yawn.......

Heh heh.

Nice argument. Am I keeping you up past your bedtime?

Bedtime....no.
It's the peppermint schnapps.

The following is from a post at overclockers.com.au
This investigation was done with respect to cold plates but is somewhat applicable to HSs as in almost all applications the HS is significantly larger than the die.
Take a look at the Thermacore site for a discussion of heat spreading resistance (and their vaporware Athlon and Pentium HSs).

I finally found a heat spreading resistance calculator at http://www.mhtl.uwaterloo.ca/tools.html# and the results were enlightening.

Assuming a heat source of 11*11mm (120mm sq Athlon) applied to an isotropic cold plate of 48*48mm, I calculated the spreading resistance for the thicknesses 1/8, 1/4, 3/8, and 1/2in.s (3.18, 6.35. 9.53, and 12.7mm) in aluminum, copper, silver, and (my favorite) Cusil (72%Ag & 28%Cu).

The results:
Matl . T.C. . 0.125 0.250 0.375 0.500 in. thick

Al . . 220* . 0.259 0.170 0.149 0.142

Cu . . 388**. 0.147 0.096 0.084 0.080

Ag . . 418 .. 0.136 0.089 0.078 0.075

Cusil . 515 .. 0.111 0.073 0.064 0.061

*This is the thermal conductivity of PURE Al, so the actual spreading resistance values are probably 20% higher than shown.
**for Alloy 11000

What can be understood from the numbers:
1) For all materials (and a given aspect ratio) there is a thickness beyond which the spreading resistance decreases only slightly.
2) Alumimum is a poor choice for small hot dies.
3) A 1/4 in. copper cold plate has 25% LESS spreading resistance than a 1/8 in. silver plate !
(and a 3/8 in. Cu will still beat a 1/4 in. Ag !!)
4) The Cusil values are very good, but the price may preclude all but absolute fanatics.
5) The commonly provided 1/4 in. copper is probably the most cost effective cold plate, though I'd go for 3/8 in. just to beat out silver.
(sorry GOD)

A note on the "Film Coefficient - h (W/m sqK): the value used was "2" as found in the literature. Also ran with 200 and 20000 and while the calculated values changed, the ratios did not.

Someone good with graphs, I'm not, might plot the curves and post it for the group.

be cool

[This message has been edited by BillA (edited 01-01-2001).]

1. CU later- why the **** do you think they make aluminum foil out of al, you can take it out of a 450 degree oven and hold it in your hand! you can't do that with copper!

2. the ceramic tiles on the space shuttle are actually designed to be insulators,instead of radiating the heat, they prevent it from coming in at all

------------------
new Confucious saying: Man who walks thru airplane door sideways going to Bangcock

You are correct Mr. condensate!

Because copper is a much better condtuctor of heat!
You would burn your hands. OUCHIE http://www.procooling.com/ubb/smile.gif

Posted by Joe long ago:

"I read Mike Larsens post on OCrs the day it was posted, and since I know some REAL professionals who have degrees and have worked in the fields of this for
years, I believe them more then some guy who posted something on OCrs"

I had no idea my name was being slung around or I would have posted sooner. At the moment I don't have time for a lengthy post on the matter because I am too busy working on heat transfer problems at work. Just to clarify things a bit Joe, I am a REAL professional and I have a Master's in Mechanical Engineering with specialization in heat transfer and structures. My life revolves around heat transfer so please don't put my name down as some slacker who doesn't know his stuff. Re-read my article, read some basic heat-transfer text, bring some SOLID arguments to the table backed up with NUMBERS, and we will talk more.

This is not a flame, just a clarification http://www.procooling.com/ubb/wink.gif

-Mike Larsen

Sorry for insulting you at all, didn't mean to really. Was more talking about the one ref from a website in general not you specifically. ( hell I don't even know you).

As for the Al vs Cu argument, I have removed myself from that argument as both metals have good and bad points and at best I am going to say they are BOTH good for cooling CPU's, They BOTH have advantages over each other in certain areas.

I personally like Ag more then both for H2O cooling (due to its outstanding thermal properties, it seems to just do a great job in H2O cooling, and I have yet to see a Silver HSF.)

Sorry bout that!
------------------
C-ya
Joe - Owner/Editor www.ProCooling.com
Where the Completely Addicted Come to Cool Off

Somebody set up us the bomb.

[This message has been edited by Joe (edited 01-04-2001).]

BUMP

Joe, how would you rate this thread ?

10.0

I guess that if you were in the same room you would have seriously injured eachother.
Now,I have something to say : Cu transfers heat better because it has a lower thermal resistence and Al dissipated heat better.
So why fight ?
Buy a heatsink with a copper base and aluminum fins and be happy.
And by the way,silver has the lowest thermal resistence but it is very expensive,so I don't think anyone can afford a silver heatsink.

