Packaging of To 247-4 Package

Swadish

We are using C3M0016120K in one of our designs, we are dissipating approx 40W from the device. We are heatsinking the bottom of the mostfet using a thermal grease, we wanted to know how much of the heat goes out through the copper paddle and how much of the heat goes out through the leads to the PBA?

AAnders

The amount of heat that will flow through the leads and into the PCB will depend on a number of factors in the design including the RMS current in the device, the thermal properties of the PCB, the lead length, and the thermal properties of the heatsink and interface. The leads are a high thermal impedance path in comparison to the drain tab of the device since the cross-section of the leads is small, and the length is much greater than the drain tab thickness. In some cases if the device has high RMS current, the power dissipated in the leads (I^2*R) may actually cause the leads to run hotter than the case temperature, in that situation, some heat would flow into the package from the leads.

In general, however, the amount of heat flow through the leads (in either direction) for a TO-247 device is negligible if the device is mounted to a heatsink with relatively low thermal impedance.