Counterfeit Component: Design Rules and Process Limits
A counterfeit component is a part that is presented as something it is not. It may be a genuine device of a lower grade relabelled, a device recovered from scrap and cleaned, a functional copy made on a different process, or a part that failed the maker’s test and was diverted. The common thread is that the paperwork is wrong, and the reason counterfeits reach production lines is almost always that the paperwork was accepted without any physical check.
How Counterfeits Reach a Line
The usual route is an urgent shortage. A part is out of stock at the authorised distributor, a broker offers it with a plausible lead time, and the purchase is made to keep a line running. The second route is a slow erosion of the approved supplier list, where a buyer who has been reliable is allowed to source from an unauthorised channel without a change to the approval. The third is a return to the market of parts that were previously sold and rejected.
Recycled parts are the most common category. A device removed from a scrapped board is cleaned, its leads are re-tinned and straightened, and it is re-marked and re-reeled. The re-tinning removes the original finish and leaves a surface that often looks plausible but that has a different solderability and a different thermal history. The re-marking covers the original marking with a thin layer, which is the detail that most visual inspections are designed to find. The supplier qualification process is the first line of defence, and it should include the requirement that the full chain of custody is documented.
Paperwork and Traceability Checks
The paperwork check is cheap and it catches a large proportion of cases. The things to compare are the part number on the label against the part number in the purchase order, the date code against the age the part should be, the lot quantities against the reel or tray counts, and the manufacturer’s name against the authorised list. A date code that is impossibly recent for a discontinued device, or a reel whose label does not match the manufacturer’s format, is a warning.
The check should also cover the physical documents. A certificate of conformance that is a photocopy, a test report with no lot number, or a label that has been overprinted are all evidence that the part has passed through an extra pair of hands. Where the supplier cannot provide the chain of custody, the part should be treated as suspect regardless of its appearance. The incoming inspection procedure should state which documents are mandatory and what happens when they are missing.
Visual and Marking Inspection
Visual inspection looks for inconsistency rather than for a known defect. The marking on a group of parts from one lot should be identical in font, position and depth; a part whose marking is slightly different from the others in the same lot is the most common finding. The same check applies to the lead finish, the body texture and the moulding flash, which differ between manufacturers and often between production sites of the same manufacturer.
The inspection needs magnification and good lighting, and it needs a reference. Keeping a known-good sample of each critical part, obtained from an authorised source and stored for the purpose, gives the inspector something to compare against rather than a memory. Where a part is critical, the reference should include the marking photographs, the body dimensions and the lead finish, because a comparison against a photograph is repeatable in a way that a comparison against a memory is not.
Marking Permanency and Blacktopping
A re-marked part usually has a coating under the new marking, applied to hide the original. The test for it is simple and is one of the most effective available: wipe the marking with a solvent such as acetone and observe. A genuine laser-marked part is unaffected; a re-marked part will lose its marking, or the coating will smear and reveal the original beneath. The test is destructive in the sense that it removes the marking, so it is applied to a sample rather than to every part.
The test should be done with a controlled technique, using a swab and a defined solvent, and the result recorded. A part whose marking is removed by the solvent is not acceptable for use, and the whole lot should be quarantined. Where the marking survives but the surface below shows a ridge or a change in texture, the same conclusion applies. The inspection stages should place this test at incoming inspection, because it is cheap and it stops the lot before it reaches production.
X-ray, XRF and Material Checks
X-ray inspection shows the internal structure: the die size and position, the lead frame, the wire bonds and any voiding. A part that has been re-marked often contains a die that does not match the marking, and comparing the die image against a known-good reference is one of the strongest checks available. Where the lot is high value or safety critical, X-ray of a sample is worth the cost of the equipment or of an external service.
X-ray fluorescence measures the elemental composition of the surface, which identifies the lead finish and can detect a coating that should not be there. It is quick, non-destructive and useful for confirming that a part is lead-free when the marking says so. Material analysis does not prove authenticity, but a result that contradicts the documentation is proof of a problem, and it is that contradiction rather than the technique itself that provides the value.
Electrical and Functional Verification
Electrical testing is the last line and the only one that proves function. A curve trace of the pins against the ground pin shows the input and output characteristics, and comparing that trace against a known-good part reveals a different die immediately for many device types. It is quick and requires little more than a curve tracer or a suitable test fixture, which makes it practical as a lot sample test.
Full functional testing under the specified conditions is the definitive check, and it is what a test house provides for high-risk lots. It is expensive and slow, so it is reserved for parts where the consequence of a failure is severe. Where the part is programmed, comparing the read-back of a known pattern against the expected data is a useful intermediate test that also detects a part that has been erased and re-sold as new. The acceptance criteria for each check belong in the incoming inspection plan, together with the sample size and the action on failure.
What to Do With a Suspect Part
A suspect part should be segregated immediately, physically and in the records. It should not be returned to the supplier before the evidence is documented, because the part may be the only proof of what happened. Photographs, the packaging, the labels and the test results should be retained, and the customer should be informed where the part was destined for their product.
The lot should be quarantined pending a decision, and no part from it should be used while the question is open. Where counterfeiting is confirmed, the supplier should be removed from the approved list and the purchase route examined, because the same route will produce more counterfeits. Where the part is already in production, the affected assemblies should be identified from the traceability records so that a recall decision can be made on evidence rather than on estimate. The incoming inspection record should support that traceability.
Building the Programme
A workable programme has four elements: an approved supplier list with an enforced chain of custody, an incoming inspection plan that matches the risk of each part, a set of reference samples for the critical parts, and a defined procedure for handling a suspect lot. Each of the four is inexpensive; what they require is the decision to apply them consistently, including when a line is under pressure to keep running.
The risk ranking should follow the part, not the price. A part that is in short supply, discontinued, or available only through brokers is high risk regardless of its cost, and it should receive the marking permanency test and the electrical check on every lot. The programme should be reviewed when a part becomes scarce, because that is the moment when the temptation to bypass it is greatest.
FAQ
Is buying from a broker always unsafe? No, but it removes the guarantee of the chain of custody, so the inspection burden moves to the buyer. Where a broker is used, the lot should be treated as high risk and the checks applied accordingly, rather than assumed to be genuine because the previous lot was.
Does the marking test damage the part? It removes the marking, so the tested part should be scrapped. That is why the test is applied to a sample of a few parts per lot rather than to the whole lot, and the cost of the sample is small compared with the cost of a production escape.
Can a counterfeit be detected electrically with confidence? A curve trace will detect a different die in many cases, and a functional test will detect it in nearly all. Neither proves authenticity on its own, but a contradiction between the measurement and the documentation is conclusive evidence of a problem and justifies rejection of the lot.
