Fluororesin Coating Composition for PCB Adhesion and Heat Resistance

The patent uses a composite coating composition containing multiple fluororesins (FEP and PTFE) with different functional characteristics. The FEP resin provides heat resistance and electrical properties, while the PTFE resin with controlled molecular weight and specific functional group content improves adhesion to metal substrates. This composite approach allows simultaneous achievement of heat resistance and adhesive properties that single fluororesins cannot provide alone.

The patent controls the molecular weight and functional group content of PTFE resin within specific ranges (molecular weight 10,000-1,000,000, functional groups 1-100 per 10^6 carbon atoms). This parameter optimization ensures adequate adhesion to smooth copper surfaces while maintaining the electrical properties required for high-frequency applications. The controlled functional group content prevents excessive cross-linking that would harm electrical performance.

The patent optimizes the silica filler content within specific ranges (0.1-10 parts by mass per 100 parts fluororesin) and controls particle size distribution (0.1-10 μm average diameter). This controlled addition provides sufficient adhesion improvement while minimizing the impact on thermal expansion coefficient. The fluororesin matrix dominates the thermal expansion behavior, allowing silica to enhance adhesion without significantly altering the overall thermal stability.