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Advantages and disadvantages of three types of potting adhesives: silicone, epoxy resin and polyurethane PU


1) Epoxy resin potting adhesive

Epoxy resin potting glue is mostly hard. After curing, it is almost as hard as a stone, and it is difficult to remove. It has a good confidentiality function, but a small part is soft. The ordinary temperature resistance is about 100℃, the temperature resistance of heating curing is about 150℃, and there is also temperature resistance above 300℃. It has the characteristics of fixation, insulation, waterproof, oil-proof, dust-proof, anti-theft, corrosion resistance, aging resistance, and thermal shock resistance. Common epoxy potting compounds are flame retardant type, thermal conductivity type, low viscosity type, high-temperature resistant type, etc.

Advantages: good adhesion to hard materials, excellent high-temperature resistance, and electrical insulation, simple operation, very stable before and after curing, excellent adhesion to various metal substrates and porous substrates.

Disadvantages: The ability to resist cold and heat changes are weak, and cracks are prone to occur after being hit by cold and heat, resulting in water vapor infiltrating into electronic components from the cracks, and poor moisture resistance. After curing, the colloidal hardness is high and brittle, which is easy to strain electronic components, cannot be opened after potting, and has poor repairability.

Scope of application: Epoxy resin potting glue easily penetrates the gap of the product, is suitable for potting small and medium-sized electronic components under normal temperature conditions, and has no special requirements for environmental mechanical properties, such as automobile and motorcycle igniters, LED drive power, Sensors, toroidal transformers, capacitors, triggers, LED waterproof lights, confidentiality, insulation, moisture-proof (water) potting of circuit boards.


2) Silicone potting adhesives

Silicone electronic potting glue is mostly soft and elastic after curing, which can be repaired, referred to as soft glue, and has poor adhesion. Its color can generally be adjusted arbitrarily according to needs, or transparent or non-transparent or colored. Two-component silicone encapsulant is the most common, and this type of adhesive includes two types of condensation type and addition agent. Generally, the condensation type has poor adhesion to the components and the potting cavity, and volatile low-molecular-weight substances will be produced during the curing process, and there will be obvious shrinkage after curing; the addition type (also known as silicone gel) has a very high shrinkage rate. Small, volatile low-molecular-weight substances will not be produced during the curing process, and it can be heated and cured quickly.


Advantages: strong anti-aging ability, good weather resistance, excellent impact resistance; excellent resistance to cold and heat changes and thermal conductivity, can be used in a wide range of working temperature, can be maintained in the temperature range of -60 ℃ ~ 200 ℃ Elasticity, no cracking, can be used for a long time at 250 ℃, heating curing type has higher temperature resistance, excellent electrical properties and insulation ability, insulation performance is better than epoxy resin, and can withstand voltage above 10000V. After potting, it can effectively improve the insulation between internal components and circuits, and improve the stability of electronic components; it has no corrosiveness to electronic components and does not produce any by-products in the curing reaction; it has excellent repair ability, which can be quickly and conveniently Take out the sealed components for repair and replacement; have excellent thermal conductivity and flame retardant ability, effectively improve the heat dissipation capacity and safety factor of electronic components; low viscosity, good fluidity, and can penetrate into small gaps and Below the components; it can be cured at room temperature or heated, with good self-discharging and more convenient use; small curing shrinkage, with excellent waterproof performance and shock resistance.

Disadvantages: high price, poor adhesion.

Scope of application: suitable for potting various electronic components that work in harsh environments.


3) Polyurethane PU potting adhesive

Polyurethane potting glue is also called PU potting glue. After curing, it is mostly soft and elastic and can be repaired. It is referred to as soft glue. The adhesiveness is between epoxy and silicone. There are many bubbles after potting, and the potting conditions must be under a vacuum, and the adhesiveness is between epoxy and silicone.

Advantages: good low-temperature resistance, shock resistance is the best among the three. It has the characteristics of low hardness, moderate strength, good elasticity, water resistance, mildew resistance, shock resistance, and transparency. It has excellent electrical insulation and flame retardancy and has no corrosion to electrical components. And rubber, plastic, wood, and other materials have good adhesion.

Disadvantages: poor high-temperature resistance, uneven surface and poor toughness of the colloid after curing, weak anti-aging ability and UV resistance, and the colloid is easy to change color.

Scope of application: It is suitable for potting and sealing indoor electrical components with low calorific value so that the installed and debugged electronic components and circuits will not be affected by vibration, corrosion, moisture, and dust. Ideal potting material.


4) What should be considered when selecting potting materials?

1) Requirements for performance after potting: use temperature, alternating hot and cold conditions, the internal stress of components, outdoor use or indoor use, stress conditions, whether flame retardant and thermal conductivity are required, color requirements, etc.;

2) Potting process: manual or automatic, room temperature or heating, complete curing time, curing time of glue after mixing, etc.;

3) Cost: The proportion of potting materials varies greatly. We must look at the actual cost after potting, not simply the price of the material.

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