south bridge heat spreader wires

[Geo]

i wet ashed one heat spreader to get a better idea of how much gold could be expected.
i didnt get a weight because i have really sucky Ebay scales.but the amount of wires is impressive.
heres a single wire.

these are from the black heat spreader, not the green base.

 

[martyn111]

Good info, well presented, Thanks for that Geo, that will definately be considered next time I use Patnor's black chips process.

 

[patnor1011]

Good info, well presented, Thanks for that Geo, that will definately be considered next time I use Patnor's black chips process.

Well I am honoured by that naming of process. 8)
I must say that I started thinking about how to do them when I saw Rusty`s experiment and NoIdeas board incineration. I did what I did after some discussion with Sucho and it just happened that I have reported my experiment process here with pictures. Anyway I am glad it makes people to think more about black IC chips packages and with our collective input we only will make it better and better.

 

[joem]

Are these sold or plated gold?

 

[johnny309]

Hope this will help.....sizes and everything :

http://www.qsl.net/ct1dmk/wire_bonding.pdf

 

[Geo]

there is only two types, Au and Al.so that narrows it down quite a bit. the gold color indicates that its gold, too the thickness is less than a human hair. the reason i think these are so cool it, with the IC's and flatpacks, theres a copper frame that has to be dealt with. with these heat spreaders the gold wire has no other metal contamination. i used my oxy/acet torch to heat a dozen to almost white hot. it took a couple of seconds each and then powdered the base with a mortar and pestle.then i put them in a coffee pot and added a drop of dish soap and set in a catch pan in the sink. i filled the pot and cut the water to a thin stream and let it run till the water in the pot was clear. then gently poured the water into the pan and dried what was left. i remove the silicon wafers and ground again and repeated the rinse.

 

[jmdlcar]

Geo how many flatpack was that? To me it looks like there more gold then I though.

 

[Geo]

Jack, thats not flatpacks. look at the picture in my first post, its from the black part thats on the green fiber base. they are called north and south bridge chips on a computer mother board. theres gold on the green part and the wires are in the black part. that amount came from 12 of various sizes.

sorry about that Jack.

 

[vango57]

I pop these off of all boards I process and have several pounds of them. Have not processed any for gold but felt they were worth saving.
I took an old stanley chisel, sharpened it slightly on my grinder. I use a pair of old wire cutters as my hammer to have a good weight balance and a couple of hits and these just pop off the board, sometimes they come off in one blow but I have learned that the right weight for whatever you use as a hammer has a direct affect on the ease of removing them. An actual hammer is too heavy so finding that balance makes the job much easier because you have to hold the board on its edge and the chisel with one hand and use your "hammer" to knock it off. ALWAYS wear glasses or safety glasses as the ceramic often flies off and a piece in the eye would not be comfortable.

 

[zenophryk]

I tried the chisel method. but it was breaking them too much, so in order to get them off in one piece I now use a paint scraper. I found a very thin flexible paint scraper where the "tang" extended all the way through the handle. I then sharpened the end on a belt sander. it slides under most anything on the boards with just a few taps from a pair of pliers.

 

[Geo]

after i have the green base off the board.i use my heat gun to separate the heat spreader off the green base. if you just rip them off without heat, you will pull the gold plated traces off the green base. when you heat the black part, the glue breaks its bond and the heat spreader comes loose very easily. i also scrape the solder off the back of the base while removing the heat spreader. it makes it easier to process the green base later. i havent checked the legs to see what they are made of or if they may be plated with gold or not. i know they are just small dots of metal, im assuming they are copper because when i heat the solder, the legs remain solid.

 

[goldsilverpro]

Geo,

You're getting pretty damned good at this stuff.

The only thing I know about these is what I've learned on the forum. Some questions:
(1) Is the purpose of the heat spreader to replace a heat sink?
(2) Are the wires solid gold or gold plated copper?
(3) I assume they are locked into the plastic and not connected to anything electronically. Is that true?
(4) In the last photo on your first post, there is one wire. Can you mic it or is it too small? What is it's length? What is that thing on the end and what does it do?
(5) How many wires per unit?

If the only function of these is to distribute heat away from the chip, pure copper would work at least as well as gold. Unless the wires are so thin that it would be cheaper to make them from solid gold, rather than plate them, I would guess they are gold plated pure copper.

 

[Geo]

thanks GSP, that means alot coming from you.ill tell you what ive learned.

