A Beginner's Guide to Soldering

A Beginner's Guide to Soldering

Solder (pronounced "sahd er") is a metal or metallic alloy that when heated to its melting point, can bind together two metal surfaces. A common soldering material is a tin-lead combination, but there are others, each with their own melting point and best uses. Solder is thin, silver-colored wire of varying thicknesses, most often sold in rolls. The act of soldering joins two or more metal surfaces together, creating a mechanical or electrical connection between them. Some common soldering work entails adjoining electrical components onto circuit boards, or connecting wires for various needs. When soldering, the metal parts that are to be bonded are heated quickly, then flux and solder are added to the surfaces. When the molten solder cools, it hardens and creates a nearly unbreakable bond that will conduct electricity.

The basic tools for a soldering job are a soldering iron and solder. There are many different soldering iron types that are used with any number of different sized tips; the particular job will dictate whether a larger or smaller tip is most appropriate; consider some additional pieces for your soldering tool kit. For circuit board work, which is a common soldering job, a fine tip, thin-wire solder, and a fairly low temperature is required. Other jobs, like those with audio cables, may necessitate a larger tip, thicker solder, and a relatively higher temperature. Also helpful for a tool kit are holders and clamps to maintain adhesion during the solder's cooling process. A damp sponge and a steel wool pad will help in keeping the tip of the soldering iron clean, which is an absolute "must". When using a damp sponge, use it quickly so the tip temperature is not reduced. Steel wool will free the tip of hardened particles without the addition of moisture. A small pair of wire cutters, and pliers (needle-nosed) will come in handy.


Be careful when soldering and pay attention! It's easy to pick up the soldering iron from the wrong end - the heated tip. For many common hand-held jobs, the tip temperature can be about 400 degrees (F). Consequently, when the heated tip and solder touch, the solder liquefies immediately - and also becomes extremely hot. Most solder melts at about 370 degrees (F). Molten solder sticks to carpets, furniture, pet fur, and skin where it will burn and instantly create a painful blister. So, take great care to prevent splatters. If a solder burn occurs, however, or solder is ingested, seek medical treatment immediately. Eye protection, made especially to guard against chemical splashes, should be worn while the job is in progress should splattering occur, and also to guard the delicate eye tissue from potential fumes. Remember -- Solder is poison! It should be handled accordingly. Do not attempt to eat, drink, or smoke while soldering. A soldering iron, when not in use, should not be put down or onto anything other than its own stand. It is crucial to operate safely when soldering.

Silver-content solders have a smooth flow and create a bond stronger than some other solders. But they melt at comparatively higher temperatures and are more difficult to remove when de-soldering, which we will discuss shortly. More common solders contain lead, but lead-free types are available, fairly popular, and encouraged for health and safety.

When the heated tip of a soldering iron meets the soldering wire, the melting process can produce small amounts of smoke, mostly from the flux. For some, especially asthma sufferers, this can become irritating. It is very important that the work area be well-ventilated and keep to the side of the work, rather than immediately over it, to avoid breathing the fumes. This means more than simply opening a window. If an exhaust fan is available, DO use it. However, place it several feet away. Too much cool air flow in too close proximity can affect the bonding and wetting of the surfaces by causing temperatures to be reduced. Hands should be washed thoroughly after soldering.

Soldering Basics and How-to's:

While in its holder or stand, plug in the soldering iron and allow it to heat to the required temperature. Dampen a sponge with cold tap water; squeeze out all excess. Test temperature readiness ready by seeing if the tip will melt the solder. Wipe the tip of the iron on the damp sponge. Melt a little solder onto the tip of the iron (tinning); this allows heat to flow from the iron's tip to the actual bonding area and removed any oxides from the iron's tip. Do this while the iron is warming up, and from time to time during the soldering job. Use the sponge to wipe the tip clean.

During the soldering process, the metal tip transfers heat from the soldering iron to the location of the desired connection. Because of the heat conducting ability of copper, this is what most tips are made of. Conductivity governs how quickly heat will reach the intended connection area. Length of the tip affects heat flow; the tip's shape determines how well heat reaches the intended connection, greatly affecting outcome. The tip as a whole and the performance of the heater will greatly affect the entire soldering system.

When molten solder and a copper surface make contact, the solder dissolves and penetrates the copper surface and new alloy forms, which is a blend of the copper and solder. This solvent action is what is referred to as wetting and forms the bond between the surfaces. Wetting can only occur if the surface of the copper is free of contamination and from the oxide film that forms when the metal is exposed to air. The solder and work surface must reach the correct temperature.

Although the surfaces to be soldered may appear to be clean, a thin oxide film is almost always covering it. For a solid bond, it is crucial that all surface oxides be removed during the soldering process; this is done by using flux.

When preparing to use soldering for surface-mounting components onto a circuit board, there are some things to be mindful of. Flux will remove oxides from the soldering surfaces but does not remove dirt, oils, soot, or other debris or particles. The circuit board has some lead components which, in addition to the board's condition, will greatly affect the solder flow and proper adhesion when the desired outcome is a reliable electrical connection.

If the surface is contaminated, solder will not flow or adhere to the surface material. Component leads are usually protected by a surface finish, which may be plated in tin or even a solder - dipped coating. Plating, however, doesn't protect as well as a solder coating because the plated finish is porous.

If the bond was unsuccessful, it could be due to one or a combination of several reasons. For one, the temperature may be too high, or the coating created by tinning was burnt off quickly and oxide contaminants settled on the tip of the soldering iron. Oxidation occurs when cleaning of the soldering iron is done poorly or improperly, or something other than a damp sponge or steel wool is used. Other reasons why the bond was unsuccessful can include a poor solder or one with interruptions in the flux core. Additionally, there may not have been adequate tinning with higher temperatures; poor timing; or a flux that does not remove all oxides from the soldering tip. For cleaning up after the soldering is complete, wet-mop all areas and surfaces.


This is done when a connection has been soldered into place and must be removed or replaced. For instance, a joint created between two surfaces may be faulty, which is called a "dry" joint; or the actual soldering job was poorly done. In another example, components of a circuit board no longer work, or need to be upgraded. Proper tools are required for de-soldering.

Soldering Professions

Certification is required before soldering work may be performed commercially. Depending on the educational facility, certification programs can vary in requirements and duration for potential students. Anyone can learn to solder for personal hobbies; it simply takes practice.

Most often, soldering certification leads to careers in electrical installation and repair, with some of these field technician positions earning more than $30 an hour. The automobile industry widely uses soldering skills in the development of auto parts; an automobile repair technician must be highly skilled with soldering, and the skill is widely used in the construction of vehicle models. Jewelry making requires the quickly bonding of metals without leaving behind any visible trace of seams or other indications. Creating works in stained glass requires soldering skill, as does plumbing work and even orthodontics.