How to Solder Wire to PCB?

How to Solder Wire

When the circuit board is ready, the next step is low volume PCB assembly. One of the steps in the low volume PCB assembly of the board is soldering. It is the process of joining the mechanical components to the electric ones. It connects two metals solidly using another element called solder.

What is a Solder? 

Solder is a metal alloy with a low melting point. There are different types of solder. The one usually used to be an alloy of lead. It melts and hardens quickly, which helps in quick and easy soldering. But due to the health hazards of lead alloys, lead-free alloys are also being utilized. The lead-free alloys include silver, tin, and copper. These metals have higher melting points.

The choice of the metal for soldering rests on the characteristics of the metal. The solder should be resistant to corrosion and oxidation to avoid degradation. It should be able to pass electrical currents efficiently.

Steps of Soldering Wire to the PCB:

Soldering creates a permanent connection between the wire and the circuit board. It is used as a part of the manufacturing or repairing the PCB. The steps of soldering wire to the PCB are given below:

  1. The circuit board and the wire are cleaned using an eraser until they are clean and shiny. 1/4th of the insulated covering of the wire is removed.
  2. The soldering iron tip is pre-tinned, and a small amount of solder is liquefied. The soldering iron is used for heating the uninsulated wire. Then the wire is made to touch the solder until it melts and flows freely into the standard wirings. This process is called tinning.
  3. The wire is placed into the PCB hole. The ends of the wire are bent. It helps to avoid it from falling off while soldering. The heated wire should not touch any other component on the board.
  4. Soldering iron is applied to the solder and the tip of the wire simultaneously. It is applied for a few seconds until the solder, used for tinning, melts. The amount of solder should be sufficient to form a curve.
  5. After removing the soldering iron, the board should be kept static. Wait for the solder to harden.
  6. The excess wire is cut off. The soldered wire should firmly adhere to the board.

Reasons behind Poor Soldering:

Damaged PCBs are the result of poor soldering. One of the causes of poor soldering is the presence of contaminants. If the board and wire are unclean, oxidants may be present. The dirty surface makes the soldering difficult and time-consuming. It may also result in weak soldering.

Another crucial factor is heating. Insufficient or excessive heat also results in defective soldering. When soldering, too little heat might cause the joint to break. Too much heat can damage the other components present on the board.

The solder should fill the hole. An inadequate amount of solder can also result in the breaking of the joint with use. On the other hand, excessive solder makes it hard to identify soldering defects. It could bridge other metallic components on the board, resulting in a short circuit.

Tips for Good Soldering:

Cleaning the board and the wire is the key to good soldering. Tinning the solder is also crucial since it prevents oxidation of the tip. Tinning also helps in heat conductance. A sufficient amount of heat also results in good soldering. It is also necessary to ensure the usage of high-quality materials. Good soldering will result in a reliable product.


Soldering wire to the PCB when do telecom PCB assembly is a difficult task and requires expertise. Incorrect soldering techniques may lead to circuit breakdown and damaged boards.

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