Soldering Technique

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Soldering Technique

soldering is the process of joining of two metals for a permanent joint. The bounding of two metals done by using alloy of two metals lead and tin called solder in different ratios to solder electronic component like resistors, capacitor, transistor etc.

Soldering a joint : – Selection and preparation of the soldering materials and cleaning the surface to be soldered are the most time consuming phase of making a solder joint. Heating the joint and applying solder is the least time consuming but, all this steps contribute heavily for the good soldered joint.

Critical factor during soldering

1 .  controlling the temperature of the workpiece.
2 . Limiting the time that a workpiece is to be held at soldering temperature.

These factors are specially critical while soldering electronic components like resistors, capacitors, transistors, ICs etc. Failure of correct time and coordinate the heating of the joint and add solder, will result in a poor quality joint and may even damage the components.

Stage in Soldering :- The soldering process can be divided into several distinct stage or phases as given below.
1 . Selection and preparation of materials.
2 . Cleaning the surface to be soldered.
3 . Heating the joint and adding solder.
4 . Cooling the joint.
5 . Cleaning the joint.
6 . Inspecting the joint.

Selection and preparation of materials

1 . Selection of soldering iron wattage : – Soldering irons are available in different wattage ratings starting from 10 watts to several 100 watts. The wattage of a soldering iron specifies the amount of heat it can produce. As a thumb rule, higher the physical dimension of the workpiece, higher should be the wattage rating of the soldering iron. Some of the suggested wattage of soldering iron are given below .,
(a) For soldering, less temperature sensitive component such as, resistors on lug boards or tag boards, use 25W to 60W iron. For soldering on printed circuit boards, use 10W to 25W iron.
(b) For soldering highly temperature sensitive components such as, diodes, transistors and integrated circuits, use 10 watt to 25 watt iron.

2 . Cleaning the surface to be soldered :- Before joining two pieces of metal by soldering, the joining surface should be cleaned to remove foreign matters over the surface.

3 . Heating the joint and adding solder : –

(a) Do not apply too much flux on a joint in one place. Apply a small amount of flux around the joint. Do not allow the flux to flow outside the area to be soldered.
(b) Place the iron tip at the joint such that the tip gets maximum contact with parts to be jointed.

4 . Cooling the joint : – Allow the joint to cool without assistance, do not blow air from your mouth or from any other source to cool the joint. Forced cooling, cools the joint much earlier than it has to , resulting in a dry and brittle solder joint which will lead to mechanical and electrical defects of the joint.

5 . Cleaning the joint ;-  When a solder joint is made, the amount of flux applied should be just sufficient to make a good joint.

6 . Inspection of soldered joints :- Soon after making a solder joint, as a quick check, the following features of the solder joint should be checked :
(a) Soldered joint must be bright and shiny.
(b) Soldered joint must be smooth and symmetrical.



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