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In printed circuit board (PCB) fabrication, surface preparation is a critical process that ensures strong adhesion, reliable plating, and long-term product performance. Without proper surface treatment, manufacturers may encounter defects such as delamination, poor solder mask adhesion, and plating failures. This article examines key surface preparation techniques, common defects resulting from improper processes, and real-world case studies that illustrate best practices.
Types of Surface Preparation
Mechanical Surface Preparation
Mechanical techniques physically remove oxidation, contaminants, and residues while roughening the surface for better adhesion.
- Brushing (scrubbing): Rotating abrasive brushes clean the copper surface and enhance adhesion for dry film lamination and solder mask application.
- Risks: Overbrushing can reduce copper thickness and damage fine traces, while under brushing leaves oxidation, leading to poor adhesion. You can also develop problems via smear from the brushes if they are worn or if the pressure is too high.
- Prevention: Use controlled brush pressure and monitor brush wear to maintain uniform abrasion. Implement process validation with cross-sectioning to ensure proper copper thickness retention.
- Abrasive Blasting (microblasting): Fine aluminum oxide or glass beads roughen PTFE and other difficult-to-bond substrates.
- Risks: Over-etching can weaken copper traces or alter dielectric properties; under-etching results in poor adhesion and delamination. Defects will also result from contamination from the grit used, with through-holes especially vulnerable.
- Prevention: Optimize blasting pressure, nozzle angle, and distance. Use a precise grit size for controlled material removal.
To read the entire article, which originally appeared in the May 2025 issue of PCB007 Magazine, click here.
