Protective Material
Encapsulation compounds shield sensitive electronic assemblies from moisture, chemical exposure, and mechanical shock. This protection is provided by a polymer potting adhesive, which fills the housing cavity and cures to form a solid protective barrier around the componentry. The material selection depends on the operating temperature and the thermal expansion of the board.
Dispensing Process
Liquid resin is dispensed into the sensor housing under vacuum to prevent air bubbles from forming. The curing profile of the polymer potting adhesive relies on a specific thermal cycle to ensure complete cross-linking without generating high shrinkage forces. Insufficient curing or trapped voids can compromise the moisture seal and create stress points on the electronics.
Automated dispensing systems must monitor the mix ratio of two-part systems to maintain the specified material properties.
Mechanical Stress
Differential thermal expansion between the cured resin and the circuit board can shear delicate solder joints. The elasticity of the polymer potting adhesive reduces this mechanical stress during temperature transitions. Harder compounds offer better physical protection but generate higher internal stresses than soft silicones.
Designers must balance these properties based on the environmental requirements of the application.
Material Qualification
Standardized testing verifies the dielectric strength and moisture resistance of the cured compound. Any degradation of the polymer potting adhesive after temperature cycling is measured by insulation resistance tests. Material data sheets specify the maximum continuous operating temperature before the polymer begins to break down.
This limit determines the suitability of the compound for automotive or industrial environments.
