Thin film thermal sensor for real time measurement of contact temperature during ultrasonic wire bonding process

Abstract

Abstract The slender, thin film, K-type thermocouple, fabricated through sputtering deposition, is employed to probe the contact temperature of the frictional interfaces during the ultrasonic wire bonding process. This thin film sensor is of thickness of 1 μm and with three different line widths that are 100, 80 and 20 μm, respectively. Contents of the sensor were demonstrated to be similar to the original K-type targets. Comparison of the thermoelectric relation of the sensor before and after the bonding processes ensured that the sensor operated appropriately during the bonding process. To help the analysis, modeling the temperature variation of the sensor based on a lumped system was also presented and discussed. Results show the currently fabricated sensor worked very well for the contact temperature measurement during the bonding process. For the same bonding condition, the recorded temperature increased with the reduction of the line width of the thermal sensor. The lumped system analysis indicated this increasing was mainly contributed by the reduction of the thermal inertia in the junction region that resulted from the decrease of the line width. With the advantage of the thin film thermal sensor, more sensitive and less invasive, the current measurement acquires temperature rise up 300 °C at the duration of bonding that, at least, is 150 °C higher than the available data in the literatures. Measurement result obtained by the present slender, thin film, thermal sensor is believed more close to true contact temperature.