Types of Soldering Iron

The soldering iron is a device for connecting components by hand by soldering. While soldering with a soldering iron, metal parts and another, low-melting metal (the solder, e.g. solder) are heated and the metal parts brought together are wetted by the solder and are then electrically and, after cooling, mechanically connected to each other. For hand soldering, a flux is required as an auxiliary substance.

Soldering irons are only used for soft soldering. Brazing is not possible with copper tips. For this, but also for soft soldering, gas flames or lasers are also used.

The origin of soldering can be traced back to ancient times, with evidence of its use dating as far back as 5000 years ago. Early civilizations such as the Mesopotamians and Egyptians employed soldering techniques to join metals together for various purposes, including jewelry making and plumbing.

However, it wasn’t until the 19th century that soldering truly came into its own with the advent of the modern soldering iron. These early iterations were often crude and inefficient, consisting of little more than a heated metal tip attached to a handle. Over time, advancements in metallurgy and engineering led to the development of more sophisticated soldering irons capable of precise temperature control and enhanced performance.

Functionality and Design of Soldering Iron

At its core, a soldering iron is a simple device designed to generate heat at the tip, allowing solder – a low-melting-point alloy – to melt and form a bond between two metal surfaces. The basic components of a soldering iron include the heating element, usually made of copper or ceramic, the tip where heat is concentrated, and a handle for easy maneuverability.

Modern soldering irons come in a variety of designs and configurations to suit different applications. Some feature adjustable temperature controls, allowing users to fine-tune the heat output for optimal soldering performance. Others incorporate ergonomic handles and lightweight construction for extended use without fatigue. Additionally, specialized soldering irons with interchangeable tips enable users to tackle a wide range of soldering tasks with precision and efficiency.

Types of Soldering Iron

Fire-heated soldering iron

Early soldering irons often have a hammer shape and consist of a 250 to 1500 g copper block with an iron handle (poorer heat conduction) and a wooden handle. The copper block usually has a cutting edge or fin, which allows the finer application of heat and solder. For even finer work, pointed pistons were used (in the illustration: 3rd from above). The flask is heated with the blowtorch, whereby the copper blackens and then becomes bright again in the flame. The copper block has enough heat capacity to process even larger solder joints.

Coal basins were also used in the construction of telecommunications lines. They were about the size of a shoebox and were fired with grease or charcoal. Thermally insulated handles (mostly wood) allowed transport in the company. Such braziers were generally used for soldering work before the invention of the blowtorch. There was a great risk of fire, especially during roof work, if it was handled carelessly, this could lead to ignition of the roof truss. These old soldering irons, like other large soldering irons, were regularly cleaned during operation by rubbing them on an ammonia stone.

Soldering water (zinc chloride solution with excess hydrochloric acid) was common for cleaning the solder joint.
Rosin (solid resin) and solder grease served as fluxes. In the field of water installations, stearin was also used for soldering lead pipes, usually in the form of a candle.

When the tin no longer flows, it must be reheated. Later, gas-heated soldering irons were developed, in which a gas flame continuously heats the copper block.

Pencil Soldering Irons

Pencil soldering irons are the workhorses of the soldering world, featuring a slim, pencil-like design with a pointed tip. These irons are lightweight, portable, and easy to maneuver, making them ideal for intricate soldering tasks such as soldering small components and surface-mount devices (SMDs). Pencil irons are available in both corded and cordless versions, offering flexibility and convenience for soldering on the go.

Temperature-Controlled Soldering Stations

Temperature-controlled soldering stations are the preferred choice for professional electronics technicians and hobbyists alike. These versatile tools allow users to precisely regulate the temperature of the soldering iron tip, ensuring optimal heat transfer and soldering performance. Temperature-controlled stations typically feature adjustable temperature settings, digital displays, and ergonomic handles for enhanced comfort and usability. They are suitable for a wide range of soldering applications, from basic through-hole soldering to advanced surface-mount assembly.

Butane-Powered Soldering Irons

Butane-powered soldering irons offer the ultimate in portability and convenience, making them ideal for use in remote locations or on-the-go repairs. These irons are fueled by butane gas, eliminating the need for cumbersome power cords or electrical outlets. Butane irons heat up quickly and are capable of reaching high temperatures, making them suitable for soldering in challenging environments where electricity may not be readily available. They are popular among field technicians, outdoor enthusiasts, and DIYers who require a reliable and portable soldering solution.

Soldering Gun

Another type of electric soldering device is the soldering gun, named after its typical shape (see picture). Its heating coil, shortened to a loop, is itself used as a soldering tip. In contrast to the electric soldering iron, the soldering tip itself is flowed through by electricity. Due to the soldering tip shape (a rather short, thick conductor), a high current at low voltage is required. This requires thick supply lines. In order to keep this short, the transformer required for transforming and galvanic isolation from the light network is integrated into the device. Due to the gun shape, the soldering device remains manageable despite its comparatively high weight and volume.

Soldering guns have a relatively short warm-up time of only a few seconds compared to soldering irons. They are therefore switched on by a button located in the handle only for the soldering process. The devices are not suitable for continuous operation. Soldering work is only possible to a limited extent with soldering guns, because on the one hand the tip cannot be very pointed due to the principle and on the other hand there is no large heat output or heat capacity available for coarser work.

Specialty Soldering Irons

In addition to the standard types mentioned above, there are also specialty soldering irons designed for specific applications and industries. For example, desoldering irons are equipped with a built-in vacuum pump to remove solder from circuit boards, while soldering tweezers feature fine tips for precise soldering of small components. Hot air rework stations combine soldering and hot air functions for advanced surface-mount rework and repair.

Soldering Tip

Soldering tips are made of copper. However, this alloys with tin, i.e. the soldering tip dissolves in the tin, it becomes scarred and must be filed. Lead-free solder dissolves copper tips faster than leaded solder.

A so-called permanent soldering tip consists of a copper core for heat conduction and is electroplated with an iron layer. Iron is used because it is wettable with tin, but very slowly deposited in liquid tin. This means that the service life of the tip is longer. The tip is pre-tin-plated. The non-wettable part is protected against corrosion with a chrome or nickel/chromium layer. If the tip becomes unwettable, an ammonia stone will help at the highest soldering iron temperature. A permanent soldering tip must not be mechanically treated (ground down). This destroys the iron layer and makes the soldering tip unusable.

The type of cleaning depends on the intended use. Soldering tips for electronic components are usually cleaned with a damp sponge. Acidic or other chemically aggressive cleaning agents are not used for such soldering tips.

Oxidation of the shaft of copper soldering tips in the heating cartridge may prevent them from being pulled out. The remedy is regular brushing clean and wrapping with some household aluminum foil.

Soldering tips are available in different shapes. For example, round, cone-shaped and flat tips are common.