Clamp Fastening a Non-Isolated TO-220

You can't just use nylon screws?

A TO220 is designed to screw mount - there are plenty of insulated screw mount options. If you don't want a screw mount, a "binder clip" (paperclip for thick piles of paper) would appear to do what you want if you are close to the edge of the aluminum and can hang the clip over the edge (or if you cut an access hole for the clamp in the aluminum) though you'll need an extra hunk of mica (or other insulator) if you want to keep it insulated.

A hunk of spring-steel screwed to the aluminum and bent appropriately could also do it, but a direct screw is simpler, unless you are building a test fixture where you need to cycle parts through at high speed, and in that case a De-Sta-Co would be a better choice.

Over large temperature swings nylon screws will cold flow and loosen up. Even if you lock-tight it, you'll just lock the screw in the heat sink, but not prevent the shank from lengthening over time.

The folks I know who do packaging for reliability over a large temperature range use a metal one-size-down screw (#4 in the case of the TO-220) and a nylon shoulder washer. It works quite well.

I vaguely recall seeing clips as you describe to hold a TO-220 or similar to a heatsink, but I'm not so sure about isolation. Have you tried the Aavid website, or other heat sink manufacturers? You may have better luck searching on "clip" rather than "clamp", although I'd try both if I found a good site.

Mouser stocks the Aavid "Max Clip" series of mounting clips (clamps); Digikey lists them in their online catalog, but are not stocked.

Cheers!

You may be looking for Kunze products, distributed through Wurth, RS and other suppliers. There are quite a few similar parts out there, and many companies make their own.

TSC209 or TSC405

Kunze website

Illustrations show them loading from the top, but there's no reason why they can't load from the side. Poor real estate use, if so.

RL

I have just the thing you need, but your "Christian" thread was so obnoxious that I'm not going to help.

John

Awwwwwwh! Did Ms Polly Prissy Pants get her feelings hurt ?:-)

I kill-filed that thread long ago with a "expire on no activity". It's still going strong, so I suspect that it's rampant with nutcases. However I won't be looking to see who it is.

...Jim Thompson

So you help him. ;)

Cheers

Phil Hobbs

Uhh..I ran out nylon nuts and bolts.. :(

afaik, Digikey doesn't stock nylon plastic nuts and bolts. I was wondering if Digikey stocked alternative hardware to clamp down a TO-220 package to the chasis.

D from BC myrealaddress(at)comic(dot)com BC, Canada Posted to usenet sci.electronics.design

That would be the Christian thing to do.

John

Do they squish is overtorqued?

I'll keep an lookout for those..

D from BC myrealaddress(at)comic(dot)com BC, Canada Posted to usenet sci.electronics.design

mmmm spring steel..

-----+ _\\/__ | | | | ---- +===( )===

I might hack up a binder clip..

D from BC myrealaddress(at)comic(dot)com BC, Canada Posted to usenet sci.electronics.design

AFAIK they _do_ stock shoulder washers. You'll have to do a bit of digging to find all the critical dimensions -- putting a #4 screw into a TO-220 hole is a bit tight, so the walls of the small-diameter part are pretty thin.

You have to _really_ overtorque them. Basically the critical part for cold flowing is shorter and has more surface area, so it gives a more favorable characteristic -- at least as far as I understand the issue.

Is was picturing the clamp forcing down on the plastic body portion of the TO-220 case not the metal tab. I'm using a mica isolator for isolation.

I'm imagining something like this to clamp down a TO-220.

I'll try clip and clamp keywords.

D from BC myrealaddress(at)comic(dot)com BC, Canada Posted to usenet sci.electronics.design

That's it .. Diagram M or L Alternatively S or T (as per Tims shoulder washer post)

Thanks

btw.. How did you find that page?

D from BC myrealaddress(at)comic(dot)com BC, Canada Posted to usenet sci.electronics.design

Cool.. I do have use for a clip for two TO-220 cases..

D from BC myrealaddress(at)comic(dot)com BC, Canada Posted to usenet sci.electronics.design