WXTECH SOLDERING COURSE
Do not expose children to lead alloys and dangerously hot soldering
irons. Be more safety consious for others because they aren’t as
aware of the hazards of soldering.
with 60 years soldering experience in electronics equipment maintenance
shops, research labs, and NASA equipment manufacturing shops. Use
the references for more information.
Al Washington 12 June, 2014
weather station owner may find the need to solder. Some may need
skills to repair or replace a circuit component. Others are
assembling a kit of parts where everything is included. Some may
design a circuit and produce the component board including drilling and
etching. Hopefully this soldering course will provide some
information so that you’ll solder safely and with confidence
1 DIY as used in this course is ‘Do It
Yourself’ and sometimes is the ‘Do-It-Yourselfer’, the person.
2 Wetting is when a liquid spreads out evenly over a surface without forming droplets.
3 When heat is removed from the work, the
alloy solidifies, not dries. Turning from a liquid to a solid.
is pronounced [sod-er]. Bonding materials by soldering, brazing
and welding are sometimes confused. Soldering is a process of
bonding items by flowing a low temperature melting alloy on the surface
and filling the void between the parts with solid metal. Soldering
uses temperatures below 700°F. Brazing uses temperatures above
700°F but below the melting point of the items that are bonded.
Welding is a process of melting and fusing the items that are bonded.
is a very dangerous task involving high temperatures, lead alloys,
vapors, fumes, acid, harsh chemicals, and tools that may cause
injury. This course suggests that the untrained person get hands
on training from an expert solderer before attempting to solder.
The kitchen table is not the appropriate place to solder
protection should always be used in case anything goes the wrong
way. Side shields are needed on prescription glasses for necessary
protection. Also consider and protect observers who may be near
to the soldering.
should not be permitted in the vicinity of soldering because of the
possibility of burns from the high temperatures and the possible
exposure to a large quantity of lead. Children should not be
exposed to lead alloys that may be used in soldering. If solder
containing lead is used, everyone should know the hazards. The
soldering iron and the work piece is hot without any visible
warning. Children won’t know that the work area is hot.
will produce fumes of lead, tin and other alloys. Work in
adequately ventilated areas or use respiratory equipment. Some
exposure may cause harm to an unborn child, reduce fertility, cause
respiratory and skin sensitivity, affect brain development in
children. Other hazards must be read on the MSDS
Please don’t ever give a child the possibility of pulling a hot soldering iron down on to them from a work table. THINK
Material Safety Data Sheet MSDS
MSDS is a multipage document for each chemical or product. The
MSDS provides information for products used in the workplace. It
is the go to place providing specifications and safe handling, toxic
information, health hazards, fire fighting, first aid procedures.
The DIY should be familiar with MSDS on solders, fluxes, and cleaners
used. All products have an MSDS. There is even an MSDS for
hazards and precautions can’t be included in this short course.
Links to several MSDS are for example only. Not responsible for
information supplied by other publishers.
CIGWELD Tin-Lead solder wire MSDS techdata/msdscigweld_tinlead.pdf
Tin/Lead Alloys-Solder MSDS techdata/msds_tin_lead_solder.pdf
Also find MSDS on fluxes & cleaners used when soldering.
Prevention and treatment of burns
using a hot soldering iron and hot parts, it is almost inevitable that
the technician will someday get burned. There are ways to lessen
the severity of burns to fingers/hands.
be aware of the hot dangerous places and when they are hot, how long it
takes parts to cool after joining. Of course the iron tip will be
hot when in use. The parts that have been soldered or unsoldered
will remain hot and dangerous for a minute or so after the iron is
removed. Always watch where your hand is reaching. Don’t
blindly reach for the soldering iron because you may contact the hot
part. The iron should be returned to the soldering iron holder and
not placed on a table top.
burn treatment procedures are the result of many years training and
supervising electronic technicians in maintenance and manufacturing
shops. Treatment of small burns applies to burns from hand
soldering irons and also to home kitchen burns from hot oil splatter or
hot cookie sheets.
