Peter: If the decoupling caps are tantalum that could be the problem. tantalum caps have some problems and need to either be over rated or have current limiting. Some even have built in fuses.
This caused me much consternation in another job when the test engineers and design engineers `assumed' the parts were reversed. However upon closer scrutiny the parts were caught at in-circuit test before they disintegrated. In deed not reversed but couldn't take the direct connection to the power rail at the 25% derating. Just a thought from the past. > -----Original Message----- > From: pe...@itl.co.il [SMTP:pe...@itl.co.il] > Sent: 05 November 1998 22:17 > To: emc-p...@ieee.org > Subject: Burning Card Module > > Dear Members, > > I am sure some of you can give me ideas on how to analyze a card > module which in four different occassions caused charring and > smoke within the equipment. In all cases, fire did not spread and > the charring occurred in all cases, arounf decoupling SMT > capacitors located between the Vcc and ground. > > The subject card sits in an industrial type computer within a GSM > equipment. The card is fed by 5 V and 12 Vdc from the computer > power supply and employs two SE:V interfaces. It employs a > piggy board with a receiver with direct connection to an external > outddor antenna. > > Any suggestions how this may have happened in the field, on four > different occassions and the charring/burning occured around the > decouplng capacitors. > > For this let us assume PWB is flame rated 94V-0 and is > Recognized. > > Regards, > PETER S. MERGUERIAN > MANAGING DIRECTOR > PRODUCT TESTING DIVISION > I.T.L. (PRODUCT TESTING) LTD. > HACHAROSHET 26, P.O.B. 211 > OR YEHUDA 60251, ISRAEL > > TEL: 972-3-5339022 > FAX: 972-3-5339019 > E-MAIL: pe...@itl.co.il > Visit our Website: http://www.itl.co.il > > Best regards, Terry J. Meck Senior Compliance/Test Engineer Phone:215-721-5280 Fax:215-721-5551 hard copy; Fax PC: 215.799.1650 To my desk PC tjm...@accusort.com Accu-Sort Systems Inc. 511 School House Rd. Telford, PA 18969-1196 USA --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
