It was but two weeks ago when I told my story of woe — the tale of an LG Nexus 5X that fell ill, seemingly due to a manufacturing fault at birth. I managed to disassemble it and made my way through a semi-successful attempt at repair, counting on a freezer and hairdryer to coax it back to life long enough to backup my data. try as I might, however, I simply couldn’t get the phone running for a lot more than ten minutes at a time.
All was not in vain, however! I was rewarded for documenting my struggles with the huge experience and knowledge of the broader Internet: “Hairdryers don’t get as hot as heatguns!”
It turned out I had just assumed that two similar devices, both counting on a hot bit of metal and a fan as their primary components, need to be essentially identical if rated at a similar power draw. I was wrong! apparently the average hairdryer stays well cooler than 150 degrees Celsius to avoid melting one’s silky locks or burning the skin. I even learned that apparently, wet hair melts at a lower temperature than dry hair. who knew?
Armed with this knowledge, I rushed out and gotten the least expensive heat gun I could find — around $50. Rated up to 600 degrees C, this was absolutely going to be hotter than the hairdryer. With the prevailing opinion being that I had not applied enough heat in general, I made a decision to also increase the heating period to 90 seconds, up from a quick 30 second pass originally.
After a quick disassembly of the phone, I was ready to go again. With the motherboard pinned down between some books to stop it skating around my desk from the airflow, I aimed the air mostly at the greatest chips on the board, being sure to step it around to avoid overheating any one spot and dislodging parts.
Lo and behold, it worked! The phone fired straight up, with a clean boot. even though I’d had the phone previously fail in the middle of an update, there were no problems at all. I was able to fire up Google Photos and set it to back up the last of my photos to the cloud, and left the phone to do its work.
Welcome Back a Dead Nexus 5X
Over two weeks have now passed, and I am delighted to report the phone is still fully functional. While I no longer use the phone day to day, it has survived occasional web browsing as well as a anxiety test of swiftly taking 17 photos with HDR enabled to see if putting a load on the processor would cause the problems to reappear. The mechanism of this repair still isn’t 100% clear to me — is the hot air gun causing the BGA solder balls to reflow, or is it some other kind of thermally-related witchcraft? Pontificate on this in the comments. To me, it feels like solder rework. Admittedly I’m not using best practices for hot air rework. Bil Herd has a guide for SMD desoldering without damage to components. His techniques can easily be adapted for reflow without removing the part from the board. A better method would be to remove and reball the BGA chip, but that is beyond my current capabilities.
It was a pretty satisfying fix in the end. It’s a good feeling to have a working phone at the end of it, rather than sending a lot more electronics straight to landfill. Of course, my unreserved thanks go out to the Hackaday and Youtube commenters who pointed me towards the light… or in this case, heat.