[Amps] Heatsinks for SSPAs

[Paul Decker]

It sounds great in theory and maybe in practice too.  How do you mount the transistors to the chassis without a through hole into the water jacket?

If you look at the NXP BFL578XR demo board, they are using a 3/8" solid copper heat spreader which then has a water inlet and outlet for cooling the heat spreader.  Similar idea except the transistor mounting does not penetrate the water jacket and there is no chance it will leak due to thermal expansion and contraction.

A second note you might find interesting is that many of the parts are supplied as solder mount and are mounted directly to the copper heat spreader via a solder mask.  That may be one way to mount to the chassis bottom, but I'm not so sure it's easy to solder to Aluminum or what two very dissimilar metals will do when bonded.

More food for thought.

Paul, kg7hf




Date: Fri, 01 Mar 2013 14:14:30 -0800
From: Bill Turner 
To: Amps 
Subject: Re: [Amps] Heatsinks for SSPAs - Newbie Questions and UK
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Just thinking about heatsinks for homebrew SS rigs.  Here's an idea, maybe
a bit in-elegant but I bet it would work like a champ.

Use a conventional aluminum chassis and mount the transistors on the bottom
side flip it over and fill it with water. Don't laugh. Just put the bottom
(now the top) cover on it and seal everything up with RTV silicone.  Put
some hose fittings on it, one for inlet and one for outlet . I'll leave
that part up to your imagination. Hint: thermal switch with an external
valve for the water. 

You want the transistors on the bottom because heat rises. 

Haven't tried it myself but I bet it would dissipate anything you could
throw at it and no fan noise either. 

Thoughts?

Bill, W6WRT