Lesser-Known Soldering Metals

Lesser-Known Soldering Metals

These are metals that may be rarely used in soldering (http://www.amazon.com/iCooker-Soldering-Iron-Watt-Solder/dp/B01774KARE) alloys or are widely used but the users rarely know about them. They include bismuth, antimony, indium and chromium.

Indium: Indium is among the most versatile metals on earth and is used in a very wide range of applications and industries. Indium is highly malleable and ductile. This allows molten indium-based solder to flow and fill joints easily, way better than other less-malleable metals. The metal also has very good electrical and thermal conductivity thus making it even more suitable for use in soldering tasks. Like antimony, indium improves the thermal fatigue resistance of other metals used in soldering. Indium-based alloys tend to have liquidus below 180 degrees Celsius making them perfect for use in procedures that make use of very low reflow temperatures. Unlike most other soldering metals, indium is very rare in the earth’s crust and this explains its limited use in soldering and other industries.

Bismuth: Bismuth has among the lowest melting points among all elements used in soldering making it ideal for use with small-scale soldering activities. However, most bismuth-based alloys expand on cooling and are therefore unsuitable for use in soldering due to lifting of soldered components. However, with the reduced use of technologies such as the through-hole technology, bismuth-based alloy solders have regained popularity. The main advantage is the low liquidus exhibited by the alloys. Bismuth in its pure form has a melting point of about 520 degrees Fahrenheit and a boiling point of 2847 degrees Fahrenheit. Similar to antimony and a few other metals, bismuth is denser in its liquid state than it is in its solid state.

Antimony: The element in its pure form has a melting point of about 630 degrees Celsius. Various characteristics of antimony have made the element suitable for use in soldering. The first characteristic is that of thermal fatigue resistance making the soldered joints more durable. However, antimony is not nearly as widely used as other metals in the manufacture of solder. There are also concerns about the toxicity of antimony.

Metals Used in Soldering: Lead

Metals Used in Soldering: Lead

Lead was until recently the most widely used metal in soldering. However, several risks and conditions arising from lead exposure have resulted in the reduced use and in some places total ban of the same. Lead is a naturally occurring metal with a relatively low melting point. This implies that lead-based solder is very easy to work with due to its low liquidus. The lead-tin alloy for example has liquidus of a relatively low 370 degrees Fahrenheit. This made lead suitable for what is known as soft soldering. Lead is often used with tin to improve the tensile strength, shear strength and wetting of the solder.

Lead use has recently been banned in very many countries around the world due to lead poisoning. This has varied effects often depending on the level of exposure and the time. The most common effects include reduced intelligence, poor cognitive skills in children, insomnia, migraines and insomnia amongst many more. Lead exposure comes from prolonged usage of household and other electronics with level of lead exceeding those stipulated by regulating authorities. The soldering process also leads to exposure through ingestion of lead oxide fumes. When a soldering iron heats solder, the lead present in the alloy turns to lead oxide, a poisonous gas that can cause rapid accumulation of lead in the body.

Often, the effects of lead ingestion are not reversible since the metal causes a permanent supply of free radicals within the body that in turn cause the health risks. Subsequently, the use of significant amounts of lead in consumer electronics has been banned and is often regulated by authorities throughout the world. However, despite its shortcomings, lead has been one of the easiest metals to solder with especially as an alloy of tin.

Soldering Metals – Images

Soldering Metals – Images

Natural Antimony

 Antimony

Natural Lead

Lead

Indium

Indium

Metals Used in Soldering: Indium

Metals Used in Soldering: Indium

Indium is among the most versatile metals on earth and is used in a very wide range of applications and industries. Indium is highly malleable and ductile. This allows molten indium-based solder to flow and fill joints easily, way better than other less-malleable metals. The metal also has very good electrical and thermal conductivity thus making it even more suitable for use in soldering tasks. Like antimony, indium improves the thermal fatigue resistance of other metals used in soldering. Indium-based alloys tend to have liquidus below 180 degrees Celsius making them perfect for use in procedures that make use of very low reflow temperatures.

Unlike most other soldering metals, indium is very rare in the earth’s crust and this explains its limited use in soldering and other industries. The metal is silvery white and has a characteristic luster not common in many metals. In its pure form, indium has a low melting point of about 318 degrees Fahrenheit. Indium-based solder has the advantage of having relatively low oxidization unlike other alloys. This implies that the solder can be effectively used even with the application of insufficient flux. However, the unavailability of indium implies that this advantage is rarely exploited.

Indium is also used as solder in its pure form to form stress-free points in terms of thermal and electrical conductivity. Indium-based alloy solders are as easy to use as any other types of solder and typically follow the generally-known soldering process of cleaning, fluxing, preheating, solder application, flow, cooling and post-soldering cleaning. It is thought that the use of indium will probably increase in soldering in the future. The rarity of the metal far outweighs its known benefits.