All About Soldering



Soldering is the process of molding metal objects together without completely melting them. Soldering can be used in a wide variety of circumstances, including plumbing, electrical work, and jewelry making. This is usually done with a soldering iron.

There are generally two types of soldering irons – butane powered and electric corded. The butane powered soldering iron is convenient because of the fact that it is cordless, making it very convenient to carry around and work with. It also has a broad range of heat, and is easy to refuel. According to the website

The electric soldering iron can hold a constant heat level, thus you won’t burn up the area you are soldering. It also has many tips for different projects, giving you a very accurate soldered joint.

When soldering, there are proper precautions and procedures that must be taken before, during, and after the task to ensure the best job possible. Cleaning the tip of the solder iron is very important. It should always be bright silver. In order to remove any residue or oxide from the iron, simply wipe the tip with a damp sponge. The tip of a soldering iron should always be properly tinned. A thin, steady layer of solder should cover the entire surface of the iron. If this is not the case, then it has not been properly tinned.

A clean board is also very crucial in soldering. A board should always be protectively stored, where it does not come in contact with oxides, or any other kinds of contaminants. Wire terminals may have to be cleaned to remove any oxides before a wire is installed. “Dirt films on metals may consist not only of oxides, but sulfides, carbonates, and other corrosive materials from the environment. These will hinder solder flow or wetting of the solder onto the surfaces being soldered.”*

It is very important to test component leads in order to make sure they are suitable for soldering. If a problem should arise, the lead should be re-tinned and then cleaned off. This should be done to ensure that no further problems occur once the components are installed onto the board. It is important to also have wire clean as well – it should have the burned flux residue removed. This can be done with a liquid cleanser.

Another imperative item is the flux. The main purpose of flux is simple: “it prevents oxidation and removes the thin layer of oxide and the atmosphere gas layer from the area to be soldered.”* When the flux is used, it allows the solder to flow, or wet, easily and evenly over the surface of the lead, wire, or whatever is being soldered. It also expands the flow of heat, which makes the items that are being soldered heat faster.

There are several different kinds of fluxes. The acceptable types of rosin flux include the pure rosin and the mildly activated rosin (R or RMA). “This later flux is in common use today, with some inroads being made by so-called low residue and no clean fluxes.”* There are times when the residues that are left behind from flux can become water absorbent. This should be removed no later than thirty minutes after the connection has been made. RA flux can be used in tinning bus wire or component leads, but it should not used on a circuit board. It also should definitely not even be kept in the same room, because of the chance of it getting picked up and used. If this happens, activators will damage the board and cause many problems.

If the proper flux is being used, it will be extremely helpful and contribute in all aspects of soldering and desoldering. It advances the “intermetallic bonding”, as well as the solder flow. When a flux is poorly wet, it’s usually because it was not cleaned properly, or it lacks sufficient heat.  The technique used in solder is actually more important than the amount of solder. In many cases, only a small amount of solder is needed. “A second method of soldering is referred to as reflow soldering. This is normally used where through holes are not involved such as installation of surface mount items or repairing circuit board traces. The technique is relatively simple.”*

There are several examples of “unreliable connections” that should be kept in mind:

  • Overheated
  • Cold
  • Fractured
  • Non-wetting
  • Excessive solder
  • Insufficient solder
  • De-wetting

Some other defects that one should keep an eye out for:

  • Damaged wire insulation
  • Lumps or large holes
  • Pinholes or voids

A good solder connection should display some of the following characteristics:

  • Smoothness
  • Brightness
  • Shininess
  • Cleanliness

*Quotations and additional information courtesy of and

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