No Power and Reflow Options

Working for a very small company that works on iphones and other things. We don't have all the resources we would like, but most of the time we make due. Just recently we've begun to do some logic board work.

Currently have a stack of iphones that won't power on.

1) tested batteries

2) tested charge ports

3) tested cables and charge blocks

4) tested without batteries

At this point we have eliminated everything but the logic board itself. We don't have the resources to replace resistors, filters, diodes or triodes, but we can do spot reflow using an Aoyue Int968A (we don't have an oven to just reflow the entire thing).

If you can't tell, I am brand new to this level of repair, so forgive me if I say something off or confusing.

So far what I've been able to read generally points to the Power Management IC. I've tried to heat it up to 220 Celcius for 5 minutes on several boards, but no dice.

Would this mean that there is another chip/diode/resistor/filter/etc I should be looking for? Or would this reflow method simply not work? I got it to work on another issue (5S BSOD, just hit the trouble spot the same way and it seems to get the device working again, most of the time).