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Saturday, 21 September 2019
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Raw materials & technologies, Applications

Thermally conductive adhesive for electronics applications is easy to apply

Tuesday, 18 November 2014

The Wacker chemicals group has developed a thermally conductive adhesive for electronics applications.

The new thermally conductive silicone adhesiveis applied to the heat sink. Source: Wacker

The new thermally conductive silicone adhesiveis applied to the heat sink. Source: Wacker

The new silicone rubber with the trade name "Semicosil 975 TC" is characterised by high thermal conductivity and good flow and processing properties. Even light pressure is enough to form an ultrathin adhesive layer between the contact surfaces. This ensures not only good bonding, but also good heat dissipation by the heat sink. The product is an interface material for forming thermal and mechanical connections in power electronics components or packages.

Silicone rubber cures at temperatures above 90°C

The one-component adhesive is electrically insulating and adheres to many of the substrates used in electronics. One of its key characteristics is its high thermal conductivity of 4.3W/mK (as per ASTM D5470). It also offers good processability, despite the fact that it has a high filler content which is necessary to achieve the requested thermal properties. Before it cures, the product is a very pasty, non-sag material that becomes progressively free-flowing with increased shearing. This property can be precisely adjusted to processing requirements. As a result, it – unlike comparable previous products – can easily be fed at low pressure, and applied as a bead. It can be processed directly from the pail or from a regular cartridge.

Offering advantages for further processing

The rheological flow properties of the adhesive also offer advantages for further processing. When a part is pressed in place, the applied silicone forms an ultrathin adhesive layer which conforms to the substrate surface without the need to apply high force. The minimum layer thickness (bond line thickness) that can be applied is between 90 and 100 micrometers, with its usability depending on the design of the interface.

It is thus good for use as a thermal interface material in power electronics. The purpose of such materials is to fix semiconductor devices – such as insulated-gate bipolar transistors (IGBT) – in engine control units and LED components on heat sinks in order to dissipate the heat. Without heat dissipation, the service life of electronic devices would be considerably impaired. As a thermally conductive adhesive, it reliably couples the electronic component to the heat sink. The adhesive layer compensates for microscopic irregularities in the surfaces, thereby maximising the contact area and – thanks to the product’s high thermal conductivity – increases heat dissipation.

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