[Noisebridge-discuss] eZ430 Chronos

[dpc]

Mikolaj Habryn <dichro at rcpt.to> writes:

> On Fri, Mar 19, 2010 at 12:32 PM, dpc <weasel at meer.net> wrote:
>> Mikolaj Habryn <dichro at rcpt.to> writes:
>>
>>> I also have vague ideas for smart-dust-style devices to build, but
>>> find the idea of soldering tiny 0.5mm pitch devices into
>>> quarter-inch-diameter enclosures faintly daunting, and would rather
>>> attempt it in company, preferably with beer.
>>
>> the beer doesn't really help :-)
>>
>> you're talking the pin pitch though? as long as the pins are exposed (as
>> opposed to tucked under the package) it isn't too hard to tack lines
>> in. the 'hard' part was making sure the lines were stress relieved
>> enough so that they didn't break off randomly.
>
> I think they are tucked underneath - "48 VQFN Exposed Pad".

i've tacked leads onto a qfn (pic 16F688) which look pretty close to the
same sort of pin dimensions (0.5 pin size), but i'm probably mis-reading
something. 

anyway, i found the trick to be not screwing up the pads/pins as you
tack the lines on. how many lines are you doing? doing a whole side of
16 might start being pretty tricky.

anyway, some tips from a non-rework pro (ie, anyone good at this would
mock my caveman technique :-)

 - don't leave the wire end you're tacking on too long.

 - a little liquid flux on the part helped me get good tacks.

 - put a little solder ball on your iron tip and flick the tack wire
   through the ball until it looks a little thicker than before (you
   don't want a thing hair attached to the wire).

 - clean off the iron's solder ball w/ sponge.

 - bring your tack wire square onto the pin, and touch iron to
   connection.

 - very light pull on wire to check connection (very light because you
   don't want to fuck up the pad).

w/ the board i was mod-ing w/, it was easier to have the tack wires come
in from the top and for me to poke the iron in from teh side. ymwdv.

\p
---
The style is the man himself - George-Louis Leclerc de Buffon