Lead: Restriction of Hazardous Substances in Electronics

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Lead is a heavy metal used in the manufacturing of many electronic devices. Lead’s use is limited by the European Union’s RoHS directive due to its high toxicity.

Properties of Lead

Lead is a heavy metal used in electronics. Heavy metals are metals with relatively high density that are toxic at low concentrations, meaning even a small amount of the metal is toxic. Lead is denser (its particles are more closely packed) than most other materials.

Lead is naturally occurring and is usually found in combination with sulfur in the earth’s crust. The chemical symbol for lead is Pb.

lead - rohs
Pure oxidized lead and a lead cube
Source: Alchemist-HP Wikipedia

China, the top producer of lead from mines, produced 1.2 million tonnes of lead in 2019, making up almost half of the global total. Australia, Peru, and the U.S. are the other world leaders in production of lead. Each year, more lead is produced from recycled lead-containing materials, rather than from mines.

Characteristics that make lead popular in electronic manufacturing include its softness, its malleability, its ability to be combined with other metals, and the fact that it does not break easily.

Lead in Electronics

Lead is considered one of the most important metals in electronics production. It is most often used in electronics as a compound or alloy with another element.

soldering iron - lead restriction of hazardous substances rohs
Soldering iron

The main use of lead in electronics is lead soldering. The lead solder attaches two electronic components securely, allowing an electric signal to pass through. For example, lead solder could attach a wire to a circuit board. 

The most common type is tin-lead soldering, which is commonly used in devices where components that are sensitive to heat may crack or melt at high temperatures. When combined with tin, lead has a low melting point, which means it can be worked with at a lower temperature and is less sensitive to variations in temperature. 

Lead is also used in alloys (a mixture) with other metals, such as copper and steel, which expands the use of these metals. Lead alloy in steel is often used in electronic products.

Toxicity of Lead

It is unlikely that the average consumer will experience lead exposure as a result of touching lead solder, as lead solder is used internally in electronics. However, people may be exposed to lead from electronics if a device breaks. More common is lead exposure in workers who manufacture or recycle lead-containing products. Additionally, if lead-containing electronics are put in landfills, as the device breaks down, lead can leach out and contaminate water and soil.

There is no safe exposure level to lead. When lead is swallowed or breathed in, or enters the body another way, it gets stored in blood, which can cause long-term harm.

Lead exposure, particularly in children, can cause damage to the brain and nervous system, lowered IQ, slowed growth, and problems with hearing and speech. Long term exposure in adults can also cause fertility problems, heart disease, and kidney disease.

RoHS: Restriction of Hazardous Substances

RoHS stands for Restriction of Hazardous Substances. The RoHS directive, issued in the European Union, restricts the use of several hazardous materials in electronic and electrical equipment (EEE). All EEE products sold in the EU must comply with RoHS.

RoHS restricts the use of ten hazardous substances in electronics, including lead. Electronic devices may only contain these substances in amounts lower than 1000 ppm. The allowable amount for cadmium is 100 ppm.

The materials include:

Any manufacturer, importer, or distributor of electronic and electrical equipment (EEE) sold on the EU market must be compliant with RoHS. 

EEE regulated under RoHS includes a wide variety of electronic products separated into eleven categories, ranging from large household appliances to medical devices. The eleventh category is all-encompassing, as it includes any EEE not covered in the previous ten categories. 

Read more about how to ensure compliance with RoHS: What is ‘RoHS Compliant’?

RoHS Lead Exemptions

While alternatives to lead soldering exist and are in the process of being refined, exemptions do exist under RoHS for the use of lead in certain applications and electronic categories. These exemptions are given a date upon which they expire, and will no longer be exempt from RoHS unless an extension is granted.

Visit the European Chemicals Agency website for a full list of lead exemptions.

Alternatives to Lead Solder

RoHS works to reduce the risk of lead exposure by limiting the amount of lead used in electronic devices. 

As a result of RoHS legislation, many electronics manufacturers no longer use lead. RoHS pushes industry to innovate substitutions for restricted hazardous materials. Many manufacturers and scientists are researching and using alternatives to lead soldering, including solders containing tin and copper, silver, or other additives.

The most popular lead solder alternative is a solder combining tin, silver and copper known as SAC solder. While SAC solder is now widely used by many in the electronics industry, many changes had to be made in manufacturing processes before the solder could be used. SAC solder has a higher melting point than lead-tin solder, so many products had to be redesigned to withstand higher temperatures.

Another, more experimental alternative to lead solder is the use of ECAs, polymers (materials like silicone) that contain small flakes of conductive metal like silver. These materials stick to circuit boards and the metal works to conduct electricity. The advantage of ECAs is that they can be applied to circuit boards at a much lower temperature than other lead solder alternatives.

Lead-Limiting Legislation

RoHS is the main legislation that limits lead in electronics. However, other legislation has been passed that controls lead in electronic waste (e-waste). 

The United States Environmental Protection Agency (EPA) has several regulations that address the disposal and cleanup of e-waste that contains lead. For example, the EPA has rules for the disposal of cathode ray tubes (CRTs), which contain lead. Visit the EPA website for more information on e-waste regulations.

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