Choosing an RF Matching Inductor: The High-Q, Tight-Tolerance Subset

An RF matching inductor needs a predictable value and low loss at the match frequency — in
practice, Q min of 30 or higher and a tolerance of ±5% or tighter. Measured against the full
inductor export published by Walsin Technology (Walsin), 1,321 of 5,410 parts (24.4%) meet both
conditions together. They concentrate in five case sizes and six series; the rest of the
catalogue — three-quarters of it — is tolerance-loose, low-Q, or both, and is not a safe pull
for a matching network without checking the row.

Venatech Limited, an authorised Walsin distributor in Hong Kong, holds Walsin’s full inductor
parametric export — 5,411 rows, one of which (Test123999) is a QA test row excluded from every
count below. The real total is 5,410 parts. Every part number named in this post is real and
checked against that extract.

What makes an inductor suitable for an RF matching network?

Two things the parametric export actually states: a high minimum Q at the operating frequency,
because loss in the matching element burns signal you are trying to preserve, and a tight
inductance tolerance, because a matching network is tuned to a specific value and a loose part
shifts the match point. A ±20% part can land anywhere across a 40% inductance spread; a ±5% part
cannot drift past 10%. This post treats Q min ≥ 30 and tolerance ≤ ±5% as the floor for “matching
grade,” and measures exactly how much of the catalogue clears it.

How many Walsin inductors meet a high-Q, tight-tolerance filter?

1,321 of 5,410 — 24.4%. That is every part with Q Min at 30 or above and a tolerance of ±2%,
±3% or ±5%. The other 4,089 fail on at least one condition: either the tolerance is ±10% or
looser, or Q Min is below 30, or both.

Tightening the tolerance alone or raising Q alone each clears roughly half the catalogue; asking
for both at once halves that again, because the two conditions do not track each other — a part
can be tight-tolerance and low-Q, or loose-tolerance and high-Q, with no correlation you can
assume without checking both fields.

Which series and sizes carry the matching-network subset?

Six series hold all 1,321 parts, and the subset concentrates hard in five standard case sizes:

No part from WLCM, MCI, WLBD, any bead series or any automotive series appears in this
subset at all — those lines either run looser tolerances, lower Q, or do not publish Q Min in a
way that clears 30.

What does a matching-grade part look like next to a general-purpose part?

Real parts at two case sizes, matching-grade against general-purpose:

Four real, in-catalogue parts. Three clear the matching-grade filter at their respective case
sizes; the WLFI part is a general-purpose or power-filtering part whose actual value could sit
20% away from nominal with roughly a third of the WLCW part’s Q at the same footprint.

Does a tight tolerance guarantee a usable Q?

No — this is exactly why the filter needs both fields, not one. Across the full catalogue,
2,572 parts carry ±5% or tighter tolerance, but only 1,321 of those also clear Q Min 30. The
other 1,251 tight-tolerance parts have a lower Q Min and are not a safe pull for a matching
network even though their tolerance alone looks right on a parametric search. The reverse also
holds: of the 2,628 parts with Q Min ≥ 30, 1,307 carry a tolerance looser than ±5%.

How do I shortlist a part for a specific matching network?

Start from the 1,321-part subset above, then narrow by case size and target inductance. At
2012(0805), for example, 334 parts clear the filter — specify your target value and tolerance
and we can return the exact real part numbers rather than a series name. For the broader
question of where inductance sits versus impedance in Walsin’s export, see
ferrite bead vs inductor: reading Walsin’s impedance (100MHz) column.
For how these same prefixes decode, see
AIP, MIP, WIP and 33 more. Browse the full
Walsin inductor range or send your target frequency and inductance and we
will shortlist real part numbers.

The short version

1,321 of 5,410 Walsin inductors (24.4%) meet a Q Min ≥ 30 and tolerance ≤ ±5% floor for RF
matching work, concentrated in six series and five standard case sizes, topped by 2520(1008) at
372 parts. Tolerance and Q do not move together — checking only one field will pass parts that
fail the other.

Give us your target frequency, inductance and case size and we will return real Walsin part
numbers that clear both the tolerance and Q thresholds, not just one.

Frequently asked questions

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.