HDD GURU FORUMS

I've got a bunch of "lab rats" (dead phones) in a box that I'm toying around with to practice chip off. Desoldering the NANDs is usually no biggie, but for the chips that are glued failure rate is almost 100%. In theory, heating everything (the whole board) evenly for enough time should break / weaken the glue. I can confirm this with a scraper / metal hook where I can peel of small chunks of glue near the edges, but for glue that's stuck under the chip - BGA mostly - I cannot see how to make it weak enough to pull the chip. Using a pryer / spludger under the chip works, but that almost always destroys the chip as well so I'm back to square one.

What's your go-to-approach for glued BGA?

Well,
you get glues removal solutions that you put and it loosens the glue and then you scrap it and then remove the IC

For the phones I don't want, and would be a pain to removed with a lot of epoxy, I sometimes cut the pcb around the chip and grind it down at the back of the chip (opposite side of PCB) until close to pads of BGA and then work with heat.

Most of the issue is the epoxy around the edge of the chip. I guess a Dremel tool would work to get most away if you are careful.

If you don't want to damage PCB then, yes it is hard..

I do a lot of iPhone/iPad data recoveries and repairs and I have to deal with underfilled IC's all the time. Manufacturers use different types of underfill epoxy depending on the application (water, physical strength, vibrations etc) so you have to adapt to different IC's, boards and manufacturers (Apple, Samsung etc.). Generally speaking, it's all about trimming the visible edges so that adjacent components don't peel off and applying the right amount of heat to the IC and using a specialized "spatula" when necessary to lift the IC.

Here are some examples of the tools required, sorry for the external links:
https://www.unionrepair.com/qianli-toolplus-007-side-glue-cleaner.html
https://www.unionrepair.com/qianli-009-ic-chip-removal-blade-16-in-1.html

Depending on the type of IC and the epoxy used, sometimes just prying it off the PCB at the appropriate temperature is sufficient. When dealing with softer or larger IC's, such as the SDRAM or SoC (CPU) on the iPhone, you have to get the temperature right and use a chip removal blade to work the underfilled epoxy loose (without damaging the pads of course ). There's a surprising amount of intuition involved...which means lots of practice and failure until you get it consistently right.