1.the heat spreader contains the silicon chip and the binding wires.some of these chips have a heat sink and some do not. the spreader is not ceramic nor is it plastic.it is organic because concentrated sulfuric will break it down though it is very heat resistant.
2.the bonding wires are made of either solid gold or aluminum.if you can see the wire and it looks gold, then it is gold.i dont have the means to mic one wire but it is less diameter than a hair.(i made a side by side comparison)
3.the wires connect to the silicon chip embedded in the heat spreader.
4.they connect with the small ball at the small end of the wire to the chip.the wide end bonds to the gold plated pad on the green base.again, i cant mic it and couldnt find anything small enough for a side by side comparison.
5.ill post a picture with one of four sides. i didnt count the wires but if you multiply by four it will give you a good estimate.the wires are in pairs.


heres a different view of a single wire that shows the ball at the end.

 

[samuel-a]

Chris, see my post "Black IC's - a look inside".
You can find high rez pictures of wires and wafers and more info regarding your Q's in the tutorials section under "Processing Black IC's - The wet way".

As Steve says, nothing new under the sun anymore... 8)

 

[zenophryk]

So these IC packages are refered to as BGA (ball grid array) packages. http://en.wikipedia.org/wiki/Ball_grid_array and the pins are indeed solder balls. I have read elsewhere that they (the solder balls) contain a higher than average (for solder) percentage of silver, which may be why they aren't melting with the rest of the solder.

So you're calling the black epoxy top of the chip a heat spreader? is that actually what it is? it seems to me to be just the silicon wafer with the gold bonding wires. I would expect a heat spreader to be some sort of iron, aluminum, or copper based square designed to take heat away from the wafer and help distribute it to a heat sink that may be mounted above the chip. So I don't think these southbridge chips even have one. Which is cool cuz there's less base metal to deal with the epoxy/plastic black top is only there to hold the wafer and keep all the bonding wires inline and protected.
Not trying to be a know it all, just regurgitating other things I've read and maybe able to fill in some gaps. I have a few pounds of these that I havn't dug into yet.

I'm going to try a heat gun. do the tops just pop off or do they still need a little help when you heat gun them?

 

[Geo]

check this link.the term heat spreader is correct when it refers to the top of these chips.

http://www.minteq.com/our-products/minteq-pyrogenics-group/pyroid-ht-pyrolytic-graphite/

the top lifts at the corners. i use a knife blade to lift them off.

 

[samuel-a]

Geo

Actually, in the link is a product made of graphite sheets that are held by thermal grease to the plastic package.
Sometimes, the same arrangment is done with Al foil.

In some high end applications, the graphite sheets (heat spreader) replace the thermal grease altogether, and an aluminum heatsink is screwed to the component/cpu.
In my mind, the epoxy material sole purpose is to hold the wafer and wires together and be able to withstand the heat generated by the resistance, although it does act like a heatspreader (like every object exist), Plastics/resins/epoxy are known to be bad heat conductors. That's why, for the most part, an heat sink is attached to n/s bridges.

I have several graphite sheet, i'll upload a picture later today.

 

[devo]

Just wanted to say thanks for those awesome pictures. I have no idea how you guys get those, but they always impress me.

 

[goldsilverpro]

As I understand it, pure gold bonding wires are usually one of three different diameters: .0007", 001", or .002", with the first 2 being the most common. At a $1645 spot, here's the dollar value of each, per inch of length.

.0007" diameter = $.0066/inch
.0010" diameter = $.013/inch
.0020" diameter = $.053/inch

A tr oz of .0007" Au wire is 4 miles long.
A tr oz of .001" Au wire is 2 miles long
A tr oz of .002" Au wire is 0.5 miles long

I think I read in several places that the wires on these were 17 to 20 microns thick. That would put them in the .0007" class above. It would be interesting to measure them, though. Anyone have a good optical comparator? Or, a wire could be cut to an exact length and weighed. It would require at least a 5 place balance, though, to get any accuracy at all.

As usual, please correct me if my math is wrong.

 

[Geo]

thank you Devo, i have a set of lens that i use with my camera. it lets me focus in on some very small stuff.

Sam, lets try a patent this time.i know you know more about this stuff than i do because you have spent more time dealing with it and im not trying to be difficult, just thorough.


http://www.freepatentsonline.com/6552907.html

Abstract:
The present invention is directed to a heat dissipation structure for an integrated circuit package, comprising a thermally conductive solid layers, one of which has receptacles for holding a thermally conductive flowable material, the heat dissipation structure being placed between the electronic component and the printed circuit board. The present invention is used advantageously with a primary heat sink placed on the top side of the integrated circuit package away from the printed circuit board. The heat dissipation structure preferably hemispherical balls on the package side of a high heat conductive plate to improve heat transfer from the die to the integrated circuit, especially, BGA, substrate to PCB power planes for heat dissipation and leads to improved secondary heat transfer from IC die in BGA packages to the heat spreader power planes in the system PCB. The heat dissipation device allows retro-fit of the heat transfer/transfer mechanism or primary attachment.

it is also referred to as a "heat dissipation structure" but heat spreader was also used and is shorter to type.