Automotive Chip Resistor Twin: Matching on Fields Finds 67,326 of 131,551 Walsin Commercial Parts, Where a Suffix Test Finds 36,646

An automotive chip resistor twin is not only a commercial part number plus a letter. We matched all 131,551 commercial Walsin chip resistors against the automotive series on size, resistance, tolerance, TCR and rated power. 67,326 have a field twin. A suffix test finds 36,646. The other 31,666 are hidden.

Venatech Limited, an authorised Walsin distributor in Hong Kong, holds the 137 chip resistor export files published by Walsin Technology (Walsin). This post is written from them. We published a suffix-based count of automotive twins earlier, and this post tests it a second way, on fields. The result changes the answer for the specialty series most: anti-surge, arrays, high precision and current sense. Every part number below is real and every count is of part numbers, not pieces.

How many commercial Walsin chip resistors have an automotive twin when you match on fields instead of the suffix?

67,326 of 131,551, which is 51.2 percent. We parsed all 234,401 distinct part numbers in Walsin’s published export files and split them into 102,850 in a series named “(Automotive)” and 131,551 that are not. We then asked two questions of each commercial row. Does the commercial code plus J, V or Z exist? Does an automotive row in the same series group share its size, resistance, tolerance, TCR and rated power?

We have not seen this counted anywhere. The suffix test understates the field-level twins by 30,680 parts, an 83.7 percent increase. It also overstates safety on 986 parts, where the letter exists and the part behind it is not the same on paper. For the suffix count itself, see the automotive upgrade path.

Which series groups hide the most twins?

General Purpose, High Power and High Precision, which together hold 26,682 of the 31,666 hidden twins. We counted by series group across Thick_Film_General_Purpose_*.xlsx, High_Precision_Thick_Film_chip_resistor_*.xlsx, Thick_Film_Chip_Resistor_Array__1of1.xlsx and the other export files. Anti-surge and arrays gain from zero suffix twins to 145 and 1,422 field twins respectively. Six groups remain at zero on both tests.

The six zero rows cover 10,615 commercial parts, and those are the shelves where a buyer needs a different series, not a different letter. WF12G1105FTL, an 11 megohm high ohm part at 1206, is one of them.

What do the hidden twins look like in the part number?

Not a suffix. We compared each hidden commercial code with its field twins character by character. 6,072 of the 31,666 differ only in the first letter: 4,930 from W to M and 1,142 from S to M. The other 25,594 differ elsewhere in the code. A test that appends a letter sees none of them.

The fourth row is the one to remember. MA04X1002FTL looks like the automotive version of WA04X1002FTL and the export says it is not: the TCR band is 100 ppm per degree wider. A string comparison passes it; a field comparison does not.

Why does the anti-surge shelf offer only 145 field twins for 8,340 commercial rows?

Because the two shelves share one tolerance. We read the tolerance of every anti-surge row. The commercial series carries ±5, ±10 and ±20 percent at 2,780 rows each; the automotive series carry ±0.5, ±1 and ±5 percent. Only ±5 percent is shared, so 5,560 of 8,340 commercial rows, 66.7 percent, cannot have an automotive twin at any resistance.

Within the shared ±5 percent, the wattage steps differ at every case size, so the field test succeeds only where they happen to coincide. That is 0603 at 1/4 W, 145 rows, and nowhere else. The file suffix is the tolerance: the commercial rows sit in Thick_Film_Anti_Surge_Chip_Resistor_5.xlsx, _10.xlsx and _20.xlsx, and the automotive rows in Thick_Film_Anti_Surge_Chip_Resistor_0_5.xlsx, _1.xlsx and _5.xlsx.

If wattage is ignored, 631 commercial rows find an automotive row at the same size, resistance, tolerance and TCR, and all 486 beyond the 145 are rated higher. At 1206, 2010 and 2512, none of 4,743 commercial rows finds one at any wattage.

Are the field twins identical on everything else the export carries?

On termination, always; on packaging, for 29,728 of the 31,666 hidden twins. We checked the two remaining fields in Walsin’s own export. Every hidden twin names the same termination, Sn base lead free. 1,938 differ on packaging, all in General Purpose, where the commercial reel is a 10 inch 20Kpcs or 13 inch 50Kpcs format that no automotive twin at that value shares.

Under a stricter test, where the series name must also match apart from the word “Automotive”, the field twins fall from 67,326 to 49,966, and the hidden ones from 31,666 to 14,490. Read both numbers: the true figure depends on whether General Purpose and General Purpose Anti-Sulfuration (Automotive) count as the same series. They are not the same series, and the export does not say which a design needs.

What should a buyer do before swapping a commercial part for an automotive one?

Compare the five fields yourself, then ask for the report. Suffix lookups find 27.9 percent of the twins and field lookups find 51.2 percent, so the method decides the answer. The practical sequence has three steps, and only the first is quick.

1. Cross the list on fields. Paste up to 500 part numbers into the free cross-reference tool, filter by commercial or automotive grade, and read every stated difference. It decodes 18 manufacturers’ part numbers against 800,000+ crossable Walsin part numbers.
2. Check what is held in Hong Kong on ready stock: 1,125 part numbers as at 23 September 2026, a dated snapshot. The range is on the chip resistor page.
3. Ask for the governing document by part number. We hold 28 Walsin datasheets, 451 pages, and two are chip resistor sheets. Where none covers your part, we will say so the same day. For why prefixes are not a clean guide, see chip resistor part number decoding.

Confirm against both datasheets and qualify in your own circuit.

The short version

Matching on fields finds 67,326 automotive field twins among 131,551 commercial Walsin chip resistors; matching on the suffix finds 36,646. 31,666 are hidden, 6,072 of them behind a changed first letter. Anti-surge has 145 of 8,340, because only ±5 percent is shared and no wattage step lines up beyond 0603 at 1/4 W. Six groups, 10,615 parts, have no automotive series at all, and 63,239 commercial parts pass neither test. We will not tell you a commercial part has an automotive twin. We will show you which five fields agree and which do not. Qualification stays with you.

Send us the commercial part numbers on your approved vendor list and we will tell you which have a field twin, which a suffix twin, and which neither. And a question back: when you appended a J, did you check the wattage?

Frequently asked questions