Silicone potting compounds is an environmentally friendly material for filling or encapsulating electronic assembly, It protects the components from shock and vibration, corrosion, and contaminants such as dust.
Silicone potting compounds feature a unique combination of flexibility, high and low temperature resistance while maintaining constant mechanical properties over a wide range of temperature, making them suitable for potting sensitive electronics. silicone potting compounds are the best choice for high-temperature applications and electronics exposed to thermal cycling.
Principle of Potting
Silicones potting compounds start out as low viscosity self-leveling liquids that quickly fill gaps in and around components. In essence, it's like creating a suitable "pot" to put electronics in, then filling that pot with special curable liquids silicones that have whatever thermal, insulation, adhesive and structural properties as are required for a potting project.
Silicones potting compounds are designed to protect and insulate printed circuit boards (PCBs) and electronic components from the threats of harsh and challenging environments. Potting does not only protect against moisture and exposure but also gives protection against the effects of mechanical shock and vibration, supporting and cushioning delicate or fragile components such as the brittle ferrites used in transformer cores. By encapsulating components or potting the entire device, silicones potting compounds can form a complete barrier against such environments offering superior performance under extreme conditions.
Features
The advantages of silicone potting materials are:
- Wide operating temperature range, Stays soft at extremes of temperature (-50°C up to 200°C).
- It has small shrinkage during curing and has excellent waterproof and moisture resistance.
- Low viscosity: It has good fluidity and can penetrate into small voids and under the components, no air bubbles.
- Excellent weathering, anti-aging properties, UV and ozone resistance
- Fire and flame retardant, UL94 V-0 grades available
- Good thermal conductivity, Good heat dissipation performance, it can effectively reduce the component temperature.
- silicone rubber has good insulation properties.
- Good adhesion, Bonds to a wide variety of substrates.
- Safest for the environment (no by-products from the curing process)
- Clear, opaque and color versions available.
The disadvantages are:
More expensive compared with Polyurethane or epoxy. In addition, certain types of sealants require primers for adhesion, which epoxy and urethane don’t require. But remember, this can also be a benefit in many cases. Lighter adhesion lets you repair your parts in a way that other compounds prohibit.
Applications
Long-term effective protection of sensitive circuits and electronic components plays an increasingly important role in today’s sophisticated and demanding electronic applications. The silicone potting material has stable dielectric insulation and is an effective guarantee for preventing environmental pollution. At the same time, it can eliminate the stress generated by shock and vibration in a large temperature and humidity range.
Silicones potting compounds is widely used for potting protection of high-power electronic components, module power supplies, circuit boards and LEDs。The can also be used for the casting of sensitive electronic components, potting telecommunications equipment, thermal cut-out switches, potting ballasts, pumps, surge suppressors, connectors, switches, relays, coils, transformers, power supplies, resistors, solenoids, proximity switches, transistors, sensors, power line filters, timers, etc.
Due to their elasticity and low modulus, silicones are also ideal materials for potting delicate surface mount devices to mitigate any damages due to thermal expansion and contraction. With excellent resistance to moisture, weathering and UV silicones are suited for applications like outdoor lighting, transportation and aerospace.
Types
RTV-1 Silicone Potting Compounds
RTV-1 silicone potting compounds are also called ready-to-use silicone potting compounds, No mixing required --these potting compounds come ready to apply. Usually use them to encase electronic assemblies for protection from dust, moisture, mechanical shock, and vibration.
RTV-2 Silicone Potting Compounds
RTV-2 silicone potting compounds are two-component, low viscosity potting compound that cures at room temperature to a soft pliable rubber. They are divided into condensation type and addition type.
Condensation silicone potting can achieve primerless adhesion to many substrates, including metals, plastics and ceramics. The excellent electrical properties make it a candidate material for both high and low voltage electrical assemblies. Cushions against mechanical shock and vibration. Usually cures at room temperature without exothermic or endothermic. During the curing process, a small amount of low molecular weight (alcohol) is released.
The product characteristics of the addition type silicone potting compounds: insulation, moisture resistance, excellent electrical properties, excellent heat and cold resistance, and earthquake resistance. Curing at room temperature, or heat curing. No low molecular release during curing. When curing, the inside and outside are cured at the same time, which can be deeply cured.
Directions for use
Circuit board cleaning: use a solvent to remove any dust and soldering residue from the circuit board surface for a better adhesion effect. Note: after cleaning and shading processes, the circuit board should be dried before coating. The drying temperature and time are determined by the maximum allowable temperature of the circuit board.
Mixing: shake part A and part B components vigorously in their own containers.
Stir: Mix thoroughly and evenly by weight in the proportions specified in the instructions.
Air bubble removal (Optional ): Most of them do not require bubble removal. If necessary, vacuum the mixed potting compound in a vacuum environment for 1 to 3 minutes to remove bubbles.
Potting: immediately apply the mixed potting compounds to the substrates. The later thickened product results in a poor fluidity, so doing so immediately is extremely important.
Cure: RTV silicone potting compounds will cure at room temperature.
Health and Safety
Silicone potting compounds are safer than other potting compounds (Epoxy potting compounds) , making it a more ideal material for engineers who want to avoid compliance or labor issues. In environments where health and safety are a huge concern, having the most worker-friendly product possible is critical. That’s why silicone is so frequently used in medical devices.
