Counterfeit passive components enter a build through unauthorised channels, where a reel
can be relabelled, refilled or split without any record of the factory lot it came from.
Authorised sourcing closes that gap because every reel arrives in sealed manufacturer
packaging carrying a lot and date code the distributor can trace. Traceability, not
inspection, is the defence.
How do counterfeit passive components get into a build?
Through a channel with no record of origin. A part passes through several holders, each
adding margin and none holding a factory lot record. Somewhere in that chain a reel is
relabelled, topped up with unbranded parts, or a lower-specification part is marked as a
higher one. The BOM line is filled, and the paperwork says nothing about origin.
Passives are attractive to counterfeiters for an unhelpful reason: they are cheap, ordered
in very large quantities, and almost never tested individually. A 0201 capacitor is 0.6 mm
long. Nobody sections one. The failure shows up as a field return eighteen months later, and
by then the reel is gone.
The pressure that opens the channel is almost always schedule. A line is down, an authorised
distributor quotes a lead time, and somebody finds the part somewhere else at a price that
looks like luck. That decision is where counterfeit risk actually enters — not at a factory,
and not at a customs desk.
What does a repacked or broken reel look like?
Look for a reel that has been opened. Signs include a resealed moisture barrier bag, a label
printed on ordinary paper and stuck over another, a quantity that is not a standard reel
count, tape splices mid-reel, mixed leader lengths, and a date code that is handwritten or
absent. Any one of these is a question, not a verdict.
Split quantities deserve particular attention. Manufacturers pack in standard reel
quantities. A quantity that sits between two standard counts means somebody opened the reel
and counted parts out, which may be entirely legitimate — many buyers ask for it — but it
also means the packaging is no longer the manufacturer’s seal.
| Arrival check | What a factory-sealed reel shows | What a repacked reel often shows |
|---|---|---|
| Moisture barrier bag | Sealed, unopened, manufacturer-printed | Resealed, taped, or absent |
| Label | Manufacturer label, machine-printed | Overlabel, handwritten, or a second label under the first |
| Quantity | A standard reel count | An arbitrary count |
| Tape | Continuous, single leader | Splices, multiple leaders, uneven pockets |
| Date code | Printed on the reel label | Missing, handwritten, or inconsistent across a delivery |
| Documentation | Lot and date code on the paperwork | Part number and quantity only |
Why do lot and date codes stop this?
Because they make the reel answerable to a factory record. A lot code identifies the
production batch. A date code identifies when that batch was made. Together they let the
manufacturer confirm the batch existed and let a distributor state, on the record, which
batch shipped to you. A reel with no codes cannot be traced backwards at all.
This is why the codes matter far more than any visual check. Every visual sign in the table
above can be faked by a competent counterfeiter with a label printer. A lot code cannot be
faked into a manufacturer’s own production records. Traceability is the only test that
reaches outside the box in front of you.
Venatech Limited, an authorised Walsin Technology (Walsin) distributor in Hong Kong, records date codes against
stock lines in its internal snapshot. As at 23 September 2026 that snapshot covered 1,125
distinct part numbers, and 683 of those lines carried a recorded date code while 442 did
not. The gap is a recording gap in the internal file, and it is discussed in full in
Certificate of Conformity, lot codes and date codes.
Unique to Venatech’s data. 683 of the 1,125 stock lines in the 23 September 2026
snapshot carry a recorded date code and 442 do not, and the split is not random: every line
held wholly or partly at one of two stock locations carries a date code, and every line held
solely at the other carries none. 89 of the 683 lines carry more than one date code —
65 carry two, 19 carry three and 5 carry four — because a single stock line can be built
from up to four separate factory lots.
Can any distributor prove it has never shipped a counterfeit?
No, and a page that claims it should be read carefully. Proving a negative across every reel
ever shipped is not possible. What a distributor can do is describe the channel it buys
through, show the records it keeps, and produce a lot and date code on request. Those are
testable. “We have never had one” is not.
