[Radio Wrangler]

You can learn things from a theft.

There was a PCB process where blank but drilled double-sided PCBs in panel form got coated in resist, exposed, developed and electroless copper plated to make the holes conductive. Then came thick electroplating to bring the copper up to thickness. Nickel electroplate came next, then finally, gold. Yup, real Gold.

The gold acted as etch resist once the photo resist was stripped. These boards looked glorious!. Solder resist was screened over the top.

They were stuffed and then went through the flow solder machine with pre-flux and post-wash.

New ingots of solder went in the machine, and slag was skimmed off the top. Slag was collected and put in a skip for disposal. After time, the recirculating solder in the wave section would be determined to have degraded a bit too far and getting close to making some dry joints. So the machine got emptied, cleaned and restarted with new solder ingots. The new solder was expensive, and we had to pay a fair bit for ethical disposal of the lead-bearing waste.

Someone drove a van into the yard one weekend. They went past cases of brand new solder bars to take the quite fullsolder slag waste bin.

What?

The initial reaction was happy that there was one bin we wouldn't have to pay to have removed, followed by annoyance that an empty bin hadn't been left. Only later did it seem to be realised as a criminal act.

Then came curiosity.

The reason for the solder going bad over time was that the wave was dissolving a little bit of the gold from each board, and after many boards, it was approaching a saturated solution. This spoiled its wetting properties.

That solder scrap was worth a lot more than the same weight in new solder bars.

So, who did it?

Inside job?

Did someone in the plant find out about the gold content and not point it out? Someone in the scrap contractor might well have known, but one word would have killed the golden goose for that firm. The bin was nicked when it was pretty full, which wasn't seen as a coincidence.

I don't know the solution to this mystery (sorry, bad pun, unintentional). I've never heard that it was pinned on anyone.

Maybe there wasn't that much pressure to solve the theft? The theft itself saved the firm what the disposal would have cost, and from then on the waste was kept securely and sold for serious money.

There was just that feeling that there might be someone around who shouldn't be trusted.

Unsolved gold robbery which actually benefitted the victim!

David