On mold corner effects of EMC adhesion for IC encapsulation process

In the IC packaging process, epoxy molding compound (EMC) was filling the mold cavity and cured in the mold. At the same time, adhesion may occur in the interface between the surface of mold and cured EMC. Large adhesion force could cause many problems, which may influence the ejection process. Some other critical problems may also happen in the IC molding process if adhesion problem occurs, such as distortion or crack on ejecting finished parts, residue of cured EMC on the surface of mold affecting the quality of the products, and regular, tedious and not effective mold cleaning. So how to improve the mold adhesion force effectively is an important issue for industry and research institutes. To avoid the mold adhesion problems, improving the mold design and applying suitable surface treatments such as mold surface coating are the common approaches. Among these, applying suitable surface coating is a more popular and practical approach. This study described the approach of using a semi-automatic EMC adhesion force test instrument to measure adhesion force between the mold surface and EMC and studied the corner effect during the encapsulation process. Three different cavity arcs were designed in three specimens and molded and tested during molding to observe the corner effects. Engineers could determine the best type of surface treatment and the type of corner to reduce the amount of mold adhesion force. This paper also discussed the issue of successive adhesion force test and the variation of adhesion force during successive molding test to predict the time for mold cleaning. It was found that larger corner would cause smaller adhesion force. Repeat experiments were executed and found that the test results could be repeated.