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Understand obsolescence, counterfeiting and COTS

Posted: 01 Apr 2013     Print Version  Bookmark and Share

Keywords:commercial-off-the-shelf  obsolescence  component manufacturers 

Designers can now mix component technologies in the same applications even though different technologies have different defining characteristics. Precision resistors, for example, may have the same resistance value and tolerance but vary widely in temperature coefficient of resistance (TCR), power TCR (PCR), thermal EMF, current noise, harmonic distortion, ESD, thermal stabilisation, and end-of-life cumulative deviations (or total error envelope), none of which is automatically included in the resistor's identification by value and tolerance. Replacements or substitutions are made by form, fit, and function (FFF). Resistors are then purchased to fit the equipment's initial function, ignoring the performance and reliability effects of the other, unmentioned, characteristics. Data from which to make statistical predictions regarding failure rate or mean-time-to-failure (MTBF) is lacking. COTS also presumes that replacement parts are available when needed. It presumes continued supply by the manufacturer.

With established-reliability (ER) and EEE-INST-002 components, all critical performance characteristic were specified and demonstrated along with documented reliability. With COTS, the design and purchasing decisions are focused on price, manufacturer claims, and BOM costs. Equipment reliability becomes separated from parts and production costs. Purchasers are encouraged to buy from the cheapest source, equipment reliability is no longer linked to parts purchased, and repair costs increase along with field failures.

New sourcing problems
We now must recognise 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 ageing 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 speciality suppliers or even brokers. The speciality 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.

Summary
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 for Application Engineering at Vishay Precision Group (VPG).

Yuval Hernik 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.

To download the PDF version of this article, click here.


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