Low profile tsop approach for MSL 1 delamination free

A low profile TSOP package has the history of die paddle and lead post delamination after pre-con MSL 1 reflow 260°C. One automotive customer had been requesting for this delamination improvement on the die paddle and lead post.. This delamination is worsen by silver plating on the lead post which is meant for wire bondability purpose. The molding compound adhesion towards the silver plated area is weaker compared to the adhesion towards the copper plated area for the current production molding compound. With the pre conditioning of 85°C/85%Rh (MSL1) and 3 times IR reflow of 260°C, the stress build up in the package due to the CTE mismatch (Mold compound CTE1 - 10ppm, CTE2 - 30ppm, Cu A194 - 16ppm) and effect of the moisture absorption will cause the stress build up between the molding compound and lead frame interface. The adhesion between the interface is critical to prevent delamination to occur. Approach of changing to higher adhesion molding compound can reduce the delamination but not sufficient to eliminate the delamination on the silver post. Top Side up-grade roughening preplated lead frame was introduced to increase the adhesion between the interface of molding compound and the lead frame. This enable the package to achieve delamination free. With the introduction of the Up-grade Roughening PPF lead frame, lead flash on the lead is sticking too hard towards the lead and additional anchoring of the lead flash at the lead frame window make it difficult to be removed by High Pressure Water Jet (HPWJ). An approach of redesign of the lead frame window design able to solve the lead flash from sticking firmly to the lead and can be removed by HPWJ easily. Before selecting upgrade roughening preplated lead frame, mechanical roughening and various green compound selection wer also studied for preconditioning MSL1 260C study.