Copper Heatsinks

[Gepetto]

With a name like Dick Blick, this one belongs in the Cave...or in Congress.

 

[mlucitt]

Yeah, funny

 

[laatsch55]

Lee,
You could try this stuff:

http://www.dickblick.com/products/liver ... ng.com+Inc" onclick="window.open(this.href);return false;.

I believe that was in the Alchemy Dept.

 

[speakerman1]

How hot will they get?

Larry

 

[laatsch55]

OK, the question was raised about the potential difference in a soldered and mechanical connection for heat transfer properties. got an experiment ready to go.
Identical copper pieces were joined, one with a bolt and heat transfer grease, the other with some liquid flux and Kester "44". Thermometers were clamped identically to the end of the attached piece. A common heat point on the other end was made wide enough for the heat gun. I will run the heat gun and Jani the camera. The test jig is suspended from the ceiling with #16 tie wire.

The first pic, checking the drllled backwall straps against the chassis pattern--------perfect.

 

[laatsch55]

Barely a degree difference. For a control I'll reverse the thermometers.

 

[laatsch55]

The one degree difference followed the thermometer.

 

[laatsch55]

Had to get a propane torch out to get the temp above 120 degrees.

 

[NavLinear]

Cool experiment. Seems that the attachment method does not make much of a difference regarding heat transfer.

I'm curious about the photo of the back of the amp. Is the entire heat sink made of copper with the attachment area for the transistors untreated? It sure does look nice.

As always you have some fun and interesting stuff going on - thanks for sharing.

 

[laatsch55]

Dennis those are just the straps that the outputs would mount to. The 6" X 6" fins still have to be silver soldered on. I was checking the accuracy of the drilled holes. After that I polished the mounting surfaces for the maximum contact area for optimul heat transfer. Stopped at 1200 grit wet/dry. I think I could shave using them as mirrors. I was about to go to the shop and solder these puppies up (only 3 blocks away). Then some poor 400 is in for some torturous times.

 

[Skratch]

Lee, Now that your that close you should lap them as any good German would do.

 

[laatsch55]

Yeppers, came back to the house to do just that and practice with the silver solder and flux on some scrap.

 

[Skratch]

Lee, Once you finish this amp what are you going to use it for ? A frequency welder ?

 

[mlucitt]

"Welded with Shpongle" That is a tagline you have not seen before...

 

[laatsch55]

Mark and Mark, these will be going on the cherry I got the other day, with the XPL-910's. Just in general torture some sp[eakers......ands neighbors..././......

 

[laatsch55]

Heatsinks are done. I will not silver solder a set of these again. I have talked to a couple of our machinists and they are going to mill out a press mold so I can lay a sheet of copper, cut to the proper dimensions and then just press the plate into the "U" shaped mold and--Voila. Instant heatsink. They turned out pretty well. Now maybe we can get some hard data.

 

[speakerman1]

What was hard about soldering? Know anyone with a metal brake. Copper should be easy to bend after you get the 1st one done. Just watch your bend radius. Even then it shouldn't be a problem.

Larry

 

[laatsch55]

I don't know of a break that can bend 6" "U" only 1-1/2 inch apart. I took some scrap copper to the shop and in our small break it bends beautifully. Nice tight radius too.
Copper takes heat so fast Larrt that by the time you have the base metal hot enough to flow the solder has cooked out most of the goodie that lets it flow, and the flux was long gone before that.
So I got a piece of 1/2 inch by 6 inch by 2 foot A-105 strap and got it red hot , then clamped the fins to it , and slid the strap in between the fins and soldered them.

 

[speakerman1]

So it was kinda hard to flow? I think we had a small hand brake. I can't remember that far back. With the greater heat dissipation rate you can go shorter if you want. I think.Therefore I am. I liked when we got to go in the machine shop to make a part. LOL It would take all day heat treating it and everything. Even though we had the right stock. LOL By the time we were done. We would have made a tool to spec. Not just something that would work. LOL Have used that many times. Screw driver in rig pin holes. I had my own pins I have collected over years. Craftsman screwdriver Phillips #2 is .250 in diameter. Never mind. Gotta go. LOL

Larry

 

[speakerman1]

I think our last bend was a half bend and we walked it the rest of the way. Aren't you glad it isn't titanium. LOL

Larry