Thermal performance of IMS™ dielectrics: data and prediction

Copper clad insulated metal substrates (IMS™) can be a solution for thermal problems caused by high power density. An IMS is a metal board laminated to a circuit layer with a thermally conductive dielectric. The dielectric´s thermal conductivity and thickness are critical to the thermal performance of the electronic assembly. These parameters were experimentally evaluated using a TO-220 package as a heat source. In addition, a detailed model was built using the CFD software Flotherm™. The predicted thermal performance matches the data well if experimental data is used to correlate the model. This study indicates that for a given dielectric thickness, the thermal impedance reduces to its asymptotic value at a characteristic thermal conductivity. For a relatively thin dielectric of 75 μm, a thermal conductivity of 4 W/m-K is sufficient, while for a thick dielectric of 250 μm, maximum performance is not achieved until about 8 W/m-K.