Improvement of Resin Adhesion by Roughening Copper Plating

Abstract

Effects of current density and plating time on structures and resin adhesion properties in roughening copper plating for improving a resin adhesion were studied. As the current density of the plating increased, the number density of plated granular copper particles increased, and rough surface was formed. As the plating time became longer, the plated granular copper particles became larger and surface roughness increased. As the arithmetic mean height (Sa) increased, the shear strength increased and reached a maximum at Sa：400 to 500 nm. The reason of decreased shear strength is the surface convex portion is excessively enlarged, so that the gap between the copper particles is closed and the bonding area with the resin is reduced. The roughening copper plating showed high resin adhesion even after moisture sensitivity tests, because the increase in the bonding interface suppressed an infiltration of water. Moreover, even noble metal plating over the roughening copper plating, the resin adhesion was high, and good results were shown even after the moisture sensitivity tests.

Based on these results, it is possible to provide a lead frame with excellent adhesion to resin even in a high temperature and high humidity environment by roughening copper plating.