Thin Film Resistor Sizes: Walsin’s WF Line from 0201 to 2512

Walsin Technology (Walsin)’s WF thin film precision series spans eight case sizes, 0201
to 2512, across 58,314 part numbers. The resistance ceiling does not climb smoothly with
size. 0402 tops out at 255 kΩ — less than a quarter of the 1 MΩ ceiling at 0603, the very
next size up, and the single biggest proportional step in the whole line.

Venatech Limited, an authorised Walsin distributor in Hong Kong, holds Walsin’s thin film
parametric export: 93,914 rows across 20 files. Every count below is measured from that
extract. We hold no public datasheet for the WF thin film precision series — figures below
come from the parametric data, not a PDF, and are cited that way.

What case sizes does Walsin’s thin film resistor line come in?

Eight, from 0201 to 2512, but only in the WF precision series. The other two thin film
series are far narrower: tantalum nitride MF sits at 1206 only, and anti-sulfuration SF
covers just 1206 and 2010. If a design needs thin film below 0402 or above 2512, WF is the
only route, because MF and SF do not go there at all.

Source: Walsin’s thin film parametric export, counted from Venatech’s extract.

The maximum-value part at each end of the ladder is real and orderable in the data we hold.
WF02T1202BTL is the top of the 0201 range at 12.0 kΩ, ±0.1%, ≦±50 ppm/°C, 1/32 W.
WF12Q2494TTL sits at the 1206 ceiling, 2.49 MΩ, ±0.01%, ≦±50 ppm/°C, 1/4 W. WF25Q3004TTL
is the 2512 ceiling, 3.00 MΩ, ±0.01%, ≦±50 ppm/°C, 1 W — the highest resistance value in the
entire WF series, matched only by WF20Q3004TTL at 2010.

Does the resistance ceiling grow smoothly from 0201 to 2512?

No. The step from 0402 to 0603 is the largest proportional jump in the whole line, bigger
than any step above it. 0402 caps at 255 kΩ. 0603, the very next size, reaches 1.00 MΩ —
3.9 times higher. Every step after that is far gentler: 0603 to 0805 is 2.0×, 0805 to 1206
is 1.25×, and from 1206 upward the ceiling barely moves, landing at 3.00 MΩ by 2010 and
staying there through 2512.

Unique to Venatech’s data. The resistance ceiling in Walsin’s WF thin film series does
not scale with case size in proportion to area or power. The 0402-to-0603 step carries
3.9× the headroom of any later step, measured across all eight sizes in our extract. This
ratio is not published in Walsin’s own case size chart, which lists dimensions and power
but not the resistance ceiling by size.

Take one resistance value that both sizes actually carry — 255 kΩ — and the asymmetry shows
up directly. At 0402, 255 kΩ is the top of the line. At 0603, the same value sits with
3.9× of headroom still above it.

Every field that is not size or headroom matches exactly. The part number tells you the
headroom; the datasheet does not publish it as a ratio.

Why does 0402 stop at 255 kilohm when 0603 reaches 1 megohm?

Sheet resistance and film area both shrink with the footprint, and thin film has less
physical area to spread a high-value film across than thick film has paste to print. That
is the general mechanism for why resistance ceilings fall with case size. It does not,
on its own, explain why the 0402-to-0603 step is disproportionately large compared with
every step above it.

Does every case size offer the same tolerance and TCR menu?

No, and the sharpest split sits at the smallest size. Already established and published:
Venatech’s catalogue has previously shown that the 0201 case size at WF is the only one of
the eight that does not offer ±0.01% tolerance at all — every 0201 part is ±0.1%, ±0.5% or
±1%, while every part from 0402 upward is ±0.01%. See
Precision thin film resistors: ±0.01% tolerance and ±3 ppm/°C TCR
for that count in full. This post does not re-derive it; the table above already reflects
it in the “tightest tolerance” column.

What has not been shown before is that the ≦±3 ppm/°C TCR grade — the tightest in the whole
WF series — is itself narrower than the ±0.01% tolerance band that contains it. ±0.01% runs
from 0402 to 2512, seven sizes. ≦±3 ppm/°C exists at only four of those seven: 0402, 0603,
0805 and 1206. From 1210 upward, tolerance stays at ±0.01% but the tightest available TCR
relaxes to ≦±5 ppm/°C.

Which case size should I use for a given resistance value?

Work backwards from the resistance, not the footprint you’d prefer. If the value is above
255 kΩ, 0402 is not an option regardless of board space — move to 0603 or larger. If the
value is above 1 MΩ, 0603 is out too. Only 1206, 1210, 2010 and 2512 reach above 2.49 MΩ,
and only 2010 and 2512 reach the full 3.00 MΩ ceiling of the series.

• Below 255 kΩ and board space is tight. 0402 at ±0.01% and up to ≦±3 ppm/°C.
• 255 kΩ to 1 MΩ. 0603 is the smallest size that reaches it, same tolerance and TCR
  ceiling as 0402.
• 1 MΩ to 2.49 MΩ. 0805 or 1206; 1206 is the largest of the four sizes that still
  reaches ≦±3 ppm/°C.
• Above 2.49 MΩ, up to 3.00 MΩ. 2010 or 2512 only. Neither reaches tighter than
  ≦±5 ppm/°C.
• Below 27 Ω or a non-standard low value under 10 Ω. Drop to 0603 or larger; 0201 and
  0402 do not go below 27.0 Ω and 10.0 Ω respectively in this extract.

Do the MF and SF thin film series span the same sizes?

No, and this is a different constraint entirely. The tantalum nitride MF series is a single
case size — 1206 — and nothing else, across all 20,520 of its parts. The anti-sulfuration
SF series holds two sizes, 2010 (14,810 parts) and 1206 (270 parts), and no others. Neither
series offers a size ladder; only WF does. For the full breakdown of what each series
actually contains, see
What is actually in Walsin’s thin film catalogue.
The complete thin film range Venatech holds is on the
Walsin thin film resistor page.

The short version

Walsin’s thin film case size ladder is not a straight line. The resistance ceiling nearly
quadruples from 0402 to 0603 and then grows gently, almost flattening out by 1206. The
tightest TCR grade, ≦±3 ppm/°C, exists only from 0402 to 1206 — four of the eight sizes —
even though ±0.01% tolerance itself reaches all the way to 2512. Pick the case size from the
resistance value and the TCR grade you need, not from the board footprint alone.

Send us the resistance, tolerance and TCR your circuit needs and we will tell you which
WF case size actually carries it, with the part number. Or send a BOM line and ask us to
confirm what size it resolves to.

Two things you can do without waiting for a reply. Cross your part — paste a single number or drop in an Excel or CSV of the whole line, and each result names what matches and what does not. And ready stock lists the thin film resistor part numbers held in Hong Kong, with an RFQ against any of them.

Frequently asked questions