[Prev][Next][Index][Thread]
Soldering Lecture (was Re: Cool Idea)
Hi Gary W., Ralph, and all who posted,
> Original Poster: Parpp807-at-aol-dot-com
> Travis,
> Never use any acid flux or acid core solder with electronic circuitry.
> will turn copper wire to a copper salt in record time. Old timers
>cleaned the solder tip by simply swiping it across their pants and then
>putting solder on the tip to tin it and then again swiping across their
[snip]
Hehehe. Sounds JUST like me ;o))). Of course there comes the
time, when you have to explain that spot on your trouser to your
mom or wife ;o)). However, a few comments on the various posts
about solder and soldering iron tips.
Tips: There are two kinds of tips out there:
-Copper tips. These require periodic cleaning and re-shaping
with a file, because the heat erode after prolonged usage. They
blacken with time and after considerable usage they are simply
worn out and need to be replaced. Cheap irons and soldering
guns use these tips. The reason why guns use these tips is quite
simple actually. The soldering gun is NOT heated by heat transfer,
but rather directly by high current. Usually in the tens of amps and
in big guns, in the 100s of amps range. This highly stresses the
copper "wire" (your tip) and leads to failure over a (relatively short)
period of time. So, using nickel cladded tips is not worthwhile,
which brings me to the second kind of tip:
-Nickel cladded tips: These tips require nothing more than a wipe
with a soft cloth to bring up the shiny finish again. They are much
more resistant to erosion, than those pure copper tips. Do not, I
will repeat, DO NOT use a file on these. This WILL RUIN the tip,
turning it into a common copper tip.
Use a variac to power your iron. That way, you can turn down the
variac, when you donīt need the power. This saves the tip quite a
bit of wear. You can also turn up the iron (you DID buy a soldering
iron with more watts than you usually need, didnīt you?), when you
need the extra power. Of course, having more than one iron is a
must-have situation, too. A big one for those heavy jobs, a soldering
gun for the quickie jobs and a temperature controlled one. I use a
Weller Magnastat, which is great (thermo-magnetic temperature
control). Having a small iron for those SMD jobs is a luxury, which
isnīt necessary IMHO. I use my Magnastat with a small (0.8mm) tip
and my soldering jobs ARE industrial quality. Anyone who has seen
my soldering work will agree on this ;o).
Fluxes:
There are several different fluxes around. However, NONE of them
are acid free, not even "acid-free" rosin cored solder. Okay, I can
hear all those jaws dropping, now. However, it IS true. Rosin consists
of organic acids, which (as all fluxes do) washes away the impurities,
so that you can make that A1 solder job. Any of you, who have tried
soldering ANYTHING w/o flux, KNOW what I am talking about. The
key point to "acid free" solder (usually rosin cored) is the fact that
the acids within the flux are heat activated (ahha). As soon as the
soldering joint cools down the flux (and the organic acid) goes back
into an inactive state. Still donīt believe me? Have a look at a well
used nickel cladded tip. Well used, means a tip that has seen some
5-6 years of service. These tips are impervious to heat related
problems, but they are NOT completely resistant to acids. If you look
at your tip with a strong magnifying lens, you will see a small ridge
right above the tip itself. This ridge is not present on a new tip. What
you are seeing is the nickel surface being removed chemically (the
nickel plating isnīt very thick, so the ridge will also be very small)
over a long period of time. Theoretically, sooner or later, you will
remove the nickel "cladding" and the tip needs to be re-newed.
However, I have several tips that are 15 years and older and show
no signs of copper appearing from underneath the nickel surface.
But, now back to fluxes:
Removing rosin flux is very easy: Just take some isopropanol
alcohol and a stiff toothbrush and brush away. Be cautious
about "open components" like relays. Most are wash proof
(usually there is a printed label saying so). Your project will
look 1000x better, than if you leave that rosin gunk on it.
Trouble soldering SMDīs and donīt want to buy that expensive
SMD paste? Easy. Just dissolve some of that rosin (your next
music shop is a great place. Rosin is used to coat the bows of
violins, cellos, etc) in alcohol. Make a saturated solution. It
should be dark brown in color and have the consistancy of synthetic
0W oil. Put a little in a syringe (those insulin syringes are great).
