Re: The strengths of FORTH

On Mar 28, 9:19=A0pm, "Robert Miller" <rsmil...@[EMAIL PROTECTED]
> wrote:
>
> So far very little, but stay tuned. =A0I am just starting to build my
circ=
uit
> board and am finding soldering 0.5mm lead pitch ICs and 0603 size
discrete=
s
> rather challenging to say the least. =A0( I had to buy a stereo
microscope=
 so
> I can even see what I am doing. =A0I also had to build a 'third hand'
=A0t=
o hold
> the components in place while I solder them down. Even so, it takes me
> several minutes per component - but I'm improving. )
>
Having soldered SMT parts for a few years with just a soldering iron,
I find that using solder paste makes things much easier.

I don't even use a stencil. Just dab a little blob on each land (the
paste comes in a syringe with a needle), or in the case of fine pitch
parts spread the paste across all of the lands together and hope for
relatively few solder bridges. A hot air rework station melts the
paste just fine, but I think a hot air gun would work. If it isn't hot
enough you could modify its fan to run slower. For small parts like
0402 (I've seen roach poop bigger than 0402) my tweezers have become
slightly magnetized so I can carry most parts to their locations by
letting them hang from the end of the tweezers. Touching the part to
the solder paste takes it off the tweezers and then it's easy enough
to nudge the part into position.

Removing solder bridges from fine pitch parts is not a problem. Just
use lots of flux and use a soldering iron to pull away the excess
solder. If it doesn't come off you might need some solder wick, but
usually cleaning the tip will allow the iron to pull off excess
solder. If a fine pitch PCB footprint uses pads that are a lot longer
than needed, you could end up with bridges under the package that are
hard to reflow. QFN packages tend to be easy to reflow, don't have
much problem with solder bridges, and you can clean up excess solder
by running the iron around the perimeter of the package. Those are my
new favorite package.

Brad