Essential considerations for managing soldering fume extraction
Electronics production is heavily concerned with soldering components on to printed circuit boards (PCBs). A small part of the operation is automated, using wave soldering machines, with the majority being manual as operators add individual components using hand soldering irons. Further hand soldering and desoldering is frequently used in rework stations to carry out repairs and upgrades.
All of this soldering activity generates fumes which can cause long term, serious harm to operators if inhaled. Employers may face expensive compensation claims as a result. Most countries recognise this and enforce legislation to ensure that employers protect their employees from these harmful effects. Even in regions without such legislation employers have an ethical duty to provide such protection. In this article we look at the nature of the risk, the relevant legislation, and how fume extraction can be managed safely, effectively, energy-efficiently and in compliance with regulatory demands.
Why soldering fumes are a risk to workers
Soldering and rework, like other activities involving adhesives, welding and laser applications, create particles and gases which can be harmful to workers. It was widely believed that the move to lead-free soldering would create more environmentally-friendly conditions; however because of the higher temperatures required and extra flux used lead-free soldering smoke emissions actually contain more fine dust particles which are easier to breathe in. As Fig.1 shows, these penetrate further into the lungs than pollen or asbestos, reaching and blocking the alveoli.
Much of the problem is actually caused by the flux that solder needs to operate effectively. Flux cleans the surfaces to be joined, increases the flow of solder to make a good connection and prevents oxidation which could affect the strength and quality of the joint. Fluxes are typically based on rosin, a naturally occurring solid, resinous material obtained from pine trees. Solder wire used for hand soldering typically contains a central rosin flux core which is released on heating. For electronics assembly lines, the flux may be within a solder paste applied by syringe, or by stencil and screen printing. It may also be sprayed as a liquid or foam before wave soldering.
During hand soldering, fume without effective control will rise vertically, probably entering the breathing zone of the solderer. Fume may drift and accumulate in the workroom, especially if the soldering work is widespread and intense, and general background ventilation is poor. Other people in the area who are not soldering can therefore be put at risk, as can staff maintaining and cleaning soldering plant, equipment and control systems.
Solder fume, comprises 99.5% particles and 0.5% gases. It is one of the top causes of occupational asthma in the workplace because, when breathed in, it can trigger an irreversible allergenic reaction in the respiratory system. Once this sensitisation reaction has taken place, further exposure to the substance, even the tiniest trace, will produce symptoms. These can become increasingly severe, with continued exposure possibly causing permanent lung damage. Sufferers are often unable to return to soldering work ever again.
Other medical conditions can also occur; these include skin and eye irritation, allergenic conditions, bronchitis, sionasal cancer and carcinogenic heart/lung diseases. The precise constituents of the fume causing occupational asthma and irritation are not known. From a review of scientific evidence it has not been possible to identify a safe level of exposure below which occupational asthma will not occur. Exposure to all rosin-based solder flux fumes should, therefore, be avoided or kept as low as is reasonably practicable.
Managing Solder Fume Extraction. Date published: 24th July 2015 by Farnell