Experimental and Numerical Thermal Analysis for Advanced Flip Chip Thermo-Compression Bonding via CMOS Microsensor Arrays and Finite Element Modelling

Abstract

Thermo-compression bonding (TCB) relies on uniform thermal distribution during microelectronic packaging processes to ensure reliable interconnects are formed. During any TCB processes, the thermal application must uniformly distribute heat in order to produce robust, thoroughly bonded packages without being damaged due to thermo-mechanical effects. To better control and develop TCB processes, further insight through thermal analysis is required. Due to the form factors and complexity involved in TCB, it is difficult to accurately extract viable information such as temperature variation, lateral and vertical gradients, or interfacial bonding temperatures. To extract real time in-situ temperature and force signals, a microsensor array was used to observe any thermo-mechanical features recorded during emulated TCB processes. Algorithms were developed to post-process the signals and produce quantifiable data. Finite element models were developed to verify the experimental thermal responses and subsequently post-analyze the numerical results. Models formed through hybridized contact resistance layers as well as surface contact models are also discussed. Several features were identified and quantified: maximum heating rates, location of maximum lateral thermal gradients, internal joint thermal distributions, knee-region slope analysis and joint to joint thermal variation. The experimental responses in combination with numerical analyses show evidence that thermal applications during TCB is robust. Low thermal variation was found with respect to joint to joint temperatures. Chip design was found to heavily influence cooling on the periphery edges of the bump array. The sensor chip temperatures were to found to be about ≈ 6 °C lower than the extracted bump temperatures, signifying the use of microsensor arrays could be developed as accurate tools for thermal process control during TCB.