When a power supply or transformer module needs potting, a two-part thermal conductive silicone encapsulant replaces the air between components with a solid silicone insulation layer and carries heat to the metal housing. The three figures engineers and buyers usually check are on the product page: dielectric strength of 10 kV/mm (ASTM D149), volume resistivity of 1 × 10^13 Ω·cm (ASTM D257) and a UL 94 V-0 flame rating. From there, estimate the average field from the working voltage and the thinner potting sections, then confirm with a withstand test on the real assembly.

Swap the air between components for solid insulation

The gain starts in the gaps. A power board has irregular spaces around transformer pins, capacitors and heat sinks, and a liquid encapsulant flows into them before curing into a solid insulating layer. Engineers searching for a high breakdown voltage dielectric paste are usually looking for exactly this: a compound that cures in place around the parts. The product page describes this addition-cure silicone as flexible and elastic, able to cover uneven surfaces and conduct heat from the PCB or discrete components to the metal housing.

Four reasons it suits high-voltage modules

Dielectric strength you can compare

Material choices can be compared under one test method. The product page lists a dielectric strength of 10 kV/mm tested to ASTM D149.

High resistivity blocks leakage paths

The cured layer conducts very little, so leakage channels between neighbouring conductors are hard to form. The H-GF-GY product page lists volume resistivity of 1 × 10^13 Ω·cm (ASTM D257) and a dielectric constant of 5.0 at 1 MHz (ASTM D150), a useful input when you assess capacitive coupling.

Insulation and heat transfer in one layer

High-voltage parts are often the hot parts too, and one material handles both jobs. Thermal conductivity comes in two grades, 1.0 and 3.0 W/m·K (ISO 22007-2), and heat moves through the potting to the housing.

Flame rating and reworkability on record

Power products need flame retardancy, and rework cost matters as well. The product page lists UL 94 V-0, self-adhesion with no primer required, and a cured compound that can be pried apart for component repair.

Where it fits

• Power supplies and high-power LED lamps: component gaps on the board are filled, and heat passes through the potting to the housing.
• Transformers and coils: once the space around the windings is filled, insulation and fixing are done together.
• Sensors: small modules gain an extra layer of water and insulation protection.

The dielectric strength formula: how thick is enough

Dielectric strength is defined as E_bd = V_bd / d, the breakdown voltage of a specimen divided by its thickness (source: Lehigh University lecture on dielectric strength).

• E_bd: dielectric strength, kV/mm
• V_bd: voltage at which the specimen breaks down, kV
• d: insulation thickness between the electrodes, mm

For design, use it in reverse. Fix the working voltage of the module, find where the potting between conductors is thinnest, estimate the average field and keep a wide margin below the 10 kV/mm material value. The relation only describes a parallel-plate model with a roughly uniform field. Dielectric strength shifts with thickness, temperature, frequency and waveform, so doubling the thickness does not guarantee double the breakdown voltage. Solder tips concentrate the field and trapped bubbles reduce the effective thickness locally. ASTM D149 itself notes that its results can seldom be used directly for an actual application, so treat the formula as an engineering model and not as a working-voltage rating for the product.

What to send with your inquiry

The potting process affects insulation quality too. The product page asks you to stir Parts A and B separately, then mix them 1:1 by weight within a 3% error. Working time is about 40 to 60 minutes at 25°C, and cure takes 20 minutes at 80°C or about 8 hours at room temperature. The page recommends vacuum degassing when very high thermal conductivity is needed; high-voltage modules can add degassing to the evaluation to keep bubbles away from conductors.

When you request a sample or a specification review, include the working voltage and waveform, the potting thickness between conductors, the housing material and the withstand test you need to pass, so the right thermal grade can be assessed. For dispensing thermally conductive materials step by step, see the two-part encapsulant mixing and potting guide, and for how insulating pads are rated, read our review of dielectric strength in thermal pads.

Conclusion

A high-voltage module needs insulation without voids, and it cannot trap heat. The thermal conductive silicone encapsulant fills component gaps with solid silicone, and its dielectric strength, volume resistivity and flame rating are all published on the product page; actual withstand voltage is confirmed by testing the assembly. Contact Lixing Composite Materials Co., Ltd. to request samples and specifications.

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