Surface Treatment Processes for PCBs
1. Electroless Nickel/Immersion Gold
The electroless nickel/immersion gold process is commonly used for PCBs with connection requirements and longer storage periods, such as mobile phone keypads and router housings. This process gained popularity in the 1990s for its advantages over hot air leveling flatness and the removal of organic coating flux. Despite challenges with black discs and brittle nickel-phosphorus alloys, nearly every high-tech PCB factory now utilizes electroless nickel plating/immersion gold wire. Approximately 10%-20% of PCBs currently use this process.
2. Immersion Silver
Immersion silver offers a cost-effective alternative to electroless nickel/immersion gold for PCBs with connection requirements. Its good flatness and contact properties make it a favorable choice for reducing costs in communication products, automobiles, computer peripherals, and high-speed signal design. Although growth has been slow due to tarnishing and solder joint voids, approximately 10%-15% of PCBs currently use this process.
3. Immersion Tin
Introduced in the past decade, immersion tin is ideal for meeting the demands of production automation and is commonly used in communication backplanes. However, tin can lose its solderability over time, necessitating optimal storage conditions. The limited use of immersion tin is attributed to the presence of carcinogenic substances. Approximately 5%-10% of PCBs currently undergo the immersion tin process.
Concluding Thoughts
As customer demands and environmental regulations evolve, the variety of surface treatment processes for PCBs continues to expand. Choosing the right surface treatment process can be challenging, but it is essential to prioritize meeting customer requirements and environmental protection. The future direction of PCB surface treatment processes remains uncertain, emphasizing the importance of selecting processes with development prospects and versatility.
