The Thin Film TCR and Tolerance Grid: 26 of 36 Cells Are Real

We counted every thin film TCR tolerance pair in Walsin’s 93,914-row export. The grid has 36 cells; 26 exist and 10 are empty. The tightest grade, ≦±3 ppm/°C, appears at exactly one tolerance — ±0.01%. Low drift at a loose tolerance cannot be bought here at all.

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Six TCR grades and six tolerances imply thirty-six choices. A selector will draw all thirty-six and let you tick any of them. Ten of those tickets lead nowhere, and which ten is not something the drop-down tells you.

Venatech Limited, an authorised Walsin distributor in Hong Kong, holds all 203 of Walsin Technology (Walsin) parametric export files. This post is measured from the eleven non-empty thin film files — the eight Thin_Film_Precision_Chip_Resistor_WF_Series_*.xlsx sheets, Tantalum_nitride_Thin_Film_Chip_Resistor_MF_Series_1.xlsx and two Anti_Sulfuration_Thin_Film_Chip_Resistor_SF_Series_*.xlsx sheets. We re-counted the files themselves: 9 of the 20 return zero rows. Every part number below is real, and every count is of part numbers rather than pieces.

How many of the 36 thin film TCR and tolerance combinations actually exist?

Twenty-six. We cross-tabulated all 93,914 rows on the two columns an engineer filters first. The TCR column holds exactly six values — ≦±3, ≦±5, ≦±10, ≦±15, ≦±25 and ≦±50 ppm/°C — and the Tolerance column holds exactly six — ±0.01%, ±0.05%, ±0.1%, ±0.25%, ±0.5% and ±1%. Of the 36 intersections, 26 carry at least one part and 10 are empty. All ten empty cells sit in the two tightest TCR rows.

TCR	±0.01%	±0.05%	±0.1%	±0.25%	±0.5%	±1%
≦±3 ppm/°C	3,064	—	—	—	—	—
≦±5 ppm/°C	6,007	—	—	—	—	—
≦±10 ppm/°C	6,678	1,026	1,026	1,026	1,026	1,030
≦±15 ppm/°C	6,678	1,026	1,026	1,026	1,026	1,026
≦±25 ppm/°C	15,177	2,156	3,849	3,261	4,219	4,227
≦±50 ppm/°C	15,204	2,156	2,582	2,156	3,114	3,122

We have not seen this grid counted anywhere. The shape of it is the point: the row totals are not proportional, the ±0.01% column holds 52,808 of the 93,914 rows on its own, and the two tightest TCR rows have a single occupied cell each. A catalogue that looks like a matrix is really a staircase.

Can you buy Walsin’s tightest TCR at a loose tolerance?

No. All 3,064 ≦±3 ppm/°C rows and all 6,007 ≦±5 ppm/°C rows carry ±0.01% tolerance, and nothing else. We checked both grades against every other tolerance value in the export and found zero rows. So the two specifications are welded together: if your circuit needs 3 ppm/°C drift but tolerates ±0.5% initial error, Walsin will still sell you ±0.01% and you will still pay for a trim you did not ask for.

That is the opposite of how most buyers model the trade-off. The usual assumption is that tolerance is the expensive axis and TCR follows it, so loosening tolerance should widen the shelf. Here it closes it. We re-measured the resistance ceiling too: ≦±3 tops out at 120 kΩ while ≦±25 and ≦±50 reach 3 MΩ, and ≦±3 is present at four of the export’s eight case sizes — a figure we have published before and have now confirmed against the current files.

How many of the 26 live cells come from a single series?

Fifteen of the 26. We tagged every occupied cell with the series behind it. Six cells — the whole ±0.01% column — are WF Series and nothing else. Nine more are the tantalum nitride MF Series alone. That leaves eleven cells with two or three series in them, and those eleven are the only places in the grid where you have a real second choice inside Walsin’s own catalogue.

Worse for a sourcing engineer: 10 of the 26 live cells exist at exactly one case size, 1206. Every ≦±10 and ≦±15 cell at a tolerance looser than ±0.01% is 1206 only, because all 20,520 MF Series rows are 1206. Pick a 0805 footprint and ask for ±10 ppm/°C at ±0.1%, and the grid says yes while the catalogue says no.

