92 What about soldering equipment for electronics work?
Description
This article is from the Antique Radios And Phonographs FAQ, by Hank van Cleef vancleef@netcom with numerous contributions by others.
92 What about soldering equipment for electronics work?
All of the manufacturers that use solder to connect electronic
components run "solder school" for new employees. Electronics soldering
is not the same as soldering pipes in plumbing or doing auto body lead
work. There is only one way to learn, and that is to do it. You will
need:
a. Soldering iron. A Weller or an Ungar "solder station" with
a 35-50 watt "pencil" iron and thermal control in a soldering iron
holder is best. If you are going to unsolder components directly
soldered to a chassis, you will need at least 50 watts, and maybe a
larger 100 watt iron. Do yourself a favor and buy a good soldering
station. It will cost more than a cheapie Radio Shack iron, but you
will find that the tip stays in good condition a lot longer, and that
you do much less damage with heat, using a good iron. The solder
station holder provides a place to put the iron down that is safe, a
real "plus." Also, buy an iron with a plated iron tip, or get one for
it. There is just no way to keep a copper tip well-tinned for this type
of work, and solder eats away the copper, ruining the tip after a
while.
b. Solder. Kester or similar ROSIN CORE solder is sold
specifically for electronic use. It is "eutectic" solder, that is, 37
percent lead, 63 percent tin, which melts at the lowest temperature.
Don't use 60-40 plumber's solder, which is 60 percent lead.
c. Small tools for use when soldering. You will want some fine
point needle nose pliers, some medium point needle nose pliers, and a
small set of diagonal cutting pliers. Also, a small screwdriver and a
solder "pick" that has a pointed piece on one end and a v-notched piece
on the other. Round this out with a solder sucker (a little pump with a
high-temperature plastic piece that you can safely shove into hot
solder, and a button trigger to trip the pump). Solder "wick" works
well, but remember that when you are removing solder from a 1934 radio
terminal, you are removing 4 or 5 times the amount of solder used on a
modern printed circuit board---use the pump to remove most of the solder
and the wick to remove the rest.
Tin your new iron, and keep the tip well-tinned at all times. This
means keeping a coat of unoxidized solder on the tip. The solder
stations come with sponges. Wet the sponge, and wipe the hot iron on it
to clean off residue. To tin the first time, just melt some solder on
the tip. The rosin in rosin core solder is a mild flux---that is,
chemically active to deoxidize and clean the surface so that solder will
flow onto it. Wipe the iron back and forth on the sponge to distribute
the solder. When properly tinned, the tip should be shiny with fresh
solder all around back about half an inch. Keep the tip looking like
this, and you'll eliminate half the problems people have when soldering.
To remove components, heat the old joint until the solder melts, and
remove the solder with the solder sucker. Bend the old component leads
back, and slide the lead out. You'll have to keep the joint hot until
you've got the bent-over part of the old lead away from the terminal.
This sounds easier than it is. You will want to learn to use the solder
pick, small screwdriver, and needle-nose pliers on various joints. If
the component you are removing is scrap, clipping the lead and leaving a
short loose end often makes getting the loop open easier, and once the
loop is open, the lead can be removed by pushing the wire through the
terminal. Also, using the nippers (carefully!) to nip the wire loop so
that it will break often helps when removing components.
Watch out what you are heating, and watch out what you are pushing and
pulling on. That iron is hot and will burn wire insulation, melt
polystyrene (clear plastic coil forms), etc. Move things out of the way
so you have a clear shot at the joint you are working on.
Don't bend terminals back and forth---they'll break. The worst ones for
breaking are on the 7 and 9-pin miniature tube sockets, and if you break
one, you get to replace the socket, which is a major task. Coil form
terminals are not far behind, and most of those old coils are
irreplaceable. The big terminals mounted on phenolic terminal strips
are fairly rugged, and components fastened to them are a good place to
get some experience before tackling finer work. On fragile terminals,
once the solder is removed (use solder sucker and solder will to remove
as much as possible), a little judicious use of nippers to cut wires,
and other little tricks you will learn as you go along, to avoid any
stress on the terminal, is the only way to go.
Another trick is to make a cold solder joint. Just wiggle the lead a
little while the solder cools, and it will stay free. You can then work
with two hands to get the joint opened up and the lead out of the hole.
When installing new components, run the leads for all new components
going to a particular terminal before soldering any. Form the leads
into new loops and nip off the excess. Place the iron against the
terminal and melt some new solder by pressing it against both the iron
and the terminal. It will melt on the iron first, then into the
terminal. Don't use too much solder, and make sure that the solder
flows onto all the wires and onto the terminal. Once the solder has
flowed into the joint, remove the iron and wait for the joint to cool
and solidify. This is where cold solder joints occur. A cold solder
joint happens when a lead gets wiggled as the joint is cooling,
preventing formation of a solid bond. They are generally easy to see,
because the solder ball on the terminal will often be very frosty, and
not have a smooth surface. They are also very easy to make, and you
should experiment with some scrap---just wiggle the pieces as the solder
is cooling, and you'll get a cold solder joint. If you've got any doubt
about a joint, reheat it and reflow the solder.
Cold solder joints are the single most common solder defect. Inspect
your work carefully after soldering, and if there is the least doubt
about the joint, reheat it. Excess solder and solder bridges (where the
solder flows between adjacent terminals) are other quality
problems---remove excess solder, and inspect carefully. Many radios
were "unrepairable" simply because of bad soldering somewhere.
Attention to producing the very best workmanship, and close inspection,
will produce quality solder joints----anything less will produce
trouble.
While the people who originally built these radios were very skilled,
you'll occasionally find a cold solder joint or a joint with no solder
at all on a lead that has been there as long as the radios has been
around. Don't be afraid to inspect, reheat, and reflow a fifty year old
solder joint that looks suspicious just because it has been there for
fifty years.
There are two schools of thought on rosin removal. You can leave the
rosin on the joint, and most radios were made that way. However, if you
do want to remove it, isopropyl rubbing alcohol on a Q-tip will melt it
right off.
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