thermal gap filling pads
At NEDC we cut a lot of thermal gap filling pads. One of the frequent questions we get is “Why are many thermal pads not available with pressure sensitive adhesive?” The answer comes back to the whole purpose of the thermal pad itself.
Attachment Methods- Natural Tack versus PSA (Pressure Sensitive Adhesive)
Thermal Interface Materials are designed to reduce air-gaps, and provide a good interface to transfer heat through the material, and then out of the application. For self-attaching methods, there are two options. There is a natural-tack, and there is pressure sensitive adhesive(PSA):
Soft-Tack/Natural-Tack on Gap Pads
Soft-Tack: Many gap filling pads come with a natural tack on at least one side. Most thermal gap fillers come with a natural tack on both sides. Many of the natural tacks that are available on thermal gap filling pads are sufficient for staying power and sometimes act as adhesives. I have stuck metal plates together with Gap Pads, and upon heating have been unable to remove them from each other without strong intervention. We have seen customers apply thermal gap filling pads using strictly their natural tack to metal enclosures for example. Most Gap Pads are available with natural tack on both sides. There are two Sil-Pad options with natural-tack, Sil-Pad 1500ST, and Sil-Pad 1100ST. The natural tack is a good solution to allow attachment and surface wetting without the costly thermal impeding PSAs. You may ask the question, Does Natural Tack Improve Thermal Performance? It sure does! In most cases by up to 0.5 W/m-K. In the case of Laird, they offer a “deadened tack” on one side which is designated by “DC1”. For more information on DC1, and deadened tack, you can find that here.
thermal gap fillers
thermal gap fillers
Pressure-Sensitive Adhesives(PSAs) on Thermal Gap Fillers
Gap Pad VOUS, Gap Pad VOS, and Gap Pad VO by Henkel are all available with a natural tack on one side with pressure sensitive adhesive coating on the other. The pressure sensitive adhesive oftentimes increases the thermal resistance by a small amount that can start to make a large difference in the application. According to Henkels’ Sil-Pad Selection Guide one layer of adhesive could easily increase the thermal resistance by 0.2C/in2/W. However, there are thermally conductive adhesive coatings(TAC) that will help to reduce this thermal resistance a little – although it still leaves more thermal resistance than without it. We did an independent test at NEDC to answer this question as well. Although some pressure sensitve adhesives are available as “thermally conductive adhesive”, it is good to think When it comes to adding a pressure sensitive adhesive to an application, its good to keep in mind that you should compensate with a higher performing thermal pad because in some cases of thin thermal gap pads, PSA can really hurt the thermal performance because the apparent thermal conductivity goes down a lot.
More Information on Thermal Gap Fillers
NEDC die-cuts, and waterjet-cuts thermal interface pads for customers. For more information on thermal gap filling pads, and their attachment methods, please contact sales@nedc.com.