Toshio Hatsuda

Corrosion Behavior of Copper in Liquid Perfluorocarbon.

Liquid perfluorocarbon coolant Fluorinert® FC-72 for electronic devices has high thermal stability and low chemical reactivity. However, the presence of water in FC-72 at less than 10wt ppm has been shown to appreciably increase copper corrosion. In the present study, the corrosion mechanism under low solubility of water in FC-72 was investigated by chemical analysis, water volume measurement, and corrosion testing. It was found that FC-72 liberates no decomposition products in temperatures below 100°C and copper corrosion depends on liquid temperature, dissolved water, and oxygen. In FC-72, copper specimens were corroded by wet oxidation at temperatures of 50, 70, and 85°C and by both wet and dry oxidation at 100°C. Copper corrosion was induced when dissolved water in FC-72 was increased to more than 8wt ppm. However it was reduced when oxygen in FC-72 was decreased to less than 25ml/L. Dissolved water in FC-72, as in air, equilibrates with adsorped water on copper surface. Therefore, the mechanism of copper corrosion in FC-72 is the same as that in air. It is considered that the mechanism for FC-72 can be extended to explain corrosion behavior in almost all inert coolants.

Development of mechanical fatigue test method for flip-chip solder joints

A controlled displacement mechanical fatigue test machine for specimens of flip-chip solder joints has been developed using PZT actuators. The extension response of the PZT exhibits good linearity using a charge control circuit. As a result of this control, errors in the strain of the specimen caused by the deflection of the test machine frame can be corrected by measuring the load. This test machine produces a cycle constant strain range in the solder joints. A fatigue test is conducted for specimens of flip-chip solder joints, and the fatigue strength of the joints is obtained. The strength of the joints seems to be higher than that of bulk solder.<<ETX>>