What is soldering
Soldering is a skill that gets better as you practice more! Soldering is the process of joining two metals together with iron by the use of a solder alloy to form a reliable electrical path. It is not a simple task since it requires experience and knowledge. It is very important to make a proper soldering joint since faulty joints are one of the major causes of circuit boards failure. For beginner a soldering process looks simple. It looks that the solder simply sticks to the metal like some kind of conductive glue. However, what happens during this process is far different. When hot solder comes into contact with surface of copper on circuit board, a metal solvent action takes place. The solder dissolves and penetrates the surface of copper. Copper and solder blend together and form new metal alloy that one part is copper and the other part is solder. Solder is already metal alloy of tin and lead. This process can occur only if the solder and surface of the copper are hot enough..
Getting started with soldering
Use an appropriate soldering iron with heat control. An Electrostatic Discharge (ESD) safe, temperature-controlled is a good soldering iron and will allow you to solder for hours.
For small projects use a 25-watt fixed power soldering iron and 100-watt for larger projects.
Solder wire
Solder is a metal alloy material (60% tin and 40% lead) that melts and creates a bond between electrical parts.
Lead-based is a type of traditional solder wire with 60/40 (tin/lead) mixture, the most common solder alloy used in electronics and available in the market. Its melting point is around 180-190 degrees Celsius. With higher tin concentration, it will have better tensile and shear strengths. You can also find non-corrosive solder wire having 63% tin and 37% lead mixture with good solderability and insulation resistance.
Component placement
Always start with the smallest component first. For example resistors; place them correctly on the PCB board by checking their value (color code).
Pay attention to the component orientation and polarity. For example Diodes, Electrolytic Capacitors have polarity and should solder in the correct position.
Start soldering
Before starting soldering, always double check and make sure all the components are placed correctly.
First you will need to have a clean and safe workstation to work. Be careful working with soldering iron you don’t want to burn anything.
Power on the soldering iron and wait a few minutes to reaches the appropriate temperature.
Once the soldering iron is hot, clean the tip either with sponge or wire cleaner.
Sponge:
Get sponge wet and rub the tip on both sides to remove any solder and or dirt
Wire Cleaner:
Stick the soldering tip in the cleaning wire a few times until clean.
Never scrape the tip with sand paper, knife, Etc. This will take the outer layer of the tip off causing dirt to build up and cause performance issues.
When ever possible make a good mechanical connection before soldering. This will make a stronger connection.
Tin the tip, do this by applying a small amount of solder on the tip of the soldering iron before trying to solder anything. Once you have tinned the tip you will want to make your solder connection as quick as possible. Tinning the tip will increase the surface space and the connectivity allowing more heat to be transferred to the metal you trying to solder. You want to clean and re-tin your tip after a few solder connections. You never want to leave your tip untinned. This will cause performance issues and oxidation on the tip. Using a soldering iron without tinning the tip will ruin the tip.
After you have tinned the tip you want to touch the tip to the metal you trying to solder. As the tip is on the metal you want to slowly add some solder until you see the solder run to the metal. Once you see the solder moving on the metal you can add the solder a little faster until you have a good amount of solder and the connection is made.
Once you have made the solder connection you want to remove the soldering iron. Do not move your connection until to solder has hardened. If you move your connection right away you connection will either fall apart or you will cause a cold solder joint. A cold solder joint is a bad connection and you will want to resolder it.
Example of a good soldering
Cold solder joints
