Industry News
The recent and severe semiconductor shortage has sparked renewed interest in semiconductor date codes, a method to measure the “freshness” of electronic components. Many manufacturers will not accept chips with expired date codes even if they pass various tests, further restricting semiconductor supplies.
When semiconductor date codes were implemented back in the 1960s, the goal was to maintain the traceability of parts, based on manufacturing or seal dates, processes, and bill of materials, as well as a 2-to-3-year “sell-by” date, according to Rochester Electronics. Historically, it was believed that components were no longer usable post their listed date codes.
However, date codes are no longer a reliable indicator of the quality of components and may prevent the use of perfectly viable components.
Today’s industry has changed substantially, as original component manufacturers (OCM) move to shorter product lifecycles, Rochester reports. Consumer applications drive demand for semiconductors but have short lifetimes as well. Still, some industries require longer semiconductor component lifecycles. Industrial, medical, aerospace, and defense industries might need application lifetimes measured in decades. In these cases, maintaining ongoing component supply is critical to sustaining application lifecycles. Since vital components may be discontinued, a common solution is to store those components for an extended amount of time.
New cars, aircraft, and industrial controllers will typically spend 5 years in design and qualification stages, have another 5-to-7 in product, and end with 7-to-10 requiring aftermarket support, according to Rochester. Adding it all up, it isn’t unknown to require up to 20 years of component supply. When looking at applications with extended lifetimes and for customers considering a long-term storage solution, having confidence that products maintain their quality and reliability is key. Yet, after so long, are those parts reliable? Are they of quality? What even is a safe shelf life for semiconductor components?
Despite the continued use of date codes by OCMs as a measure of quality, mounting evidence indicates that this is not an accurate measure of products. Almost all components are usable beyond that date. In fact, Rochester Electronics has been successfully storing components for extended periods since 1981.
Date codes are also problematic to the supply chain. Expired products are supposed to be returned to OCMs, but many get sold into the open market. If returned, component prices have likely changed between the time of purchase and return; the difference is often reflected as a credit. OCMs typically have to dispose of expired products. There are costs associated with these practices, which might be destroying perfectly usable components.
No evidence of degradation
“Tin whiskers,” which are small structures that grow off tin component leads, can be a cause for concern for many end-users. These tiny structures have been known to grow up to 10 millimetres and can result in electrical damage to components. Although commonly believed to be linked to the age of components, NASA has found no evidence to support this claim. Not content to only rest with this proof, Rochester Electronics’ Quality and Reliability team investigated the effects of long-term storage on both mechanical integrity and electrical performance for components.
Rochester analysed a range of components, each stored for up to 17 years. Working intensively on two studies, Rochester performed tests on solderability, package integrity, joint quality, electric viability, and assembly functionality. The results show that not only did the components not degrade, but in fact, components can still be functionally assembled and are electrically viable for many years when properly stored.
Texas Instruments has conducted several white papers exploring the reliability and quality of components after extended periods of storage. One initial study revealed that semiconductor products that are properly stored in controlled environments can last beyond 15 years. Furthermore, a subsequent Texas Instruments paper discovered that components stored for up to 21 years showed no signs of failure mechanisms. It is important to note that these studies are based on components that have been stored in controlled environments.
Policy recommendations
The Electronics Components Industry Association (ECIA) is now recommending an end to general date code restrictions. “Forty years ago, there may have been some truth to this perception. However, the last four decades of process improvements by electronic component manufacturers have all but eliminated the causes of failure mechanisms related to component age concerns,” it stated.
In a recent June 2023 policy recommendation, ECIA suggests that customers order from businesses that have the authorizations and certifications to assure all buyers that:
· All packaging, shelf life, and storage requirements are understood and complied with.
· Product warranties will be supported.
· Product change notices are distributed and complied with, including product recalls, quality alerts, and packaging changes.
· Reports of specific component issues by customers will be reported to manufacturers and suspect stock will be appropriately quarantined.
· Order management processes will provide for appropriate review, quoting, and conformance to customer-specified date code restrictions.
ECIA believes that “general date code restrictions unnecessarily delay the order entry process and delay the order fulfilment process, resulting in delayed service to the customer. General date code restrictions result in further aging inventory in the supply chain by disrupting normal FIFO (first-in first-out) consumption.”
Multiple industry leaders have tackled the issue of how to maintain a source of long-lifecycle components, Rochester concludes. Through years of diligent research and testing, long-term storage has not only been found to be possible but an important option to consider. It is safe, available, controlled, and ready. Purchasers no longer need to fear component “expiration dates.” They can feel confident that properly stored components will not only be reliable in the field, but of high quality well past their date code.
Rochester Electronics staff contributed to this article.