Types of Silicone Thermal Transfer Materials

Using silicone polymers and specialty fillers, CHT has formulated a variety of materials that in addition to the ability to transfer heat, will also have some additional functionality which will be of benefit to the designer.

Adhesive Sealants

The benefits of having a thermally conductive adhesive mean you can permanently bond your component to some form of heat sink and eliminate the need for additional mechanical fastening systems. It will also prevent the possibility of movement and air gaps forming which will reduce performance. These products can also be used to form gaskets which will not only transfer heat but also form a seal against moisture and other environmental contaminants.

Silicone adhesives utilise two basic chemistries; condensation cure (RTV) systems which will cure at room temperature and addition cure 1-Part systems which require heat to cure.

Physical properties such as rheology, viscosity, hardness, colour, etc. ensure we can meet specific design requirements. With a flowable 1-part adhesive, it is possible to apply a coating with thermally conductive properties. This approach has successfully been used to coat the back of large-scale mega screen LED displays, offering environmental protection and effectively removing heat from the diodes.

As the adhesive will be in contact with sensitive metals such as copper, it is essential that there are no harmful, corrosive by-products such as acetic acid. CHT has developed a range of neutral cure adhesives with the electronics market in mind and have included a number of thermally conductive products.

For more information, view our Thermally Conductive Adhesives page.

Encapsulation and potting compounds

Using a thermally conductive encapsulant has become a very attractive option when trying to remove heat from various components within a single device. Selection of a suitable, flowable silicone will eliminate all the air gaps in and around components, thereby providing an effective path for the transmission of any unwanted heat. In addition to heat dissipation, silicone encapsulants also provide protection from harsh environments, vibration and thermal shock. Of particular interest is the new development of thermally conductive gels which reduce mechanical stress on delicate wire connections.

Typical applications include the manufacture of power supplies, under bonnet electronics and LED packaging. Encapsulation materials can be supplied as either 1 or 2-Part systems using condensation and addition cure chemistries. For a more detailed explanation of these chemistries, please refer to the CHT encapsulation application sheet.

Designs will vary but in essence all involve some form of heat sink to dissipate the heat away from the active components. It is the interface between the heat sink and component that calls for the use of thermal transfer compounds - without their use any air gaps that exist will act as an insulator and prevent heat escaping.

These transfer materials come in a wide variety of forms - liquid adhesives, pastes, gels, potting compounds, sheets, rolls, pads and sprays. They also utilise an equally large array of chemistries.

The choice of material will be driven by a combination of factors including:

• Thermal requirements
• Manufacturing processes
• Environmental operating conditions
• Need for additional functionality

Visit our Thermally Conductive Encapsulants page.