Objective:
- To troubleshoot the PCB traces
- To assembly the components
- To solders the component
- To master the soldering skill
Content:
It is important for the
designer troubleshoots the PCB traces before assembly and solders the
components. Two possible things might happen in the PCB traces: one is short
circuit and the other one is open circuit. Short circuit means two PCB traces
are touching to each other. This causes high current flows in the entire
circuit and burn out some of the low rating components. Open circuit means
there is no connection. When power is on, the PCB does not response. This might
be the problem of open circuit. Short circuit can be troubleshoot by using PCB
cutter to separate the two touching traces. Open circuit can be troubleshoot by
using jumper wire to make the connection between two traces.
After all tracks are
repaired, the component can be replace on PCB and start solder one by on using
soldering iron and lead. The figure on the bottom is the component that need to be use when soldering
Soldering Iron
Lead
Analysis:
There are a few things that needs to be considered while soldering, the important thing is of course the safety precautions. These are the list of safety precaution that must follow when soldering
First a few safety precautions:
- Never touch the element or tip of the soldering iron.
They are very hot (about 400°C) and will give you a nasty burn. - Take great care to avoid touching the mains flex with the tip of the iron.
The iron should have a heatproof flex for extra protection. An ordinary plastic flex will melt immediately if touched by a hot iron and there is a serious risk of burns and electric shock. - Always return the soldering iron to its stand when not in use.
Never put it down on your workbench, even for a moment! - Work in a well-ventilated area.
The smoke formed as you melt solder is mostly from the flux and quite irritating. Avoid breathing it by keeping you head to the side of, not above, your work. - Wash your hands after using solder.
Solder contains lead which is a poisonous metal.
Preparing the soldering iron:
- Place the soldering iron in its stand and plug in.
The iron will take a few minutes to reach its operating temperature of about 400°C. - Dampen the sponge in the stand.
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment, then squeeze to remove excess water. It should be damp, not dripping wet. - Wait a few minutes for the soldering iron to warm up.
You can check if it is ready by trying to melt a little solder on the tip. - Wipe the tip of the iron on the damp sponge.
This will clean the tip. - Melt a little solder on the tip of the iron.
This is called 'tinning' and it will help the heat to flow from the iron's tip to the joint. It only needs to be done when you plug in the iron, and occasionally while soldering if you need to wipe the tip clean on the sponge.
Ready to start soldering:
- Hold the soldering iron like a pen, near the base of the handle.
Imagine you are going to write your name! Remember to never touch the hot element or tip. - Touch the soldering iron onto the joint to be made.
Make sure it touches both the component lead and the track. Hold the tip there for a few seconds and... - Feed a little solder onto the joint.
It should flow smoothly onto the lead and track to form a volcano shape as shown in the diagram. Apply the solder to the joint, not the iron. - Remove the solder, then the iron, while keeping the joint still.
Allow the joint a few seconds to cool before you move the circuit board. - Inspect the joint closely.
It should look shiny and have a 'volcano' shape. If not, you will need to reheat it and feed in a little more solder. This time ensure that both the lead and track are heated fully before applying solder.
Conclusion
Now the circuit is complete and after wiring it, the circuit is ready to use. Now, all need to be done is the hardware part of the project. The hardware will be prepared on the next week.
