An MLCC can be reflowed twice according to Walsin Technology (Walsin): the application guide recommends a two-pass limit, and it is the only file of 26 that does. One sheet, the large-size 1825, 2220 and 2225 sheet, conditions samples with 3 cycles. The other 24 files state no number, and every sheet tests a single solder exposure.
Venatech Limited, an authorised Walsin distributor in Hong Kong, holds 28 Walsin datasheets, 451 pages in all. This post is written from the 26 MLCC files in that set: 24 series approval sheets, the full catalogue and the 12-page application guide (Jan. 2022), read against the 24,026-row parametric export. We searched every page for twice, two times, cycles, once and rework, and then read the soldering heat row of every sheet. Every part number below is real. The question is what a process engineer asks on a board that reflows on both sides and then needs one repair: what, in Walsin’s paper, supports the second pass?
How many Walsin MLCC files say how many times a part may be reflowed?
Two of 26. We opened each file and searched every page. The application guide says “Two times limitation for reflow soldering will be recommended” and the large-size sheet says to subject the sample to “3 cycle of the appropriate reflow conditions”. The other 24 files, including the 65-page catalogue and 23 series sheets, contain no reflow count. The guide reaches all 24,026 export rows; the large-size sheet reaches 501.
| What the file says about reflow passes | Files | Which | Export rows | Example part | Match / mismatch against the guide |
|---|---|---|---|---|---|
| Two times limitation, recommended | 1 | 00_MLCC_Application_Guide.pdf, clause 5-5 |
all 24,026 | 0603B104K500 |
reference |
| Sample subjected to 3 cycles of the reflow conditions, 15 minutes to 4 hours after removal from the chamber | 1 | 03_Large_Size_1825_2220_2225.pdf, page 9 |
501 | 1825B224K631 |
Mismatch — 3 against 2, and a different kind of statement |
| One heat exposure in the soldering heat row, no count of passes | 23 | every other series sheet, 01 to 24 less 03 | 23,525 | SH21B103K500 |
Mismatch — silent on passes |
| Heat row copied from the sheets, no count of passes | 1 | the full catalogue | all 24,026 | MT21B103K500 |
Mismatch — silent |
The guide is MLCC_application_guide.pdf and the large-size sheet is WTC_MLCC_1825_2220_2225.pdf. We have not seen this counted anywhere: the two numbers a reader can find, 2 and 3, sit in two files that together reach 24,026 rows, and in no series sheet outside the large-size one.
Do the guide’s two passes and the sheet’s three cycles contradict each other?
Not on their face, because they are different statements. The guide gives a recommendation for production. The sheet sets a test condition for the sample in a moisture-classification procedure that cites IPC/JEDEC J-STD-020D. A part that survives 3 conditioned cycles in a classification test is not thereby cleared for 3 production passes, and the sheet does not say it is. A reader still holds two numbers for one 2220 part, such as 2220B102K102, and neither file tells him which governs.
The guide also lists “Solder repair by solder iron” in clause 5-6, separately from clause 5-5, and does not say whether a repair counts toward the two. We read both clauses twice. They are adjacent and they are silent on one another. That is the question a rework line asks first.
How many solder exposures does the soldering heat test give a sample?
One, on every sheet. We read the soldering heat row of all 24 sheets and counted what each exposes the sample to. Twenty-one sheets dip the sample once for 10 ±1 seconds at 260 ±5 °C, the FT sheet dips once at 270 ±5 °C, and the two Mega Cap sheets reflow once at a 260 ±5 °C peak. The S2-H sheet prints both a dip and a reflow line and carries a Mega Cap note although it covers no Mega Cap part.
| Test exposure printed | Sheets | Which | Export rows | Example part | Match / mismatch against a two-pass recommendation |
|---|---|---|---|---|---|
| One dip, 260 ±5 °C, 10 ±1 s | 21 | 01 to 21, including S2-H | 24,018 | 0603B104K500 |
Mismatch — one exposure tested, two recommended |
| One dip, 270 ±5 °C, 10 ±1 s | 1 | 22 Feed Through FT | 8 | FT21B103M500 |
Mismatch — hotter, still one |
| One reflow, peak 260 ±5 °C | 2 | 23 and 24 Mega Cap M and V | 0 | no export rows | Mismatch — one pass, and no part to cite |
The point is the count, not the table: a 10-second dip and a reflow pass are not the same thermal event, and a sheet that tests either has evidence for one exposure. The second pass rests on the guide alone.
We checked the dip against the guide’s other numbers. The guide limits the temperature difference by case size and gives no peak; the sheets give 260 °C and no pass count. Neither document can be read as a profile for two passes without the reader supplying the profile. For the preheat side of that profile see our post on the MLCC preheat limit.
Which sheets state a leaching limit after that one exposure?
