What you should know about Ceramic Capacitors ?
Discover the basic information about ceramic capacitors, to improve your choice
▲ What you should know about Ceramic Capacitors ?
1. Materials expert
For 50 years and as a market leader, EXXELIA’s comprehensive knowledge of the materials properties and performances have enabled us to design capacitors in Porcelain, NPO, BX, 2C1, BP, X7R and –2200ppm/°C ceramics.
2. Custom Designs
Our catalog products don’t meet your application?
Based on the valuable experience accumulated over the design of 2,000+ specific ceramic capacitors, you can trust EXXELIA to define a qualitative custom solution in a time effective manner.
3. No Obsolescence
Choosing a standard or custom EXXELIA product means you won’t have to worry about obsolescence.
4. Typical Applications
- Aerospace & Defense: cockpit panels, flight control, radio systems, missile
- guidance systems…
- Space: military and commercial satellites, launcher…
- Medical: MRI, external defibrillators, implantable devices…
- Telecommunications: base stations…
- Oil and gas: drilling tools, MWD, LWD, wellheads…
5. ISO 9001 And AS9100C
Quality is at the core of Exxelia’s corporate culture. Each sites has its own certifications.
Capacitors manufactured by EXXELIA comply with American and European standards and meet the requirements of many international standards.
For Space qualified parts (ESA QPL), please refer to our catalog «Ceramic capacitors for Space applications».
7. Quality & Reliability
EXXELIA is committed to design and manufacture high quality and reliability products. The test cycles reproducing the most adverse operating conditions over extended periods (up to 10 000 hours) have logged to date well over 5.109 hours/°Component.
Failure rate data can be provided upon request.
8. Conflict minerals
EXXELIA is committed to an approach based on «Conflict Minerals Compliance». This US SEC rule demands complete traceability and a control mechanism for the mineral procurement chain, encouraging importers to buy only «certified» ore.
We have discontinued relations with suppliers that procure from the Democratic Republic of the Congo or an adjoining country.
EXXELIA is committed to applying a robust environmental policy, from product design through to shipment. To control its environmental footprint and reconcile this with the company’ functional imperatives, our environmental policy provides for the reduction or elimination of hazardous substances. We also focus on compliance with European Union directives and regulations, notably REACH and RoHS.
10. RoHS Compliancy
The capacitor terminations are generally protected by a nickel barrier formed by electrolytic deposit. This barrier gives chip capacitors leaching performance far exceeding the requirements of all applicable standards. The nickel barrier guarantees a minimum resistance to soldering heat for a period of 1 minute at 260°C in a tin-lead (60/40) or tin-lead-silver (62/36/2) bath without noticeable alteration to the solderability. It also allows repeated soldering-unsoldering and the longer soldering times required by reflow techniques.
However nickel barrier amplifies thermal shock and is not recommended for chip sizes equal or greater than CNC Y (30 30) - (C 282 to C 288 - CNC 80 to CNC 94).
As well as for SMD products, leaded capacitors ranges can also be RoHS. These products, which are characterized by the suffix «W» added to the commercial type, are naturally compatible with the soldering alloys used in RoHS mounting technology. The connections coating is generally an alloy SnAg (with a maximum of 4% Ag). However, on a few products that EXXELIA will precise on request, the coating is pure silver.
11. MLCC Structure
12. Equivalent circuit
Capacitor is a complex component combining resistive, inductive and capacitive phenomena. A simplified schematic for the equivalent circuit is:
13. Dielectric characteristics
Insulation Resistance (IR) is the resistance measured under DC voltage across the terminals of the capacitor and consists principally of the parallel resistance shown in the equivalent circuit. As capacitance values and hence the area of dielectric increases, the IR decreases and hence the product (C x IR) is often specified in Ω.F or MΩ.µF.
The Equivalent Series Resistance (ESR) is the sum of the resistive terms which generate heating when capacitor is used under AC voltage at a given frequency (f).
Dissipation factor (DF) is the ration of the apparent power input will turn to heat in the capacitor:
DF = 2π f C ESR
When a capacitor works under AC voltage, heat power loss (P), expressed in Watt, is equal to:
P = 2π f C Vrms2 DF
The series inductance (Ls) is due to the currents running through the electrodes. It can distort the operation of the capacitor at high frequency where the impedance (Z) is given as:
Z = Rs + j (Ls.q - 1⁄(C.q)) with q = 2πf
When frequency rises, the capacitive component of capacitors is gradually canceled up to the resonance frequency, where :
Z = Rs and LsC.q2 = 1
Above this frequency the capacitor behaves like an inductor.
