Soldering is a process in which two or more metal items
are joined together by melting and flowing a filler metal into the joint, the
filler metal having a lower melting point than the workpiece. Soldering differs
from welding in that the workpieces are not melted. There are three forms of
soldering, each requiring higher temperatures and each producing an
increasingly stronger joint strength:
- soft soldering, which originally
used a tin-lead alloy as the filler metal
- silver soldering, which uses an
alloy containing silver
- blazing, which uses a brass
alloy for the filler.
The alloy of the
filler metal for each type of soldering can be adjusted to modify the melting
temperature of the filler. Soldering appears to be a hot glue process, but it differs from gluing
significantly in that the filler metals alloy with the workpiece at the
junction to form a gas-tight and liquid-tight bond.
Soft soldering is characterized by having a melting point of
the filler metal below approximately 400 °C (752 °F), whereas silver
soldering and brazing use higher temperatures, typically requiring a
flame or carbon arc torch to achieve the melting of the filler. Soft solder
filler metals are typically alloys (often containing lead) that melt at
temperatures below 350°C/662°F.
In the soldering
process, heat is applied to the parts to be joined, causing the solder to melt
and to bond to the workpieces in an alloying process called wetting. In stranded wire, the solder is drawn up into
the wire by capillary action in a process called wicking. Capillary action also takes place when the
workpieces are very close together or touching. The joint strength is dependent
on the filler metal used, where soft solder is the weakest and the brass alloy
used for brazing is the strongest. Soldering, which uses metal to join metal in
a molecular bond has electrical conductivity and is water-tight and gas-tight.
Equipment:
1) How many
different types of soldering irons are there and which are ones to avoid when
soldering small wires?
There are hundreds of
kinds of soldering irons on the market:
·
small craft sized
irons sometimes called "pencil irons" sold at Home Depot, Radio
Shack, Hobby Lobby, Michaels, etc. are cheap and easy to use.
·
larger "heavy
duty" irons (get a lot hotter than is good for LEDs
·
ESD Digital Regulated
iron
ESD stands for
Electrostatic Sensitive Device. Regulated means you can set the temp
accurately. This type of iron is best for use when soldering wires onto an LED.
LEDs are heat + discharge sensitive. (This does not mean that an ESD is necessary for the wires, only for work on the diode itself. That is why having the wires and resistors already done for you is so nice.)
I own an ancient soldering iron which gets hotter the longer it is on.
For soldering of wires at the connection points: I can use my old iron, but
I’ve found I need a light touch, usually soldering and then unplugging the
iron, plugging it in and making the next solder, etc.
Anyone who already has the "pencil iron" can use this.
However, if you intend to do lots of wiring, think about the ESD iron.
2) Is it necessary to
solder on a particular surface, or is there a surface
you would
recommend?
Soldering surface
can be as little as a piece of cardboard or as much as a ceramic tile.
Cardboard can be changed often, giving a clean surface for work. Take a look at
the wire stripping video. http://www.modeltrainsoftware.com/kynarwire.html
Scroll down to the second item on the page to see video. She was using a
paper towel.
3) What sort of
solder do you recommend?
I get "benzomatic" at Home
Depot in the tools area. It comes in a small cheap roll. It has 40% rosin core
(flux already inside of it) and is a lead-tin type, which sticks better than
non-lead. I researched lead in solder and safety concerns. The lead does not
become airborne when you heat the solder. The flux is what is in the smoke you
see. The lead stays inside the solder itself. So if you wash your hands and
avoid eating or smoking or touching your eyes or nose while soldering, you will
not ingest any lead!
4)I like the idea
of the flux in the solder, but why is flux necessary?
Flux is a reducing agent
designed to return oxidized metals to their metallic state. Rosin Flux makes
the solder "stick" better by etching the metal a bit. It ‘seals’ the
metal connection and prevents future oxidization and thus improves the
electrical connection and mechanical strength. The two principal types of flux
are acid flux, used for metal mending and plumbing and rosin flux used in
electronics.
Steps in
Soldering:
- bare about 1/3 inch of each wire
to be connected
·
slide shrink
insulation piece onto one side of wires to be connected and away from soldering
area
- lay together the wires which are
to be connected
- solder them by holding the solder
near the wires and heating it with the soldering iron
- cool a minute
- give a little tug to make sure
solder is solid
- slide shrink insulation over the
connection
- hold shrink insulation over a lit
match in order to shrink it tightly onto the connected wires
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