Enhancing High Temperature Adhesion Performance Via a Renovated Leadframe Surface Treatment

Abstract

Leadframe based micro-electronic packages are widely used in the semiconductor industry. The metal leadframe surface properties directly impact its adhesion with epoxy molding compound (EMC). During the manufacturing process and application services, the electronic packages unavoidably suffer from moisture and heat stress. When the moisture in the package volatilizes during the reflow process, its force may be strong enough to break the adhesion between the leadframe and EMC, causing interfacial delamination. In addition, the leadframe surface inevitably oxidized (especially Cu surface) under high thermal loading during the assembly process, and the thickness of metal oxides layer could rise quickly at such high temperature operation. The thick metal oxides layer may deteriorate the interfacial strength between leadframe and EMC, leading to higher tendency of package delamination after stressed The work here evaluated an innovated leadframe surface treatment method called NEAP, with which the copper surface of leadframe was first covered with a thin layer of silver, and then the silver surface was further chemically treated to form a special oxidization film to act as an adhesion promoter for EMC. The NEAP leadframe was compared with the conventional copper leadframe (selective silver) and rough copper leadframe, in terms of its package level reliability. Under severe thermal loading conditions, most of the leadframes could not survive the reliability tests and showed package delamination. On the contrary, the NEAP leadframe show outstanding adhesion performance compared to the others. The NEAP process concept was discussed in detail. The NEAP leadframe is suggested for use in micro-electronic packages that require high thermal performance.