Hi Inge
Vibrations around? I just had recently a similar problem in an industrial environment. Failure analysis showed fretting on socket spring- contacts. When I made vibration measurements I found quite a spectrum of low level vibrations on the floor but a clear resonance at 28Hz in the rack.
Best regards
Guenter
>-----Ursprüngliche Nachricht-----
>Von: TechNet [mailto:[log in to unmask]] Im Auftrag von Inge
>Gesendet: Dienstag, 22. September 2009 21:34
>An: [log in to unmask]
>Betreff: [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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