Thermally conductive adhesive for electronics applications

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  • Electrically insulating one-component silicone adhesive
  • Thermal conductivity of 4.3 W/mK
  • Applications: power electronics

Wacker has developed a new thermally conductive adhesive grade for electronics applications. The new silicone rubber with the trade name Semicosil 975 TC features 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 very good heat dissipation by the heat sink.

thermally conductive adhesive is applied to the electronics component

The thermally conductive Semicosil 975 TC silicone adhesive from
Wacker is applied to the heat sink. As the electronic component is pressed
on, the adhesive forms a thermal interface (TIM). The adhesive layer transfers
the heat of the device efficiently to the heat sink. (source: Wacker Chemie AG)

One-component adhesive: electrically insulating & thermally conductive

The material is an addition-curing silicone rubber that 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 4.3 W/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 material 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, Semicosil 975 TC, 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.

Minimum layer thickness between 90 and 100 micrometers

The rheological flow properties do 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.

thermally conductive silicone adhesive bonds parts mechanically

Tightly packed semiconductor components, such as IGBTs, in motor controllers and LED packages can become very hot. Such components are mounted on heat sinks to prolong their lifetime. The thermally conductive silicone adhesive from Wacker bonds the parts mechanically and ensures optimum heat transfer.
(Source:  Wacker Chemie AG)

Application: to fix semiconductor devices on heat sinks

Semicosil 975 TC is thus very suitable 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. In addition, the adhesive layer compensates for microscopic irregularities in the surfaces, thereby maximizing the contact area and, due to the product’s high thermal conductivity, optimizing heat dissipation.

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