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From: seeker@indirect.com (Stan Eker)
Subject: Re: surface mount by hand-doable?
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Date: Sun, 7 May 1995 18:37:42 GMT
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Jason Greene (younggun@ix.netcom.com) wrote:
: I'm going to build a circuit board that uses a 68 pin plcc.  I want
: to hand build a few at first to make sure the design is correct before
: I commit the design.  I'm not keen on drilling 68 holes .100" apart so
: I'm looking at surface mounting the plcc.  My question is, is there
: some technique to hand solder surface mounted components or is this
: something only machinery can do?  If it's doable by hand, what's the
: technique?

Everyone that makes through-hole sockets for PLCCs makes the surface-mount
variety, too (or just about).  The sockets are about .1" bigger on all 4
sides than the raw PLCC part, and most can be hand-soldered with care.

The ugly end - doing the soldering RIGHT takes skill or practice.  We use
them extensively at work, and only about 1 in 10 assemblers can do a good
job of soldering them reliably by hand.  You need a good tip on your iron,
and fine (.020" or .015" dia.) solder, and a liberal amount of liquid flux
to get it soldered to the pads.  Doing it WRONG is seriously annoying to the
poor b@stard that has to troubleshoot it.

If you have some bare boards with PLCC patterns, practice before you do the
real project.  Get a real fine (small tip) pair of tweezers so you can grab
the leads of the socket and see if they'll wiggle (unsoldered or poorly
soldered) and a 4X or 5X eyeloupe to check the actual joint.

As far as the solder and flux, I'd recommend changing to the water-soluble
variety if you haven't already.  You *DO* have to remove the flux, or
you'll see sub-100K resistance pad-to-pad as time goes on.  If at all
possible, remove it within the first hour of application and it'll come off
easier.  Leaving it overnight makes it hard to impossible to clean properly.
The liquid flux (absolutely required for good SMD PLCC soldering) should be
liberally applied with a brush or squeeze bottle, about 1 drop per side, and
will aid wetting to the pin and pad.  It's usually sold in big carboys or
jugs for the wave-solder folks, and helps hand soldering immensely.

