Vapor Deposition
Vacuum-deposited poly(para-xylylene) films provide uniform conformal moisture protection across circuit traces and sensing elements. Applying parylene c coating involves gas-phase polymerization inside a vacuum chamber, depositing a pinhole-free polymer film over complex three-dimensional geometries. The vapor-phase process ensures uniform coating thickness over sharp edges, deep crevices, and component under-fill areas without meniscus formation or surface tension pooling.
Chlorine substitution on the phenyl ring gives Parylene C high dielectric strength, low gas permeability, and resistance to organic solvents and corrosive vapors. Metrological inspection uses spectral reflectometry and step-height profilometry to measure film thickness against target specifications.
Dielectric Barrier
High dielectric breakdown voltages protect underlying circuit traces from electrical leakage and ionic contamination. Thin coatings preserve high electrical insulation resistance between high-density conductor traces under humid conditions. Low dielectric constants minimize parasitic capacitance additions to sensitive sensing nodes.
Verification testing subjects coated boards to high-voltage isolation breakdown tests.
Pin-hole Evaluation
Gas-phase deposition eliminates pinholes down to sub-micron thickness levels. Continuous polymer films block corrosive gas migration to sensitive metallic bond wires. Salt spray testing exposes coated test coupons to corrosive atmospheres to evaluate coating continuity.
Microscopic inspection confirms complete surface encapsulation without voids.
Thickness Specification
Coating thickness targets range from two micrometers to twenty micrometers based on application requirements. Thickness measurements verify uniform film growth across flat substrates and component edges. Regulatory standards govern coating compliance for harsh environment electronics.
