>mostly practice on a bunch of scrap boards to start..

Definitely recommend doing this. It is also worth attempting some joints
with solder-wick braid.

>cleaning is done with the tool(reamer) that looks like a
>small drill bit -- may have a slight taper to it...

This is usually the biggest source of problems with a desoldering tool,
especially if it has more than one user. It must be cleaned out regularly,
the tip removed and all the slag in the tube behind the tip, which goes to
the collector removed. If this cleaning is not done while there is still
some heat in the iron, the slag will cool down and sit in the tube, and then
the problem is to get it hot enough to remove it without damaging something.
regular cleaning of the desoldering iron is a must, rather than waiting for
it to clag up.


>clean with wet sponge just like regular iron -- minimize "on" time
>since just a little tip erosion makes the unit useless...

Hmm, my experience is that the tip should last as long as a normal soldering
tip. If the tip is cleaned using a drill, then the iron cladding inside the
hole will be removed, and the tip will then eat away rapidly. Normal
cleaning with the proper steel wire tool should not damage the tip in this
way.


>sometime helps to put extra solder on each joint (with normal iron)
>before applying the desoldering  tip -- that way the tip has molten
>solder to "seal" the nozzle and "suck" better

Agreed, but I believe this helps for different reasons. It seems to help
more on PCB's which have been commercially wave soldered, and my theory is
that there is leaching of one of the metals because of extended periods with
the solder bath at temperature. This will change the melting point of the
solder. Putting fresh solder on the joint restores a percentage of the
leached out product, and removes the oxide layer, allowing the desolder tip
to make good thermal contact, and have the melting point of the solder at
the correct temperature.


>for pins that are connected to the gnd/voltage plane it sometimes
>easier to solderwick the top and bottom side and then break what's
>left of the solder joint by "wiggling" the component pin with a small
>needle nose plier or pointed scribe...

I doubt that the PCB will survive the process described. I suspect that this
will tend to remove the plated through hole plating. How to proceed depends
on what you wish to save - the PCB or the chip. Often the decision does have
to be made this way :) See further down if the chip is to sacrificed.

My preferred method of using the desolder tool is to apply it to the pin on
the bottom side of the PCB, and watch the solder meniscus on the top side
around the pin. When you see the solder start to melt, then rotate the
desolder tool so it is moving the pin in the hole in a rotary motion. The
pin should move on the other side of the board. Activate the air while
keeping the pin moving, and almost always this will remove all the solder in
the hole. Depending on the chip placement relative to the hole, the lead may
now be totally free in the centre of the hole. Repeat on all leads of the
component, and it will then fall straight out.

If the placement of the chip means that the legs are against one side of the
hole, then the best method seems to be to solder suck all the legs, and then
using a normal soldering iron - sometimes on the top side - apply pressure
to each pin in turn to melt the remaining solder and bend the pin
sufficiently that it no longer has its rest position against the side of the
hole. You may then need to come along with the desoldering tool to remove
the last bit of solder that will then form a bridge between the pin and the
side of the hole, and to do this will often entail an application of more
solder.

If there is an inner layer acting as a heat sink, or a large copper layer on
the outside, I will often apply a normal iron to the same pin on the other
side of the PCB. This is about the only way to get enough heat into the
joint rapidly. Trying to unsolder this joint any other way will almost
certainly result in PCB delamination, copper separation, and/or component
damage if the heat input is not sufficient to get the joint up to melting
temperature rapidly. To do this requires the PCB to be supported with a
"third hand" type clamp, or another person to steady it so you can get at
both sides of the PCB with the two irons.

If the chip is definitely to be sacrificed, then this method will give the
best desoldering of the PCB. Use some fine side cutters to cut all legs of
the component as close to the component body as you can manage (difficult
with surface mount). Remove the component body, and then using an ordinary
soldering iron, heat each pin in turn, and remove it from the solder. I find
the side cutters the ideal tool to grab the pin while doing this. Once all
the pins have been removed, then use the desoldering iron to suck the solder
out of the holes. I guarantee this method to be the kindest to the PCB.


>someone might have a video tape (i've seen some, but they
>all were pretty expensive)

Check with your local night school, Polytechnic, or other tertiary education
establishment to see if there are any electronics courses where they might
show this sort of video. Failing that chat up a salesman for one of the
soldering iron companies to see what they might have. He may even have a
product demonstration video which may be of some help, if they do not have
an instructional video as such.

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