Feature: Avionics
Battling ESD in avionic electronics production By Elizabeth Norwood, Senior Chemist, MicroCare
T
he aviation industry demands unparalleled reliability and precision to ensure the safety and efficiency of operations. Printed circuit boards
(PCBs) are indispensable components within avionic systems, serving as the backbone for critical functions such as flight control, data communication and navigation. Te precision and reliability of these PCBs are therefore crucial. However, maintaining their reliability requires diligent PCB cleaning practices, as ESD (electrostatic discharge) or even minor contamination pose a considerable risk, leading to intermittent malfunctions or complete failure, or to disruptions and even accidents. Tus, proper ESD dissipation and PCB cleaning are paramount to safeguarding the integrity and functionality of avionic systems.
ESD in avionic electronics ESD poses a significant threat to fragile
electronic components ranging from resistors, capacitors and inductors to contacts, relays, switches and connectors. ESD occurs when two surfaces or objects with different electrical charges come into contact, allowing electrons to flow between them, equalising the charges and creating a discharge. Tis sudden release of charge manifests as an ESD pulse. ESD that surpasses the PCB’s ratings
can inflict two types of damage on electronic components: catastrophic and latent. Catastrophic damage leads to immediate and complete part failure that is easily detectable during inspections. Since this type of damage is found early in the manufacturing process, its impact on production time, yield and costs is minimal. In contrast, latent ESD damage is challenging to detect initially, but can gradually diminish the performance and reliability of the PCB over time. Although a latent-damaged PCB may appear functional, it could be partially degraded, leading to eventual malfunction or failure
Figure 1: ESD dissipation and PCB cleaning are paramount to
safeguarding the integrity and functionality of avionic PCBs
in the field. Tis scenario poses significant risks, potentially harming a company’s reputation and causing costly recalls; it could even pose safety hazards depending on the PCB failure.
Sources of ESD
1. Humans and machines ESD incidents can occur at any phase of the PCB manufacturing and assembly process, with human touch oſten being a primary cause. Te human body, along with specific clothing materials, can amass static electricity up to 2,500V during a standard workday. Manufacturing zones involving manual tasks like assembly, repair, inspection and packaging are especially prone to ESD. In addition to human contact, ESD
can originate from ungrounded electrical testing equipment or other machinery causing friction; see Figure 2. Even swiſt, dry air currents flowing near PCBs, like those created by facility fans or air compressors, can cause static.
www.electronicsworld.co.uk April 2024 37
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