[sdiy] moving to SMD/SMT

[The Old Crow]

  SMT stuff really isn't that bad.  Only real tool changes recommended are 
the smallest soldering tips and the thinnest low-residue solder (aka 
Kester 245).  Even with my bad eyesight I can solder 0.5mm-pitch TQFP 
packages, though you have to be careful with the leads as they bend if you 
look at them hard enough. ;)  With large chips, you have to solder 
opposite corners (at least 4 pins, 1 per corner) to keep it stable while 
soldering the rest.  I'll use a tiny bit of solder paste for this, though 
it can be done with the thin wire solder as well.

  I've also done the toaster oven reflow method, which is really not hard
to do at all--provided you have 1) a paste stencil 2) solder paste (aka
solder cream) 3) a temperature marker that can be placed on the board to
indicate when the surface temperature has reached 420F at which time you 
carefully remove the board to a cooling rack 4) don't cook your food in 
the same toaster oven.

  OK--the real trick is #1, the paste stencil.  These can be made by most
PC board houses, but they're not cheap--figure $150 plus S&H.  Using it is
the 2nd trick as you have to affix the board to a flat surface then anchor
the stencil, precisely aligned, over the board such that no warps in the
stencil occur.  A *thin* layer of paste is then troweled across the
stencil, filling in all the pad areas with neat little squares of solder
paste.  The stencil is carefully lifted away, then comes the eye-straining
positioning of parts.  This is where alignment of the 0.4mm and 0.5mm
pitch pins dissuades a lot of people and they just hire a board house to
assemble it.  Although, for SDIY it is rare for parts under 0.8mm pitch to 
be needed, unless it is some QFN, SSOP or TQFP-packaged microcontroller.
0.8mm pitch is easy to solder with a regular iorn and the thin tip.

Crow
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