Potting compounds protect electronic assemblies from moisture, vibrations, chemicals, and thermal stress. The three main material classes—epoxy, silicone, and polyurethane—differ fundamentally. This guide will help you make the right choice.
Why use electronic potting?
Unencapsulated electronics are vulnerable: moisture causes corrosion and short circuits, vibrations break solder joints, chemicals attack circuit boards, and temperature fluctuations cause material fatigue. Encapsulants eliminate these risks and extend the service life of electronic assemblies from years to decades.
A Comparison of the Three Material Classes
| property | epoxy | silicone | polyurethane |
|---|---|---|---|
| temperature range | –40 to +150 °C | –60 to +250 °C | –40 to +130 °C |
| Hardness (Shore) | D 70–85 (hard) | A 10–60 (soft–medium) | A 40–D 70 (variable) |
| repairability | Beyond repair | Removable | Conditionally removable |
| thermal conductivity | 0.2–1.5 W/mK | 0.2–2.0 W/mK | 0.2–0.8 W/mK |
| chemical resistance | Excellent | Good | Moderate |
| Stress-free | Low (shrinking) | Excellent | Good |
| Price | means | High | Low |
Epoxy Encapsulation – Maximum Protection
When to Choose Epoxy
When mechanical strength, chemical resistance, and a durable seal are top priorities. Epoxy potting compounds form a hard, impermeable shell around the electronics.
benefits
Highest chemical resistance, excellent electrical insulation (dielectric strength >20 kV/mm), good thermal conductivity when filled with fillers, low cost per unit volume.
disadvantages
Not repairable – encapsulated assemblies cannot be opened. Shrinkage during curing can cause stress on sensitive components (BGAs, quartz crystals, ceramic capacitors). Not suitable for applications involving extreme temperature fluctuations.
Typical applications
Power supply enclosures, sensor housings, LED drivers, ignition coils, high-voltage modules, outdoor electronics.
→ Our electrical casting resins
Silicone Encapsulation – Flexible and Repairable
When to Choose Silicone
When thermal shock resistance, repairability, and stress-free properties are critical. Silicone potting compounds remain elastic after curing and transfer virtually no mechanical stress to the assembly.
benefits
Wide temperature range (–60 to +250 °C), excellent thermal shock resistance, removable for repair and rework, no stress on sensitive components, biocompatible versions available.
disadvantages
Higher price, lower mechanical strength, sensitive to certain solvents (toluene, hexane), not suitable for applications requiring a hard surface.
Typical applications
Automotive control units, medical technology, aerospace, high-voltage modules, e-mobility (BMS encapsulation), power electronics with high power dissipation.
→ Our RTV-2 encapsulation silicones
Polyurethane Encapsulation – The Compromise
When to choose PU
When cost is a key factor and requirements for temperature and chemical resistance are moderate, PU offers good value for money for standard applications.
benefits
Lowest price, good elasticity, wide range of hardness levels (soft to hard), good adhesion to many substrates, repairable to a limited extent (soft formulations).
disadvantages
Sensitive to moisture during processing (bubble formation), limited temperature resistance, lower long-term stability than epoxy or silicone, not suitable for medical applications.
Typical applications
Consumer electronics, lighting, cable assemblies, sensors (for interior use), cost-sensitive high-volume production.
Decision Guide: Which Encapsulant for Which Application?
| Requirement | recommendation |
|---|---|
| Maximum temperature resistance (>200 °C) | silicone |
| Extreme temperature fluctuations (–40/+125 °C cycles) | silicone |
| Repairability / Rework required | silicone |
| Maximum chemical resistance | epoxy |
| Hard, impact-resistant surface | epoxy |
| Outdoors / UV Exposure | Epoxy or silicone |
| Medical Devices (ISO 10993) | silicone |
| Cost-sensitive / High-volume production | polyurethane |
| Automotive (AEC-Q200) | Silicone or epoxy |
Thermally conductive potting compounds
Thermally conductive potting compounds (λ = 0.8–2.0 W/mK) are required for power electronics, LED modules, and e-mobility applications. These compounds contain mineral fillers (aluminum oxide, boron nitride) that enhance thermal conductivity without compromising electrical insulation.
→ Further reading: Thermally conductive encapsulants
Processing tips
- Degassing: Vacuum degassing (2–5 min at –0.9 bar) removes air pockets. This is particularly important for epoxy and PU.
- Primer: For optimal adhesion to circuit boards and housing materials. Especially recommended for silicone potting.
- Mixing ratio: For two-component systems, adhere strictly to the specified ratio—deviations will result in incomplete curing.
- Note the pot life: The working time begins immediately after mixing. For large casting volumes: choose slow-curing formulations.
