|Optical and x-ray images compare known-good (left) and counterfeit (right) ultrafast diodes. |
Counterfeit components are now a real concern in electronics assembly, not just for expensive items but more and more for lower-costing components. Many involved in PCB assembly will admit to having received counterfeit components in the past, and/or know someone who has. A counterfeit component is defined as an item for which external details appear to resemble one object but the item is actually a different object. This definition does not apply to items that have been recycled or recovered from waste PCBs, which are typically honestly represented as what they are: pre-owned or pre-used components. While other issues may apply to pre-owned components, they are not counterfeits.
Best practices always involve obtaining electronic components only from trusted and reputable suppliers, but market pressures sometimes make it difficult for even the best of suppliers to provide the right parts when they are needed. When a difficult-to-find component cannot be found from normal supply channels, one resource is to turn to the Internet. Unfortunately, counterfeiters prey upon such opportunities. Even when receiving "gray market" items from a regular supplier, if the component has sufficient value (high enough margins), testing and quality assurance steps will be taken to ensure the quality of the parts.
Lower Value Items
When lower-value devices are also being counterfeited (values of $10 or less), they are often more difficult to detect. Such devices are most dangerous to a business and its reputation. A capable counterfeiter may supply a small quantity of genuine items for quality verification and/or include a small number of real components at the head of the reel in an effort to pass the counterfeit items. Because many plastic-packaged components are sensitive to moisture, components may arrive in special moisture-proof packaging, and most customers and contract assembly companies may be reluctant to check inside for fear of exposing the components to moisture in the air. As a result, as long as the external label has the correct information, counterfeit components will be accepted for use in production.
|Optical images show the terminations of known-good and counterfeit (on right) ultrafast diodes. |
While it may be practical to perform some analytical checks on a few components (usually off the end of a reel), it may not be as reasonable to check all samples at incoming inspection, or all components on every (low-cost) incoming reel of components. Because of this, counterfeit components can readily enter a production floor and manufacturing process. This is also true for the same items purchased through a legitimate supply chain as, again, a supplier may not find it practical to check every component, without having to dramatically increase the cost of the components.
What Can Be Done?
Efforts to detect counterfeit components rely on a number of different inspection techniques, including optical and x-ray inspection. Quick visual inspections are often the main acceptance tests for checking incoming components (particularly for low value items). But particularly when undertaken without a microscope, it is relatively easy for a counterfeiter to modify fake items to pass this test. The number of terminations may be correct, the molding is the proper color, the shape and size of the components are consistent (at least to a superficial view), and the serial numbers and other printed information appear to be correct. Many components are similar, which is why they work so well in a surface-mount-technology (SMT) assembly process. Using only optical inspection, it is clear how counterfeit items can easily escape into production.
Using an x-ray inspection system with high magnification (including oblique views) and large gray-scale sensitivity within the images, it is possible to quickly, easily, and nondestructively see within suspect component packages. By taking images of known good samples that clearly indicate the correct wiring and subassembly alignments within the packages, production operators and inspectors can quickly compare known-good components with suspect components. If all is well, the inspected items can be passed directly for production use. However, if something is found to be wrong, not only have these counterfeit components been prevented from contaminating future production, but these x-ray tests can be made when the components are still within their original packaging.
|Aluminum wire connections at the leg of known-good (left) and counterfeit (right) ultrafast diodes. |
A number of other test methods can be used to detect counterfeit components. X-ray fluorescence can check components nondestructively for their chemical composition. This test can be used to detect the presence of lead in what may have been supplied as a lead-free component or material. Electrical testing can provide a simple and quick check of component functionality and if that component is right for a given application. However, electrical testing will not necessarily indicate if an off-the-shelf item is being masqueraded as a much higher-tolerance equivalent component.
Destructive testing can also be used in searching for counterfeit components, such as the use of infrared (IR) microscopy, which allows selected surfaces of die and bond sites/bonds to be examined without removing the moulding compound and exposing the top surface of the die. Component body packaging can also be removed for further optical examination against a known good example. Another destructive test is component delidding, which involves using a blade or other cutting tool to remove a component's lid so that optical inspection can be performed on the internal parts of the component. This test may reveal the component to be genuine, but this kind of inspection means that the component can no longer be used in production.
As an example of a lower-cost counterfeit component, an obsolete $10 value ultrafast diode became a target. Any optical comparison of a known good diode and a counterfeit shows them to be quite similar. But when the two items went into the x-ray inspection system, the differences internally were substantial. Die size and location as well as the number of interconnections were not the same. The counterfeit component appears to have been a modification of another component, as it has wire bonds and a die contained within it. The cut leg suggests that the original item, from which the counterfeit was made, was a transistor; testing with a meter shows no diode between the legs. It also appears that the heat sink of the counterfeit had been trimmed into the same shape as that of the original device. Although the counterfeit diode has no stamped detail in the heat sink, the heat sink finish is rough, the printing on the outside is not the same quality as the original, and it has an extra leg, although one that has been cut. The extra leg was not apparent from an optical inspection.
In another comparison, the over-molding in the center of a known-good component appears similar to the cut termination in the counterfeit. But a thorough and detailed optical examination by magnifying glass would quickly reveal the problem, although the time and expense of such an inspection may not be warranted by a $10 component. Further x-ray inspection of these two items also showed the aluminum wire count and the bonding also varied.
Of course, original component manufacturers may modify their designs, so that not all internal changes to a component may be indicative of counterfeits. Inspections rely on having known good reference samples to compare to suspect devices.
Electronics manufacturers can battle against counterfeits by developing a counterfeit investigation check list to reduce the possibility of counterfeit components being accepted into production. Should counterfeits be found, then each component at risk should have its own unique database reference file within a master spreadsheet, and a known-good reference component available for comparison. The counterfeit database file should also incorporate optical data, x-ray images, supplier data sheet, reference marking, component weight, and any other additional physical data for assisting in future analysis. The use of a spreadsheet approach, plus the retention of a known good part, is the most cost-effective, quick, and simple procedure to implement. It can quickly reduce the incidence of component counterfeiting, or at the very least enable quick examination of suspect items against known data. Furthermore, having such data on site will make the whole company aware of the overall risk that counterfeits provide and sensitize all employees to their ever-present risk. Adding x-ray inspection and other analytical techniques into goods acceptance procedures — or at least sharing these facilities with other manufacturing disciplines — requires personnel, time, and expense. But the investment can be large when compared to the potential costs of repair, loss of reputation, and possible loss of future business that counterfeits can cause.
Counterfeit electronic components are a concern for any production line. Unfortunately, counterfeiters don't just target expensive items, but lower-priced components as well. As a result, implementing effective methods for minimizing counterfeits is critical for any production process. The use of as many inspection tools as possible, including optical, electrical, and x-ray inspection systems, and the use of other nondestructive techniques can help minimize the risk of counterfeits. If all is well, then the components can be used in the manufacturing process. However, if there is a problem, and security seals have not been broken on the external packaging, the issue can be discussed earnestly and confidently with the supplier.
Contact: Nordson Dage Precision Industries, 28601 Clemens Road, Westlake, OH 44145 440-892-1580 fax: 440-892-9507 E-mail: email@example.com Web: http://www.nordsondage.com