This article discusses an abbreviated technique that uses the tools of HALT to expose hard-to-find defects in products returned by customers, written by Gary Delserro and published in Evaluation Engineering Magazine.  Click on the link to view the article in PDF, Exposing Hard to Find Defects.

How many times have your customers returned products or circuit boards with reported defects that you can’t find?  Every manufacturer experiences this situation at some time.  Your customer reports a problem in your product and sends it back to you.  You test the faulty product in your lab and the problem doesn’t occur. Sometimes you try to bend it or tap it against the table.  You may even try heating it in a chamber or with a heat gun or using a freeze spray.  Still the problem does not expose itself.