DPRG mailing list archives: [DPRG] SMT Soldering

Fri Jun 6 12:54:22 CDT 2008

Hi Eric -

A couple of months ago, I had to do some very tiny SMT rework. (One
particularly icky aspect involved dead-bugging a 20 mil pitch part and
soldering one strand of wire (smaller than 30 AWG) to each leg.
Another involved soldering a few 0402 parts between two legs of SMT
ICs. Yet another involved lifting pins and soldering parts between the
board and the  part. Photos upon request.)

It's challenging, but if you have good magnification or are very
nearsighted (like me!) it's kind of fun.

What kind of soldering iron will you have available?  We use a Weller
WD 2M, which has some very small tips available.  Have some nice sharp
tweezers, too.

What's the pitch of your parts?  Off the cuff, I'd say that 0.050"
spacing is very doable. Surface tension is your friend and your enemy
when working with tiny parts.  0805s work very well for passives.
0603s are OK, and 0402s are a pain.

DON'T use lead free ROHS solder!  It'll look like you frosted a cake.

Can you provide a link to the actual footprint drawings?

One hint - for SMT SOIC-like packages, solder one corner pin first.
Then bend the part so the other corner pin can be soldered to its pad.
 All the pins will line up.

Good luck!
-Jeff

On Fri, Jun 6, 2008 at 12:21 PM, Eric Sumner <kd5bjo at gmail.com> wrote:
> I am working on laying out one of the boards for my thesis, and I have
> no experience with surface-mount soldering.  The processor that I am
> using is available in DIP, TQFP, or MLF; how hard will it be to
> hand-solder either the TQFP or MLF package?  Also, which size of
> resistors and such would you recommend?
>
>  -- Eric
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