Feed-Through and 3-Terminal MLCC for EMI Suppression: How to Use the Walsin FT Series

A 3-terminal feed-through MLCC carries the signal or supply through the part between two
in-line terminals, with a third wide terminal returning to ground. Walsin Technology
(Walsin) builds this as the FT series. Venatech holds eight FT part numbers: one 0402 X5R
and seven 0805 X7R. Walsin’s MLCC application guide publishes no three-pad land pattern for
any of them.

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What is a 3-terminal feed-through capacitor?

It is a capacitor with the current path and the capacitor path separated. Two terminals sit at
the ends of the long axis and carry the through current. A third, wider terminal on the side
connects the internal electrodes to ground, so noise current leaves through that terminal
rather than doubling back along the same pads.

Walsin describes the FT series as a bypass for digital and analogue signal line noise on
computer motherboards and peripherals.

Physically it is still an MLCC: same ceramic, same X7R or X5R dielectric, same Cu/Ni/Sn
termination system coded C, same reflow process. The change is geometric — a short, wide
ground return on the side of the body rather than a long path back through an end pad.

Flagged for review. The Walsin FT datasheet we hold publishes no equivalent series
inductance figure, no impedance curve and no insertion loss curve. Do not put a decibel or
nanohenry number against an FT part in customer-facing copy until Walsin supplies one.
Source:
Walsin Feed Through FT datasheet,
January 2026 revision.

Which Walsin FT parts can I actually order?

Eight, and seven of them are the same case size. Venatech Limited, an authorised Walsin
distributor in Hong Kong, holds an extract of 24,026 Walsin MLCC part numbers. FT is eight of
those rows, the smallest series in the catalogue.

Part number	Size	Dielectric	Capacitance	Tolerance	Rated voltage	L × W × T (mm)
FT21B103M500	0805	X7R	10 nF	±20%	50 Vdc	2.00 ±0.20 · 1.25 ±0.10 · 0.85 ±0.10
FT21B223M500	0805	X7R	22 nF	±20%	50 Vdc	2.00 ±0.20 · 1.25 ±0.10 · 0.85 ±0.10
FT21B473M500	0805	X7R	47 nF	±20%	50 Vdc	2.00 ±0.20 · 1.25 ±0.10 · 0.85 ±0.10
FT21B224M160	0805	X7R	220 nF	±20%	16 Vdc	2.00 ±0.20 · 1.25 ±0.10 · 0.85 ±0.10
FT21B474M160	0805	X7R	470 nF	±20%	16 Vdc	2.00 ±0.20 · 1.25 ±0.10 · 0.85 ±0.10
FT21B474K160	0805	X7R	470 nF	±10%	16 Vdc	2.00 ±0.20 · 1.25 ±0.20 · 0.85 ±0.10
FT21B105M160	0805	X7R	1000 nF	±20%	16 Vdc	2.00 ±0.20 · 1.25 ±0.10 · 0.85 ±0.10
FT15X435M4R0	0402	X5R	4300 nF	±20%	4 Vdc	1.00 ±0.10 · 0.50 ±0.20 · 0.4 ±0.10

Every one of those eight returns a row in Walsin’s own parametric export. Only two rated
voltages sit above 4 V, 16 V and 50 V, and there is exactly one 0402 part.

Note FT21B474K160. It is the only ±10% part in the series, and the FT datasheet’s
capacitance range table footnotes the tolerance as “M” only, meaning ±20%. The export
contradicts the footnote, and the part carries a wider width tolerance, ±0.20 mm against
±0.10 mm.

Flagged for review. FT21B474K160 is listed at ±10% in Walsin’s parametric export
while the FT datasheet footnote states the FT tolerance is ±20% only. Confirm the tolerance
and the ±0.20 mm width tolerance with Walsin before releasing a drawing against this part.

How do I lay out a 3-terminal 0805?

Not from Walsin’s application guide, because it does not publish a three-pad footprint at any
case size. The guide’s reflow soldering table gives two-pad footprints for seventeen case
sizes, and every one of the seventeen assumes two terminations on the ends of the body.

The 0805 reflow footprint published is A = 2.80 mm overall pad span, B = 1.00 mm
pad length, C = 0.90 mm gap, D = 1.30 mm pad width, E = 0.40 mm, F = 3.05 mm, G = 1.85 mm,
with a placement accuracy of ±0.25 mm. That is the starting geometry for the two through pads
and nothing for the third.

What you need for an FT21 part	What Walsin publishes	Match / mismatch
Two through-terminal pads, 0805 outline	0805 reflow footprint, A 2.80 · B 1.00 · C 0.90 · D 1.30 mm	match — use as the starting geometry
Third ground pad position and size	nothing at any case size	mismatch — no three-pad land pattern published
Terminal geometry to lay the pad against	FT datasheet dimensions e, g, i and j per size	match — dimensions given, footprint not derived
Placement accuracy for a 3-terminal part	±0.25 mm for a 2-terminal 0805	mismatch — not stated for FT
Wave soldering option	FT datasheet states reflow only	mismatch — no wave process available

Unique to Venatech’s data. Walsin lists only eight feed-through parts in its entire
MLCC catalogue, and the MLCC application guide publishes no three-pad land pattern for any
of them. The guide’s reflow footprint table covers seventeen case sizes, all two-terminal,
including 0508 and 0612 footprints for which Walsin’s parametric search returns zero MLCC
parts. Measured from our extract of Walsin’s own published data.

