Desoldering, can't suck it or wick it, blow it.

[Walter Lawhead]

I have all the tools of the trade including a high end
Pace soldering station. Even with the tools and
decades of experience I still find that occasional tab
that refuses to clear of sollder. Ran into several
pads on my KX1 while installing the upgrade that
refused to clear and gave all the signs of pulling
away from the pc board. On a chance I had nothing to
loose I used my fine iron tip (aprox 0.03") and a can
of 'Dust Off' compressed gas, used to dust computer
keyboards. Heated the problem pads and they came clean
when I gave the pad a shot of gas. The down side of
this procedure is the solder is blown out the opposite
side and you must inspect the board and remove any
solder splatter. I use the long plastic tube that
usually comes with the compressed gas to direct the
spray right at the problem pad while heating the pad
at the same time.
Hope this saves someone the trouble of reworking
damaged pc board traces.

73, Walt KE8BQ

73, Walt, KE8BQ

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[Ron D'Eau Claire-2]

Trying to use a solder sucker on the same side of the board as the soldering
iron usually doesn't work for me either. Some builders trim a notch in the
side of their sucker nozzle to they can put the sucker over the soldering
iron tip.

I put the sucker on the opposite board from the iron and have excellent
results on the first try. I do it like this:

Carefully choose which side of the board to touch with the iron. Choose the
side with the fewest heat-sensitive parts like relays, trimmer caps and
pots, etc. Generally, that's the "bottom"  of the KX1 PCB. So you position
the board in the vice so you have a clear view of the side you  are going to
touch with the iron then, with your hand supported on a rest to hold it
steady, position the solder sucker on the opposite side over the hole with
your finger/thumb on the trigger. Now, while looking at the pad where you
are going to touch the iron, touch the iron carefully to the pad and, as
soon as the solder melts, squeeze the sucker trigger and WHACK! You have a
clean hole.

Don't admire the clean hole until you've carefully moved the soldering iron
back to its stand! A LOT of builders groan about having successfully cleared
a pad and then, while they're admiring the clean hole while holding the iron
in their hand accidentally touch a relay case or pot shaft and melt it!

Put the iron back in the stand before looking or doing anything else! Until
it's safely back in the stand, it's a "bomb" waiting to attack your rig!

Ron AC7AC

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[N8CEP]

Good ideas Ron!  I have never used a solder sucker before. How is one
used when a part is still on the board?  And what is a good solder
sucker to buy?

Thanks for educating us poor mistake makers!

Keith Hamilton, W8GX
K2 #4692


Ron D'Eau Claire wrote:

> Trying to use a solder sucker on the same side of the board as the soldering
> iron usually doesn't work for me either. Some builders trim a notch in the
> side of their sucker nozzle to they can put the sucker over the soldering
> iron tip.
>
> I put the sucker on the opposite board from the iron and have excellent
> results on the first try. I do it like this:
>
> Carefully choose which side of the board to touch with the iron. Choose the
> side with the fewest heat-sensitive parts like relays, trimmer caps and
> pots, etc. Generally, that's the "bottom"  of the KX1 PCB. So you position
> the board in the vice so you have a clear view of the side you  are going to
> touch with the iron then, with your hand supported on a rest to hold it
> steady, position the solder sucker on the opposite side over the hole with
> your finger/thumb on the trigger. Now, while looking at the pad where you
> are going to touch the iron, touch the iron carefully to the pad and, as
> soon as the solder melts, squeeze the sucker trigger and WHACK! You have a
> clean hole.
>
> Don't admire the clean hole until you've carefully moved the soldering iron
> back to its stand! A LOT of builders groan about having successfully cleared
> a pad and then, while they're admiring the clean hole while holding the iron
> in their hand accidentally touch a relay case or pot shaft and melt it!
>
> Put the iron back in the stand before looking or doing anything else! Until
> it's safely back in the stand, it's a "bomb" waiting to attack your rig!
>
> Ron AC7AC
>
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[Don Wilhelm-3]

Along with all Ron's good comments, I would like to add one more technique
for clearing solder filled holes or holes partly filled with solder - a
tapered stainless steel needle.  Heat the hole and the needle and when it is
hot enough push the needle through and the solder will easily clear.

The only condition is that the component lead has already been removed -
easy enough if you cut the pins and pull them out one at a time.

If you can't pick up one of these tools at a hamfest, a large sewing needle
glued into a small hole drilled into a 1/4 inch dowel (dowel long enough to
serve as a handle - your choice for the length) will do the job nicely.

73,
Don W3FPR

> -----Original Message-----
>
> I put the sucker on the opposite board from the iron and have excellent
> results on the first try. I do it like this:
>
> Carefully choose which side of the board to touch with the iron.
> Choose the
> side with the fewest heat-sensitive parts like relays, trimmer caps and
> pots, etc. Generally, that's the "bottom"  of the KX1 PCB. So you position
> the board in the vice so you have a clear view of the side you
> are going to
> touch with the iron then, with your hand supported on a rest to hold it
> steady, position the solder sucker on the opposite side over the hole with
> your finger/thumb on the trigger. Now, while looking at the pad where you
> are going to touch the iron, touch the iron carefully to the pad and, as
> soon as the solder melts, squeeze the sucker trigger and WHACK! You have a
> clean hole.
>
>

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[Ron D'Eau Claire-2]

Keith W8GX asked:
I have never used a solder sucker before. How is one
used when a part is still on the board?  And what is a good solder
sucker to buy?

