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Thermally Conductive Sealants & Adhesives

Thermally conductive adhesives both adhere to and efficiently conduct thermal energy from a heat source. They are often used in electronics, for example, to bond a heat sink to a processor to move the heat from the processor to the heat sink. Thermally conductive silicones are synthetic resins, which can be made from a number of elastomers, and are augmented with metallic or inorganic fillers such as an aluminum oxide or aluminum nitride. Thermally conductive RTV (room temperature vulcanizing) epoxies can be found in one or two parts, as well as with various cure systems.

Common applications for thermal conductive adhesives include heat sink bonding, potting and/or encapsulating sensors, adhering power semiconductors and more. In addition to adhesives, non-hardening gels are also available and are ideal for specialty assembly heat transfers. Thermal conductive silicone works best with a thin layer.

The miniaturized electronics in use today are powerful and generate more heat. Electronic devices need to be kept cool to reduce energy consumption, avoid damage to surrounding components, and extend their life.

Moreover, modern equipment and appliance incorporate electronics and microprocessors that drive up performance but are also more sensitivity to reliability and power quality issues. Good thermal management has become crucial for compact electronics, and thermally conductive silicone adhesives, a type of thermal interface materials, are a part of the solution.

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Exonic Thermally Conductive Adhesive - Electronic Components Exonic Thermally Conductive Adhesive

Our thermally conductive silicone RTV transfer adhesive rubber developed for heat sink applications.

Starting at: $29.01
Exonic Thermal Joint Sealant Exonic Thermal Joint Sealant

A high temperature thermal joint compound developed to fill the gaps between heat sinks and substrates.

Starting at: $30.24
EX3-118 - Thermally Conductive Deep Section Paste Silicone Adhesive EX3-118 - Thermally Conductive Deep Section Paste Silicone Adhesive

Exonic Polymers Thermally Conductive Deep Section paste is 2-part, Platinum cure, adhesive sealant silicone RTV that offers great thermal conductivity. When cured, the elastomer resists weathering, ozone, moisture, UV and high temperatures.

Starting at: $30.50
EX3-119 - Fast Cure Thermally Conductive Deep Section Paste Silicone Adhesive EX3-119 - Fast Cure Thermally Conductive Deep Section Paste Silicone Adhesive

Exonic Polymers Thermally Conductive Deep Section paste is 2-part, Platinum cure, adhesive sealant silicone RTV that offers great thermal conductivity. When cured, the elastomer resists weathering, ozone, moisture, UV and high temperatures.

Starting at: $33.57
Exonic Thermally Conductive Vibration Dampening Liquid Silicone Gap Filler Thermally Conductive Vibration-Dampening Liquid Silicone Gap Filler, 1.0 W/mK

A performance thermally conductive liquid gap filling material. It is formulated to develop a very soft, form in place elastomer, ideal for coupling hot PC board components to heat sinks. It is supplied as a two part, 1:1 mixed system that will cure at room temperature and can be accelerated with the addition of heat. This product is superior to cured thermal pad material because using a paste approach offers infinite thickness variations with little or no stress to sensitive components during assembly.

Starting at: $36.69
EX3-120 - Extremely Fast Cure Thermally Conductive Deep Section Paste Silicone Adhesive EX3-120 - Extremely Fast Cure Thermally Conductive Deep Section Paste Silicone Adhesive

Exonic Polymers Thermally Conductive Deep Section paste is 2-part, Platinum cure, adhesive sealant silicone RTV that offers great thermal conductivity. When cured, the elastomer resists weathering, ozone, moisture, UV and high temperatures.

Starting at: $36.93
Exonic 2 W/mK Thermally Conductive Vibration Dampening Liquid Silicone Gap Filler Exonic 2 W/mK Thermally Conductive Vibration Dampening Liquid Silicone Gap Filler

A performance thermally conductive liquid gap filling material. It is formulated to develop a very soft, form in place elastomer, ideal for coupling hot PC board components to heat sinks. It is supplied as a two part, 1:1 mixed system that will cure at room temperature and can be accelerated with the addition of heat. This product is superior to cured thermal pad material because using a paste approach offers infinite thickness variations with little or no stress to sensitive components during assembly.

