Mel,
Despite all the exotic methods, one thing is true - solder suckers of
all types work much better when there is a lead in the hole to be
de-soldered (the lead conducts heat through the hole). Clearing the
hole after the lead is removed is a different matter entirely. For my
part sticking something that solder will not adhere to into the hole
(after heating the solder pad with a soldering iron) is quite
effective. A wooden toothpick will work, but I use a stainless steel
needle. I have several with handles than I have picked up at hamfests,
but in a pinch a sewing needle with the eye end embedded into a cork
works fine too (the needle will get hot, and the cork is only 'finger
protection').
73,
Don W3FPR
Mel Farrer wrote:
I would like to add a comment on removing solder from SMT via holes.
There are three methods and the first two have been discussed. I have
found as the technology gets better, smaller, the plated through holes
also get really small. Like 0.020 or smaller. Solder suckers have a
very difficult time pulling the solder up.
Let me explain, consider the mass of the solder pad on the side you
are going to apply heat. If you get the solder liquid and don't
destroy the pad, the bottom pad, MAY be liquid and come up with the
sucker type. It works good on larger pads but not so good as the
holes get smaller. Too much air leakage and you are trying to pull
cold solder. Not always successful.
Using the solder braid has also the same problem as it is a heat sink
and usually requires you to put additional heat to suck the solder
up. Works great on larger holes and traces that are large like 50 ohm
strip line.
OK, so what is left? I use a solder "pusher". Back before someone
invented the solder sucker, we used a small hollow rubber ball with a
small entrance teflon tube that we had and it had replaceable tips of
different sizes to accommodate hole size. This allows exact pressure
of the right size on the hot side of the PCB and "blows" hot solder
out against the colder solder on the other side and effectively cleans
the hole without over heating the pad.........
From someone who is long in the tooth,
Mel K6KBE
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