The soldering under the BGAs letting go, is the commonest problem with both the Sony PS3 ( "yellow light of death") and the X-Box 360 ("red ring of death")
Those names for the conditions refer to the behaviour of the front panel indicator LEDs when the faults that result, show themselves.
I am quite convinced that the slow running of the fan at idle, is a major contributory factor in the failing of the BGA soldering.
Arfa
In article , Arfa Daily writes
I'd recommend Arctic Silver.
nah, standard IPA works fine. The trick is to use clean tissue wetted with IPA, wiping just once or twice then replacing with a fresh piece, repeating until the CPU is clean. If you go back with used tissue, you just spread the AS about more.
If it makes that much mess, you're using too much. See the application tips on the AS website. You literally only need a half-a-grain-of-rice sized blob in the centre of the CPU heat spreader, it'll spread out by itself with pressure from the heatsink. Note AS say it can take a few heat/cool cycles to become fully effective, and indeed this is what I have found.
It is. A colleague at work was struggling to cool a CCD (a big one!) without having to resort to cryogenic cooling. He was experimenting with a Peltier cooler and unable to transfer heat away from the CCD fast enough. I suggested he try replacing the standard white goop with AS and he was astonished at the massive improvement in heat transfer.
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In article , Jeff Liebermann writes
I herded a fleet of 21264s (AlphaServer DS10) for a while. Impressive heatsinks in those. One is still in use today.
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In article , Arfa Daily writes
They do, they just take three times longer to boil. They're nowhere near as ubiquitous in American kitchens as they are in the UK.
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In article , Michael A. Terrell writes
2kW and 3kW kettles are common. 2kW is ~8.3A, 3kW is ~12.5A. UK plugs and sockets (=receptacles over the pond) are rated for 13A.
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In article , Arfa Daily writes
Which is what caused the 'red ring of death' on Microsoft's Xbox.
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On the gas or electric stove. A lot of people heat the water in a microwave. Fast and efficient.
The same thing with water demand when people rush to the bathroom during a commercial. :)
-- Politicians should only get paid if the budget is balanced, and there is enough left over to pay them.
Yes indeed. This is kind of what I'm finding. I in fact use a vanishingly small amount of AS which as you say is easy to remove with IPA, but I come across devices that have been 'excessed' on the AS by other people, and it is very messy to remove compared to white compound. Until I really got into using the stuff, I was of the same misconceived notion about the quantity to use, as others seem to be. I have always been sparing with compound - and I use a lot of it as I repair many big amps for a living - but it is a fact that a very thin translucent layer of white, is not effective enough on a standard non-flatted device face, and heatsink contact area, whereas with AS, it would appear that it is. These BGAs are the size of a large graphics chip, and I apply a very thin line of AS across the face, and then spread it using an old credit card, rather than hoping that it will spread out across the whole face on its own. This negates the tedious disassembly and reassembly required to get at the heatsinking faces if the cooling turns out to not be adequate. So far, this seems to be working well.
Arfa
I've evolved into the single cup K style or K-Cup Keurig machine made by Cuisinart. Mine turns on at 5:am water is ready to brew in 2 minutes. Place k-cup in head (could be coffee, chi-latte, hot choc, Earl Grey,) close head and hit brew. In 45 seconds you have 12 oz of your favorite brew. I shelved my Cuisinart Grind and Brew conventional 12 cup machine several months ago. You can buy k-cups filled with your favorite or use the k-cup adapter and spoon in your favorite grind.
Oh and about heating water in the microwave. There is a phenomena called hyper-boil that I'm sure you know about. Got to be careful
-- Live Fast, Die Young and Leave a Pretty Corpse
Yeah, but your odds of having this happen are about the same as flashing your high beams at oncoming traffic and getting killed as a result of a gang initiation.
Jeff
Some parts of the country that's a real possibility. And you wouldn't even have to flash your lights.
-- Live Fast, Die Young and Leave a Pretty Corpse
I let things sit for 30 seconds or more before I remove them from a microwave.
I don't drink coffee, and I can't find the tea I like, except as a concentrate. The price has doubled in the last year, so when i run out of what I have, I doubt that I'll buy more.
-- Politicians should only get paid if the budget is balanced, and there is enough left over to pay them.
On the other foot, I suspect that a high air flow fan will make it worse. The problem is NOT that the BGA is flexing with increasing temperatures. It's that the PCB underneath the BGA is flexing. Stabilizing the temperature of the BGA is probably useful, but unless the PCB is also stabilized, it will bend, bulge, buckle, twist, or otherwise go through various contortions trying deal with the temperature difference between the BGA and the PCB. If the differential temperature is large enough, the PCB may bulge enough to tear way from the BGA. Again, the BGA does not move, the PCB does.
Now, add a high air flow fan into the picture and we have a larger temperature differential. The air flow will probably do a fair job of cooling the PCB because of the comparatively smaller mass of the PCB. The thermal conductivity of G10/FR4 isn't all that wonderful, resulting in a localized hot spot. With a larger difference between the BGA area and the surrounding PCB, the result is a larger PCB bulge with PCB air cooling. I've seen PCB's (usually motherboards) with permanent bulges under BGA's from this effect.
For entertainment, take any PCB, heat it in the middle with a heat gun, and watch the bulge form. It's that bulge that's ripping the BGA's apart. Extra credit to laptop manufacturers, that add heat sinks to the BGA, and then mechanically connects the heat sink to the frame. When the board bends, it will literally tear the BGA off the PCB, since the heat sink can't move with the board.
