[SOLVED] What does "TS" stand for on a transistor datasheet?

Here is the datasheet for Infineon's NPN biploar BC847A. With respect to "Total power dissipation", it states " TS ≤71 °C, BC847-BC850...".
What does "TS" mean here? Seemingly it's not temperature for storage, 'cause we can see from below the storage temperature is designated as Tstg, and the power dissipation test obviously has nothing to do with the storage temperature. What can the "TS" be ?

Temperature of the surface (case)? I haven't seen that before.

barry said:

I haven't seen that before.

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Dittto.
Anyway, when in doubt, look at another datasheet.
e.g. This one from NXP puts it in more normal terms.

It is the temperature of the substrate (the PCB material) using a predefined trace layout. The heat mostly spreads out via the leads, and these are thermally connected to the PCB.

WimRFP said:

It is the temperature of the substrate (the PCB material) using a predefined trace layout. The heat mostly spreads out via the leads, and these are thermally connected to the PCB.

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So, is that the same as Tj (junction temp)?

Wait, you mean PCB substrate? That's a weird spec. As you say, heat is conducted by the copper, the substrate does little for heat conduction, so why would that even enter into the discussion?

Barry, My statement is somewhat confusing. The best definition for Ts is the temperature of the soldering point, that is where the hottest lead touch the PCB. They use the temperature of the hottest soldering joint (for bipolars where the collector is directly atached to the collector lead, the collector lead is the hottest).

In the image of the datasheet, they specify: Ts< 71 degr, dissipation 330 mW (first line). So there is 150-71 = 79 degr drop between the junction and the solder point at the PCB (assuming 150 degrees maximum junction temperature). So Rthjunction-solderpoint = 79/330mW = 240 K/W.

To find the junction to ambient resistance, you need to know Rsolderpoint-ambient, and that depends on substrate type, substrate thickness, copper thickness and size, additional vias, etc.

So the overall thermal resistance is the sum of Rj-s and Rs-a (s = solder point, a = ambient, j = junction).

Manufacturers generally provide data on how to estimate Rs-a, as measuring the solder point temperature requires a thermal imaging camara with very good resolution (I don't have that).

hopefully this makes more sense to you.

WimRFP said:

hopefully this makes more sense to you.

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I'd just put a big fan in there and hope for the best. :grin:

Why don't you look at the standard spec's on the datasheet from a MAJOR manufacturer like NXP (Philips) instead of from (who in the heck is) Infineon?
Notice that there are four packages and they all have different temperature ratings.

Infineon have a 4 billion Euro turnover and are a spinoff of the semiconductor division of Siemens so I think they are a major manufacturer.

Keith

Audioguru said:

Why don't you look at the standard spec's on the datasheet from a MAJOR manufacturer like NXP (Philips) instead of from (who in the heck is) Infineon?
Notice that there are four packages and they all have different temperature ratings.

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"Who the heck is NXP?"
--Infineon

barry said:

"Who the heck is NXP?"

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I asked that about 7 years ago when it was a division of Philips then became separate company.