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Looking for some advice on attaching a USB cable to a USB drive of which the original USB connector has snapped off. It has a bunch of my girlfriend's coursework on it and of course she has no backup...

I have a reasonable foundation knowledge of electronics but am a bit hazy on PCBs.

From what I can make out from the image below, there are 4 solder pads for the 4 terminals of a USB connector. The connector simply solders onto these pads. Normally this would mean that I can simply reflow the solder to reattach the connector.

However in this case, I think that the solder pads themselves have broken away from the PCB as the material exposed seems non-conductive. With this in mind, the next logical thing is to try and expose some metal from the PCB wiring and solder to that. You can see in the image that I have started to do that with the leftmost terminal.

Both this and the rightmost terminal will be okay in this sense but I can't actually make out where the PCB wire is routed for the middle two terminals to scrape away at it.

Was wondering what people would suggest as a means of connecting into this? It's not got to last, just needs to survive long enough to pull the data off of it.

I have also included side and back images for reference.

Any and all help would be appreciated, thanks!

Front Side Back

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  • \$\begingroup\$ Personally I'd get another connector, or try to solder the old connector back onto the pads. Where is the old connector? Looks like one pin may be damaged but the other 3 may be OK. You may be able to desolder a connector off of a similar drive. \$\endgroup\$
    – Ron Beyer
    Nov 1, 2017 at 15:37
  • \$\begingroup\$ Thanks Ron, I do have to original connector but the issue with it is that the solder pads are still soldered firmly to the leads of the connector, its actually the bond between the solder pad and PCB that seems to have broken. I had tried securing the PCB and the connector together so that the solder pads were making contact with the PCB but no avail there. \$\endgroup\$
    – Jacob King
    Nov 1, 2017 at 15:44
  • \$\begingroup\$ Have you tried to solder the connector back on? Is there metal material left on the pads on the PCB? Just pressing the pads together probably won't work (well), to get the better connection you'll need to solder it, I'm guessing the solder joints broke off and are on the connector, but looks like the pads are still on the board. \$\endgroup\$
    – Ron Beyer
    Nov 1, 2017 at 15:47
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    \$\begingroup\$ I believe only the rightmost pad is still on the board, the other 3 pads are still attached to the leads of the broken off connector. I would take a picture but I unfortunately don't have it to hand right now. The 'pads' that you can see on the leftmost 3 aren't conductive; I'm assuming it's the base material of the PCB. \$\endgroup\$
    – Jacob King
    Nov 1, 2017 at 15:48

2 Answers 2

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Three of the four pads ripped off the board along with the connector. You will have to very carefully scrape the resist and connect to the vias for the D+ and D- lines as shown here:

enter image description here

The colors notated above are the wire colors you'll find in most USB cables if you cut off the "B" end and expose the wires.


EDIT: One way to make the resulting assembly a little more rugged would be to use another board as a strain relief for the cable. Hopefully, this sketch makes sense:

sketch

Get a piece of pad-per-hole board or even just perfboard, and tape the USB board to it, after putting something like a piece of cardboard or tape between the two boards to prevent shorts. Solder the wires from the USB cable to individual pads on the bigger board, and then use single strands of very fine wire to make the final connection to the USB board.

This way, any movement of the USB cable relative to the larger board won't put any strain at all on the delicate connections to the USB board.

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  • \$\begingroup\$ Thank you so much for the very helpful diagram Dave, I really appreciate it. Do you have any advice for connecting to the vias? Given the extremely small surface area I have to work with? \$\endgroup\$
    – Jacob King
    Nov 1, 2017 at 16:14
  • \$\begingroup\$ Be very, very careful! You can't afford to lose any more copper. The other end of those vias are hidden under the chip on the other side of the board. They undoubtedly connect directly to two pins on that chip, but you would have to use an ohmmeter to figure out which two. If you can do that, it may or may not be easier to solder directly to the chip pins. \$\endgroup\$
    – Dave Tweed
    Nov 1, 2017 at 16:17
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    \$\begingroup\$ Note that the place you scraped is NOT Vbus! Connect to R1 as suggested by @peufeu. (I updated my diagram.) \$\endgroup\$
    – Dave Tweed
    Nov 1, 2017 at 16:24
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    \$\begingroup\$ This is going to be a very fragile assembly so if you get this to work take all the data off in one go and back-up anything you are not prepared to lose. Unfortunately my experience of IT (or BS) support is we have two sorts of users: those that have lost important data and those that will. \$\endgroup\$ Nov 1, 2017 at 19:21
  • \$\begingroup\$ @WarrenHill: Good point. See my edit above for one way to mitigate the fragility. \$\endgroup\$
    – Dave Tweed
    Nov 1, 2017 at 19:46
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Good luck with this one! The two centre pads connect to vias that take the signal through the board to come up under the chip on the other side and connect to a couple of its pins. I've sketched the original copper out in pink and blue here:

enter image description here

Obviously all that's left of the tracks are the surrounds of the vias, you'll need to very carefully scrape the solder resist away and solder to them. I'd be tempted to try using a drill bit very gently turned by hand rather than a knife or scraper. Take it slowly!!

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    \$\begingroup\$ +1. The 1R resistor provides a nice soldering point for the missing pad on the left. The two vias end up underneath the chip on the back, so this is going require subtlety! If you carefully scrape off the soldermask and manage to solder 1 strand of your multistrand copper wire it should be OK. \$\endgroup\$
    – bobflux
    Nov 1, 2017 at 16:06
  • \$\begingroup\$ I'm trying to determine whether the Vbus connection runs through the pad to provide a circuit all the way from the 1R0 resistor to the track above the pad, or whether the missing solder mask on that bit of track is a coincidence. I can't be certain. \$\endgroup\$
    – Finbarr
    Nov 1, 2017 at 16:17
  • \$\begingroup\$ Looks like it does, also having a RC filter with the 1R resistor and the cap on the right makes sense, but OP should check with a continuity tester, if the probe is sharp it's possible to probe where the track was torn off... Also if it's not possible to solder into the vias, but you can get enough soldermask off to probe, you can find which pins on the chip on the back match the torn pads... \$\endgroup\$
    – bobflux
    Nov 1, 2017 at 16:21
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    \$\begingroup\$ very good luck with this and do note if you get it wrong you're sleeping in the dog house for a month :) \$\endgroup\$
    – Solar Mike
    Nov 1, 2017 at 16:46
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    \$\begingroup\$ @JacobKing worst comes to worst you could purchase an identical flash drive and swap the flash chips but you should be OK soldering thin wires to the vias if you take it nice and slow. Also teach your GF about backups. Never mention your backup GF though. \$\endgroup\$
    – bobflux
    Nov 1, 2017 at 19:56

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