Walsin Technology (Walsin) specifies MLCC storage at 5–40 °C and 20–70% relative humidity,
and says the products should be used within 12 months upon receipt. Storage must be free of
dew condensation and of hydrogen sulphide, hydrogen sulfate, chlorine, ammonia and sulfur. A
dropped chip is scrap, not stock, and the 12-month window is a shelf life few distributors
quote.
Source: Walsin MLCC Application Guide,
January 2022, sections 1, 6, 8, 9, 10 and 11. Counts are measured from the 24,026 MLCC part
numbers held by Venatech Limited, an authorised Walsin distributor in Hong Kong.
What is the shelf life of an MLCC?
Walsin gives 12 months from receipt. Section 1 of the MLCC Application Guide states that the
products should be used within 12 months upon receipt, alongside the temperature and humidity
window. It is a single figure with no series exceptions and no distinction by case size,
dielectric or termination.
The clock starts at receipt, not at manufacture, so a stores system tracking only a manufacture
date cannot answer the question Walsin is asking.
| Walsin condition | Limit | Section |
|---|---|---|
| Storage temperature | 5 to 40 °C | 1 |
| Storage relative humidity | 20 to 70% | 1 |
| Use by | 12 months upon receipt | 1 |
| Dew condensation | Not permitted in storage or operation | 1 |
| Direct sunlight | Avoid | 1 |
Unique to Venatech’s data. Walsin publishes one shelf life figure — 12 months upon
receipt — applying uniformly to all 24,026 MLCC part numbers Venatech holds, with no series,
size or dielectric carve-out. Most distributor listings quote no shelf life at all.
What temperature and humidity should MLCCs be stored at?
5 to 40 °C and 20 to 70% relative humidity, with no dew condensation. Both bounds are real
limits, not just an upper one: 5 °C is the floor and 20% is the dry limit. Walsin also asks
for damp-proof countermeasures wherever conditions could cause condensation.
Walsin sets 20% as a floor rather than treating dry storage as automatically safe. In a humid
climate the 70% ceiling is harder to hold, and that is where the condensation risk lives.
Walsin separately rules out storage under high humidity and under both high and low atmospheric
pressure.
Section 8 adds two conditions for mounted parts. Do not bend or distort the board after
soldering. And check functional-test pin pressure: pins set high to avoid intermittent contact
bend the board, cracking the chip. Where board flex rather than storage is the concern, see
Soft termination MLCC: SH, SG, ST and VT.
Which atmospheres damage a stored MLCC?
Walsin names five in section 1: hydrogen sulphide, hydrogen sulfate, chlorine, ammonia and
sulfur. Section 5-1-3 adds ozone, ultraviolet rays and radiation, and names sulfur dioxide
alongside the others. All of them attack the termination rather than the ceramic, and none
carries a published exposure limit.
| Atmosphere Walsin names | Where it comes from in practice |
|---|---|
| Hydrogen sulphide | Rubber, vulcanised packaging, sewage plant, geothermal |
| Hydrogen sulfate | Acid process areas, battery rooms |
| Chlorine | Cleaning chemicals, coastal and pool environments |
| Ammonia | Refrigeration plant, cleaning chemicals, agriculture |
| Sulfur and sulfur dioxide | Diesel exhaust, industrial flue gas, some rubbers |
| Ozone, ultraviolet, radiation | Corona from nearby HV gear, direct sun, sterilisers |
This is a storage-area risk as much as an application risk: sulphur-bearing rubber matting and
packaging foam in the same room as open reels is a common source. Walsin’s answer to sulphur in
chip resistors is an anti-sulfuration construction, and no comparable MLCC series exists in the
24,026-part extract.
What happens if I drop an MLCC?
Scrap it. Section 9 is unambiguous: if dropped, the chip capacitor may crack, and once dropped
it should not be used. Walsin adds that this is especially true for large case sized chips. The
same section warns against piling up populated boards, because one board’s corner can strike a
chip on another.
A crack from a drop is invisible. The part measures correctly, passes in-circuit test, and fails
weeks later as moisture lowers the insulation resistance. Section 5-2-3 asks for a fuse where a
shorted capacitor could cause fire. “Large case size” is worth quantifying, because Walsin does
not.
| Case size | Parts held | L x W (typical, mm) | Drop risk per Walsin section 9 |
|---|---|---|---|
| 1808 | 419 | 4.50 x 2.00 | Named — large case size |
| 1812 | 1,020 | 4.50 x 3.20 | Named — large case size |
| 1825 | 137 | 4.60 x 6.30 | Named — large case size |
| 2211 | 57 | 5.70 x 2.80 | Named — large case size |
| 2220 | 327 | 5.70 x 5.00 | Named — large case size |
| 2225 | 141 | 5.70 x 6.30 | Named — large case size |
| Total at 1808 and above | 2,101 | — | 8.7% of the MLCC extract |
Unique to Venatech’s data. 605 of the 24,026 Walsin MLCC parts sit at 1825, 2220 or 2225,
but only 501 are in Walsin’s “Big sizes Caps 1825 2220 2225” series. The other 104 come from
three series: 74 soft termination SH, 23 S2 safety certificated, 7 automotive ST. Filtering on
the “Big sizes” name misses 17% of the parts the drop rule covers.
