response 1 of 36:

Oct 29 01:30 UTC 1999

Um.  That's a tall order...

response 3 of 36:

Oct 29 03:32 UTC 1999

Soldering is (usually) easy.  It's just a question of using a low temp
melting metal to glue other bits of metal together.  For electronics,
the most important thing is to get the right kind of solder.  What you
want is an alloy of tin and lead called "60/40" (for the ratio of the 2
kinds of metal), and you want "rosin core".  You do *NOT* want "acid
core".  The rosin or acid are called a flux, and their purpose is to
clean off impurities from the metals being soldered together.  Both do
this, but the acid leaves a corrosive deposit behind that will eat
through thin metal pretty quickly, with obvious bad consequences for
electronics.  In any event, the right stuff is readily available at any
good hardware store, meijers, radio shack, purchase radio, etc.  The
solder you buy will come in the form of a thick gauge wire, and the
rosin will be in a tiny hole run through the middle of the wire.  It
won't be visible unless you cut the solder, which there's no reason to
do.

In order to melt the solder, you need a soldering iron.  Originally,
these were irons that you heated up in a fire, but this has long gone
out of fashion, being replaced by electrically heated irons that are
considerably more convenient.  The typical modern soldering iron looks
something like an overly fat pen with a long metal tip and an electric
cord.  Like anything else, having high quality tools makes the job go a
whole bunch easier.  In a soldering iron, you want to look for something
with the highest wattage (the more power it can burn, the faster it can
heat things up, and if you're soldering small things that can be easily
damaged by excess heat, heating things up faster has the paradoxical
effect that you need less heat to solder.)  The other thing to look for
is a thermostat; it costs more, but it's a lot easier to take care of.
The fancier irons also come with stands, little sponges, and other
conveniences.  These aren't necessary but they are nice.  You can get a
relatively cheap iron for as little as $10-20.  The expensive ones with
the thermostat can run $80 or more.  Different soldering irons (and
their larger cousin, soldering guns), come with different sized tips.
Larger tips heat up better but are not so good for really small stuff.

If you don't have the fancy stand, then you can very easily make due
with a pie plate; the disposable "tin" ones that frozen pies used to
come in work fine (do they still make these?).  You also want something
to rub the tip against to clean it; a sponge will work, or ordinary
paper towels will work (the coarse ones that you find in public
restrooms work best).  The sponge or paper towel should be wet; since
the paper towel will turn into mush, it's best to wet it last.  It
should be thoroughly wet, but not have any standing pools of water on
it.  You want to assemble all your stuff before you proceed further.
You don't want to leave the soldering iron unattended as long as it's
plugged in or still hot.  The first step is to plug the iron in and let
it warm up.  If it's a new iron, the tip will probably not be tinned,
but will most likely be a coppery color.  It will need to be tinned
before you can use it.  To do this, simply wait until the iron gets hot
enough to melt solder, then apply solder to the tip and let it flow all
over the tip.  So far as handling the solder goes -- it's usually
easiest to leave most of it coiled up on the spool, and to unroll it as
you use it.  Generally, you'll want to unroll a foot or so, and you'll
want to hold it at least 3-4 inches away from the end.  To apply it to
something, simply press the tip against the hot object, it will melt,
and you can apply a lot very fast by pressing the tip through the blob
and against the hot object.  It's a very interesting sensation.  When
tinning the iron, you'll want to rotate the tip as you apply the solder,
otherwise, the blob will drip off instead of coating the iron.  You
don't need a very thick layer, ideally, the thinnest layer that is shiny
bright will do fine.  Once you have the iron coated, you'll probably
want to remove the excess solder; to do this, simply run the iron over
the sponge.  It helps to press down fairly hard and move it fast
(otherwise, you'll melt the sponge or burn the paper toweling.) If there
are any black bits on the iron, you'll want to remove those, and and if
there are any bits that somehow aren't coated, you'll want to get those
coated.  You may need to use a file or something in stubborn cases to
solve any of these patchy problems.  The black stuff may be carbonized
solder, but it also tends to be corrosive, so you want to get rid of it
before it eats away at the tip and leaves it a funny shape.  The reason
why the solder might not want to stick to all of the tip is that the tip
will have some corrosion (almost all metals corrode in open air, and
quickly form an invisible layer of corrosion), and solder won't "wet"
corrosion.  This is, in fact, the reason for the rosin.  The corrosion
will also form a thin, but effective insulator, so it won't heat things
up as fast.  Indeed, you will probably find that you need to "scrape"
the iron with the solder to get it to actually start melting, even if
the iron is hot enough.