------------------------

I remove the part first. Parts are cheap. If in doubt, cut the leads! After
all, the PCB with the rest of the parts is the most expensive part you have.


To tell the truth, you don't always have to do that.

Often you can save caps and resistors by very *gently* lifting up on one end
at a time while touching the iron to the pad to melt the solder. I use a
very thin small screwdriver or dental pick (see your dentist - he/she
usually throws them out regularly) under the lead whose soldering pad I'm
going to heat. Then lift gently when the solder melts. You can usually heat
the pad and lift from the same side of the board. Again, use your iron on
the safest side of the board.

That process can be facilitated by removing most of the solder first. If you
can safely approach the PCB from the component side with your iron, heat
that pad from the component side while using the sucker on the other side
where the tip will sit against the board over the pad. The idea is to force
all the air pulled into the sucker to come through the solder pad. That will
usually leave very little solder in the hole. Sometimes you'll find the lead
is loose in the hole after doing that. At the very least, a little heat will
release it completely.  

If the pad is full of solder while you remove the part, it might take going
back and forth several times, side to side, but resistors and caps usually
come out easily. The trick is to NOT apply significant pressure on the lead
the until the solder is molten to avoid pulling the plated through hole out
of the board. Also avoid "cooking" the pads. The pads slowly debond as long
as heat is applied. It's not just how hot they get, it's also how long
they've been hot that determines whether a pad will come loose.  

Once the part is out, then I clear the hole using the solder sucker as
needed.

There's a *world* of difference between the bulb-type suckers and the
spring-loaded type. In my experience, the bulb suckers are an exercise in
futility 99% of the time. My first choice is the spring loaded sucker for
best performance per dollar spent. Of course, nothing is as nice as the
heated desoldering tools like the Hakko.

Elecraft recommends the SoldapulltR model DS017LS. It is good. I also have a
Radio Shack sucker that I suspect was made by the same people. Works fine.

On-line, one of my favorite tool vendors is Tequipment (www.tequipment.net)
who carries the Palidin 1704
(http://www.tequipment.net/PaladinTools1704.html or http://tinyurl.com/z8elf
for a short URL) that sells for about $20. I not connected with tequipment
but have made several purchases from them and liked the service the provided
(and questions answered by a simple phone call when I was trying to decide
exactly what I wanted to order).

If you've got a spare $100 you can consider the Hakko powered desoldering
tool that Tequipment carries as well. I'd probably buy one except that I do
some of the documentation for Elecraft. I am careful to live in the same
world as our builders, using only those tools suggested to our builders so I
know that when I say something will work if done a certain way it's based on
my actual experience and not what I "hope" would work. The worst thing would
be to have a fancy desoldering tool on the bench and not be able to use it
in good conscience!

At the risk of stating a PCB "heresy" is this: if you are desoldering and
suddenly see the little round donut of a solder pad stuck to your iron,
don't panic. The little donut on the side of the board without any
connecting trace is the easiest to debond, and it usually does not affect
the performance of the rig in any way. Just be sure you don't tear or break
any traces leading to the pad. If that happens, it's a sure sign that you
are heating the pad too much for too long, but losing a donut won't kill the
rig. Just go ahead and put in the new part and solder. The solder will bond
to the plating in the hole and on the other side of the board.

I solder and desolder at 700F unless it's one of the rare occasions I use
some braid (pad too close to an obstruction to get the sucker over it, for
example). When using braid I bump up the iron temperature to 800 F because
of the heat-sink properties of the braid, and I keep trimming off the used
braid so I'm always working at the end to minimize the amount of braid the
iron has to heat up. Also, make sure there's a little solder in the hole and
the iron is slightly wet with solder so the heat will transfer quickly. The
biggest issue I see with braid is that people don't have some solder to
start the transfer process and they don't have the iron hot enough so they
end up cooking the pad until everything debonds.

In my book, braid is the hardest way to clear solder from pads without
damaging them. It requires the most skill to use successfully.

The ability to change the tip temperature with a simple twist of a knob on
the front of the unit one of the features I like best about my Hakko 936
soldering station. I find that's very important when I do use braid.

Finally, I mentioned using a vice. A lot of builders don't have them. Over
the years I've done without one more often than I've had one handy. A good
alternative is to use a few books or even bean-bags (just avoid ones covered
with static-generating plastic). Prop up your PCB with them so it's stable
and you can get to both sides easily with your hands supported by the bench
or other books. A minute spent properly supporting your PCB and your hands
to approach the board with everything under control can save you hours of
frustration after damaging something because your hand wandered or the board
moved at the wrong moment. And always arrange things so you can see what the
soldering iron is touching clearly. If you get the solder sucker in the
wrong spot, you won't hurt anything. But you want to know where that
soldering iron hot tip or body is at all times when it's out of the holder!

Hope that helps a bit. Like anything, taking one's time makes doing the work
a lot more fun! None of are racing the clock trying to disassemble a timer
fuse on a nuclear bomb to save the world, I hope! So the fun, and success,
is in doing it right, not doing it fast.

Ron AC7AC


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