Chip Resistor Short Time Overload: Walsin’s 2.5 Times Rule Puts 6.25 Times Rated Power Into 22,526 Rows and Less Than Rated Into 6,933

Chip resistor short time overload in Walsin’s WR and MR sheets is a voltage rule, not a pulse rating. We applied it to 33,192 export rows: 22,526 receive 6.25 times rated power for 5 seconds, 3,733 receive between 1 and 6.25 times, and 6,933 receive less than their rated power.

---

If you read “short time overload” as a pulse withstand figure, the sheet does not support it. Venatech Limited, an authorised Walsin distributor in Hong Kong, holds both chip resistor approval sheets from Walsin Technology (Walsin), ASC_WR_V24 (SEP 2016) and ASC_MR_V13 (Mar 2024), and the 137 chip resistor export files. This post is written from page 3 and the test pages of each sheet and from the 33,192 non-jumper WR and MR rows at sizes the sheets tabulate. Every part number is real. The rest is arithmetic on the sheets’ own formula, and you can repeat it on your own bill of materials.

What does Walsin’s short time overload test actually specify?

One voltage, held for 5 seconds, with a resistance-change limit afterwards. Both sheets print the same row: “2.5 times RCWV or max. overload voltage, for 5 seconds”. We read the test pages of Walsin_WR_General_Purpose_Chip_Resistor.pdf (page 8) and Walsin_MR_Automotive_Thick_Film_Chip_Resistor.pdf (page 9) and the requirement is identical: resistance change within 2 percent plus 0.05 ohm at 5 percent tolerance and within 1 percent plus 0.05 ohm at 1 percent, no visible damage.

RCWV is the rated continuous working voltage, which page 3 of each sheet defines as the lower of the square root of rated power times resistance and a printed maximum operating voltage. The same sheets print a maximum overload voltage for each size. There is no power, current, energy or duration other than the 5 seconds in the test row, and the sheet does not say whether the “or” means the lower of the two voltages or either of them.

Does the overload voltage follow from the rating?

Yes, as a fixed ratio, and that creates the ambiguity. We compared the two printed voltages at every tabulated size. Max overload voltage is exactly twice max operating voltage at all 5 sizes, page 3 of ASC_WR_V24 and ASC_MR_V13: 200 to 400 V at 1210 and 1206, 150 to 300 V at 0805, 75 to 150 V at 0603 and 50 to 100 V at 0402.

A 2.5 times multiplier on a quantity that is capped at the operating ceiling would exceed twice that ceiling. Once RCWV passes 0.8 times the ceiling, 2.5 times RCWV is higher than the maximum overload voltage in the same table. That happens at every size, and it is the reason one sentence yields two test voltages above a size-specific resistance.

Size	Max operating voltage	Max overload voltage	Rated power in sheet	Resistance above which 2.5 x RCWV exceeds the overload voltage	Match / mismatch of the two readings above that resistance
1210 (MR)	200 V	400 V	1/2 W	51.2 kilohm	Mismatch: 500 V against 400 V
1206	200 V	400 V	1/4 W	102.4 kilohm	Mismatch: 500 V against 400 V
0805	150 V	300 V	1/8 W (WR)	115.2 kilohm	Mismatch: 375 V against 300 V
0603	75 V	150 V	1/10 W	36 kilohm	Mismatch: 187.5 V against 150 V
0402	50 V	100 V	1/16 W (WR)	25.6 kilohm	Mismatch: 125 V against 100 V

The threshold is 0.64 times the ceiling squared over the rated power. The 0805, 0603 and 0402 rows use the WR ratings of 1/8 W, 1/10 W and 1/16 W; the MR sheet prints 1/4 W, 1/8 W and 1/10 W for those three sizes.

How many rows get two different test voltages from one sentence?

10,666 of 33,192, which is 32.1 percent. We parsed every WR row at 1206, 0805, 0603 and 0402 (19,640) in files such as Thick_Film_General_Purpose_1_1_4W.xlsx and every MR row at 1210, 1206, 0805, 0603 and 0402 (13,552), took rated power from the export, and found that the two readings of the test give a different voltage on 10,666. WR has 6,220 of these rows and MR 4,446.

