December, 2012
www.us-tech.com
Page 55
X-Ray Inspection to Identify Counterfeit Parts R
By Dr. Bill Cardoso, Creative Electron, Inc., San Marcos, CA
adiography (x-ray inspection) is a technique that is central to all recent and upcoming coun-
terfeit detection standards, including IDEA 1010B, CCAP 101, AS5553, AS6081, and AS6171. X-ray inspec- tion provides the unique ability to “see” what is inside an electronic component without damaging it. A top view x-ray of a real plastic
molded component has dark regions in the x-ray image that represent dense areas in the component. Conversely, the light areas represent light areas in the field of view. For this reason the area around the com- ponent is represented in white. The x- rays traveling through the different density areas of the component under inspection cast a shadow onto the camera. Thus this x-ray imaging tech- nique is also known as a shadowgram. A common technique used to
identify counterfeit components using x-rays is to utilize an exem- plar as a basis of comparison. The exemplar samples can be obtained in different ways. The usual method includes the comparison to compo- nents in previous lots that were obtained from trusted suppliers. In the event that such a priori
information is not available, it is possible to compare the part to another one currently in use. In this case, it is often necessary to x-ray
As long as people have been in the business of inventing, others have been in the business of faking their inventions.
the printed circuit board with the assembled component. Both options, if available, must be used carefully, as manufacturers can change the leadframe structure, die size, and wire bonding schemes without notice. Therefore, it is imperative that the user seek more information on the part before judging it to be suspect. The major challenge in deter-
mining a component’s counterfeit status is the usual lack of an exem- plar that can be used as a basis of comparison. The most common strat- egy used in this case is to perform the comparison with parts of the same lot. This in-lot comparison can be very powerful, because all parts within the lot must be identical. However, oftentimes counterfeiters re-mark different parts (that do not have identical x-ray images) to fulfill an order. Even if you do have an exem-
plar available, it is also common to find counterfeit components mixed with good parts. That is the counter- feiters’ attempt to circumvent detec- tion by customers who perform tests of just a few “sample” parts in the lot. For this reason, it is imperative that all parts are tested to assure homo- geneity within a lot. Until fairly recently, testing
thousands of components was cost- prohibitive. However, recent break- throughs in the automation of radi- ography inspection have made it pos- sible and feasible. New systems in the market make possible reel-to-reel automated inspection of thousands of parts in trays, tubes, or reels.
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Photo of a section of the reel, (left) all components showing identical part number, date code, and part number and (right) overlaid x-ray image onto photo showing mixed components.
Common Inconsistencies When looking for counterfeits,
the most common things you may Inconsistent die size; because the
find inside the components are: l
die is a thin piece of silicon, a top view x-ray image will likely not show the die. However, the die attach fillet is dense enough to appear in a top view x-ray image. As a result, the size of the die can be determined by measuring the boundaries created by the die attach fillet. Since counter- feiters often re-mark different parts to pass as the part wanted on the market, it is almost inevitable they
Continued on next page
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