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Learn to Solder
Electronic Training Course
Slide# 1
Learn to Solder
What is the Purpose for
Soldering in Electronics?
Slide# 2
Learn to Solder
Soldering is the process of joining metal leads to create a
mechanical and electrical bond. In the figure above, the
lead of the resistor and the pad of the circuit board are
mechanically attached and electrically connected.
Slide# 3
Learn to Solder
Mechanically attached means that the lead of the resistor
and the pad on the board are bonded and cannot easily
be separated. Electrically connected means that current
can flow between the lead of the resistor and the pad on
the board with practically no resistance.
Slide# 4
Learn to Solder
Tools needed in the soldering process: safety glasses, soldering
iron, solder, wire cutters, and a damp sponge.
It is important to always wear the safety glasses during the whole
soldering process to protect your eyes against boiling solder
particles that get ejected while the solder is melting and from cut
off leads that might fly in any direction when they are cut.
Slide# 5
Learn to Solder
The soldering iron is the tool used to heat the joint. It has a tip that
is heated by an internal heating element. The picture shows two
common types of soldering irons: the pencil and the controlled
temperature type. Soldering irons have a wattage rating that
indicates their capacity to transfer heat to the joint. Wattage ratings
of 35 to 45 watts are the recommended for electronics.
Slide# 6
Learn to Solder
Solder is the material that melts on the joint attaching to both the
component lead and the pad on the circuit board. Solder is made of a
tin and lead mix. The ratio of tin and lead determines the melting
point and the hardness of the solder. A common type of solder used in
electronics is the SN63, which contains 63% tin and 37% lead. All
types of solder used in electronics contain a central core of rosin flux.
Slide# 7
Learn to Solder
Solder used in electronics contains a central core of rosin flux. As the
solder melts during the soldering process attaching to the component
lead and the pad, the flux flows into the joint dissolving existing
oxides on the leads and preventing the formation of new ones. This
facilitates the formation of a good soldering joint.
Slide# 8
Learn to Solder
The Soldering Process
Step 1: Prepare component for mounting
In this step you bend the leads of the component at a 90 degree angle
to fit into the holes of the circuit board. You can do this with your
hand or with the help of pliers. You have to be sure that the leads are
bent at the right distance from the body of the component so they fit
comfortably into the holes in the board.
Slide# 9
Learn to Solder
The Soldering Process
Step 2: Mount component on board
In this step you insert the leads of the component into the holes on
the board from the component side. The body of the component
should rest on the component side of the board. It is incorrect to
install the component on the soldering side (foil side) of the board
instead of the component side, or to install the component away from
the surface of the board instead of resting on the surface of the board
as shown in the figure.
Slide# 10
Learn to Solder
The Soldering Process
Step 3: Bend component leads slightly
After you inserted the leads of the component into the holes on the
board, you should bend the component leads slightly to hold the
component in place (not falling) while the board is turned over to be
soldered.
Slide# 11
Learn to Solder
The Soldering Process
Step 4: Clean the soldering iron tip
Before you start soldering and after the tip of the iron has heated up,
the tip of the iron should be cleaned on a damp sponge and tinned by
melting a piece of solder on the iron's tip and then wiping the tip in
the damp sponge again.
The tip of the iron should always have an even shinny metal surface
from the solder. Each time oxide forms on the tip, clean the tip on the
damp sponge to make it shiny again.
Slide# 12
Learn to Solder
The Soldering Process
Step 5: Apply heat
In this step you apply heat to the joint to be soldered by touching the
tip of the iron firmly against both the component lead and the pad on
the board simultaneously. Allow about three seconds or more for the
joint to heat up before applying the solder. This is one of the most
important steps in the soldering process. If you do not heat up the
joint (lead and pad on the board) sufficiently you will get a cold
soldering joint which will have to be resoldered.
Slide# 13
Learn to Solder
The Soldering Process
Step 6: Apply Solder
After the joint has heated up, apply solder to the point where the lead
and the pad join. Apply enough solder the create a "mountain” of
solder that attaches to both the lead and the pad as shown in the
drawing.
A common soldering problem is to apply too little or too much solder,
either case is not good and might require resoldering.
Slide# 14
Learn to Solder
The Soldering Process
Step 7: Remove solder
After the solder has melted on the joint forming a nice connection like
the one shown above remove the solder from the joint.
Step 8: Remove iron
After the solder has been removed, remove the iron from the joint.
Slide# 15
Learn to Solder
The Soldering Process
Step 9: Inspect the soldering joint
After the joint has cooled off, visually inspect the joint that you have
created. It should have a shiny and smooth surface and it should
attach to both the component lead and the pad on the board. Slide 19
shows what good and bad soldering joints look like. If the solder
connection is not good it will have to be resoldered. This is done by
reheating the connection until the existing solder melts then
retouching the connection with slightly more solder.
Slide# 16
Learn to Solder
The Soldering Process
Step 10: Cut off component leads
After you have soldered a joint the next step is to cut off the excess
component leads using a cutter. Trim the lead of the component as
close to the solder joint as possible. This is another important step in
the assembly process that cannot be avoided because non-trimmed
component leads might cause short circuits between metallic traces
on the board or other component leads.
Slide# 17
Learn to Solder
Once soldering has been
completed, how can a good
solder joint be identified
compared to a bad solder joint?
Slide# 18
Learn to Solder
Good soldering joint
As we have said before, a good soldering joint has a shiny
and smooth surface and attaches to both the component
lead and the pad on the board.
