Walsin WCI Multilayer Inductors: 720 Parts Across Six Sizes

The WCI series from Walsin Technology (Walsin) is a 720-part multilayer chip inductor family
spanning six case sizes, 1005(0402) to 4532(1812), and an inductance range of 1.0 nH to
15,000 nH. Q min is not a simple function of case size: it climbs from 15–25 at the smallest
size to a peak of 80 at 2012(0805), then falls back to 15–65 at the physically larger
2520(1008) size, because 2520(1008) also carries WCI’s highest inductance values, and Q within
any one case falls as inductance rises.

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

What is the Walsin WCI series and how big is it?

WCI is Walsin’s second-largest inductor series by part count, 720 parts behind only WLCW’s
791. It is multilayer construction, built across six case sizes:

The 2520(1008) size is the only one with two distinct published thickness values, 2.02 mm and
2.10 mm, within the same case code.

How does Q min change across the WCI range?

It generally rises with case size, but not smoothly. Average Q min by size runs 20.9 at
1005(0402), 29.3 at 1608(0603), 48.8 at 2012(0805), then drops to 42.7 at 2520(1008) before
climbing again to 53.8 at 3225(1210) and 73.0 at 4532(1812). The dip at 2520(1008) is the one
genuinely nowhere-else fact in this family: the physically larger case does not mean a higher
Q at that step.

Why does Q min fall at 2520(1008) even though the case is larger?

Because inductance, not case size, is the stronger driver of Q within the WCI series. Within
2520(1008) alone, Q min starts at 50 for a 10.0 nH part, rises to a peak of 65 around
47–68 nH, then falls steadily to 15 by the time inductance reaches 10,000–15,000 nH. The same
pattern holds inside every other WCI case size: Q rises through a low-to-mid inductance band
and falls again as inductance approaches that size’s ceiling.

So comparing Q min across case sizes without controlling for inductance is comparing two
different things. A fair comparison holds inductance roughly constant: at 10 nH, 2012(0805)
publishes Q min 60 while 2520(1008) publishes Q min 50 for the same nominal inductance — the
larger case is not automatically the higher-Q choice even at matched inductance.

What does self-resonant frequency look like across WCI’s six sizes?

SRF(min) falls as case size and inductance increase, which is the expected direction, but the
numeric scale the column uses changes by size in a way that is not documented:

The 1005(0402) range (1.16–12.9) reads like GHz; the other five sizes read in the hundreds to
thousands, which reads like MHz. We have not confirmed this with Walsin. For the full
measurement of this pattern across every inductor series, see
self-resonant frequency in Walsin inductors, and for
how it plays out specifically between WCI’s wirewound siblings, see
WLCW vs WQCW wirewound inductor families.

Which WCI case size should I start from?

Start from your inductance target, then check which case size reaches it with headroom to
spare rather than at its ceiling, because Q min falls as a part approaches the top of its
case’s inductance range. For anything under 120 nH, 1005(0402) is viable; between 120 nH and
1,000 nH, 2012(0805) carries the highest Q in the family; above 1,000 nH, only 2520(1008),
3225(1210) or 4532(1812) reach far enough, and Q min falls accordingly.

For the construction trade-off against wirewound inductors generally, see
multilayer vs wirewound chip inductors. The
full range is on the Walsin inductor range page.

The short version

WCI is 720 real parts across six sizes and 1.0–15,000 nH. Q min peaks at 2012(0805), not at
the largest case, because Q tracks inductance within a case more than it tracks case size
itself. SRF(min) is not in consistent units across sizes, and the 1005(0402) scale looks
different from the other five.

Send us your inductance and Q target and we will tell you which WCI case size actually
delivers it, with the real part number and what we cannot yet confirm from a datasheet.

Faster than an email. The cross-reference tool takes a pasted list or a spreadsheet and returns Walsin inductor candidates field by field, differences included. Ready stock shows what is physically in Hong Kong, so you can see straight away whether a line is a stock pull or a production slot.

Frequently asked questions