A young hardware company contacted me to get help with an urgent field issue: batteries were melting enclosures. Many previous batteries had performed correctly—shutting down if the battery got too hot during charging. However, in the most recent lot of thousands of units, some batteries were not shutting down as designed, creating thermal runaway that released smoke and melted enclosures.
Failure analysis revealed that an upstream vendor had made an unapproved change. This is a nightmare scenario: with only a lot number, it’s impossible to tell when the change occurred and which units already shipped to customers were also not built to the specification. Do you recall and replace the whole lot of thousands, even if there are only a few bad units? Depending on the severity, you might have to.
Traceability from Day 1 and Step 1
Traceability is where many companies cut corners in favor of the many other challenges involved in bringing a physical product to market, and they do so at great peril. The simplest (and most powerful!) form of traceability is assigning individual serial numbers to each unit, known as serialization. That unique serial number often encodes important “breadcrumb information,” such as the date and time, the line or machine number, the vendor name, the configuration or work order, etc. This detailed information makes tracing a change to a specific date and time possible.
Teams with experienced engineers know that serialization is important and will do it from Day 1. However, some take a shortcut to not add serialization until very late in their process, such as the last step before a unit goes in the box. Usually, this is a compromise with the manufacturing partner, who pushes back against the extra work involved in creating, printing, and tracking temporary barcodes from Step 1.
In the example above, if the company had Day 1 and Step 1 traceability, they could look up the serial numbers of the batteries in the affected lot to identify when the unapproved change had been made.
Serialization is so important to the hardware development process that it’s number five on the Shedletsky Test. If the product is complex or there are multiple vendors for a single component, teams should also serialize the modules: chips, PCBs, enclosure parts, displays, cameras, and more.
The combined information in these serial numbers can provide invaluable insights during failure analysis. While more advanced traceability is possible, the humble serial number unlocks many benefits to your hardware development process, enabling your team to start tracking other information on top of it—such as timestamps at key stations, performance-based test results, reliability results, and even field performance. These data points can help improve operational efficiency or accelerate your failure analysis process during development.
Implementing Serialization
Implementing basic unit serialization is usually easy. Ask your contract manufacturer to start printing barcode stickers, which will be scanned at key assembly or test stations and ultimately transferred to the final packaging. More advanced methods include laser etching the serial number on a visible part of the enclosure, enabling a customer to report the serial number back to you should anything happen in the field.
In the mission-critical electronics space, particularly aerospace and defense, some parts have been in production for decades. The original drawings do not have barcodes, so manufacturers cannot add them. The quality of those parts is often critical. Our best advice is to put the part in a tray or carrier with a barcode and leverage that for traceability.