| 摘要 |
PURPOSE:To form a thin film multilayered circuit board having small contact resistance and high reliability by forming a through hole pattern having desirable coverage on a polyimide resin film. CONSTITUTION:A primary wiring electrode metal film 20 of an Al film, etc., is formed on a thin film multilayered circuit board 10. The board 10 is spin- coated thinly with varnish of polyimide resin, and thermally cured to form a thin first layer polyimide film 30. Then, it is spin-coated with varnish of polyimide resin having faster etching rate than that of the film 30, and thermally cured several times, thereby forming a thick second layer polyimide resin film 31. Thereafter, an etching selection mask 40 is formed on the film 31. The film 31 of the opening of the mask 40 is wet etched to form a forward-tapered through hole. The film 30 of a lower layer is etched by a dry etching method, and the mask 40 is further removed. |
