INDUSTRY FOCUS - AUTOMOTIVE ELECTRONICS Gold standard practices in automotive


conformal coating processes Joe Booth, CEO, Altus Group


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odern vehicles now depend on complex electronics, from driver- assistance systems and EV power components to infotainment modules. These systems operate in harsh conditions, including vibration, temperature changes, humidity and chemical exposure. Conformal coating, a thin protective layer on PCBAs, safeguards these electronics, ensuring performance and meeting safety standards. Reliable results require careful application, as minor variations affect coverage and long- term reliability.


Medium selection


Selecting the correct coating medium is crucial. While many manufacturers use customer-specified media, applications without defined preferences can benefit from advanced solutions. Gel-state nano coatings simplify setup, cut energy use, and reduce masking. These materials suit manual or automated processes, minimising labour, rework and variability. In automotive electronics, medium viscosity, flow and curing directly influence coverage and adhesion.


Masking and application Masking represents the most significant labour cost in manual conformal coating, often requiring up to 30–40 minutes to apply masking and the same to remove it. Automated systems can reduce masking by over 90 per cent, delivering substantial ROI through time savings. While complete elimination is possible for many assemblies, validation testing is essential assuming a 90


A non-contact jetting valve to selectively applying coatings (with UV trace) onto substrates with close keep out areas.


per cent reduction provides realistic expectations and significant returns. Modern conformal coating systems employ three application heads for optimal control. Spray heads efficiently cover large areas with moderate precision. Needle heads provide finer control for critical regions. Syringe heads, particularly with gel-state materials, enable precise deposition around sensitive areas creating, ‘dams’ around keep-out zones before spray application. Advanced systems can dispense UV-curable masking material in-line, then cure and coat within a single automated process.


Pre-cut shapes, 3D-printed connector boots and automated masking materials further reduce manual intervention while


Example conformal coating line layouts for nano coatings versus UV/solvent materials, highlighting differences in curing and inspection stages.


maintaining the repeatable precision required for automotive reliability standards.


PCB cleaning


Even when no-clean flux is used, pre-cleaning PCBAs represents the gold standard approach. Cleaning removes residues that could contribute to dendrite formation and creates consistent surface tension for uniform medium flow, resulting in a more stable coating process. The cleaning requirement ultimately depends on design authority specifications and expected product lifetime, longer-life applications benefit most from this additional process step.


Environmental control and pre- baking


Consistent environmental control is critical in conformal coating. Temperature and humidity variations during production shifts significantly impact quality, as warmer PCBs and medium react differently than colder ones. The key is maintaining consistency rather than achieving specific temperature or humidity levels. Sealed environments may be beneficial depending on automation level, particularly to address solvent odours. Pre-baking PCBAs ensures consistent board temperature and removes moisture, ensuring boards are bone dry, particularly important after cleaning processes or when production environments aren’t controlled. This consistency reduces variability between boards entering the coating process.


34 OCTOBER 2025 | ELECTRONICS FOR ENGINEERS


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