have been taught to get some ice or a stick of butter to soothe the
burn. Maybe you intend to pinch off an aloe stem or buy some burn
treatment? That’s bad advice. Those take too long to begin
treatment and are the worst suggestions for first treatment for small
burns. You need to control the burn while it is in progress before
it can cause damage. You can get instant treatment in 2 seconds
if you know what to do.
react quick enough to prevent burns. It takes several seconds to
realize the pain is a burn from a hot object. First, you hear the
sizzle, then you feel pain, a few seconds later you deduct that
the pain is a burn. Then you react by dropping the hot
soldering iron is 500°F, and your finger touches it; ouch it’s difficult
to think that. The outer layer of dermis becomes almost 500°F
from heat conduction from the iron. The heat migrates down into
the body heating the flesh layer by layer to hotter and hotter
temperatures. You’ve now removed your digit from the iron but the
flesh remains hot. The longer the layers stay hot, the more burn
damage occurs. We have to get the flesh cooled in a hurry.
rush to the sink for cold water; get some ice; apply burn treatment
cream. Too late. Your finger is now toasted.
and practice a reflex to instantly cool the burned site. The burn
site is at 500°F. Your mouth is 98°F. Put your burn into
your mouth and that will reduce the flesh temperature from 500°F to 98°F
within 2 seconds.
OK, so your finger is dirty and won’t taste good. Would you rather have a burned finger that will be in pain for weeks?
You hear the sizzle, feel the pain, insert finger in mouth.
hurt for awhile. Keep the burned site moist until you can get to a
faucet for running cold water. Then do your normal aloe or burn
treatment cream. In a day, you won’t notice the burned area.
You’ve prevented discomfort from a minor soldering iron burn.
soldering, set up a glass of water. If you’re unfortunate to get
burned, just dip your fingers into the water. Instant relief, no
burn. It’s better than sucking on your thumb. But who
prepares for a hazardous task like soldering?
children away from soldering. The irons may not have an indicator
lamp showing that it’s hot. It doesn’t smoke, make bubble and
boiling sounds. Soldering tools are apparatus for responsible
May your burns be minor and just a learning experience.
a. Eye protection Before
investing in tools, take stock of your eye protection. If you
don’t use prescribed glasses, purchase a comfortable pair of quality
safety glasses with side shields. If you wear prescribed eyeware,
they should also protect your eyes from debris injury. You will
need protection from hot fragments, objects ejected when clipping, and
b. Soldering iron
The soldering iron can range from just a few dollars for a blister pack
soldering kit similar to a wood burning tool to a professional
solder/unsolder station with a hefty price tag.
your iron to the task you have. For a training project soldering
axial lead through hole electronic components, you should select a 25
Watt AC line powered iron. When you have more experience
soldering, invest in another iron that has features such as thermostat
controlled. Isotip makes an excellent battery powered iron with
interchangeable sizes of tips. The battery is recharged from the
Some irons have screw in interchangeable heaters. The heaters have screw on tips of several shapes and sizes.
A more experienced technician may need a thermostatically heat controlled soldering station.
soldering irons differ from stained glass soldering irons mainly by
Wattage. Stained glass artists use larger irons that have the
capacity to heat larger areas. Their solders are larger solid wire
with no flux core. They apply flux before soldering.
burning tools are also similar to soldering irons. They may have
similar capacity but offer different tip selections. Wood burning
irons also have hot knife selections. If your iron is compatible,
you may be able to buy wood burning tips for your soldering iron.
How cool is that?
Again, match your tool selection to the work.
c. Soldering iron holder
The holder must raise the hot tip above the table work surface to
prevent charring. Don’t accept an iron holder that doesn’t have a
cage or wire spiral that will prevent anything from touching the hot
parts of the soldering iron. A simple stand isn’t good enough.
This simple soldering iron stand simply props the iron up away from the
table top. It is not acceptable because it won’t protect a
person’s hands from touching the hot iron. Find a holder with a
cage that covers the hot parts.
d. Wet cellulose sponge
Soldering stations almost always include a cellulose sponge in a water
tight tray. If your tools don’t have the sponge, buy a tray and
fit it with a small cellulose sponge. Cellulose resists melting
from the hot iron. Wet the sponge with as much water as it will
hold. Don’t squeeze water from the sponge. You can add water
to the tray to make the sponge saturated.
