How To Make a Perfect Soldering Joint- halfstudents.in
The most fundamental skill needed to assemble any electronic
project is that of soldering. It takes some practice to make the perfect joint,
but, like riding a bicycle, once learned is never forgotten! The idea is
simple: to join electrical parts together to form an electrical connection,
using a molten mixture of lead and tin (solder) with a soldering iron.
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Soldering is a very
helpful technique by which we can design any circuit with a professional way on
PCB. It is like welding, but this time we are not welding two iron parts but
some electronic components.
SEE VIDEO HOW TO MAKE PROPER SOLDERING JOINT CLICK HERE
Soldering material:
An alloy of tin and lead called solder (63% tin and 37%
lead), is normally used to ‘metallurgically’ bind a component pin/leg to the copper
track of a circuit.
There are also some other kind of soldering material which
are commonly available( 60% tin and 40% lead).
Lead is very dangerous for health due to its poisonous
nature. So lead-free soldering material is also available in the market although it
is costly and needs more practice to make a perfect soldering joint, due to
having more melting point than leaded solder. (lead-free soldering need more
temperature than leaded solder )
Soldering flux:
It is a type of grease that is used to give proper joint between the wires and soldering material. flux is very useful when we have to cure the dry joints in the circuit.
Soldering irons :
Soldering irons are the main structural unit of soldering and these are available in many varieties of soldering iron
which are dependent on voltage, heater valve, and wattage are classified below:
Voltage:
Most irons run from the mains at 220V. However, low
voltage types (e.g. 12V or 24V) generally form part of a "soldering station"
and are designed to be used with a special controller made by the same
manufacturer. We can also design a portable soldering iron but this is only
possible when we are using 12volt soldering iron. Just we need to connect a
battery it may be of lithium and we can perform better soldering anywhere in
the world.
Wattage:
Typically, they may have a power rating of between
15-25 watts or so, which is fine for most work. A higher wattage does not mean
that the iron runs hotter - it simply means that there is more power in reserve
for coping with larger joints. This also depends partly on the design of the
"bit" (the tip of the iron). Consider a higher wattage iron simply as
being more "unstoppable" when it comes to heavier-duty work because
it won't cool down so quickly. Wattage is more important when we are
performing a big task, which means where we need a huge soldering joint to make the
components bind.
Otherwise, we can simply use a low wattage soldering iron to
design our regular circuits.
Temperature Control:
The simplest and cheapest types don't
have any form of temperature regulation. Simply plug them in and switch them
on! Thermal regulation is "designed in" (by physics, not
electronics!): they may be described as "thermally balanced" so that
they have some degree of temperature "matching" but their output will
otherwise not be controlled. Unregulated irons form an ideal general-purpose
iron for most users, and they generally cope well with printed circuit board
soldering and general inter wiring. A proper temperature-controlled iron will
be quite a lot more expensive.
Temperature control soldering irons can also be designed
using some electronic microchips and giving programming to them.
CLICK HERE to see how
to make a temperature control soldering iron
Turning to the actual techniques of soldering, firstly it's
best to secure the work somehow so that it doesn't move during soldering and
affect your accuracy. In the case of a printed circuit board, various holding
frames are fairly popular especially with densely populated boards: the idea is
to insert all the parts on one side ("stuffing the board"), hold them
in place with a special foam pad to prevent them from falling out, turn the board
over and then snip off the wires with cutters before making the joints.
Proper soldering Technique:
The frame saves an awful lot of turning the board over and over, especially with large boards.
Other parts could be held firm in a modeler's small vice, for example. Solder
joints may need to possess some degree of mechanical strength in some cases,
especially with wires soldered to, say, potentiometer or switch tags, and this
means that the wire should be looped through the tag and secured before solder
is applied. The downside is that it is more difficult to de-solder the joint
and remove the wire afterward, if required. Otherwise, in the case of an
ordinary circuit board, components' wires are bent to fit through the board,
inserted flush against the board's surface, splayed outwards a little so that
the part grips the board and then soldered. Integrated circuits can either be
soldered directly into place if you are confident enough, or better, use a
dual-in-line socket to prevent heat damage. The chip can then be swapped out if
needed. Parts that become hot in operation (e.g. some resistors) are raised
above the board slightly to allow air to circulate. Some components, especially
large electrolytic capacitors may require a mounting clip to be screwed down
to the board first, otherwise, the part may eventually break off due to
vibration.
