surface is prepared by using glass cloth as the sheet-like base material. A method for producing a laminate, characterized in that the thickness of the prepreg is 120 to 150% of the thickness of the glass cloth, and the weight average molecular weight of the resin is 1000 to 8000.