Printed circuit boards (PCBs) with immersion finishes such as electroless nickel immersion gold (ENIG), immersion tin, silver, and OSP are appealing because they are lead-free. However, if handled improperly, these materials are susceptible to oxidation and corrosion from exposure to moisture and humidity. This oxidation causes dewetting after soldering, which can lead to poor joints at assembly and ultimately lead to failure of the board.
Solutions For Handling PCB Surface Finishes
Careful handling will minimize oxidation and associated problems. Even natural oils from human skin can tarnish these finishes, so gloves are always recommended when handling printed circuit boards with immersion surface finishes. Additionally, storing your circuit boards in airtight packaging helps prevent oxidation due to humidity and moisture.
Examples:
PCBs with ENIG finishes that have been heavily oxidized due to exposure to moisture:
Results of solder testing and the dewetting caused by the oxidation on the ENIG surface mount pads:
Taking the time and simple steps to properly handle and care for ENIG and other immersion finish circuit boards can dramatically reduce defects from occurring down the line. Fewer PCB defects means lowering your PCB costs and increasing your margins.
Summary
Immersion surface finishes such as ENIG, immersion tin, silver, and OSP provide lead-free solutions for PCBs, but they are highly vulnerable to oxidation and corrosion if mishandled. Exposure to moisture, humidity, or even natural skin oils can result in tarnishing, solder dewetting, and poor joint formation during assembly.
By following simple precautions like wearing gloves, maintaining airtight packaging, and controlling storage conditions, manufacturers can prevent oxidation, improve solderability, and reduce costly board failures. Proper care extends the reliability of the boards and helps control overall production costs.
Key Takeaways
- Immersion finishes like ENIG, tin, silver, and OSP are lead-free but prone to oxidation if exposed to moisture or poor handling.
- Oxidation leads to dewetting during soldering, which creates weak or unreliable joints that may cause board failure.
- Natural oils from human skin can tarnish finishes, making gloves an essential precaution during PCB handling.
- Airtight packaging and controlled storage conditions help prevent oxidation from humidity and environmental factors.
- Proper handling of immersion finishes reduces PCB defects, lowers manufacturing costs, and improves long-term product reliability.
