How to choose PCB circuit board sealant

           At present, there are mainly three kinds of PCB board sealants, namely polyurethane potting glue, epoxy potting glue and silicone potting glue.

          The first is polyurethane packaging

          Temperature requirements, no more than 100 degrees Celsius, more bubbles after potting, potting conditions under vacuum, adhesion between epoxy and silica gel.

          Advantages: excellent low temperature and good impact resistance.

Disadvantages: Poor temperature resistance. After curing, the gel surface is not smooth and the toughness is poor. The anti-aging ability and anti-ultraviolet ability are weak, and the colloid is easily discolored.

Scope of application: Suitable for potting and sealing of low-heat indoor electrical components.

 

         Second, epoxy resin potting

         Advantages: Excellent high temperature resistance and electrical insulation, easy operation, stable before and after curing, excellent adhesion to various metal substrates and porous substrates.

Disadvantages: The ability to withstand cold and heat changes is weak, and cracks are easily generated after being subjected to thermal shock, causing water vapor to penetrate into the electronic components from the cracks, and moisture resistance is poor. And after curing, the colloid is high in hardness and brittle, and is liable to deform the electronic component.

Scope of application: Applicable to normal temperature and pressure electronic components, no special requirements for environmental mechanical properties.

 

         Third, silicone potting

         Advantage:Strong anti-aging ability, good weather resistance and excellent impact resistance;

         Excellent resistance to cold and heat, can be used at various working temperatures, can maintain elasticity in the temperature range of -60 ° C ~ 200 ° C, without cracking;

         It has excellent electrical performance and insulation ability, effectively improves the insulation between the internal components and the line after potting, and improves the stability of the use of electronic components;

         Non-corrosive to electronic components, no curing reaction by-products;

         Excellent rework ability to quickly and easily remove the seal assembly for repair and replacement;

         It has excellent thermal conductivity and flame retardancy, effectively improving the heat dissipation capability and safety factor of electronic components;

        Low viscosity, good flow, ability to penetrate into small voids and components;

        It cures at room temperature and can be heated and cured. It has good self-discharge performance and is more convenient to use.It has low cure shrinkage and excellent water and impact resistance.

        Disadvantages: high price and poor adhesion.

Scope of application: Suitable for filling various electronic components in harsh environments.