Recently, I was working on a client project where I had to decide between using thermal pads or thermal paste for a custom heat dissipation solution. It’s a decision many engineers face, and I thought it’d be helpful to break it down here.
Basics first. Transferring heat is critical to ensure your electronics last longer and perform better. It can be SoCs, LEDs, Power MOSFETs etc. Both thermal paste and thermal pads are materials used to fill microscopic air gaps between a heat-generating component and a heatsink. But when should you use one over the other?
Thermal paste/Thermal grease is a viscous material that provides great thermal conductivity. It’s often preferred in cases where the contact surfaces are perfectly aligned or where you require maximum heat transfer. Since they are in paste form they virtually have no “thickness” so the metal heatsink technically has max contact with the heat source for maximum heat transfer.
Thermal pads are pre-formed, solid sheets of thermal material that are easy to apply and is not messy to use at all. Here the overall heat transfer is less because this material has some thickness and it acts as an insulator between the heat source and the heatsink. So why would you want to use this if conductivity is lower? It’s for those cases where you can’t have flush contact between the heatsink and the source for different reasons like non-flat surface due to manufacturing tolerance or if you are using the same heatsink for multiple ICs of varying heights. The spongy nature of thermal pads handles this height variation. Another great thing is it doesn’t dry out over time. Make sure you choose thermal pads of the minimum thickness possible.
In summary, both materials have their place. If max heat transfer is needed and surfaces are flat go for thermal grease, else use thermal pads. Hope this helps.
