Increasing IC Leadframe Package Reliability

As the conversion of the electronics industry to lead free soldering materials continues some unexpected negative side effects of higher lead free reflow temperatures have occurred. Component level defects such as delamination and "popcorning" in surface mount IC lead frame components have increased significantly since lead free soldering has become mainstream. Popcorning and delamination defects often manifest themselves as a fracture between the epoxy based encapsulant and the metal, usually copper alloy, leadframe components used to form a surface mount IC component. This fracture occurs when moisture in the package volatilizes during the reflow process and forces its way through the encapsulation material and leadframe interfaces. The keys to popcorning, or delamination, defect reduction are twofold. The first objective is to enhance the bond between the encapsulant and the copper leadframe materials to form a stronger bond that is capable of withstanding the vapor pressures induced during reflow. The second objective is to provide a superior bond between the leadframe and encapsulant thus minimizing moisture ingress. In either case, delamination defects may be identified immediately after assembly during ICT, have latent defects that manifest themselves in the field, or a mixture of both. New chemical treatment processes have been developed that pre-treat the copper surfaces of the leadframe and significantly enhance the bond between the encapsulant material and the metal leadframe. The chemical treatment process results in micro-roughening of the copper surfaces and at the same time depositing a thermally robust film that enhances the chemical bond between the epoxy encapsulant material and the copper alloy leadframe.