[Guy Kuo]

Although I can't recommend doing this because it's easier to make things worse than better, but I just managed to reflow the soldering of a large BGA video chip package in my 12 inch dual USB iBook. The video processor chip had developed the dreaded intermittent connection to the logic board. That much was pretty easy to isolate by just pushing around on the board to find where the fault appeared and disappeared with pressure. I had hoped it was one of the surface mount components that would have been easy to resolder. Unfortunately, it turned out to be the video processor chip, a ball grid array package about 3 cm square on the underside of the logicboard below where the HD sits. Lord knows how many solder balls are in its array. Well, without any visible leads and all its connections under the chip, you'd normally be SOL and need to replace the motherboard. Since, I was out of warranty and not in the serial numbers being repaired by Apple, I had nothing to lose. I decided to attempt reflowing the video chip BGA package even though I don't have a rework station. The air flow of my heat gun wasn't too high on the low setting. High setting would blow components right off their pads.

I took my heat gun on its lowest setting and practiced reflowing some scrap circuit boards. It worked fine on small smd's and multi lead packages but I was going to be crazy enough to tackle a big BGA package. First I removed the foam like thermal transfer pad with a sharp knife. This was done in one piece so it could be reused later. Then, I masked off the logic board with several layers of aluminum foil such that only the video processor BGA and 1/2 inch of the surround PC board was exposed. The board was kept horizontal. Started with the heat gun (on low) about twelve inches away and very gradually lowered it over about ten minutes down to roughly 3 inches above the IC. The slow heat up was to reduce thermal shock on the board. Once I saw the solder on nearby SMD's change sheen, I knew I was near the right temp. The BGA is bulkier and insulates its solder balls because those are all under the package so I kept that distance for one minute to allow the solder balls to melt and reflow. Too much heat and the balls would melt and short together. Too little heat and I'd accomplish nothing. Finally, I gradually backed off the heat gun. Great care was taken to avoid bumping the board and keeping it level.

Inspection of the BGA package shows it definitely had sunk down a little closer to the logic board. That indicated the solder balls did all melt. If I was lucky I didn't short things out, popcorn the chip, or destroy the logic board. Amazingly, it worked. The intermittent video is gone and the laptop now works again. No more senstivity to pressing on the logic board.

So there you have it, an apparently successful BGA chip reflow done with VERY primitive tools. No doubt the real rework station owners will cringe at such a crude method, but heck it seems to have worked. No telling how long it will last though.

You probably shouldn't try this, but I thought it would be an interesting report.

[sniffer]

Well done. So everything is back to normal now?

[Nerozwei]

I suppose your iBook was not covered by the Logic Board Replacement programme?

[Guy Kuo]

It was outside the serial number range and the symptoms were not scrambled video but backlight faiding (unrelated to the hinge/reed switch cable). Apple wouldn't cover it under the extended repair program.

The problem was reproduced easily by very lightly pulling up on the video processor. After the solder reflow, I haven't been able to get it to fail despite pushing and prodding the board and video chip. So far so good.

[Guy Kuo]

It's still alive!

[Nerozwei]

Originally posted by Guy Kuo:
It's still alive!

Sweet

[agentz]

Cool, well done!

[Carl Norum]

Wow - you sure beat us out by a step. We just sent a couple of logic boards off with the regular work shipment, and they came back nicely reflowed. So for those of you with problems and without access to tools yourself, there are a lot of PCB manufacturers out here who might have the right heat dies and presses to help you out.

[Guy Kuo]

I'd imagine commercial reflow equipment to be quite a bit safer than the way I did it. If someone can find a PCB manufacturer willing to reflow the board, I'd definitely let them do it rather than wield a hot air gun like I did.

[Guy Kuo]

And....... it's still running!

[monkeyxiii]

Thanks for posting your experience with reflowing the graphics chip with a heat gun. I took your idea and adapted it using a standard propane torch. I just finished reflowing the graphics chip on my 12" G3 ibook with this method and it worked! The display backlight works flawlessly now.

Here is what I did:

-removed the bottom plastic case and bottom shielding
-removed the foam on top of the ATI graphics chip with a sharp blade
-opened up the display to max and propped the ibook upside down on top of a block so that the underside of the logic board is flat and the display is far from harm. This step seemed to be unnecessary since the top case never got hot enough to do any damage.
-put a few small pieces of solder on top of the chip (to indicate when the top of chip reaches solder flowing temperature)
-put a couple of pieces of solder around the chip (to indicate that the board around the chip has reached solder flowing temperature)
-lit the propane torch (benz-o-matic) and adjusted it to a low setting
-pointed torch downward and hovered the flame about an inch above the chip and constantly moved the flame back and forth across the chip to cover the entire chip area
-continued doing this until the chip slowly heated up and the solder bits I placed on the top of the chip started to melt and formed into balls
-kept the heat on the chip for about 15 seconds or so more to hopefully melt the solder on the underside of the chip (obviously the solder on the top will melt first)
-removed the heat and let cool off
-tested to see if it worked by starting up the ibook
-for me this worked the first time!

For me, the solder that I placed on the logic board beside the chip did not melt meaning the logic board beside the chip never reached the critical temperature that would cause other components to reflow or fall off. As a result, the operation was probably pretty safe. This is good because I kept all the components in the case while doing this.

I don't recommend this for everyone but if you are careful it seems to work fine.

