Studies on microstructure of epoxy molding compound (EMC)-Leadframe interface after environmental aging

The Leadframe-Epoxy molding compound (EMC) interface is known to be one of the weakest interfaces in an electronic packaging exhibiting delamination during reliability test. Interfaces of EMC and leadframes with different metal coatings exhibit different failure mode behavior after environmental aging because of the different adhesion strengths. In this paper, the interface microstructure of EMC-leadframes with different metal coatings was studied using Scanning Electron Microscopy (SEM). The leadframes used in this study were copper, copper with Ag coating, Ni coating and Ni/Pd/Au coating. The results of tab pull testing showed the adhesion strength of the EMC/copper leadframe interface was strongest while that of the EMC/leadframe with Ni/Pd/Au coating interface was weakest. Little delamination appeared on the EMC/Cu sample, including the samples after the moisture and reflow treatment. Delamination appeared on the interface of EMC/leadframe with Ag coating after treatment, and serious delamination was found on the interface of EMC/leadframe with Ni coating. The SEM micrographs showed that there were some microcracks between the filler of EMC and the leadframe.