The influence of heat treatment on the adhesion between molding compound and lead frame

Surface chemistry and surface energy of copper leadframe after thermal treatment at 175C were studied by XPS and contact angle. The adhesion after JEDEC level 3 and reflow between epoxy molding compound and leadframe after thermal treatment was measured too. The results shows that the adhesion between epoxy molding compound and heated lead frame increased with heat the leadframe up to 3 minutes then start to decreased. The adhesion force becomes consistent after 7 minutes heating. Form XPS analysis it was suggested that the major chemical of leadframe surface is cupric hydroxide and cuprous oxide after heating the leadframe for short period. With increasing of heating time, cupric oxide was observed on leadframe surface. Copper canpsilat be found no matter how long the leadframe was heated. Compare with adhesion test result, it can be concluded that cupric hydroxide and cuprous oxide has great contribution on the adhesion improvement. The existence of cupric oxide will decrease the adhesion significantly. Surface energy measurement shows that higher adhesion is related to higher surface energy.