Copper strips plated with Sn-Pb eutectic solder were hot pressure-bonded to gold thin-film wiring. It was proven that a Au-Sn alloy forms at the interconnection between the gold thin film and the copper strip, but that there is virtually no Pb present in the interconnection. Au, Sn, and Pb were observed on the surfaces of the copper strips and the gold thin film outside of the connection area.

There are several kinds of semiconductor chip bonding methods--wire bonding, TAB, and flip chip bonding--and each is used in applications in ways which utilize its individual characteristics. Wire bonding is inexpensive and imposes fewer restrictions on wiring, but when used with conventional technology, it has been difficult to narrow the bonding pitch. The authors challenged themselves to develop a 40µm pitch wire bonding technology for use in development of a 600 DPI (dots per inch) LED print head. To accomplish this, a high strength ultra fine wire with a diameter of 10 µm was developed and a suitable wire bonding technology using that wire was determined. Finally, the targeted 40 µm pitch wire bonding technology was established.

Change in film properties, especially resistivity and the thermal dependence of resistance, that are due to differences in the thickness and the temperature of heat treatment of Ta-Si-C films developed as high resistivity materials were investigated. From these results, the mechanism of film thermal changes was discussed. Further, the effect of film thickness on the performance of Ta-Si-C thin film thermal printing heads was also investigated. The results show that; (1) a ln ρT-1/2 relationship between resistivity and temperature in Ta-Si-C thin films holds good over a wide temperature range from 293 to 873 K, (2) resistivity is dependent of film thickness when film thickness is less than 2000 (greater resistivity in thinner films), (3) the thermal dependence of resistance is dependent on film thickness when film thickness is less than 3000 (greater thermal dependence in thinner films), (4) resistivity is increased and thermal dependence of resistance is decreased by heat treatment below 400 , and that (5) excellent performance is achieved when Ta-Si-C thin films greater than 3000 in thickness are used as the thermal printing head resistor film.

I have examined factors for implementing a high-speed, low-power-consumption thermal head. In conventional thermal heads, a heat insulation layer is provided between the heating resistor and the radiator. I found it desirable to implement fast operation and low power consumption to lower the thermal conductivity of the heat insulation layer and to thin the heat insulation layer. I also found there is an optimum heat characteristic to the thickness of one heat insulation layer. I assumed polyimide as a material for the heat insulation layer which could materialize the hypothesis, and studied necessary items based on the thermal calculation. I manufactured a trial thermal head on the basis of this result and confirmed that our assumptions were correct. In addition, to confirm that the assumption is also ultimately correct, I fabricated a trial thermal head only consisting of a heating resistor and without a protective coat and a heat insulation layer. I confirmed that the structure with only the heating resistor exhibited excellent heat response and consumed less power necessary for heating.