Soldering
Soldering: Soldering is the process of joining
two metal plates or conductors without melting them, with an alloy called
solder.
Necessity of soldering: cable joints are soldered to have
good mechanical strength, electrical conductivity and also to avoid corrosion.
Solder: solder is an alloy of tin &
lead, whose melting point is lower than that of the metals to be soldered. .
Factors that influence the choice of a solder are: place of use, melting point,
solidification range, strength, hardness, seal-ability and price. There are two
types of solder:
- Soft solder (contain lead and tin and
requires low temperature of 150°C to 300°C but if some percentage of
antimony and bismuth is added in lead and tin, its melting point comes to
96°C
- Hard solder (Hard solder is used for plumbing purposes and
requires high temperature of 350°C to 600°C. The compositions of these
solders for different purposes)
Difference
between Soft Soldering & Hard Soldering
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Soft
Soldering |
Hard
Soldering |
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Flux: Flux is a substance used to
dissolve oxides on the surface of conductors and to protect against
de-oxidization & to facilitate the flow of the solder through surface
tension during the soldering process. The state of the flux can be solid or
liquid.
Methods
of soldering:
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Soldering with a soldering iron: The most
common method of soldering is with a soldering iron. This is widely used for
most kinds of soft soldering work.  |
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Temperature controlled soldering: A soldering station
consists of a soldering iron
whose temperature is controlled through an electrical
power supply.  |
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Soldering with a soldering gun: Soldering
guns are used for individual soldering, e.g. for servicing and
repair work.  |
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Soldering with a flame or blow
lamp: This
method, permits rapid heating and is used primarily for larger jobs, such as
piping and cable work, vehicle body repairs etc.  |
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Dip soldering: Dip
soldering is a soldering process by which electronic components
are soldered to a printed circuit board (PCB) to form an electronic
assembly. The solder wets to the exposed metallic areas of the
board.  |
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Machine soldering: This
method is used for quantity production, and is based on the principle that
molten solder or a mixture of oil and molten solder is set in rapid motion,
thus breaking up the oxide film. The solder comes into direct contact with
the component ends to be soldered. Soldering machines of different designs
are used for wave soldering, cascade soldering and jet soldering.  |
Soldering Iron: The heating element in the iron is
heated by an electric current passing through it. The bit is heated by the
heating element. The face of the bit is the part of the iron, used to make
contact with the surfaces to be soldered.
Bit: Most bits are made of copper
because it is a good conductor of heat. The face of the bit may be either:
un-plated & iron-plated (Iron-plated faces do not wear out as rapidly as
un-plated faces).
Cleaning the bit: To clean the bit, rub the face of
the un-plated bits on a wire brush or special sponge pad when the iron is hot.
Iron-plated bits must not be cleaned on a wire brush. Rub on a sponge pad.
Wetting (soldering): To make a good joint, the solder
must flow evenly over and between the surfaces to be soldered.
Tinning the soldering iron: A coating of solder is applied to
the tip of the soldering iron, the surface of the tip must be coated with the
solder, this operation is known as tinning.
Soldering
with pot and ladle:
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·
For larger sized jobs like underground cable jointing, a melting
pot and ladle are used. ·
The solder is kept in the pot and heated either by a blowlamp or
by charcoal. Initially the surface to be soldered is cleaned and a coat of
flux is given. ·
Then the surface to be soldered is heated by pouring molten
solder over it in quick. ·
The dripping solder is collected in a clean tray, solder
collected in the tray is re-melted in the pot. ·
The flux is again applied and the solder is slowly poured on the
surface as it forms an even layer. |
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Soldering aluminium cables:
- · Soldering aluminium conductors is more difficult than soldering copper conductors because aluminium forms oxide layer when exposed to air. This oxide film does not allow the solder to wet the surface to be soldered, and also prevents the solder from entering the interior surface. Hence special solders and fluxes are used for aluminium soldering.
- · A typical composition of solder with 51% lead, 31% tin, 9 % zinc and 9% cadmium with the brand name “ALCAP” solder and “Ker-al-lite” is available for soldering aluminium conductors or cables.
- · Organic fluxes (free from chlorides) of reaction type are used for soldering aluminium cable. The composition of the organic fluxes decomposes at approximately 250°C to effect the removal of the oxide film and also to assist in the spreading of the molten solder to enable tinning the de-oxidised surface immediately. The major disadvantage of organic flux is that it tends to char (burns & would not allow proper soldering) at a temperature above 360°C. The name of fluxes used for joining aluminium conductors are “Kynal Flux” and “Eyre No.7”.
Difference
between Soldering & Brazing
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Soldering |
Brazing |
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