When a replacement sponge
is needed, buy a large cellulose sponge and trim it to fit. The
sponge will be hard when dry and can be trimmed with a razor or X-Acto
The reason for a saturated sponge is to provide enough water
to give the hot iron a thermal shock when it is wiped. The fast,
but short, reduction in tip temperature loosens scale or debris that has
settled on the tip. You should hear a hiss sizzle as the hot tip
touches the wet sponge. Two quick wipes are sufficient. The
iron has enough heating capacity to quickly recover from this reduction
in temperature. .
e. Heat sink tool, anti-wicking tool
We can prevent soldering heat
from conducting through the component leads causing heat damage to
semiconductors. Semiconductors are susceptible from soldering heat
damage. These heat sinks are made from aluminum which readily
conducts heat away from the component. Clamp the heat sink as near
to the component body as possible. The heat sink is removed as
soon as the soldering is completed.
f. Static strap
The anti-static wrist strap dissipates charges that build on a person’s
body. The wrist strap makes contact with the person’s skin and
the other end of the cable plug or clip connects to a ground connection
point on the workbench. Controlling static charges is vital when
handling metalic oxide or field effect solid state devices or any
equipment containing those components. A safe precaution is to
always use a static strap.
Use a commercial static strap; do
not make your own. Manufactured straps have internal
resistance which makes them safe for the user when working on energized
g. Cup or glass of cool water
The glass of water is for burn safety. Use a wide mouth open
cup or glass of water. Keep it near the soldering iron to
dip fingers if you’re unfortunate to have a burn accident.
h. Solder sucker
A hand operated vacuum device that will remove molten solder from a
terminal or pad. Heat the point with your soldering iron, quickly
place the sucker tip over the hot solder and press the button. A
plunger inside causes a vacuum which sucks the molten solder
inside. Press the other button to cock it for the next
removal. Occasionally open the barrel and remove the solder
This is an alternative to using solder wick. .
aids are available in an assortment of reamers, brushes, hook tips,
fork tips, and scrapers. These are the hand tools for positioning
wires or component leads on terminals or brushing, scraping for
soldering or solder removal.
Electronics Technicians use tools designed specifically for small
electronics components. We also find use of surgical knives,
hemostats, dental cleaning, mirrors, jewelers screwdrivers, gunsmith
tools, optical/camera clamps, modeling/clay tools, and artists
tools. If it works, adopt it.
Soldering alloys and fluxes
do-it-yourself technician will probably use solder in wire form.
Manufacturing has other forms such as bars heated to liquid, solder
paste, preformed solder shapes. The wire form used for electronics
construction or repair usually has an inner core of rosin flux.
Ensure that you are getting a rosin flux core solder and not acid core
which are not for electronics applications.
suppliers are a better source of rosin core solders in several wire
sizes. Hardware stores has acid core solders.
ROHS lead free solders comply with the European Union directive directing manufacturers to reduce certain chemicals in products.
of solders are too numerous to list here. Tin is the major
component. Lead is the next highest ingredient when it is used in
lead solders. Silver, copper, and Indium are ingredients in some
solders. You select the metal alloy to suit the job you are
making. Silver requires a higher temperature and is
stronger. Copper is an ingredient that preserves your soldering
iron tip, prevents the tip from sacrificing copper to the work.
Solder specifications show the melting temperature and the solidus
soldering flux is a metal surface cleaning fluid or a paste. Some
fluxes are inactive and some are acid. Acid based fluxes are not
acceptable for use in electronic devices. The acid flux must be
neutralized or it will cause corrosion of the equipment. Soldering
can be easier if the surface is prepped by using a liquid flux dropper
or a flux pen. This removes dirt, grease or corrosion from the
surface to be joined. Sometimes additional flux is used on
difficult to solder surfaces such as solar panels.
We normally use a solder wire form which has an inner core of solid flux. Additional flux isn’t normally needed.
