The engineering validation test build is the first time you combine looks-like and works-like into one form factor, with production intent materials and manufacturing processes.
14 pages of definitions, workflows, best practices, and common causes for delay at each phase.
The engineering validation test build is the first time you combine
looks-like and works-like into one form
factor, with production intent materials and
This is a critical stage for electronics products, after your initial prototype, but before units are ready for real-world environmental testing or regulatory certifications like FCC or UL.
It's also an important step in the relationship between design engineers and the contract manufacturer (CM), as this is the first build where the CM is assembling the product. As such, engineers are typically present in-person for the EVT build, or available for live conversation or feedback with the CM. (If a team is using Instrumental, PD engineers may track the build live via their Instrumental dashboard to provide real-time feedback, if they are unable to be present in the factory.)
What is the purpose of Engineering Validation?
Engineering validation testing has several goals. First, the aim is to select a final production-intent design, potentially from a build matrix of options that were developed during prototyping.
A secondary goal is to identify issues with the design that may need to be fixed before it can be produced at scale. The hope is that major design issues are identified and resolved during engineering validation and do not make it into your next build phase - design validation.
What is the typical quantity produced during EVT?
Engineering validation testing runs typically involve between 100 and 1,000 units.
Units must be fully functional and
testable, made from the intended
materials and with the intended
manufacturing process, though they may be made from soft tooling since it is still very likely that design changes will be required.
(Hint: If you're using 3D printed parts, it's not EVT - you're still prototyping! This distinction is important because units made via processes that are substantially different from the final mass production process are much more likely to fail downstream tests and require more significant rework than expected.)
During EVT, all functional test stations must be present and collecting data.
What types of things might go wrong during EVT?
Engineering validation is the time to test and iterate on design. It may involve multiple cycles of issue discovery, solving, and validation that a design or process change fixed the issue.
Often in consumer electronics, program schedules provide for only one EVT build, but in reality this stage requires testing and iteration and frequently extends to multiple builds as engineers discover additional issues.
A typical EVT may last 6-9 weeks with periods of building, testing, and design iteration, and it's not unusual for 40%+ of units to be cast off as scrap.
A few factors that cause delays during EVT are:
When is EVT complete?
Engineering validation is complete when the product design team has settled on one production-worthy configuration that meets all of the product requirements (the PRD) for functionality, performance, and reliability.
Additional resources for engineering validation testing:
Instrumental captures images on the assembly line and leverages AI to detect defects and enable manufacturing optimization from anywhere.