The Thermal Conductive Pathway In Epoxy Encapsulants For Electronic Packaging And Its Properties

The polymeric sponge method was used for producing reticulated ceramic using alumina as raw material in this paper. The optimized ceramic slurry was chosen and the structure as same as the sponge was obtained in reticulated alumina. Then a reticulated alumina was filled in epoxy material to obtain the composite using encapsulating method. The microstructure, thermal conductivity, coefficient of thermal expansion(CTE) and dielectric constant were tested by scanning electron microscope(SEM), unidirectional steady-state thermal conductivity measurement, PCY-â…¢instrument and high frequency Q measurement. Finally, ANSYS was used for thermal simulation of the reticulated structure models. And the results were compared with experiment data. Experimental results show: i) The optimum solids content and polymer content are found to be 60 and 2.0wt.% for 50 ppi sponge and 65 and 2.0wt.% for 20 ppi sponge. After sintered under 1500°C, alumina reticulated ceramic which contains alumina crystal phase is obtained with continuous reticulated structure. The porosity is 87.4% and 92.5% respectively. ii) For reticulated ceramic reinforced epoxy, thermal conductivity reaches 0.55 and 0.79 W/m?K which volume fraction of fillers is 7.5and 12.6vol.% respectively. It is 3.6 and 5.2 times higher than particles filled epoxy with the same volume fraction. The coefficient of thermal expansion (CTE) decreases as low as 27.56×10^-6/°C and 22.34×10^-6/°C, which is 70% lower than particles filled epoxy. The dielectric constant is between 4 and 5. After filling Al₂O₃ and Si3N4 particles in epoxy, the thermal conductivity increases as linear. iii) Comparing with theoretical predict, Calmidi model is accurate to reticulated ceramic filled epoxy when A is 0.25, and Agari model is accurate to the part whose volume fraction is larger than reticulated ceramic. iv) The reticulated structure model is fabricated by cutting spheres of BCC, FCC or A15 in a cubic by using ANSYS software. The simulant results show that A15 is accurate to experiment results. Simulant results rapidly increase when reticulated ceramic's thermal conductivity is between 50²00 W/m?K, and it gradually begins to keep steady when it is larger than 500 W/m?K.