MOTM

On Fri, 12 Sep 2003, Mike Estee wrote:

> I agree, soldering a gnats ass to a pad is kinda annoying, but not 
> impossible.  You need the right tools, and they're kind of expensive 
> right now. You don't know soldering until you've soldered SMT!  Where's 
> you sense of adventure! ^_^

  Reflow soldering of SMT parts is really not that hard.  The trick is to 
use solder paste and a toaster oven (really!).  The only really tedious 
part is using a toothpick to apply the paste to each solder pad, then 
using tweezers to place the parts.  I've done this even with 0.5mm 
pin-pitch microcontrollers, and they turn out fine.

  On critical designs, I'll ante up and have a paste stencil made--then 
you just lay the stencil over the PCB and trowel a thin layer of paste 
over the stencil such that all the pads are done in about 10 seconds.

  Anyway, just heat a toaster oven to 420F, put the prepared board in and 
watch till the solder melts under the pins of the largest IC.  Then remove 
the board and set it on a cooling rack (takes about 3 minutes in my 
toaster oven desigated for flow soldering).  After it cools, solder on any 
through-hole parts and its ready.

  I've seen the paste dispenser and picker-placer robots at work on boards 
at a factory I hire from time to time.  Those are awesome. ;)

Crow
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