Solder is a metallic alloy used when melted to join two metallic surfaces into one. Joining metal parts together by allowing a molten metal alloy to flow around them is called soldering. When the solder cools and solidifies, it provides an excellent electrical connection between the parts along with a bit of mechanical strength. It is a skill that both professionals and hobbyists should hone and is essential in repairing, building, and modifying electronic components. The most frequent use of soldering is in attaching electronic components to printed circuit boards (PCB). I wrote this guide to help beginners and novices with the basics of soldering electronic components together. While the basics of soldering are seemingly straightforward and simple, only the correct tools, technique, and practice will produce the “perfect” joints.
Before you get started, you must first realize that the rosin in the solder is harmful to your body. Therefore, you must always work in a well-ventilated area. Next, be sure to protect your eyes. Safety glasses are a cheap investment for a lifetime of vision. Finally, static electricity can cause problems, especially to integrated circuits and other semiconductor devices. It is a good idea to work in an antistatic area with an antistatic soldering iron. Antistatic mats are available to overcome this.
How to Solder
Equipment: Basic Tools
The one instrument that you will always need is a soldering iron. A soldering iron between 15W and 30W is recommended. The use of a soldering iron with higher wattage can cause unnecessary damage to electronic components and is generally not used in essential soldering work. You will also need some solder. A rosin core solder, preferably with a small diameter, is recommended. The solder will be composed of 60% lead – 40% tin and cores of rosin “flux,” which improves the molten solder to flow more quickly over the joint. A thin solder with a small diameter makes tinning the exact amount of solder. It is always good to have a small wet sponge to clean and cool the soldering iron tip. Most soldering iron holders come with a sponge attached to their base. Refer to the soldering iron category for detailed information regarding tools.
Surface Preparation: Cleaning
Before you can start soldering, you must ensure that all parts to be soldered are free from grease, oxidation, and other contamination, lest you form globules of molten soldering flowing around where you don’t want them to. An unclean surface can also cause the solder to not bind well to the surface, and beginners can make the error of overheating the components as they try to force the solder to stick. The overheating will usually result in irreversible damage and force you to replace the parts. It is essential to understand how to prepare the components to be soldered properly.
Component Preparation: Tinning
It would be best if you tinned both contacts before you attempt to solder them. This coats or fills the wires or connector contacts with solder so that you can melt them together. For example, if you are soldering a piece of insulated wire, use a wire stripper to peel away the insulation tip to expose the copper wire within, and then gently coat it with solder. It would be best if you likewise tinned the iron tip to improve conduct heat to the components.
Applying Heat and Solder
With the tinned soldering iron in hand, you are now set to heat the parts. Rest the iron tip on both the component lead and the PCB. It will only take one or two seconds to warm the components. Once you have heated the part and the circuit board, you can connect the solder. Touch the tip of the strand of solder to the heated element lead and the solder pad on the circuit board, but not to the iron tip. At this point, the solder will float freely around the component lead and the pad. Once the pad’s surface has been fully coated, you must stop adding solder and quickly remove the soldering iron. Do not remove the newly formed joint for a few seconds till the solder cools down and becomes solid. Moving the joint at this point will create a formation of a cold joint.
Cleaning & Finishing up
It would be best if you wiped the tip after each solder. There are solutions specifically designed for this, but a damp sponge works just as well. The idea is to rub the soldering iron tip every time you finish a solder joint. That is to say, you will be cleaning the tip several times per session if your project requires you to form multiple solder joints. To wipe the solder off a circuit board, you should use a solder wick. First, place the wick on the joint or track you want to clean up, and apply your soldering iron on top. The solder will melt and be drawn into the wick. The wick will fill up, so kindly pull the wick over the joint and your iron, and the solder will move into it as it relinquishes.