Thermal pad
A thermal pad , like thermal paste, is used to better dissipate the heat loss from electronic components. Some designs allow electrically insulated mounting on a heat sink .
General
When operating electronic components , especially in power electronics , there are sometimes very high power losses that cannot be dissipated via the free-standing housing of the component alone. The components are therefore provided with heat sinks . When mounting on these heat sinks, air spaces always remain due to unevenness, which strongly impede the transfer of heat . It is therefore also the task of the thermal pads to displace the air from these spaces and thus improve the heat transfer.
An insulation between the heat sink and the surface of the component used for heat dissipation is often required, u. a. because these surfaces often have different electrical potentials. The insulating washers used for this can also be counted as heat conducting pads, since they are made of electrically insulating, but highly heat-conducting materials. As a rule, however, they also require the use of thermal paste.
Executions
Different materials are used depending on the requirements.
- Electrically isolated assembly:
- Silicone rubber sheets and sleeves, some with glass fiber fabric insert;
- Large-area silicone mats for heat-conducting and vibration- damping assembly, for example between SMD- equipped circuit boards and heat sinks or housing parts that serve as heat sinks; The thermal conductivity is around 5 W / (m · K).
- Mica washers ;
- Ceramic discs (mostly aluminum oxide ceramic);
- Plastic films ( Kapton ), some of which are packaged with a paraffin coating to fill air spaces by melting during operation or with a self-adhesive coating.
- Uninsulated assembly:
- Thermoplastic pads as an alternative to thermal paste (e.g. for processors ); they melt during operation due to the heating and thus adapt to the unevenness.
- soft metal foils, e.g. B. from indium
- Graphite foils
literature
- Chakravarti V. Madhusudana: Thermal Contact Conductance . 2nd Edition. Springer, 2013, ISBN 978-3-319-01276-6 .
Web links
Individual evidence
- ↑ Technical data sheet, Keratherm 86/60 thermal conductive film. (No longer available online.) Archived from the original on April 8, 2016 ; Retrieved September 25, 2014 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ http://www.cmr-direct.com/de/indium-foil/cmr-in50um-100x100mm Offer indium foil with instructions for use, website of CMR-Direct (Great Britain)
- ↑ http://www.kerafol.com/thermal-management/keratherm-produktuebersicht/keratherm-grafitfolien/ Information from the company Keramische Folien GmbH (Germany) on graphite foils
