New aspects in characterization of adhesion of moulding compounds on different surfaces by using a simple button-shear-test method for lifetime prediction of power devices

The knowledge of moulding compound adhesion on different surfaces inside a semiconductor package is fundamental to ensure high reliability of the devices. The most susceptible interfaces are the boundary surfaces between moulding compound/chip and moulding compound/lead frame. The adhesion properties of these interfaces are influenced by various material and process parameters for chip surface and bond pad conditioning. The knowledge of the zero hour adhesion state and the possible degradations during reliability stress tests like e.g. high temperature storage (HTS) or temperature cycling (TC) is the base to perform a trusty lifetime prediction. This paper shows the principle of button-shear-test method offering the determination of adhesion in a quantitative way. The influence of different moulding compound materials, polyimide layers and bond pad conditioning on moulding compound adhesion on silicon is described by corresponding force-displacement diagrams. Degradation effects of moulding compound adhesion on copper lead frames after performing HTS stress tests is presented and will be discussed. For high accelerated HTS tests the possibility of test time reduction by a factor of 10 compared to automotive qualification standards AEC-Q100/101 is discussed in the paper based on performed experiments (Automotive Electronic Council, 2003, 2005 [1,2]).