| 摘要 |
PURPOSE:To enable a flexible wiring board to have an excellent low thermal linear expansion property so as to improve the film characteristic of the board by mixing polyamic acid varnish having a low thermal linear expansion property with another polyamic acid varnish having a high thermal linear expansion property and directly applying the mixed varnish to metallic foil. CONSTITUTION:Polyamic acid varnish having low thermal linear expansion property is prepared by making an acid dianhydride component composed mainly of pyromellitic acid dianhydride and diamine component composed mainly of p-phenylenediamine to react to each other. Then aimed varnish is prepared by mixing this varnish with polyamic acid varnish which becomes polyimide having a high coefficient of thermal linear expansion. After the mixed varnish is directly applied to metallic foil, the varnish is dried by removing the solvent contained in the varnish and imidizing the varnish. Therefore, a flexible wiring board composed of polyimide which is improved in thermal linear expansion and curl and metallic foil can be surely obtained.
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