If you're looking to do research on thermally conductive epoxy resins the first thing you're probably going to do is a simple set of Google searches to get a feel for typical properties and values. To emulate this process, we did exactly that and collected information on over 50 thermally conductive epoxies from different formulators and suppliers. This post is dedicated to explaining the most common trends we saw among these products, to save you time in your research process.
Other Resources To Check Out:
- Thermally Conductive Adhesive Selection Tips
- Bulk Thermal Conductivity Values Of Typical Epoxy Filler Materials
- Don't Let A Thermally Conductive Adhesive's W/mK Fool You
1. Adhesive Formulators Don't Like To Tell You What Filler They're Using
This was by far the first thing we noticed. We had hoped going into the process that adhesive & sealant formulators would openly share the type of filler material they used in their epoxy formulation. But as it turns out, these formulators are a little paranoid about sharing too much information regarding their formulation. Only about 43% of all the thermally conductive epoxies we collected information on directly communicated the type of filler material they used in the TDS. Even within this 43%, many of the data sheets used generalized terms such as "nitride blend," and a data sheet will hardly ever tell you the typical particle size of the filler material used.
When in doubt, assume the filler is alumina. In our experience alumina is by far the most common material formulators use to increase the thermal conductivity of epoxy formulations. Its electrically insulating, relatively cheap, and moderately thermally conductive.
2. The Most Common Electrically Insulating Materials Are Aluminum Oxide and Aluminum Nitride
As we just said, alumina (aluminum oxide) is by far the most common filler used in thermally conductive epoxies. But aluminum nitride is a close second.
Boron nitride and diamond filled epoxies are much harder to come by. Our guess is that this is probably because these products are incredibly expensive, and as a result the market for these products is too small to justify a large product selection.
3. Electrically Insulating Epoxies Normally Fall In The Range Of 1.0 to 3.0 W/mK
As you can see from the chart above, the majority of electrically insulating materials fell in the range of 1.0 to 1.99 W/mK with the next most common range being 2.0 to 2.99 W/mK. This is about what you should expect as you go searching for an electrically insulating, thermally conductive epoxy material.
Exceptions to this rule include several aluminum nitride filled systems in the 5 to 5.99 W/mK range and a diamond filled epoxy made by AI Technology that claims to achieve 11.4 W/mK.
4. The Most Common Electrically Conductive Materials Are Aluminum & Silver
Both aluminum and silver make excellent thermal transfer fillers. Aluminum is a cheap way to boost thermal conductive and silver is the premium choice (comes at a much higher price point).
We only identified eight electrically & thermally conductive epoxies, but this is simply because we limited our options to the products that were specifically marketed as a "thermally conductive epoxy." Plenty of "electrically conductive epoxy" products exist that would make excellent thermal interface materials. If you're application can handle a highly electrically conductive material, consider searching for an "electrically conductive epoxy" instead.
5. Electrically Conductive Epoxies Are Able To Achieve Much Higher Levels Of Thermal Conductivity
As you can see there is a much wider range among this group of materials. Silver filled systems can commonly achieve 5-20 W/mK.
We did identify one extremely interesting silver filled system that claimed to achieve 60 W/mK. This a system developed by a company called Diemat, and as far as we can tell it is a one of a kind product.
6. There Aren't Many Thermally Conductive Epoxy Options On The Web
Overall we were a little disappointed by the number of products we were able to immediately identify while searching on the web. With such a limited selection its highly likely that the perfect material solution for your application isn't going to be easy to find. However, there is some good news:
- Many adhesive formulators don't describe their entire product selection online.
- Depending on the size of your application, most formulators will augment their products to better meet your application needs.
- We can help you find a product and supplier! That's what we do here at Cova Scientific, completely free. Simply click the link below to get started.