Two real parts show why the series filter is the wrong tool.
| Field | 2220B102K402 |
SH55B474K631 |
Match / mismatch |
|---|---|---|---|
| Case size | 2220 | 2220 | Match |
| Dielectric | X7R | X7R | Match |
| Body, L x W x T | 5.70 x 5.00 x 2.00 mm | 5.70 x 5.00 x 2.00 mm | Match |
| Tolerance | +/-10% | +/-10% | Match |
| Capacitance | 1000 pF | 470 nF | Mismatch |
| Rated voltage | 4000 Vdc | 630 Vdc | Mismatch |
| Walsin series | Big sizes Caps 1825 2220 2225 | Soft Termination (SH, Ag-poly) | Mismatch — different filter |
| Section 9 large-case drop rule | Applies | Applies | Match |
| Section 11 low-pressure flashover | Primary concern at 4000 Vdc | Lower concern at 630 Vdc | Mismatch |
Identical case size, body and drop rule; only one appears under the “Big sizes” filter.
What are the transport limits for an MLCC?
Four climatic numbers and two mechanical conditions, in section 10. Low air temperature -40 °C.
Change of temperature air to air -25 °C to +25 °C. Low air pressure 30 kPa. Change of air
pressure 6 kPa per minute. Boxes must not deform and force must not reach the inner packaging,
which rules out heavy stacking.
| Transport condition | Walsin limit | What it constrains |
|---|---|---|
| Low air temperature | -40 °C | Unheated air freight hold, winter road |
| Change of temperature, air to air | -25 °C / +25 °C | Hold to apron, cold chain break |
| Low air pressure | 30 kPa | Cabin or hold altitude |
| Change of air pressure | 6 kPa/min | Climb and descent rate |
| Box deformation | Not permitted | Stacking and strapping in transit |
| Force on inner packaging | Not permitted | Outer box crush reaching the reel |
The transport floor is far below the 5 °C storage floor, but the air-to-air change is capped at
a 50 °C span — what a pallet sees coming off an aircraft into a humid apron. That transition is
where condensation forms, and section 1 prohibits condensation. Section 10 also bars sharp-edged
impact from an air driver, an iron, tweezers or a chassis.
Does altitude affect an MLCC?
Yes, in two ways, both in section 11. As atmospheric pressure drops, the risk of a flashover
between the capacitor terminations increases. And heat transfer degrades, so heat generated at
the terminations cannot be dissipated, which leads to overheating and eventual failure.
The flashover mechanism scales with working voltage, so the high-voltage parts matter most.
| Rated voltage band | Parts held | Relevance to section 11 flashover |
|---|---|---|
| 500 Vdc and above | 4,126 | Flashover risk rises with reduced pressure |
| 1000 Vdc and above | 2,014 | Primary concern at altitude |
| 2000 Vdc and above | 1,089 | Highest concern |
| 4000 Vdc and above | 128 | Confirm creepage and clearance with Walsin |
1825N100J402 is one of the 4000 Vdc parts, an 1825 NPO part at 10 pF. S242B101K502 is a
5000 Vdc safety certificated S2 part at 1808, 100 pF. Above roughly 3,000 m, raise these lines
with Walsin rather than derating by judgement.
Can I still use MLCCs that have been in stock longer than 12 months?
Walsin does not say the parts are unusable; it says they should be used within 12 months of
receipt. Beyond that the position is a quality decision, not a published limit, and it needs
electrical and solderability evidence rather than an assumption in either direction.
What to do with aged stock, in order. Check the goods-in date. Inspect the reel seal and any
desiccant. Look at the terminations under magnification for discolouration, the signature of
sulphur attack. Then run solderability and capacitance checks on a sample.
One further effect applies to Class II parts, which lose capacitance logarithmically with time
after firing: a long-stored X7R or X5R part reads lower than a fresh one until it is reflowed.
| Dielectric group | Parts held | Time-dependent capacitance drift |
|---|---|---|
| NPO and X8G | 15,546 | No — Class I, temperature stable |
| X7R, X5R, X6S, X7S, X7T, X8R, Y5V | 8,479 | Yes — Class II ages after firing |
What is the full MLCC storage and handling checklist?
