# MEF/CL21X Series Compact Metallized Polyester Film Capacitors

> Compact epoxy-dipped metallized polyester (PET) film capacitors for bypass, coupling, filtering and low-pulse circuits. 50–100 VDC, 1 nF–1 µF.

- Series code: MEF/CL21X
- Product line: [Film capacitors](https://www.songtian-ste.com/en/products/film-capacitors/) › Metallized polyester (PET) film capacitors
- Part numbers: 266 · [part list (JSON)](https://www.songtian-ste.com/data/parts/mef-cl21x.json)
- Page: https://www.songtian-ste.com/en/products/film-capacitors/mef-cl21x/
- Chinese version: https://www.songtian-ste.com/zh/products/film-capacitors/mef-cl21x/
- [Ask AI about this series](https://www.songtian-ste.com/en/products/film-capacitors/mef-cl21x/?ask=Help%20me%20choose%20a%20part%20from%20the%20STE%20MEF%2FCL21X%20series.)

## Key specifications

| Parameter | Value |
| --- | --- |
| Rated voltage | 50 / 63 / 100 VDC |
| Capacitance | 1 nF–1 µF |
| Lead spacing | 5 / 7.5 mm |
| Dielectric | Metallized PET |
| Tolerance | ±5% / ±10% |
| Operating temperature | −40 °C to +125 °C |

## Engineering details

### Overview

Compact metallized polyester (PET) film capacitors with a non-inductive, self-healing winding and epoxy-resin dip coating, for bypass, blocking, coupling, filtering and low-pulse circuits. Rated 50, 63 and 100 VDC, 1 nF–1 µF, J ±5% or K ±10%. Lead spacing 5 mm up to 100 nF and 7.5 mm from 120 nF. Operating temperature −40 °C to +125 °C, with voltage derating at high temperature.

#### Series features

- Metallized PET film, non-inductive winding, compact epoxy-dipped body
- Rated 50 / 63 / 100 VDC; 1 nF to 1 µF
- Lead spacing 5 mm up to 100 nF; 7.5 mm from 120 nF to 1 µF
- Self-healing; operating temperature −40 °C to +125 °C

#### Typical applications

- Bypass, blocking and coupling in compact DC circuits
- Filtering and low-pulse circuits; validate dV/dt, current and temperature rise
- Timing and signal circuits; include PET dielectric absorption and drift in the error budget
- Dense radial-lead PCB assemblies; body size, lead form and packing vary by part number

### Specifications

|   |   |
| --- | --- |
| Product type | Compact metallized polyester DC film capacitor for bypass, blocking, coupling, filtering and low-pulse circuits; not a safety capacitor, not for reflow soldering |
| Construction | Metallized polyethylene terephthalate (PET) film · non-inductive winding · epoxy-resin dipped radial body |
| Rated DC voltage | 50 · 63 · 100 VDC |
| Capacitance range | 1 nF–1 µF (below 10 nF on request) |
| Capacitance values | 36 values at each of 50, 63 and 100 VDC |
| Capacitance tolerance | J ±5% · K ±10% |
| Operating temperature | −40 °C to +125 °C |
| Voltage derating | Required at high temperature; derating curve for operation above +85 °C on request |
| Climatic category | 40/100/21 |
| Storage temperature | +15 °C to +35 °C |
| Dissipation factor | tan δ ≤1.0% at 1 kHz, 1.0 Vrms, 20 °C |
| Insulation resistance, C ≤0.33 µF | ≥15,000 MΩ at 100 VDC, 60 s, 20 °C; test voltage for 50 and 63 VDC parts on request |
| Insulation resistance, C >0.33 µF | Time constant IR × C ≥5,000 s at 100 VDC, 60 s, 20 °C |
| Voltage proof, terminal to terminal | 1.6 × UR for 5 s |
| Pulse ratings | Designed for low-pulse duty; dV/dt, K0, peak and repetitive current, pulse energy and repetition rate on request |
| AC operation | DC-rated only; do not use in AC, resonant or capacitive-dropper circuits without frequency, current and lifetime data (on request) |
| Safety class | Non-safety product; no X/Y class and no agency approval. Do not use across the line or line to earth. |
| Coating | Epoxy resin |
| Body dimensions | W 7.3–10.5 · H 7.0–14.0 · T 3.5–9.5 mm; maximum values depend on voltage and capacitance |
| Lead spacing | 5.0 mm for 1–100 nF · 7.5 mm for 120 nF–1 µF · ±1.0 mm |
| Lead diameter | 0.5 ±0.05 mm at 5 mm spacing · 0.6 ±0.05 mm at 7.5 mm spacing |
| Lead forms and packing | Long straight · inner-bent · straight taped · bent taped |
| Taping | Tape dimensions specified for 5 and 7.5 mm lead spacing |
| Soldering profile, PP | Preheat ≤110 °C · soldering ≤120 °C · ≤15 s |
| Soldering profile, PE | Preheat ≤125 °C · soldering ≤160 °C · ≤15 s |
| Hand soldering | 350 °C max. · 3 s max. · ≥2 mm from the coating |
| Reflow soldering | Not permitted; film shrinkage can degrade performance |
| Environmental compliance | RoHS and REACH compliant; bromine-free and halogen-free. Material declarations on request. |
| Further data | On request: clearing energy, capacitance loss and end-of-life limits · storage humidity and shelf life · ESR, thermal resistance, hot-spot rise and lead-temperature limits · ESL, impedance, self-resonance, permissible voltage and current versus frequency, dielectric absorption and drift · flame class · loaded-life, thermal endurance, pulse-life, damp-heat, overload, thermal-cycle, vibration and lead-strength test results |

### Variants

Ranges by dielectric, package and lead style within this series.

