MLCC Damp Heat Test: 6 of Our 28 Walsin Datasheets State 85 °C and 85 % RH. 21 State 40 °C.

An MLCC damp heat test at 85 °C and 85 % RH appears on 6 of the 28 Walsin datasheets we hold. 21 state 40 ± 2 °C at 90 to 95 % RH, and one states no humidity row. We read all 451 pages. The figure takes two values and nothing in between.

Venatech Limited, an authorised Walsin distributor in Hong Kong, holds 28 Walsin Technology (Walsin) datasheets — 451 pages, 26 multilayer ceramic capacitor documents and 2 chip resistor documents. We extracted the text of every page and read one thing: the humidity row. If you have ever assumed “85/85” is what a ceramic capacitor datasheet means by damp heat, this post is the correction, and it is drawn from Walsin’s own approval sheets rather than from habit. Every part number below is real.

How many of Walsin’s 26 MLCC datasheets state an MLCC damp heat test at all?

25 of 26. We checked all 26 and only 00_MLCC_Application_Guide.pdf, 12 pages, has no humidity row. The remaining 25 split into two regimes that do not overlap by a single degree. 20 sheets run a Damp Heat Steady State at 40 ± 2 °C, 90 to 95 % RH, 500 +24/−0 hours. 5 sheets run a Biased Humidity at 85 ± 3 °C, 85 % RH, 1,000 +24/−0 hours and no 40 °C row at all.

The split tracks one thing and one thing only: AEC-Q200. It does not track case size, rated voltage, dielectric or termination. The five MLCC sheets stating 85 ± 3 °C are 09_Microwave_Automotive_RT.pdf, 11_Automotive_MT.pdf, 12_Soft_Term_Automotive_ST.pdf, 13_Soft_Term_Automotive_VT_VW80808.pdf and 17_Safety_X1Y2_Automotive_S2_H.pdf — every AEC-Q200 sheet in the library and nothing else. The soft-termination SH and SG sheets, which share a construction with ST, sit on the 40 °C side because they are not automotive-qualified parts. See soft termination, SH, SG, ST and VT for what else moves across that boundary.

Which Walsin series actually state 85 °C and 85 % RH?

Five MLCC series and one resistor series, and they state it as Biased Humidity rather than damp heat. Page 17 of 11_Automotive_MT.pdf gives the full condition: 85 ± 3 °C, 85 % RH, 1,000 +24/−0 hours, referenced to MIL-STD-202 Method 103, with the bias applied as “rated voltage and 1.3~1.5Vdc (add 100k ohm resistor)”. The post-test limit is ±3.0 % or 0.30 pF for X8G and NP0, and ±12.5 % for X7R.

That is twice the hours at 45 °C more heat than the 40 °C sheets state, and it is the condition a tier-1 incoming-inspection plan is usually written against. The automotive sheets also add a second row the commercial sheets do not have: Moisture Resistance, MIL-STD-202 Method 106, at 25 to 65 °C and 80 to 100 % RH for 10 cycles of 24 hours each — 240 hours of cycling on top of the 1,000 steady hours.

The safety-certified automotive sheet is the outlier inside the outlier. Page 5 of 17_Safety_X1Y2_Automotive_S2_H.pdf states 85 ± 3 °C and 85 ± 5 % RH for 1,000 +24/−0 hours, with the bias as rated voltage up to a maximum of 500 Vdc plus 1.3 to 1.5 Vdc, and then adds 250 Vac on top. No other sheet in the library applies an a.c. bias during a humidity test.

Which real part numbers sit on which humidity condition?

Eight, from eight different approval sheets, every one present in our master part-number set. We measured each row against the hardest humidity condition in the library — 85 °C, 85 % RH, 1,000 hours under bias — and stated the differences field by field rather than calling anything a like-for-like swap.

Two rows carry a design consequence. FT21B103M500 is a three-terminal feed-through part used for supply filtering, and its sheet states a humidity test with no voltage on it; if you need a biased humidity result for that part, no page in our library gives you one. S242B101K502 is the safety-certified X1/Y2 part whose single humidity row permits a ±15 % Class II capacitance change — wider than the ±12.5 % on the general-purpose sheet, and stated against the safety standard rather than relaxed by Walsin.

What does the 40 °C steady-state damp heat row actually prove?

