Melting lead emits fumes

Soldering in production

1. General
2 hazards
3 protective measures
4 More information


Soldering is particularly important in electrical engineering and is an essential working process for the production of electrical connections between components, cables and the construction of circuits. Practically every product with electrical or electronic components takes place in the manufacture. In principle, a distinction is made between manual iron soldering and large-scale machine soldering processes.

What is soldering? (Soft soldering < 450°="">

Soldering is a thermal process for joining materials (metals). Melting the solder creates liquid solder that creates the connection. In contrast to welding, the workpieces are not melted in depth.

When soldering, a flux is required as an additive in addition to the tin solder. Its purpose is to clean the surfaces of the workpieces when heated, to remove an oxide layer and to prevent oxidation during melting. This means that the above-mentioned soldering process can take place without interference and a mechanically stable and electrically conductive connection is created.

Where is soldering used in production?

In series production, large-scale machine soldering processes are primarily used, with machine soldering in systems. In the case of machine processes, the flux is either applied to the circuit boards before soldering or it is contained in the solder paste. The suction in the system collects and dissipates any soldering fumes and smoke that arise.
In addition, there are a large number of work steps in which manual iron soldering is required, e.g. B .:

  • the construction of devices and systems,
  • the production of small series,
  • the soldering of certain components or cables,
  • in the development.


Hazards during manual iron soldering

In contrast to machine soldering, manual iron soldering contains the flux inside the soldering wire like a thin channel.

The cause of the health hazard is the thermal processing of tin solder and flux at approx. 200 ° C. This creates soldering fumes / gases from the flux and its decomposition products, as well as smoke from ultra-fine dusts from solder and flux. The vapors, gases and smoke are released into the air and can enter the body through breathing.

Formaldehyde and acetaldehyde are predominantly used as soldering vapors / gases. As a result, with short-term exposure, among other things. Irritation of the eyes, the respiratory tract and irritation of the throat occur. Long-term exposure can lead to nausea and diarrhea. In addition, formaldehyde is classified as a carcinogenic and skin-sensitizing hazardous substance. Acetaldehyde is rated as a "presumably carcinogenic hazardous substance".

The soldering fumes contain ultra-fine dusts of the metals of the soldering tin and its oxides, which can lead to a health hazard if the occupational exposure limit is exceeded. Depending on the type of solder, it contains carcinogenic substances such as antimony, cobalt or nickel and / or the toxic heavy metal lead.

(Photo: DGUV Information 213-714)

Particular risk from leaded tin solder

With the Electrical and Electronic Equipment Act of May 24, 2015, lead was banned in the majority of products. This includes mass products such as B. Household appliances, IT and consumer electronics devices. There are exceptions, however. Due to the fact that lead-free tin solder sometimes causes major technical problems, lead-containing solder (with 37% lead) is legally permissible for certain applications. They relate in particular to certain components in an automobile, medical technology devices and photovoltaic systems as well as aviation, space travel, the entire military sector, and research and development.

In addition to the risk of inhaling the lead-containing soldering fumes, there are other hazards arising from the abrasion of the solder on the fingers. This can lead to absorption in the body through the mouth and digestive tract in the event of poor hygiene, in particular insufficient hand washing after work and before breaks.

3Protective measures

Extraction of soldering fumes and smoke

(Photos: Weller Tools GmbH)

The workplace limit values ​​for soldering fumes (formaldehyde and acetaldehyde) and soldering fumes must be observed. In the case of occasional soldering (max. ½ hour per day), based on previous measurements, it is not to be expected. In this case, the risk can be classified as low. Nevertheless, due to the proximity to the point of origin, suction is generally recommended. With permanent soldering, the occupational exposure limit values ​​can be exceeded. In this case, suction devices must be used.

Small table-top devices that look like a fan with a filter, so-called solder fume absorbers, do not adequately separate solder fumes and fumes. They are therefore not recommended by the employers' liability insurance association.

Prohibition for pregnant women

Due to the carcinogenic effect of formaldehyde, pregnant women are allowed to use manual iron soldering irrespective of compliance with the workplace limit value not used become.

Suitable work equipment and workflow

The following points must be observed when visiting the workplace:

  • If the occupational exposure limit values ​​for inhalable dusts or inhalable lead, nickel, cadmium, antimony and formaldehyde cannot be met, preventive occupational health care is mandatory
  • If the exhaustion does not guarantee complete collection of the substances, appropriate preventive measures must be offered.
  • When using lead-containing tin solder - even with low lead concentrations in the air - lead can be absorbed into the body through hand-mouth contact. It is therefore urgently advisable to monitor the blood lead level during preventive occupational health care (biomonitoring).

Further protective measures when using lead-containing tin solder

When using lead-containing tin solder, hygiene measures must be ensured, such as B.

  • regular intensive cleaning of the hands, in connection with a skin protection program,
  • Separation of work and private clothing,
  • possibly wearing thin cotton gloves,
  • Ban on eating, drinking and smoking in the workplace.

4additional Information

Soldering in the craft

Preventive occupational health care - suitability examinations - "G examinations"