[ghporter]

EEEKKKKKK! BGAs are BAD to mess with!!!! Of course you guys didn't have a lot to lose with computers that didn't work properly, were out of warranty, and were not covered by logic board replacement programs, but oh my!

Just the thought of a heat gun on a circuit board gives me chills. A PROPANE TORCH??? Holy COW!

[Guy Kuo]

Wow, a torch. That IS amazing. Congratulations. That's even more risk of frying the board than a heat gun. I'm amazed.

[Tuoder]

You two are crazy like a fox.

[Neato]

I too had the same problem with my iBook G3. I had previously replaced the screen hinge after dropping it which involved taking it all apart, so when the screen backlighting became intermittent, I chanced upon Guy's fix and decided to try it for myself. It was way out of warranty etc. so I had nothing to lose. Heat gun freshly bought, I made myself a rum and coke, cleared off the dining room table and set to work. I took as much of the iBook apart as I could so that nothing got in the way. I fashioned a heat baffle out of 4 layers of tin foil and laid it onto the motherboard where the BGA was, smoothin g it over so that I could trace the shape of it so that I could cut a hole roughly the same size with a scalpel. I too placed a bit of solder on top of the BGA so that I could see the melting point and fired up the heat gun at a low setting. Starting 12 inches directly above for about 10 seconds, I lowered it to about 2 inches away until the solder melted and held it there for a further 10 seconds. Then I removed the tinfoil baffle and allowed it to cool. I then attached all the bits which the iBook needed to function without fully assembling it, just so that I could confirm that it was all working fine before I went about putting it all back together for real. Presto! It was all working fine so I reassembled it, adding a touch of thermal conductive paste on the top of all 3 chips as well as their thermal pads. So there we go, it's all working again. Who knows for how long but it was better than chucking the whole thing away.

[Guy Kuo]

Nice picts and description of your technique. Mine is still working 24/7 as a server.

[MacInEnterprise]

A nice 14" iBook G3 was entrusted to me to repair. No amount of shims could get the system to boot up and stay up, but a firm thumb on the chip allowed it to boot.

Since shims were neither a desirable, permanent or clean solution, after reading the posts above, I decided to go the reflow route with a heat gun.

Now with a heat gun in hand, I'm going to reflow the solder on the ball grid array (BGA) video chip.

I've done some research on the subject leading up to this, and I've learned far more than I ever wanted or need to know. Here's what I found out:

A typical temperature profile for reworking a BGA device involves:

1. A gradual increase in temperature, of about 1 to 3 deg. a second over a period of 60 sec., up to a temperature of 150 deg.
2. Flux activation begins at 150 deg.
3. Through the flux activation phase, a slow ramp up of temp. to a peak of about 180 degs over 90 seconds.
4. Reflow begins at about 180 degs.
5. A gradual increase during the reflow phase to about 210 degs. for 60 sec.
6. Cooling phase should then begin gradually.

This doesn't mean that the ATI BGA chip on the iBook has the same temperature profile, but I think it's a safe profile to base my work on.

I think you'll see from this temperature profile, however, that it doesn't take an extreme amount of heat to reflow the solder. So careful attention to time and temperature can achieve the results you're looking for. Not paying attention to detail can result in a ruined chip. (But hey...what has anyone to really loose when the iBook is out of warranty, costs too much to replace the logic board, and is just gathering dust anyway?)

Short of a temp. gauge, I think the technique of using pieces of solder to gauge the temperature is a good one.

After the solder is reflowed, and the iBook is working again, I think some well made shims will keep it from flexing and breaking its balls again.

I'll document my work and post pictures when I perform the work...

[Dork.]

Wow. Like, wow. I bow to your mad BGA rework powers!

[Guy Kuo]

I can happily report that over two years later, that same reflowed iBook is continuing to run 24/7 as a light web server. Not too bad for such an old machine that would have otherwise gone to the dumpster.

[MacInEnterprise]

Pictures forthcoming...

I attempted to reflow the solder under the video chip over a period of 3:30 minutes, but because my heat curve was too conservative and careful, I most likely didn't get the chip hot enough, so no reliable video yet.

The iBook boots up reliably now, without having to put pressure on the chip. Unfortunately, now I don't get any video even when applying pressure to the chip.

One step forward...One step back.

To accommodate the higher heat of a repeat session, I removed the logic board entirely instead of just removing the bottom shield.

If all else fails, I may remove the BGA video chip entirely to inspect the solder balls...but considering the resistors on the other side of the board, it's the last thing I want to do at this point.

[MacInEnterprise]

Classic American mistake that has even cost NASA a Mars probe: Conversion between metric (what the rest of the world uses) and Fahrenheit (what we're too stubborn to give up).

This explains a lot about why my heating didn't begin to reflow the solder on the video chip...

Here's is a more specific and accurate curve:

1. A gradual increase in temperature, of about 1 to 3 deg. up to a temperature of 150 deg C (302 F). Pre-heating is extremely important so boards don't warp. It may take a minute or even longer to pre-heat...No need to rush it. Flux activation begins at 150 deg. C (302 F)
2. Through the flux activation phase, a slow ramp up of temp. to a peak of about 180 degs. C (356 F) over about 90 seconds. Reflow begins at about 180 degs. C (356 F)
3. A gradual increase during the reflow phase to about 210 degs. C (410 F) for 60 sec.
6. Cooling phase should then begin gradually, not abruptly.

I found a really good graph of the temperature curve here: