| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a surface protective layer that has excellent adhesion to a substrate, in particular to tin, excellent long-term reliability of electric insulation and small warpage. <P>SOLUTION: A method of forming a flexible circuit board protective layer includes a step of forming the protective layer by applying a thermosetting composition and heating it on a flexible circuit board having a wiring pattern in which a tin plating layer is formed on the surface, wherein the thermosetting composition contains a specific carboxyl group-containing urethane resin (A), a curing agent (B) and an acid anhydride (C) as essential components. <P>COPYRIGHT: (C)2013,JPO&INPIT |
