tips on soldersucking

[Batz Goodfortune]

Y-ellow Mark 'n' y'all.

At 03:33 PM 04/13/00 -0400, mark scetta wrote:
>how do y'all do your desoldering, without damaging components? i have used 
>1. a heavyduty springloaded type of solder sucker, which will sometimes rip 
>the traces right off the board, 2. a cute squeezable rubber ball type of 
>sucker, and 3. solderwick, which i cannot for the life of me make work. any 
>tips?

Without having read some of the other replies yet, but having spent a
regrettable proportion of my life sucking solder and components from
boards, I may be able to help a little here.

There are two basic aims.

1> Save the components bugger the board.
2> Save the board stuff the component.

In the first case we're talking about salvaging valuable components from
old boards. In which case you're not worried about saving the board. You
simply want to scab the component(s). In this case you usually want to rip
as many components as you can, as fast as you can with as higher yield as
you can.

I'll cut to the chase. I use a hot-air paint stripper gun. You heat the
board up till it just about bursts into flames and all pins are molten,
then pull the sucker out with a component puller. The idea is that you heat
the whole thing up real fast and you cool it real fast. So that it's no
more stressful to the component than the original wave soldering process.
With practice  you can achieve a 90-95 % success rate. Some boards are
harder than others. 

Mill-spec boards are real hard because they bend and clip the leads. This
makes them a bugger to get out of the boards and the components are more
stressed.

Consumer spec boards are generally pretty easy. The damn things just about
fall out of their own accord when you heat them up.

A guy I know here uses and oxy set to do the same job. Actually probably a
better solution in that the heat is so fast, the board and components don't
know what's hit 'em. The only problem is this guy doesn't understand the
concept of CMOS and ESD. So it's not  worth buying any of the salvaged
components in his shop that are static susceptible devices. Actually given
his prices it's just plain not worth it.

Remember. When doing this, wear gloves to protect your hands and eye
protection. Do it in a very well ventilated area with a fan blowing. Or do
it outside under cover. Or wear some kind of mask. Or all 3 as do I.

If you get sick of that. Just store the boards in boxes (which I also do)
and go on a scrounge now and then. It's no big deal to suck some components
off a board or two as required. But try doing it that way en mass and
you'll get RSI faster than you can say "Carpel Tunnel Syndrome".

Double Sided boards are the worst to remove anything from. Quite often
you'll pull the plate-through hole right out of the board still attached to
the pin of the component. You have to remove these manually with a
soldering iron but this is usually no big problem.

(2)
On the flip side of this, when you suspect a dead component and you wish to
change it, or simply substitute a component, you are not interested in the
welfare of the component you're removing. But the board's integrity is of
paramount importance.

Here the recommended procedure is to cut all the pins off the component
with side cutters. Leaving the pins still soldered in their holes on the
board. Then with soldering iron you quickly extract the pins using a pair
of needle nosed pliers. Once done you suck the excess solder from within
the holes with your solder sucker.

Desolder wick is generally for clean up work after the fact. You won't be
able to use it to suck the solder out of the holes with any success. But it
will soak up solder around the pins. It is useful but only under certain
circumstances. And it has other uses as earth braiding too BTW.

An intermediate step with a solder sucker, where you wish to desolder the
component and save the board at the same time, is to try to suck as much
solder  from around each pin as you can. But this is rarely enough.
Especially with double sided/plate through boards. The pins generally
remain still stuck to the plating inside the hole. What you have to then do
is go round with a pair of needle nosed pliers and gently twoggle the pins
till they come loose. Only when all pin in the component are completely
free should you attempt to remove it. Otherwise you could... (A) break one
or more pin instead. (B) rip the plate through clean out of the board along
with the component.

Suggestion. Have a look at the board under a magnifying glass as you're
doing it. You'll see how the pins sit in the holes even after  you've
desoldered them.

OTHER ISSUES:
If you bugger the board in the process, have some kynar wire on hand. AKA
Wire wrapping wire. This is ultra thin plastic sheathed wire on spools. You
can make amendments to boards with it and you can strip off the coating to
replace tracks with it. And because it's so thin, you can often fit it down
a board hole along with the leg of some component to replace the plate
through, even if it's been damaged.

Japanese domestic/consumer boards are notoriously easily damaged. It's a
function of the way the boards are made. It's a good idea when repairing
gear with these boards to carry some kynar wire, and even a few heavier
gages of tinned copper wire for extra current. For when you're working on
power amps etc.

FINALLY.
I'm a poor person. Even poorer now that I'm basically an invalid pensioner.
If it weren't for salvaging components I couldn't afford to mess with this
shit at all. But nearly everyone salvages stuff. Especially in a place like
Adelaide where you can't even buy resistors half the time. But it is a
common practice that goes back to the days when people use to have to make
their own capacitors by hand. Although I've been salvaging any cool
components and gear I could find over the years, when I came out of
Hospital, salvaging  stuff off of boards was like a therapy. I couldn't
watch TV for more than 5 minutes. I could barely concentrate enough to read
my email. But I could sit there for hours on end ripping components from
boards. Unfortunately most of it was TTL and redundant digital crap but
that's all I did for about 3 months and it did reduce my stock pile.

So if anyone's after some old TTL chip or other.... :)

Hope this helps.

Be absolutely Icebox.

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