Explained Peter Swanson, M.D. at Intertronics: “Typically thermal transfer silicones are used for applications such as bonding heat sinks to processors, or LEDs to cases or heat dissipation devices. We see these generally requiring one of three levels of performance, usually with a price trade off and a balance to be found between flexibility and thermal conductivity.”
A good example is ACC AS1803, which is a single part thermally conductive silicone adhesive. It is a white paste, with a fast, neutral cure and good adhesion. It has excellent thermal conductivity of 1.55 W/m•K. It is used for electronics applications in aerospace, under bonnet automotive, consumer products and LED applications. Because of its neutral cure and the absence of any harmful by-products, ACC AS1803 is a perfect replacement for conventional oxime based silicone adhesives.
The natural properties of silicones have been enhanced in order to optimize their application in the thermal management process while eliminating corrosive action when in contact with sensitive metals such as copper.
Firstly they are valuable as adhesives, bonding components to heat sinks quickly and effectively without the need for mechanical fixing while eliminating the development of air gaps which would reduce performance. This approach has successfully been used to coat the back of large scale mega screen LED displays thereby offering environmental protection and effectively removing heat from the diodes.
Secondly, encapsulation and potting compounds are a very attractive option when trying to remove heat from a number of components within a single device. Thermally conductive silicones like ACC Q-Sil 553 are effective in a thermal transfer role in the manufacture of power supplies, under bonnet electronics and LED packaging. Non-setting compounds or “grease” do not set but offer heat dissipation capability plus a facility for easy rework or repair where this is considered an important factor. For further information please see www.intertronics.co.uk or visit their blog at www.adhere.uk.com.