Tomoaki Goto

Development of copper-copper bonding by ultrasonic welding for IGBT modules

In this paper, we present the copper-copper bonding technique by ultrasonic welding for the copper terminals of large current, high reliability IGBT modules. Investigated topics are joint strength indicated from joint microstructure, the effect of copper hardness on joint strength, the relationship between terminal bonding location and the damage to the insulator layer in the module sutructure, and reliability estimation of large IGBT modules with ultrasonic welding comparing with conventional soldering.

Interface Properties of Thin Film Bonding by Low Melting Point Metal for MEMS devices

Low temperature metal bonding is promising for assembling micro devices because the interface can easily achieve high mechanical reliability by the formation of metallurgical and electronically high conductive interfaces. For gaining high strength of micro joints with low temperature process, vacuum deposited low melting point metal (Snxln1-x) thin films were applied to solid-liquid diffusion bonding of copper. The effects of Sn content on the growth of reaction layer and on the shear strength were investigated. It was found that the sufficient initial Sn supply was important to achieve high strength interface characteristics to enhance solid-liquid diffusion.

Influence of die adhesion properties on delamination of stacked chip interconnection encapsulated in plastic package

The chip-on-chip (COC) package in which a controller IC chip is adhered to a power MOSFET chip with a polyimide film is described. In the heat cycle test, the polyimide film showed a good performance but the mold resin used was delaminated from the IC chip surface. From the experimental and the thermal stress simulation, we demonstrate that the resin delamination is prevented by the polyimide film with a small thermal expansion coefficient. Thus we have successfully developed the high reliable COC package promising for automotive application.

DIELECTRIC PROPERTIES OF Pb(Zr,Ti)O 3 CERAMICS PREPARED BY PULSED ELECTRIC CURRENT SINTERING

Application of the piezoelectric element to the MEMS devices is one of the promising techniques finely drive them as a sensor. In this paper, thick PZT Pb(Zr,Ti)O 3 piezoelectric layer was prepared by using the pulsed electric current sintering (PECS) process. The effect of synthesizing parameters on the microstructure and dielectric properties of the obtained PZT layer was discussed. It was confirmed that PECS enabled the densification of PZT particles at a lower temperature for a shorter time than slurry printing method. Moreover, the obtained PZT compacts exhibited comparable dielectric properties with those obtained by conventional sintering. However, it should be noticed that the PECS in a vacuum atmosphere caused the loss of oxygen in PZT structure resulting to the degradation of dielectric properties.