Dave I remember seeing a very similar problem on a low voltage ceramic hybrid a few years ago but unfortunately it was a different company so I don't have a lot of information but you may want to try:- 1. Cleaning the furnace muffle. If your muffle is as dirty as mine was it could well be a source of sulfur. 2. Check to see if any of the operators smoke. The sulfur may be introduced from their hands. 3. I seem to remember that we stopped using clear silicon gel (a 2 part Dow Corning material) on these hybrids so it maybe worthwhile trying to build and test a few circuits without encapsulant. Hope this is some help ===== Original Message from TechNet@PAT [log in to unmask] (TechNet E-Mail Forum.) at 24/09/98 02:08 >I need help tracing the possible root causes for a circuit failure from >the field. Does anyone have any experience with open circuit traces due >to a silver sulfide corrosion concentrated at the juncture tin-lead >solder joints and silver thick films? We are seeing this only on joints >that are low voltage potential. There is silver sulfide corrosion at >other randomn areas, but the heavy corrosion is primarily at just a few >points where the solder and silver meet. Under the microscope, it looks >like a black worm crawling along the interface between the solder joint >& the silver thick film. We pot the circuit board in silicone gel to >protect the circuit from moisture. So far, we haven't traced the source >of sulfur to any material that we use to make or to package the circuit >board. >The packaging does not contain cardboard, so sulfur from the packaging >is out. We meticulously clean the board after reflow soldering the >printed solder paste, so flux is out. Is it possible that we are getting >sulfur gas from the enviroment? The environment is automotive, >underhood. Is it possible that there is a galvanic action that is >concentrating the corrosion to just a few solder joints? >Thank you all for your time. > >################################################################ >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 >################################################################ Mark Austin (Process Engineer) ACW Technology Ltd Hylton Road Petersfield GU32 3XX TEL - (01730) 300000 FAX - (01730) 266045 DDI - (01730) 304401 MA @ ACW.CO.UK ################################################################ 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 ################################################################