Mica Insulators

[glen65]

Hello,
Just looking for an opinion from others as to which
would be the best course of action. I have looked all over the place
for mica insulators for TO127 devices and been unsuccessful. However I have some new mica insulators I believe are for a TO3P case transistors. Based on the pics below would they be safe to use on these TO127 case devices?

An externally hosted image should be here but it was not working when we last tested it.

Here is one I modified so that it would cover the entire back of the device.
Would this be a better way to go if I were to use them?

An externally hosted image should be here but it was not working when we last tested it.

Thanks.

 

[Netlist]

Nice modification but I would prefer the original.
Suppose you drill the whole one little millimeter lower and the mica is accidentally placed too high...
The first picture covers the risky area very well.
Just make sure to always measure for shorts between heat sink and body of an insulated transistor before applying current.

/Hugo

 

[steenoe]

Dont cut them to size, they fit good enough. What you often can do with Mica is to actually split them with a sharp scalpel! More often than not they are too thick. Being the material it is, you can easily split them in half or even more some times. Just go ahead and try it, its easier than one should think. The thinner the better, regarding heat-transfer.

Steen

 

[anatech]

Hi glen65,
I agree with Hugo 100%. Use them in their stock form.

Maintaining surface flatness may be difficult if you split the mica insulators to make two thinner ones.

-Chris

 

[steenoe]

Maintaining surface flatness may be difficult if you split the mica insulators to make two thinner ones.

Nope!! They wont be more uneven when split. I dont mean to start an arguement, but Mica's are no flatter if not split!
Mica's are allways a bit bumpy Thats what you got Thermal grease for.

Steen (used to build Class A amps with heavy current draw )

 

[glen65]

Thanks for the response,

I was just a little concerned that not having the insulator
extending completely to the bottom of the device might
result in a lack of heat transfer.