Ferrite Bead Selection: 641 of Walsin’s 5,410 Inductor Rows Are Not Inductors

Ferrite bead selection starts by knowing a bead is not an inductor. We parsed all 5,410 real rows of Walsin’s chip inductor export and found 641 carry an impedance in ohms, not an inductance in henries. They span 19 of the 47 series. Sort the file by “Inductance” and you mix three physically incompatible quantities in one column.

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Venatech Limited, an authorised Walsin distributor in Hong Kong, holds all of Walsin Technology (Walsin)’s parametric export files, including Walsin_Inductor_ALL.xlsx. The file ships 5,411 rows; one, Test123999, is a QA test record with the literal text “TEST Saturation current 123.88” in a numeric cell, so we excluded it and worked from the real total of 5,410. Every count and every part number below came out of that file, and we say so before you read a single figure.

How many of Walsin’s 5,410 inductor rows are actually ferrite beads?

641 of them. We read the Unit column across every row rather than trusting the Inductance header: 4,125 rows are nanohenries, 644 are microhenries, and 641 read Ω — ohms, an impedance, not an inductance at all. Those 641 are ferrite beads. Walsin files them in the same export, under the same “Inductance” header, as every genuine power and RF inductor in the catalogue.

What the row is	Unit in the Unit column	Rows	Share of 5,410
Genuine inductor	nH	4,125	76.2%
Genuine inductor	µH	644	11.9%
Ferrite bead	Ω	641	11.9%

A bead’s whole job is to present impedance to high-frequency noise while looking like a short circuit at DC. An inductor’s job is to store energy at a design frequency. They are not interchangeable, and the export does not say which is which anywhere in the part number — only the Unit column tells you, and most BOM tools do not read it.

Which 19 series carry a bead, and what case sizes do they use?

Nineteen of Walsin’s 47 inductor series, and the case-size mix is heavily skewed to two sizes. We grouped all 641 Ω-unit rows by Series and by Size: BIH, HCM, MCB / MHC Automotive, MCB-B, MCB-H, MCB-S, MCM, MHC-P, MHC-S, MPA, SCA, SCM, WLBD, WLBD(HC), WLPN, WQBD, WQCF, WTBL and WTCF. Every one of those 19 is bead-only in this export — none of the 641 rows mixes with a genuine inductor’s nH or µH value inside the same series.

Case size	Bead rows	Share of 641
1608 (0603)	177	27.6%
2012 (0805), written 2012(0805)	177	27.6%
1005 (0402)	90	14.0%
3216 (1206)	72	11.2%
2012, written as the bare integer 2012	45	7.0%
4516 (1806)	22	3.4%
4532 (1812)	22	3.4%
3225 (1210)	15	2.3%
1012, 2520 (1008), 2016 (0806), 3216, 2.0*2.0	21 combined	3.3%

0603 and 0805 alone account for 354 of 641 rows — 55.2% of the whole bead shelf. We have not seen this case-size breakdown counted anywhere. It matters for selection because a bead’s self-resonant behaviour and current rating move with case size, and over half the catalogue’s beads sit in the two sizes a board-space-constrained design is most likely to want anyway.

Why does sorting the Inductance column mix three incompatible quantities?

Because the column header says “Inductance” on every one of the 5,410 rows, and the unit lives in a separate cell. A row printing “600” is 600 nH, 600 µH or 600 Ω depending entirely on what the Unit cell next to it says — and the ratio between the smallest and largest reading of “600” under those three units is six orders of magnitude. Sort or filter on the numeric value alone and a 600 Ω bead lands in the same bucket as a 600 nH RF inductor.

A second, smaller version of the same problem sits in the Size column. Of the 641 bead rows, 45 store the 2012 case code as a bare number — Python reads it as an integer, not text — against 177 that store it as the string 2012(0805). Catalogue-wide, only 47 rows anywhere in the 5,410-row file use the bare-integer form, and 45 of those 47 (95.7%) are bead rows. A find-and-match on the text string 2012(0805) silently drops the bare-integer beads, and a numeric filter on Size silently drops everything else.

Does Walsin publish an impedance figure for every bead row?

No — 609 of 641. We checked the Impedance (100MHz) column across the whole 641-row bead population and found a non-zero reading on 609 of them, 95.0%. The other 32 beads read a literal 0 in that column with no value recorded anywhere else in the row. Catalogue-wide, only one row outside the bead population carries a non-zero figure there at all, and that single exception is the Test123999 test record, which we have already excluded from every real count.

Field	Populated / non-zero on bead rows	Share of 641
Unit = Ω (identifies it as a bead)	641	100%
RDC (DC resistance)	634 in the standard Ω notation	98.9%
Rated current, with a unit	611	95.3%
Impedance at 100 MHz	609	95.0%
Q Min	0	0%

Q Min reads zero on all 641 bead rows, with no exception. That is not missing data in the usual sense — Q is not a meaningful figure for a component designed to be lossy at RF, so a zero here is arguably correct. But a buyer filtering the whole inductor export for “Q above zero” to exclude junk rows will silently exclude every real bead in the catalogue instead.

