Walsin Technology (Walsin) reaches ±0.01% tolerance and ≦±3 ppm/°C TCR in the WF thin
film precision series. Venatech holds 58,314 WF parts; 52,808 of them are ±0.01% and 3,064
carry the ±3 ppm grade. The tightest high precision thick film in the same catalogue stops
at ±0.1% and ≦±25 ppm/°C. Tight tolerance is the WF norm.
Venatech Limited, an authorised Walsin distributor in Hong Kong, holds Walsin’s own
parametric export for the thin film range: 93,914 parts across three series. Every figure
below is counted from that extract, not quoted from a marketing page.
Flagged for review. We hold no public datasheet URL for the Thin Film Precision Chip
Resistor / WF Series or for the High Precision Thick Film Chip Resistor series. Both are
cited by series name in this post. Confirm the public PDF addresses with Walsin before
publishing, and add per-series links then.
What tolerance and TCR can a Walsin precision thin film resistor reach?
Two numbers set the ceiling. Tolerance reaches ±0.01%, which is 100 ppm of initial
resistance. TCR reaches ≦±3 ppm/°C. Both grades exist in the same series, the WF thin film
precision family, and both appear on real orderable parts rather than on a special-order
line.
The two specifications are not independent in this catalogue. Every one of the 3,064 parts
at ≦±3 ppm/°C is also ±0.01%. Walsin does not publish a loose-tolerance, ultra-low-TCR
part, which is the right engineering decision: a ±1% part with a 3 ppm temperature
coefficient would spend its error budget before the board warmed up.
Six TCR grades exist in the WF series: ≦±50 at 17,546 parts, ≦±25 at 18,341, ≦±15 at 6,678,
≦±10 at 6,678, ≦±5 at 6,007 and ≦±3 at 3,064. The depth sits in the middle of the range.
How many Walsin WF parts are actually ±0.01%?
52,808 of 58,314. That is 90.6% of the series. The remaining 5,506 parts split into ±0.1%
at 1,674, ±0.5% at 1,916 and ±1% at 1,916, and every one of those 5,506 sits in the 0201
(0603) case size. From 0402 upward the series is ±0.01% and nothing else.
Unique to Venatech’s data. 52,808 of the 58,314 Walsin WF precision thin film parts
Venatech holds are ±0.01% tolerance. The tight-tolerance part is the norm in this series,
not the exception, and the looser grades exist only at 0201. Counting the extract by size
shows a clean split with no overlap: 0402, 0603, 0805, 1206, 1210, 2010 and 2512 return
±0.01% on every row. This distribution is not published anywhere.
The consequence is a sourcing one. An engineer who specifies ±0.1% in a 1206 footprint and
searches the WF series for it gets nothing back, because the series does not offer ±0.1% at
1206. What fits is either the ±0.01% thin film, tighter than asked for, or a high precision
thick film part from a different catalogue.
Which case sizes carry the ±3 ppm/°C grade?
Four: 0402 (1005), 0603 (1608), 0805 (2012) and 1206 (3216). The count by size is 595, 769,
832 and 868 parts respectively, for 3,064 in total. There is no ±3 ppm part at 0201, 1210,
2010 or 2512. Above 1206 the tightest TCR available is ≦±5 ppm/°C.
| Case size | WF parts held | Tightest tolerance | Tightest TCR | ±3 ppm available |
|---|---|---|---|---|
| 0201 (0603) | 5,506 | ±0.1% | ≦±25 ppm/°C | Mismatch — no ±3 ppm part |
| 0402 (1005) | 6,359 | ±0.01% | ≦±3 ppm/°C | Match — 595 parts |
| 0603 (1608) | 7,562 | ±0.01% | ≦±3 ppm/°C | Match — 769 parts |
| 0805 (2012) | 7,985 | ±0.01% | ≦±3 ppm/°C | Match — 832 parts |
| 1206 (3216) | 8,427 | ±0.01% | ≦±3 ppm/°C | Match — 868 parts |
| 1210 (3225) | 7,216 | ±0.01% | ≦±5 ppm/°C | Mismatch — stops at ±5 ppm |
| 2010 (5025) | 7,436 | ±0.01% | ≦±5 ppm/°C | Mismatch — stops at ±5 ppm |
| 2512 (6432) | 7,823 | ±0.01% | ≦±5 ppm/°C | Mismatch — stops at ±5 ppm |
The larger sizes lose the tightest TCR grade and gain power handling instead. At 2512 the WF
series reaches 1 W; at 0402 it is 1/10 W. A bridge or divider that needs 3 ppm tracking has
to fit inside 1206 and inside 1/4 W.
How does precision thin film compare with high precision thick film in the same size?