The flux is activated when the soldering iron melts the alloy and
liquefies the flux. The flux flows over the surface and is replaced
with the molten metal.
Flux build up on cicuit pads is
unsightly. It can be removed with 91% alcohol on a stiff brush or
Q-tip. If a large amount of flux remains, it may be brittle and
can be chipped away with a soldering aid & wire brush.
a. Lead free solder.
This is ROHS compliant solder specified by the European Union Directive
for reducing hazardous chemicals in disposition. The lead has
been replaced with silver and trace amounts of other elements. A common
Sn/Ag/Cu alloy has a melting point of 423°F.
b. Lead alloy Solder
This is a ‘soft solder’. Major ingredients are tin (Sn) and
lead(Pb). Common types are 60/40 tin/lead, 50/50 common to stained glass
work, 63/37 lowest melting temperature. 63/37 tin/lead is a
eutectic solder, it’s melting point and solidus point are both at 361°F.
c. Solder wick is a length of braided copper tubing that is flattened and impregnated with a dried rosin flux.
Several widths are available
from 0.030” wide to 0.190” wide. This is used for removing solder
from a terminal or component pad. Solid copper braid works best
because it has the most surface area of copper to pull the solder.
First, flex the solder wick to ‘activate’ the impregnated dried
flux. Place the solder wick flat on the area of solder to be
removed. Apply the flat area of the soldering iron tip to the top
surface of the solder wick. Move, rock, soldering iron tip side to
side to achieve maximum contact of the iron tip to the wick. When
the heat is transferred through the copper wick to the solder, the
copper will wick the solder from the terminal into the copper
braid. Sometimes it may help to ‘prime’ the wick with fresh
solder..Remove the wick braid before removing the hot iron. You
will need to move the wick along to expose more wick as it fills with
solder. Cut off the solder filled wick with diagonal cutters to
start again with a fresh wick. The wicking process should take
only a few seconds. Watch for overheating damage of the component
that solder is being removed.
In this topic ‘wick’ is a noun and a
verb. Wick is a product used for desoldering. The verb wick
is the process of drawing solder away from the terminal.
See also Solder sucker topic.
d. Liquid flux or flux pen
Mil standards that regulate soldering alloys
Through Hole Soldering
a. The mechanical bond. Use
appropriate size smooth jaw needle nose pliers, bent tip pliers, round
jaw pliers, flush cutting diagonal pliers, etc to create a most perfect
position of the lead. The component should be firmly held before
solder is applied. Most components are mounted and secured in
place by their component leads. The components should not depend
on the solder to keep them in place. A solid mechanical connection
must be made before soldering. The component lead should be
brought around the terminal stud 270° only. Do not multiple wrap
the lead around a terminal. The minimum wrap allows easy removal
of failed components without damage to the terminal stud or the
board. A firmly mounted component won’t allow any movement while
the solder is solidfying. Movement in the joint while cooling will
cause a ‘cold solder joint’.
Wattage axial lead power resistors should be mounted above the circuit
board. Use the axial leads as stand-offs. These power
resistors are designed to handle internal heating by dissipating the
heat to the surrounding air. If the power resistor is in contact
with the board, it may char the board over time.
components leads should be straight for 0.2” to 0.4” before bending 90°
to be fastened to the board. This prevents stress on the lead
where it enters the component.
space reserved for describing the Davis supercap failure due to improper lead bending
insulation should be dressed to stop at the edge of the board
pad. Insulation should not be deformed or burned during the
soldering process. Insulation of the wires should not be in
contact with the solder.
b. The electrical connection The
solder bond should provide a low resistance path between all components
connected at the joint. If the joint wasn’t clean before
soldering or is a granulated cold joint, it can add significant
resistance in the circuit. A cracked joint due to vibration during
its service life can corrode and become a ‘rectifying’ junction. A
recitifying junction provides low resistance in one current flow
direction while high resistance in the other direction. This is
the same as if a diode were placed in the circuit; and the device
fails. Most cracked or cold joints can be repaired simply by
reheating with the soldering iron and a little flux. A cracked
joint is difficult to spot as a hairline in the solder above stressed
component leads. Defective solder joints are difficult to
troubleshoot. You can see that a wire is firmly in place; but it
may not be properly electrically connected.
