Reason for considering junction temperature in derating

[praveenhunchi]

Hi,

I was performing a derating analysis on a diode and as per MIL STD 975, the parameters to be considered are PIV, surge current, forward current and Junction Temperature.

The max junction temperature in MIL STD 975 is around 125 deg C for all kinds of diodes. Does that mean for any diode chosen , i need to maintain a junction temperature below 125 deg C ( even if the Tj max specified in the datasheet be 150 deg C).

A more serious concern was on why are we limiting the junction temperature to 125 deg C, the thermal properties of the junction material are not going to degrade under any condition as long as it is operating below Tj max, then why limit it to 125 deg C ?

 

[dick_freebird]

MIL standards are kind of a "living history of ways people
have failed" and not all of them are realistic or relevant
to a particular item. They are more of an agreed upon
"can't fail" that eliminates the need to dig deeper.

If you want to take it further then it's on you to supply
the proof, over and over, to every PhD joker from TASC
that needs a few billable hours.

Not that I've been there.