■ Installation of
surface mount chip.
■ Application of
solder to one pad.
I usually go back and re-solder the first pin since it may be
messed up from re-positioning the part.
NOTE: Some people prefer to use a small dot of glue
to hold each component in place before soldering. If this
works out well for you, use that method but keep in mind
it adds another step and can make rework more troublesome down the road if you have to replace any parts.
Working with Fine Pitch Parts
Care needs to be taken to ensure that there are no
solder bridges causing shorts. When dealing with fine
pitch parts, do not be concerned about solder bridges at
first. Since the pitch is so close on these pins, just solder
each side without worrying about solder bridges and let
it cool before going on to the next side. When done, let
the whole component cool. Then, go back over each
side with solder wick to remove the excess solder. This
will remove most of the solder and leave just enough to
make a proper connection. Repeat the process if solder
bridges still exist.
Solder wick is your friend when
working with surface mount parts. If you ever get a
bridge or too much solder on a connection, just use the
wick to remove the excess. In the event you remove
too much, you can always add more solder and
repeat the process. Be sure to let the component
cool between each side so the part will not be
damaged by excessive heat. The results can be fantastic if you take your time.
■ Removal of excess solder.
you only want to sever the lead without nicking
the PCB. That may not be a problem if there are no traces
underneath the chip but it is always best to assume there
are and be very careful during the process. When I was
removing an SX28 processor, the leads were thin so I only
needed to cut one side and then bend the chip up and
down to break off the other side. With the chip out of the
way, the rest of the preparation was easy.
Just put a fresh bead of solder down with the iron and
all the leads end up sticking to the soldering iron. Just
wipe them off on your sponge. The last step is to go over
the pads with solder wick so they are all flat again, ready
Replacing Surface Mount Parts
Sometimes you may need to replace a surface
mount component. There is one method I have
found works very well for fine pitch parts. I use a
sharp utility knife to cut the leads right at the
body of the part. It requires a steady hand since
■ Small hybrid modules assembled with
ordinary soldering gear.
January 2009 63