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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. 

   File:SolderStation.JPG

Tip

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

 

Use the soldering iron to heat both the solder pad and the parts lead at the same time. Give it a couple seconds to heat up and then apply your solder, using just enough to cover the soldering pad and connect to the wire lead. Then let the connection cool. Be sure that the doesn't doesn't move during the cooling phase.
Ensure also that separate openings are not inadvertently patched.

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. 		This image is copyright © by Ian C. Purdie VK2TIP - correct soldering procedures to avoid dry joints

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