Hold one requirement steady — 2012 (0805), 30 Ω at 100 MHz, 1 A rated, ≤ 0.05 Ω RDC — and the export returns three candidates, not one, and none matches on every field:

Part number	Series	Impedance (100 MHz)	RDC	Rated current	Match / mismatch vs 2012(0805), 30 Ω, 1 A, ≤0.05 Ω
MHC2012S300RZP	MCB / MHC Automotive	30 Ω	0.014 Ω	3300 mA	Match on case and impedance; mismatch — RDC and rated current both exceed the requirement, in the buyer’s favour
MCB2012S300KBP	MCB-S	30 Ω	0.05 Ω	800 mA	Match on case, impedance and RDC; mismatch — rated current is below 1 A
MHC2012S300QBP	MHC-S	30 Ω	0.04 Ω	3000 mA	Match on case, impedance and RDC margin; mismatch — no AEC-Q200 or automotive marker exists in the export to say whether this one is interchangeable with the automotive row above

We will not tell you any of the three is equivalent. The case size and the 100 MHz impedance match on all three; RDC and rated current do not, and the column that would tell you whether the automotive row is a qualified part sitting next to two commercial ones simply does not exist in this file.

What case sizes dominate the bead population, and what does that tell a buyer?

0603 and 0805 together hold 354 of the 641 rows, and the automotive-marked series concentrate there too. We measured the non-automotive beads (491 rows across the other 18 series) against the single automotive series MCB / MHC Automotive (150 rows) separately: the automotive series publishes a non-zero 100 MHz impedance on 150 of 150 rows, 100%, while the remaining 491 non-automotive beads publish one on 459, 93.5%. The automotive line is the more completely specified half of the bead catalogue by this measure, even though it is not AEC-Q200 marked anywhere in the export — there is no qualification column in this file for any series, automotive or not.

Where does the RDC column break its own unit convention?

On 7 of 641 rows. Every other bead row writes DC resistance as a decimal followed by the Ω symbol — 0.09Ω, 0.014Ω and so on. Two rows instead write a milliohm figure with its own symbol (WLBD1608HCU700TL reads 22mΩ, as does MHC1608P700Z06BP3A5), and five WLPN rows (WLPN202012N1R0PB, WLPN202012N1R5PB, WLPN202012M2R2PB, WLPN202012M3R3PB, WLPN202012M4R7PB) write a bare decimal — 0.07, 0.09, 0.107, 0.19, 0.241 — with no unit symbol of any kind. We read the bare figures as ohms because they sit in the expected numeric range for this case size, but that is our inference, not Walsin’s statement.

What should an engineer do before filtering Walsin’s inductor export by inductance?

Read the Unit column first, on every row, before touching the Inductance column at all. If it reads Ω, you are looking at a bead and the “inductance” figure is not one. If it reads nH or µH, confirm the Size column is text rather than a bare integer before you join it against anything else. Then check whether Impedance (100MHz) is populated — 95.0% of bead rows carry a real figure, but the 32 that read zero need a different source before you can select on impedance at all.

1. Decide bead or inductor before you open a BOM line. The Unit column is the only place this is stated.
2. Cross the part on our free cross reference tool. Paste up to 500 part numbers or drop an Excel or CSV, and it decodes 18 manufacturers’ part numbers against 800,000+ crossable Walsin part numbers, field by field, with every difference stated rather than hidden.
3. Check what is physically in Hong Kong on ready stock, a dated snapshot as at 23 September 2026, before committing to a case size.
4. Ask us for the datasheet. We hold 28 Walsin datasheets, 451 pages — 26 MLCC and 2 chip resistor — and none of them covers an inductor or bead series. We will tell you plainly when a figure is export-only.

For how rated current and saturation current diverge on the inductor side of this same file, see Rated current vs saturation current in chip inductors. For how to tell Walsin’s 47 inductor series apart before you even reach the bead question, see Walsin inductor series: how to tell them apart. The full range is on the Walsin inductor range page.

The short version

A ferrite bead and an inductor sit in the same Walsin export file under the same column header, and the only thing that tells them apart is a one-character entry in the Unit column. 641 of 5,410 real inductor rows read Ω rather than nH or µH, across 19 of the 47 series, and 0603 and 0805 alone carry 354 of them. Sorting or filtering on “Inductance” without reading Unit first mixes nanohenries, microhenries and ohms in one numeric list — three quantities that cannot be compared. We hold no inductor or bead datasheet for any of the 47 series, so the export is the whole of the published evidence, and we say so rather than quoting a mechanism we have not seen.

Send us the bead or inductor rows off your BOM with each line marked as noise suppression or energy storage, and we will come back with Walsin candidates field by field, blanks included, checked against what was physically in Hong Kong on 23 September 2026.

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Frequently asked questions

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