Counterfeit components are not primarily a consumer-electronics problem. They concentrate in exactly the segments where the price of a genuine part is high, the lead time is long, and the consequences of failure are serious: power modules, memory, analogue and mixed-signal devices, and anything with a military or industrial temperature grade.
There is no single test that proves a component is genuine. There is a ladder of methods, each with a different cost and a different power of detection. What matters is knowing which rung is appropriate for the value and criticality of the lot in front of you.
The ladder, from cheapest to most conclusive
| Level | Method | What it can catch | What it cannot catch |
|---|---|---|---|
| 1 | Traceability and documentation | Parts with no verifiable source, reused lots, inconsistent date codes | A well-documented counterfeit |
| 2 | Visual and dimensional inspection | Re-marking, sanding, re-tinning, wrong package, mixed date codes | A re-marked part that matches the original visually |
| 3 | X-ray inspection | Empty packages, wrong die size, missing bond wires, die from a different device | A die that is functionally similar but not equivalent |
| 4 | X-ray fluorescence (XRF) | Lead-free finish where a leaded finish is claimed, and the reverse; coating composition | Anything about the die itself |
| 5 | Decapsulation and die inspection | Wrong die, wrong manufacturer, re-used die, die markings | Destroys the sample; not a lot-screening method |
| 6 | Electrical curve tracing and parameter test | Devices outside specification, wrong part in the right package | A device that is in specification now but was salvaged |
| 7 | Functional test at rated load, plus reliability screening | Latent defects and wear-out behaviour | Nothing, but it is slow and expensive |
Levels 1 to 3 are the practical screening set for most incoming inspection. Levels 5 to 7 are for a sample per lot, or for a dispute with a supplier.
Level 1: traceability first
Before any physical test, ask where the parts came from and whether the answer survives scrutiny. Genuine stock from an authorised channel comes with a chain: manufacturer, distributor, invoice, date code, and often country of origin.
Red flags at this level:
- A price materially below the market for the same date code and grade.
- A date code that does not match the other markings, or a mixture of date codes in one sealed bag.
- A part described as "new" but supplied in bags, without the manufacturer's original packaging.
- Documents that describe the part differently from the label: a different grade, a different temperature range, a different suffix.
- A supplier who will not provide a photograph of the actual goods before shipment.
Level 2: visual and dimensional inspection
This is the highest-value step per minute spent. With a low-power microscope and a good light, most re-marked parts give themselves away.
- Laser-etched versus printed markings. Most modern manufacturers laser-mark. If the part was specified with laser marking and the sample shows ink, that is a finding.
- Marking surface. Sanding or grinding to remove the original marking leaves visible abrasion, rounded package edges, or a surface that reflects light differently from the rest of the body.
- Re-tinned leads. Salvaged parts often have their leads re-tinned. Look for solder that is thicker or smoother than the manufacturer's plating, darker or uneven colour, and solder that has wicked up onto the package body.
- Package dimensions. Measure the body, the lead pitch and the lead thickness. A part in the right nominal package is sometimes a different thickness.
- Date code and lot consistency. All markings should tell the same story. A 2015 date code on a part that has been produced only since 2020 is conclusive.
- Pin one indicators and logo. Compare against a known-good sample or the manufacturer's drawing, not against a photograph from a marketplace listing.
Level 3: X-ray inspection
X-ray looks inside without destroying the sample, which makes it the key screening tool for power modules and BGAs. For a power module, the questions are the die area, the number and position of bond wires, the solder layer between die and baseplate, and whether the internal layout matches the expected topology.
For a BGA memory device, X-ray shows the ball array and any voids in the balls, and it can reveal a die that is far smaller than the package would suggest. A large package with a small die is a strong indicator of a substituted part.
X-ray also catches the crudest counterfeit: an empty package, or a package with no die attached at all. That failure mode is more common than most buyers expect, particularly in parts bought at auction.
Level 4: XRF and surface composition
XRF reveals the elemental composition of the surface it is pointed at. It is most useful for checking lead-frame and lead finishes: whether a tin-lead finish was replaced by pure tin, or whether parts claimed to be lead-free carry a leaded finish. A change in finish is a strong hint of re-tinning after salvage.
It tells you nothing about the die, and it is a surface measurement only. Treat it as a corroborating test rather than a verdict.
Level 5: decapsulation
Removing the package and inspecting the die is the most conclusive test available. It reveals the die manufacturer's logo and mask markings, the die revision, and the layout. A genuine-looking package with the wrong die inside is a fact, not an opinion.
The cost is that the sample is destroyed, and the process requires controlled acid handling. It belongs in a supplier dispute or a high-value incoming inspection, not in routine receiving.
Level 6: electrical curve tracing
A curve tracer applies voltage across two pins and plots the resulting current. Comparing the signature of the suspect part with a known-good part reveals differences in junction behaviour immediately: a different breakdown voltage, a different forward drop, or a leakage path that should not exist.
This is fast, non-destructive, and can be applied to a sample from every lot. It is particularly effective against the "same package, different device" counterfeit and against parts that have been electrically degraded.
The counterfeit types you are actually looking for
The highest-risk categories are not exotic. They are the parts that carry a high genuine price, a long lead time, or both: power modules such as IGBT half-bridge modules, thyristor modules, IPM and PM series modules and phase-control thyristor modules, together with managed memory and analogue devices.
- Re-marked. A cheaper or lower-grade device given the markings of an expensive one. The most common type, and the one visual inspection is designed to catch.
- Recycled or salvaged. Parts removed from scrapped boards, cleaned, re-tinned and sold as new. Electrically they may pass, but their remaining life is unknown and their moisture history is unknown.
- Rejected or out-of-specification. Devices that failed the manufacturer's test and left the factory through an uncontrolled channel.
- Clone or unlicensed production. A functionally similar die made by a different factory. X-ray, curve tracing and functional test all matter here.
- Empty or non-functional. The crudest and the easiest to detect, and still shipped.
Practical incoming inspection strategy
- Buy from a source that will put its traceability in writing. Everything downstream depends on this.
- Apply level 2 visual inspection to 100% of lots at the goods-in stage. It is cheap and it catches the majority of re-marked material.
- Apply level 3 X-ray and level 6 curve tracing to a sample from each lot of critical parts: power modules, memory, and any safety-related device.
- Reserve level 5 decapsulation for disputes, for a new supplier's first shipment, and for lots where an earlier level gave an ambiguous result.
- Record everything: photographs of the sample, the date code, the lot, the supplier, and the test result. A documented rejection is the only kind that changes supplier behaviour.
- Run level 7 functional test at rated load for a sample when the failure consequence is severe. It is the only level that tests the part in the conditions it will actually see.
No inspection programme makes a bad supplier good. The highest return on effort comes from level 1: buying from someone who can prove where the parts came from.
How we can help
If you need to verify a lot you have already received, send us the part number, the markings, photographs of the top and the leads, and the date codes. We will tell you what does not look right and what the markings should be.
If you are trying to avoid the problem rather than solve it, send us the bill of materials with the critical part numbers and the annual volumes. We will tell you which items carry the highest counterfeit and obsolescence risk, and what the traceability of our supply looks like for each one.
