Concerning thermomechanically induced failures, such as metal line deformation and passivation cracks, there is a practicable way to achieve the zero-defect limit of plasticencapsulated 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 I of this series of papers, the yield stress of the power metallization is shown to play a crucial role for the generation of metal deformation and passivation cracks. Understanding the ratcheting mechanism led to the development of a new layered metallization material with a distinctly increased yield stress, resulting in a considerably reduced failure generation.

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Concerning thermomechanically induced failures such as metal-line deformation and passivation cracks, there is a practicable way to achieve the zero-defect limit of plasticencapsulated power devices. This limit can be reached by, first, evaluating the influence of the major components involved and, consequently, by selecting the appropriate materials and measures, and, second, by always keping in mind the interdependence between all components, 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 III of this series of papers, the influence of passivation and die coating materials on thermomechanical damage is investigated. Finally, it is shown that an intelligent chip design, in combination with a stiff Al multilayer, a low-stress molding compound (low coefficient of thermal expansion and high Young's modulus), a new passivation material, and an appropriate polyimide layer, may reduce the thermomechanical damage to zero, even for electronic power devices.

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The design of electric machines is motivated by electromagnetic and mechanical requirements. The magnetic flux is confined and guided by ferrite cores which consist of coated electrical sheets with a thickness of only a few tenths of a millimeter in order to minimize the eddy current losses. This heterogeneous structure causes preload dependent transversal isotropic material properties which affect the fatigue behavior and structural dynamic behavior of the machine. The material constitutive equations are defined by five parameters which must be derived from experimental investigations with respect to compression in the stacking direction. In this paper, a test procedure is introduced to determine the elastic and torsional stiffness as well as the lateral elongation of the stack depending on its preload.