If you were to leave the iron just sitting for a long time, the hot
solder on the iron will start to corrode, and it will form a yellowish
deposit on its surface as it does this -- it can even look almost
golden, in some cases.  While it may look pretty, again, it's bad for
soldering, and it means you need to re-tin your iron.

Now, for actually soldering stuff.  The "approved" technique is this:
 (1) make the wires (or whatever) mechanically secure, so that they are
        wrapped against each other, and can't wiggle.  This isn't
        absolutely necesary, but it does make the job go easier.
 (2) heat the wires with the soldering iron.  There needs to only
        be a small amount of solder on the iron for this, basically
        just enough to enable the iron to "wet" the wires so that
        the heat travels into the wire better.
 (3) when the wires are good and hot, apply the solder to the wires.
        If the wires are not hot enough to melt the solder, they are not
        hot enough to make a good connection.  Ideally, you would
        use the heat from the soldering iron to travel through the metal
        and into the solder, but you may find instead that you need
        to apply the solder to the crevice between the tip and the wire.
        With practice, however, you can tell how many seconds it takes
        from between when you apply the iron to the wire, and when you
        should apply the solder.
 (4) you want to put enough solder on so that there is a smooth layer
        of melted solder smoothly coating the entire outside of the joint,
        and so it's good and solid.  Any solder past this point is
        at best wasteful, and at worst, could bridge a gap and touch
        other wires that you didn't mean to join.  (This is an
        especially bad thing when soldering IC dip packages which have lots of
        wires right next to each other that aren't met to be joined.)
 (5) remove the iron, and *without wiggling any wires*, blow on them
gently.
        The solder will have a smooth shiny appearance when melted,
        and will become slightly less smooth and look "whiter" when
        it freezes.  If you jiggle it while it's freezing, it may
        crystalize out into a much coarser form, and this is bad,
        because it may not make good electrical contact or may fail early (this
        is one form of what is called a "cold solder joint").
 (6) when the joint is good and cold, (and you can touch it with your
bare fingers),
        *then* it's safe to tug on it.  If you aren't sure if it's cold enough,
        try touching the wires a few inches from the joint, and running your
        fingers towards the joint -- if it gets too hot then stop and blow on
        it more.  The objects should be firmly attached to each other and there
        should be absolutely no wiggle.  Also, inspect the joint. The solder
        should not be beaded up on the joint, but should instead form a smooth
        continuous joint with the metal under it.  If it looks like you could
        pry it apart with a knife, the solder is probably not really attached
        to the metal under it, and the joint is defective.  Typically, with
        rosin core solder, some of the solder will congeal and form a
        transparent "drip" near or sometimes on the joint; this is completely
        harmless and can safely be ignored.

If you've never soldered before, you should practice on some scrap wires
first.  If you've never soldered electronics, ditto there, practice on
some "extra" stuff.  With the wires, try pulling it apart, you can
afford to be rough with your scraps.  Don't move onto the real stuff
until you feel comfortable that you can get dependable results.

Be careful.  Never leave a hot soldering iron unattended.  If you can't
pick it up by the tip, don't go away.  If it *is* hot, be extremely
careful around it.  You can get a *really* bad burn from the iron with
less than a second of contact, and even before the pain impulses make it
to your brain.  In fact, your first warning *may* be the smell of
"something cooking".  Trust me, though, you don't want to do this, and
there's no reason why you should do this if you are careful.

response 5 of 36:

Oct 30 04:18 UTC 1999

All good advice except the part about the wattage of the soldering iron.
Small integrated circuits a nd transistors will not stand much heat.  A 25
or 30 Watt soldering is ok if you are careful to not overheat the compnents.
Otherwise, stick to a 15 Watt iron.  It will take longer, but you will have
less damage.

It's also a good idea to clean off the extra flux with isopropyl alcohol.
You can get that at any grug store.  91% is best as it removes all the water
as it evaporates.  70% will do, but you will have to wait till it is
thoroughly dry before trying the circuit.

response 7 of 36:

Oct 30 12:58 UTC 1999

You can also get a 40 watt iron and put it on a lamp dimmer for more precise
control.

response 9 of 36:

Oct 30 17:19 UTC 1999

For components that are particularly heat sensitive, if you have room you
can clip a pair of locking foreceps onto the lead you're soldering, between
the joint and the component.  That'll conduct the heat away.

response 11 of 36:

Oct 30 19:52 UTC 1999

You see SM fuses a lot in computer keyboard ports.  I'm not sure about the
logic of putting in a fuse that's nearly impossible to find or replace. 
What's the point of protecting the rest of the components if it's going to
be dead anyway?

response 13 of 36:

Oct 30 20:31 UTC 1999

Protects against fire or overcurrent on the power supply?