Starting at: $39.23
Exonic Self-Leveling 2.0 W/m-K Thermally Conductive Liquid Silicone Gap Filler Exonic Self-Leveling 2.0 W/m-K Thermally Conductive Liquid Silicone Gap Filler

A performance thermally conductive liquid gap filling material. It is formulated to develop as a low viscosity liquid that allows the product to self-level in the application. In addition it develops a very soft, form in place elastomer, ideal for coupling hot PC board components to heat sinks. It is supplied as a two part, 1:1 mixed system that will cure at room temperature and can be accelerated with the addition of heat. This product is superior to cured thermal pad material because using a paste approach offers infinite thickness variations with little or no stress to sensitive components during assembly.

Starting at: $41.54
Exonic 2.2 W/mK Thermally Conductive Silicone Gap Filler Exonic 2.2 W/mK Thermally Conductive Silicone Gap Filler

A performance thermally conductive liquid gap filling material. It is formulated to develop a very soft, form in place elastomer, ideal for coupling hot PC board components to heat sinks. It is supplied as a two part, 1:1 mixed system that will cure at room temperature and can be accelerated with the addition of heat. This product is superior to cured thermal pad material because using a paste approach offers infinite thickness variations with little or no stress to sensitive components during assembly.

Starting at: $41.63
Thermally Conductive Silicone Adhesive Sealant - Momentive TSE 3941 Offset Exonic Thermally Conductive Silicone Adhesive Sealant - Momentive 3941

Our thermally conductive silicone RTV adhesive rubber developed for heat sink applications.

Starting at: $77.12
Exonic Rubberized Thermally Conductive Silicone Coating Exonic Rubberized Thermally Conductive Silicone Coating

A fast cure RTV rubberized silicone developed for thermally conductive applications. This thermally conductive silicone rubber adheres well to metals and composite substrates.

Starting at: $302.58
   
 

Thermal conductivity and thermal interface materials – A quick overview

Thermal interface materials act as an essential part of an efficient thermal management system by transferring heat between two or more solid surfaces. Thermal adhesives, a category of thermal interface materials, are a specialized type of glue that handle heat transfer while holding components together. They are available as curing fluids, tapes or sheets.

Thermal conductivity is a material’s intrinsic ability to transfer or conduct heat. It is also defined as the amount of heat per unit time per unit area that can be conducted through a plate of unit thickness of a given material, with the faces of the plate differing by one unit of temperature.

As molecular conductivity occurs due to molecular agitation and collision, it does not result in the movement of the solid. Heat moves from an area of high temperature and high molecular energy to an area of lower temperature and lower molecular energy. This process continues until thermal equilibrium is reached.

A material’s thermal conductivity depends on a number of factors, including the properties of the material, temperature gradient, and the path length followed by the heat. Air has a low conductivity 0.024 W/mK at 0°C while copper is a highly conductive metal (385 W/mK).

The temperature of a material also affects thermal conductivity. At higher temperatures, molecules move more quickly, and heat is transferred through the material at a higher rate. It implies that an increase or decrease in temperature can change the thermal conductivity of the material quite significantly.

An understanding of the effect of temperature on thermal conduction is important to ensure that products retain their function and performance when they undergo thermal stress. This is especially important when working with electronics and developing heat- or fire-protection materials.

The structure of the material is also a factor when it comes to thermal conductivity. The thermal conductivity values of some materials differ depending on the direction of heat travel. Based on how heat transfer occurs, materials can be divided into gases, metallic solids and non-metallic solids.

The thermal conductivity of gases is lower than that of solids. As the molecules in non-metallic solids are tightly packed, they have a higher thermal conductivity than gases. But thermal conductivities can vary across different non-metallic solids.

Metals have the highest thermal conductivities of all materials except graphene. They have both thermal and electric conductivity, which correlate positively, that is, materials with higher electrical conductivity/low electrical resistance exhibit higher thermal conductivity.

The thermal conductivity of materials determines their application. Materials with low thermal conductivities do not allow heat to pass easily through them, and are therefore ideal for insulating homes and commercial establishments. Those with high thermal conductivity are utilized where heat must be moved quickly and efficiently from one area to another, such as in cooling systems of electronic devices.

Why use thermal silicone?

Silicones are a diverse family of high-performing materials. They are extremely environmentally friendly, solvent free, non-volatile and do not contribute to ecosystem degradation. Cured silicone rubbers are not biodegradable or affected by weathering, ozone and exposure to UV. Cured silicone rubber is resistant to extreme temperature changes (–60°C to +250°C). It also offers protection against moisture, and withstands shocks, vibrations and chemical attacks.

