Advantages and Disadvantages of Three Types of Encapsulating Adhesives: Silicone, Epoxy Resin, and PU(1)

What is encapsulating adhesive?

Encapsulating adhesive is a material used to fill and seal electronic components and circuits using equipment or manual methods. It is then cured at room temperature or heated to form a high-performance thermosetting polymer insulating material, which serves the purpose of bonding, sealing, encapsulating, and coating for protection.

What are the main functions of encapsulation?

The main function of encapsulation is:

1) to enhance the integrity of electronic components and improve resistance to external impact and vibration;

2) to improve the insulation between internal components and circuits, which is beneficial for the miniaturization and lightweighting of devices;

3) to prevent direct exposure of components and circuits and improve the device‘s waterproof, dustproof, and moisture-resistant performance;

4) to conduct heat and dissipate heat.

Advantages and disadvantages of the 3 encapsulating adhesives?

1) Epoxy encapsulating adhesive

Epoxy encapsulating adhesive is mostly rigid and becomes as hard as stone after curing, making it difficult to remove. It has excellent confidentiality function, but there are also a few soft ones. The common ones can withstand temperatures around 100℃, while the ones that are heated to cure can withstand temperatures around 150℃, and there are also those that can withstand temperatures above 300℃. They have characteristics such as fixing, insulation, waterproofing, oilproofing, dustproofing, anti-theft sealing, corrosion resistance, aging resistance, cold and heat shock resistance, etc. Some common types of epoxy encapsulating adhesive include flame-retardant, heat-conductive, low-viscosity, and high-temperature resistant types.

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

Disadvantages: Poor resistance to cold and heat changes, prone to cracking after being subjected to cold and heat shock, which allows water vapor to seep into electronic components from the cracks, poor moisture resistance. And after curing, the hardness of the gel is high and brittle, which can easily scratch electronic components. After encapsulation, it cannot be opened for repair.

Application: Epoxy encapsulating adhesive is easy to penetrate into the gaps of products and is suitable for encapsulating small to medium-sized electronic components at room temperature with no special requirements for environmental and mechanical properties, such as ignition coils for automobiles and motorcycles, LED driver power supplies, sensors, ring-type transformers, capacitors, triggers, LED waterproof lights, circuit board secrecy, insulation, and moisture (water) encapsulation.

2) Silicone Encapsulating Adhesive

After curing, organic silicone electronic encapsulating adhesive is usually soft and elastic, which can be repaired. It is commonly referred to as "soft gel" due to its poor adhesion strength. Its color can usually be adjusted to any desired color, either transparent, non-transparent, or colored. Two-component silicone encapsulating adhesive is the most common type, which includes the two types of condensation and addition. Generally, the adhesion of condensation type to the electronic components and encapsulating cavity is poor, and low molecular substances will be generated during curing, resulting in a noticeable shrinkage after curing. The addition type (also known as silicone gel) has very small shrinkage and no low molecular substances will be generated during curing, which can be quickly cured by heating.

Advantages: excellent aging resistance, good weather resistance, excellent impact resistance; excellent cold and heat resistance and thermal conductivity, can be used in a wide range of working temperatures, can maintain elasticity within the temperature range of - 60℃ to 200℃ without cracking, can be used for a long time at 250℃, the heat-curing type has a higher heat resistance, has excellent electrical performance and insulation ability, the insulation performance is better than that of epoxy resin, can withstand a voltage of more than 10,000V. After filling, it effectively improves the insulation between internal components and wiring, improves the stability of use of electronic components; has no corrosive effect on electronic components and no by-products are produced in the curing reaction; has excellent repairability, and the sealed components can be quickly and conveniently repaired and replaced; has excellent thermal conductivity and flame retardancy, effectively improving the heat dissipation ability and safety factor of electronic components; low viscosity, good fluidity, able to penetrate into small gaps and under components; can be cured at room temperature or heated, good self-foaming property, more convenient to use; small curing shrinkage, excellent waterproof performance and shock resistance.

Disadvantages: High price, poor adhesion.

Application: suitable for encapsulating various electronic components that work in harsh environments.

What are the advantages of silicone electronic encapsulating adhesive compared to other encapsulating adhesives?

Advantage 1: Provides long-term protection for sensitive circuits or electronic components, offering effective protection for electronic modules and devices, regardless of their simple or complex structure and shape.

Advantage 2: Has stable dielectric insulation properties, serving as an effective barrier against environmental pollution. After curing, it forms a soft elastic body that can eliminate stress caused by impact and vibration over a wide temperature and humidity range.

Advantage 3: Can maintain its original physical and electrical properties in various working environments, and can resist degradation caused by ozone and ultraviolet light. It has good chemical stability.

Advantage 4: Is easy to clean and remove after encapsulation, allowing for the repair of electronic components, and the re-injection of new encapsulating adhesive in the repaired area.

3) Polyurethane PU Encapsulating Adhesive

Polyurethane encapsulating adhesive, also known as PU encapsulating adhesive, solidifies into a soft and elastic material that can be repaired. It is commonly referred to as "soft glue." Its adhesion is between that of epoxy and silicone, and its heat resistance is generally no more than 100℃. After encapsulation, there are often many bubbles, and the encapsulation conditions must be in a vacuum. Its adhesion is between that of epoxy and silicone.

Advantages: Good low-temperature resistance, the best anti-shock performance among the three. It has the characteristics of low hardness, moderate strength, good flexibility, water resistance, mold resistance, transparency, excellent electrical insulation and flammability, and no corrosion to electrical components. It has good adhesion to metal materials such as steel, aluminum, copper, and tin, as well as rubber, plastic, and wooden materials.

Disadvantages: Poor high-temperature resistance, the surface of the cured adhesive is not smooth and the flexibility is poor, the anti-aging ability and resistance to ultraviolet radiation are very weak, and the adhesive body is prone to discoloration.

Application: suitable for encapsulating indoor electrical components with low heat generation, it can protect the installed and adjusted electronic components and circuits from vibration, corrosion, moisture, and dust, making it an ideal encapsulating material for electronic and electrical component moisture and corrosion protection.