KK, Have you found any carbonization on the no clean flux residue? We had found the same problem before which was due to high temperature localised on the particular area during burn-in causing carbonization of flux residue and result in electrical leakage. Hope this help. Regards, WM Cheng ______________________________ Reply Separator _________________________________ Subject: [TN] Voltage Across 1206 SMD Author: "TechNet E-Mail Forum." <[log in to unmask]> KK Chin <[log in to unmask]> at Internet Date: 2/8/99 12:29 Dear Technetters, We see some failures in one of our products due to resistance drop across a 1206 resistor on a PWB assembly. The products failed after hours of operation in the burn-in environment and is suspected to be the effects of SIR drop or electromigration. There's 135Vdc across the resistor during operation. The designer thought it's ok because the resistor itself has a max. operating voltage of 200Vdc. The land pattern is of the IPC-SM-782 standard (1.2mm gap in between). The solderpaste is also claimed to be compliant with IPC-SF-818 and Bellcore TR-78 in terms of SIR and EM. My understand is that SIR and EM are tested with bias voltage of 50Vdc and 10Vdc respectively. Are these standard tests really applicable to this high voltage case? Thanks! KK Chin Artesyn Technologies 47173 Benicia Street, Fremont, CA 94538 ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text n the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for ditional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 t.312 ################################################################ ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################