thermal gap filler pads
It is no secret that NEDC has a thermal pad test machine at its facility in Methuen, MA. We test a lot of thermal pads. We stack them, sort them by apparent thermal conductivity, by bulk thermal conductivity, test with liners, without liners, with PSA, without PSA… In this blog, we decided to make the distinction between Tack, and No-Tack. Some thermal interface pads have a tack on one side. Some thermal gap filler pads have tack on both sides. Some of tack neither side. In this distinction, we wanted to show how the inherent tack affects the ability of the material to conduct heat.
What is Tackiness on One Side Supposed to do?
The inherent tackiness on the backside of material is supposed to help the material wet-out onto the topography of the surface, and create better surface contact. When doing this, it lowers the thermal impedance, and drives better overall thermal performance. However, not everyone wants tackiness on their thermal pad.
Why would one want “No-Tackiness” on their Thermal Gap Filler Pad?
Tackiness can easily get in the way when placing a pad into an application. In fact, when I’m placing a thermal pad inside the testing unit, tackiness can become extremely frustrating- and oftentimes I end up ruining pads.
How did we Test These Pads, Tack, Non-Tack Thermal Pads?
We thought it was important to test these pads with as little pressure as possible. We tested at 5 psi, 10 psi, and 20 psi. We did this to allow the pad to wet-out through the natural tack that is present in the pad. While we knew that extra tackiness would cause the pads to perform better, we wanted to see how much better than actually performed. These values were expressed in Apparent Thermal Conductivity. Here are the results:
| Product | Tacky One (DC1) Side (5, 10, 20 psi) | Tacky Both Sides (5, 10, 20 psi) |
| TFlex 660 | 1.97 W/m-K, 2.02 W/m-K, 2.30 W/m-K | 2.25 W/m-K, 2.33 W/m-K, 2.64 W/m-K |
| TFlex 360 | 1.13 W/m-K, 1.10 W/m-K, 1.11 W/m-K | 1.19 W/m-K, 1.20 W/m-K, 1.19 W/m-K |
Discussion:
I was surprised by the amount of difference in thermal performance that having a little tackiness can provide. Why does this happen? Tackiness allows significantly more wet-out than without it. In fact, unless it’s a very intricate part that you’re having trouble assembling- I’d always suggest to get the pad with the intentional tackiness on both side if you can.
More Information on Thermal Pads:
NEDC does die-cutting, knife-cutting, and waterjet cutting of thermal interface pads. For more information on thermal interface pads, or gap filling pads, please contact sales@nedc.com.