Size	Rows tested	Rows where the two readings differ	Rows whose capped test dissipates less than rated power	Match / mismatch against “the test is an overload”
0402	7,744	2,915	2,026	Mismatch on 26.2% of rows
0603	7,744	2,727	1,860	Mismatch on 24.0%
0805	7,744	2,192	1,307	Mismatch on 16.9%
1206	8,024	2,200	1,320	Mismatch on 16.5%
1210	1,936	632	420	Mismatch on 21.7%
All five	33,192	10,666	6,933	Mismatch on 20.9%

The export’s Rated Power column is the only power source for these rows. The crossover logic is the one in our earlier working voltage against rated power post: the same 33,192 rows, the same formula.

How much power does the 5-second test put into a chip resistor?

Usually 6.25 times rated power, and sometimes less than rated. Dissipated power is voltage squared over resistance. Below the crossover, 2.5 times RCWV squares to 6.25 times rated power, and that applies to 22,526 rows: 67.9 percent. Another 3,733 rows (11.2 percent) sit between 1 and 6.25 times. 6,933 rows (20.9 percent) get less than their own rated power.

We have not seen this counted anywhere: every one of the 4,760 rows at 1 megohm and above gets less than rated power in the capped reading, so the “overload” is not an overload in watts for the whole top decade. The lowest case is 0.010 times: MR04X106 JTL is 10 megohm at 0402 and 1/10 W, and 100 V across it dissipates 1 mW against a 100 mW rating.

Band of multiple of rated power, capped reading	Rows	Share of 33,192	Match / mismatch against “a 6.25 times power test”
Exactly 6.25	22,526	67.9%	Match
Between 1.0 and 6.25	3,733	11.2%	Mismatch
Less than 1.0	6,933	20.9%	Mismatch

For a 1/4 W 1206 at 10 kilohm, 6.25 times is 1.5625 W for 5 seconds, 7.8 joules. For the same part at 10 megohm it is 16 mW.

Which real part numbers show each case?

Six, one per behaviour. All six are in the export and in the 360,078 part numbers we check against. Voltages are the capped reading and the unbounded reading; power is voltage squared over resistance.

Part number	Size, resistance, rated power	RCWV	Test voltage, unbounded / capped	Power, unbounded / capped	Match / mismatch of the two readings	Your incumbent part (fill in)
WR12X1002FTL	1206, 10 kilohm, 1/4 W	50.0 V	125 V / 125 V	1,562.5 mW / 1,562.5 mW (6.25x)	Match
MR10X1002FTL	1210, 10 kilohm, 1/2 W	70.7 V	176.8 V / 176.8 V	3,125 mW / 3,125 mW (6.25x)	Match
WR06X1003FTL	0603, 100 kilohm, 1/10 W	75 V	187.5 V / 150 V	351.6 mW / 225 mW (3.52x / 2.25x)	Mismatch
WR12X1004FTL	1206, 1 megohm, 1/4 W	200 V	500 V / 400 V	250 mW / 160 mW (1.00x / 0.64x)	Mismatch
MR04X1004FTL	0402, 1 megohm, 1/10 W	50 V	125 V / 100 V	15.6 mW / 10 mW (0.16x / 0.10x)	Mismatch
WR12W1005FTLV	1206, 10 megohm, 1/4 W	200 V	500 V / 400 V	25 mW / 16 mW (0.10x / 0.064x)	Mismatch

Read the 1206 rows together. At 10 kilohm the test is an overload of 6.25 times in watts. At 1 megohm, 1206 and 1/4 W, the unbounded reading dissipates exactly the rating, 250 mW, and the capped reading 64 percent of it. The test voltage is 500 V or 400 V against the 200 V working ceiling.

Does either Walsin sheet state a pulse or surge limit?

No. We searched the text of both sheets for pulse, surge, energy and single-pulse language and found none for a resistor’s electrical rating; the only “pulse” is the half-sine shock pulse in the MR mechanical shock test. The only “Peak Current” is the zero-ohm jumper table, which prints 5 A, 3.5 A, 3 A and 2 A on WR and up to 10 A on MR, with no duration beside any of them.

