LIQUID ENCAPSULATED MCM PACKAGE - THERMAL DEMONSTRATION

This experimental study was undertaken to demonstrate the capability o f liquid-encapsulated system in its simplest form of implementation to cool a multichip module (MCM) package, The MCM package was made of ko var (dimension: 58 x 35 x 11 mm), Two silicon thermal test chips were bonded to an FR-4 board and housed inside the metal package, Tests wer e performed on both dry (no liquid-filled) and liquid-filled packages, In the liquid-filled situation, either a pure dielectric liquid or a dielectric liquid mixture was employed, The MCM package was externally cooled by either free-air or forced-air (1.0 to 2.54 m/s of air how), Heat transfer history from single-phase, through nucleate boiling, to film boiling was documented. The overall improvement for the liquid-f illed package was 2-4 times compared to the dry package, due to the su perior thermal properties of dielectric liquids compared to air, The m aximum power dissipation in the liquid-filled package at 2.54 m/s exte rnal air flow was 18 W (based on junction temperature maximum of 125 d egrees C), In the liquid-filled package, both the single-phase and boi ling heat transfer were enhanced by varying the external boundary cond itions from free-air to forced-air, The total power dissipation limit in the liquid-filled package is strongly influenced by the ability to condense the vapor in the package, By changing the boundary conditions from free-air to forced-air (2.54 m/s), the condenser (top lid) effic iency is raised, thus raising the maximum power dissipation by 2.5 tim es. Results also indicated that for any given external boundary condit ion, the allowable power dissipation did not vary much under different liquid conditions: nondegassed liquid, degassed liquid at slightly ab ove ambient pressure, and degassed liquid at ambient pressure, When th e system was sealed, increasing power in the package created large liq uid pressure and raised its boiling point, The dies remained in the si ngle-phase regime and no boiling occurred.