Reminds me of a problem we had years ago. We were building circuit cards for GE Medical and they were seeing similar cracked solder joint caused field failures.
They loaned us a shake table and the software they wrote specifically for the boards we were building. We loaded boards into the fixture and ran the profile and some parts were actually popping off the boards! Funny thing, it wasn't the larger heavier parts we thought would be the problem. GE had to come in and "tweak" their profile and we experienced no more failures as long as we ran the program.
GE still had the same fractured solder type field failures & they finally attributed them to equipment vibration and not manufacturing defects. I guess it's all about resonant frequencies.
Also, I had a laptop at work and was required to take it home every day for security reasons. So it rode home & back, 45 miles each way in the trunk of my Harley-Davidson. I had 4 keyboards fail and every one had fractures in the ribbon cable right where it plugged into the motherboard. I never did explain resonant frequencies to IT.
Tom
From: David Beierl [mailto:dbeierl@gmail.com] On Behalf Of David Beierl Sent: Monday, February 28, 2011 12:39 AM To: Tom Hargrave Cc: vanagon@GERRY.VANAGON.COM Subject: RE: Unbelievable, was Re: Spare ECU
At 01:08 AM 2/28/2011, Tom Hargrave wrote: >The solder fatigue you took pictures of is common for electronics >that have been in a vehicle for a long time. Ayuh. And not by any means just automotive gear. So why aren't there more images out there? > usually the parts that fatigue are heavier power resistors, caps > or inductors. They seem to be more susceptible than smaller, lighter parts. To amplify on that somewhat: heavy parts, parts that stand away from the board, parts subject to thermal cycling and most particularly parts with pronounced thermal cycling that are mechanically connected to a stiff external structure (like the devices connected to the heat sink in our ECUs). But the curious thing I'm finding in the ECUs is bad joints in small light parts that sit right on the board, in low-power DIP leads, in the flattened-ribbon connections between boards. I find that surprising. Yours, David _____ No virus found in this message. Checked by AVG - www.avg.com Version: 10.0.1204 / Virus Database: 1435/3472 - Release Date: 02/27/11 |
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