In the instructions for hot air reflowing of BGA's, there's usually a section on pre-heating and slow cool down of the PCB. The idea is to not tear the BGA ball apart from differential thermal expansion between the large thermal mass of the BGA and the comparatively smaller mass of the PCB. It's exactly like moving a solder connection while it's cooling. You get a "cold" solder joint.
Incidentally, I once designed a 150 watt 2-30Mhz HF power amplifier. After about a year of normal use, we started seeing failures caused by the power transistor screws coming loose. Suspecting cold flow, I worked on improving the grip with stainless inserts. This worked, but now produced failures in the ceramic case power transistors. The clue was when a PA module arrived with all the ceramic lids popped off the transistors, but still working. Weird(tm).
After a dozen bad guesses, I determined that PCB expansion and contraction was initially causing the loose screws. When the screws were properly secured, the next weakest link was ripping the leads out of the power transistor case, causing the glued lid to pop off. The problem was solved by slightly pre-bending the power transistor leads in a fixture so that PCB thermal expansion would be absorbed by the bends. I still do this even on TO220 packages, which can have the same problem. Too bad it can't be done with BGA packages.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
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Ok, let's do the numbers. The coefficient of thermal expansion for G10/FR4 is: 1*10^-5 cm/cm/C That means a 1 cm long piece of G10/FR4, will expand 1*10^-5 cm for every degree C of temperature differential.
So, we have a big fat BGA chip, that's about 5cm across. It's running hot with a bottom temperature of about 80C. Assuming the PCB is running at room temp of 25C, that's a 55C differential temperature. Over the diameter of the BGA, that's 125*10^-5 cm movement of the PCB.
Solder balls come in all manner of sizes, but my guess(tm) that for a
1mm pitch BGA, a 0.4mm ball is appropriate. When soldered, the ball will remain about the same diameter, but the height will be reduced to about 0.1mm.The angle that the ball moves over temperature is: angle = arctan ( 125*10^-5 cm / 0.01cm ) = arctan 0.125 angle = 7 degrees which is a fair amount of ball rotation. Do that often enough, and the ball will "roll" itself off the pad. For a sanity check, solder a rigid bar of something to a flat surface, and bend it back and forth about 7 degrees. It will take a while, but it will eventually break.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
Great info and insights in both posts as always Jeff. I will take them into consideration. The temperature differential thing is something that I hadn't considered, but following through your numbers, seems to be a very valid point ...
Arfa
Well, I did manage to make one mistake. The 7 degrees is the worst case bending angle assuming everything accumulates in one direction. That's not the case as local heating of the PCB will be from the center outward. Instead of 125*10^-5 cm of lengthening measured from the edge, the PCB will elongate half that amount, measured from the center of the BGA. Correcting accordingly:
The angle that the ball moves over temperature is: angle = arctan ( 63*10^-5 cm / 0.01cm ) = arctan 0.063 angle = 3.5 degrees That's still enough to tear apart the solder ball, but not as radical as I previously suggested.
One solution is to use a BGA adapter socket. Obviously, this isn't going to work inside a laptop, where vertical height is a major limitation. Same with some desktops, where the CPU heatsink and fan can only be so tall or air flow out the top of the heatsink and fan will be constricted. I've never tried to retrofit one of these into an existing motherboard, but it sure looks tempting.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
In article , Arfa Daily writes
Have you tried applying the white stuff to both surfaces, then scraping it off with the edge of a card? That will fill in any valleys on both surfaces, and you should get a good thermal bond with the minimum of compound.
This is the method that AS suggest using, by the way.
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This is something that I was talking about with a colleague just a few days ago. I'll take a look at the links. Going back to the differential heating issue, I've thought a bit more about it, and it seems that the greatest source of heat is going to be the top surface of the BGA itself, which has the bonded heat dissipation plate for interfacing with the heatsink assembly. Heat getting into the PCB is going to be two ways i.e. by conduction through the solder balls, and by direct radiation from the underside of the chip. Neither of these are going to be particularly efficient, and I would expect as much heat as possible to be directed upwards into the plate, by design. So it seems to me that the board is going to remain relatively cool, compared to the underside of the BGA, and more to the point, the upper side. So the hotter that the BGA is allowed to run, the greater will be the undesired thermal difference between board and chip. Therefore, any help to the cooling of the upper surface of the chip, should help to reduce the temperature differential rather than exacerbate it, shouldn't it ? To take it to its logical conclusion, if you could remove all heat that the chip was generating, then there would be none to heat the board, so there would be no thermal differential, at all ??
Arfa
Yes Mike. Prior to starting to use the AS, I have always treated both surfaces when using white, contrary to much perceived wisdom where it is insisted that only one surface should be coated. I believe in doing both surfaces for the exact same reasons that you cite. I am also doing both surfaces with AS, but very sparingly. There are always milling patterns on the heatsink faces on these machines, which I think is a bit bad on the part of the manufacturers anyway, given the huge thermal loads that are produced by these chips ...
Arfa
I've never thought it necessary to coat both surfaces. If you use sufficient paste on one it will suffice for both sides. Key word sufficient but not overly so. I guess it's just something you develop a knack for in knowing what is too much or not enough. This 120 watt AMD 955 PhenomII chip in my PC runs in its normal temp range. Idles around 43c. CPU fan runs at 2500rpm, half of 5000 at full speed automatic control. What I'm getting at is the heatsink that comes with the chip has a very thin coat of Arctic. And it seems to do very well being applied to the heatsink side only.
-- Live Fast, Die Young and Leave a Pretty Corpse
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