Mica newb question... - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 6th March 2011, 07:30 PM   #1
diyAudio Member
 
Join Date: Jun 2010
Default Mica newb question...

Please excuse my ignorance, but I should be using a dab of heat transfer grease between both the mica and the case, and the mica and the transistor, correct?

Using this kit
4880MG Aavid Thermalloy Heatsinks

Should I put it between the case and the external sink as well?

Steel case and anodized sinks...
Standard Products Found

Thanks!

Last edited by monkeyevil; 6th March 2011 at 07:33 PM.
  Reply With Quote
Old 6th March 2011, 07:55 PM   #2
diyAudio Member
 
Join Date: Nov 2008
With the Thermasil or the Thermafilm a thermal compound should not be needed.
With mica you would smear a thin film of the compound on each side of the mica pad to aid heat transfer. E
  Reply With Quote
Old 6th March 2011, 08:54 PM   #3
BrianVG is offline BrianVG  Belgium
diyAudio Member
 
Join Date: Jun 2010
Location: Louvain
When you often heat the transistors and they go trough their 'thermal cycle' (ambient-operation-ambient temperatures)often, they will act as a bimetal with your heatsinks. It will create little gaps. After a while these gaps get bigger,so less heat is transferred and so on.
I use thermal paste which gets a bit fluid when it heats up=>fills gap

Anodized= isolated, so no need for mica if you use paste.
__________________
FET fanatic
  Reply With Quote
Old 6th March 2011, 09:51 PM   #4
jaycee is offline jaycee  United Kingdom
diyAudio Member
 
Join Date: Apr 2004
Location: Norwich, UK
4880MG is mica, so yes you need paste on both sides of the pad. BTW, 4880MG is TO-220 pads and your heatsinks are for TO-3 transistors.

Whether you should use paste between the case and the heatsink depends on whether the transistors are mounted on the heatsink, and then onto the case, or not.
  Reply With Quote
Old 6th March 2011, 09:53 PM   #5
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
If one wants to transfer heat quickly, then air must be excluded from all interfaces across which the heat needs to pass.
__________________
regards Andrew T.
  Reply With Quote
Old 6th March 2011, 10:14 PM   #6
HighTec is offline HighTec  Croatia
diyAudio Member
 
HighTec's Avatar
 
Join Date: Mar 2003
Location: Sibenik, Croatia
Speaking of which, I bought this tube of crappy thermal grease. It's ok but the problem is that it has a high viscosity and starts to melt at a rather low temperatures. Actually, the damn thing begins to seep and collect under the heatsink. So, guys, which thermal grease do you use? Can you recommend me some real stuff?

Edit: what about Dow Corning 340 thermal compound?

Last edited by HighTec; 6th March 2011 at 10:33 PM.
  Reply With Quote
Old 6th March 2011, 10:46 PM   #7
diyAudio Member
 
Join Date: Jun 2010
Quote:
Originally Posted by jaycee View Post
4880MG is mica, so yes you need paste on both sides of the pad. BTW, 4880MG is TO-220 pads and your heatsinks are for TO-3 transistors.

Whether you should use paste between the case and the heatsink depends on whether the transistors are mounted on the heatsink, and then onto the case, or not.
This is actually for a headphone hybrid (Starving Student) and my first forte into case design.

I have the transistors mounted to the underside of the case, and the sink mounted to the topside. So it goes transistor, mica, case, sink.

Not much heat is getting into the sinks currently, and I need to go back and introduce thermal paste.

Is it a poor design to assume the heat will transfer from the case into the sinks?

Click the image to open in full size.

Click the image to open in full size.

All finished.
Click the image to open in full size.
  Reply With Quote
Old 6th March 2011, 11:27 PM   #8
jaycee is offline jaycee  United Kingdom
diyAudio Member
 
Join Date: Apr 2004
Location: Norwich, UK
No that is fine, but yes you should have thermal paste between the heat sinks and the casing.

Are those transistors getting hot? If you can't keep your finger on them, then they're too hot. The case itself might be an adequate heat sink in itself. I couldn't say without seeing the design. You should have transistor, paste, mica, paste, case, paste, heatsink.

Looks nice BTW
  Reply With Quote
Old 6th March 2011, 11:28 PM   #9
diyAudio Member
 
Join Date: Nov 2008
Ah, Blue Beauty! E
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
newb question jorge1 PC Based 2 19th May 2010 09:14 PM
Major Newb Question Nexter Digital Source 0 1st April 2008 05:16 PM
Newb question bushroot Chip Amps 3 6th October 2006 05:31 PM
newb question v1d9uy Subwoofers 2 11th January 2006 11:53 PM
Very newb question jaws2421 Solid State 7 29th December 2005 05:46 PM


New To Site? Need Help?

All times are GMT. The time now is 04:14 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2