Datasheet Parameter for Zener Diode

I know this doesn't help a lot: but, good question.

Look at this data sheet:-

http://www.onsemi.com/pub_link/Collateral/3EZ6.2D5-D.PDF

from On semi. It specifies power dissipation for lead temperature at lead length 3/8" (about 10 mm), and, a much lower power dissipation at T ambient.

Lots of the surface mount data sheets specify power dissipation for components mounted on certain areas of ceramic (again not normally very useful).

Maybe you could write to Vishay. I think all these suppliers need to be a bit more helpful. I guess the problem is that if they say anything specific about "normal" conditions they may open themselves to litigation.

I had a brief look for equivalents to see if other data sheets were better but didn't get anywhere you might do better if you persevere.

3¼ Watts seems like a lot from a little package like that.

Tamb is the ambient air temperature without circulation. So under this condition the maximum acceptable power dissipation of the zener is 1.3 watts. TL is the temperature of the leads of the diode. So if you have sufficient cold air or oil circulation to maintain 25°C on these leads, the diode can dissipate a maximum of 3.25 watts without damage.