When selecting film capacitors, 90% of engineers have been confused by the parameter table—what critical information is hidden in the string of code ECQ-E1274KZ? This article takes the Panasonic ECQ-E series as a sample to break down the film capacitor part numbering rules, core parameters, and selection points, helping you lock in the target specification in 3 minutes.
Basic Structure of ECQ-E Series Film Capacitors
The ECQ-E series consists of metallized polyester film capacitors, specifically designed for DC-Link, filtering, and coupling scenarios in electronic equipment. Its multi-layer wound structure combined with epoxy resin encapsulation allows it to operate stably for thousands of hours in a 105℃ environment.
Product Positioning and Application Scenarios
This series is mainly targeted at consumer electronics, industrial power supplies, and new energy fields. Typical applications include switching power supply input filtering, inverter DC-Link snubber circuits, LED driver circuits, and noise suppression in motor control systems. Compared with ceramic capacitors, film capacitors feature self-healing properties and a lower capacitance decay rate.
Packaging Forms and Lead Specifications
The ECQ-E is available in radial lead (Radial) and axial lead (Axial) packages. Radial lead pitch commonly comes in four options: 7.5mm, 10mm, 15mm, and 22.5mm, corresponding to different capacitance-rated voltage combinations. The lead material is tinned copper wire, with a diameter of 0.6mm-1.0mm, which can withstand a 260℃ wave soldering temperature.
In-Depth Breakdown of Part Numbering Rules: ECQ-E1274KZ
Taking ECQ-E1274KZ as an example, we parse the physical meaning of this 12-digit code digit-by-digit:
| Code Position | Character | Meaning |
|---|---|---|
| 1-3 | ECQ | Panasonic Film Capacitor Product Family |
| 4 | E | Polyester (PET) dielectric material |
| 5-6 | 12 | Package size code (12×7.5mm) |
| 7-9 | 274 | Capacitance code: 27×10⁴ pF = 0.27μF |
| 10 | K | Tolerance class: ±10% |
| 11-12 | Z3 | Rated voltage code: 100VDC (implied) |
Series Code and Dielectric Material Identification
In the ECQ series, the second letter determines the dielectric type: E = Polyester (PET), F = Polypropylene (PP), G = Polyphenylene Sulfide (PPS). Polyester dielectrics feature low cost and small size, suitable for general coupling; polypropylene dielectrics have a lower dissipation factor (tanδ ≤ 0.001), suitable for high-frequency, high-current scenarios.
Capacitance/Rated Voltage/Tolerance Code Analysis
The capacitance code uses a three-digit representation: the first two digits are significant figures, and the third digit is the power of 10. Thus, 274 is 27×10⁴ pF = 270nF = 0.27μF. Tolerance codes follow the EIA standard: J = ±5%, K = ±10%, M = ±20%. The rated voltage is typically not directly marked on the part number and needs to be verified by consulting the datasheet to confirm the rated voltage class.
Core Parameter Quick Lookup and Conversion
Capacitance Code Comparison Table (pF/μF Unit Conversion)
| Code | Formula | Nominal Capacitance |
|---|---|---|
| 103 | 10×10³ pF | 10nF / 0.01μF |
| 104 | 10×10⁴ pF | 100nF / 0.1μF |
| 224 | 22×10⁴ pF | 220nF / 0.22μF |
| 274 | 27×10⁴ pF | 270nF / 0.27μF |
| 474 | 47×10⁴ pF | 470nF / 0.47μF |
| 684 | 68×10⁴ pF | 680nF / 0.68μF |
| 105 | 10×10⁵ pF | 1.0μF |
Rated Voltage Class and Temperature Coefficient Matching
The ECQ-E series rated voltage covers 50VDC to 630VDC. During selection, a 20%-30% voltage derating must be reserved; that is, the actual working voltage of a 100V rated capacitor should not exceed 70-80V. Regarding the temperature coefficient, the polyester dielectric exhibits a negative temperature characteristic (-200±100 ppm/℃), and the capacitance drops by about 5%-10% at high temperatures.