To solder an SMD part just put a drop on one pad. Apply a tiny(!)
bead on solder to the tip of your iron. Heat the rosin-solder pad
with your iron. Donīt apply any extra solder. You just want to tin
the pad and thicken the rosin slightly. Next take your favorite pair
of tweezers and slip that little SMD bugger on the pad and
position it correctly. Another drop of flux to the other (!) pad. Using
SMD solder, now solder this side of the SMD down. As the rosin
from the first pad is very tacky, your part wonīt move around and
stick to your iron (esp if you use a thermo-magnetically controlled
iron, as I do). Then reheat the first pad and apply a little solder.
Presto, thatīs all there is to it. It takes a little practice, but once
youīve go the hang of it, you will be soldering SMDs like their big
counter parts and your projects will become smaller ;o). For
example, my homebrew model rocket video/telemetry transmitter
would not have been possible w/o SMDs. Using fluid rosin is a
great way to solder-plate your projects (like those copper traces
on your PCB), as the copper becomes unsightly after prolonged
exposure to air. All you need is fluid rosin, a soldering iron and
a very minute quantity of solder. Simply coat the copper with
fluid rosin. You will immediately notice that the copper, that
comes into contact with the rosin, becomes bright "copper pink"
in color. This is another indication of the organic acids doing
thier work (even w/o heat applied). Now touch the tip of your
iron to the solder and slowly pass over the copper traces. As
soon as you run out of solder (i.e: the traces no longer become
silver colored), add a small quantity of solder to your iron and
continue on. After you have coated the whole board, you might
notice a rough surface or a blob of solder. Just add more rosin,
reheat the trace and take a (non synthetic) cloth and wipe over
the trace. It will become butter smooth. If you are carefull, you
can use a heat gun (not at top setting, tho). This makes the
smoothing operation a bit easier, but PRACTICE first on some
unimportant projects, because overzealous use of the heat gun
can remove your copper traces or even induce thermal stress,
which leads to (usually invisible) cracks within the SMD
components themselves, leading to a PIA trouble shooting job.
If you have a real *blob* of solder somewhere, you can remove
it with de-soldering braid. Donīt use a solder sucker, esp. if you
are building SMD. The solder sucker can suck your solder pad
right off the board, which means back to square one ;o(x(. After
a bit of practice, you wonīt see a difference to the industrial
work :-o))
Other fluxes:
Acid core flux: I donīt recommend this for ANY kind of work. It
is outdated. NEVER use it on electronics or electrical work of
any kind. As it has been pointed out, this will corrode anything
in sight (including your soldering tip). It usually contains HCL
(hydrochloric or itīs common name: pool acid).
Solder grease:
This is a variation of the above, which has similar properties
to rosin flux. It remains chemically inactive as long as there
is no heat applied. I would still recommend washing off the
parts with soap, hot water and a stiff brush, however. Okay
for copper tubing, but NOT for electronics.
Got a problem tinning that old AWG #1 cable? Hate having to sand
everything, which oxidizes readily? A great (no, make that fantastic)
flux is used in plumbing service. It has the consistency of wheel
bearing grease and has a grayish (!) look to it. This stuff is
fantastic. It is a combo of fluxes (slightly acidic and heat activated)
and it has powdered soldering "tin" mixed in. This stuff is esp.
great for lead filling work on cars (a trade that has died out,
being replaced with Bondo; much to my disgust) or, to keep it
on topic, sweat soldering that stubborn piece of copper tubing,
you stashed away years ago (for your coiling work, of course),
which has now become dull and unsolderable. You just put a bit
of that stuff on the tubing and heat it with your favorite propane
torch (or soldering iron, if it is a small job). This stuff removes
all impurities and coats it with a fine trace of solder. Just perfect
for sweat soldering or applying a bead around the (e.g.) tubing.
After completing the soldering job just take a stiff brush, soap
and water and work away. This will remove all the flux and
prevent it from corroding over time. For copper or other tough
customers you can even use that SOS pad from the kitchen
sink to scour away. Best of all this stuff is considered non-toxic
(although I wonīt eat it ;o} ) because it is legal for use on water
lines.
Lecture closed ;o)))}
Coiler greets from Germany,
Reinhard