Belleville washers and power transistors 1

[chiefbrody]

Does anybody have any experience with securing power transistors to heatsinks using belleville washers. I am interested in TO-220, TO-247 packages. Any info is appreciated.

 

[IRstuff]

Why a belleville?

I would imagine that the force required make solid thermal contact is beyond the compression from the spring, or you'd wind up with one so stiff that you might as well have just bolted it together directly.

TTFN

 

[chiefbrody]

I have heard that the spring action helps thermal cycling and expansion, and keeps a steady force to make a solid thermal contact. Spring clips are available from other manufacturers such as AAvid/Thermalloy, but I would like to accomplish the same by using a screw and washer. Are there certain forces required for optimum thermal contact?

 

[mech53]

Interface thermal resistance is one part of the thermal path that is often given too little attention.

The Belleville washer will also compensate for differences in interface pressure caused by cold flow of an (electrically) insulating washer, if one is being used. In high shock or vibration environments, it also plays a big
role in keeping a consistent pressure on the interface.

Check out this article:

http://www.electronics-cooling.com/Resources/EC_Articles/MAY97/article3.htm

which gives a more-than-you-wanted-to-know account of thermal interfaces.

 

[electricuwe]

Look at Lcube's post in the following thread for more information on Belleville washers:

thread404-39941