We now must recognize that “commercial” is an important part of COTS. Commercial suppliers make economic decisions. Parts may be discontinued. Suppliers may cater to the majority of their customers who demand lead-free terminations and neglect those that need tin-lead terminations. They may discontinue the tin-lead versions or, at least, make them only when ordered (and there goes the “off-the-shelf” aspect of COTS). Moreover, the manufacturer is free to change processes without having to prove equal performance and reliability. This is done with minimal relation to form, fit, and function, not reliability.
When a supplier decides to cancel a product it becomes obsolete. The manufacturer might offer a limited time for users to make a lifetime buy for specific parts. But even if the OEM can predict his expected usage, he has no backup for an unexpected revival of customer purchasing or for new equipment using the same circuit boards. Additionally, parts remaining on the shelf for extended periods of time suffer deterioration of solderability, moisture intrusion, contamination, and oxidation. The lifetime buy products will also all have the same aging date code while many of the OEM’s customers have date code restrictions, limiting their use sometimes to one year and almost never more than two years.
Now the OEM must either design in a new resistor involving costly analysis and possible requalification of equipment or identify a source for the discontinued precision resistor. The latter path often leads to counterfeiting. The buyer searches through distributors. The distributors search through specialty suppliers or even brokers. The specialty suppliers search through unregulated and unreliable sources, often in Asia. The unregulated sources seize on the opportunity; they begin to counterfeit the needed parts and sell them at a large mark-up under the camouflage of the lengthened supply chain back to the desperate OEM. Field failures increase. Reputations, and possibly lives, are at risk.
It is critically important for designers, component engineers, and designers to know their component manufacturers, their product commitments, their integrity, their reputation, the specific details of their products, the design and test links of their commercial products to their reliability-documented products, and to never, ever allow any unapproved links in the supply chain. Faced with the continuing concentrated ingenuity of the counterfeiting entities, everyone must protect themselves and the industry, in general, with scrupulously unrelenting vigilance and supply-chain control.
About the author
Yuval Hernik is Director Application Engineering at Vishay Precision Group (VPG).
Yuval Hernik (firstname.lastname@example.org) holds a B.Sc in electrical engineering from the Technion (Israel Institute of Technology). He has been a director of application engineering at Vishay Precision Group – Bulk Metal Foil resistors - since 2008.