We have developed a n ultra-compact Power chip size package （Power-CSP） technology suitable for 1200 V/100 A SiC MOSFETs. Power-CSP features an extended gate electrode structure for ease of attaching gate and source surface of power semiconductor chip. In addition, the high insulation structure constitutes a chip-level thin package, which enables low thermal resistance and low inductance. In this paper, the structure of Power-CSP, electrical characteristics and thermal resistance evaluation results are described in detail. In the future, Power-CSP will make it possible to easily design and develop ultra-compact double sided cooled power modules. Furthermore, the implementation of Power-CSP and the integration of power units will enable a dramatic increase in power density and efficiency of power convertor.

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 This paper investigates thermal behavior of microprocessor with chiplets. Targeting desktop PC’s and server microprocessors with 2D based chiplet implementation, effects on junction temperature by thermal conductivity variation of materials used in microprocerssor package and its heat transfer paths are discussed, especially, focusing on TIM (Thermal Interface Material). Thermal resistance variation by TIM thermal conductivity is explored and is discussed with thermal network with component thermal resistance, thermal spreading resistance and thermal local resistance.

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 It is important for semiconductor components to increase the adhesion strength between the mold resin and lead frames. Particularly under high-stress environments such as automotive components, high reliability of adhesion becomes more important compared to conventional methods. We have researched the method of roughened copper plating by using the Periodic Reverse Pulse （PR pulse） current plating. As a result, we have developed a high surface area ratio （S-ratio） film by using the nitrogen additives without sulfur additives. This film shows high adhesion, resulting in a shear strength of 27 MPa or more. This technology is expected to show higher reliability in the field of power devices, such as high current and high temperature conditions.

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In semiconductor pack aging used in automotive and infrastructure products, delamination occurring at the interface between metal components and molding resin is a significant reliability-related problem. This study verified the applicability of a prediction method that uses the ratio of fracture toughness value to fracture parameters as a delamination index. First, we fabricated joint specimens of Cu and molding resin, and evaluated the fracture toughness value for the roughness of Cu surface, the resin type, and the test temperature. Furthermore, using three-dimensional CAD models of two types of product shapes, we calculated the fracture parameters at the corner of Cu and molding resin by finite element method analysis. Finally, we compared the delamination state observed by SAT （Scanning Acoustic Tomography） with the delamination index, clarifying the applicability of the prediction method.

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 Bonding materials for power device s are required to be high thermal and electrical conductivity without environmentally hazardous substances. Electrically conductive adhesive （ECA） is a candidate of alternatives for high temperature Pb-included solder. In the curing process of the suggested ECA, low-melting-point alloys such as Sn-3Ag-0.5Cu solder fillers are molten and bridge between the copper main fillers to reduce the interfacial resistance. The wettability of the alloy on copper is important factor for bridging. In this paper, Sn-58Bi alloy and Sn-3Ag-0.5Cu alloy are used in low-melting point alloy bridged conductive adhesives, and the effects of Sn coating on the main Cu filler on thermal and electrical conductivity are evaluated focusing on wettability in the resin.

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 The superplastic deformation behavior of Sn-Bi-Cu, Sn-Bi-Ni, Sn-Bi-Zn, and Sn-Bi-Sb alloys has been investigated. The purpose of this study is to measure the strain rate sensitivity index m of Sn-Bi binary alloys. Tensile tests were conducted at 25, 40, 60, and 80℃ under different crosshead speeds to measure the index m. The results showed that the index m increased with both the concentration of Bi and the test temperature. At 60 and 80℃, the index m of Sn-Bi alloys exceeded 3.0, which is the threshold of superplastic deformation behavior. The eutectic microstructure of Sn-Bi was found to have a significant effect on the superplastic deformation in hypoeutectic Sn-Bi alloys.

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 To improve the penetration depth and welding efficiency of TIG welding, we have proposed the “Electromagnetic Controlled Molten Pool Welding Process” （hereinafter referred to as ECMP method）. Until now, by utilizing the electromagnetic force generated when adding an external magnetic field to the current flowing in the arc and the molten pool, it has become possible to increase the penetration depth, albeit under very limited conditions. However, the penetration depth varies greatly depending on the distribution of the external magnetic field and the position of the magnetic poles, and the slight differences in these conditions could result in a shallower penetration depth. In this study, in order to elucidate this mechanism, we observed in detail the effects of the external magnetic fields on the arc, the surface flows of molten pool, and the bead shape. In addition, since it is clear that the flow within the molten pool has a large effect on the penetration depth, we directly observed the flow within the molten pool by the X-ray transmission observation. As a result, when a negative magnetic field was applied that inclined the arc backwards （at which time electromagnetic force was generated in the arc in the opposite direction to the welding direction）, the penetration of TIG welding increased and this mechanism was clarified from the observation results of the flows within the molten pool.

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