Several hours of work, and this sort of stuff is born… 16 new JeeNode USB’s:
It looks pretty, but I’m not going to show you the high resolution picture… even on this one you can probably spot one or two problems :)
The fact is that hand-assembly of SMD takes a lot of patience. By now, I think it’s absolutely doable for one-offs, such as to assemble one board with some parts. But larger quantities do tend to bring out the trouble spots.
Usually, on a run this size, I’ll expect to see 3 or 4 boards not working right away, and ending up with perhaps one board which I can’t fix quickly. I’ve got a box with a bunch of units by now, which don’t seem to want to be cured. Oh well, their loss – that means they get to wither away in a dark box, waiting for better times :)
Especially the mini usb are a problem when using reflow, my last board had a short at the beginning of the pin which was covered by the body of the connector. So there was no chance to correct this. Meanwhile I do not reflow mini usb anymore. On the other hand, I reflowed 5 melf ATMega 168 and 2 Bmp pressure sensors and the all worked immeadetly.I was very impressed, maybe I was lucky.
Cheers Rubi
I’ve used hot-air desoldering occasionally to fix that sort of issue. But that too can be tricky – before you know it lots of parts come flying off the board :)
Ya …. the hand assembly gets old pretty quickly. It’s perfectly doable for prototyping (I even place the solder paste by hand with a syringe and the microscope), but it takes me about an hour to make a moderately complex board (30+ parts). If there are bridges they have to be removed, plus washing/drying/inspecting, etc. It’s a great skill to have in the toolbox (I’d even say essential for small shops) and can save a lot of money and time in the prototyping phase … but it’s definately a case of picking the right tool for the right job. Prototyping, good. Even small scale commercial assembly, very bad. I’ve put together a few dozen variations of boards like this the past months and I always dread making new ones: http://www.microbuilder.eu/Projects/LPC1343ReferenceDesign.aspx
A solder paste applicator and pick-and-place robot would be a great (and ambitious) project. Regardless how slow they do their job – for one-offs and hobby use it would still be a huge convenience. Who knows, maybe some day…