2
Basic Soldering
Evan McKeeJan [email protected]
The purpose of this tutorial is to teach someone who has never
soldered (pronounced SOT-terred) how to begin soldering with a
pencil tip soldering iron.
The tutorial is geared toward working with small electronics and
is divided into two parts:
· Part one contains basic, start-from-scratch knowledge about
soldering and familiarizes the reader with soldering components and
terms. A brief written tutorial is also presented.
· Part two contains links to two useful video tutorials on the
actual act of soldering.
The tutorial should take approximately 30 minutes to complete.
Upon completion, the reader can be expected to solder electronics
simply and safely. As with any skill, practice makes perfect, and
hands on experience is the best way to get better at soldering.
Important safety tips:
1. The metal tip of a soldering iron heats to and maintains a
temperature of around 600° F (315° C). DO NOT touch the tip with
your bare fingers, or hold the soldering iron like the stock model
shown below:
2. Make sure you’re working in a well-ventilated space,
especially if you are using lead-containing solder.
Part I: Glossary and Basic Tips
Source: sciencebuddies.org
Useful Soldering Terms:
Soldering Iron: A tool used to melt solder for the purpose of
joining two metals. Three main categories of soldering tools exist:
Soldering irons, soldering guns, and soldering torches.
Soldering iron
Soldering gun
Soldering torch
Irons are most the most commonly used tool for soldering small
electronics, guns are used on larger parts like the insides of
cars, and torches are most useful when you don’t have outlet
access. Attachments also exist for regular butane torches that
convert them into soldering guns, with no outlet required. This
tutorial focuses on the pencil type soldering iron shown in the
leftmost picture.
Solder – The noun form of solder refers to the fusible metal
wire with a low melting point used to join less fusible metal
workpieces. For electronics, use solder with a rosin core.
The verb form of soldering is the act of joining two pieces
using solder wire and a soldering iron.
Flux – A lubricant preventing oxidation of the metals that are
being connected, as well as “wetting” the surfaces to be soldered.
Flux used to come separately in a little container and had to be
applied in a different step. Now, flux is contained in the core of
the solder wire. The rosin core in the solder spool shown above
acts as flux while you solder.
Tinning – Before beginning the act of soldering, you should put
a little bit of solder onto the tip of the iron. This is called
“tinning”. Tinning the tip of your soldering iron is important – it
keeps a layer of solder between the air and the iron, preventing
oxidation.
Oxidation – The iron tips of modern soldering irons are subject
to transforming into iron oxide with exposure to air, even at room
temperature. When the tip is heated, this happens much more
rapidly. Why is this bad? According to Metcal,
“The biggest factor affecting tip performance in oxidation will
be the loss of wetting ability. As oxidation builds up on the tip,
it creates a thermal dewetting barrier. When this happens, the
solder will tend to ball up on the tip instead of flowing
smoothly.
The oxidized layer will also impact heat transfer between the
tip and the work. Many times a soldering iron that does not seem to
be hot enough is actually suffering from oxidation.” source
Oxidized iron tip.
Written Tutorial:
The following written tutorial acts as a step by step guide for
soldering. The text and images are taken from
www.sciencebuddies.org.
Source: Part 1 Part 2
Preparing the Soldering Iron: Tinning the Tip
1. Place the soldering iron in its stand and plug it in.
2. Wait for the soldering iron to heat up.
3. Moisten the sponge.
4. Wipe the tip of the iron on the damp sponge. This will clean
the tip.
5. Melt a little solder on the tip of the iron.
· This is called tinning and it will help the heat flow from the
iron's tip to the joint.
· The solder should flow onto the tip, producing a bright shiny
surface.
· If the solder will not flow onto the tip, clean it by wiping
it on the wet sponge.
· When tinned, wipe excess solder off on the wet sponge.
· You do not need to tin the tip before every joint, but you
should re-tin it if it has gone dull when the soldering iron has
not been used for a few minutes.
· Check the manufacturer's instructions related to tinning the
tip.
6. The tip of the soldering iron should be a shiny silver color.
If it is black and pitted, replace it with a new one.
Soldering
1. Solder needs a clean surface on which to adhere.
· Buff the copper foil of a PC board with steel wool before
soldering.
· Remove any oil, paint, wax, etc. with a solvent, steel wool,
or fine sandpaper.
2. To solder, heat the connection with the tip of the soldering
iron for a few seconds, then apply the solder.
· Heat the connection, not the solder.
· Hold the soldering iron like a pen, near the base of the
handle.
· Both parts that are being soldered have to be hot to form a
good connection.
Figure 2. The tip of the soldering iron heats both the copper
pad and the lead from the electronic component. Solder melts when
placed in contact with the hot metals to be joined.
3. Keep the soldering tip on the connection as the solder is
applied.
· Solder will flow into and around well-heated connections.
· Use just enough solder to form a strong connection.
4. Remove the tip from the connection as soon as the solder has
flowed where you want it to be. Remove the solder, then the
iron.
5. Don't move the connection while the solder is cooling.
6. Don't overheat the connection, as this might damage the
electrical component you are soldering.
· Transistors and some other components can be damaged by heat
when soldering. A crocodile clip can be used as a heat sink to
protect these components.
Figure 3. By absorbing heat, the crocodile clip will reduce the
heat that flows to the component, helping to prevent damage.
7. Soldering a connection should take just a few seconds.
· If it is taking longer, see the troubleshooting section
below.
8. Inspect the joint closely. It should look shiny.
· If you are soldering a wire (called the lead) onto a PC board
(on the track), it should have a volcano shape. See Figure 3.
· If the connection looks bad, reheat it and try again.
Figure 4. The solder in a good join will be shaped like a cone,
with solid contact between the solder and all surfaces to be
joined. Bad joins (also called dry joins) should be melted and
remade.
9. Wipe the tip of the iron on a damp sponge to clean it. The
tip should now be shiny.
10. Unplug the soldering iron when it is not in use.
Final tip: A common mistake is to glob the solder onto the iron
directly, and then try to wipe it off the iron into position. The
preferred way is shown in the above tutorial.
The iron heats up the connection, which in turn melts the
solder. The tinning that is done right before you begin soldering
should be the only time you apply solder directly to the soldering
iron.
You are now familiar enough with the components and terms of
soldering to view the video tutorials linked in part two.
Part II: Video Tutorials
“How to Solder Electronics,” CuriousInventor, 2007 (YouTube)
The video linked below is a helpful YouTube video on soldering
small electronics. It’s short in length (6:51), but dense with
information. It also contains several examples of the wrong way to
solder:
https://www.youtube.com/watch?v=IpkkfK937mU
“How To Do It: Basic Soldering,” Coldrestart, 2007 (YouTube)
The video below contains an excellent visual soldering
demonstration starting at 3:15. The speaker stresses the importance
of applying solder to the heated joint, not the soldering iron
itself.
http://www.youtube.com/watch?v=BLfXXRfRIzY&t=3m15s
