Impact of mold compound on reliability performance in roughened Ni/Pd/Au-Ag preplated leadframe package

Abstract

In this study, roughened Ni/Pd/Au-Ag alloy-plated Cu leadframe and two types of mold compounds (A and B) were studied in terms of button shear tests on the leadframe surfaces and package performance after assembly and after reliability stresses. The package reliability stresses include pre-conditioning at Moisture Sensitivity Level 3 (MSL3) with three cycles of reflow at 260 °C (peak temperature) according to the standard for automotive products, followed by 100 cycles of temperature cycling (TC), autoclaving (AC) for 96 hours, and TC for 500 cycles. The results show that the button shear force of Mold Compound A on the leadframe surface is much higher than that of Mold Compound B on the same leadframe surface at room temperature as well as after MSL3 pre-conditioning. The package using Mold Compound A shows positive results after all the stresses stated above, while the package using Mold Compound B shows no delamination after assembly but does show minor delamination after AC for 96 hours and gross delamination after TC for 500 cycles at the bottom side of a die paddle. It is understood that the roughened surface is only on the top side of the leadframe surface and the bottom die paddle surface is the normal surface. Thus, the interface between the bottom die paddle of the leadframe and mold compound is the weakest interface in terms of adhesion, and after stresses it is weakened further and shows delamination. This study shows that the mold compound plays a very critical role in the package reliability in roughened Ni/Pd/Au-Ag pre-plated leadframe packages.