Fifteen of 24. After the dip, 15 sheets print “25% max. leaching on each edge” as a pass criterion, and the other 9 do not. The 15 are sheets 01 to 08, 10, 14, 15 and 19 to 22; they belong to 13 export series and 21,559 rows. The 9 without it are RT, MT, ST, VT, the three safety sheets and the two Mega Cap sheets, and the three that reach the export hold 2,467 rows: MT 2,176, ST 118 and S2 173.
| Sheet group | Sheets | Leaching limit printed | Export rows | Example part | Match / mismatch against General Purpose |
|---|---|---|---|---|---|
| General Purpose, Ultra-small, Large, Middle and High Voltage | 4 | 25% each edge | 13,380 | 0805B101K251 |
Match |
| Microwave RF, UF, High Q HH | 3 | 25% each edge | 5,609 | RF03N0R1A250 |
Match |
| MG, HT | 2 | 25% each edge | 916 | MG21B103K500 |
Match |
| Soft termination SH and SG, Low Profile TT, Feed Through FT | 4 | 25% each edge | 1,654 | SG21B103K500 |
Match |
| Surface Coating 05, RH 07 | 2 | 25% each edge | 0 | no series of their own | Match, no parts |
| AEC-Q200 form: MT, ST, VT, RT | 4 | none; capacitance, Q or D.F., I.R. only | 2,294 | MT21B103K500 |
Mismatch — criterion absent |
| Safety S2, S2-H, S3 | 3 | none; a sentence on leaching resistance in the description | 173 | S242B101K502 |
Mismatch — claim, no limit |
| Mega Cap M and V | 2 | none | 0 | no export rows | Mismatch |
We summed the rows ourselves: the first four groups come to 13,380 + 5,609 + 916 + 1,654 = 21,559, the next three to 2,467, and the two together to 24,026. The sheets do not say what the 25% is a percentage of, and the guide, which advises on solder quantity in clause 5-4, does not mention leaching at all. The ST sheet, ST21B103K500, and the SH sheet, SH21B103K500, are the same soft-termination idea with one criterion between them that the other lacks.
What should a double-sided board file attach?
The guide’s clause 5-5, the series sheet’s soldering heat row, the large-size sheet’s page 9 for any 1825, 2220 or 2225, and Walsin’s written answer on three questions: whether a repair counts toward the two passes, whether the 3 cycles is a ceiling, and what the 25% leaching limit is a percentage of. We hold 28 datasheets, 451 pages, and send the file for your part number on request. The MLCC range page lists the series, and our post on reflow profile and mounting covers the guide’s other clauses.
Our free cross-reference tool tells you which series a candidate belongs to, and therefore which of these rows applies. Ready stock shows what is held in Hong Kong as at 23 September 2026. Qualification stays with you: your own board, paste and number of passes decide whether the part passes. Confirm against both datasheets and qualify in your own circuit.
The short version
One file in 26 recommends a reflow limit, two passes; one sheet conditions samples with 3 cycles; 24 files say nothing. Every one of the 24 sheets tests a single solder exposure, so the second pass rests on the guide alone. A 25% leaching limit follows that exposure on 15 sheets covering 21,559 rows and is absent from 9 sheets, including MT, ST and S2, which hold 2,467 rows. Nothing printed says whether a repair counts as a pass.
Send us the part numbers on your BOM and we will tell you which sheet and which heat row applies to each. And a question back: if your board needs a third pass, whose paper is it resting on?
Frequently asked questions
How many times can an MLCC be reflowed?
Walsin’s application guide recommends a two-times limit for reflow soldering. It is the only one of 26 MLCC files that states a limit as a recommendation. The large-size sheet mentions 3 cycles as a sample conditioning step. The other 24 files give no number.
Does a repair with a soldering iron count as one of the two passes?
The guide does not say. Clause 5-5 gives the two-times limit and clause 5-6 gives iron repair conditions, 350 °C maximum at 1206 or smaller and 280 °C at 1210 or larger. Neither clause refers to the other, so ask Walsin before counting a repair as zero or as one.
Why does the large-size sheet say 3 cycles when the guide says 2?
They are different statements. The sheet’s 3 cycles are conditions applied to a sample 15 minutes to 4 hours after it leaves a humidity chamber, citing J-STD-020D. The guide’s 2 is a production recommendation. The sheet does not say the 3 is a limit for users.
Do the Walsin soldering heat tests cover two reflow passes?
No. We read the soldering heat row of all 24 series sheets. Twenty-one dip the sample once for 10 seconds at 260 °C, the FT sheet dips once at 270 °C, and the two Mega Cap sheets reflow once at a 260 °C peak.
Which Walsin sheets state a solder leaching limit?
Fifteen of 24 print 25% maximum leaching on each edge. The MT, ST, VT, RT, three safety and two Mega Cap sheets do not, and MT, ST and S2 hold 2,467 of 24,026 export rows. The sheets do not say what the 25% is measured against.
Where do I get a reflow pass limit for my part?
From Walsin, in writing. We hold 28 datasheets, 451 pages, and send the sheet for your part number on request. Ask for the pass count, whether repair counts, and the profile it assumes, then validate on your own board.