Mass produced electronics components and assemblies are much more reliable than a few decades ago. This is largely down to better manufacturing processes and techniques such as statistical process control, which creates a tight feedback loop from end-of-line testing to the manufacturing process.
But even with the quality improvements of general commercial grade products, there’s still a huge step up to meet the standards demanded in high-reliability markets such as aerospace, medical, nuclear and automotive electronics.
Electronics Assemblies for Aerospace
To understand the differences, you need to consider the intended service life, location and operating environment. To illustrate, there’s a gulf between a mobile phone with an expected lifespan of around four years and a critical piece of satellite equipment expected to operate in space for decades without being serviced.
The quality, process control and reliability bar is many notches higher. On top of the general (but rigorous) AS 9100 quality standards, there are a host of military-specific standards related to features such as conformal coatings.
Testing products for in-service reliability is critical. Product screening will subject each serial-numbered device to environmental tests that reflect the intended operating environment. The performance characteristics are recorded before, during and after testing. If there’s a significant drift in performance the product and possibly the batch will be scrapped.
Production volumes are a factor. For a production run of 1000 or fewer units, statistical process control isn’t as relevant. A single failure represents an unacceptable rate at that level of volume.
Medical Electronics
The critical quality standard for medical equipment is ISO 13485. This has many similarities with the AS 9100 standards for defence and aerospace. The two standards set out to achieve similar things: strict control over supply chains, manufacturing and traceability – they just define them in a different context.
Automotive Electronic Assemblies
Automotive electronics illustrate how operating environments can vary within a single end product. Inside the engine compartment is a different environment to a vehicle cabin. Products may be subjected to different levels of vibration, temperature extremes or ambient conditions depending on where they’re fitted.
Design, manufacturing and testing for the intended operating environment is critical. Even though production volumes may be high compared to aerospace or medical applications, the electronic assembly can still be safety-critical and needs to have quality-assured reliability.
For all high-reliability electronics applications they key is to design-in reliability from the outset. This can affect practical issues such as component choice, how they’re arranged on the board and even the board thickness. Assemblies are then designed for the operating environment, manufactured from quality assured and fully traceable components and rigorously tested before entering service.
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