Thermal transfer for a TO-92

[abit]

If I solder it in-place with the leads bent so that the flat face of the IC is in contact with an exposed pad to the ground-plane - is this going to provide significant heat relief? How should I make this reliable or better, with some thermal compound, or this is not a good solution or not worth the effort? Lets assume the IC might going to run hot for a short while only, or switching, and in case it might not have thermal shutdown built-in as most transistors do not. Should I design a PCB with this option in mind?

Update:

Thanks, I suspected this, not worth the effort designing a PCB that way..

[radioFlash]

To get good thermal transfer, you need to have some pressure applied, and bending the leads won't provide much force and won't be reliable, and TO-92s have a very large thermal resistance anywy, so you won't gain much. There are TO-92 heatsinks, but I don't think they're worth it. If you're concerned about heat, consider a TO-220 or other package.

[T3sl4co1l]

As long as you have something filling the gap (you don't really need clamping pressure, but without it, the gap can creep open is the thing), you can get slightly better, but the plastic stinks for conduction, so it's not going to be much.

If you can do SMT, SOT-89 or 223 will be much better, up to a watt or two.

Tim

[jay]

Thermal adhesive might do the trick.

[digsys]

  Thermal adhesive might do the trick. 

Arctic cement / Arctic silver will give you the best thermal dissapation, but as others have said, the package isn't designed to get rid of heat.

[abit]

"Arctic cement / Arctic silver"

Thanks, I never hear of these, thanks!

[Gyro]

I suspect that, given the high thermal resistance of the case, any minor difference in thermal resistance of exotic heat transfer compounds isn't going to make any significant difference.

I'd stick with bog standard heatsink compound, maybe even superglue if the mating surfaces are in close flat contact (and secure them that way), Datron used to use it all the time to maintain matched components in close thermal contact in their instruments.

The most effective thing you can do is maximise the area of copper attached to the center pin, that's the one the die is attached to.