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IPhone 12 ProMax - Thoughts of (not so young) apprentice

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    IPhone 12 ProMax - Thoughts of (not so young) apprentice

    Hi guys.
    I'm working on my first board reballing.
    It's iphone 12 pro max and I made a mistake(s), but now to learn something, I hope.
    Either I overheated the board and two ics fell off on it's own, or I clumsily took of top board and knock them off. Adrenaline was high at that moment so I do not recall best.
    I repaired the damage by putting these components back in place. In some moment I begin tinkering about my future steps and about the fact that I have used low melt solder (138C) to put those components back. My line of thoughts was something like, if I use same solder on ics and sandwich pads components will fall off again when I start heating the boards. I decided to desolder ics and use higher temperature solder and that's where things go south.
    First I knock off small cap, which jump out of my tweezers to abbys and when I looked at boardview to find info for that cap I found out that much more components are missing, compared to a boardview.
    Questions:
    - Did I lose all that components when heating for separation and they mysteriously vanish or it is common thing to these boardview files are somewhat different?
    - How do I need to repopulate a board for it to work?
    - What do you think, was my idea about not using same solder unnecessary?

    #2
    Let me answer to myself, if future someone have same dilemmas.
    - No I didn't lose all that missing components. In the schematics, some of components have "nostuff" comment. That basically means that component will not be present after assembly. These components are sometimes flagged as DNF (Do Not Fit), DNP (Do Not Populate), etc
    - Cross reference board view and schematic to see what is there.
    - I think that in the moment of solder melting temperature at sandwich pads are bit higher then contact points of IC at upper board. Even if temperatures are the same and solder underneath the IC is melted, surface tension will probably hold IC in it's place.

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