Heat-conducting silicone-based gap filler for electronics

WACKER launched its heat-conducting silicone-based gap filler material for the electronics industry at the Power Conversion and Intelligent Motion  (PCIM) electronics tradeshow Europe. Available under the tradename SEMICOSIL® 961 TC, the silicone rubber is ideal as an interface material for thermally connecting electronic circuits, ensuring effective heat management.

The material has  good flow and processing properties, while wear of the mixing and metering equipment used in its application is low.  With the new silicone gap filler material, WACKER is expanding its portfolio of thermal interface materials.

SEMICOSIL  961 TC is a highly filled, two-part silicone rubber that cures at room temperature via a platinum-catalyzed addition reaction to form a soft silicone elastomer with a tacky surface. The cured rubber achieves a thermal conductivity of two watts per meter kelvin and, at the same time, is electrically insulating.  

Before it cures, SEMICOSIL 961 TC is a non-sag material. However, its viscosity decreases with increased shearing, for example during mixing and metering. Its shear-thinning property is adjusted so that the silicone rubber can easily be fed by machine and applied as a bead. Processors can achieve a high metering rate and very high dosing accuracy.  

SEMICOSIL 961 TC ensures optimum heat transfer from the electrical circuit to a heat sink. In practice, the gap filler is first applied to the heat sink. The circuit board is then pressed on or fitted by means of a vacuum process. During compression, a continuous film forms that conforms snugly to the surfaces of the two joining parts. In this way, surface irregularities and tolerances can be evened out perfectly. Furthermore, the film maximizes the contact area and thus promotes heat transfer.  

The film cures to form a silicone layer between the joining parts. Thanks to its soft consistency, it ensures a reliable, tight fit even if there are frequent temperature changes and vibrations. In addition, the new silicone gap filler can be used over a wide temperature range. Its properties remain unchanged between -45 and +180 degrees Celsius. High thermal and thermal-shock resistance and the ability to absorb vibrations are important for applications in automotive electronics and electromobility, for example.  
 
SEMICOSIL 961 TC is a two-component system. Despite its high filler loading, it has a comparatively minor abrasive effect on the mixing and metering equipment used to apply it. This means that there is less abrasive damage to feed pumps, for example, than is usually the case with highly filled silicone rubber. Consequently, significantly longer service lives of mixing and metering equipment and major cost advantages in processing are possible.   

The new gap filler contains hardly any volatile components. In terms of fire-safety properties, tests show that the silicone product meets the specifications for classification V-0 as per UL 94 of Underwriters Laboratories. SEMICOSIL 961 TC is available in both Euro cartridges and 30-kilogram pails.