So the rail isn’t shorted, (atleast not fully) and is in the realms of ordinary
Looking at your images it seems somebody has bady “reballed” this… and by reballed I mean tinned it with an iron. Given how close one side of the IC is to the board my best guess is the chip has likely fractured internally (and possibly a bit externally but hard to tell from the image) likely failing open, and the 1.1V your measuring on the rails output is likely just parasitic. I imagine the IC failed due to to it’s close proximity to the board and the rework you did on the M92 the opposing side (not your fault - ordinarily it’d be fine)
Yeah not much point in injecting voltage given that the rail is not shorted, that is unless the suspicion is an active short scenario (rare) For future reference, imo, I’d avoid “injecting” voltage so early on in the diagnosis process in future, your measurments prior ruled this out and as we didn’t/don’t know what’s going on below this now suspected IC (and how it’s failed internally) it’s just not worth it (even if you think 1.2V is “safe” which it largely is but in certain circumstances it can not be)
You can get them on mouser or any of the other big suppliers - I don’t remember the part number off the top of my head (sorry @coda you might be right) but I identified it on the forum ages ago which you should be able to find/verify with a search.
It’s easy when they’re preballed. don’t worry (even easier than the other IC’s you’ve worked on) - just pull the chip, tin the pads, wick them, flux, pop the new IC on and away you go
you got this, small BGA chips are simple installs my man. Id much rather install a 20 ball BGA than a QFN, I suck at QFN’s lol. Just remember to lower your airflow and hover above the chip farther than normal and then move closer. Its been my own experience that BGA’s tend to catch an air current easier than most.
Sorry missed this. You have to watch yourself getting ICs from China as while sometimes they’re fine - in the case of unmarked parts (for example if the listing just says “EN IC” then likely thery have no idea themselves what the part is and they’ll either be salvaged and poorly reballed or physically damaged or they’ll be a clone IC (or worse a re-etch/laser of an unrelated IC in the same package)… or they could be legit… it’s a coin toss. Given that you can get this at most legit vendors I’d opt for that before anything else…I only ever use Aliexpress/eBay China these days if I can’t get the parts from a legit supplier and/or I’m desperate, just not worth the headache.
Got a whole bunch of fuel gauges for Switch on Aliexpress ages ago. Literally no good reason to pull, reball, retop (in some cases) and then re-blister then ultimately resell… given how common and cheap the IC is new… but they still did it
Here is the topic where the IC was identified.
As for replacing M92/P13 no you should be fine, provided all your rails measure good (like we did earlier ) following replacing the EN IC en you should be fine.
Since I haven’t received the new ENXX for Switch #2, I got back to switch #1 and swapped the MAX IC under the SoC. I still get the exact same behavior (60 mA current draw at 15V, turning on and off when pressing the power button, missing 1V3 power rail) though. I might need to swap the fuel gauge now, or maybe there’s a chance my soldering was bad.
I followed your advice @Severence, @coda and @PhynxVT, and I think it went pretty smoothly, though. I also thought it was easier than large QFNs, @coda!
The whole board looks close enough in temperature so I wouldn’t worry about it, thermal cameras can send you down a rabbit hole sometimes
Also the 1.35v your missing is generated by the main power ic on the back of the board, the max77620H in this case, max77620A for v1 boards, not the max ic you’ve swapped
Note the two max77620’s are not swap-able, at least never worked for me
Yes, A and H are not interchangeable between board revisions,
The 1.35v could also be missing if it is a shorted line but I believe you checked for that?
Just for future reference. I can tell from your image that your iron was not delivering enough heat and you were pressing a touch to hard, for next time, apply barely any pressure to the wick, let the flux and heat do the work, if the pads aren’t winding up totally flat by the end (which yours aren’t) then suggests not enough heat in the board… if your finding your iron is simply not capable then use your hot air alongside at approx 150C to give it a helping hand. If your seeing the solder mask coming away (can be seen in your image) it’s indicating your pressing too hard on the wick.
