In-situ calibration of wire bonder ultrasonic system using integrated microsensor

Based on investigations with an ESEC thermosonic wire bonder, we report a novel ultrasound calibration method which consists of in-situ measurement of the friction heat generated by the gold ball as it scrubs on the oxide of an integrated microsensor. This procedure can be carried out in-process using a dedicated test chip and a modified clamping plate. The calibration dependence on the process parameters of bond force, ultrasonic energy, and initial ball diameter is quantified. The test chip-to-test chip standard variation of the calibration signal taken from a single wire bonder corresponds to a horn amplitude variation of 0.01 μm