Moisture ingress at low stress over 500 hours, and nothing about 85 °C. On 17 of the 20 sheets at 40 °C the test appears twice: once unbiased as Humidity (Damp Heat) Steady State and once energised as Humidity (Damp Heat) Load, both at 40 ± 2 °C, 90 to 95 % RH, 500 +24/−0 hours, with rated voltage up to 500 V applied on the second. The acceptance widens on the biased row — page 16 of 01_General_Purpose.pdf states NP0 within ±5 % or 0.5 pF unbiased, and page 17 states ±7.5 % or 0.75 pF with voltage applied.

Three sheets state only one humidity row: 16_Safety_X1Y2_General_S2.pdf, 18_Safety_X2_S3.pdf and 22_Feed_Through_FT.pdf. The two safety sheets apply voltage to theirs — rated voltage on S2 and 250 Vac on S3 — so their single row is the biased case. The feed-through sheet applies none, so its single row is the unbiased case. Of the 25 MLCC sheets that state a humidity test, 24 state at least one biased humidity condition and exactly one does not.

If your product sees condensation, a 40 °C result is the wrong evidence to carry into a design review, and we would rather tell you that than let the row stand in for something it does not cover. Storage conditions are a separate question again — the sheets put those at 5 to 40 °C and 20 to 70 % RH, moisture sensitivity level 1, covered in MLCC shelf life, storage and handling.

Why does only one of the six 85 / 85 rows state a tolerance on the humidity?

Because four of them simply print 85%RH with no band at all. We read all six 85 °C rows in the library. Five of the six state the temperature as 85±3°C. Only one states a tolerance on the humidity: 17_Safety_X1Y2_Automotive_S2_H.pdf writes 85±5%RH. The four other MLCC sheets — RT, MT, ST and VT — write a bare 85%RH, and the MR resistor sheet writes 85% RH. We have not seen this counted anywhere.

That is not pedantry. A humidity chamber is specified and calibrated to a band, and an incoming-inspection plan written to “85 % RH” with no tolerance either invents its own band or argues about it at the audit. The same four sheets are precise to ±3 °C on temperature in the same sentence, so the omission is on the humidity axis only. The practical move is to ask Walsin which band applied, and to write the band you actually used into your own test record. For the automotive context around these four sheets, see automotive MLCC, MT against MG.

What should you ask for before you accept a humidity figure for your part?

The governing page, then the tolerance, then the stock position. Walsin’s humidity rows state a test, not a field lifetime, and the difference between 500 hours at 40 °C and 1,000 hours at 85 °C is the difference between two qualification arguments.

1. Ask which sheet and page govern your exact part number. We hold 28 Walsin datasheets, 451 pages. Ask for the one covering your part and it will be in your inbox, not in a brochure — and if no page covers it, you get that answer the same day.
2. Ask for the qualification report if the part is automotive. AEC-Q200 on the RT, MT, ST, VT and S2-H sheets is stated as compliant and qualified to, never certified, and we will not upgrade Walsin’s own word. The S2-H family also carries third-party certificate numbers you can check without asking us: UL file E182369, TUV R50381780 and R50195920.
3. Cross the whole list in one pass. Paste up to 500 part numbers or drop your Excel or CSV into the free cross-reference tool, filter for soft termination, high temperature or safety certified, and read every stated difference. Then check what is physically in Hong Kong on ready stock — 1,125 part numbers as at 23 September 2026, a dated snapshot and not a live feed. The lines sit on the Walsin MLCC and chip resistor pages.

The short version

Six of our 28 Walsin datasheets state 85 °C and 85 % RH; 21 state 40 ± 2 °C at 90 to 95 % RH; one states no humidity test. There is nothing in between, and the split tracks AEC-Q200 rather than case size, voltage or dielectric. The 40 °C regime runs 500 hours, the 85 °C regime runs 1,000 plus 240 hours of moisture cycling at 25 to 65 °C. Only one of the six 85 % RH rows states a tolerance on the humidity figure. Twenty-four of the 25 MLCC sheets state at least one biased humidity condition; the feed-through sheet states none. Qualification stays with you, and so does the chamber record — our job is to make sure the condition you qualify against is the one actually printed on the page that governs your part.

Send us the humidity-critical lines off your bill of materials and we will return the governing page, the exact temperature and humidity band, the hours and whether a bias was applied — including the lines where no page exists. And a question back: the last time a supplier told you a part was “85/85 qualified”, did you ask them for the page, or did you take the phrase?

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