From the MAKE Flickr pool
Member Macetech took on the challenge of soldering this teeny-tiny 3mm QFN-16 SMD chip. Those are 30AWG wires in the pic and the chip is an Allegro A6281 3-LED PWM driver.
Macetech does mention, “Note: this prototyping method is really not recommended for anyone with common sense.” Agreed! –Link
Related:
Surface mounting with hand-soldering tools – Link.
14 thoughts on “The tiniest deadbug proto”
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Ribbon cable of the right pitch would make soldering wires directly to SMD chips easier, if you had no other choice.
For larger SMD that works, but unfortunately the smallest typical pitch ribbon cable comes in is about 0.64mm (80 pin IDE cables). The QFN above has 0.5mm pad centers and 0.2mm between pads. And the wires inside 80 pin IDE cables are still 30 gauge like the Kynar above…except stranded, which makes things a little more difficult, with strands going everywhere. Still a really nice technique for standard SOIC, where the pitch is 1.27mm, the same as 40 conductor IDE cable.
I almost tried this a few months ago, its a technique that a skilled solderer can use for SOT packages but QFNs are nearly impossible! It’s so easy to burn the pads, for these times I recommend the SchmartBoard which will allow you to prototype with these packages without getting too frustrated.
Very nice. I had to do this once with a 24 pin 5×5 QFN. Another technique is to use a razor knife to scratch out the pattern on a blank PCB. Once you’ve soldered it you can check to make sure you soldered it correctly using the ESD diodes. Take a multimeter in diode check mode and apply + to GND and – to each pin in turn.
http://de.sevenload.com/alben/4LP56Ej
This is an ICL7106 sawn out of a mechanically defective DMM… pitch is 0.80mm here, Wire is 34AWG.
I’ve done this plenty of times before, and it’s quite easy if you have some tweezers, magnification, and use fine enameled copper wire.
Yeah, that blows away my dead-bugging an SMD 5×3.2mm crystal (https://www.sparkfun.com/products/8581) to a dead-bugged ADNS-3090! :) Also, why not wire-wrap wire? For me, it’s easier to work with on tiny crap