Test and Measurement Handbook 2020

Page 30

TEST & MEASUREMENT HANDBOOK

Detecting counterfeit integrated circuits without a microscope Curve-trace testing can reveal whether an incoming batch of ICs are bogus without resorting to destructive inspection measures.

MAKING FAKE “lookalike” integrated circuits which resemble real ones takes minimal skill. It may simply require finding cheap parts in the same package and applying new markings. This problem has arisen due to the high value of electronics parts, and the whole manufacturing chain from assembly house to end-user is vulnerable. There are several methods the counterfeiters use to produce their fake goods. Consider just one means, salvaging ICs from old circuit boards. ICs recycled from old PCBs are often so old that they contain lead or other materials now banned by RoHS. Moreover, those built to use tin-lead solder were built to use relatively low peak solder reflow temperatures (typically below 235°C). Today’s lead-free IC packages now see peak reflow temperatures as high as 260°C. Manufacturers that mount what they believe are lead-free ICs

ALAN LOWNE | SAELIG

can unknowingly induce major reliability hazards such as cracking or delamination of the package. Conversely, counterfeiters may mark lead-free packages as leadbearing to meet demands for legacy lead-bearing packages. This may cause tin whiskers to form between adjacent pins and solder balls on ICs. To better mimic original parts, counterfeiters now largely mark IC packages with lasers rather than ink. The problem is that counterfeiters usually do not know the depth of bond wires in plastic packages, especially when they have thinned these packages by chemically or mechanically removing the original package markings. So the fake laser-marking process sometimes partially melts bond wires. Bad laser marking can also compromise hermetic packages. In one case, counterfeiters laser-marked iron-based IC lids plated with nickel and gold. The laser fully removed both layers of plating to expose the underlying iron. Prolonged exposure to moisture would corrode away the iron, allowing moisture ingression. Also in attempting to make old components look new, counterfeiters typically can use acids on package pins and solder balls. These acids may be incompatible

SENTRY contains all the hardware required to analyze the electrical characteristics of ICs with up to 256 pins. 256 pins+ devices can also be tested by rotating the device (BGA, QFP) to allow all pins to be learned and compared. SENTRY contains four 48-pin dual-in-line (DIL) zero-insertion-force (ZIF) sockets; these can be used directly for older DIP components but can also be used to accommodate a variety of additional socket adapters available for different package types. The socket adapter can contain multiple IC sockets to allow testing several ICs simultaneously or comparing one IC with another. An expansion connector allows custom socket adapters with up to 256 pins to be attached.

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DESIGN WORLD — EE NETWORK

6 • 2020

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