Soldering and LEDs
Purpose and Operation
A soldering iron is a hand tool most commonly used in joining two conductors. It supplies heat to melt the solder so that it can flow into the joint between two workpieces.
It is composed of a heated metal tip and an insulated handle. Heating is achieved electrically, by passing an electric current (supplied through an electrical cord or battery cables) through the resistive material of a heating element.
Stand
A soldering iron stand keeps the iron away from flammable materials, and often also comes with a cellulose sponge and flux pot for cleaning the tip. Some soldering irons for continuous and professional use come as part of a soldering station, which allows the exact temperature of the tip to be adjusted, kept constant, and sometimes displayed. |
Most soldering irons have interchangeable tips, also known as bits, that vary in size and shape for different types of work.
Cleaning
When oxidized material begin to accumulate on the tip, they can block heat transfer and contaminate joints, making soldering difficult or impossible. This can be alleviated by running a wet sponge across the tip.
Soldering Technique
Examples of proper and
improper soldering are shown on the right In the first example, the component lead was heated while the PCB wasn't heated. As a consequence the solder only flowed onto the component lead. |
In the second example the PCB was correctly heated while little or inadequate heat was applied to the component lead. This is the most treachorous example because in practice it is not always particularly obvious. Often this type of dry joint "just" allows the solder to "touch" the component lead while not actually being "soldered" to the lead. It it might work for a period of time depending upon environmental conditions of heat and cold.
Example 3 depicts solder bridging both the PCB and the component lead. In this case the PCB and the component lead were both heated "simultaneously" AND the solder was applied to either the component lead or the PCB to "flow" freely from one to the other to provide a good electrical joint. Such a joint is always bright and shiny.
LEDs
Short leg is negative