What is PCB encapsulating adhesive ?

_ April 24, 2023_ Kate_ 0 Comments

PCB encapsulating adhesive is a composite material used to protect electronic components and circuits, which can be coated on the PCB board to provide waterproof, dustproof, shockproof, shear resistance and other functions. The following introduces you to the relevant content of PCB encapsulating adhesive.

What is PCB encapsulating adhesive

PCB encapsulating adhesive and its roles

Encapsulating adhesive is a more commonly used auxiliary material in the industrial, with good fluidity and low viscosity, which can be applied to the bonding between various electronic devices. And after curing, it will form a soft body similar to rubber, which can play a good impact resistance, and can play a role in heat resistance, moisture resistance, cold resistance in electronic devices, and can increase the service life of electronic or electrical appliances.

PCB encapsulating is to pour adhesive (polyurethane potting glue, silicone potting glue, epoxy resin ) into devices equipped with electronic components and circuits with equipment or manual methods, and next , solidify them into thermosetting polymer insulation materials with excellent performance under normal temperature or heating conditions, so as to achieve the purpose of bonding, sealing, potting and coating protection.

What’s the main role of PCB encapsulating adhesive

– Protect the mechanical properties of electronic components and circuits, such as absorbing impact forces, reducing vibrations, etc..

– Prevent the circuit from being attacked by chemicals (such as water, acids, alkalis, etc.), improve their stability and durability.

– Increase the adaptability of the circuit to temperature, especially in high temperature environment, to ensure that the normal operation of the circuit is not affected by temperature.

– Improve the insulation performance of the circuit and reduce the influence of leakage, inductance and other factors.

– Improve the EMI (Electromagnetic Interference) and RFI (Radio Frequency Interference) characteristics of the circuit.

What’s the type of PCB encapsulating adhesive

Common PCB encapsulating adhesive are Silicone, Acrylic, Ester, Polyurethane and so on. According to different applications and requirements, choose different types of encapsulants to obtain the best results.

▲ Epoxy encapsulating adhesive

Epoxy resin potting glue is mostly hard, and after curing, it is hard and difficult to remove, and it has a good seal function. The ordinary temperature resistance is about 100 °C, the temperature resistance of heating and curing is about 150 °C, and there are also temperature resistance above 300 °C. It has the characteristics of fixed, insulated, waterproof, oilproof, dustproof, anti-theft, corrosion resistance, aging resistance, cold and hot shock resistance. Common epoxy potting adhesives are: flame retardant type, thermal conductive type, low viscosity type, high temperature resistant type, etc.

▲ Silicone encapsulating adhesive

Silicone encapsulants referred to as soft glue, and the adhesion is poor. After curing, silicone electronic potting glue is mostly soft and elastic and can be repaired. Its color can generally be adjusted as needed, or transparent or non-transparent or colored. Two-compositions silicone encapsulants are the most common, including condensed and additive agents.

Generally, the condensed type has poor adhesion to components and potting cavity, and volatile low molecular substances will be produced during the curing process, and there is a significant shrinkage rate after curing; The molded (also known as silica gel) has minimal shrinkage, no volatile low molecular weight substances during the curing process, and can be heated for rapid curing.

▲ Polyurethane encapsulating adhesive

Polyurethane encapsulating adhesive, also known as PU encapsulating adhesive, after curing, mostly soft, elastic can be repaired, referred to as soft rubber, adhesion between epoxy and silicone, temperature resistance is general, generally not more than 100 °C, after potting there are more bubbles, potting conditions must be under vacuum, adhesion between epoxy and silicone.

Consideration when selecting PCB encapsulating adhesive

1) Requirements for performance after encapsulating: use temperature, hot and cold alternating conditions, internal stress of components, outdoor or indoor use, force 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, solidification time of glue after mixing, etc.;

3) Cost: The proportion of potting materials varies greatly, we must look at the actual cost after potting, rather than simply looking at the selling price of the material.

Consideration when using electronic PCB encapsulating adhesive

● Select the appropriate type and formula of PCB encapsulating adhesive, and mix it according to the actual situation.

● Before mixing the glue, make sure the tools and containers are clean to avoid impurities contaminating the PCB encapsulating adhesive.

● Before pouring the PCB encapsulating adhesive, please clean the area to be potted and ensure that the surface is dry and free of impurities such as oil and dust.

● After pouring the PCB encapsulating adhesive, the air bubbles should be removed in time with a vibrating plate or other tools to ensure the quality of potting.

● If the mixed encapsulating adhesive is not used immediately, store it in an airtight container to avoid solidifying in contact with air.

● Depending on the nature and requirements of the glue, the curing process is carried out at the correct temperature.

● Please pay attention to personal protection during potting such as wearing gloves, masks, etc.

● Do not contact the skin and eyes directly when using, if accidentally contacted, should be washed immediately.

● Please store in a dry, cool, dark place, away from fire and flammable materials to avoid safety accidents.

Reliability testing of PCB encapsulating adhesive

Reliability testing of PCB encapsulating adhesive needs to be selected according to the specific product and application area. Here are some common reliability test conditions:

● Heat aging test: the PCB encapsulating adhesive is placed in a high temperature environment to detect its aging at different temperatures and times.

● Life test: simulate the vibration, shock, humid heat and other environmental conditions during actual use, and test its service life and performance stability.

● Salt spray test: simulates humid environments such as the ocean to test their corrosion resistance and durability.

● High and low temperature cycle test: simulate the temperature change in the actual working environment by alternating heating and cooling, and test its adaptability and stability to temperature change.

● Environmental pollution test: the PCB encapsulating adhesive is exposed to air pollution to test its anti-pollution ability and weather resistance.

● Insulation resistance test: test the insulation resistance and dielectric strength of PCB encapsulating adhesive to evaluate their insulation performance.

● Tensile, compression and other mechanical property tests: test the mechanical strength, hardness and other properties of encapsulating adhesive to evaluate their mechanical reliability.

Conclusion

PCB encapsulating adhesive plays an important role in the electronic component manufacturing industry. It can improve the stability and reliability of the PCB, and also protect the electronic components and circuits from the interference of the external environment. In order to make electronic components play a better role, we should choose the appropriate PCB encapsulating adhesive according to specific requirements, and pay attention to the details and points in the construction process.