Tolerance Accuracy Class and Application Selection
±5% (J class) is suitable for precision-sensitive scenarios such as oscillation circuits and timing circuits; ±10% (K class) is a general-purpose class, satisfying most filtering and coupling requirements; ±20% (M class) is only used in situations with loose accuracy requirements, such as power supply decoupling. The K-class positioning of ECQ-E1274KZ balances cost and performance.
Practical Selection Guide for Film Capacitors
Alternative Part Numbers Cross-Reference Methods
When ECQ-E is out of stock, alternatives can be found according to the following priority: first match the dielectric material (PET) and package size, then verify the capacitance-rated voltage-tolerance trio, and finally verify dynamic parameters such as ESR and ripple current. Potential alternative series include: TDK B32529, Vishay MKT368, KEMET R46, etc.
Parameter Priority in High-Frequency/Filtering/Coupling Scenarios
For high-frequency applications, priority should be given to ESR and Self-Resonant Frequency (SRF), where polypropylene dielectrics outperform polyester; filtering scenarios require calculating the ripple current rating to avoid thermal failure; coupling circuits focus on insulation resistance and dielectric absorption characteristics, and low leakage current specifications are recommended.
Common Selection Pitfalls and Reliability Verification
Voltage Derating Design Principles
For DC applications, it is recommended to derate to 70% of the rated voltage; for AC applications, both peak voltage and RMS voltage must be considered. In high-temperature environments (>85℃), it should be further derated to 50%-60%, or a product with a higher rated voltage class should be selected.
Prevention of Thermal Failure due to ESR and Ripple Current
Although the ESR of film capacitors is lower than that of electrolytic capacitors, it still generates significant thermal loss under high-frequency and high-current conditions. Calculate power dissipation P = I² × ESR to ensure the case temperature does not exceed the upper limit temperature (usually 105℃). It is recommended to measure the actual temperature rise of key nodes or select enhanced packages with thermal fuses.
Quick Glance at Key Points
- ECQ-E1274KZ Analysis: 0.27μF/100V/±10% polyester film capacitor, 12mm package
- Capacitance Conversion: Among the three-digit codes, the first two digits are significant figures, and the third is the power of 10 (unit: pF)
- Voltage Derating: Recommended ≤70% rated voltage for DC applications, and ≤50% for high-temperature scenarios
- Dielectric Selection: Polyester features low cost and high versatility, while polypropylene is suitable for high-frequency, low-loss scenarios
- Tolerance Matching: J class (±5%) for precision circuits, K class (±10%) for most filtering needs
Frequently Asked Questions
What specific capacitance value does the 274 code of ECQ-E1274KZ represent?
274 represents 27×10⁴ pF, which is 270000 pF, converted to 0.27μF or 270nF. This is a common three-digit coding rule for film capacitors, consistent with the identification method of SMD ceramic capacitors.
Can a film capacitor replace a ceramic capacitor of the same capacitance value?
A comprehensive evaluation is required. Film capacitors are superior to ceramic capacitors in terms of capacitance stability, voltage surge resistance, and self-healing properties, but they have a larger volume and slightly inferior high-frequency characteristics. The capacitance temperature drift of X7R ceramic capacitors can reach ±15%, while film capacitors are usually controlled within ±5%.
How to determine the actual rated voltage class of ECQ-E series capacitors?
The rated voltage information in the part number is usually implied in the datasheet; some manufacturers will mark it in the part number suffix. The "Z3" suffix of ECQ-E1274KZ corresponds to a 100VDC rated voltage. Be sure to check the official datasheet during selection, and do not infer solely from the part number.
How to quickly distinguish between polyester and polypropylene film capacitors?
Check the second letter of the part number: E stands for polyester (PET), F stands for polypropylene (PP). Although they are difficult to distinguish by appearance, polypropylene capacitors usually feature a lower dissipation factor (tanδ ≤ 0.001 vs 0.005) and superior high-frequency characteristics.