c. The soldering process
The soldering illustration is owned by Bill Earl from https://learn.adafruit.com/assets/1978
1. mechanical cleaning
The items that are to be bonded must have a clean surface. The
solder adheres to the surfaces by ‘wetting’ If you are tinning insulated
stranded wire, first clip 1/4” or more from the end of the insulated
wire to get to bright copper wires for easier tinning. If copper
is dark, it can be brightned with a rubber eraser, brass brush or with
steel wool for large areas. The cleaning operation may leave its
own debris that must also be removed. Chemicals may be used in
this first cleaning but they may need to be washed and dried. Clean
copper is pink. Copper is a very active element. Copper will
remain clean for only a day. It oxidizes quickly. The lowly
‘Pots & Pans’ helper in a restaurant has to clean the copper pots
every single day with salt and vinegar.
2. flux application
Always use a flux core solder. There will be sufficient flux
without needing to apply more. If you apply additional flux, the
excess will need to be cleaned from the work. Liquid flux has a
solvent base which evaporates leaving the rosin as residue. The
rosin is non-conductive but may become dirty and cause less than optimum
performance of the circuit.
Some difficult to solder items such as
solar panels may need to be pre-fluxed with a liquid or paste so that
the solder will flow quickly and without much mechanical pressure from
3. heat application
Remove the soldering iron from its holder. Wipe the iron tip on a
very wet cellulose sponge listening for the hiss as the heat evaporates
water. This is very important to temperature shock the iron tip
and loosen debris on the tip. Wiping will remove most of solder
that remained after the last soldering operation.
THROW MOLTEN SOLDER FROM THE IRON! To do so is like random firing
of a weapon. It is dangerous and unnecessary. Inspect the iron
occasionally for pitting and areas that are not tinned.
4. solder alloy delivery
Heat and alloy application occurs simultaneously. Bring the
solder wire to the work while touching the iron to the same point.
Apply pressure with the iron against the work and the end of the
solder. Start a molten solder bridge between the iron and the
work. You want maximum contact for quick heat transfer to the
work. Do not lay the iron on top of the solder wire. This
will heat the inner flux core and cause spitting of the flux which is
dangerous to the technician and contaminates components. Remove
the solder and iron together. Watch for a shiny surface when the
solder becomes solid. If the work is moved, it will become a ‘cold
solder joint’ with a grainy appearance. Fix the cold solder joint
by applying a very small bit of solder & flux while heating. A
cold solder joint is resistive and unreliable.
More solder on a
joint is not better. Apply only enough solder to give a good
contour around the joint. A ball shaped joint is
unacceptable. You should see the shape of the wire as it bends
around a terminal.
5. post cleaning and inspection Watch
the joint cooling as soon as the soldering iron is removed. The
solder surface should remain shiny. A dull or grainy appearance
may have been caused by the components moving before the alloy
Inspect for the proper quantity of solder and the
contour over the pad and component leads. Add more solder or
remove with a wick to get the perfect joint.
Check for solder bridges between board pads and traces. Remove excess solder with a solder sucker or with a wick.
at the component side of a circuit board to be sure that the component
is properly placed, usually firmly against the board, not moved away
during the soldering process.
Surface Mount Device Soldering
a. The mechanical bond.
Surface mounted components have no excess lead length. To build a
circuit, the components are mounted on a circuit board or a chip
carrier board which adapts the small components to a larger circuit
board. The surface mounted devices will be hereafter referred to
as SMD. Passive SMD are resistors, capacitors, diodes, LEDS,
inductors. Active SMD are integrated circuits, transistors, and
sensors. Switches and actuators are sometimes packaged as SMD.
b. The electrical connection The solder bond provides a low resistance path between the component and the circuit board.
c.. The soldering process Select
one lead of a component or a corner lead of a large package; apply a
small dot of solder to the corner circuit board pad before placing the
component. Place the component in its proper orientation.