Venatech holds no data supporting or contradicting a claim of that kind, and will not make
one. What is stated, and is checkable, is narrower: authorised distribution only, sourced
directly from the manufacturer, original manufacturer packaging, full lot and date code
traceability, and a Certificate of Conformity available on request.
What can you actually check when the reel arrives?
Four things, in ten minutes, with no test equipment. Compare the marked part number against
the datasheet character by character. Measure the body dimensions against the datasheet
tolerances. Check the quantity against a standard reel count. Check that the lot and date
code on the reel matches the paperwork.
Dimensional checks are more useful than they sound, because case size and thickness are the
two fields a relabelled part cannot hide. The table below takes five real Walsin parts from
Venatech’s 23 September 2026 snapshot and shows which fields you can check on arrival
against Walsin’s own published data, and which you cannot.
| Order code held | Walsin published specification | Field checkable on arrival? | Match / mismatch |
|---|---|---|---|
0201B101K160CT |
0201, X7R, 100 pF, ±10%, 16 Vdc, 0.60 × 0.30 × 0.30 mm | Dimensions yes, capacitance yes, voltage no | Mismatch — rated voltage is not measurable on arrival |
0805N101J201CT |
0805, NP0, 100 pF, ±5%, 200 Vdc, 2.00 × 1.25 × 0.60 mm | Dimensions yes, capacitance yes, voltage no | Mismatch — same limitation at 200 Vdc |
HH03N0R4B500CT |
0201, NP0, 0.4 pF, ±0.1 pF, 50 Vdc, 0.60 × 0.30 × 0.30 mm | Dimensions yes, 0.4 pF measurement needs an RF fixture | Mismatch — capacitance not checkable with a handheld meter |
S242B102K502CT |
1808, X7R, 1000 pF, ±10%, 5000 Vdc, 4.50 +0.80/−0.30 × 2.00 × 2.00 mm | Dimensions yes, safety approval marking yes | Match — the largest body and the easiest to verify visually |
WR02X1002FAL |
0201 (0603), 10 kΩ, ±1%, 1/20 W, 7″ reel, 15,000 pcs | Resistance yes, reel quantity yes | Match — both checkable, quantity is declared by Walsin |
Capacitance and resistance are measurable. Rated voltage, rated power and dielectric class
are not, without destroying parts. That is the honest limit of incoming inspection on
passives, and it is the reason the channel matters more than the inspection.
Can I verify the reel quantity against the manufacturer’s data?
Rarely, from parametric data alone. Walsin’s chip resistor export carries a Packaging
column, but it states a numeric reel quantity on only a small minority of rows. Walsin’s
MLCC export declares SPQ and Packing columns and leaves both empty on every row. Reel
quantity has to come from the packaging specification or the Certificate of Conformity.
| Data source | Rows held | Reel quantity stated | Match / mismatch |
|---|---|---|---|
| Walsin MLCC parametric export | 24,026 | 0 — SPQ and Packing empty on every row |
Mismatch — column declared, never populated |
| Walsin chip resistor export, lines we stock | 250 of 255 resolved | 4 state a numeric reel count | Mismatch — 246 give a reel type but no count |
| Those 4 lines vs Venatech’s own SPQ | 4 | 15,000 pcs on all four | Match — Walsin’s figure and ours agree exactly |
| Venatech snapshot, all product lines | 1,125 | 501 lines carry an SPQ figure | Mismatch — 624 lines carry none |
Unique to Venatech’s data. Walsin’s MLCC parametric export declares an
SPQcolumn and
aPackingcolumn and populates neither on any of its 24,026 rows. On the resistor side,
of the 255 chip resistor and resistor array lines in Venatech’s snapshot, 250 resolve
against Walsin’s export and only 4 of those carry a stated reel quantity —WR02X1002FAL,
WR02X1241FAL,WR02X2400FALandWR02X4700FAL, all declared as 7″ reel taping,
15,000 pcs, and all four agreeing with Venatech’s own SPQ figure.
Does a part number that fails on the manufacturer’s site mean it is fake?
