Experimental and numerical studies of transient heat transfer in electronics packaging
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Date
2016-09-01
Authors
Ong Kean Aik
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Abstract
The demand for mobile and tablet devices is at all time high for the last decade, overwhelming attention has been paid to this field, the novelty studies that needed in industry to accompany this demand is to characterize the steady state and transient studies for satisfactory thermal performance on these devices, and ensuring reasonable thermal qualification time for chip and better production outputs. The part one of this study presents the steady state forced air thermal simulations with the attachment of heat spreader for various die power conditions (0.5W to 2.0W), the steady state thermal model has successfully been developed and optimized, and thermal contour for each die power was demonstrated. The simulated thermal model at steady state has been verified by thermocouple-measured junction temperature, with the maximum percentage difference at 6.02% only; the verified thermal model has been extended to characterize the thermal impacts of the various air flows on the resistance from die to the ambient. It utilizes heat path resistance network and simulation in a holistic manner for accurate thermal analysis. The results show that the heat path resistance from die to ambient is a function of air flow but not the die power, higher air flow will reduce the thermal resistance from die to ambient, and for this study the minimum thermal resistance obtained at 5.90C/W for maximum air flow.
The part two of this study has been extended to transient heat transfer simulation, with the intention to understand what is the auxiliary heat source that required for the junction temperature to achieve 700C at transient mode? The auxiliary heat source is
crucial in helping to reduce the qualification time of chip. Sufficient understanding of transient heat transfer paths within the die has been demonstrated though the creation of thermal contour with various heat sources. An auxiliary heat source prototype has successfully been developed and tested. And the transient thermal model has also been verified with the thermocouple-measured transient time, the simulated transient time is within 11% of the experimental measured values. The data shows it requires 22W of auxiliary heat source and takes 69.65s for the junction temperature to reach 700C from room temperature, this is a very significant achievement that can be applied in chip qualification. The study of verified transient model has also been extended to the effects of various transient times (15s to 75s) and heat sources (7W to 27W) to the heat path resistance from the die to ball, the heat path resistance from die to ball is a function of transient time, in which thermal resistance from die to solder ball increases with transient time; however, at any specific time thermal resistance will not change with various heat sources.