USB Power Supply Contacts

[argon]

I can't believe it's been nearly two years.... Well, stuff happens. Anyway, I have to report: SUCCESS
Thank you, Dave9. I could not have done this without all your advice.

After getting my soldering station, I bought a Solder Practice Kit (ELENCO, Model SP-3B). This was a terrific way to improve my soldering skills as well as introduce me to various components, terminology, etc. There was nothing, however, that mimicked the small size of solder joints I needed to create; those pins are only about 1.2 mm long x 0.3 mm wide. Here's a photo of my prep after using JB Weld epoxy to secure the mini connector:



I bent the (left-to-right) 4th pin up and out of the way. I did want to connect the #2 & #3 data pins. Skinny little traces for those... I chickened out using a Harbor Freight heat gun with soldering paste. I soldered the outside pins conventionally without much difficulty. Those middle two pins were another matter. I tried to apply soldering paste and the swipe with the iron; got a nice little trace adhesion on pin 3. I ended up trying to hand solder pin #2; I thought it was a disaster, and I couldn't remove the solder to give it another try. But, I figured I'd see if the bluetooth speaker would work before messing with it any more. I attached my power cord and the red LED lit up! I was getting some intermittent disconnection, so I soldered the two tabs of the connector to the PCB; improvement. The speaker and my iPhone seemed to pair, got the typical connection chime. But my iPhone reported failed connection. I figured those data pins were shorting out, being connected (apparently by a big gob of solder), preventing proper connection/handshaking of the bluetooth protocol. I was about to fire up the iron and work on it further, when I realized that I selected the wrong bluetooth speaker on my iPhone! No wonder I failed to connect. I did connect without difficulty, played a few songs, changed songs, adjusted volume. It's good. Here's the post-solder result. I'm surprised the speaker works:


I suppose that job looks somewhat laughable to you guys, but those pins and traces are very small. Anyway, I'm pleased. If I had to do it all over again I'd use paste for all connections and use the big heat gun (saw a YouTube video). I'll probably buy some other small kits and continue with this. Next up, however, is replacing the wiring harness on a guitar; should be easy with the required "macro" solder connections (vs. what I've been doing lately).

Thanks again, Dave9

 

[dave9]

Glad it works! Be careful with heat guns around connectors with plastic inside, can melt them so it is handy to have a sheet of mica to put between, shield and keep the heat away. I would just avoid using a heat gun with the plastic so close.

The main thing I would do differently, is I would have flooded the area with liquid flux, then put a bit of solder on the tip of the iron, then slid that across the target area, not try to feed a piece of solder wire in because it is easy to end up with too much solder that way.

Now if I were you, I'd put more epoxy around the connector, after cleaning off any remaining flux residue if there is any, being careful not to let any epoxy get inside the connector. There are also tricks for that, in tough situations you can coat the charger cord in grease or petroleum jelly, plug it in, then epoxy won't get in enough to matter, then once the epoxy has set you can unplug the cord, and flush out the socket with your choice of petroleum solvent or electronics cleaner, etc.

 

[argon]

Thanks for the advice. You know, I tried and tried to get melted solder at the tip, but it always tended to "pool" (in a football shape) enveloping the tip but distant from the very end of the tip. I could never get anything--any excess--that could be easily transferred to a component. I found this to be very frustrating.

The smallest tip I had was a T-1. It was still, really, too big for my task. I thought (if I had to repeat the work) that I would try wrapping a stiff wire (like a paper clip) around a tip in a downward spiral and extending slightly beyond the tip proper, providing me with a new, much smaller tip. It's easy enough to do; I may experiment.

 

[dave9]

Yeah a tip that wets well is very useful, but it doesn't necessarily need to be a tiny one. The tip might've needed cleaned, or oxidized metal removed at which point it has a very short lifespan before you'd need to do that again as it means the plating is shot. This is one of the big differences with better quality soldering irons, that they have the iron tip instead of plated copper, but also temperature control helps to reduce the amount of flux that gets burnt up and causes residue on the tip.

If you flood the area with flux and just have a "little" bit of solder on a tip way larger than the joint, as it passes over the joint it will make the solder flow onto the uncoated metal areas. The key is don't put too much solder on the tip, and let the flux move it around. You can find a technique like this on youtube videos for "drag soldering" but in this case you're only dragging a pin or two at a time, if not trying to connect the USB data pins too.

You can also use desolder wick saturated with flux (some supposedly has flux built in, but often not as much as I'd like) and drag that across areas with too much solder to pickup the excess if there's a short.