I had an interesting conversation with a colleague the other day. They wanted to return some printed circuit boards to an off-shore manufacturer because not all of the surface mount pads would solder. I help friends and customers troubleshoot problems all the time. Its just good business.
“Was it the entire lot of boards or only a few?”, I asked.
“Well, when we soldered the first batch the pads wet with solder with no problem. The second batch from the same lot has solderability issues. The pads don’t wet properly. I can’t explain it but nothing has changed here. The boards have ENIG on them so it must be the boards.”
“Well, if the first batch soldered and the second batch from the same lot didn’t then there’s a problem. How much time has passed between batches?”
“Hmmmm. About three years”
We then proceeded to have a conversation about shelf life. This is a topic that I find many people don’t know about or understand properly. Put simply, (more…)