Mold Compound Adhesion to Bare Copper Lead Frames – Effect of Laser Texturing

This paper investigates the effect substrate preparation has on epoxy mold compound (EMC) adhesion to bare copper leads. There have been four basic strategies employed to characterize and subsequently improve adhesion between the EMC and copper: 1. Choosing a particular copper alloy, i.e. varying alloy effects in copper to improve oxidation control and thus adhesion. 2. Modifying the mold compound chemistry. 3. Modifying the surface chemistry/ topography of the copper by metal plating, organic inhibitor priming, vacuum deposition, ion implantation, UV cleaning, chemical oxidation, and various forms of mechanical roughening including sand or bead blasting. 4. Controlling the rate of oxidation and CuO/Cu2O ratio during product assembly. The effects of mold compound chemistry, copper alloying, control of oxidation level and surface topography modification through various means such as laser texturing and Electrical Discharge Machining (EDM) are investigated. It will be shown that laser surface texturing offers one possible low cost solution to achieving significant improvement in adhesion by changing the surface topography of the copper substrate.