At low temperatures (-75°C), they remain highly elastic, besides offering excellent temperature stability when exposed continuously to higher temperatures (up to 200°C), and up to 300°C for shorter durations. Silicone’s properties remain intact during temperature fluctuations.

A wide range of products can be made from different formulations of cured silicone elastomers. These include adhesive sealants, micro thin coatings, soft cured gels and rubbers of varying hardness. As bonds made with silicones can be acted upon by small mechanical loads, their primary use is in the form of sealants.

A humidity of 5%-95% is required to cure single component silicone adhesives. That apart, a temperature of between (5°C and 40°C) is needed for the curing process. The adhesive film’s thickness will determine how long complete curing takes, and can run into several days. For thickness of only a few millimeters, the adhesive cures fully in 24 hours.

During battery design, engineers may concern themselves with two main tasks – installing each battery cells and the other is evacuating the heat, also known as thermal conductivity. Ensuring thermal conductivity involves integrating a cooling system with cooling fluids, usually under the battery modules, with the goal of reducing heat generated by the battery cells. Thermally conductive materials are used to facilitate conduction between the cell and cooling plate. The cavities or roughness of the surface are ‘filed’ to avoid air void. As these materials have high thermal conductivity, the heat moves down directly to the colling system for removal.

So, it follows that cells should adhere effectively to the cooling plate, which means the thermally conductive material should maintain bonding for a long time. For reliable binding over the entire battery life, the right selection of thermally conductive materials is necessary.

When high thermal conductivity is required, silicone adhesives are a popular option. Their thermal conductivity can be improved by adding thermally conductive fillers to the formulation while also maintaining bonding performance. Silicones can be purpose-designed to offer the right level of adhesion and safety.

The most sensitive circuits and their components made use of thermal silicone sealants. Thermally conductive silicone is essential to dissipating heat away from heat-generating components and the surrounding equipment. The adhesive ensures that the component functions as expected even if the appliance heats up. Sealants also assist in the transfer of the device heat to heat sink.

Silicone adhesives are a sought-after choice for their ability to remain flexible across a very wide range of temperatures and operating conditions. They are also resistant to water and a variety of chemicals. They find their utility in harsh environments, bonding, sealing and protecting modern miniaturized electronics effectively.

Types of thermally conductive silicones

Silicone potting compounds are useful for heat generating circuits that require potting or encapsulation in a heatsink enclosure. This provides both heat dissipation and environmental protection.

Silicone thermal gap filler pastes are an alternative to prefabricated thermal pads. They offer better thermal dissipation compared to rigid pads. As they can be dispended by automated units, they are used in sectors that require a high production throughput and lower mechanical pressure on components. Silicone thermal gap filler pads can be cut to size and applied by hand. The thickness of the gap pad contributes to higher thermal resistance in comparison with thermal pastes.

Thermal adhesives sold as fluids can have different mechanical and adhesive properties once they are cured. Some may peel away easily; others provide moderate adhesive, while some also provide permanent adhesion. They may have a rubbery soft texture upon curing or an inflexible state.

How to choose the right thermal interface material – Important points

- The thermal resistance between joining parts depending on

(a) thermal conductivity of the thermal interface material

(b) bond line thickness, the amount of the material used between the joining items

(c) contact resistance between the different types of materials at the interfaces that make contact with one another.

- To improve heat transfer, the following options are available:

· increasing thermal conductivity of the thermal interface material

· reducing the bond line thickness between the electronic component and heat sink

· reducing contact resistance by using liquid-dispensed thermal interface materials

· increasing the mounting pressure for solid thermal interface materials.

You can use highly thermally conductive RTVs as a default. RTV silicone (room-temperature-vulcanizing silicone) is a type of silicone rubber that cures at room temperature, forming a flexible rubber. It can be an adhesive sealant, encapsulating potting compound or molding rubber. RTV silicone is made from a component system comprising a base and a curative, and first involves mixing rubber with a curing agent. Compounds containing tin or platinum are commonly used as a catalyst during preparation.

Benefits of our thermally conductive silicone sealants and adhesives

· Fast cure and good adhesion

· High thermal conductivity

· Low thermal resistance

· Wide operating temperature range

· Compatible with high-temperature lead-free processing

· Minimal ionic impurities & excellent dielectric properties

· UV exposure, ozone and weathering have no impact on silicone.

Applications

Component bonding

Gasket fabrication

PC board heat sink

Electronic component heat transfer

Adhesive sealing of components

Part fixturing with heat dissipation capability

Power unit adhesive