Safety MLCC Reliability Tests: Walsin’s S2 and S3 Sheets List 17, S2-H Lists 19, and 7 of 12 Size-Keyed Pass Levels Fit No Part in the Series

Walsin Technology (Walsin) prints three different sets of safety MLCC reliability tests. We opened all three sheets: S2 and S3 list 17 tests each, S2-H lists 19, and of the 12 tests S2 and S2-H both state, only 4 share a condition. Seven of 12 size-keyed pass levels apply to sizes the series never makes.

Venatech Limited, an authorised Walsin distributor in Hong Kong, holds the three approval sheets for Walsin’s X1/Y2 and X2 safety MLCC range: S2 (dated April 2026), S3 (April 2026) and S2-H (May 2026). Together they run to 38 pages. This post is written from section 9 of each PDF, read line by line, and from the 173 S2 rows in the parametric export. Every part number below is real. Of the 28 Walsin datasheets we hold, these are the three where a wrong assumption about a test condition ends up in a supplier-approval file.

How many reliability tests does each Walsin safety MLCC sheet list?

The S2 and S3 sheets list 17 numbered tests each and the S2-H sheet lists 19. We counted the numbered rows in section 9 of each PDF: S2 is a 14-page sheet, S3 and S2-H are 12 pages each. The counts look close and the lists are not. S2-H follows the AEC-Q200 test order and folds capacitance, dissipation factor, insulation resistance, voltage proof and temperature coefficient into one “Electrical Characterization” row.

S2 and S3 give each of those five its own row, which is why the two lists are 17 long while covering less ground. S2-H adds seven tests that S2 never states: destructive physical analysis, ESD, moisture resistance, thermal shock, resistance to solvents, mechanical shock and beam load. S2 states one row that S2-H does not carry as a row: impulse voltage. S2-H states impulse only as three pulses applied before its endurance test.

Read the S2 sheet, the S3 sheet and the S2-H sheet against each other and you are not comparing three copies of one table.

Which tests do the S2 and S2-H sheets state with the same condition?

Four of twelve. Twelve tests appear in both the S2 and the S2-H sheet, once the five folded electrical tests are counted as voltage proof. We compared the condition and the pass limit of each. Visual examination, voltage proof, soldering heat and passive flammability match. The other eight differ in at least one stated condition.

The humidity row is the one that bites. S2 and S3 test at 40 °C; S2-H tests at 85 °C and 85% RH for twice as long, with a bias applied. A buyer who writes “damp heat per the Walsin safety sheet” into a specification has named three different tests. The same split is counted across the whole corpus in our damp heat post, and the cycle-count split in our temperature cycling post.

How does the S3 sheet differ from S2?

In 6 of 17 rows. We extracted the section 9 text of both PDFs and diffed it. Eleven rows are word-for-word the same condition; six differ because S3 is an X2 sheet and S2 is an X1/Y2 sheet. The six are dissipation factor, voltage proof, humidity, active flammability, endurance and impulse voltage.

• Dissipation factor. S3 adds a de-ageing step (150 °C for 1 h, then 24 ±2 h at room temperature) before the Class II measurement. S2 does not state it.
• Voltage proof. S3 states 1,075 Vdc for the X capacitor only. S2 adds 1,333 Vdc, a 2,000 Vac Y-capacitor test and two series-specific levels.
• Humidity. S3 applies 250 Vac. S2 applies “rated voltage” and prints its Class II recovery time as “48± hrs” with no tolerance; S3 prints 48 ±4 h.
• Active flammability. S3 uses Ui 2,500 V. S2 uses Ui 5,000 V.
• Endurance. S3 applies a 2.5 kV impulse three times first; S2 applies 5.0 kV or 6.0 kV. S3 stops at 312.5 Vac; S2 also lists 387.5 Vac and a 2,550 Vdc line for UL and TUV certified products.
• Impulse voltage. S3 is X2 at 2.5 kV; S2 is X1 at 4.0 kV and Y2 at 5.0 kV. Both cap the count at 24.

If your drawing says X2, you are on S3. If it says X1 or Y2, you are on S2. For the class decision itself, see X1/Y1 versus X1/Y2 safety capacitors.

Which voltage-proof level applies to which real S2 part number?

It depends on the first five characters of the part number. The S2 sheet prints a base voltage-proof test and then two exceptions keyed to named prefixes. We parsed all 173 S2 export rows by prefix and dielectric letter. 86 rows (49.7%) sit under a named exception and 87 sit under the base test alone.

Of the three levels the sheet labels, two are internal validation by Walsin and one is validation by UL. The export column that would let a buyer filter on this does not exist: Series, Size, Dielectric and Rated Voltage are there, and the prefix is only inside the part number. The S2-H sheet names the same prefixes and adds a separate S242B line at 3,000 Vdc for 60 s. The export holds no row tagged S2-H, so from the export alone we cannot tell you which of the 173 parts is an S2-H part. That question is on our request list for Walsin.

The 5,000 Vdc that the export shows as “Rated Voltage” on 163 of these rows is the impulse voltage, not a working voltage; we published that defect in the 173-row S2 post.

Which size-keyed pass levels apply to no part in the series?

Seven of twelve. Several test levels in the safety sheets are keyed to chip sizes that these series do not make. The cover line of all three sheets reads 1808 to 2220 sizes, and nothing smaller. We counted 12 size-keyed values across the three sheets; 7 apply to no chip the series offers. We have not seen this counted anywhere.

The pass level that governs a 1808 part is the 17.7 N adhesive force and one of the two long-chip beam loads. The rest apply to no chip in these series. That is harmless to the part and it matters to your paperwork: a qualification plan that copies “5 N for 0603” from an S2-H sheet into a safety-capacitor report cites a force no S2-H chip is ever tested at. The same size-keyed pattern drives our count of adhesive strength across 24 sheets.

What should a safety buyer ask for before accepting a test claim?

Ask which of the three sheets governs the part number, and ask for it by revision date. Three facts from our count decide that. S2 has 173 export rows. S2-H and S3 have none, so the free cross-reference tool cannot offer either. And no AEC-Q200 qualification report for S2-H is in the documents we hold.

We hold 28 Walsin datasheets, 451 pages, and send the one covering your part number on request. For what is physically on the shelf in Hong Kong, see ready stock: 1,125 part numbers as at 23 September 2026, a dated snapshot and not a live feed. The chip capacitor range sits on the MLCC page. Qualification stays with you. Confirm against both datasheets and qualify in your own circuit.

The short version

Walsin’s safety MLCC reliability tests come in three lists: 17 on S2, 17 on S3, 19 on S2-H. Of 12 tests that S2 and S2-H both state, 4 share a condition and 8 do not; humidity alone is 40 °C for 500 h on one and 85 °C and 85% RH for 1,000 h on the other. S3 differs from S2 in 6 of 17 rows. Of 173 S2 export rows, 86 carry a prefix-keyed extra voltage-proof level of 3,000 or 4,000 Vdc. Seven of 12 size-keyed pass levels in the three sheets apply to no chip in the series.

Send us the safety capacitor part number on your approved vendor list and the test conditions in your specification, and we will tell you which Walsin sheet they came from. And a question back: if your specification says “damp heat per the manufacturer’s sheet”, which of the three are you actually qualifying to?

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