Hold it in place with gentle pressure on the device with a tweezer,
probe, etc and apply heat at the lead/pad junction for 1.5
seconds. The component should settle down through the solder to
the base metal pad. Remove the soldering iron while continuing to
hold the component in place with the probe.
Inspect that component
terminal and next solder the diagonally opposite terminal on a multi pin
device by adding solder while applying heat. Repeat on the
remaining component terminals.
1. mechanical cleaning
The circuit board must be thoroughly cleaned and tinned before the
components are placed. An amount of solder is applied to the
pad. The cleaning process can use alcohol or a solvent depending
on the board. A silk screened board may not tolerate a
solvent. Tinning is the process of applying a small amount of
solder to the SMD pads on the circuit board. Some DIY may be
assembling a kit of parts. Others make our own boards.
2. flux application An adequate amount of flux should be applied in the solder core or using a flux applicator.
3. heat application
An adequate amount of heat is necessary to make a quick solder.
Be sure that the iron is clean, the solder wire is clean, and the iron
tip is clean and tinned. The
SMD can be soldered manually with a small tip soldering iron or by
heating the entire circuit board in a preheated oven. Hot air
should be investigated as a method of small job soldering.
4. solder alloy delivery The
solder alloy can be applied before the component is placed above the
cooled solder before heating in an oven. Or the solder alloy can
be applied similarily to the lead/pad junction as with through hole
5. post cleaning and inspection
Check for solder bridges between board traces. Components and
circuit boards have smaller clearances which make it more likely to
bridge between pads/traces. Check that the component didn’t move
during the soldering or oven process. The component pins should be
in perfect alignment with the board pads.
The Ten Commandments for soldering
When touching the work with the iron, try to contact the part of the
greater mass with the flat (larger) part of the tip while trying to
touch the part of the smaller mass with the side or edge (smaller part).
Immediately on tool-to-work contact, create a fast heat bridge by
placing the core solder in the gap. This will melt the flux and
then some solder, which will permit localized wetting for rapid heat
Once the core solder starts melting, draw it around the joint in the
direction of flow (good for large connections). If the fillet is
small, feed the solder steadily to the junction of tip and work.
4 Remove the solder first, provided that sufficient metal has been added to the joint.
5 Next, remove the iron, but only after the solder has reached the desired contour as dictated by surface tension.
6 Allow the solder to freeze without vibration to avoid disturbed joints.
7 Always place the heat (soldering iron tip) on the side opposite insulation and heat sensitive components
8 Do not melt solder on top of the soldering iron tip and carry it to the work (puddling), unless the work was prefluxed.
Do not place the soldering iron on top of core solder or interpose core
solder between the work and the tip; flux will spit and not run onto
10 Do not pull or push on solder joint for inspection.
The Ten Commandments of Soldering is from “Solders and Soldering”, Howard H. Manko
materials can be soldered if the surfaces are prepared and the propper
flux and alloys are used.. We normally solder to a copper surface
or to components that have been tin plated. Tinning a wire or
component means that we are precoating it with molten solder (which is
tin). It is possible to solder to stainless steel, brass, silver,
gold. We can even solder to ceramic, graphite, and glass.
Those are specialities that the DIY won’t need. A tin/lead solder
will easily adhere to a gold plated surface. However, soldering to
gold contact areas of components is not acceptable. The amalgam
of gold and tin is brittle and the solder joint will fail
prematurely. The gold plating must be mechanically removed
(scraped) before soldering to it.
Relating lead alloy soldering, to homes with lead found in old painted walls:
are required to control access during the removal of lead paint from
structures. The lead in old walls may be a small amount of
lead compared to our soldering supply of lead. We may purchase a
lead alloy solder in a 1 pound roll. How many square feet of walls
would contain the same quantity of lead? My point is that
we must be considerate of exposure to and control our use of lead alloy
Solders and Soldering, Howard H. Manko 0-07-039970-0
Soldering Manual, American Welding Society 0-87171-151-6
Suggested How To Solder links:
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LAST CHANGED ON 2014.06.12