| 摘要 |
PROBLEM TO BE SOLVED: To improve the mass-productivity and quality of a bendable flexible printed wiring board by forming a laminated structure by combining a base insulating layer with cover insulating layers having a coefficient of thermal shrinkage which is different from that of the base insulating layer and heat- treating the part which is to be constituted so that it can be bent permanently and its vicinity at a fixed temperature higher than that used at the time of laminating the cover insulating layers upon the base insulating layer. SOLUTION: A base insulating layer 2 is composed of a polyimide film having a thickness of about 20-100μm and first and second cover insulating layers 5 and 6 are composed of acrylic photosensitive resin layers having thicknesses of about 20-40μm. The coefficients of thermal shrinkage of the layers 2, 5, and 6 are set so that the coefficient of the layer 2 can become smaller than those of the layers 5 and 6. The whole body of this double-faced FRC is bent by heat-treating the whole body at a fixed temperature higher than that used at the time of laminating the layers 5 and 6 upon the layer 2. The heat treatment is performed for about 5-10 seconds at 2O0-250 deg.C. When this heat treatment is performed, only the bending part C provided with an opening 7 is bent and a unified prescribed angle is obtained.
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