Unsoldered gold pads on unleaded wave solder process

Sorry, but I don't have a quick and easy answer. Before jumping the 'black pad shark,' tell us more about your boards ...
* Is the gold still on the pads after soldering?
* Can you make the pads take solder using a soldering iron?
* Does this happen to all boards? Or just every so often?
* Are all of these boards from a single source? Or are they from multiple suppliers?
* What is the 'actual' plating on top of the copper on the boards?
* How are the boards packaged from your supplier?
* How are boards stored after receipt from the supplier?

reply »

It is possible that there is nickel contamination in the gold. Depending on your plating board vendors put nickel down first. The plating also could be to thin. Dave had a good suggestion in trying to solder the pad with a Iron that will tell a lot.

reply »

Yes pads are still gold after the wave soldering process
even if you wave solder a pcb several times.
I have tried soldering using an iron and the solder takes to the pad as you would expect.
This happens on all boards of this type and all boards are from single source packaged in sealed bubble wrap.
PCB's are stored on shelves in the main assembly area.
The plating on the PCB is copper with an Electroless Nickel Gold Immersion finish.

Thanks for the help so far

reply »

Are you spray fluxing ? If so, check that you are getting flux onto the whole pcb uniformly....
That BLT flux is a water based material, are you getting rid of all the water in the preheat before you get to the wave ( can you hear any spitting as the pcb travels into the wave ?) Any water spitting will interfere with the solder flow over the surface and cause solder skips.

reply »