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In an attempt to fix a short circuit on a BGA package, I ended up making things worse. The BGA is desoldered with some of the balls left on the BGA, some on the PCB, and some gone entirely. I don't have replacement solder balls or a stencil to replace them. Instead of ordering some, waiting and then reballing by hand, I'm considering pulling off all the balls and soldering the pins directly to the pads (preapply some solder to the pads and then use hot air). I haven't been able to find information about this online, so I assume that means it's not a good idea.

What is the benefit of the solder balls? Do they make soldering easier? Is it possible to solder the pins directly to the pcb pads? Between waiting for new solder balls to manually replace on the package (which I've never done before) and attempting to solder the bga directly to the pcb, which is recommended?

It's worth mentioning that another option is to buy another IC, since it's only $20. But I'd prefer to avoid that if possible.

Edit:

Unfortunately hand soldering without solder balls was more difficult than I expected. I tried this several times and was unsuccessful each time. Although I can't be sure about why it didn't work since I can't check the individual connections, the problem seemed to be that I wasn't able to preapply enough solder to the pads and pins since the metal contact area is so small. The height of the applied solder seemed to be consistent enough, so I don't believe that was the issue.

A possible alternative to get more solder would have been to spread solder paste over the pads. However, it's difficult to control the amount of paste with this method and it sounds like it would be asking for a short.

I think I'm just going to order a replacement IC. If the IC were more expensive, I'd probably try to reball by hand first.

MattHusz
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  • never balled BGA before, but based on my experience with QFN yeah i think you should wait. chances are high you'd get dry joints doing it the impatient way – Ocanath Jun 09 '20 at 03:45
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    The advantage of solder balls or stencils is the right amount of solder in the right spot. I wouldn't do this by hand or "pin to board" on a BGA, too big of a chance of shorts, cold joints, incomplete soldering, or other. The only way to inspect it is via x-ray or smoke test... – Ron Beyer Jun 09 '20 at 04:03

2 Answers2

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Is it possible to do? Sure anything is possible. There are many examples of people hand soldering bga csp or wlp type packages. Some do it as a repair others do it for debugging. Mostly as dead bug style.

Is it practical? No. Depending on the chip the extra length of wire may cause issues especially with high frequency signals. Since you want to solder the chip back in place on the board, the amount of tinning and solder you add to the board and chip is crucial to ensure no shorts no cracks no uneven heating. You are liable to ruin the chip and board that way.

Passerby
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Head over to YouTube and watch some videos by Louis Rossmann. Louis repairs Apple Macbook products that Apple won't touch. I see him remove and replace BGA chips all the time.

In his early days, he used to do the whole solder ball thing - he had the stencil to hold the balls in place on the chip, then reflowed them so they would adhere to the BGA chip, then reflow the chip back onto the board. He did this when removing a good chip from a donor machine to put into the machine undergoing repair.

However, he now simply uses lots of flux and creates solder bumps on both the PCB and the BGA chip, then reflows the chip back onto the board.

I have not yet tried this myself but I intend to do so. Louis makes it look easy - I am certain that it is NOT easy but he does it regularly.

As always, practice makes perfect. But being able to watch someone do it goes a really long way to showing you that YOU can do it as well.

Dwayne Reid
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  • Cool, thanks for the suggestion. That strategy (solder bumps on pcb and bga) is actually what I tried, but hopefully (as you say) seeing it will make it easier to get working. – MattHusz Jun 10 '20 at 02:04
  • You do need a decent hot-air pencil to do this well. – Dwayne Reid Jun 10 '20 at 02:24