Make:

I had to whip up a bunch of these for my sister. I ended up doing mine "end mounted" as well, as opposed to having the LED sit on top of the beads. I'll have to try the tape method, when I did it I used toothpicks to move everything around. I'd do about 10 in a batch, put all the beads on their side, put a small blob of solder on a side of each one, then tin both sides of the LEDS.

With the LED facing down, I'd grab a bead by sliding my iron into it and tipping it over, drag it over to the LED, and then use a toothpick to hold the bead in place and slide the iron out once it made the connection.

Oh yeah, I also picked up a pair of reading glasses (~2.5 or so), they make work like this sooooo much easier! Hope you follow up with how well they work out, my sister said there was about a 30% breakage rate. I tested them all before I sent them to her, so I don't know if she was just sewing them too tightly, or if my solder-fu is weak...

Reply to this comment

That does look pretty cool, so you just use conductive thread to sew them to cloth after soldering the beads?

@Peter - From your description, you're probably producing cold solder joints which could explain the breakage rate. Though given the tiny sizes I doubt there's a perfect method to solder these at home.

Reply to this comment

Yeah, I try to leave the iron on there long enough to see it all turn to liquid and give it a five count after that or so, but next time I'll try it w/o tinning the LEDs.

And for the conductive thread, she was having serious problems until she moved to the two-ply thread, said that was tons easier to work with. You probably don't need resistors when using the thread, as it usually offers enough for LED purposes.

Reply to this comment

Posted by: Mike Estee on September 17, 2008 at 11:13 AM

@Peter - I don't know if there is a good solution for breakage. The joints are pretty small, and the thing that normally makes them strong is being attached to a unified flat surface. It would be possible to make a very large number of thin PCB mounted parts, but you'll have to find a way to cut them out. Normal routers would just vacuum them up. Laser might work, depending on what the PCB is made out of.

However! If strength is really an issue there is a somewhat complicated and messy solution. Epoxy the backs with a drop of glue. The glue should span the back of both beads and the LED. Once it hardens it will be less likely to break.

I've also found that crimping the crimps down will weaken the joint further. I don't recommend it, even if it does make a solid electrical connection.

Reply to this comment

Here's a crazy idea, not sure if it would work but if it does it might speed this up a bit:

Super-glue the beads to the side of the LED, then apply solder paste to the bottoms of the joints and use hot plate reflowing such as http://www.sparkfun.com/commerce/tutorial_info.php?tutorials_id=59

Reply to this comment