Hi Inge!

The DIPS aren't socketed, are they?

Wayne

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge
Sent: Tuesday, September 22, 2009 3:34 PM
To: [log in to unmask]
Subject: [TN] Knock, knock, knock on the heaven's door

Well, not exactly that, but knock, knock, knock on a earthly board. One customer needs fix a intermittent problem asap. 19 inch racks with hundreds of PTH double sided boards, old technology, no BGAs, no QFMs etc, but lots, lots of DIPs. The edge contact fingers have a very thick and good gold over nickel, and the backplane connectors have really stiff double tongues. The contact pressure/sq is extremly high and I think the contact spots are really gastight once the board is plugged in. Now, they have electrical issues, and they've found, that the signals are interrupted or coming back when they knock on the boards. Someone is going to take a flight the other day to fix the problem. The electricians believe, stubborn as mules, that the only think needed, is to take out the boards and clean the edge contact fingers with a solvent and that will fix it. Myself, with quite many year's experience from connectors, I don't think that is the problem, because when such robust contact springs wipe along the contact fingers, they slide pretty deep into the gold and makes good connection. Each spring has double contact ridges, so the risk that some dirt should cause interrupts is minimal. There is more that talks against their theory, namely, that the problem is still there after plugging, deplugging more than once. I'm sure there is a solder joint issue, or maybe a bond wire problem in the packages.
Logically, this later is more likely because you have thousands of solder/bond joints vs, just some one hundred edge connector ditto. A ratio like 10,000/100 per board. Without knowing all details, what is your general experience between the index finger and the big toe?

/Inge

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