Electroless plating copper cones on leadframe to improve the adhesion with epoxy molding compound

Abstract

A simple method to increase the adhesion strength between leadframe and epoxy molding compound (EMC) was reported in this paper. Cone-structured copper film was deposited on copper-based leadframe sheets by electroless plating. SEM observation of the as-prepared film indicates that cone size distinctly depends on plating time. Adhesion strength between EMC and cone-coated leadframe was measured by button shear test (BST). Results show that when deposition time t::;120s, the adhesion strength increases rapidly with the growth of copper cones, when t > 120s, although cones keep growing, the adhesion strength tends to level off. Average adhesion strength reaches maximum value of 33.80(±1.74) MPa, increased by 87% (57%�124%) when substrate was plated for 600s, compared with that of conventional leadframe. By observing leadframe side of fracture surface after destructive button shear test, two failure modes were proposed: failure at interface and inside EMC. It is assumed that the copper nano-cones structure could effectively increase the contact area of EMC and leadframe, which leads to mechanical interlocking. Such micro-nano structure and its unique property are expected to be applied in the practical industry.

Synthesis of adhesion promoter for lead frame bonding and application of epoxy composite materials

“…Accordingly, the adhesive technology used for material bonding or interfaces is important. [5][6][7] The lead frame is a major component that supports the semiconductor chip while electrically connecting it to the external PCB board within the package. 8 The metal for the lead frame is generally a copper alloy with excellent thermal and electrical conduction capabilities.…”

Enhancing the oxidation resistance of copper by using sandblasted copper surfaces

“…Unlike aluminum oxide, the Cu oxide layer is not self-protective and the oxidation of Cu continues [8,9]. This usually results in delamination that decreases the adhesion between the lead frame and epoxy-molding compound (EMC) [10][11][12][13]. Cu oxidation is considered as a major reliability problem for the development of high-density integrated circuit packages and lead-free soldering.…”