TO-3P vs. TO-247 insulators

vsr123 · 24th April 2003, 05:37 PM

Hi
I am trying to find mica insulators for a TO-3P package and am having a hard time finding any. On the other hand, insulators for TO-247 seem to be much easier to find -

1) What is the difference between these two packages, they seem almost identical in size to me.
2) does it matter if the insualtor I use is slightly bigger than the transistor base that I am trying to insulate from the heatsink? or should I cut it down to size?

thanks in advance
vsr

Nelson Pass · 24th April 2003, 06:53 PM

Keystone is a primary supplier for Micas. I think they
still have TO3s in the Digikey catalog, but I'm sure you
can find them if you look around.

JoeBob · 24th April 2003, 09:14 PM

It does not matter if the pad is larger than the transistor. Actually if the pad is a little smaller it won't matter either, because the metal center of the chip is the only part that will conduct the electricity, and the heat dissipated off the plastic of the FET is negligible (although some obviously does). So a slight difference in size won't hurt.

24th April 2003, 05:37 PM	#1
vsr123 diyAudio Member Join Date: Mar 2003 Location: california	TO-3P vs. TO-247 insulators Hi I am trying to find mica insulators for a TO-3P package and am having a hard time finding any. On the other hand, insulators for TO-247 seem to be much easier to find - 1) What is the difference between these two packages, they seem almost identical in size to me. 2) does it matter if the insualtor I use is slightly bigger than the transistor base that I am trying to insulate from the heatsink? or should I cut it down to size? thanks in advance vsr

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24th April 2003, 06:53 PM	#2
Nelson Pass The one and only Join Date: Mar 2001	Keystone is a primary supplier for Micas. I think they still have TO3s in the Digikey catalog, but I'm sure you can find them if you look around.

24th April 2003, 09:14 PM	#3
JoeBob diyAudio Member Join Date: Nov 2001 Location: Montreal, Canada	It does not matter if the pad is larger than the transistor. Actually if the pad is a little smaller it won't matter either, because the metal center of the chip is the only part that will conduct the electricity, and the heat dissipated off the plastic of the FET is negligible (although some obviously does). So a slight difference in size won't hurt.

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