Hi,

I could use some help on a problem.

I recently revised a board and received a prototype quantity to audit from the same vendor that fabs the production boards.
The prototypes that we received are SMOBC/HASL with LPI soldermask and are double-sided smt reflow with manually
soldered through hole parts (same as the previous revision).

On the new prototype run, there is what looks like a slight goldish tint to the exposed tin/lead pads on the board.
When the bare board is viewed under magnification, the solder surfaces look grainy and mottled, not shiny like one would
expect with tin/lead.  There is a definite definition where the soldermask border is located around exposed pads, and
the boards do not feel sticky.

So far the boards appear to have soldered just fine in both top side and bottom side reflow operations, using OA water-soluble flux.
The boards are having a problem in the through hole (manual) soldering op, using rosin flux.
The solder joints are very poor, and they have some black stuff bubbling out of the holes.
One engineer scratched off an area of a smt pad on a bare board with a white eraser, and then touched a hot solder
iron to the scratched area and the solder wetted up to the area that was not scratched off.

The vendor says that it is some kind of tarnish that is over the surface and in the holes.  They have a few overage boards
still at the fabrication site, and those boards have the same goldish hue.
We received these prototype boards on a 2-week delivery, and began assembling the boards
the day after we received them.

Does anyone have any experience with a problem like this or have any ideas what the problem could be?
I am having some trouble believing that it is tarnish on HASL finish.

Any ideas would be appreciated.

Thanks,

Kaye Clayo
Sr. P. C. Layout Designer


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