Hi Guenter,
interesting. Very interesting. You got fretting issues at 28 Hz? Caused by floor vibration? Really? I've been involved in several fretting problems (aircrafts), but then we had much higher frequencies, maybe multiples of lower resonances. Our equipments were transported by ship to the other side of the planet, and it was then the problems started. I'll check how they were transported, time at sea etc.
Thanks again
/inge
PS. What level of vibration?
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Grossmann, Guenter
Sent: onsdag 23 september 2009 09:41
To: [log in to unmask]
Subject: [TN] AW: [TN] Knock, knock, knock on the heaven's door
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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