Counterfeit: Key Checks Before Release
A counterfeit part rarely announces itself. It arrives on a reel that looks correct, with a label that scans, and it usually works, at least on the bench. Screening is therefore a process of collecting small inconsistencies until the evidence outweighs the convenience of using the parts, and it has to happen at incoming inspection because after reflow the trail is gone.
How Counterfeit Parts Enter the Supply Chain
Most counterfeit parts are not fabricated counterfeits. They are recovered components: parts removed from scrapped assemblies, cleaned, re-marked and re-reeled, then sold as new. Others are lower-grade parts relabeled as a higher temperature or speed grade, or parts from a different date code blended into a reel to fill a shortage. Each type leaves a different trace.
The commercial pressure that produces the problem is predictable, so the control has to be proportionate. Parts bought through franchised distribution carry the lowest risk, while parts bought on the open market during a shortage carry the highest. The traceability of where the parts came from therefore sets how much inspection they should receive. A part bought on the open market during a shortage should be assumed to need full screening, while one bought under a franchise agreement needs only the documentation and sampling checks that its risk category justifies.
Purchasing Evidence and Traceability Records
Start with the paperwork, because most counterfeit parts are caught there rather than on the bench. Check that the supplier is authorized, that the certificate of conformance names the manufacturer and the lot, and that the date codes on the packaging match the certificate and the reel label. Discrepancies between documents are the cheapest defect to find and the easiest to overlook.
Keep the shipping documents, the label photographs and the inspection record together for the parts that are released to production. When a suspected part is later found in the field, that file is what allows the affected assemblies to be identified, and without it a recall becomes a broad and expensive exercise instead of a targeted one.
Visual and Marking Inspection
Visual inspection under magnification looks for re-marking: a surface that has been abraded, a coat of black epoxy over the original marking, or laser marking that differs in depth and font from a known-good part. Compare against a golden sample rather than against a photograph, because marking styles change between manufacturing sites and over time.
Check the physical form as well. Pin one leads that were straightened after removal, solder residue on terminations, and a package body that has been cleaned to remove the evidence are all consistent with recovered parts. A first-article sample held in stock makes these comparisons fast, and a good light source makes the surface differences obvious.
<img src="https://www.gopcba.com/wp-content/uploads/2020/12/ptt_careers.jpg" alt="Incoming inspection of reeled electronic components at a receiving bench” />
Packaging, Labels and Moisture Indicators
Packaging carries a great deal of information. Re-reeled parts often show hand-spliced carrier tape, an inconsistent pocket pitch, or a reel whose label does not match the manufacturer’s current format. Moisture barrier bags that have been re-sealed, missing desiccant, or an MSL indicator card that has been reused are all signals worth investigating.
Where the parts are moisture sensitive, the packaging also affects the process. Re-reeled parts may have absorbed moisture during handling and storage, so the floor life assumptions in the process are no longer valid. Treat any repackaged moisture-sensitive part as suspect for both authenticity and for the bake decision. Where a barrier bag has been opened and resealed, the recorded floor life no longer applies, so a documented bake before use is the safe default rather than an assumption that the parts are dry.
Electrical and Functional Screening
Simple electrical checks catch the low-grade relabel: measure key parameters on a sample and compare the distribution against the datasheet limits rather than against a single pass or fail. A batch whose parameter distribution sits near the edge of the specification is consistent with parts that were sorted or downgraded rather than manufactured to that grade.
Curve tracing on a sample of pins detects electrical differences that a functional test at one condition misses, and it is fast enough to run on a receiving bench. Record the measured values rather than a pass or fail result, so a later lot can be compared against the same distribution even when the source changes. Where the risk is high, decapsulation of a sample reveals the die marking and the construction, which is definitive evidence when the die does not match the part number being sold.
Solderability and Surface Finish Clues
Recovered parts often fail solderability because their terminations have been through a reflow cycle and then cleaned. Run a wetting balance or dip test on a sample and compare the result against a new part of the same type; a wetting time that is markedly longer, or a termination that does not wet at all, is consistent with reuse.
Termination finish also gives a clue. Parts sold as lead-free that wet like tin-lead, or terminations that measure differently under X-ray fluorescence from the same part bought previously, indicate that the finish or the part itself has changed. XRF is fast, non-destructive, and worth running on every new lot of a critical part number.
X-ray and Internal Structure Comparison
X-ray inspection compares the internal structure of the delivered parts against a known-good sample: die size and position, wire bond layout, die attach voids and the lead frame outline. A part that looks identical outside but shows a different die footprint or a different bond pattern inside is not the part that was ordered, regardless of what the label says.
The comparison works best with an image library built from parts bought through authorized channels, so the reference exists before a shortage makes it urgent. Building that library takes an afternoon and turns a subjective judgement into a side-by-side comparison that a receiving inspector can make.
What to Do When a Part Is Suspect
Quarantine the lot, stop any assemblies built from it, and preserve the evidence in the condition it arrived. Notify the supplier in writing and keep the response, because the paper trail determines whether the parts can be returned and whether the incident has to be reported. Do not return the only sample of a suspect lot to the supplier before the internal analysis is finished.
Disposition should be decided by evidence rather than by schedule pressure. A lot that fails a definitive test, such as a die comparison that does not match, is rejected regardless of how urgently production needs it. A lot that raises only a documentation discrepancy may be releasable with additional testing, but that decision belongs in a written record.
Building the Control Into the Process
The strongest control is purchasing discipline: buy from authorized distribution, request the manufacturer’s traceability information, and treat open-market purchases as a separate risk category that always triggers inspection. A part number list ranked by risk lets the inspection effort sit where it changes the outcome.
Pair that with a receiving checklist that a trained inspector can complete quickly, and with a documented escalation path for a suspect lot. Inspection that depends on an expert being available on the day is inspection that gets skipped on the day it matters, and shortages are exactly when it matters most.
FAQ
What is the single best defence against counterfeit parts? Buying from authorized distribution and keeping the traceability records. Most counterfeit parts are identified through documentation before any bench test is needed.
Can a counterfeit part pass functional test? Often yes. Recovered and downgraded parts frequently work at the test condition, which is why electrical sampling looks at parameter distributions rather than a single pass or fail.
Why is XRF useful on incoming lots? It measures termination finish non-destructively, so a part sold as lead-free that measures like tin-lead, or one that differs from a previous lot, is flagged before it reaches the line.
