That is a very disturbing, sobering report.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Hfjord
Sent: May 9, 2007 1:00 PM
To: [log in to unmask]
Subject: [TN] SV: [TN] Strange one?
Here is the report. Read chapter 2.1 the aircraft was destined to accident. Cause: Polyimide wiring!
The start of the accident was in the microscale, but the result was horrible.
It's spoky reading.
When I got the preliminary report many years ago, I sent it to our staff immediately, and after that we have very little Polyimide wiring. But new generations come, and this accident will be forgotten.
http://www.iasa-intl.com/pdf/SEVEN_YEARS.pdf
Inge
-----Ursprungligt meddelande-----
Från: Hfjord [mailto:[log in to unmask]]
Skickat: den 9 maj 2007 20:33
Till: 'TechNet E-Mail Forum'; [log in to unmask]
Ämne: SV: [TN] Strange one?
Ioan,
I have to check carefully to be sure, but some years ago, we had a fire in a equipment at high altitude. Luckily, it was just experimental stuff. The reason was that the flex material undergoes certain change, and cold+mechanical friction+voltage caused leakage and finally arcing.
An airplane went down by that cause years ago. I got the report, but don't know if I have it still. Think it's not confidential any more.
You've certainly heard of that already. I don't remember the exact failure sequence, so I repeat that I need check. Would be disastrous to say something wrong here. Anyone who got information on that accident?
Such failures must be extremely rare.
Inge
-----Ursprungligt meddelande-----
Från: TechNet [mailto:[log in to unmask]] För Chuck Brummer
Skickat: den 9 maj 2007 16:49
Till: [log in to unmask]
Ämne: Re: [TN] Strange one?
Iain,
I look forward to hearing. I t is hard to believe that there we not a high current arc on the burnt looking sample. The white or near white could be something else like moisture. I have seen failures of the oxide but they are not usually that even. If there are larger blisters and you cut them open then catch the smell of ammonia that would be from moisture.
Are you X-sectioning?
Chuck Brummer
3M Manufacturing Engineer
8357 Canoga Ave.
Canoga Park, CA 91304-2605
(818) 734-4930
"Braddock, Iain" <[log in to unmask]> Sent by: TechNet <[log in to unmask]>
05/09/2007 02:42 AM
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Re: [TN] Strange one?
Chuck,
That was my comment to the Lab however they were adamant that wasn't the case. The area under the blasted part on pic 1 was delaminated but due to the surface of the Cu being etched away. They managed to replicate the etched area on the Cu under the Polyimide and the fact it became conductive by placing a spot of Alkaline on the board.
I will be checking another board with similar test fault though that will not be until next week.I'll let you now the outcome.
Regards,
Iain.
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Sent: 08 May 2007 17:54
To: TechNet E-Mail Forum; Braddock, Iain
Subject: Re: [TN] Strange one?
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Iian,
Stop fixing small shorts with your hi pot tester. Wow, Big flash and the short is gone leaving you on pic 1 a delaminated area and on pic 2 the burnt remains.
Bet if you look real close you will find a sliver of metal or a copper fiber.
Chuck Brummer
3M Manufacturing Engineer
8357 Canoga Ave.
Canoga Park, CA 91304-2605
(818) 734-4930
"Braddock, Iain" <[log in to unmask]> Sent by: TechNet <[log in to unmask]>
05/08/2007 09:23 AM
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[TN] Strange one?
Hi all,
Stevie G has been kind enough to post a couple of pics of a flexi anomaly I've come across.
Been having problems with some flexi-rigid boards failing at Ins/Cons test due to insulation breakdown - tested at 200v.
Had the lab do some exploratory work and the guys have come up with these pics. along with the fact that the Polyimide was conductive around the areas highlighted on the pics. but only localised. The Lab view seems to be that something was left on the board during fabrication and caused the problem; they have their suspicions but would like to know if anyone else has encountered a similar problem.
http://stevezeva.homestead.com/files/Flex_Problem_1.JPG
<http://stevezeva.homestead.com/files/Flex_Problem_1.JPG>
http://stevezeva.homestead.com/files/Flex_Problem_2.JPG
<http://stevezeva.homestead.com/files/Flex_Problem_2.JPG>
Regards,
Iain.
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