Salt hydrate based thermal energy storage material, Na2HPO4·12H2O, was studied for thermal management of electronics. Such a material usually has a poor thermal conductivity and hence was filled in a metal foam to enhance the thermal conductivity. Copper sheets with varying thickness were used to study the heat spreading effects on the heating module. With different levels of heating power, the temperature difference between the middle and the edge of the copper spreader was monitored. The results showed that an increase in the thickness of the copper sheet decreases the temperature difference. With 6W heating power, a 0.5 mm thick copper sheet should be used if the required temperature difference is less than 4 ℃. A heat storage module with a dimension of 30 mm×30 mm×7 mm could work for 10 minutes without overheating above 70 ℃. Simulations were performed with both one-melting-point model and two-melting-point model. The results showed that the two-melting point model worked better than the one-melting-point model at a low power, whereas little difference between the two models were seen at high powers.