Grid region	Live cells	Series present	Case sizes present	Match / mismatch vs a free choice of tolerance and TCR
≦±3 and ≦±5 ppm/°C	2 of 12	WF only	4 and 7 of 8	Mismatch — tolerance is fixed at ±0.01%, no choice at all
≦±10 and ≦±15 ppm/°C, loose tolerance	10 of 10	MF only (one cell adds SF)	1 of 8 — 1206	Mismatch — footprint is fixed at 1206
≦±25 and ≦±50 ppm/°C, loose tolerance	10 of 10	WF, MF and SF	2 or 3 of 8	Match on freedom of choice; mismatch on drift
±0.01% column	6 of 6	WF only	7 of 8	Mismatch — 0201 carries no ±0.01% part

Why does one 10 kΩ position at 1206 reproduce the whole grid?

Because the grid’s shape is set by series structure, not by resistance. We pulled every row at 1206 and exactly 10,000 Ω: 28 parts, occupying 26 distinct TCR-and-tolerance cells — the same 26 that the full 93,914-row export occupies. One value in one footprint is a complete scale model of the catalogue. That makes it the cheapest test available: if a cell is empty at 10 kΩ 1206, it is empty everywhere.

Here is the part of that set a 10 kΩ, ±0.1%, ≦±10 ppm/°C requirement actually hits. We will not tell you a part is equivalent. We will show you where it differs.

Part number	Series	Size	Tolerance	TCR	Rated power	Match / mismatch vs 10 kΩ ±0.1% ≦±10 ppm/°C 1206
MF12W1002BTL	Tantalum nitride MF	1206	±0.1%	≦±10	2/5 W	Match on all four fields — the only exact hit in the export
MF12W1002ATL	Tantalum nitride MF	1206	±0.05%	≦±10	2/5 W	Match on TCR and size; mismatch — tighter tolerance than asked
WF12W1002TTL	Thin Film Precision WF	1206	±0.01%	≦±10	1/4 W	Match on TCR and size; mismatch — ±0.01% only, and 1/4 W not 2/5 W
WF12B1002TTL	Thin Film Precision WF	1206	±0.01%	≦±3	1/4 W	Mismatch — best TCR in the catalogue, unavailable at ±0.1%
WF12F1002TTL	Thin Film Precision WF	1206	±0.01%	≦±15	1/4 W	Mismatch — 1.5× the drift and the wrong tolerance
MF12R1002BTL	Tantalum nitride MF	1206	±0.1%	≦±25	2/5 W	Match on tolerance and size; mismatch — 2.5× the drift
MF12Q1002FTL	Tantalum nitride MF	1206	±1%	≦±50	2/5 W	Mismatch on both axes; the loosest cell at this value
SF20U1002ATL	Anti-Sulfuration SF	2010	±0.05%	≦±25	1/2 W	Mismatch — 2010 footprint, 2.5× the drift, sulfur-resistant film

One exact hit out of twenty-eight. The other twenty-seven match on resistance and differ somewhere a selector does not show you side by side. Confirm against both datasheets and qualify in your own circuit — that step stays with you, and we will not pretend otherwise.

Does a part number starting WF mean the part is thin film?

No, and this is the trap that will corrupt a filtered list before the grid ever gets a chance to. We read the part numbers in both exports. The thin film export holds 58,314 rows beginning WF, 20,520 beginning MF and 15,080 beginning SF. The chip resistor export holds 76,968 beginning WF, 14,791 beginning MF and 10,690 beginning SF — and every one of those 102,449 rows sits in a thick film series.

So more thick film parts carry a thin-film-looking prefix than there are thin film parts in the whole catalogue. WF12H1202BTL is a High Precision Thick Film chip resistor TC100 part from High_Precision_Thick_Film_chip_resistor_0_1_1_4W.xlsx, at 12 kΩ, ±0.1%, ≦±100 ppm/°C. MF12E1R00FTL is a Thick Film Triple Power Surge automotive part at 1.00 Ω. We checked: zero part numbers appear in both files, so there is no duplicate to catch the error for you. Prefix-filter your way to a thin film shortlist and roughly half of it will be thick film with a ≦±100 ppm/°C floor — two full steps outside the grid above.

