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After I removed the Touch IC chip, I put some solder onto the pads of all 3 chips, U2401, and both capacitors C2432 and C2433.
The solder was placed successfully, but when I tried to rectify some imperfections, the solder disappeared on a few pads and I couldn’t put solder on them again.
See photo below.
What happened and what mistake did I make?
Is this recoverable?
Ist dies eine gute Frage?
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Is this the same phone as the one in your previous question (What should I do to fix that pad?)?
This board has a lot of damage, you have multiple pads that ripped off the board, including the pads for the two capacitors. This is a sign that you are pulling the IC before the solder has molten completely. I'll restate what I said in the previous Q:
Pulling an IC before all of the solder is molten will pull pads. You have to insure the IC floats on the molten solder. You can do this by gently tapping the IC to see if it springs back. Also, avoid wicking. These pads are simply too small and have very little adhesive and copper holding them in place.
What kind of equipment are you using and what temperature and airflow settings are you using? Everyone develops their own style, microsoldering is as much an art as it is a science, but there are some ground rules you have to follow:
Obviously, too much heat can cause damage not only to the IC you are replacing but also the surrounding area and the flip side of the logic board. Sometimes passives get disconnected electrically even though they look okay. Those that are encapsulated in underfill are more prone to that.
Also, when testing for "float", we can sometimes nudge the IC too far and cause a solder bridge underneath the IC, shorting out pins that can cause all kinds of problems.
Finally, practice on dead boards until it works well. Don't "learn" on customer devices.
War diese Antwort hilfreich?
As for this board being recoverable...doubtful but maybe (I'd have to check where all the missing pads go). The thing is, if your technique isn't ready for properly pulling IC's, then it certainly isn't ready for doing the kind of micro-jumper work required to possibly save this board.
We all learn by making mistakes so don't put yourself down. Learn from it! But I would highly recommend you purchase some dead or iCloud locked phones and practice removing and reballing IC's until it feels natural.
Hi there, thanks for your responses. Yes it's the same phone.
The strange thing is that I was able to put solder on those spots, but wanted to rectify some imperfect spot, by the 2 capacitors. So I ran the tip of my iron around that spot and the solder spots all disappeared and the whole layer got torn off.
It seems things can go wrong very quickly with just one gesture over a seemingly empty spot.
I can't figure out how long does the heating have to be to secure the newly placed chip with a 360-380C? Tried to see from Youtube videos, but it's harder to assess when you're doing it by yourself.
Yeah, the videos make it look deceptively simple. Remember that those videos are often done by techs who master the process. They also had to learn one day but they weren't making videos of it.
Based on the damage I can see, it looks like you damaged the physical pcb when pulling the IC. Running your soldering iron over it just loosened and removed the top layer that was already compromised.
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