Shielded vs Unshielded Chip Inductors: What Walsin’s Data Can and Cannot Tell You

Walsin Technology (Walsin)’s own parametric export carries no shielded or unshielded
construction field, so a shielded-vs-unshielded split cannot be verified from the data
Venatech holds. What the export does carry is real, checkable size and rated-current
data across all 5,410 parts, and running that comparison turned up a genuine defect:
30 of 44 WLFI Series rows publish a rated current that is physically implausible for the
package it is printed against.

Venatech Limited, an authorised Walsin distributor in Hong Kong, holds Walsin’s full
5,410-row inductor parametric export. Venatech holds no Walsin inductor datasheet PDF, and
208 parts across the VEFL, WIP, SCM, SCA and BIH series have no datasheet at all — so
construction details that would normally sit in a datasheet drawing are not available to
us for any series. Every number below comes from the export itself. Every part number is
real.

Does Walsin’s inductor data tell you which parts are shielded?

No. The export has 14 columns — Part Number, Series, Size, Size L*W (mm), Thickness (mm),
Inductance, Impedance (100MHz[Ω]), Unit, Tolerance, Q Min, SRF(min), RDC, Rated Current and
Saturation Current. None of them records winding type, core material or shielding. No
series name in the 47-series list contains the word “shielded” or “open” either. If your
supplier’s cross-reference tool claims a Walsin series is shielded, that claim is not
coming from anything in the file Venatech holds, and we cannot confirm it from our data.

If construction is not in the data, what can you actually check?

The relationship between package size and rated current — which is the practical reason
engineers care about shielding in the first place, since an unshielded open-core design
can pack more current into a smaller footprint at the cost of radiated flux, while a
shielded design trades some current density for a cleaner field. We cannot label which
Walsin series uses which construction, but we can measure whether size reliably predicts
current capacity across the parts we hold. It does not.

Does a bigger package always mean more rated current?

No, and the spread at a single inductance value is wide. At 2.2 µH, a common value across
several Walsin inductor families, rated current ranges from 0.365 A to 10.4 A depending on
series, and the largest footprint is not always the highest current:

The 2.0×1.25 mm row is the one worth stopping on. MIP and MIP-P parts at that footprint are
rated 0.6–0.7 A, which fits the general size trend. WLFI parts at the identical footprint
and identical 2.2 µH inductance are exported at 30 A. That is not a construction
difference an engineer could design around — it is 50 times the current in the same
package, which is not physically plausible for any winding type.

What did checking the size-vs-current trade-off turn up?

A real defect in the WLFI Series Rated Current column. 30 of its 44 parts carry a current
figure in whole amps — not milliamps — that implies more power dissipation than the
package could survive:

A 1.6×0.8 mm or 2.0×1.25 mm chip inductor dissipating hundreds to thousands of watts
through its own winding resistance is not physically possible — that is motor-starter
territory in a component smaller than a grain of rice. The last row above, from the same
series, shows the pattern breaks cleanly at the lower inductance values: WLFI2012Z0M47NTB
reads a plausible 300 mA. The 30 affected rows sit at 1.0 µH and above in the 1608 size and
at 1.0 µH and above in the 2012 size; the 14 rows below that threshold all read in
milliamps. The most likely explanation is a dropped “m” — 50 A should probably read 50 mA —
but Venatech has not confirmed this with Walsin.

How should I choose between a shielded-type and open-type inductor?

Ask Walsin or request the datasheet for the specific part number, since the construction
answer is not recoverable from the parametric data Venatech holds. What you can do with the
export today is compare real rated-current figures at your target inductance and footprint
across several series — as the table above shows, two series at the same size and
inductance can differ by a wide margin for reasons the data alone will not explain, and at
least one of those differences, in the WLFI case, turned out to be a data defect rather
than a real design difference. Confirm any outlier before you specify it.

For how Walsin’s wirewound and multilayer inductor families differ in general, see
Multilayer vs wirewound chip inductors. For
the smallest case sizes in the catalogue, see
The smallest Walsin inductors: 0201 and 0402.
The full range is on the Walsin inductor page.

The short version

Walsin’s inductor export cannot answer a shielded-vs-unshielded question — the field does
not exist. What it can do is show that package size is an unreliable proxy for current
capacity, with spreads up to 50x at an identical size and inductance. In the WLFI Series,
that spread traces to an exported rated-current figure that is physically implausible on
30 of 44 parts. Confirm construction and current rating directly with Walsin before
relying on either.

Send us your target size and current, and we will tell you which real Walsin part
numbers match it and flag anything in the data that does not hold up.

Check it against the catalogue yourself. Cross-reference accepts one part number or a whole BOM column and prints the mismatches as plainly as the matches — qualification stays with you, which is the honest division of labour. Ready stock covers the inductor lines held in Hong Kong.

Frequently asked questions