The dated snapshot shows the same thing commercially. Of the 1,125 catalogue codes on our ready stock list as at 23 September 2026, thirteen begin WF, MF or SF. We checked all thirteen against the thin film export: not one is in it. Ten are thick film parts in the chip resistor export and three — including WF06U5363BTL — have no matching row in any parametric export at all.

Do we hold a thin film datasheet to confirm any of this?

No. We hold 28 Walsin datasheets, 451 pages, and exactly two are chip resistor sheets: Walsin_MR_Automotive_Thick_Film_Chip_Resistor.pdf and Walsin_WR_General_Purpose_Chip_Resistor.pdf. Neither covers WF, MF or SF thin film. For the thin film line we hold zero datasheets, so every TCR and tolerance figure in this post is the export’s own value and nothing in our library confirms it.

That matters most for the ±0.01% column. 52,808 rows at 0402 and above all read ±0.01% and nothing else, while the 0201 file carries three tolerances — ±0.1%, ±0.5% and ±1% — and no ±0.01% at all. A single value repeated across eight files and seven case sizes is the signature of a column populated from a series default rather than from a trimmed part, and we cannot distinguish the two without the sheet.

Where we can be checked, we are. UL file E182369 covers Walsin’s safety capacitor line and is searchable in UL’s own public database in about thirty seconds. That is the standard this post is held to, and on thin film it is the standard the figures currently fail. We will tell you what we do not have. Most distributors will not.

What should a buyer in the United States or Germany do with the grid?

Fix the cell before the resistance. A 10 kΩ 1206 position has 28 Walsin candidates and exactly one lands on ±0.1% with ≦±10 ppm/°C; the other 27 are a different cell wearing the same resistance. The trade press reported passive component lead times stretching through 2026 while AI server and electric vehicle programmes drew on the same capacity, so the practical question is which of the 28 is in a warehouse.

1. Write the cell, not the two numbers. “±0.1% and ≦±10 ppm/°C” is one cell of 26, available in one series at one case size. Say that in the requirement and you will not lose a week discovering it at quote stage.
2. Cross the whole BOM in one pass. Paste up to 500 part numbers or drop your Excel or CSV into the free cross-reference tool. It is matched against Walsin’s published catalogue and returns candidates field by field, with every difference from your original stated rather than hidden. Filter by commercial or automotive grade, or for soft termination, high temperature, safety certified, high Q / low ESR or low profile.
3. Check what is physically in Hong Kong on ready stock before you commit to a production slot. That page is a dated snapshot as at 23 September 2026, not a live feed, and 254 of its 1,125 codes are chip resistors.

For the tolerance and TCR ceilings on their own, see precision thin film tolerance and TCR. For what the ratio of two such parts does, see precision resistor divider accuracy. For the empty files behind the 9-of-20 count, see nine Walsin thin film exports return nothing. The full range is on the Walsin thin film range page.

The short version

Thin film TCR and tolerance are not an independent pair. Thirty-six combinations exist on paper and 26 exist in Walsin’s 93,914 rows. The ≦±3 and ≦±5 ppm/°C grades are sold at ±0.01% and at no other tolerance. Fifteen of the 26 live cells come from one series, and ten of them exist at one case size only. One 10 kΩ position at 1206 holds 28 parts and reproduces all 26 cells, which makes it the cheapest way to test a requirement before you cross a list. And 102,449 thick film rows carry a WF, MF or SF prefix, so a prefix filter is not a thin film filter. We hold no thin film datasheet, so every figure here is the export’s and is flagged as such. Qualification stays with you.

Send us the precision resistors off your BOM with the cell you actually need — tolerance and TCR together, not separately — and we will come back with Walsin candidates field by field, differences included, then tell you which of them was in Hong Kong on 23 September 2026. And if your selector offered you ≦±3 ppm/°C at ±0.5%, we would like to know whose selector it was: we cannot find a single part that fits.

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Frequently asked questions

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