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soldering techniques

I. Soldering - The joining of metals by fusion of alloys which have relatively low melting points.
A. Basic Equipment used in Soldering:
1. Soldering Iron
– The heat source used to melt solder.
– Use 20W to 40W soldering iron range for electronics printed circuit board
2. Soldering Iron Stand
– Use to hold soldering iron.
3. Soldering Lead (solder)
– It is an alloy (Mixture) of Tin and Lead, typically 60% tin and 40% lead use
to join two metal surfaces.
– It melts at a temperature of about 190 deg C.
– Solder for electronics use contains tiny cores of flux, which cleans the
metal surfaces as the solder melts.
– Available soldering lead are 40/60, 50/50, 60/40, 63/37, 95/5. The most
common used is 60/40.
– Solder Mixture:
Melting Point
460 deg F (230 deg C)
418 deg F (214 deg C)
374 deg F (190 deg C)
364 deg F (183 deg C)
434 deg F (224 deg C)
II. First Few Safety Precautions:
A. Never touch the element or tip of the soldering iron.
B. Take great care to avoid touching the main flex with the tip of the iron.
C. Always return the soldering to its stand when not in use.
D. Work in a well-ventilated area.
E. Wash your hands after using solder.
III. Preparing the Soldering Iron:
A. Place the soldering iron on its stand and plug in.
B. Dampen the sponge in the stand.
C. Wait for a few minutes for the soldering iron to warm up.
D. Wipe the tip of the iron on the damp sponge.
E. Melt a little solder on the tip of the iron.
IV. Soldering Process:
A. Hold the soldering iron like a pen, near the base of the handle. Imagine you are going
to write your name.
B. Touch the soldering iron onto the joint to be made. Make sure it touches both the
component lead and the track. Hold the tip there for a few seconds (2 – 3 sec).
C. Feed a little solder onto the joint.
D. Remove the solder, then the iron, while keeping the joint still. Allow the joint a few
seconds to cool before you move the circuit board.
E. Inspect the joint closely. It should look shiny and have a volcano shape. If not, reheat
the joint making sure that the lead and the track are heated fully before applying the
Note: Right amount of solder:
A. Minimum amount of solder
B. Optimal
C. Excessive
Note: Improper amount of solder:
A. Bad solderability of terminal wire
B. Bad soldering of PCB
C. Bad soldering of terminal wire of PCB
Note: Refrain from a having a Cold Solder Joints.
- A cold solder Joints is a joint in which the solder does not make contact with the
component lead or printed circuit board.
- Cold joints can be recognized by a characteristic grainy, dull gray color, and can be
easily fixed.
V. Some Useful Tips in Soldering
A. Use Heat Sinks
Keep the iron tip clean
Double check joints
Use the Proper Iron
Solder Small Parts First
VI. Summary of How to Make the Perfect Solder Joints
A. All parts must be clean and free from dirt and grease.
B. Try to secure the work firmly
C. Tin the iron tip with the small amount of solder
D. Clean the tip of the soldering iron on a damp sponge.
E. Add tiny amount of fresh solder to the cleansed tip.
F. Heat all the parts of the joint with the iron for under a second or so.
G. Continue heating, then apply a sufficient solder only to form an adequate joint.
H. Remove and the ion safely to its stand.
I. It only takes two or three seconds at most, to solder the average PCB joint.
J. Do not move parts until the solder has cooled.
VII. Using a Desoldering Pump(Solder Sucker)
A. Desoldering is required when electronic components need to be removed from the
B. Steps in Using Desoldering Pump
1. Set the pump by pushing the spring-loaded plunger down until it locks.
2. Apply both the pump nozzle and the tip of the soldering iron to joint.
3. Wait a second or two for the solder to melt.
4. Then press the button on the pump to release the plunger and suck the molten
solder into the tool.
5. Repeat if necessary to remove as much solder as possible.
VIII. First Aid
- If you accidentally receive burns which require treatment:
1. Immediately cool the affected area with cold water or ice for several minutes
2. Remove any rings etc, before swelling starts.
3. Apply sterile dressing to protect against infection.
4. Do not apply lotions, ointments nor prick any blisters which form later.
5. Seek professional medical advice if necessary.