SMD environmental tests
Ceramic chip capacitors for SMD are designed to meet test requirements of CECC 32100 and NF C 93133 standards as specified below in compliance with NF C 20700 and IEC 68 standards:
- Solderability: NF C 20758, 260°C, bath 62/36/2.
- Adherence: 5N force.
- Vibration fatigue test: NF C 20706, 20 g, 10 Hz to 2,000 Hz, 12 cycles of 20 minutes each.
- Rapid temperature change: NF C 20714, –55°C to + 125°C, 5 cycles.
- Combined climatic test: IEC 68-2-38.
- Damp heat: NF C 20703, 93 %, H.R., 40°C.
- Endurance test: 1,000 hours, 1.5 URC, 125°C.
STORAGE OF CHIP CAPACITORS
TINNED OR NON TINNED CHIP CAPACITORS
Storage must be in a dry environment at a temperature of 20°C with a relative humidity below 50 %, or preferably in a packaging enclosing a desiccant.
STORAGE IN INDUSTRIAL ENVIRONMENT:
- 2 years for tin dipped chip capacitors,
- 18 months for tin electroplated chip capacitors,
- 2 years for non tinned chip capacitors,
- 3 years for gold plated chip capacitors.
STORAGE IN CONTROLLED NEUTRAL NITROGEN ENVIRONMENT:
- 4 years for tin dipped or electroplated chip capacitors,
- 4 years for non tinned chip capacitors,
- 5 years for gold plated chip capacitors.
Storage duration should be considered from delivery date and not from batch manufacture date. The tests carried out at final acceptance stage (solderability, susceptibility to solder heat) enable to assess the compatibility to surface mounting of the chips.
SOLDERING ADVICES FOR REFLOW SOLDERING
Large chips above size 2225 are not recommended to be mounted on epoxy board due to thermal expansion coefficient mismatch between ceramic capacitor and epoxy. Where larger sizes are required, it is recommended to use components with ribbon or other adapted leads so as to absorb thermo-mechanical strains.
RECOMMENDED FOOTPRINT FOR SMD CAPACITORS
Ceramic is by nature a material which is sensitive both thermally and mechanically. Stresses caused by the physical and thermal properties of the capacitors, substrates and solders are attenuated by the leads.
Wave soldering is unsuitable for sizes larger than 2220 and for the higher ends of capacitance ranges due to possible thermal shock (capacitance values given upon request).
Infrared and vapor phase reflow, are preferred for high reliability applications as inherent thermo-mechanical strains are lower than those inherent to wave soldering.
SOLDERING ADVICES FOR IRON SOLDERING
Attachment with a soldering iron is discouraged due to ceramic brittleness and the process control limitations. In the event that a soldering iron must be used, the following precautions should be observed:
- Use a substrate with chip footprints big enough to allow putting side by side one end of the capacitor and the iron tip without any contact between this tip and the component,
- place the capacitor on this footprint,
- heat the substrate until the capacitor’s temperature reaches 150°C minimum (preheating step, maximum 1°C per second),
- place the hot iron tip (a flat tip is preferred) on the footprint without,
- touching the capacitor. Use a regulated iron with a 30 watts maximum,
- power. The recommended temperature of the iron is 270 ±10°C. The temperature gap between the capacitor and the iron tip must not exceed 120°C,
- leave the tip on the footprint for a few seconds in order to increase locally the footprint’s temperature,
- use a cored wire solder and put it down on the iron tip. In a preferred way use Sn/Pb/Ag 62/36/2 alloy,
- wait until the solder fillet is formed on the capacitor’s termination,
- take away iron and wire solder,
- wait a few minutes so that the substrate and capacitor come back down to the preheating temperature,
- solder the second termination using the same procedure as the first,
- let the soldered component cool down slowly to avoid any thermal shock.
TAPE AND REEL
The films used on the reels correspond to standard IEC 60286-3. Films are delivered on reels in compliance with document IEC 286-3 dated 1991.
Minimum quantity is 250 chips.
