Insulating hardware, esp.washers

Roight, I was looking at the nylon ones. Silly me.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
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hobbs at electrooptical dot net 
http://electrooptical.net

It's a family thing. When I was working with Ford, their primary electrical engineer was the _son_ of the chief engineer for Henry Ford #1 ;-) ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
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| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
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I love to cook with wine.     Sometimes I even put it in the food.

On Sun, 22 Dec 2013 10:45:55 -0700, Jim Thompson Gave us:

Who, even you should remember, was a Nazi.

Nice ASCII!

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There are application notes by many of the Semiconductor manufacturers where they describe mounting arrangements that can be used with their devices. These include the Mica and Silicone based Insulations washers and insulated sleeves and collars for the mechanical fixings.

--
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On Saturday, December 21, 2013 1:34:12 PM UTC-5, snipped-for-privacy@yahoo.com wrote :

Hi James, Nice art work! So are we talking about the washer between the b ack side nut and the heatsink? (not shown in drawing) How about an anodize d aluminum washer? There's a washer company up in Idaho that has all sorts of options. (Do you do any prep to the to-220 surface so it doesn't scrat ch the anodization*? What about where the screw goes through the hole in t he heat sink?)

Re: nylon and crumble at ~80C.. have you seen this? (Does your device run

24/7?) I've used teflon shoulder washers for ~120C heater operation.. and nylon at lower temps.

George H.

*I've had issues with burrs left on a threaded hole punching through sil pa ds and shorting the to-220. I don't know if the same thing can happen with hard anodization.

Thanks Michael.

Cheers,

James

I vaguely remember these from many years ago...

...Jim Thompson

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| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142   Skype: Contacts Only  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.

It's been decades since I read that, and I needed the reminders. (I hardly do anything that needs heatsinking any more; I'm always trying to use all the energy and waste none. Heat = waste.)

It's the first published reference I've seen that recommends anodize on Al (as I'm doing here) as electrical isolation for low-voltage circuits.

I also had mistaken "wavy" washers for Bellville--that was good to learn too.

Thanks.

James Arthur

Wavy washers are functionally about the same as Bellevilles, but they won't gouge surfaces like Bellevilles and split rings will.

Handy--I passed on some, thinking they wouldn't be stiff enough.

Thanks.

James

I was mostly wondering what people do between the bolt and the semiconductor--sorry I didn't make that very clear. I saw the various offerings at DigiKey, but some of them looked cheesy.

I didn't prep them. Trapping grit would be my main concern, but even that shouldn't make much difference as long as the grit's non-conductive.

That depends. If the screw's not touching the TO-220, it doesn't matter.

I've seen old nylon, yes, yellow-brown, and brittle.

It won't run continuously, and in normal operation it shouldn't even get hot. But, abused, it will, and the customer's hammering the heck out of it.

So, I'm trying to protect the semis under fault conditions.

It already has instantaneous current limiting with a limit inversely proportional to switch temperature. That and the heat sinks were really just meant so the unit would survive long enough to take out its input fuse.

I might make that thermal overload cutoff a lot more aggressive. Or possibly not--blowing sacks of fuses might get old, and enforce a certain amount of discipline.

Per John, Teflon cold-flows. Nylon would probably work here. As it is I'm using Kapton, 'cause that was handy locally, intruding into the hole to keep the bolt clear of the TO-220 tab.

Removing burrs is essential--burrs are NOT allowed. Having done that, the Al2O3 works great--no problems at all.

Cheers,

James Arthur

They come in a wide range of stiffnesses.

One check always worth doing when you have assembled everything is an insulation integrity check to ensure what should be insulated remains insulated.

--
******************************************************************** 
Paul E. Bennett IEng MIET..... 
Forth based HIDECS Consultancy............. 
Mob: +44 (0)7811-639972 
Tel: +44 (0)1235-510979 
Going Forth Safely ..... EBA. www.electric-boat-association.org.uk.. 
********************************************************************

and can be stacked in "parallel" or "serial"

-Lasse

A new material for my list, cool. I was going to recommend diallyl phthalate for the job, i have used it enough at temperatures as high as

125C for years in a test lab. No problems.

?-)

On Fri, 27 Dec 2013 20:02:28 -0800, John Larkin Gave us:

That's what *she* said.

Whatever turns you on.

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