On the Way to Zero Defect of Plastic-Encapsulated Electronic Power Devices—Part II: Molding Compound

Concerning thermomechanically induced failures, such as metal line deformation and passivation cracks, there is a practicable way to achieve the zero-defect limit of plastic-encapsulated power devices. This limit can be reached by evaluating the influence of the major components involved and, consequently, by selecting the appropriate materials and measures. On the other hand, the interdependence between all components must always be kept in mind, i.e., chip and package have to be regarded as an entity. An important finding was that applying simply one improvement step will not necessarily lead to the desired goal. Only the implementation of all improvement steps considering their interdependence is the key for the perfect overall system chip and package. In Part II of this series of papers, the thermomechanical influence of the molding compound (MC) on the chip, i.e., the root cause of metal deformation and passivation cracks, was studied in great detail. Concerning the generation of these failures, the coefficient of thermal expansion was shown to play a key role. However, for a full understanding of the thermomechanically induced damage, the viscoelastic properties of the MC have to be considered.