Photo-imageable-dielectric (PID) materials and the Micro-filled Via (MfVia) technology are utilized to make the ViperBGA (VBGA), a thermally enhanced BGA package substrate. The thermal performance of the VBGA packages was evaluated by wind tunnel tests of JEDEC standard and FEM simulations. It is shown that the thermal resistance Θja of any given package can be approximated by a rational function of the power level and the airflow speed. One advantage of such expression is that the thermal resistance of the package under any condition can be confidently predicted, and the other is that more reliable numerical predictions can be achieved. This paper also describes how to approach a confident FEM modeling of the wind tunnel tests in terms of heat transfer coefficients and other factors.

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