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Electroless Nickel-Phosphorus Alloy Plating Process for Rigid Boards

Time:2025-07-28 Views:1

Electroless Nickel-Phosphorus Alloy Plating Process for Rigid Boards

The electroless nickel-phosphorus (Ni-P) alloy plating process is a key surface treatment for rigid boards, providing excellent corrosion resistance, wear resistance, and solderability. This autocatalytic process deposits a uniform Ni-P layer without external current, making it ideal for complex rigid PCB geometries with blind vias or high-aspect-ratio holes.

The process begins with pretreatment, critical for adhesion. Rigid boards undergo degreasing (using alkaline cleaners at 50-60°C) to remove oils and contaminants, followed by acid pickling (10-20% sulfuric acid) to etch the copper surface, creating micro-roughness. Activation with palladium chloride solution (0.1-0.5 g/L) ensures catalytic sites for nickel deposition.

The plating bath typically contains nickel sulfate (20-30 g/L), hypophosphite (25-40 g/L, reducing agent), and complexing agents (citrate or glycine) to control pH (4.5-5.5) and prevent nickel hydroxide precipitation. Operating at 85-95°C, the bath deposits Ni-P alloy at 10-20 μm/h, with phosphorus content ranging from 5-12%low phosphorus (5-8%) offers higher hardness, while high phosphorus (10-12%) enhances corrosion resistance.

Post-plating, a heat treatment at 200-400°C for 1-2 hours improves adhesion and hardness (up to 800 HV). The final layer provides a barrier against oxidation, ensuring reliable solder joints and protecting copper traces in harsh environments. This process meets IPC-4552 standards, ensuring uniformity (±10% thickness) and adhesion strength (>0.5 N/mm) for rigid boards in automotive, industrial, and aerospace applications.

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