Abstract
In recent years, in an effort to prevent global warming and to achieve energy saving, power modules have become common not only in transport equipment but also in home electronics. In these semiconductor packages, large-scale ceramic substrates are bonded on copper heat sinks to control high voltages and high currents. In this paper, we report on a new experimentally developed bonding process realizing void reduction in solder joints. A ceramic substrate having high-temperature solder bumps on slit pads was mounted on a heat sink printed with low-temperature solder paste. The solder bumps are then reflowed. As a result, the solder joints have fewer voids than conventional methods. Moreover, the mechanism of void extinction is revealed using X-ray dynamic observation.
