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, when 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.
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: