I read in !emc-pstc that Chris Chileshe <chris.chile...@ultronics.com> wrote (in <01c26f7a.00510c40.chris.chile...@ultronics.com>) about 'Testing for dry joints' on Wed, 9 Oct 2002:
>The specific problem is that the joints appear to be electrically >sound to start with, meaning the units are getting through function >test, but once exposed to endurance (lengthy) tests or worse >still, actual practical use, the gremlins begin to show. The fault >analysis almost invariably leads to a connector dry joint. Can you please provide more information: - do these joints involve gold-plated parts? - do the endurance tests and use involve vibration? Gold plated parts can cause bad joints through the development of a non- conducting interface between the solder and the metal that was gold- plated before the plating dissolved in the solder. Such bad joints are extremely difficult to find, because the fault is hidden inside a perfectly formed solder pad. The remedy is usually to increase the soldering temperature, but a change of flux may also be necessary. Failure due to vibration produces a characteristic grey, almost micro- crystalline appearance of the solder pad. The remedy is self-evident, but may be difficult to implement. I know a way of detecting some types of *potential* bad joint, using an audio-frequency non-linearity test. It can be very sensitive, but obviously I don't know whether it would work in your case. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk Interested in professional sound reinforcement and distribution? Then go to http://www.isce.org.uk PLEASE do NOT copy news posts to me by E-MAIL! ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
