Smd rework - Solder balls squeeze out

[caphair]

Can anyone explain why and how to prevent solder that seems to squeeze out under a BGA chip when reworking or applying heat for removal?

Have a couple iPhones been working on and it's happened twice on various chips like the NAND and CPU

I know iPhones use underfill but could that be the reason?

[stj]

Re: Smd rework - Solder balls squeeze out

it could be underfill expanding, the only other way is if you push down on the chip

[caphair]

Re: Smd rework - Solder balls squeeze out

it could be underfill expanding, the only other way is if you push down on the chip

I'm guessing using flux would only make it worse if underfill is creating the issue?

How would you rework ics that use underfill?

[stj]

Re: Smd rework - Solder balls squeeze out

no idea,
i suppose you lift the chip and clean off the underfill.
then re-ball and put back down.

personally i dont touch such stuff.

[keeney123]

Re: Smd rework - Solder balls squeeze out

I'm guessing using flux would only make it worse if underfill is creating the issue?

How would you rework ics that use underfill?

Here is and article than explains on type of underfill attached.

[vinceroger69]

Re: Smd rework - Solder balls squeeze out

This lady has some good guides on her youtube channel this is about underfill ics
https://www.youtube.com/watch?v=FUKJaf029tY

[badcaphunter]

Re: Smd rework - Solder balls squeeze out

Jessa's channel is good for IPhones/Ipads and Louis Rossman's channel focuses on mac book motherboard repairs


IPhones/IPads
https://www.youtube.com/channel/UCPj...e1o_lp1US9TpWA

MacBooks
https://www.youtube.com/user/rossmanngroup

[Deusjevoo]

Re: Smd rework - Solder balls squeeze out

Can anyone explain why and how to prevent solder that seems to squeeze out under a BGA chip when reworking or applying heat for removal?

Have a couple iPhones been working on and it's happened twice on various chips like the NAND and CPU

I know iPhones use underfill but could that be the reason?

What you use? Hot air? IR? Rework station? Do you preheat?
Photo of setup and pcb/underfilled chip?