A couple of lifetimes ago, we saw something similar due to large sized chip capacitors becoming resistors. Something about being at the manufacturing process limitations of the large size of the capacitor. In those days it was a 330 nF capacitor that caused the problem. I know that processes have improved considerably in 15 years, but it might be worth checking out.
Don Umbdenstock Sensormatic > ---------- > From: [email protected][SMTP:[email protected]] > Reply To: [email protected] > Sent: Thursday, November 05, 1998 5:16 PM > To: [email protected] > 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: [email protected] > Visit our Website: http://www.itl.co.il > > --------- > This message is coming from the emc-pstc discussion list. > To cancel your subscription, send mail to [email protected] > with the single line: "unsubscribe emc-pstc" (without the > quotes). For help, send mail to [email protected], > [email protected], [email protected], or > [email protected] (the list administrators). > --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to [email protected] with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to [email protected], [email protected], [email protected], or [email protected] (the list administrators).
