legg wrote:

============
Phil Allison



The item itself looked new, but was in fact 9 years old.
Eventually I found 3 open resistors, all with values like 1Mohm.

Googling tells me this is a known hazard not shared with through hole parts - has to do with the use of silver plating on top surface of the resistor being subject to sulphiding and similar air borne contaminants.


As formation of sulphides is a surface phenomenon, I doubt
it plays a role in properly reflow-soldered junctions.


** Never said it did.

As the silver layer is on TOP of the SMD chip, failure occurs at the silver to resistive element interface.

You would need a microscope to see evidence of it.

My concern is that many more of the same resistors will fail open in time.


...... Phil