Research On Induction Local Heating For Mems Packaging

Induction local heating mainly bases on the three basic principles, including electromagnetic induction, skin effect and heat conduction. Because of the electromagnetic induction heating's selective and rapid characteristics, the Joule heat caused by eddy current is concentrated in small local areas and melts only the solder layer, the temperature of chip area keeps low. This heating method can effectively reduce the heat and stress effect on the chip and the temperature-sensitive circuits; correspondingly, it will enhance the bonding quality and efficiency.The feasibility of induction local heating for MEMS packaging is proved based on theoretical study, numerical simulation and experiments in this paper. The detailed contents for this article are as follows:1) The basic principles of electromagnetic induction heating and wafer level packaging were introduced and studied. It is found that there was great difference for electromagnetic induction local heating to apply in wafer-level packaging and chip packaging. In order to ensure temperature uniformity, wafer-level packaging should use a uniform alternating magnetic field.2) Induction heating is a complicated nonlinear research topic because the physical properties of materials change with temperature. In this paper, the simulation of induction heating adopts non-direct coupling method to calculate the coupling effect between the temperature field and the electromagnetic field. An analytical model of electromagnetic and thermal field was presented based on a simplified method.3) High-frequency and RF induction heating system was designed. Various components including inductors offering uniform magnetic field, sensor power supply, impedance matching, vacuum chamber and fixtures were designed and fabricated, then an induction heating packaging system were integrated based on the above components.4) The selectivity and uniformity of induction local heating were proved by numerical simulation and experiments, which ensure the feasibility of its application in MEMS packaging.