Field by field, at 1206 and 470 Ω. Both technologies exist in Walsin’s catalogue at that
footprint, both are reel-taped, both use a lead-free tin base termination, and both are
rated 1/4 W. Tolerance and TCR are where they separate, and they separate by an order of
magnitude on each.
| Field | WF12B4700TTL (thin film WF) | WF12J4700BTL (thick film TC25) | MF12F4700ATL (tantalum nitride MF) | WR12X4700FTL (thick film general purpose) | Match / mismatch |
|---|---|---|---|---|---|
| Technology | Thin film | Thick film | Tantalum nitride thin film | Thick film | Mismatch — four different films |
| Case size | 1206 (3216) | 1206 (3216) | 1206 (3216) | 1206 (3216) | Match — all four |
| Resistance | 470 Ω | 470 Ω | 470 Ω | 470 Ω | Match — all four |
| Tolerance | ±0.01% | ±0.1% | ±0.05% | ±1% | Mismatch — 100:1 spread |
| TCR | ≦±3 ppm/°C | ≦±25 ppm/°C | ≦±15 ppm/°C | ≦±100 ppm/°C | Mismatch — 33:1 spread |
| Rated power | 1/4 W | 1/4 W | 2/5 W | 1/4 W | Mismatch — MF is higher |
| Packaging | 7″ reel taping | 7″ reel taping | 7″ reel taping | 7″ reel taping | Match — all four |
| Termination | Sn base (lead free) | Sn base (lead free) | Sn base (lead free) | Sn base (lead free) | Match — all four |
| Series group | Thin film precision | High precision thick film | Tantalum nitride thin film | Thick film general purpose | Mismatch — four catalogue paths |
Four parts, one footprint, one resistance value. Nothing in the case size or the resistance
tells you which you are holding. The part number does, from the fifth character onward.
Walsin’s high precision thick film group is not small — 52,027 parts, within 120 parts of
the WF thin film series. Its tolerance ladder runs ±1%, ±0.5%, ±0.25% and ±0.1%, and stops.
Its TCR ladder runs ≦±200, ≦±100, ≦±50 and ≦±25 ppm/°C, and stops. The ≦±25 grade exists on
3,087 parts, in three case sizes only: 0603, 0805 and 1206, at 1,029 parts each.
Thick film gets you to ±0.1% and 25 ppm/°C across eight case sizes. Thin film gets you to
±0.01% and 3 ppm/°C across four. The crossover is at ±0.1%, where both exist.
Why does 0201 not offer ±0.01% tolerance?
Because the trim resolution and the absolute film area do not support it at that size in
this series. Walsin’s 0201 WF parts are offered at ±0.1%, ±0.5% and ±1% only, with TCR at
≦±25 or ≦±50 ppm/°C, at 1/20 W and 1/32 W. The tight grades begin at 0402.
WF02Q27R0DTL is a 0201 WF part: 27.0 Ω, ±0.5%, ≦±25 ppm/°C, 1/20 W. WF02T1000BTL is the
tighter 0201 option at 100 Ω, ±0.1%, ≦±50 ppm/°C, 1/32 W. Note the trade in the second part
— tighter tolerance comes with looser TCR and lower power at that size.
Flagged for review. Walsin’s export shows the tolerance and TCR limits at 0201 but
does not state a reason. The explanation above is engineering inference, not a Walsin
statement. Ask Venatech to obtain Walsin’s position before repeating it in a design
review.
What resistance range comes with each TCR grade?
The tighter the TCR, the narrower the resistance window. Measured across the WF extract, the
≦±3 ppm grade spans 4.7 Ω to 120 kΩ. ≦±5 ppm reaches 597 kΩ. ≦±10 and ≦±15 ppm both reach
1.5 MΩ. ≦±25 and ≦±50 ppm run the full 1 Ω to 3 MΩ span of the series.
| TCR grade | Parts held | Resistance span | Case sizes | Match to full series span |
|---|---|---|---|---|
| ≦±3 ppm/°C | 3,064 | 4.7 Ω – 120 kΩ | 0402 to 1206 | Mismatch — 4% of the decade span |
| ≦±5 ppm/°C | 6,007 | 4.7 Ω – 597 kΩ | 0402 to 2512 | Mismatch — no low ohm, no high ohm |
| ≦±10 ppm/°C | 6,678 | 4.7 Ω – 1.5 MΩ | 0402 to 2512 | Mismatch — half the top decade |
| ≦±15 ppm/°C | 6,678 | 4.7 Ω – 1.5 MΩ | 0402 to 2512 | Mismatch — half the top decade |
| ≦±25 ppm/°C | 18,341 | 1 Ω – 3 MΩ | 0201 to 2512 | Match — full span |
| ≦±50 ppm/°C | 17,546 | 1 Ω – 3 MΩ | 0201 to 2512 | Match — full span |
A ratio-matched divider at 1 MΩ cannot use the 3 ppm grade, because the grade does not exist
above 120 kΩ. Scale the divider down, or accept 10 ppm. The constraint is invisible until
the parametric filter is applied in the right order.
How do I read the tolerance and TCR letters in a WF part number?
Two characters carry it. The fifth character encodes TCR and rated power together. The
third character from the end encodes tolerance. Everything between is the case size and the
resistance value in a three-significant-figure plus multiplier form.
