Method for producing flexible printed wiring board, and flexible printed wiring board

Abstract

The present invention provides a method for producing a flexible printed wiring board which allows formation of a bump on a wire trace even in a high-density mounting process, and a flexible printed wiring board which realizes high-density mounting with high reliability. In the method for producing a flexible printed wiring board including an insulating layer and a wiring pattern on which a semiconductor chip is to be mounted, the pattern being formed of a conductor layer provided on at least one surface of the insulating layer, the method includes a first etching step including applying a photoresist onto a conductor layer and light-exposing the photoresist by the mediation of a first mask, followed by development, to thereby form a first resist pattern, and etching the conductor layer so as to penetrate the layer in the depth direction, to thereby form a first wiring pattern; and a second etching step including light-exposing the first resist pattern by the mediation of a second mask, followed by development, to thereby form a second resist pattern formed of a remaining portion of the first resist pattern, subsequently, leaving, as a thick portion, a portion of the first wiring pattern covered by the second resist pattern, and half-etching a portion other than the thick portion to an intermediate thickness of the conductor layer, to thereby form a second wiring pattern in the form of a thin portion having a thickness relatively smaller than that of the thick portion.

Dependencies are inferred from the claim text.