Posts Tagged ‘shelf’

When ENIG Doesn’t Solder.

Sunday, November 25th, 2012

One of the misconceptions about Electroless Nickel Immersion Gold (ENIG) is that it remains solderable for an unlimited amount of time. This misunderstanding is based in the fact that gold is a noble metal. Noble metals are metals that are resistant to oxidation and corrosion. Hence the belief that ENIG remains solderable since gold is the metal that we see. Some people in the electronics industry are surprised when they learn that ENIG has a solderable shelf life of (more…)

Shelf Life Identification of a PCB.

Saturday, November 5th, 2011

How does one identify the shelf life of a printed circuit board?

By convention the printed circuit board fabricator shall mark the printed circuit board with a four digit date code. The date code consists of a two digit week number ranging from 01 (the 1st week in January) to 52 (the last week in December). The year code would be 99 for the year 1999 or 01 for the year 2001. Commercial fabricators use a week/year format. Date code 0199 would be the first week of January of 1999. Military fabricators use a year/week format. Date code 0152 would be the last week of December of 2001. The printed circuit board fabricator shall place the date code on what is traditionally referred to as the circuit side of the printed circuit board.

What is the circuit side of a pcb?

To understand the term circuit side, you need to learn a little history of the printed circuit board industry. In the beginning (more…)

Shelf Life = Solderability = Supply Chain Management

Saturday, June 25th, 2011

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”

“ouch”

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…)