Desoldering techniques
A soldered joint that is improperly made will be
electrically "noisy", unreliable and is likely to get worse in time.
It may even not have made any electrical connection at all, or could work
initially and then cause the equipment to fail at a later date! It can be hard
to judge the quality of a solder joint purely by appearances because you
cannot say how the joint actually formed on the inside, but by following the
guidelines there is no reason why you should not obtain perfect results. A
joint which is poorly formed is often called a "dry joint". Usually, it results from dirt or grease preventing the solder from melting onto the
parts properly and is often noticeable because of the tendency of the solder
not to "spread" but to form beads or globules instead, perhaps
partially. Alternatively, if it seems to take an inordinately long time for the
solder to spread, this is another sign of possible dirt and that the joint may
potentially be a dry one. There will undoubtedly come a time when you need to
remove the solder from a joint: possibly to replace a faulty component or fix a
dry joint. The usual way is to use a desoldering pump or vacuum pump which
works as a small spring-loaded bicycle pump, only in reverse! A spring-loaded plunger is released at the push of a button and the molten solder is then drawn
up into the pump. It may take one or two attempts to clean up a joint this way,
but a small desoldering pump is an invaluable tool especially for p.c.b. work.
Sometimes, it's effective to actually add more solder and then desolder the
whole lot with a pump, if the solder is particularly awkward to remove. Care is
needed, though, to ensure that the boards and parts are not damaged by
excessive heat; the pumps themselves have a P.T.F.E. nozzle which is heatproof
but may need replacing occasionally. An excellent alternative to a pump is to
use desoldering braid, including the famous American "Solder-Wick"
(sic) or Adcola "TISA-Wick" which are packaged in small dispenser
reels. This product is a specially treated fine copper braid which draws molten
solder up into the braid where it solidifies. The best way is to use the tip of
the hot iron to press a short length of braid down onto the joint to be
de-soldered. The iron will subsequently melt the solder, which will be drawn up
into the braid. Take extreme care to ensure that you don't allow the solder to
cool with the braid adhering to the work, or you run the risk of damaging
p.c.b. copper tracks when you attempt to pull the braid off the joint. That is
why buying a small reel of de-soldering braid, especially for larger or
difficult joints which would take several attempts with a pump is recommended.
It is surprisingly effective, especially on difficult joints where a
desoldering pump may prove a struggle.
SEE VIDEO CLICK HERE
how to desolder properly
How to make the perfect solder joint.
1. All parts must be clean and free from dirt and grease.
2. Try to secure the work firmly.
3. "Tin" the iron tip with a small amount of solder. Do this immediately, with new tips being used for the first time.
4. Clean the tip of
the hot soldering iron on a damp sponge.
5. Many people then add a tiny amount of fresh solder to the
cleansed tip.
6. Heat all parts of the joint with the iron for under a
second or so.
7. Continue heating, then apply sufficient solder only, to
form an adequate joint.
8. Remove and return the iron safely to its stand.
9. It only takes two or three seconds at most, to solder the
average PCB joint.
10. Do not move parts until the solder has cooled.
Troubleshooting Guide
• Solder won't
"take" - grease or dirt present - desolder and clean up the parts.
Or, material may not be suitable for soldering with lead/tin solder (e.g.
aluminum).
• Joint is crystalline or grainy-looking - has been moved
before being allowed to cool, or joint was not heated adequately - too small an
iron/ too large a joint.
• Solder joint forms
a "spike" - probably overheated, burning away the flux.
If there are spikes
on soldering then apply soldering flux to make a proper joint.
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