Slide# 19
Learn to Solder
Cold soldering joint
You can recognize a cold solder joint because it is dull (not
shiny) and irregular (not smooth). Cold solder joints do not
make good electrical connections and should be resoldered.
Slide# 20
Learn to Solder
Solder not attached to lead
In this type of defective soldering joint the solder is
attached to the pad of the board but not to the lead of the
component. In some cases this is very obvious to see, but in
other cases only a careful inspection of the joint will identify
this problem, because even when the solder is surrounding
the component lead it might not attach to it. If in doubt
always resolder the joint.
Slide# 21
Learn to Solder
Solder not attached to pad
In this type of defective soldering joint the solder is
attached to the lead of the component but not to the pad of
the board. In some cases this is very obvious and easy to
detect but in other cases only a careful inspection of the
joint will identify this problem. In these cases the solder is
resting upon the pad but does not attach to it and there is a
layer of rosin between the pad and the ball of solder. If in
doubt always resolder the joint.
Slide# 22
Learn to Solder
Leads not trimmed
This problem is caused by not trimming the component
leads after soldering the joint. Non-trimmed leads are an
immediate and potential problem because they can be
touching each other or touching other parts of the traces,
producing short circuits and damaging the components.
Never leave un-trimmed leads after soldering is completed.
Slide# 23
Learn to Solder
Solder bridges
A solder bridge is a bridge made with solder that is
connecting two traces of the board that should not be
connected. Sometimes solder bridges are easy to detect and
other times they are so tiny that they can only be detected
with the use of a magnifying glass. Solder bridges can be
eliminated by melting them with the soldering iron.
Slide# 24
Learn to Solder
Review
The basic tools and materials needed for soldering are:
- Safety Glasses
- Soldering Iron
- Solder
- Wire Cutters
- Damp Sponge
Soldering irons are used to heat the connection or joint
before applying solder. The wattage rating of a soldering
iron indicates its ability to transmit heat. A rating of 35-45
watts is recommended for electronics.
Slide# 25
Learn to Solder
Review
Solder is melted by the heated joint between the circuit
board and component lead to make an electrical and
mechanical connection (heating the solder directly with the
iron will cause faulty connections). Solder is made of a tin
and lead mixture around a rosin core.
The soldering process contains 10 steps.
(Slides 9-17 show each step in detail)
After soldering, each connection needs to be inspected for
good connections. Electronics with bad solder joints will
not work correctly and might become damaged from shorts.
Slide# 26
Learn to Solder
Test
The figure shows a _____.
The figure shows a _____.
The purpose of the soldering iron is to_____.
Solder is made from mixture of _____.
Solder used in electronics contains a central core of _____.
Slide# 27
Learn to Solder
Test
The figure shows a _____.
Soldering Iron
The figure shows a _____.
The purpose of the soldering iron is to_____.
Solder is made from mixture of _____.
Solder used in electronics contains a central core of _____.
Slide# 28
Learn to Solder
Test
The figure shows a _____.
Soldering Iron
The figure shows a _____.
Coil of Solder
The purpose of the soldering iron is to_____.
Solder is made from mixture of _____.
Solder used in electronics contains a central core of _____.
Slide# 29
Learn to Solder
Test
The figure shows a _____.
Soldering Iron
The figure shows a _____.
Coil of Solder
The purpose of the soldering iron is to_____.
Heat the Joint
Solder is made from mixture of _____.
Solder used in electronics contains a central core of _____.
Slide30
Learn to Solder
Test
The figure shows a _____.
Soldering Iron
The figure shows a _____.
Coil of Solder
The purpose of the soldering iron is to_____.
Heat the Joint
Solder is made from mixture of _____.
Tin and Lead
Solder used in electronics contains a central core of _____.
Slide# 31
Learn to Solder
Test
The figure shows a _____.
Soldering Iron
The figure shows a _____.
Coil of Solder
The purpose of the soldering iron is to_____.
Heat the Joint
Solder is made from mixture of _____.
Tin and Lead
Solder used in electronics contains a central core of _____.
Rosin Flux
Slide# 32
Learn to Solder
Test
In a good soldering joint the solder should connect to _____.
The figure shows a _____.
The figure shows a _____.
The figure shows a _____.
The figure shows a _____.
Slide# 33
Learn to Solder
Test
In a good soldering joint the solder should connect to _____.
The metallic pad and component lead
The figure shows a _____.
The figure shows a _____.
The figure shows a _____.
The figure shows a _____.
Slide# 34
Learn to Solder
Test
In a good soldering joint the solder should connect to _____.
The metallic pad and component lead
The figure shows a _____.
Good solder joint
The figure shows a _____.
The figure shows a _____.
The figure shows a _____.
Slide# 35
Learn to Solder
Test
In a good soldering joint the solder should connect to _____.
The metallic pad and component lead
The figure shows a _____.
Good solder joint
The figure shows a _____.
Cold solder joint
The figure shows a _____.
The figure shows a _____.
Slide# 36
Learn to Solder
Test
In a good soldering joint the solder should connect to _____.
The metallic pad and component lead
The figure shows a _____.
Good solder joint
The figure shows a _____.
Cold solder joint
The figure shows a _____.
Joint with un-trimmed leads
The figure shows a _____.
Slide# 37
Learn to Solder
Test
In a good soldering joint the solder should connect to _____.
The metallic pad and component lead
The figure shows a _____.
Good solder joint
The figure shows a _____.
Cold solder joint
The figure shows a _____.
Joint with un-trimmed leads
The figure shows a _____.
Joint with solder not
Attached to the pad
Slide# 38