Take WF12B4700TTL.
| Character | Position | Value in WF12B4700TTL |
Means |
|---|---|---|---|
| WF | 1–2 | WF | Series prefix — see the caution below |
| 12 | 3–4 | 12 | 1206 (3216) |
| B | 5 | B | TCR ≦±3 ppm/°C |
| 4700 | 6–9 | 4700 | 470 Ω |
| T | 10 | T | Tolerance ±0.01% |
| TL | 11–12 | TL | Taping and lead-free tail |
The tolerance codes verified across the WF extract are T for ±0.01%, B for ±0.1%, D for
±0.5% and F for ±1%. The TCR codes are B, Z, W, F, R, U, Q and T, and two pairs repeat a TCR
value at a different rated power: R and U are both ≦±25 ppm/°C, at 1/4 W and 1/8 W.
Does a part number starting WF always mean thin film?
No, and this is the trap. 76,968 part numbers in Walsin’s thick film chip resistor export
also begin WF, across seven different series groups. Added to the 58,314 thin film WF
parts, 135,282 Walsin resistors share the same two-letter prefix across two separate
technologies and two separate catalogues.
Unique to Venatech’s data. The
WFprefix is not a thin film marker. Venatech’s
extract holds 58,314 thin film WF parts and 76,968 thick film parts whose numbers also
beginWF— high precision, high power, high voltage, anti-surge, trimmable, wide
terminal and high ohm. There are zero exact part-number collisions between the two sets;
the fifth character is the only thing separating them. Thin film uses B, Z, W, F, R, U, Q
and T in that position. Thick film uses A, G, H, J, K, L, M, N, P, S and V. Neither
catalogue warns you about the other.
WF12B4700TTL and WF12J4700BTL are both real Walsin parts, both 1206, both 470 Ω, both
1/4 W. One is ±0.01% thin film at 3 ppm/°C. The other is ±0.1% thick film at 25 ppm/°C. A
BOM line that reads “WF12” plus a resistance has not specified a part. Check the fifth
character before ordering, and again on the packing list.
FAQ
What is the tightest tolerance chip resistor Walsin makes?
±0.01%, in the WF thin film precision series. Venatech holds 52,808 Walsin parts at that
tolerance across seven case sizes from 0402 to 2512. The tightest grade in Walsin’s high
precision thick film range is ±0.1%, on 16,103 parts. The two ranges meet at ±0.1% and do
not overlap below it.
What is the lowest TCR Walsin chip resistor?
≦±3 ppm/°C, on 3,064 WF thin film parts. All of them are also ±0.01% tolerance, and all of
them sit in 0402, 0603, 0805 or 1206. The resistance span at that grade is 4.7 Ω to 120 kΩ.
Above 1206 the tightest grade available drops to ≦±5 ppm/°C.
Can I get ±0.01% tolerance in an 0201 chip resistor from Walsin?
No. All 5,506 Walsin WF parts at 0201 (0603) are ±0.1%, ±0.5% or ±1%, with TCR at ≦±25 or
≦±50 ppm/°C. The ±0.01% grade begins at 0402 (1005) and runs through to 2512 (6432). If the
design needs ±0.01%, the footprint has to grow.
Is thin film always better than thick film for precision?
For tolerance and TCR, yes in this catalogue — ±0.01% and 3 ppm against ±0.1% and 25 ppm.
For power handling and case size coverage, not automatically. Walsin’s high precision thick
film group covers eight case sizes and reaches 1 W, and it holds 52,027 parts against the
WF series’ 58,314.
How do I tell a Walsin thin film part from a thick film part?
By the fifth character of the part number, not the prefix. 135,282 Walsin resistors begin
WF across both technologies. Thin film uses B, Z, W, F, R, U, Q or T in position five.
Thick film uses A, G, H, J, K, L, M, N, P, S or V. There are no exact part-number collisions
between the two sets.
Does a ±0.01% resistor stay at ±0.01% in circuit?
No. Tolerance is the initial value at reference temperature. TCR, self-heating, moisture and
load life all move it afterwards. A ±0.01% part with 25 ppm/°C TCR drifts 0.125% over a
50°C rise, which is twelve times its initial tolerance. Specify TCR and tolerance together.
What rated power comes with the precision thin film sizes?
The WF series runs 1/32 W and 1/20 W at 0201, 1/16 W and 1/10 W at 0402 and 0603, 1/8 W and
1/10 W at 0805, 1/4 W and 1/8 W at 1206, 1/4 W and 2/5 W at 1210, 1/2 W and 3/4 W at 2010,
and 1 W and 3/4 W at 2512. Power and TCR grade are chosen together.
Are the WF precision parts available on tape and reel?
Every one of the 58,314 WF parts in Venatech’s extract lists 7″ reel taping and a lead-free
tin base termination. No other packaging option appears on any row. Stock position is a
snapshot and moves, so confirm availability on the specific part number rather than on the
series.
Next step
Precision is a four-field decision: tolerance, TCR, resistance and case size. All four
constrain each other in this catalogue, and the constraint only shows up when you filter in
the right order.
Send your BOM and Venatech Limited, an authorised Walsin distributor in Hong Kong, will
return the Walsin part that matches on size and resistance, the tolerance and TCR actually
available at that footprint, and every field where it differs from the one you specified.
Send your BOM to Venatech · Browse the
Walsin thin film range · Read
Thin film vs thick film chip resistors and
Chip resistor power rating by case size.