Eleven checks, each traceable to a numbered section of Walsin’s application guide. Six belong to
stores and goods-in; five belong to the line and the process document. Run the stores checks
against the area once, then against every incoming batch.
- Storage temperature 5 to 40 °C. Section 1.
- Storage humidity 20 to 70% RH, damp-proof where condensation is possible. Section 1.
- No dew condensation, in storage or operation. Section 1.
- No direct sunlight on stored reels. Section 1.
- Atmosphere free of hydrogen sulphide, hydrogen sulfate, chlorine, ammonia, sulfur.
Section 1. - Goods-in date recorded, 12-month use-by tracked from it. Section 1.
- Dropped loose chips scrapped, tighter at large case sizes. Section 9.
- Populated boards not stacked. Section 9.
- Transport within -40 °C, a -25/+25 °C air-to-air change, 30 kPa and 6 kPa/min.
Section 10. - No sharp-edge impact from air drivers, irons, tweezers or a chassis. Section 10.
- Clean no sooner than 5 minutes after reflow; ultrasonic within 20 W/L, 40 kHz, 5
minutes. Section 6.
The process side is in
MLCC reflow profile and mounting. Walsin’s MLCC range
is at Walsin MLCC.
FAQ
What is the shelf life of a Walsin MLCC?
12 months upon receipt. Section 1 of Walsin’s MLCC Application Guide states that the products should be used within 12 months upon receipt, and applies the same figure across the whole MLCC range with no series, size or dielectric exception. The clock starts at goods-in, not at manufacture.
What temperature should MLCCs be stored at?
Between 5 and 40 °C. Walsin gives both a floor and a ceiling, and pairs them with a 20 to 70% relative humidity window and a prohibition on dew condensation. Transport may be colder, down to -40 °C, but the air-to-air temperature change is capped at a -25 °C to +25 °C span.
What humidity is safe for MLCC storage?
20 to 70% relative humidity. The lower bound is a real limit, not an open end. Walsin also requires damp-proof countermeasures wherever conditions can cause condensation, and separately prohibits use under high humidity. In a humid climate the 70% ceiling is the harder one to hold.
Can I use an MLCC that has been dropped?
No. Walsin’s section 9 states that a dropped chip capacitor may crack and that once dropped it should not be used, especially at large case sizes. A crack from a drop is invisible and passes electrical test, then fails later as moisture lowers the insulation resistance. Scrap it.
Which gases damage MLCCs in storage?
Walsin names hydrogen sulphide, hydrogen sulfate, chlorine, ammonia and sulfur in section 1, and adds ozone, ultraviolet rays, radiation and sulfur dioxide in section 5-1-3. They attack the terminations rather than the ceramic. There is no anti-sulfuration MLCC series in Walsin’s catalogue.
What are the MLCC transport limits?
Low air temperature -40 °C, change of temperature air to air -25 °C to +25 °C, low air pressure 30 kPa and change of air pressure 6 kPa per minute. Mechanically, transport boxes must not deform and forces must not pass through to the inner packaging. Section 10 of the application guide.
Does high altitude affect an MLCC?
Yes. Walsin’s section 11 states that as atmospheric pressure drops the risk of flashover between the capacitor terminations increases, and that degraded heat transfer at altitude can leave termination heat undissipated and cause failure. 2,014 of the 24,026 Walsin MLCC parts Venatech holds are rated 1000 Vdc or above.
Do MLCCs lose capacitance while they sit in stock?
Class II dielectrics do. X7R, X5R, X6S, X7S, X7T, X8R and Y5V lose capacitance logarithmically after firing until the part is reflowed; NPO and X8G do not. 8,479 of the 24,026 parts Venatech holds are Class II and 15,546 are Class I. Walsin publishes no ageing rate.
Next step
If a reel has aged past 12 months, a stores area sits above 70% RH, or a build is going to
altitude, the question is which parts are affected. Send the part numbers and Venatech Limited,
an authorised Walsin distributor in Hong Kong, will return the case size, rated voltage,
dielectric class and whether the large-case drop rule applies.
Send your BOM to Venatech · Browse
Walsin MLCC · Read
MLCC reflow profile and mounting and
Soft termination MLCC: SH, SG, ST and VT.
Cross it yourself. The cross-reference tool takes a single part number or a whole BOM column and returns the Walsin candidates with every field that differs stated plainly — qualification stays with you. Ready stock shows what is held in Hong Kong today, with an RFQ against any line.