Copper Heatsinks

[laatsch55]

Would you need a fan on a WOPL 1000 at 4ohms load if you had copper heatsinks the same dimensions as the stock ones?

 

[Gepetto]

Copper heatsinks will help keep semiconductor heat down Lee because copper conducts heat and electrical current better than aluminum but difficult to say without more rigorous analysis whether the improved conductivity benefit is enough to avoid forced air cooling under your conditions. Putting a black oxide finish on the copper will help the copper radiate into the air more efficiently but still don't know whether it will be enough. The copper will help keep all portions of the heatsink at closer to the same temperature than the aluminum (in other words, the aluminum will exhibit a larger temperature gradient from transistor to tips of the heat sink fins)

 

[Rex Everything]

Copper heatsinks will help keep semiconductor heat down Lee because copper conducts heat and electrical current better than aluminum but difficult to say without more rigorous analysis whether the improved conductivity benefit is enough to avoid forced air cooling under your conditions. Putting a black oxide finish on the copper will help the copper radiate into the air more efficiently but still don't know whether it will be enough. The copper will help keep all portions of the heatsink at closer to the same temperature than the aluminum (in other words, the aluminum will exhibit a larger temperature gradient from transistor to tips of the heat sink fins)

My thoughts exactly....... NOT!

 

[laatsch55]

Well, Ed and I had talked about this a couple months ago. The thermal conductivity of copper is 5 times that of aluminum (I think) IIRC. So it's not that I have to have it go 4 ohms at max with no fans, this is mainly an excuse to build Ed a set of heatsinks for his 700B that he has noi heatsinks for. I mean if a fellas gonna build some , might as well be out of the good stuff. Ordered the copper today as a matter of fact after having a long talk with one of our machinists. I am going to take separate side pieces and silver solder them to the strap that will be milled for the TO-3's to mount to. Silver solder now comes in strips, so you put the strips between the two pieces and apply local heat to the joint. Pretty cool actually. I'm hoping Ed doesn't run his amps past the melting point of silver solder.

 

[laatsch55]

I will run some tests after making them comparing how the aluminum and copper behave differently if i can get the controls in place to make it repeatable and valid.

 

[Rex Everything]

This is getting very interesting. Of course you'll be documenting with pictures as you go....?

 

[laatsch55]

This is getting very interesting. Of course you'll be documenting with pictures as you go....?

Well yeah, post and pic whore that I am.

 

[speakerman1]

Well, Ed and I had talked about this a couple months ago. The thermal conductivity of copper is 5 times that of aluminum (I think) IIRC. So it's not that I have to have it go 4 ohms at max with no fans, this is mainly an excuse to build Ed a set of heatsinks for his 700B that he has noi heatsinks for. I mean if a fellas gonna build some , might as well be out of the good stuff. Ordered the copper today as a matter of fact after having a long talk with one of our machinists. I am going to take separate side pieces and silver solder them to the strap that will be milled for the TO-3's to mount to. Silver solder now comes in strips, so you put the strips between the two pieces and apply local heat to the joint. Pretty cool actually. I'm hoping Ed doesn't run his amps past the melting point of silver solder.

What % Silver? You will have to figure out how to protect the copper from corrosion yet not mess with the heat dissipation. LMBO Can't believe I wrote that.

Larry

 

[laatsch55]

Why can't you beliweve you wrote that? Valid points Larrt. I think Joe may have nailed it with the black oxide finish statement. What percent silver in the silver solder??

 

[laatsch55]

Don't know Larrt, but 10 pieces, 36 inches long and 1/8 inch wide and .015 thick cost me 149.00
So I'm thinkin pretty high. This isn't like your regular silver and tin and lead combo, thia is what they use to solder carbide tips on cutting tools, good stuff.

 

[speakerman1]

Don't know Larrt, but 10 pieces, 36 inches long and 1/8 inch wide and .015 thick cost me 149.00
So I'm thinkin pretty high. This isn't like your regular silver and tin and lead combo, thia is what they use to solder carbide tips on cutting tools, good stuff.

You may have a hard time getting it to flow.

Larry

 

[laatsch55]

We don't seem to soldering carbide. It is pre-fluxed and clamped between the 2 pieces. There's enough temp difference between the copper and the solder that it shouldn't be a problem.

 

[mlucitt]

I might consider a mechanical bond. If the surfaces were polished smooth or lapped on a glass plate with pressure-sensitive abrasive (PSA), and then bolted together; I think the heat transfer coefficient might be better than copper - silver solder - copper. The bonus is you could unbolt it and try different configurations. De-soldering is always a messy proposition. You could even use some thermal heat sink compound, I hear there are folks out in Wyoming that put it under them big transistors that nobody uses anymore...

 

[laatsch55]

That was my first option Mark. But at 1/8 inch thick, drilling and tapping can be a pain in the ass. It may be that that is what I wind up doing. But i'll try soldering first.

 

[speakerman1]

We don't seem to soldering carbide. It is pre-fluxed and clamped between the 2 pieces. There's enough temp difference between the copper and the solder that it shouldn't be a problem.

Put my tinfoil hat on. LOL Never mind.

Larry

 

[Fairchild]

We don't seem to soldering carbide. It is pre-fluxed and clamped between the 2 pieces. There's enough temp difference between the copper and the solder that it shouldn't be a problem.

Put my tinfoil hat on. LOL Never mind.

Larry

If you can't find yours, you can borrow mine.

Jim

 

[laatsch55]

Gotta keep the aliens from tapping in.

 

[Skratch]

What about water cooled??????

 

[Fairchild]

I never thought of that, the foil will get hot and that could create digital and electrical issues.

Hmmmm

Jim

 

[Fairchild]

Keep an eye out. I think they are...........gray.

Jim