How to Select a Potting Silicone for Power Electronics

Start from the thermal path, not the filler

Thermal management exists because heat shortens component life. Reference figures used across our thermal material documentation note that electronic component reliability falls by roughly 10% for every 2°C rise in temperature, and that service life at 50°C can be as low as one sixth of the life at 25°C.

That is why potting is treated as part of the thermal path rather than only as protection. The material has to occupy the air gaps between component surfaces and the heat sink, and it has to do so without trapping voids.

• Silicone and epoxy thermally conductive systems in the range cover thermal conductivity from about 0.4 to 6.0 W/m·K.
• Potting compounds are formulated for low viscosity and good leveling so they fill complex housings.
• Cured systems are designed to form a deep-cured elastomer rather than remain a paste.

Flow before cure decides whether the process works

Two-component 1:1 systems are supplied at around 2000 mPa·s for the standard potting grades, which allows the material to flow around inserts and windings before cure.

When the housing is large or the clearance is tight, low-viscosity flow is the deciding property. When the gap is a controlled bond line, a gap filler or adhesive is often the better shape of product.

• Thermally conductive potting compound GMX-8152/11 and GMX-8152/15N(3:1) are the stated recommendations for high-voltage distribution boxes and on-board chargers.
• Thermally conductive potting compound GMX-8160 and GMX-8160V are recommended where motors and electric motors have high heat dissipation requirements.
• Thermally conductive potting compound GMX-8152/8760Z and the GMX-8152/08M series are stated for potting of power components.

Hardness and stress after cure

Hardness decides how the cured material loads the assembly. A potting compound cures into an elastomer; a gel stays soft and compressible. Where the component is fragile or thermally cycled hard, the softer option reduces stress on solder joints and windings.

Gels are described as low stress and compressible, with good electrical insulation, good high and low temperature stability, and excellent damping and shock absorption.

• Thermally conductive gel GMX-TG-3220 and GMX-TG-3222 are 1:1 two-component grades with a stated thermal conductivity of 2.3.
• Thermally conductive gel GMX-TG-6 and GMX-TG-3230 are stated for communication equipment and RF units.
• Thermally conductive adhesive DR-5212 is stated for gap filling of lithium battery modules.

Protection requirements beyond heat

Potting compounds in this range are described as combining thermal conductivity with flame retardancy, which matters for high-voltage assemblies. Electrical insulation and long-term stability at high and low temperature are part of the same specification.

For transparent devices the requirement changes again: transparent electronic potting grades are used where the cured material must be seen through.

Confirm before you specify

The final choice depends on the housing geometry, the dispense equipment, the cure schedule available in production and the electrical clearance required. Send the drawing and the process window and the compound can be matched to the assembly rather than to a datasheet alone.