| Variant | Body dimensions | Rated voltage / capacitance | Dielectric / tolerance / coating | Lead / land pattern | Notes |
| --- | --- | --- | --- | --- | --- |
| D · 5 mm | W 7.3–7.5 · H 7.0–9.5 · T 3.5–4.5 mm | 50 / 63 / 100 VDC · 1–100 nF | Metallized PET · J/K · epoxy dipped | P 5.0 ±1.0 · d 0.5 ±0.05 mm | Compact size up to 100 nF; higher values at 5 mm lead spacing on request. |
| J · 7.5 mm | W 7.5–10.5 · H 7.5–14 · T 4–9.5 mm | 50 / 63 / 100 VDC · 120 nF–1 µF | Metallized PET · J/K · epoxy dipped | P 7.5 ±1.0 · d 0.6 ±0.05 mm | Higher capacitance, 120 nF–1 µF. Availability on request. |

### Selection guide

Start with the space constraint and the duty: filtering or low pulse. Then check voltage, capacitance, frequency loss, pulse current, dielectric drift, temperature derating, self-heating of the compact body, lifetime and dimensions.

1. **Define waveform, stability and space constraints**
   Specify DC bias, AC ripple, frequency spectrum, peak voltage, rise and fall time, dV/dt, repetition rate, RMS current, allowed drift or absorption error, ambient temperature, board spacing, cooling and service hours.
2. **Select voltage, capacitance and lead spacing**
   The series covers 50/63/100 VDC and 1 nF–1 µF, with 5 mm lead spacing up to 100 nF and 7.5 mm above. For higher voltages, other values, or values above 100 nF at 5 mm, request the part specification.
3. **Calculate pulse, loss and self-heating**
   Use Ipk = C·dV/dt and the measured spectrum, and check the result against the dV/dt, repetitive and RMS current, ESR, impedance, self-resonance, thermal-resistance and hot-spot data for the part (on request).
4. **Check derating and PET stability**
   Before operation above +85 °C, check the voltage–temperature derating curve, dielectric absorption, capacitance and loss versus temperature and frequency, drift and loaded-life data (on request).
5. **Confirm dimensions and assembly**
   Match the part number to voltage, capacitance, tolerance, W/H/T, lead spacing, lead form, packing, marking and soldering profile. Do not use reflow soldering; validate forming stress, cleaning, coating compatibility, vibration and thermal cycling.

### Design notes

#### Compact size has thermal and electrical tradeoffs

A 5 mm body saves board area but reduces the thermal surface and may change winding geometry. Verify current, ESR, hot-spot rise and lifetime for the selected capacitance and voltage.

#### Quantify low-pulse duty

“Low pulse” is qualitative. Calculate I = C·dV/dt and check it against the dV/dt, repetitive-current and temperature-rise limits for the part number.

#### Values below 10 nF

The ordering code and dimension table cover 1 nF to 1 µF. Check the availability of values below 10 nF before design-in.

#### Derating above +85 °C

For operation above +85 °C, use the voltage derating curve, case or hot-spot limit and loaded-life data for the part.

#### Values above 100 nF at 5 mm

The datasheet assigns values above 100 nF to 7.5 mm lead spacing. For parts above 100 nF with 5 mm lead spacing, request the body and winding drawing, loss and current data and qualification report.

#### Control heat and lead stress during assembly

Do not use reflow soldering. Follow the soldering profile, keep forming stress away from the epoxy interface, and validate cleaning, coating, vibration and thermal cycling.

### Part numbering

Example ordering code. Not every combination is available.

`LX · 1J · 104 · J · D · 1 · B0 · 073 · 095 · 045 · E · 0 · X`

| Code | Meaning |
| --- | --- |
| LX | Series code: MEF/CL21X |
| 1J | Rated voltage code: 1J = 63 VDC; 1H = 50 VDC, 2A = 100 VDC |
| 104 | Capacitance code: 104 = 100 nF; range 1 nF–1 µF |
| J | Capacitance tolerance: J = ±5%, K = ±10% |
| D | Lead spacing: D = 5 mm; J = 7.5 mm, used above 100 nF |
| 1 | Lead form: 1 = long straight, 2 = inner-bent, 5 = straight taped, 6 = bent taped |
| B0 | Lead length code: B0 = 20.0 mm |
| 073 | Body width: 073 = 7.3 mm |
| 095 | Body height: 095 = 9.5 mm |
| 045 | Body thickness: 045 = 4.5 mm |
| E | Environmental code: E = RoHS, F = RoHS and halogen-free |
| 0 | STE internal control code, first field |
| X | STE internal control code, second field |

## Datasheets & approval documents

- [Datasheet: MEF/CL21X series miniature encapsulated metallized polyester (PET) film capacitors — short-form datasheet (2023-10)](https://www.songtian-ste.com/documents/source-cn/%E9%87%91%E5%B1%9E%E8%86%9C%E7%94%B5%E5%AE%B9%E5%99%A8%E7%B3%BB%E5%88%97%E4%BA%A7%E5%93%81%E8%A7%84%E6%A0%BC%E4%B9%A6/MPE%E8%81%9A%E8%84%82%E8%86%9C%E7%94%B5%E5%AE%B9%E5%99%A8/%E5%B0%8F%E5%9E%8B%E5%8C%85%E5%B0%81%E9%87%91%E5%B1%9E%E5%8C%96%E8%81%9A%E9%85%AF%E8%86%9C%E7%94%B5%E5%AE%B9%E5%99%A8%28MEF%20CL21X%29%E7%AE%80%E7%89%88%E8%A7%84%E6%A0%BC%E4%B9%A6-202310.pdf) — PDF · Chinese · 2023-10 · 269 KB

## More in polyester (PET) film capacitors

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