Effect of Leadframe Oxidation on the Reliability of a Quad Flat No-Lead Package

This study analyzed the reliability of two condition types of copper leadframe, namely, good and oxidized. Both types of leadframe were used in the fabricating process of a quad flat no-lead (QFN) package. Determining the adhesiveness of die strength and determining the strength of the leadframe are important in order for the package to obtain higher reliability. Commonly, an epoxy material is used in the die attachment process for die adherence onto the leadframe. A statistical analysis of the die shear test and the cyclic strain test of a QFN package was performed in this paper. From the application of the $t$-test method, the $p$-value shows a significant difference in die shear stress depending on leadframe condition. Based on a process capability ratio $(Cpk)$ above 1, the leadframe in good condition showed better processing capability than the oxidized leadframe. The Coffin–Manson approach was used in the cyclic loading of a QFN package to predict the package reliability in terms of cyclic strain. The leadframe in good condition showed a higher die strength value and lower microstrain compared with the oxidized leadframe. The oxidized leadframe provided a poor surface to attach adhesive and a higher microstrain on cyclic load, resulting in a negative effect on package reliability, such as a crack phenomenon at the epoxy interface between the die and the leadframe. This occurrence may ultimately cause delamination, which occurs between the die and the leadframe die pad.