The datasheet does give terminal geometry for a pad stack. For 0805 it publishes e = 0.30 ±0.20 mm, g = 0.40 ±0.20 mm minimum, i = 0.60 ±0.20 mm and j = 0.25
±0.20 mm. For 0402: e = 0.17 ±0.10, g = 0.10 mm minimum, i = 0.35 ±0.10, j = 0.15 ±0.10 mm.

Flagged for review. Ask Venatech to obtain a recommended three-pad land pattern from
Walsin before committing a layout. Deriving one from the terminal dimensions is an
assumption, and a mis-sized ground pad is exactly the kind of solder-volume error the
application guide warns causes cracking.

Does the FT part fit where my 2-terminal capacitor was?

In outline, yes at 0805. In height and in electrical spec, check first. Every 0805 FT part is
2.00 by 1.25 mm, which is the standard 0805 outline, and 0.85 mm thick. A general purpose
0805 at the same capacitance and voltage is 0.80 mm thick. The soft-termination and some
automotive options in the same case size are 1.25 mm.

Field	FT21B103M500	0805B103K500	MT21B103K500	SH21B103K500
Series	Feed Thru FT, 3-terminal	General Purpose	Automotive MT, AEC-Q200	Soft Termination SH
Terminals	3	2	2	2
Size	0805	0805	0805	0805
Dielectric	X7R	X7R	X7R	X7R
Capacitance	10 nF	10 nF	10 nF	10 nF
Rated voltage	50 Vdc	50 Vdc	50 Vdc	50 Vdc
Tolerance	±20%	±10%	±10%	±10%
Thickness	0.85 ±0.10 mm	0.80 ±0.10 mm	0.80 ±0.10 mm	1.25 ±0.10 mm
Match / mismatch vs FT21B103M500	reference	match: size, dielectric, value, voltage · mismatch: 2 terminals, ±10%, 0.80 mm	match: size, dielectric, value, voltage · mismatch: 2 terminals, ±10%, 0.80 mm, AEC-Q200	match: size, dielectric, value, voltage · mismatch: 2 terminals, ±10%, 1.25 mm, soft termination

The electrical line item is identical across all four; everything that differs is mechanical
or qualification — an FT swap is a layout decision, not a BOM decision.

The 0402 part sits differently. FT15X435M4R0 is 4300 nF X5R at 4 Vdc and 0.4 mm thick. The
closest two-terminal 0402 X5R parts are 0402X106M4R0 at 10 µF and 0402X226M4R0 at 22 µF,
both 4 Vdc and 0.50 ±0.20 mm thick.

What current can a feed-through capacitor carry?

Two amps DC on ten of the eleven part numbers Walsin tabulates, and four amps DC on the
1 µF 0805 part. That is a real constraint a two-terminal capacitor does not have, because in
an FT part the supply current physically passes through the component.

Rated value from the FT datasheet	Figure
Rated current, most FT parts	2 A DC
Rated current, FT21B105M160	4 A DC
DC resistance, most FT parts	0.03 ohms max
DC resistance, FT21B105M160	0.02 ohms max
DC resistance limit after stress testing	0.05 ohms max
Insulation resistance, FT21B parts	1000 megohms min
Insulation resistance, FT15X435M4R0	25 megohms min
Withstanding voltage test	rated voltage × 300%, 1 to 5 s
Operating temperature, FT21B parts	−55 to +125 °C
Operating temperature, FT15X435M4R0	−55 to +85 °C

Figures from the
Walsin Feed Through FT datasheet,
section 6.

Two lines change a design. 0.03 ohms max at 2 A dissipates 0.12 W, and the operating range
includes self-heating. And FT15X435M4R0 stops at 85 °C, being X5R rather than X7R.

What does the FT datasheet promise, and what does it leave out?

It promises a reliability set: solderability at 240 ±3 °C, resistance to soldering heat at
270 ±5 °C for 10 ±1 seconds with capacitance change inside ±7.5%, vibration at 10 to 55 Hz
with 1.5 mm amplitude for six hours, ten temperature cycles, and 500 hours of damp heat at
40 ±2 °C and 90 to 95% RH.

The bend test is specified twice. On a 100 × 40 × 1.0 mm
glass-epoxy substrate the deflection is 2 mm held for 30 seconds. On a 100 × 40 × 0.8 mm
substrate it is 1 mm held for 5 seconds. Both require capacitance change inside ±7.5% and DC
resistance under 0.05 ohms.

It leaves out the frequency behaviour — the whole reason to choose a 3-terminal part — plus
the land pattern, any wave soldering option and any AEC-Q200 test table.

Why does the datasheet list more FT parts than Walsin’s search returns?

