Intrinsic-Thermocouple Process Monitor
Original Publication Date: 1987-Apr-01
Included in the Prior Art Database: 2005-Feb-01
In order to replace the ultrasonic wire bonding technique which requires the coating of heavy gold on EC pads, laser welding using fiber optics has been developed. The figure shows this technique in which a continuous laser beam 10 of short duration (<1 sec) is delivered via an optical fiber 12 to heat a tungsten tip 14 which, in turn, melts the gold-coated copper wire 16 (60 microns in diameter) and bonds it to the EC pads 18 on the alumina or glass ceramic substrate 20. To minimize oxidation of tungsten tip 14 at elevated temperatures, it is highly desirable to heat the tip with an amount of laser energy which is just sufficient to achieve good bonding between EC pad 18 and copper wire 16.