Thermal Gel or Thermally Conductive Potting Compound?

What each material class is for

The classification used in the thermal management documentation separates the range into thermally conductive potting compound, thermal grease, thermally conductive adhesive and thermally conductive gel. Each entry carries a different set of stated characteristics.

• Thermally conductive potting compound: low viscosity, excellent leveling; can be deeply cured into an elastomer; good thermal conductivity and flame retardancy.
• Thermal grease: paste, non-flowing, non-curing; excellent thermal conductivity and electrical insulation; good high and low temperature stability; low oil separation and low volatility.
• Thermally conductive adhesive: reliable adhesion after curing; excellent thermal conductivity and electrical insulation.
• Thermally conductive gel: low stress, compressible; good electrical insulation; good high and low temperature stability; excellent damping and shock absorption.

Gap filling versus encapsulation

A gel is the right answer when the assembly needs a compliant thermal path between two surfaces that move relative to each other, or when the component cannot tolerate a rigid encapsulant. It is stated for network servers, communication equipment and RF units, drones, lithium battery modules, solid-state storage, graphics cards and processor chips.

A potting compound is the right answer when the housing has to be filled and the device has to be mechanically and environmentally protected as well as cooled. It is stated for high-voltage distribution boxes, motors, on-board chargers, powertrain control units and power components.

Do not overlook the non-curing option

Thermal grease is non-curing by design. It stays a paste and is used as an interface material rather than a structural one, with low oil separation and low volatility as stated characteristics.

It is stated for TFT-LCD, PDP and OLED flat panel displays, network servers, transistors and power amplifiers, solid-state storage, graphics cards and processor chips.

• Thermal grease GD-6941, GD-6941-20 and GD-6941-30 are the stated grades for servers and flat panel displays.
• Thermal grease DR-5312 and DR-5360 are stated for solid-state storage, graphics cards and processor chips.
• Thermally conductive adhesive GD-480, GD-480-20, GDA-8450 and GDA-8455 are stated for power components and inverters.

A practical sequence

First decide whether the material must hold the assembly together or merely bridge a gap. Then decide whether it must cure. Finally check the conductivity, hardness and flame requirement against the housing and the electrical clearance.

If the answer is a soft interface that stays in place, look at the gels. If the answer is a filled housing that must survive the environment, look at the potting compounds.