[sdiy] pros and cons of SMT in DIY

[paula at synth.net]

Richie,

> Paula, when you say "working with 0402", do you mean replacing the odd
> component here and there, or soldering 100s of SMT parts on?

mostly the former, but I have done the latter a few times.
next boards I have arriving for prototypes have about 100 parts on, only 
two are 0603, 7 are through hole, the rest are 0402 and QFNs

> And how
> are you actually doing the soldering?  With a fine tipped soldering
> iron and a steady hand?  ...heater tweezers?  ...or stencilling solder
> paste onto the board then placing components into the paste and
> ovening the board?  Just curious what methods you're using,
> particularly to get consistent results with those tiny QFNs.

I use several tools;
* fine tip soldering iron (almost like a needle)
* microscope (my eyes are getting worse)
* solderpaste (I have some fine solder for the occasional use, but 
solder paste in a syringe is superb.
* and for QFNs, solderpaste with a heat gun.

I've not yet tried the solder stencil method (these boards are tiny, 
<40mm by <15mm) but for a igger board I would.

> I can also vouch for the structural integrity of super-gluing down
> wire-wrapping wire or polyurethane enamelled copper (magnet wire) for
> mods to PCBs.  Never seen one fail, and they're almost impossible to
> rip up if you need to.

totally agree, Kynar is just amazing to work with.

> I've never felt entirely happy with the fumes
> given off when someone has to solder in an area of the board polluted
> with dried Cyanoacrylate glue though.

hahaha, yeah, that's a GREAT smell :)

> I remember doing this once and
> leaping backwards with my eyes and nose stinging!

hehe, yeah, not nice!

Paula