Understanding delamination for fast development of reliable packages for automotive applications. A consideration of adhesion by interlocking and anchoring

Abstract

Thermo-mechanical stress caused by the mismatch of coefficients of thermal expansion (CTE) and temperature variations remain a major concern for the reliability of semiconductor components. This issue is usually addressed by exposing the component to temperature cycling stress tests for a certain number of cycles, followed by e.g. scanning acoustic microscopy (SAM) to investigate delamination. Discussions about specific cycling conditions, e.g. using -65 °C/+175 °C instead of -55 °C/+150 °C for the minimum and maximum temperatures of the cycles or even using liquid-liquid instead of air to air cycling to speed up investigations [1], are often moot, because no real understanding of the effect of the cycling conditions on the component is available. Furthermore, it is almost a truism that testing alone does not suffice to ensure the reliability of a component. Reliability has to be built into the components from the beginning. As a consequence, the question should be turned around: it is not enough to look at delamination after a certain number of cycles in a stress test. The question is rather how the component should be designed and how the materials should be chosen to prevent delamination. Thus, the focus is changed from measuring delamination to measuring adhesion. In the previous paper [6] an approach for a better understanding of adhesion in terms of possible material combinations, temperature influence (ageing, delamination due to critical induced stress) and topology of interfaces was presented. This paper focuses on methods to reduce interfacial stresses in order to reduce the risk of delamination.