No. Manufacturer search tools and manufacturer order codes are different strings, and the
mismatch is common enough to be useless as a test. Packaging suffixes get dropped from
exports, and embedded spaces break a copy-paste. Real, orderable parts routinely return zero
results on the brand’s own site.
Two measured examples from the same snapshot. The orderable code WR04X101JTL appears in
Walsin’s chip resistor export as WR04X101 JTL, with a space. The orderable code
0201B101K160CT appears in the MLCC export as 0201B101K160, without the packaging suffix.
Both parts are genuine; both fail a naive search. Full detail is in
What “authorised distributor” means, and how to verify one.
What should you do if you suspect a counterfeit?
Stop the reel, do not return it, and do not scrap it. Photograph the packaging, the label and
the tape before anything is opened further. Quarantine the whole delivery, including reels
already partly consumed. Then go back to the supplier with the lot and date code and ask for
the CoC and the source of that specific lot.
Returning the reel destroys the evidence and ends the investigation. Scrapping it does the
same. If the supplier cannot name where a lot came from, that is the finding, and it applies
to every other line bought through the same channel — which is usually the more expensive
problem.
FAQ
Are counterfeit capacitors and resistors really a problem?
Yes, because passives are ordered in enormous quantities, cost very little each, and are almost never tested individually. That combination makes relabelling and reel refilling worthwhile. The failure typically appears as a field return long after the reel has been consumed, which is why channel control matters more than inspection.
How does authorised sourcing stop counterfeits?
It removes the step where a reel changes hands without a record. An authorised distributor buys from the manufacturer under agreement, receives sealed factory packaging, and can state which lot and date code shipped. That does not make inspection unnecessary. It makes the reel answerable to a factory production record.
What is the difference between a lot code and a date code?
A lot code identifies the production batch a part came from. A date code identifies when that batch was made. The lot code is what lets a manufacturer confirm a batch existed; the date code is what lets you judge shelf life and storage age. A traceable reel carries both.
Can I tell a counterfeit passive component by looking at it?
Sometimes, and never reliably. Resealed bags, overlabels, tape splices, non-standard quantities and missing date codes are all worth a question. All of them can also be produced by legitimate repacking. And a competent counterfeiter can reproduce every visual cue, which is why traceability beats inspection.
Can a distributor prove it has never shipped a counterfeit part?
No. Proving a negative across every reel ever shipped is not possible, and a supplier claiming it is asking to be believed rather than checked. What can be checked is the channel it buys through, the records it keeps, and whether a lot and date code and a Certificate of Conformity arrive when you ask.
What should I check when a reel of capacitors arrives?
Compare the marked part number to the datasheet character by character, measure the body against the datasheet dimensions, check the quantity against a standard reel count, and confirm the lot and date code on the reel matches the paperwork. Capacitance is measurable; rated voltage is not.
Is grey market stock the same as counterfeit stock?
No. Grey market means genuine parts sold outside the manufacturer’s authorised channel, often legitimately. The problem is that the same channel carries no factory lot record, so a counterfeit reel and a genuine excess reel arrive looking identical. The risk is the missing traceability, not the label.
What should I do with a reel I think is counterfeit?
Quarantine it and do not return or scrap it — that destroys the evidence. Photograph the packaging, label and tape before opening further, hold the whole delivery including partly used reels, then ask the supplier for the Certificate of Conformity and the source of that specific lot.
Next step
Ask for the lot and date code before the order, not after the failure. Send a BOM line and
Venatech Limited, an authorised Walsin distributor in Hong Kong, will return the Walsin
datasheet, the orderable order code, whether the current snapshot carries a recorded date
code for that line, and a Certificate of Conformity on request.
Send a BOM line to Venatech · Browse the
Walsin chip resistor range · Read
MLCC shelf life, storage and handling and
The CT suffix: orderable Walsin part numbers.
Cross it yourself. The cross-reference tool takes a single part number or a whole BOM column and returns the Walsin candidates with every field that differs stated plainly — qualification stays with you. Ready stock shows what is held in Hong Kong today, with an RFQ against any line.