inexpensive TO-220 mounting hardware?

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grant fair
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inexpensive TO-220 mounting hardware?

Post by grant fair » Fri Feb 28, 2003 9:56 am

Does anyone know of an inexpensive source of TO-220 mounting hardware? (This includes mica or plastic insulating outline, nut and bolt, and plastic insert to isolate the bolt from the transistor case). The best price I have found so far is 5 for $4.00 Jameco).<p>Grant
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Edd
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Re: inexpensive TO-220 mounting hardware?

Post by Edd » Fri Feb 28, 2003 1:28 pm

Grant:
I have a stack of TO-220 mica insul as well as a string of the hard to get items,e.g…..the insulative shoulder washers. As well, a large sheet of the amber/orange mylar sheeting with a good thermal gradient so commonly used by NASA and the Mil nowadays.. This you could custom cut to any casing configuration required. Typically the hardware requirement is 4/40 in the US, but you might be using metric. I can easily gratis you a dozen copies if U get your own screw hardware. But U probably will need to test a shoulder washer’s ID. Hit me at the atti with your mail addee if interested….also how are U fixed for beryllium oxide ??<p>73's de Edd
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grant fair
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Re: inexpensive TO-220 mounting hardware?

Post by grant fair » Fri Feb 28, 2003 2:01 pm

Edd- many thanks - Grant
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Re: inexpensive TO-220 mounting hardware?

Post by gadgeteer » Fri Mar 07, 2003 9:40 pm

Can you use a TO-126 part? It has the plastic screw-hole, no need for a shoulder washer. Also, most any thin insulater works---even polyester or polyethylene. Just use the white grease.<p>If insultation isn't critical, I've had good results with a bit of SUPERGLUE (no grease)---it conducts heat fairly well, and almost always destroys the electrical conduction between the metal surfaces as the glue polymerizes. (It's nice if the two surfaces have similar coefficients of expansion.) Just try one and see if it works. Do a resistance check between the heatsink and your transistor. No screw needed. It naturally forms a thin film of acrylic plastic. (I wouldn't use this if it uses high voltage, or line voltage, and possibility of a shock exists) Preform your parts so that the component is not pulling on your heatsink, rough up both surfaces with fine sandpaper...

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Re: inexpensive TO-220 mounting hardware?

Post by grant fair » Sat Mar 08, 2003 10:42 am

I have TO220 transistors purchased, and finding the TO126 equivalents would be unlikely (these are garden variety switching transistors MJ3055 and MJ2955).<p>The superglue idea is a neat tip, though. Thanks.<p>Grant
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Re: inexpensive TO-220 mounting hardware?

Post by rshayes » Sun Mar 09, 2003 6:37 am

Two points about Superglue:<p>It is very hard to pull the joint apart, but it is much easier to shear it. It you need to get the part loose, tap it sideways rather than pulling it. This works both ways. Arrange the part so that the joint is not subjected to shear stress or it may break loose.<p>It bonds most materials well, except for a few types of plastics. It bonds human skin even better. If a drop squeezes out of the joint and you press your finger down on it, you will need some time to get your finger loose and you may loose a layer of skin doing it. Be careful.

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Re: inexpensive TO-220 mounting hardware?

Post by grant fair » Sun Mar 09, 2003 10:10 am

Super glue on skin can be dissolved with acetone (acetone is also the main ingredient in nail polish remover).<p>Grant
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Re: inexpensive TO-220 mounting hardware?

Post by chessman » Sun Mar 09, 2003 4:51 pm

Or Ketone, or any other abrasive cleaner ;)

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Joseph
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Re: inexpensive TO-220 mounting hardware?

Post by Joseph » Mon Mar 10, 2003 12:34 am

Or the oil from orange peels, which I believe contains the active ingredient d-limonene.<p>I have used electrical tape for transistors which do not get very hot. You have to be aware that excessive heat can cause the tape to melt and let the metal tab of the device short out against the heatsink. I do not use screws to fasten TO-220 or any other plastic power semiconductors to heatsinks anymore, but use springs which I obtain from clothes pins.<p>I had not thought of using plasic films like polyester but now like the idea of trying out some of the big roll of mylar film I obtained off of eBay.<p>[ March 10, 2003: Message edited by: Joseph Meisenhelder ]</p>

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Re: inexpensive TO-220 mounting hardware?

Post by chessman » Mon Mar 10, 2003 2:41 pm

A lot of heat-sink/hardware companies offer free samples if you ask them, just don't make up false information or abuse it, because that will only contribute to the poor economy.

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Re: inexpensive TO-220 mounting hardware?

Post by rshayes » Mon Mar 10, 2003 7:13 pm

I would still be very careful with Superglue. It might be diffult to open the bottle of nail polish remover (acetone, MEK, limon oil, etc.) with your left hand while you have a heatsink glued to your right thumb.<p>Years ago, one of my coworkers told me of his experience with Eastman 910 (the original version of Superglue). He had been using it to assemble prototype magnetic recording heads, and was applying it with a toothpick. He got confused, put the wrong end of the toothpick between his teeth, and bit down gently to hold it while he used both hands. It took him three hours to get his teeth separated again.

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Re: inexpensive TO-220 mounting hardware?

Post by gadgeteer » Tue Mar 11, 2003 1:07 am

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>while you have a heatsink glued to your right thumb.<hr></blockquote>Ha ha ha! :D <p>I have a colleague who is older---and worked with probably that exact stuff. He was talking to an insufferable co-worker, who refused to believe the strength of the new glue. My friend demonstrated it for him---placed a tiny drop on his finger, and said: "Now touch your nose..." (I'm amazed no one got fired over that...)<p>Loctite makes a line of "TAK-PAK"---a superglue system, with the main adhesive thick (between GEL and common liquid); it has a catalyst, solvent based; it will totally harden the glue in about 3 seconds. (They recommend brushing the watery catalyst on one surface, and a drop of glue on the other---then assemble.) The catalyst does work on regular superglue, but unless you blow on it (evaporating the catalyst) it reacts so quickly, the glue foams and smokes.<p>I would absolutely roughen the surfaces. I discovered that "Armor-Etch" on my windshield, producing a very finely frosted glass, ends the repetitive purchasing of "REAR-VIEW-MIRROR-ADHESIVE". Glue bonds to a rough surface much better---haven't replaced the mirror since...<p>You could still be bitten by the "differential expansion" problem---being acrylic, the hardened glue is brittle; a copper transistor tab does not expand at the same rate as an aluminum heatsink. So for high thermal stress, I would expect it to shear...<p>RE using polyester films---alot of companies offer them made out of just that (using the predicted lithium grease). But there's still the problem of keeping the system below the melting point of the film; which, if it DOES get that hot, you really need a bigger heat sink anyway.<p>...or a fan. NO one can have too many fans. ;)

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