Maximum quantities per reel are as follows:
- Super 8 reel - Ø 180: 2,500 chips.
- Super 8 reel - Ø 330: 10,000 chips.
- Super 12 reel - Ø 180: 1,000 chips.
Reel marking complies with CECC 32100 standard:
- Rated capacitance.
- Capacitance tolerance.
- Rated voltage.
- Batch number.
15. Dimensional characteristics of chips tray packages
16. High Q Capacitors Tape and Reel Packaging Specifications
17. EIA standard capacitance values
Following EIA standard, the values and multiples that are indicated in the chart below can be ordered. E48, E96 series and intermediary values are available upon request.
18. EIA capacitance code
The capacitance is expressed in three digit codes and in units of pico Farads (pF).
The first and second digits are significant figures of the capacitance value and the third digit identifies the multiplier.
For capacitance value < 10pF, R designates a decimal point.
See examples below:
19. Part marking voltage codes
Use the following voltage code chart for part markings:
20. Part marking Tolerance codes
Use the following tolerance code chart for part markings:
21. Reliability levels
Exxelia proposes different reliability levels for the ceramic capacitors for both NPO and X7R ceramics.
As the world’s leading manufacturer of specific passive components, we stand apart through our ability to quickly evaluate the application specific engineering challenges and provide a cost-effective and efficient solutions.
For requirements that cannot be met by catalog products, we offer leading edge solutions in custom configuration: custom geometries, packaging, characteristics, all is possible thanks to our extensive experience and robust development process, while maintaining the highest level of reliability.
Where necessary, special testing is done to verify requirements, such as low dielectric absorption, ultra-high insulation resistance, low dissipation factor, stability under temperature cycling or under specified environmental conditions, etc.
Film capacitor series keeps its cool even at 150°C
The Exxelia Dearborn 880P series of metalised Polyphenylene Sulfide (PPS) Film Capacitors is designed to keep cool when things get hot. With an operating temperature range of -55 to +150°C, they experience no derating for DC operations and none in AC operations up to +125°C. This enables them to function at full capacity in extreme heat applications. The ability to operate at such high temperatures can eliminate the need for a cooling system within the design, thus reducing overall design time, weight and space. PPS is a high-temperature, low-loss dielectric film used in the 880P series of wrap-and-fill capacitors. This allows them to feature superior electrical characteristics over an extremely wide temperature range and maintain excellent capacitance stability in one rugged, lightweight package. It performs consistently well in commercial applications such as in power supplies and in more demanding applications, such as in avionics, on a congested control or instrumentation panel. The series features a capacitance range of 0.0047 to 10.0µF and voltage ratings from 50 to 400VDC with precision tolerances as low as ±¼% through ±10% yielding greater accuracy of capacitance. It is also a customisable unit with voltage maximums of 700 – 800VDC at 125°C maximum (higher voltages are available at reduced capacitance). Made in the USA, the units are highly durable and capable of withstanding a five-pound pull force on lead axis. They are non-polar and demonstrate low loss factor, good voltage breakdown strength and high insulation resistance (low leak current) – and are completely stable over normal temperatures, voltages and frequency ranges. These characteristics allow the 880P series capacitors to deliver high performance in a variety of applications such as DC timing circuits, low- to high-frequency AC applications, and pulse or energy discharge uses. Additionally, the package has axial leads with moisture-resistant, flame-retardant epoxy end seals and an outer tape covering for maximum performance.
TCM Series of High-Reliability Common-Mode Inductors
Exxelia designed this extensive and cost-effective range to be an easy commercial (COTS) solution for aerospace, defense, and other high-reliability applications. The TCM series is available in a through-hole package for horizontal or vertical mounting. TCM chokes are offered with inductances from 0.7 mH to 47 mH under rated currents from 0.3 to 4.0 A. Each unit is thoroughly tested with a dielectric withstanding strength of 1,500 VAC. Excellent thermal properties allow the series to operate from -55° C to +125° C. The high mechanical performance of the component materials (all meeting to UL94 V0 rating) makes TCM a perfect fit for aviation, defense and transportation industries. The TCM series of common-mode chokes is designed into circuit boards of a large number of power electronic devices used for a wide range of applications, including switch-mode power supplies and converters, inverters, battery management systems, and chargers. Exxelia’s TCM series fully complies with the requirements of RoHS and REACH.