I don't like to fight, I just don't like to see people misapplying (sp?) science.

For example, you still think that the emmisivity of aluminum makes it a better fin material than copper.

If your heatsink had no fan, and was in space, it would.

But your heatsink has a fan, and is here on earth (hopefully) where radiation of heat is a much smaller factor.

pfft silver isn't the best for the real shit buy a diamond heatsink! 4 times better than silver, order your today for just $10,000,000 ;P The real reason for no silver is cost, copper is the same to an extent.

As for someone's cu vs al foil crap that's be cause copper foil would be to fragile and expensive not because it wouldn't loose heat fast enough, any foil loses heat really fast due to surface area.

ok, tell me this though, if radiation is such a large factor why aren't heatsinks still black? I notice that most Al HSFs have moved to silver, even though black is the most radating colour and silver the least (leave a foil tray out in the sun, with water covered with clear food wrap and another painted black, see which gets hot :))

Sorry Guys, but if ever notice that most all heatsinks in pure class A Amps (current flows constantly through the transistors) That the heatsinks are of aluminum,we are talking of amps that you can use for space heaters,AKA- Mark levinson,Krell& Jeff Rowland. for all you non-Audiophiles Yes these Are audio amps some of the best in the world :D

Most manufactures dont use CU because it's 4-5 times the price of AL. Also AL is MUCH easier to machine than CU...

hehehe lots of good memories in this thread :)

LC, I know somone who cools 5000watt Power converters for some heavy machinery. I discussed heatsinks and waterblocks, and asked what they used. he said " I have never heard of someone using Copper on any Heatsink for any serious purpose, we only use Aluminum, cause if that wont cool it, nothing will" the guys got a degree from CalTech so I guess I will believe him on that one.

it prolly comes down to weight, and expense, and machinery to make them. Most of these are custom made for an application by this guy.

hey guys, I see you are hot on this one.. Now I thought this was kind of simple.

CU conducts better(collects heat better, but releases it slow)
Al disepates better(Does not collect heat as good but releases it fast)

Silver- well I spend that.

According to your application, one may be better than the other.

For plain HSF I would use AL

If you had Identical heatsinks. one AL and one CU, the AL would probaly do better with a regular fan. But the CU would probaly do better than the AL with a delta 38.
I think thats why most manufacters are going with CU/Delta 38, for the best performance.


For anything hvy duty I would use CU/With H2o
with H2o disepation is not an issue.

It's just that plain and simple. Maybe I'm wrong but I think this makes sense.

At least thats what all of you KNUCKLE HEADS have been telling me.

Go ahead and flame me, I'm an old fart that owns a chilcare center with 45 kiddies, so guess what I think about your flame?

Given the same design Cu should be better regardless of airflow (unless it's low enough that radiation is a major factor than black anodized Al is better). However because Al is easier to machine it's a lot easier to get a better design with Al which makes up for the reduced conduction (eg. a lot of Cu hsfs are press fit or soldered whereas Al hsfs tend to be extruded in one piece).

Also for the 5000W stuff mentioned, it's probably not such a small heat source as a cpu is proportional to heat produced which means heat spreading is less of an issue. Also the weight issue is going to be a major factor in something that large which makes Al a much better choice.

BUTCHER !!!!

You win da kewpie doll!!

Thank goodness this is grasped by someone!!

When my first argument (debate?) took place with Joe and others, copper HSFs were an oddity. Now we are seeing more and more of them.

yeah, now almost every newly released heatsink that performs worth a damn has copper in it

Wow where'd this shit spring back up from. :p I thought we buried this long ago ;)

hehe, either way, it is a decent thread

Well how about this!?
 

why not make a copper base heat sink (cuase copper is more dense) THEN attach that to AL fins! to get rid of the heat faster? cuase it's like more holy n stuff. ;) Both of best worlds.

I like Zalman heatsinks, they are pretty and they are quite.

ben tha one leg pimp.

What like a swifty MCX462? :p

As for Al fins - they're for weight, dissipation is the same between Al and Cu.

bump, carbon foam kicks silver, copper, or aluminums butts. problem is it's porous good for heatsinks bad for waterblocks

cabon foam

more importantly it costs some serious dollars. I think it would be fine to use in the channels of a water block though

Stuck in thread, coincidentally.

If someone reads the whole posts today, he/she will indicate that all the story is related with some area/weight ratio and some thermal conductivity. Cu "became" the future in HSFs. Sure. Of course. Certainly. Easy to understand "now".

How is that "easiness" possible in only 1-2 years? Is it increase in knowledge, technology or just evolution:p: