| | | Has any one seen failures of chip resistors after 1-2 years where the junction between the silver termination and the restive element on the top of the ceramic has corroded through. This results in a high resistance failure after this period of time. | | | | | | I understand that some people in the automotive industry have seen this even on conformally coated boards, the example I have been examining is not in the same type of environment. | | | | | | Look forward to hearing from a few people, many thanks.
Your problem may be related to silver migration (leaching) into the solder. I had what seems to be a similar problem. The solution was using solder with 2% silver content. See these pages for a bit more information:
http://www.ferroemd.com/page7.html http://www.ferroemd.com/page12.html
Regards, Pete Sorenson
| | | | | | | | What kind of flux was used when the board was built? Sometimes organic fluxes can cause corrosion if they are not cleaned off properly. Also if a component overheats often enough it can cause oxidation. I'm not sure if I understood the question the way you intended. Please respond if this helps. | | | | Ben K. | | | | It is a corrosion failure ie the connection between the silver termination and the resistive element has been eroded. There is no evidence on other areas of the board that flux is the cause. Normally dendrite growth provides a low resistance path and not a open or high resistance. The corrsion site shows silver salphide at the area of failure. The silver is from the termination which also has a tin lead coating. The failure is occuring at the junction with the resitive element on the top of the device. | | Many thanks. | |
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