Walsin’s export lists anti-surge series, and we hold no sheet for any of them. Our anti-surge chip resistors post covers what the export does and does not say, and the free cross-reference will show you the differences between a surge-rated incumbent and a Walsin row field by field. For the thermal side of the same sheets, see the derating curve, which has the 70 °C and 155 °C line behind the rated power used here.

What a designer can take from the sheets is a voltage a part survived for 5 seconds with a resistance shift under 1 percent plus 0.05 ohm. A pulse train, a long-duration surge or a sub-millisecond transient is not covered, and neither is energy. We hold 28 Walsin datasheets, 451 pages, two of them chip resistors: ask for the sheet covering your part number and it will be in your inbox. Ready stock lists 1,125 part numbers as at 23 September 2026, a dated snapshot and not a live feed. Families sit on the chip resistor page.

The short version

Walsin’s short time overload test is 2.5 times RCWV, or the max overload voltage, for 5 seconds. Max overload voltage is exactly twice max operating voltage at all 5 sizes, so the two readings diverge on 10,666 of 33,192 rows, 32.1 percent. In watts the test is 6.25 times rated power on 22,526 rows, between 1 and 6.25 times on 3,733, and less than rated power on 6,933, including all 4,760 rows at 1 megohm and above. Neither sheet states a pulse limit. We will not tell you a part survives your surge. We will show you the voltage the sheet tested at. Confirm against both datasheets and qualify in your own circuit.

Send us the part number and the pulse your board sees, and we will tell you which sheet the part falls under and what that sheet does not cover. And a question back: when a datasheet says “overload”, do you check whether it is in volts, watts or joules?

---

Frequently asked questions

<!– wp:rank-math/faq-block {"questions":[{"id":"faq-question-01","title":"What is the short time overload test in Walsin's chip resistor sheets?","content":"2.5 times the rated continuous working voltage, or the maximum overload voltage, applied for 5 seconds. Both the WR and MR sheets print the same row and the same limit: resistance change within 2 percent plus 0.05 ohm at 5 percent tolerance, 1 percent plus 0.05 ohm at 1 percent, with no visible damage.","visible":true},{"id":"faq-question-02","title":"How does the maximum overload voltage relate to the operating voltage?","content":"It is exactly twice, at all five sizes the sheets tabulate: 400 V against 200 V at 1210 and 1206, 300 V against 150 V at 0805, 150 V against 75 V at 0603 and 100 V against 50 V at 0402. A 2.5 times multiplier therefore exceeds the overload voltage once RCWV passes 0.8 times the ceiling.","visible":true},{"id":"faq-question-03","title":"How many watts does the overload test put into a Walsin resistor?","content":"On 22,526 of 33,192 WR and MR rows, 67.9 percent, the test dissipates 6.25 times rated power for 5 seconds. A further 3,733 rows see 1 to 6.25 times. On 6,933 rows, 20.9 percent, it dissipates less than rated power, including every one of the 4,760 rows at 1 megohm and above.","visible":true},{"id":"faq-question-04","title":"Is the short time overload test a pulse rating?","content":"No. It states one voltage and 5 seconds, with no energy, current, pulse shape or repetition. We searched both sheets for pulse and surge language and found none for a resistor. The only peak current is the zero-ohm jumper table, with no duration printed beside 5 A, 3.5 A, 3 A or 2 A.","visible":true},{"id":"faq-question-05","title":"Can I use the 2.5 times rule to size a surge-tolerant resistor?","content":"Not from this test alone. The same formula gives 1,562.5 mW for a 10 kilohm 1/4 W 1206 and 16 mW for the same case at 10 megohm. For surge work ask Walsin for the anti-surge series data; we hold no datasheet for any anti-surge series and the export carries no pulse column.","visible":true},{"id":"faq-question-06","title":"Does the export state an overload voltage?","content":"No. We read the Rated Power column across the WR and MR rows and it holds watts only. The 10 chip resistor columns include no voltage, overload or derating field. The overload voltages come from page 3 of each approval sheet and exist only for the 5 sizes the sheets tabulate.”,”visible”:true}],”listStyle”:””,”titleWrapper”:”h3″,”titleCssClasses”:””,”contentCssClasses”:””,”sizeSlug”:””} –>

---