It’s possible I suppose. as those joints don’t look amazing (you’d expect those balls to be as atleast as shiny as the lead free solder used on those caps nearby) but could also be your flux is coating them- it does look a bit smeary from the other images. What brand of flux are your using?
To add - Looking at the images, I don’t like the look of that resistor just below the IC, probably been hit a few times when you were wicking. It’s probably fine but I’d swap it out if it were me regardless.
Aliexpress, I ordered them before you warned me against it.
I could tell, my iron wasn’t hot enough. Actually to be accurate: my iron tip wasn’t big enough, so it wasn’t transmitting enough heat.
I’m slightly disappointed, as I thought it was a clean job, but obviously, the joints are not shiny.
Chipquik flux bought on Amazon. So far, pretty satisfying: easy to clean, easy to use.
I see trouble is this IC (and the fuel gauge) is just a shot in the dark based on the suspected likely impact damage. It might well be this IC is/was never to blame (it could really be any other IC incl the SoC but that particular Max IC was the most primary candidate), trouble now is were doubting the IC due to it’s origin. Did you happen to get a look at the balls on this IC before setting it down? one potential reason the joints might not look good is if the seller has reballed them as I’ve seen photos from others here from IC’s from China which either use junk solder or they aren’t even properly reballed.
I’ve not used the stuff myself but you will have to experiment reballing on some scrap boards using leaded solder and see if you can produce nice shiny looking joints on BGA style IC’s using this flux - just incase that’s the reason for the dullness in your photos above
Don’t be, it takes practice you’ll get better as time moves on. Practice on some other scrap boards, even if you don’t have stencils and paste just start pulling some chips off on the scrap boards then work on tinning the pads with leaded solder and try and wick said pads after (using your hot air if needed) - while bigger tips help, you can do just as good a job even with small tips using the tricks I mentioned. After, (and you’d never do this on a board meant for repair but just for practice) try tinning the scrap board pads then the IC pads and place the IC down, reflow, inspect your joints
Hey everyone,
I finally received what I needed for Switch #2 (and also work’s been crazy, so sadly not a lot of time to practice my repair skills), and I gave it a go today.
As a reminder, the EN chip was bad (or badly soldered), which resulted in the coil on the left shorting to ground.
Looking at the picture now, it’s pretty obvious the EN chip had been tinned instead of reballed, based on the quantity of solder (as predicted by your psychic powers again, @Severence !)
Wicked it clean, soldered a new one (easy peasy!), and… the switch is booting up again, yay!
M92 had been changed already, so I’m a bit lost on what to do next.
Regarding switch #1, I changed the fuel gauge with a new preballed one, but behavior remains the same. Not sure about my soldering on that one though.
For learning purposes, I tried reballing the old fuel gauge with 0.3mm solder balls I got from our infamous chinese website. It all went well until all the balls decided to merge together
I’d probably try another M92 just to rule out damage to the previous one prior. Check the reviews wherever your buying (and make sure they’re legit) there was a glut of fake ones at one point. If still no dice we’ll drill down deeper on this
I think whats happened here is not simply the balls joining together but rather I think you’ve stripped the “mask” (the kapton like enamel) which means your soldering iron was too hot these styles of ICs are far more sensitive to this than regular encased IC’s
Could well be - you can verify with your meter in continuity and check corresponding lines up to the slightly raised “pads” around the M92 IC
No the error would remain. While it’s not exclusive to the M92 I2C [corresponding] lines/pads this does seem to be the most usual cause for the error. Though as I say, this error is not exclusive to this IC or exclusively as a result of those I2C lines being open or closed at the M92 or anywhere else.
trouble is this IC (and the fuel gauge) is just a shot in the dark based on the suspected likely impact damage. It might well be this IC is/was never to blame (it could really be any other IC incl the SoC but that particular Max IC was the most primary candidate), trouble now is were doubting the IC due to it’s origin. Did you happen to get a look at the balls on this IC before setting it down? one potential reason the joints might not look good is if the seller has reballed them as I’ve seen photos from others here from IC’s from China which either use junk solder or they aren’t even properly reballed.
