(A) solution to the Nexus 5X Bootloop failure

As you know I am a fan of the Nexus line of phones that LG did for Google.  My test piece is a Nexus 5X (one of the first with USB-C Fast Charge…) and the phone is indestructible by all rational accounts.

NOTE:  This is a Pass/Fail test where we ask only:  “Does it still WORK?”  Y/N

It has survived:

  1.  A fall into the Puget Sound
  2. Many skittering skitters at 25mph off an ebike
  3. Many falls at every angle you can think of (100ish?)
  4. All the glass broken out of it
  5. Multiple disassembles
  6. Of course it is rooted with whatever random crap I could find (including my own crap) installed on it

This phone is a solder…  but…

This time I caught the BoOTloOP (AHHHHHHHH!)

Onward…

You can do your own research…  but it is commonly agreed upon (wich is worth exactly SHIT without a proper test…) that the failure mode is Hardware Based.  My failure happened during a “high heat” period after a “long time in the hands of a 5yo) so…  I am pretty sure I understand the failure mode.

Its a hardware failure…  (even tho technically just taking it apart did a reset…  but stick with me on this)

So we clear the table of the kid projects (explains the background…)

Phone comes apart clean…

An engineer notes that all of the fasteners are of EQUAL SIZE and that they are all pre-hit with loc-tite.

If you dont have a BAG of screwdrivers like this…  then this may not be the activity you want to get into.   Just let it wash over you.

The flat-flex assembly picks apart like beautiful little scabs…  Pick them ALL or rip them on the way out.

That’s the front facing camera…  amazing…  how much would that cost at the Spy shop in San Francisco???  Probably $500 + $200 in add-ons.

Yes my hands are filthy.  We brought a 2001 Prelude back from the grave over the last two days.  Those snaggly fingernails are called “tools” and I intend to keep them until our Schindler Engineering camping trip is completed.

Ah HA!  Just as easy as that.

See that USB-C plug…  that’s the one you want to support…

Now..  for some history…

THAT is corrosion.  Maybe Aluminum Oxide…  maybe some sort of tin…  du’know…  but I can tell you its from falling into the salt water and then seeing electricity, moisture, and warmth.

The corrosion above is why we do the solvent soak below.  Without writing pages…  things fail because…

  1. There is no conduction where there should be conduction
  2. There IS conduction where NO conduction should be

That pretty much sums up every failure mode there is…  at the root…  they are mechanical in nature…  and even a thermal failure is mechanical (as is electrolysis to my thinking)

So…  we are going to absorb any salts on the board.  Normally I would like to soak it in DI (DeIonized water, then 99% ISO, then bake…  but we have what we have on hand)  —  <different impurities absorb into different solvents…>

This is what I have to work with.  Its the standard stuff from the drug store.  For killing bugs you want to use 70%.  For cleaning circuit boards you want to use something higher than 90%.  If you see 99% on the shelf buy 5 of them.  What I have is 9% water…  and thats fine…  as the isotropic mixture will do fine absorbing all the nasties on the board.

But…..  before we jump the gun…  we need to open up the little water-catchers.

Those coverings can serve MULTIPLE PURPOSES…  so pay close attention!

Notice that this cover has polyimide tape… (which is often used as an electrical insulator that thermally conducts…)  but more importantly… it has what looks like a thermal conductor pad to me!

That little square sponge touches one of the chips and it spreads the heat…  so…  yes these are for FCC compliance but they are also HEAT SPREADERS.

Spread your heat or be sorry   !

Now..  back to cleaning the boards.  Just SOAK THEM, agitate them, brush them if you must.  This is a normal part of the process and every part on the board must be sealed (including the buttons…  I hope/presume)

Skip the part pictured above and think hard about the step listed below.  One involves a proof which need not be proven…  and one involves… possibly…  superstition.

