Hey there,
thanks for the new thread providing a good overview. I’d like to share my personal experiences from oven reflowing multiple Fairphone 3 boards with a good success rate and several months lasting (most of them up until today 1-2years):
For reasons of the already mentioned temperature profile and to minimize the smell, I wrap the mainboard in normal grocery aluminum foil. Then I preheat the oven to 180°C and place the mainboard for 20 minutes inside with air circulation.
So far I couldn’t see a difference for the outcome regarding the side which is placed upwards (also didn’t put much attention to it).
Remark 1: Normal ovens have an unprecise thermal management. Using an external digital thermometer for meat I measured ca. 185°C in my oven when it was set to 180°C. This can obviously differ in both directions.
Remark 2: After the oven reflow you can test your board by inserting it in the frame, only connecting the bottom module, insert battery and try to power it on or plug it in the charger. The bottom module will vibrate if the mainboard works again, even without a screen.
Remark 3: I don’t intend to start a discussion here about the perfect temperature and time for oven reflowing. I just wanted to report my values which provided me with good results.
Since I didn’t have 100% success rate I ordered the chips which are in question of causing the sudden death (mainly Qualcomm PMI632 902 00 and to be sure Qualcomm PM8953 0VV and will use a community workshop (fablab) to try soldering the new chips on. I do have experience in “normal” soldering and will post a short howto in this thread if I succeed to revive the mainboard.
Kind regards