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-   -   Thermal management (http://www.diyaudio.com/forums/solid-state/123057-thermal-management.html)

Linear Purpose 14th May 2008 03:19 PM

Thermal management
 
In solid sate amplifier thermal management is a critical point for performance an reliability.

Nevertheless it is often an under estimated part of the design.

For example there is still people using MICA insulators (which are completely obsolete) between transitors and dissipator ...

There is certainly lots of ideas to share on that subject !

CBS240 14th May 2008 05:53 PM

Quote:

...For example there is still people using MICA insulators (which are completely obsolete) between transitors and dissipator ...
Mica is obsolete:confused: My mica insulators work quite well if you mount them properly. There may be material out there that works a little better but when you factor in the price... :dodgy:
You just have to deal with the heatsink grease.:xeye:

AndrewT 14th May 2008 06:13 PM

Mica insulators conduct heat better than many of the new insulators that are marketed.

The main purpose and reason for these "dry" insulators is to save assembly time.

whoandcar 14th May 2008 06:13 PM

Quote:

Originally posted by CBS240

"It is not a disgrace to fail. Failing is one of the greatest arts in the world."

I usually fail with complete succes...

wg_ski 14th May 2008 06:29 PM

By far the best way is to mount the transistors directly to the heatsink, but that creates other headaches. You either have to run the sinks electrically hot or limit yourself to a grounded collector topology.

Dr_EM 14th May 2008 06:36 PM

The mechanical mount is important too. Using Hex head bolts will help and ideally a clamp can be used (again tightened with hex type bolts). For insulators I tend to use Sil-Pads, seem to work pretty well (had a heatsink untouchably hot in one test setup but the chips never cut out or had problems).

EWorkshop1708 14th May 2008 11:19 PM

I use wide clear tape on my heatsinks, so far success and no issues.

I stick the tape on the heatsink, making sure of no air pockets, and grease the transistors, and stick them to the tape, and clamp them down. The thermal performance is good.

I'm not worried about melting the tape, because if I run it that hot, which I doubt, then I have more problems to worry about than the tape anyway.

MJL21193 14th May 2008 11:28 PM

My first time I was impatient to try my creation and I used thermal grease and paper. Ordinary white printer paper cut to size. Amp had 56V rails, and it worked fine.

I later changed to mica to be on the safe side.

jrockhead 15th May 2008 12:04 AM

Re: Thermal management
 
For example there is still people using MICA insulators (which are completely obsolete) between transistors and dissipator ...

Obsolete??? I would not use anything else. As others have stated and I verified for myself the other types have worse thermal performance than mica and good thermal grease.

EWorkshop1708 15th May 2008 12:24 AM

2 Attachment(s)
Quote:

Originally posted by MJL21193
My first time I was impatient to try my creation and I used thermal grease and paper. Ordinary white printer paper cut to size. Amp had 56V rails, and it worked fine.

I later changed to mica to be on the safe side.

Wow, you used paper??? :bigeyes:

At least you greased it though. That thermal grease is great stuff.

I saw a car amp one time someone tried to fix, and they put pieces of fairly thick paperboard behind the transistors with no grease :yikes:

Here's a heatsink I just done with clear tape. You can hardly see the tape with the naked eye


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