[Nixie]

There's no screw hole, nor even much of a tab sticking out in this package. How do I attach such devices to a heatsink?

 

[Jazper]

my initial thought is thermal glue but it looks like you're sposed to solder the back to the groundplane on a circuit board (don't quote me on that)

 

[tangent]

Quote:

it looks like you're sposed to solder the back to the groundplane

Maybe...but then why is there also the DDPAK package? That's much better suited for SMT power semis.

 

[Nixie]

I wonder if it could be clamped to a heatsink.

 

[beerguy0]

Quote:

Originally Posted by Nixie There's no screw hole, nor even much of a tab sticking out in this package. How do I attach such devices to a heatsink?

What is the specific device you are looking at? I found a Fairchild device (MOSFET) that uses this package. This is kind of an odd package, and I don't recall ever having used one. The leads are thru-hole, but the body looks like a TO-263, which is an SMT version of a TO-220. Just looking at the device, my guess is that you would clamp the device body to the heatsink, using a sil-pad for isolation and heat transfer. There may be clips available for this purpose.

I found this about the TO-262 package:

TO-262 Package

This low-profile through-hole assembly package option for the TOPSwitch product line of high power monolithic switcher ICs ranges in power up to 290W. The TO-262 package can be used for applications unable to accommodate the TO-220 package due to height restrictions above the p. c. board.
Power Integrations Inc., San Jose, Calif.

Based on that, it looks like a smaller version of a TO-220. The Fairchild device is available in TO-220, which is easier to work with for the DIY'er. Without knowing what device you have, I can't be much more specific.

Hope this helps.

Cheers,

bg

 

[Nixie]

I was going to place my order at Digikey, as it ships to my place in two days, but it only has the IRLZ34NL in small quantities in TO-262 and D2PAK versions.

I suppose I could solder it to a copper heatsink...

 

[mono]

It is meant for surface mount (obviously soldered). If necessary and there isn't a lot of heat to dissipate you could get away with thermal epoxy. Some types of heatsinks implement a spring-clip against the epoxy casing and could also be used, though I don't have a source for any such 'sinks. Likewise a clamp might be possible.

Soldering to a heatsink is a bit more difficult to do than write, since it is obviously designed to 'sink away the heat.

 

[Nixie]

I'm thinking cutting out a pad of the 1 mm copper sheet I have, soldering to it, and then attaching that to a heatsink.

 

[beerguy0]

Quote:

Originally Posted by Nixie I'm thinking cutting out a pad of the 1 mm copper sheet I have, soldering to it, and then attaching that to a heatsink.

That might work, but there will be an additional thermal barrier. The Cu pad would have to be extremely flat to be really useful. If the Pdiss isn't too high it would probably work.

I found this heatsink intended for TO-220, but it would likely work for the TO-262, since the packages are very similar.

http://www.thermaflo.com/stamp.shtml

The device is held to the heatsink with a clip. I think this is probably the intended mounting method for this type of device.

 

[Emon]

Quote:

Originally Posted by mono Soldering to a heatsink is a bit more difficult to do than write, since it is obviously designed to 'sink away the heat.

It would actually be quite easy with the proper equipment...You'll need to heat up the heatsink to solder melting temp, tin the contact area and make sure the contact area on the TO-262 device. Then squish em together.

Unfortunately there's the problem that the heatsink will transfer most of its heat back into the device, probably frying it. So you'd probably want to clamp the device to the heatsink and stick the bottom half or the assembly or the hole thing in some water to cool it off.

You can solder to aluminum with the proper tin/zinc (or is it lead/zinc?) solder or use a technique like this.

But you're probably much better off with thermal epoxy. SVC was one of the cheaper stores to carry it when I bought my tube a year or two ago - most places charge $15 and shipping, this should cost around $12 shipped, if that. It's got pretty good thermal conductivity - 7.5 w/m*K. If I recall correctly, water is 1, air is about 0.0022, steel about 80, brass around 110, aluminum about 260, and copper about 400 - to put that in perspective for you. I believe it conducts about as well, perhaps better, as silicone or zinc oxide white thermal paste, but it's been a while, so I don't remember. Should be more than adequate for your needs...but be warned...it'll never come off!

 

[Emon]

Quote:

Originally Posted by beerguy0 That might work, but there will be an additional thermal barrier. The Cu pad would have to be extremely flat to be really useful.

Oh comon. You're cooling a single IC, not a Cray. Screw it down tight and it'll be fine.

 

[Nixie]

I've used the oil method to solder to aluminum before. Strangely, silver solder (i.e. Caras, etc.) works better in that application than common solder. Cooking oil with a bit of flux worked better than motor/mineral oil. Once the oil is on, the aluminum surface should be scratched to remove the oxide coating.

Actually, I just found a substitute at Digikey that's close enough and comes in TO-220, so I guess this thread has become purely theoretical...for now.