Feature: Avionics
Figure 3: Vapour degreasing is exceptionally effective at cleaning large batches of avionic PCBs
thereby reducing costs and environmental impact. Aſter a typical cleaning cycle lasting
between six and 20 minutes, the PCBs emerge pristine, rinsed, dried and primed for later procedures, like conformal coating, assembly or packaging. Vapour degreasing offers several advantages, including high throughput, energy efficiency and seamless integration into standard production lines. It also ensures consistency and repeatability during production, thus reducing variations and ESD-related failures.
Choosing vapour degreasing fluid Choosing the right cleaning fluid is paramount for the success of vapour degreasing in avionic PCB cleaning. Most contemporary cleaning fluids consist of various compounds, including hydrocarbons like mineral spirits, isopropanol and ethanol. Vapour degreasers can use a single type of cleaning fluid, or suppliers can
customise blends to target specific soils on substrates, maximising cleaning efficiency. Modern cleaning fluids offer a balance of stability, performance and eco- friendliness, ensuring a safer and cleaner work environment. Here are some factors to consider when choosing a vapour degreasing fluid for avionic PCB cleaning: • Nonflammability: Opting for nonflammable cleaning fluids enhances safety during handling and storage, ending the need for specialised equipment and simplifying the overall process. Most vapour degreasers are engineered to work smoothly with nonflammable cleaning fluids.
• Low boiling point: Choosing cleaning fluids with a boiling point below 100°C promotes energy efficiency and safety. Lower boiling temperatures enable effective PCB cleaning without risking damage to delicate avionic components.
• Low surface tension and viscosity: Selecting fluids with low surface tension and viscosity ensures thorough wetting of
the PCB surface, reaching into tight areas and under low-mounted components for comprehensive cleaning.
• High-density: High-density fluids, heavier than water and alcohol, are effective for removing non-dissolvable particulates like dust and dirt from PCB surfaces, enhancing overall cleaning efficiency.
• Solvency: Te strength of the cleaning fluid, oſten shown as a Kb value, should be sufficient to dissolve and remove contaminants without harming PCB substrates.
• Maintenance-free: Modern vapour degreasing fluids oſten require minimal maintenance, staying stable without the need for frequent testing or analysis, thus streamlining the cleaning process.
• Environmental stability: Newer cleaning fluid formulations offer excellent performance whilst addressing environmental concerns by reducing greenhouse gas emissions and following air quality regulations, contributing to a cleaner and safer environment.
www.electronicsworld.co.uk April 2024 39
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