Feature: Avionics
Newer replacement formulations of vapour degreasing fluids offer excellent performance whilst addressing environmental concerns
Enhancing avionic reliability and safety through PCB cleaning
By Elizabeth Norwood, Senior Chemist, MicroCare T
he aviation industry demands the highest level of reliability and precision to ensure safe and efficient flight operations. Printed circuit boards (PCBs)
used in avionic applications are custom designed and made to meet the rigorous requirements of the industry, such as withstanding extreme temperatures, vibration and harsh environmental conditions. To ensure compliance, there are stringent testing and quality control processes. Part of these processes is the proper cleaning of PCBs, since contamination poses a significant risk to PCB performance and functionality – even the smallest speck of dust or mark can result in intermittent or complete failure, leading to operational disruptions or, worse, accidents. It’s near impossible to avoid PCB
exposure to contaminants during their fabrication, transport and storage. Yet, dust, oils, flux residue and uncured solder
pastes can lead to poor solder joints, bridging, dendrite growth, incomplete conformal coating adhesion and other issues, resulting in PCB failure. With increased complexity and
miniaturisation, PCBs have become more difficult to access and clean properly, and cleaning PCBs in avionics is an even more challenging task due to their intricate design and tightly-packed components. Hence, developing effective cleaning procedures that reliably remove contaminants without damaging delicate components is crucial.
Vapour degreasing One cleaning method that has emerged as highly efficient for avionic PCBs is vapour degreasing. Tis process involves immersing the PCBs in a cleaning fluid within a vapour degreaser machine. Te fluid is continuously filtered and distilled inside the vapour degreaser to dissolve or liſt contaminants from the PCB’s surface. In some instances, ultrasonic agitation is
42 September 2023
www.electronicsworld.co.uk
added for additional cleaning power. Aſter being liſted from within the
cleaning fluid, PCBs undergo vapour rinse and drying. Te cleaning fluid condenses and drips back into the vapour degreaser for re-use. Te vapour degreaser recycles and re-uses the cleaning fluid hundreds of times before it needs to be refreshed or replaced. Tis helps reduce the cost of hazardous waste removal. Aſter a typical cleaning cycle of up to 20
minutes, the PCBs come out clean, rinsed, dry and ready for conformal coating, assembly and packaging. Vapour degreasing is fast and efficient,
offering high throughput and being easy to integrate into standard production lines. However, its effectiveness relies heavily on the choice of appropriate cleaning fluid. Most modern cleaning fluids are a mixture of compounds that can include hydrocarbons like mineral spirits, isopropanol and ethanol. Te vapour degreaser can use just one type of cleaning fluid, or fluid suppliers can mix and blend
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