How do I reball a BGA with capacitors on it?

[dicky96]

Hi guys

How do I reball a BGA like this one that has capacitors on it? Obviously my usual technique of dragging a solder ball around with my iron, then cleaning with small strips of braid is not going to work

I removed another one of these GPU today as it was testing faulty measuring resistances on board - I decided to clean that one up for 'practice' and did not even notice all the capacitors under the sticky flux.

It's only when I kept hitting something 'gritty' while I was trying to clean he centre area of the BGA that I cleaned all the flux off to see what was the problem. By this time I had capacitors stuck all over the place lol

But the other one which I ordered a stencil for is almost certainly good -so I am going to need another technique to get that one cleaned ready to reball.

[diif]

Re: How do I reball a BGA with capacitors on it?

That's not something I've seen before. I'd use your usual technique but with a bit more finesse, use your microscope.

[Spider1211]

Re: How do I reball a BGA with capacitors on it?

The stencil will usually have a recess or a cutout which fits over the caps.

[dicky96]

Re: How do I reball a BGA with capacitors on it?

That makes sense the stencil will work OK (I ordered one for this type of BGA) I was more concerned about preparing the BGA for reballing. One of them came from a board that had short on Vcore but once I removed the GPU the short was still there and it turned out to be short circuit MLCC

So the GPU should be good if I can reball it and resolder

[Spider1211]

Re: How do I reball a BGA with capacitors on it?

As diif mentioned, steady hands and a bit more finesse than usual should do (and microscope ofcourse). I'ld try using a smaller tip (BC2 if you have) and thinner wick, they allow for more control around edges and small/tight locations.

[dicky96]

Re: How do I reball a BGA with capacitors on it?

OK I did it - on one of the other GPU I removed

This was really quite fiddly to do. The balls outside of the perimeter of the capacitors was not so difficult, I used the usual technique of dragging the solder ball to within a few mm of the capacitors, then I resorted to using the microscope toe clean the rest. I still used the BC3 tip and solder braid.

The central area within the fence of capacitors was considerably more fiddly - but taking my time I cleared most of it using the BC3 and braid without too much trouble.

The real problem started with the balls in the enclosed corners. I tried using the BC2 plus the braid, but even preheating the GPU with my Quick 861DW, then switching to the T12 on boost, I found it impossible to get enough thermal transfer between the soldering iron tip and the braid to melt those balls

In the end I went back to the BS3 and let the braid become more soaked in solder to improve thermal transfer and was able to clean out the corner ball - but it is very fiddly (and not to mention time consuming!) and takes a steady hand

The results were pretty good. I still managed to dislodge one of th e tiny capacitors but after cleaning off a lot of the excess flux I was able to push it back nearely into position using the BC3 tip. It's not exact but the capacitors don't solder to the PCB, just the BGA, so I think it is probably close enough

Would I like to do this job on GPU on a daily basis? - no - it's time consuming and easy to make a mess. I have one more suspected good GPU to clean as well so I still need to do this at least once more LoL