I once fixed the logic control part of a fancy turntable; it had what looked
to be little signal transistors with one lead missing.  I think they were
fuses, since the good one had no resistance and the bad one was open.

response 15 of 36:

Oct 31 01:42 UTC 1999

The only reason I know to clean off rosin flux is because you don't like
the looks.  If you were stupid enough to use acid flux (which you
shouldn't!) then, yes, you really really do want to clean it off.  In
commercial PCB manufacture, other stuff is used for making boards, at
least some of which is best washed off.  One common technique for this
is to use an ordinary dish washer with no detergent, just ordinary hot
water.  I once toured Ann Arbor Terminals and was quite amazed to see
them load up a dish washer with boards.  Water makes an excellent
cleaning agent, but there is one caveat, you want to dry boards quickly.
The dish washer probably got water up to 140F-180F, so the boards would
have dried quite rapidly once removed.

Fuses in modems may be a requirement of the telco - they don't like it
when you short out their lines.  I suspect a lot of computer parts are
made with the theory that there's no point in it "lasting forever",
because it's going to be functionally obselete in short order.  I still
have 3 external 2400 baud modems at home which probably work fine.  I
have to admit, I haven't been tempted to find out if they actually do
work.

response 17 of 36:

Oct 31 01:53 UTC 1999

#15 slipped in.  The PC board vendors use a special flux that is water
soluble.  Rosin core flux is not.  (As I recall, one of the washable
variants is made from lemon.)

Yes, I've been known to wash PC boards right along with the dishes.
You just have to watch out for water sensitive stuff like speakers,
however.

response 19 of 36:

Oct 31 02:48 UTC 1999

Yeah...flux can cause problems in high-impedance circuits.  It's a little
sticky and can collect dirt, which can then cause leakage paths of a few
megohms or so between traces.

response 21 of 36:

Nov 1 01:15 UTC 1999

 I don't mean to sound ungratefull for you wonderfull responses, but
 that's a bit more information than I need...  I really appreciate you
 handing down some of your own experiences to me.  I was just wondering
 about the etching process, since that is before the component
 installation in the PCB layout.  How to I make etch a board based on
 that strange little 6cm X 4cm layout given to me by the ELMP people? 
 They talk about chemicals...where do I get those....I need to learn a
 lot before I even begin soldering the components.  Any more help
 appreciated greatly :) oh yes, btw in case your wondering the
 information on the ELMP can be found at -
 http://www.algonet.se/~cyrano/elmp/index.html
. lytez .

response 23 of 36:

Nov 1 03:34 UTC 1999

I've seen drips of rosin on metal on decades old electronics.  The metal
is still nice and shiny and bright under the rosin--often brighter than
the metal that wasn't protected by the rosin.  Rosin may well be
corrosive, but it's probably less corrosive than ordinary air can be.

Wave solder machines are definitely pretty impressive things.  The basic
idea is that there is a long thin nozzle facing upwards.  The solder
comes pouring out of this and spills back into the machine.  The boards
to be soldered are attached to a conveyor belt that pulls the boards
over this flat fountain of solder, one by one.  Each board, which can
easily have hundreds or even thousands of connections, gets soldered in
less than a second.  I've hand-soldered PCBs -- it takes days and days
of painstaking labour to accomplish the same result, and it's
considerably more error-prone.

Commercial PCBs, especially ones to be wave-soldered, are generally
coated with a "solder resist".  This works just the same way that water
& oil does, in that the solder doesn't like to "wet" the resist and just
beads up or rolls off.

Ferric chloride is popular because it's safe (no fumes), easy to handle,
and produces dependable results.  But virtually any strong acid will
work; you could use hydrochloric acid and get similar results.  One
catch is that most acids will release small amounts of hydrogen as they
attack the metal--not enough to be dangerous, but the bubbles can cause
more uneven results, especially at high concentrations.

The results of the etching process will be some sort of copper salt,
probably blue or green, and definitely rather toxic.  In theory, you
really shouldn't pour it down the drain, but ought to dispose of it as a
hazardous waste; I don't know of anyplace you could just drop a small
amount off at however.