Pcb Copper Trace Finish
Then the copper and fibreglass prepreg sandwich is bonded along with epoxy and a giant press. It feels like you could have thin porous gold allowing the nickel to oxidize and will trigger poor wetting and solderablity. If an natural materials is deposited in a thin layer on the coating, it may discolor the material.
Any gold immersion coated board must be placed in a metallized ESD bag and sealed well. It will still solely last as long as 6 months before the gold becomes duller due to the diffusion of the substrate. The more expensive and much thicker auto-catalytic electroless gold process will be a greater approach.
This could or might not prevent the flux from doing its job, so solderability could also be affected to varying degrees. The finish was not ENIG, but either an OSP or a single-steel immersion coating like immersion silver, and the metal surface did oxidize. OSPs in particular are identified for this, especially when reflow is completed in air and there is a couple of reflow cycle. It is extensively believed that IBM was the primary major company to provide this finish credibility.
The newest OSP formulation are much more robust and are designed for lead-free assembly. They can handle multiple warmth cycles and have a one year shelf life.
The original formulas had a short shelf life of three-6 months and will only withstand one or two heat cycles. By right now's standards, this may be thought of applicable just for decrease applied sciences.