The soldering iron tip is the part of the iron that is used to transfer heat from the element to the work pieces that are being soldered. The size, composition and configuration of the tip being chosen should be determined by the requirements of the intended application and by the work environment that it will be used in. There could even be rare instances where a custom tip may be desired.
Choosing the correct tip will greatly increase your chances of creating a quality solder joint. It is very important for you to match both the tip and the iron to the soldering application that it will be used on. It is always a good idea to make sure in advance that the desired tips size and configuration are readily available for the type of irons that you have chosen to use. Always remember that a good quality solder joint is rarely achieved by using improper, or inappropriate tools, materials, or equipment.
Most tips are made of copper, which is suitable because of its excellent thermal conductivity and high heat content per volume. Some tips are plain copper, while others incorporate various additives or have a protective plating applied. One of the most common problems associated with plain copper tips, is that tin-lead alloys (more specifically the tin in the alloy) will attack the copper, dissolving it away. This makes it necessary to continually file the tips to maintain the required shape, giving these tips a shortened working life. Another concern is the amount of impurity that is imparted to the solder joint when using bare copper tips. Adding tellurium to the copper improves both wear and oxidation resistance, but does not protect the tip from rapid deterioration. It has been determined that both iron and nickel, despite their low conductivity, are wettable, offer a high level of resistance to erosion and their heat per volume is close to that of copper. Because of these facts we are able to maintain good conductivity, while increasing the erosion resistance by plating copper tips with either nickel or iron. These plated tips are generally referred to as nickel-clad, or iron-clad and make up a large majority of the tips in use for modern soldering applications.
The tip type is determined by the soldering iron it is used on. There are screw type tips (tips that screw onto, or into the solder iron element), slip on tips that slip over the element and plug type tips that slide inside of the element. There are even tips that are a permanent part of a replaceable element/tip assembly. Regardless of the type of tips required it is always important to have them fully seated to the element and periodically cleaned, in order to maintain proper heat transfer from the element into the tip.
The tip configuration to use should be determined by the intended application requirements. Some of the basic tip configurations available include ballpoint, conical, diamond (pyramid), chisel, and spade. You will find that there are usually a variety of styles, or modifications available, within each of these basic configuration families, to accommodate specific application requirements. Although less efficient, a more narrow configuration is sometimes required to obtain accessibility, or to achieve the desired results.
The tip size to use (regarding the working portion) should also be determined by the intended application requirements. The tip body, or shank must be matched to the iron it will be used with (always select a tip that was designed, or approved for the soldering iron you intend to use on the application being considered). As with tip configuration though, there are usually a variety of modified working diameters available within each family of standard tip sizes that are available. These modified tips are generally referred to as turned down tips, because the working area of the tip has been turned down to a smaller diameter than the body, or shank diameter. Turned down tips are not as efficient, but are sometimes required to solder in otherwise inaccessible areas.
An important consideration, when choosing the most appropriate tip, is that thick, short tips will store more heat and deliver it more efficiently than long, narrow ones. This makes the standard chisel, or diamond (pyramid) configuration the usual tip of choice. The chisel shaped tip is often used for connecting components to through-hole PCBs and for joining flat seems together. The working edge of the chisel tip should be about the same width as (or slightly wider than) the connection that is being made, or the seam that is being soldered. The diamond (pyramid) shaped tip is commonly used for assembling corner seams in order to heat both of the 90° surfaces simultaneously. The working area of the diamond (pyramid) tip should be determined by the material mass being soldered, the overlap of the seam (if any) and the tips accessibility to the intended solder joint area. Usually a solder connection (unless soldering large, or heavy gauge parts) is made in 1 to 3 seconds. If the connection takes longer than 3 seconds, you may need a larger tip, a higher wattage iron or a completely different type of soldering equipment altogether. It is a good idea to familiarize yourself with other soldering methods and equipment that are available in order to ensure that you are utilizing the best, safest, most efficient and economical means available to perform your soldering application.