In November of 2010, Jim Williams told me that Linear Technology, now part of Analog Devices, was seeing more and more counterfeit ICs. This is where some unscrupulous semiconductor company mislabels its inferior parts with Linear Tech’s or some other top-tier company’s logo and part number. They can sell the parts for a lot more money. Then the poor systems company that bought these chips would see they did not work in production and it would blame Linear Tech.
Sometimes a simple X-ray of the part would show it was not really an LT die in the package. Other times, Linear would “decap” the part, dissolving the plastic with fuming nitric acid, so that they could then see the die was a counterfeit (see figure). Occasionally there was no die at all, or a die that did not have bond wires to the IC pads.
Jim said that in the old days, he would hear about a counterfeit part maybe once a month. By 2010, he said it was happening multiple times per week. I saw this happen at National Semiconductor (now Texas Instruments) as well. A customer would be ranting at how we sold him thousands of bad parts. When we asked where he got the parts, he answered that it was some small gray-market distributor. We could see from the date code that the parts were counterfeit. I never saw a person change from yelling to begging so fast. He asked if there was any way National could get him 4000 parts that week. We did find him some parts, despite his being a low-volume customer. We warned him to be wary of any more “great unbelievable deals” from shady distributors.
This is one of the best reasons to pay a fair price from top-tier vendors that you see on SourceESB. I have never heard of counterfeit parts coming from Digi-Key, Mouser, or Newark. Arrow and Premier Farnell are trustworthy as well. This is not to say you can’t use smaller distributors or even those gray-market ones. Just be prepared to do an incoming test on the parts to ensure they meet all the specs. If so, it’s a good bet they are genuine.