The tiniest deadbug proto

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By Collin Cunningham
Posted 2008/02/12 @ 3:30 pm
Category Electronics

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

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6 Responses to The tiniest deadbug proto

Anonymous on February 12th, 2008 at 3:55 pm said:

Ribbon cable of the right pitch would make soldering wires directly to SMD chips easier, if you had no other choice.

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macegr on February 12th, 2008 at 4:10 pm said:

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.

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SaTyPe on February 12th, 2008 at 5:01 pm said:

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.

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eschlaep on February 12th, 2008 at 6:57 pm said:

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.

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faustian.spirit on February 13th, 2008 at 12:32 am said:

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.

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David on February 13th, 2008 at 3:05 am said:

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.

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