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.

Gap Fillers
These Thermally Conductive 2-Part, 1:1 Paste materials cure to form a very soft rubber. They are designed to be used as flexible Gap Fillers in electronic assemblies. The cured material is not self-bonding but remains flexible, allowing for a good interface between components or PCB’s and heat sinks or enclosures. They are easily applied and provide a very efficient path for heat dissipation between uneven surfaces, while removing air gaps that would cause heat to build up in the component.

These Gap Fillers are used in applications with wide tolerances or differences in the gap between the component or PCB and the heat sink. In some areas, the gap may be close to zero, in other areas it may be several millimetres. If a hard interface material is used, the pressure exerted when trying to eliminate any air gaps could be very damaging to either the PCB or delicate components.

The liquid dispensable Gap Filler can be applied to very specific areas and at varying thicknesses, thus offering commercial and technical advantages.

Non-setting compounds
Silicone thermal transfer compounds are non-setting in which they do not cure, have no adhesion and retain their physical properties, similar to that of grease. The main reason to choose a compound rather than adhesive is the ability to easily rework the component. Under typical circumstances, the component would be held in place with some form of mechanical fastening systems and the compound applied to simply improve heat dissipation. These silicone compounds are work stable and will withstand reasonably high temperatures.

For more information, download our CHT SILCOTHERM product brochure.

Finding the right silicone for your application is not limited to CHT’s product portfolio. Our technical team will partner with you to either modify specifications in a current product or custom formulate a new one to meet your exact requirements

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About The CHT Group
The CHT Group, a medium-sized global player and “hidden champion” for speciality chemistry, is active worldwide in development, production and sales. The CHT Group’s headquarters is located in Tübingen, Germany.
CHT products improve the quality, the functionality and the performance of textiles, building materials, colours, coatings, papers and agrochemicals as well as cleaning and care products for the field of consumer goods industry.
By bundling the strengths of the entire group, innovative products, applications or processes are constantly in development. Highly qualified specialists work in top equipped laboratories for development, analysis and application engineering in order to develop ideas and solutions that meet with the most modern of requirements.
In 2023 the group had almost 2,500 employees in 28 companies contributing to the company's success.
The CHT Group operates very close to its customers and markets. Together with its own representatives, the company provides products and services for customers in over 120 countries on all continents.