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April 30, 2018

Soldering Technique

OVERVIEW

Soldering is used today to make electrical connections. Modern electronic systems are formed from thousands of components connected by soldering. If any connection fails, the system could stop working, resulting in loss of time, money, or even lives. Therefore, good soldering technique is important to ensure reliable electrical connections.

Solder melts at high temperature and lows to cover the surface of the connections. When it cools, the solder solidifies and a good electrical connection is formed. For solder to flow easily, the metal surface must be free of grease, dirt, or paint, very much like how water wets a non-waxed surface.

Besides a dirty surface, another barrier to wetting is the oxide layer that forms when metal is exposed to air. In fact, as you solder, oxidation is accelerated due to the heat. A substance called flux can be used to remove the oxide layer. Flux can be applied manually or in some cases, it is embedded in the solder.

 

 

PART 1: PREPARING THE SOLDERING IRON

  1. Switch on the soldering iron and place it in its stand. Wait a few minutes for the soldering iron to reach its working temperature.
  2. Dampen the sponge in the stand.
  3. Melt some solder on the top of the soldering iron, and then wipe the tip with the sponge to clean off any excess solder. This step is called tinning, which helps to clean the tip and speed up the heat flow later.

 

NOTE: Here are some safety precautions:

  • The tip of the soldering iron can get very hot. Be careful not to touch it.
  • Work in a well-ventilated area or wear a face mask when soldering because the fumes of the solder flux can damage your lungs.
  • The solder may contain lead, which is poisonous. Wash your hands thoroughly after handling it.

 

PART 2: PREPARING THE CIRCUIT BOARD

 

 

PART 3: SOLDERING THE COMPONENTS

STEP 1: Mount the component on the circuit board.

 

 

STEP 2: Bend the leads to hold the component.

 

STEP 3: Solder the leads to the copper track.

 

 

STEP 4: Cut off the leads.

 

 

PART 4: IDENTIFYING GOOD SOLDERING JOINTS

A good soldering joint is shiny and has a volcano shape.

Image courtesy of Adafruit

Some components, like transistors, are sensitive to heat. During soldering, use a crocodile clip as a heat-sink to channel way heat from the component.

 

PART 5: SOLDER THE CIRCUIT

For this example, we will use the circuit from Non-Contact Voltage Detector. Now that the breadboard circuit is proven to work, we will now solder the components on the circuit board. Start by cutting the board to the required size (12 holes × 9 holes) as shown below.

Before soldering, plan your component layout on the circuit board. It is better to spend time planning to get the connections right. If not, you have to spend a considerable amount of time to re-solder the components.

 

 

 

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