What is this copper thing?

Pulled out of a non functioning imac G4. I'm not sure what it's called but it was over a large black chip on the board. I scratched it and it is copper, non magnetic everywhere, i broke it to see the inside and it has strands off copper wire in it? Anyone have an idea?

Heat sink

Can I just throw it in with my copper? I'm wondering just because it is coated if it is a seperate category? Also, I have some copper wire coated with silver stuff from CRT monitors, does that still go with clean copper?

Yes I have, but was not sure what this was, I haven't seen one like this before. Also, I couldn't find the name for the coated copper, so I asked.

Huh, I wonder if thats what happened to this one, it wouldn't even power on at all. Thank you for that, it was from one of these. I agree it was weird, especially since it needs to be upside down to take apart. Would you happen to know what the metal dome inside of the egg shaped part is made of? It seems to heavy for aluminum but isn't magnetic, is it zinc or something?

That metal dome is the iMac's Faraday cage, so it has to contain something conductive. I don't know what it is, though. My guess would be aluminum, but I've never seen one, so that's just a wild guess.

Originally Posted by BRASSCATCHER

Its cu and Al and those machines suck to take apart!!!

Hope they are vintage, I have four of them. Maybe FLimits may want them?

Are all four of those eggs boiled? ;-)

Wouldn't the heat pipe originally have had some low boiling point liquid sealed inside of it? Where the liquid would boil at the CPU chip end, the vapor travel up the pipe to the cool end, condense, (giving up heat) and then run back down the pipe to the CPU as a liquid to start the cycle all over again?

I would guess that the strands of fine copper wire inside the tubes acted to improve the heat transfer into the liquid.

Can anyone offer any insight if this is the way they worked?

Jon.

Originally Posted by billygoat

Look for a little sticker inside. I have one and the sticker says "Zn" so as far as I'm concerned it's zinc.

And I think your heat sink is a combination of copper and aluminum. At least that's what it looks like in the picture, but I can't be sure without seeing it in person.

No sticker but it does have letters/numbers protruding on inside and at one spot says Zn also.

Look for a little sticker inside. I have one and the sticker says "Zn" so as far as I'm concerned it's zinc.

And I think your heat sink is a combination of copper and aluminum. At least that's what it looks like in the picture, but I can't be sure without seeing it in person.

Any idea what would be aluminum? I mean for the size, it is decently heavy. And there isn't much coating on it

Originally Posted by sawmilleng

Wouldn't the heat pipe originally have had some low boiling point liquid sealed inside of it? Where the liquid would boil at the CPU chip end, the vapor travel up the pipe to the cool end, condense, (giving up heat) and then run back down the pipe to the CPU as a liquid to start the cycle all over again?

I would guess that the strands of fine copper wire inside the tubes acted to improve the heat transfer into the liquid.

Can anyone offer any insight if this is the way they worked?

Saw! How are you? I meant to post this when you asked your question, but I was having browser problems and gave up.

Yes, that's how a true heat pipe works; it's part of a closed-loop evaporative cooling system. In CPU cooling applications, vapor travels from the hot end of the system, where the CPU is, through the heat pipe to the cold end (heat sink), which typically consists of an array of cooling fins, possibly coupled with a fan. Condensation then returns the vapor to the liquid phase, and the liquid travels back to the heat source. However, these systems don't necessarily rely on gravity to get the condensate back to the hot end; they also use capillary action. Most CPU heat pipes include a capillary structure (or wick) on their inner wall. Vapor condenses on the pipe wall at the cold end and migrates through the capillary structure toward the hot end at a rate sufficient to replenish the liquid that evaporates at the heat source. The most common types of capillary structure used in CPU applications are sintered metal powder, metal mesh, and grooves. Here are some heat pipe cross sections showing each type, respectively:



The iMac G4 actually used its case as a heat sink. The two heat pipes that ran from the CPU terminated in thermal contact with a big conductive metal dome that rested just beneath the outer casing. In this picture you can see the two metal "pads" (circled in red) where the heat pipes in the base attached to the upper metal case:



And this is the metal dome itself, which functions as a heat sink and as a Faraday cage for the iMac:



To achieve adequate heat transfer, the specifications called for thermal paste to be applied at these joints and at the interface with the CPU. The thermal design tolerances must have been pretty tight, because problems with overheating occurred if the outer ends of the heat pipes didn't make full contact with the case due to slight misalignment, under-tightened bolts, or even too little or too much thermal paste.

I've never dissected one of these machines, so I don't know from firsthand experience what's inside these pipes. However, the Apple manual calls them "thermal pipes," which in this context is synonymous with heat pipes, and technicians usually refer to them as heat pipes. so by definition they should contain a working liquid. If you cut open a heat pipe, you find the fluid in the wick lining, where most of it is absorbed.

The coolest application (both figuratively and literally) of this type of system is in the pipeline support structures used for the elevated portions of the Trans Alaska Pipeline System. The vertical support members (pilings) include heat pipes to prevent melting of the permafrost in which they are anchored. There are approx. 420 miles of elevated pipeline and over 124,000 heat pipes.

Hey, thanks, FL, for the detailed description. I've heard of heat pipes before and was aware of the Alaskan pipeline system but never put a lot of thought into how they worked. This is an interesting and clever application in a computer...trust Apple to make a Faraday cage do double duty as a cooling "tower". Bright idea but like it kinda fell down in how it was implemented, with all the heat failures.

I think the other place you maybe have seen something using a similar principle is with those "bobbing bird" toys where you set a glass of water in front of the bird and wet its head....it swings back and forth and slowly overbalances and dips its beak into the water, then starts the cycle all over again.

Jon.