Re: Diode Failure Mechanism & Mode




RST Engineering (jw) wrote:
Suppose I have a popcorn glass diode like a 1N4148. I will slowly advance
the temperature so as to not thermally shock the glass.

At what temperature (or range of temperatures) would you expect the diode to
fail?

What is the mechanism for the failure (thermal expansion, solder melt,
etc.)?

What is the mode of failure (short, open, gross deterioration, etc.)?


Thanks,

Jim

According to empirically compiled data over many years (decades?), Mil
Handbook 338 lists 3 modes of failure for diodes (such as the 1N4148)
and the likelyhood of each:

Short Circuit -- 75%
Intermittent -- 18%
Open circuit -- 6%
I suppose "other" would be the remaining 1%, or the numbers were
truncated after the decimal place.

These are failures under normal operating circumstances. At higher
temperatures, I don't know how the probabilites would change, but I
don't believe the percentages would change that much.

As for mechanisms, you would have to get a materials expert to answer
that. I have personally seen overheated diodes "go" both ways, most
recently being a zener that shorted out.

Tom

.



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