[sdiy] smt placement and soldering..

[Jay Schwichtenberg]

I would recommend a good set of non-magnetizable and solder resistant
tweezers (ceramic if you can afford them), either a magnifier hood (~$5)
with good lighting or lighted lamp/magnifier ($60-$120)), a good soldering
iron, as fine pitch solder as you can afford (0.020" is cheap, 0.015" and
0.010" is expensive but better), lots of solder wick both narrow and wide
and a lot of round wood tooth picks.

Read the data sheets on the solder you use. I use both Kester water solible
and no clean. The tempature makes a big difference.

Having the finer solder gives you better control how much solder you use.

Once I place a component on the board with the tweezers I usually hold it
down with a tooth pick tool I've made to solder it. I clip the sharp point
off the tooth pick with a pair of dykes and flatten the tip by squeezing it
with my needle nose pliers.

I usually tack down a bunch of parts and then come back and solder them
properly. When tacking them solder the ends that are further from other
solder points. You want the thermal isolation so you don't unsolder other
components which are thermally coupled. Remember also that those little
resistors are on ceramic subsrates so they conduct heat also which can
unsolder the other side of the part. So keep the iron on the joint as short
as possible.

Some parts are very sensitive to heat. Only parts that I've had major
problems with are SMT metal film caps. A number of them are made out of
plastic and can melt. I don't even bother if I have to resolder one of
these, I just use a new one.

For myself I never go below 0805 parts and if the part is going to carry any
current at all I'll use 1206 size. SOIC 8, 14, 16 sized parts are pretty
easy to deal with.

Have plent of solder wick handy and some flux. I use the narrow stuff for
clean up and the wider stuff for removing parts. If I'm removing parts I
also use a higher temp and wider tip on the soldering iron.

Like Toby said a dental pick is good to for cleaning and to wiggle pins for
checking joints.

Hope this helps.
Jay

  -----Original Message-----
  From: owner-synth-diy at dropmix.xs4all.nl
[mailto:owner-synth-diy at dropmix.xs4all.nl]On Behalf Of Bert Schiettecatte
  Sent: Friday, July 18, 2003 12:14 PM
  To: synth-diy at dropmix.xs4all.nl
  Subject: [sdiy] smt placement and soldering..


  Hi all,



  I’m thinking about building a board with a lot of surface mount stuff, but
I’m not sure how to do it without messing it up. I have a decent soldering
iron (weller ws80) and very sharp small tips … I was thinking about
investing in a manual pick and place but maybe that’s overkill. Anyone have
any references on how to do surface mount prototypes without messing it up?



  Thanks,

  bert



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