Ultrasonic Friction Power in Microelectronic Wire Bonding

Abstract

An integrated sensor method is used to measure interfacial temperature profiles with an ultrasonic friction test process. The profiles are compared to numerical results obtained by a transient thermal 2D axisymmetric finite elements (FE) analysis. In the experiments, the 50 $m diameter gold balls used in wire bonding are deformed by the capillary tool during impacting on the flat surface of a silicon chip (contact zone). The deformed balls then are pressed onto the SiO2 layer on the chip and vibrated with various amplitudes of 128 kHz ultrasonics. The 52 $m diameter contact zone is surrounded in 14 $m distance by a 50 aluminum resistor which is used as a resistive temperature detector. Temperature increases of typically 0.18 K and up to 0.3 K are measured by the sensor close to the heat source at the contact zone, corresponding to 3.1 K and 5.2 K at the interface as suggested by the FE model. With typical bonding parameters, the contact zone friction power is determined to be 4.4 mW which is less than 2 % of the electrical energy delivered to the used ultrasonic transducer type.