Abstract
Semi-conductor sensors requirh such conditions as high bonding strength, stability at repeated stresses and electrical insulation on their bonding parts. But several defects are found in solder materials now generally used, resines, low melting point glasses and gold-silicon eutectic alloys respectively.
This paper presents the investigations concerning the gold-copper-germanium ternary eutectic alloys as solder materials of semi-conductor sensors. The alloys have high bonding strength by forming super lattice of goldcopper alloys in the ternary eutectic alloys.
At first, theoretical stress analysis is carried out on the bonding parts with certain assumptions, and the following results are clarified for decreasing the zero point shift and hysteresis of sensors; (1) The materials with high shearing yield strength have to be used. (2) The thickness of solder layers has to be thinned.
After that, the experiments are performed on gold-copper-germanium ternary eutectic alloys. From these experiments, it is found that the tensile strength of ternary alloys increases by forming super lattice of gold-copper alloys in the ternary alloys and reaches 1GPa when copper contents are 19 wt%.
The liquidus temperatures of the gold-(17-19) wt% copper-(12-15) wt% germanium ternary eutectic alloys, approximately 700K, are as same as the heat-treatment temprature of cantilevers made of iron-nickel-cobalt alloys, and the performance of semi-conductor sensors containing canti-lever will surely be maintained in the most favorable condition.
Zero point shifts of the sensors are within ±0.1% after 107 cycles when repeated stresses of 1.5 times of full scale are applied.
