[sdiy] Moving to Surface Mount - lots of questions

Tom Arnold xyzzy at sysabend.org
Wed Dec 7 03:13:02 CET 2011


On Tue, Dec 06, 2011 at 02:45:09AM -0500, Mike Beauchamp wrote:
> after assembling a few PCB's with a few hundred resistors, I've been
> thinking about moving to Surface Mount for my next project. Please
> convince me, or talk me out of it :)

I can manually stuff a board with 1206 resistors using a soldering iron with
a small tip much faster then I can stuff through hole.  Enough so that I'm
slowly switching in that direction.  The large parts are quite easy to deal
with.  I touch the pad with solder, nail one end of the part down, then hit
the other end.  no fliping and trimming, no worries about leveling the parts
when I'm stuffing a bunch of parts between solder passes.  At the very least
I'd try that.  I think you'd be surprised how easy it is.

> Speed: Having never done it before, how much faster is it to
> stencil-place-oven as opposed to insert-solder-clip?

Its at least on par if not faster to do the SMD parts.

> Reliability: I know that repairing a through-hole board is easier for
> most people, but is the reliability of SMT stuff on par with TH?

Seems to be the same.  Rework is a little more difficult but only because I
havent had enough failures to really get good at it.

> Storage: Those SMD resistors are tiny! What are some good ways to
> store 30-40 different values so they can easily be grabbed for
> populating?

I buy reels.  Usually find the values I want for a few dollars a reel
surplus.  I havent found a great method for storing small quantities.  Right
now I use little plastic bags in a compartmented plastic box.

> Toxicity: Soldering irritates my asthma, although my fume extractor
> helps heaps. Does sticking solder paste into an oven cause similar
> fumes?

I would not use your home oven.  At the very least a cheap toaster oven you
can run in the garage.  I've been using the skillet method.  If you just
place the board in an electric skillet you can heat it up quite nicely.
http://www.sparkfun.com/tutorials/59

With the skillet method you can use your normal smoke filter.

I've done BGAs with the skillet method.  Lots of fun to place several
hundred little solder balls by hand...

-- 
 -----------------------------------------------------------------
 - Tom Arnold       -  Free Synth DIY webspace http://www.sdiy.org 
 - SynthGeek        -  "...is it a virus, a drug, or a religion?"
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 --------------------         -- Neal Stephenson,  Snow Crash


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