(well…  we always stand our Construz Jesus in the pool of solvent while trying a Hail Mary…  and it always works…  so…  )

Wrap it up tight buddy…  those iso fumes will give you a headache.

With it wrapped up tight you can agitate the crap out of it.

I have seen some bozo’s use Aluminum Foil for a base while attempting to reflow in the oven.  Think long and hard about the logic of reflowing over metal.  Just …  does not make sense to me…  even if 99% of the time it wont be an issue.  I just use silicone or FR-4…  in this case Pyrex (borosilicate glass)

I did a quick pre-dry with a hair dyer, set the oven to 390 (which is an early reflow temp) and tossed it in there until the oven beeped.

(This is not rocket science…  you cant be an idiot about it…  but you don’t need superstition.  I have done a lot of reflow work…  so I have the magic touch.  Don’t burn the silk screen and you are pretty much fine)

Now…  dont get all YouTube on us and think that you are actually reflowing BGA’s here..  with no flux…  with low temps…  come on…

At BEST something is re-seating that was twirked or something along those lines.  Some sort of kissing contact…  or …  some cracked conductor moving a micrometer…  its something that you DONT WANT TO KNOW ABOUT…

But what you SHOULD KNOW>….  is smothering the border of a BGA with flux then blasting it with a hair dryer is NOT anything more than triple P.

So if you are reading this in the future…  and your phone is all taken apart…  and you are looking at the picture above (which should be rotated 90 degrees…  grrr…) you have possibly lost your faith.

In programming we call it the Leap of Faith when viewed thru the lens of recursion…  but if you like you can call it just faith

Ok… so…  while you are looking at that jumbled pile of parts…  feeling fear and anxiety… just tap into whatever faith you have.

Maybe its bold confidence.

Maybe its a Construx Jesus.

Maybe its Buddha, Jah, Flying Spaghetti Monster

Dont know, dont care…  you believe what you want to believe…  I believe what I want to believe…  we dont fight…  we work together…  we win.

Simple as that

Now…  to fold back  (thats a trick professors used to either confuse the hell out of you or be sure you absorb the information…)  Here is some closeup work of those HEAT SPREADERS

 

See that little foam pad…  its not there to hold the chip on…

Those spots match and if they are not touching then you ARE going to have overheating chips.  Dont EVER assemble a phone without its heat spreader.

SERIOUSLY..  WTF Youtube?  (jab at a few videos I watched…)

All tight and buttoned up.

At this point you might as well go for broke and fully assemble…  as it either WORKED or it DID NOT WORK and further fussing probably wont help.

SINCE I have skill, experience, and faith in my abilities…

My fix WORKED

(Not that I needed it since I already had full backups run thru Google.  Yes…  that gives them and the NSA free run at your data.  YES they do dig thru it in 32,768 “anonymous” ways that SHOULD protect your privacy UNLESS you match a profile…)

Now…  Profile matching…  that’s a $50,000.00 post.

Want to know what happens when your “randomized and anonymous data” hits a high match with search algorithms intended to identify threats to the <US Government As It Stands> (er…  I mean “National Security”)?

Lol…  You get your privacy invaded without a warrant and without warning or notification afterword.  You either know that or you dont and I dont really care.

Schindler Engineering wants you to succeed whether you want to or not.  Just accept the surveillance state…  dont struggle too much…  and soon we will have you settled into your pod so that we can suck your juices and keep you busy.

Lol…  (I live in Santa Cruz)…  We actually have “Chem Trail” meetings posted on street corners, UFO accounts, people who think they can smoke pot all day and improve their work performance…  wtf?

Until next time. . .

Eat your greens, get your exercise, pay me on time, and keep it real.

Schindler Engineering is going into Cold Storage for a year or a decade.  When we return…  it will be with a vengeance…  So look out crooked politicians, authoritarians, and non do-good’ers round the world.  Our first order is to “Do The Right Thing” and our second order is to “Get Money, Get Paid”.

-Patrick