Short answer: a Walsin MLCC part number is read left to right in seven fields — size, dielectric, capacitance, tolerance, rated voltage, termination and packaging. 1206B104K500CT is a 1206 case, X7R dielectric, 100 nF, ±10%, 50 VDC, copper/nickel/tin termination, on a 7-inch reel.
The seven fields
Walsin uses a fixed-position code. Once you know the positions, any part number in the series decodes without a datasheet.
| Position | Field | Example | Means |
|---|---|---|---|
| 1 | Size (inch) | 1206 | 3216 metric |
| 2 | Dielectric | B | X7R |
| 3 | Capacitance | 104 | 10 × 104 pF = 100 nF |
| 4 | Tolerance | K | ±10% |
| 5 | Rated voltage | 500 | 50 VDC |
| 6 | Termination | C | Cu / Ni / Sn |
| 7 | Packaging | T | 7″ reel |
Size codes
The first field is the inch code; the metric equivalent is in brackets.
0201 (0603) · 0402 (1005) · 0603 (1608) · 0805 (2012) · 1206 (3216) · 1210 (3225) · 1812 (4532)
Dielectric codes
| Code | Dielectric | Class |
|---|---|---|
| N | NP0 (C0G) | Class I |
| B | X7R | Class II |
| X | X5R | Class II |
| S | X6S | Class II |
| A | X7S | Class II |
| F | Y5V | Class II |
Capacitance code
Two significant digits followed by the number of zeros, in picofarads. R takes the place of a decimal point for values below 10 pF.
0R5= 0.5 pF1R0= 1.0 pF101= 100 pF102= 1,000 pF (1 nF)104= 100,000 pF (100 nF / 0.1 µF)106= 10,000,000 pF (10 µF)
Tolerance codes
Note that the code set splits: small capacitance values use absolute tolerances in picofarads, larger values use percentages. This catches people out when filtering a catalogue.
| Code | Tolerance |
|---|---|
| A | ±0.05 pF |
| B | ±0.1 pF |
| C | ±0.25 pF |
| D | ±0.5 pF |
| F | ±1% |
| G | ±2% |
| J | ±5% |
| K | ±10% |
| M | ±20% |
Rated voltage codes
Same convention as capacitance — two significant digits plus the number of zeros, with R as the decimal point.
4R0 = 4 VDC · 6R3 = 6.3 VDC · 100 = 10 VDC · 160 = 16 VDC · 250 = 25 VDC · 350 = 35 VDC · 500 = 50 VDC · 101 = 100 VDC
This is the field that most often gets misread. 101 in the voltage position is 100 volts, not 101 volts — and 500 is 50 volts, not 500.
Termination and packaging
C denotes copper / nickel / tin termination. For packaging, T is a 7-inch reel and G is a 13-inch reel. Reel size changes the quantity per reel and therefore the minimum order — always confirm it on the purchase order rather than assuming.
Worked examples
| Part number | Decodes as |
|---|---|
0603B104K500CT |
0603, X7R, 100 nF, ±10%, 50 V, Cu/Ni/Sn, 7″ reel |
0805N101J500CT |
0805, NP0 (C0G), 100 pF, ±5%, 50 V, Cu/Ni/Sn, 7″ reel |
1206B102K501CT |
1206, X7R, 1 nF, ±10%, 500 V, Cu/Ni/Sn, 7″ reel |
0805B105K160CT |
0805, X7R, 1 µF, ±10%, 16 V, Cu/Ni/Sn, 7″ reel |
Frequently asked questions
What does the B in a Walsin part number mean?
In the dielectric position (the character immediately after the size code), B means X7R. In the tolerance position it means ±0.1 pF. Position determines meaning — the same letter does different jobs in different fields.
Is NP0 the same as C0G?
Yes. NP0 is the older industry term (negative-positive-zero temperature coefficient) and C0G is the EIA designation. They describe the same Class I dielectric and are used interchangeably. Walsin codes it as N.
How do I tell 50 V from 500 V?
500 is 50 VDC — two significant digits (50) followed by zero zeros. 501 is 500 VDC. If a design calls for a high-voltage part, check this field character by character before releasing the order.
Does the reel size affect the minimum order quantity?
Yes. A 13-inch reel holds substantially more pieces than a 7-inch reel of the same part, so switching the packaging code changes both the MOQ and the standard pack quantity. Specify it explicitly on every RFQ.
Venatech Limited is an authorised distributor of Walsin passive components. If you need a part decoded, cross-referenced or quoted, send us the part number and we will come back with availability and lead time.