• • • SAFETY IN ENGINEERING • • •
Enabling a safer, more productive working environment through atmosphere management
Josh Evans MEng (Hons) IChemE, applications engineer and head of BOFA Academy at BOFA International, says the value of effective fume and dust extraction can sometimes be overlooked in a busy manufacturing environment
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ot only does filtering workplace emissions make sense from an occupational health and regulatory perspective, it can also be a significant contributor to productivity. In the global electronics industry, automated soldering processes are well established, and have helped to de-risk many of the predecessor manual procedures involved in soldering and the production of PCBs. However, while automation has advanced more efficient working practices, the fume inherent in these processes still needs to be extracted both to remove contaminated air from the working environment and to keep expensive technology and equipment free from contaminants that might otherwise impact on product quality.
In wave soldering, for example, PCB components are placed on the board and passed over a continuous wave of molten solder. Areas not to be soldered are covered with a protective ‘mask’. While this process doesn’t usually involve the potential harmful resin/colophony present in hand soldering, which can present health risks, it can require the use of an alcohol-based solvent such as Isopropyl Alcohol (IPA) and a small amount of organic acid, fume from which needs to be extracted and filtered.
Before soldering, the boards are ‘spray fluxed’, using either a general spray process, which can generate an airborne dispersion of the flux, or a targeted jet from a robotic nozzle. Either way, the airborne contaminants created need to be controlled through effective atmosphere management, which will mean investment in either portable fume extraction technology or a fixed vent-to-air system. With reflow soldering, solder paste is applied to the PCB and components are ‘picked and placed’. The board moves through various heating, stabilising and cooling zones, during which the solder metal ‘reflows’ or melts and solidifies around the component connection. During this process, the solvent which makes the paste liquify will evaporate and this airborne emission then needs to be filtered through an extraction unit. In addition, the fume from this process will include rosin content, which can present a risk to health if not controlled. A solder flux may also be used, which is likely to possess a significant concentration of ammonium chloride. As with wave soldering, operating temperatures need to be considered to ensure the effective filtration of any potentially harmful emissions.
These examples underline the need for effective atmosphere management and investing in
24 ELECTRICAL ENGINEERING • MARCH 2023
appropriate fume extraction and filtration systems, not just to provide an appropriate working environment for people but to fulfil mandated workplace exposure limits (WELs) covering defined substances and emissions. These WELs are presented as time weighted averages for either 15 minutes or 8 hours in ppm (parts per million) or mg/m3 (milligrams per metre cubed) and need to be scrupulously monitored and observed. The question then for factory and health and safety managers is how best to assess the most appropriate approach to fume extraction. The first step is to understand the quantity, size and chemical composition of particulate or fumes emitted, paying particular attention to the potential toxicity of each substance and any resultant chemical interaction. This assessment will also take account of any potential risk to health presented by the given process.
The results of this work will inform the design of the fume extraction system architecture, the filtration media used and the most appropriate monitoring and control mechanisms. From there, it’s a question of assessing the installation and life cycle costs of fixed or portable extraction system options, taking account of the mix of work relative to product volume, capacity
and type. Increasingly, the adoption of lean and agile working practices is leading to more electronics companies investing in portable extractions systems, such as those developed by BOFA, to maintain greater resource utilisation and manufacturing flexibility.
Effective fume extraction in electronics processes often needs to be achieved as part of a fully integrated system, which incorporates multi- stage filtration and activated carbon filters designed to capture chemical emissions. In addition, alongside its filtration technology,
BOFA has also developed a temperature control unit (TCU) that will simultaneously maintain PCB print area temperatures within a programmable 19 - 30oC range, accurate to within 1ºC thanks to integrated sensor-driven heaters and refrigerated cooling. The result is a system that helps to prevent process contamination, while any condensate produced is gravity-fed to a 5 litre container or piped to an external drain. Two capacitive level sensors monitor the condensate level. This also helps protect equipment from a build- up of debris on critical components, which might otherwise impact on product quality, lead to rework or even result in unplanned production line down time.
electricalengineeringmagazine.co.uk
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