Because three of the tabulated part numbers do not appear in the parametric export. The FT
datasheet’s rated-value table names eleven part numbers with full rated values. Walsin’s own
parametric search returns eight of the eleven. The three absent from it are FT15B105M4R0,
FT21B103M101 and FT21B104M250.

Part number in the FT datasheet rated-value table	Returned by Walsin’s parametric search
FT15X435M4R0	yes
FT15B105M4R0	no
FT21B103M101	no
FT21B103M500	yes
FT21B223M500	yes
FT21B473M500	yes
FT21B104M250	no
FT21B224M160	yes
FT21B474K160	yes
FT21B474M160	yes
FT21B105M160	yes

Unique to Venatech’s data. Walsin’s FT datasheet tabulates eleven feed-through part
numbers with full rated values. Walsin’s parametric search returns eight. Three
datasheet-listed parts — the 0402 X7R 1 µF at 4 V, the 0805 10 nF at 100 V and the 0805
0.1 µF at 25 V — are invisible to anyone selecting from the search tool. Counted by
cross-checking the datasheet table against our extract of the export.

The 100 V part matters most. Nothing in the eight-part export reaches above 50 Vdc, so a
designer working from the search tool would conclude FT stops there.

Flagged for review. Treat FT15B105M4R0, FT21B103M101 and FT21B104M250 as
datasheet-listed but unconfirmed. Ask Walsin whether each is orderable before quoting it.
The three are not in Walsin’s parametric export and we hold no other source for them.

How do I qualify an FT part on my board?

Treat it as a new footprint, not a new value. Get the land pattern confirmed, build a coupon
with the ground pad at two sizes, and measure the attenuation you actually get rather than
relying on a published curve that does not exist in the revision we hold.

Then check four things in order. The DC current through the part against the 2 A or 4 A
rating. The DC resistance dissipation against the ambient, remembering that the operating
range includes self-heating. The height, at 0.85 mm for 0805 and 0.4 mm for the 0402 part. And
the tolerance, ±20% on seven of the eight parts. Plan for reflow only; the datasheet gives no
wave option at either size.

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FAQ

What is a 3-terminal capacitor?

A 3-terminal capacitor carries current through the part between two in-line terminals, with
a third wider terminal on the side returning the internal electrodes to ground. Separating
the through path from the ground return shortens the ground current loop compared with a
two-terminal capacitor and its via. Walsin builds this as the FT feed-through series.

How many feed-through capacitors does Walsin make?

Eight part numbers return from Walsin’s parametric search: seven 0805 X7R parts from 10 nF to
1000 nF at 16 Vdc and 50 Vdc, and one 0402 X5R part at 4300 nF and 4 Vdc. The FT datasheet
tabulates eleven, so three datasheet-listed parts are not returned by the search tool.

What land pattern does a Walsin 3-terminal MLCC use?

Walsin does not publish one. The MLCC application guide gives two-pad reflow footprints for
seventeen case sizes and no three-pad footprint at any size. The FT datasheet gives terminal
dimensions e, g, i and j per size, which is enough to derive a pad stack, but the derivation
is yours and should be confirmed with Walsin.

Can a feed-through capacitor replace my 0805 decoupling capacitor directly?

Electrically, often yes: FT21B103M500 matches 0805B103K500 on case size, X7R dielectric,
10 nF and 50 Vdc. Mechanically, no. The FT part has three terminals, needs a different land
pattern, is 0.85 mm thick against 0.80 mm, and carries ±20% tolerance against ±10%.

How much current can a Walsin FT capacitor carry?

Two amps DC on ten of the eleven part numbers Walsin tabulates, and four amps DC on the 1 µF
0805 part FT21B105M160. DC resistance is 0.03 ohms maximum, or 0.02 ohms on the 4 A part.
The datasheet notes that the stated operating temperature range includes self-heating, so
budget for the dissipation.

Does Walsin publish an insertion loss curve for the FT series?

Not in the January 2026 revision Venatech holds. That revision contains no impedance plot,
no insertion loss curve and no equivalent series inductance figure. If a design depends on a
specified attenuation at a given frequency, that number has to come from Walsin in writing or
from your own measurement.

Can I wave solder a feed-through capacitor?

No. The FT datasheet states reflow soldering process only, at both 0402 and 0805. There is no
wave soldering profile and no wave footprint for a three-terminal part anywhere in Walsin’s
published MLCC data. Plan the board so no FT part needs a second-side wave pass.

What is the temperature rating of the Walsin FT series?

The seven FT21B X7R parts are rated −55 to +125 °C. The single 0402 part FT15X435M4R0 is
X5R and rated −55 to +85 °C, 40 °C lower. The datasheet states that both ranges include
self-heating, which matters because supply current passes through the part.

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Next step

A 3-terminal part is a layout commitment before it is a purchasing one. Send the BOM line or
the noise problem and Venatech Limited, an authorised Walsin distributor in Hong Kong, will
return the FT part numbers matching the value and voltage, the terminal dimensions to lay out
against, and a written request to Walsin for the land pattern.

Send your BOM to Venatech · Browse the
Walsin MLCC range · Read
How to read a Walsin MLCC part number and
MLCC reflow profile and mounting.

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