How to hook up a heat sink?

Hi,

When testing out a voltage regulator, I see that it gets very hot. Heat sinks are new to me, and I am not sure what I need or how to hook it up.

Here is the regulator I am using:

http://www.st.com/stonline/books/pdf/docs/2145.pdf

I have the TO-92 version.

Any help or suggestions would be great!

Thanks.

Those aren't really designed to have heatsinks mounted to them; you may want to buy a larger regulator with a tab for bolting a heatsink on (TO-220 case, perhaps). Once you do that, you just need a boltable heatsink and some heatsink compound to go between.

For a TO-92 device, you might try to epoxy (I prefer 2-part JBWeld, personally - strongest stuff on the planet, I think - I have it holding together a backfire prevention valve on a 400ci V8 in my old Bronco, which is bolted directly to the exhaust manifold; I've also seen it used to hold together an aluminum blower on a large diesel engine for 20 years - so, if it can take that kind of temperature abuse, it will work good for a small TO-92 device!) a small piece of copper/brass/aluminium tubing over the device, and split the top 3-4 ways and spread the "fins". You can find such smaller tubing at hobby stores (they should carry a "pieces-n-parts" assortment bag of cutoffs that would work good; whole tubing can also be purchased). Be sure to have plenty of airflow.

:)

78XXs rule OK :slight_smile: , just bolt a lump of metal to the tab. In fact if 100ma is enough,and the input voltage isn’t excessive, it would probably be quite happy without a heatsink at all. Cheap too.

You can put a heatsink onto any package. They come in all shapes and sizes start at this product selector to see what is avaliable:- http://uk.farnell.com/jsp/search/browse.jsp?N=500006+1001235&Ntk=gensearch_001&Ntt=heatsink&Ntx=mode+matchallpartial

Basically you are just putting a piece of metal on the package to reduce the thermal resistance. This can be fixed by mechanical clamping or by thermal conducting glue. If you use mechanical clamping you can also heat sink compound, a sticky white goo to improve the thermal coupling between IC package and the metal. What is important is to maximize the surface are of the metal not the bulk, that is why the more efficient heasinks have lots of thin fins on them.

Grumpy_Mike:

I didn't see a TO-92 heatsink in that selector; do they actually make such a thing (I've never seen one; that doesn't mean they don't exist)?

:)

Here is one.... http://parts.digikey.com/1/parts/988402-heatsink-92-72-blk-575200b00000g.html

If you are interested in just ordering a few and don't want to pay too much in shipping, I don't mind stocking it in my store and sending you some via First class mail.

Jeff K (or anyone else) - how would one hook up that 92 heat sink?

Thanks for the feedback so far. I could switch to a 220 if needed now that I understand how heat sinks are intended to hook up to them, but this seems an interesting issue to follow through so I'll stick with the 92 for now and see what works.

it pretty much just clamps on the body

Interesting find, Jeff - thanks for posting that!