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Solved Desoldering tips/tricks?!!

kilroy07

Well-known member
#1
Okay, I won't repeat the words I used when this happened last night...
I was just wrapping up soldering up my brand new Mateksys F405-Wing FC when a blob from a connector (XT60) dropped right between the two ICs!!!
:eek::mad::mad::mad::cry:
IMG_7785_LI.jpg


I got most of it cleaned up with braided desoldering wire... and I have a desoldering pump (although it's too tight to really get in there with that...)
Sigh...

So, does anyone have a tip/trick for cleaning this mess up?

If not I'll probably try again with the braided wire tonight... (I had to walk away from it last night....)
 

Brett_N

Well-known member
#3
Got any copper stranded wire?

While I love braid, soemtimes copper wire (especially if it's fine strand) works better. Just strip about 1/4" back and use it like a small bristle brush - you can heat the wire instead of the board.
 

d8veh

Well-known member
#5
I haven't tried this, but I would if I were in the same situation as you. Get the smallest desoldering wick you can, like 2mm or smaller. Bind a bit to your soldering iron with some copper wire so that it just level with or slightly overlaps the tip. Dip in flux, then attack the rogue solder.
 

Keno

Well-known member
#6
I have been soldering for over 50 year repairing electronic equipment. I really don't want to be in your position as it is not good. All You can do is try what has been suggested and clean up the mess the best you can. Sorry to say that. What I have resulted in doing is to after getting as much to the solder off as you can then you can use your hobby knife to scrape off the areas that appear to inter-connect. The problem is new electronic modules are so small they are really hard to see to repair. A magnifying glass is a necessary tool. I had to leave my work as things became small the my soldering iron tip became larger than the distant between that a circuit board ic's connections. Try what you must you have noting to lose, the end result may result in the necessity to purchase of a new module. I wish you success.

Edit: the word "scape" should be "cut" and do not use to much pressure otherwise you could lift the circuit traces, not a good thing.
 
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PsyBorg

Wake up! Time to fly!
#7
If you have sucked of / wicked off most if the blob and are down to small bridges you can carefully use a dry (not tinned) tip to pull the solder out from between the pins.

If you have a temp controlled iron turn it up a touch more then what you normally solder with. Use some flux on the dry tip and you should be able to get the solder to draw in to the tip and separate between the pins. Drag the tip in a straight line away from the chip in line with the pins.

The key use enough heat to melt solder between several pins and a super clean tip with less solder then the area you try to clean up and it should follow the heat.
 

kilroy07

Well-known member
#8
Thanks everyone for suggestions and support.... I was really (REALLY) upset when it happened (I know better!)
Anyway, I believe I've got it mostly cleaned up (down to two pins... (I hope).
IMG_7793_LI.jpg


I'll take it slow and double check everything before I apply any power... (Fingers crossed) I might have this installed on my Kraken by the weekend.... It's my newest, favoritist, FPV toy! :D
 
#9
You didn't accidentally remove a couple of tiny surface mounted components, did you?
Looking at that photo, it looks like there should be a pair of components just off the large IC.
Man, that is a tough position to be in. Not really much you can do but try and keep your fingers crossed. Good luck!
 

Brett_N

Well-known member
#10
Those look like 0-ohm resistor jumper connection points. (Typical on flight controllers)

For the pins - get a really really sharp exacto blade and run between the pins. if you've got a helping hands thingy, you can even heat the tip of the exacto with the soldering iron.

most of the solder we use at home still has lead in it, or at a minimum is a lower temp melt than what's used in production by about 50*C
 

Bricks

Well-known member
#11
What I have done in some instances is use a compressor and air nozzle get the solder hot then hit it with air trying to direct it away from everything else. Usually small pieces of solder will spray some but they do not really stick the tip of an Xacto knife usually pops them off.
 

makattack

Winter is coming
Moderator
Mentor
#12
I've seen it mentioned above a suggestion about using flux. I would 100% agree that the flux can make this an easier job to fix and cleanup. I would use the flux paste, spread on those pins with a toothpick, then very quickly with a clean solder tip that's tinned (but not with too much solder) run it quickly along those pins. The flux should help the solder reflow and stick only to the contact pads. Clean the flux residue up afterwards with some isopropyl alcohol and some lint free cloth (or cotton swabs if that's all you have)
 

kilroy07

Well-known member
#14
You didn't accidentally remove a couple of tiny surface mounted components, did you?
Good eye... SIGH.... YES, it looks like I did.
I thought they were just test pads or places to make a solder bridge (the 405 has a bunch of options like that...)
F405-WING_3.jpg

Must have happened with the first big blob removal...

Well, gosh darn it... :mad::mad:
Looks like my FC project is on hold until I can find out what those are are get some replacements....:cry:

Man... Just when I thought I was back on track...
 

Brett_N

Well-known member
#15
Un-solder your VTX and probe the voltage. Those look like zero-ohm resistors to me. usually they use solder pads AND 0-ohms...

I can't read the chip that's upside down to the upper left of the resistors - if you can let me know what that is, I'll see if I can find a schematic - maybe it's a power chip. Or see if you can get a good picture of the underside of those pads - there must be a variable V-out switcher somewhere, we just need to figure out the resistance values (I'll bet 100ohm or 10Kohm - Thank god for Digikey!)
 

Brett_N

Well-known member
#16
I did a little googling - will your FPV work with 5V? I'll betcha dollars to donuts even with those 2 resistors missing you've got 5V vTX working.
 

makattack

Winter is coming
Moderator
Mentor
#17
Err... I think they're caps... they are the yellow/ceramic colors looking SMD components right?

Here's a zoomed in clip from the vendor page:
http://www.mateksys.com/wp-content/uploads/2018/04/F405-WING_Layout-1471x1500.jpg

I can't find any online schematics, though some of the folks at the RCGroups thread for this board might be able to look at their boards to help you out:

https://www.rcgroups.com/forums/sho...ek-F405-WING-Flight-Controller-iNav-ArduPlane

Alternatively, maybe the iNav folks can help on related / similar boards:
https://github.com/iNavFlight/inav/blob/master/docs/Board - MatekF405.md

If you think they might be in your solder sucker, or your soldering iron cleaning pads, you can try looking there and they might still work if you resolder them on!
 

Attachments

Hai-Lee

Old and Bold RC PILOT
#19
Just a heads up for anyone doing soldering away from the properly setup soldering station/work bench.

I used to work on ATC radar a long time ago and it would not fit on the work bench so repairs were often done deep in the bowls of the equipment at times often over HV circuitry.

TO prevent such issues as experience in this thread we used to place either a tray/plate or even a sheet of paper under the work area where the soldering took place. this caught all solder blobs, flux spatter, and even strands of damaged wires from reaching areas where they could do serious damage.

I still use the old sheet of paper if I am required to take a soldering to a model aircraft to change battery plugs or whatever. I always solder my motor to ESC connections so if reversing a motor it requires a soldering iron intervention. So far I have NEVER had an issue with unwanted and accidental shorts because of my soldering efforts.

Just something to get used to and a simple method to avoid disaster in future.

Have fun!
 

Brett_N

Well-known member
#20
I'd still un-solder or disconnect the VTX, plug a battery in and see what voltage you have on the VTX pin.

I did find a close up on google - they are definitely resistors (black) but too small to read the resistance value. The power part right next to it doesn't come up in any searches that I could find so it's probably some Chinese knock-off PMIC