Inge
In the range of 10- 100 mm/s on the floor
Best regards
Guenter
>-----Ursprüngliche Nachricht-----
>Von: TechNet [mailto:[log in to unmask]] Im Auftrag von Jerry Dengler
>Gesendet: Mittwoch, 23. September 2009 13:47
>An: [log in to unmask]
>Betreff: Re: [TN] Knock, knock, knock on the heaven's door
>
>Hi Inge,
>
>We produced a product in the US for the US market that used a socket for
>a PLCC. This product's usage went up and the customer sent the
>production to China. At first all was well. After the production got
>to normal levels, suddenly they were getting a high level of out of box
>failures. These were all sent via ship. The earlier units were being
>air freighted in while the factory in China got up to speed. We found
>fretting at the socket to lead interface. We believe it is vibration
>from the ship that causes it.
>
>Recently the factory in China made 1000 units. 500 were air freighted
>and 500 were sent via ship. We left the 500 units sent by air on the
>skid until the ocean units arrived. We then tested all 1000 units. 122
>of the ocean units failed. None of the air units failed.
>
>Jerry
>
>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]] On Behalf Of Hernefjord Ingemar
>Sent: Wednesday, September 23, 2009 5:59 AM
>To: [log in to unmask]
>Subject: Re: [TN] Knock, knock, knock on the heaven's door
>
>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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