1、 EIA STANDARD Application Guide for Multilayer Ceramic Capacitors - Electrical EIA-521-A (Revision of EIA-521) December 2013 EIA-521-AANSI/EIA-521-A Approved: July 26, 1993 Revised: December 4, 2013 NOTICE EIA Engineering Standards and Publications are designed to serve the public interest through e
2、liminating misunderstandings between manufacturers and purchasers, facilitating interchangeability and improvement of products, and assisting the purchaser in selecting and obtaining with minimum delay the proper product for his particular need. Existence of such Standards and Publications shall not
3、 in any respect preclude any member or nonmember of ECIA from manufacturing or selling products not conforming to such Standards and Publications, nor shall the existence of such Standards and Publications preclude their voluntary use by those other than ECIA members, whether the standard is to be u
4、sed either domestically or internationally. Standards and Publications are adopted by ECIA in accordance with the American National Standards Institute (ANSI) patent policy. By such action, ECIA does not assume any liability to any patent owner, nor does it assume any obligation whatever to parties
5、adopting the Standard or Publication. This EIA Standard is considered to have International Standardization implication, but the International Electrotechnical Commission activity has not progressed to the point where a valid comparison between the EIA Standard and the IEC document can be made. This
6、 Standard does not purport to address all safety problems associated with its use or all applicable regulatory requirements. It is the responsibility of the user of this Standard to establish appropriate safety and health practices and to determine the applicability of regulatory limitations before
7、its use. (From Standards Proposal No. 5250, formulated under the cognizance of the P-2.1 Committee on EIA National Ceramic and Dielectric Capacitors Standards). Published by Electronic Components Industry Association 2013 Engineering Department 2214 Rock Hill Road, Suite 170 Herndon, VA 20170 PLEASE
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9、2-5704 or call USA and Canada (1-877-413-5184), International (303-397-7956) i CONTENTS Page Foreword Clause 1 Introduction 1 2 Definition of ceramic capacitors 2 2.1 Mechanical 2 2.2 Electrical 3 3 Factors influencing performance 5 3.1 Temperature coefficient of capacitance (TCC) 5 3.2 DC voltage c
10、oefficient of capacitance (VCC) 7 3.3 AC voltage coefficient of capacitance 7 3.4 Temperature voltage coefficient of capacitance (TCVC) 8 3.5 Ageing 9 3.6 Frequency effects on performance (capacitance, dissipation factor, impedance, equivalent series resistance, and equivalent series inductance) 10
11、4 Electrical properties 13 4.1 Piezoelectric properties 13 4.2 Dielectric absorption 13 4.3 AC Corona 14 5 Reliability 14 5.1 Failure modes associated with packaging 14 5.2 Failure modes in the capacitor element 15 6 Typical applications 17 Annex A Additional information 18 EIA-521-A Page 1 1 Introd
12、uction Ceramic capacitors are those wherein the dielectric material is a high-temperature, sintered, inorganic ceramic compound. As a general rule, these materials are based on mixtures of complex titanates or niobate compounds, i.e., barium titanate, titanium oxide, calcium titanate, strontium tita
13、nate, etc. Stannate and zirconate compounds are also used. Because of the great variety of electrical characteristics found in ceramic capacitors, the Electronic Component Industry Association (ECIA) has categorized ceramic capacitors into four separate classes. 1.1 Class I capacitors Class I capaci
14、tors are those of the stable and temperature-compensating type. They are available in a wide range of temperature coefficients with relatively linear characteristics. They are suited for applications where low losses and high stability are required. The capacitance ranges available in Class I are mu
15、ch lower than in the other classes. 1.2 Class II capacitors Class II capacitors are typically more complex in formulation. They may be ferroelectric compounds, often based on barium titanate, and possess a high dielectric constant (K). They are classified as having a semi-stable temperature characte
16、ristic and are used over a wide temperature range. 1.3 Class III capacitors Class III capacitors are typically based on complex formulations. Like Class II, they may be ferroelectric compounds, often based on barium titanate, but Class III capacitors have a much greater dielectric constant (K). They
17、 are the most volumetrically-efficient of the standard ceramic dielectric types. They are used over a moderate temperature range in applications where high capacitance is required, but where significant dielectric losses and capacitance changes can be tolerated. 1.4 Class IV capacitors Class IV capa
18、citors are restricted to reduced titanate or barrier layer dielectrics. These capacitors have the highest apparent dielectric constant (K). Creating a thin re-oxidized dielectric layer, a PN semiconductor junction, and/or a thin grain boundary insulating layer develops the high dielectric constant.
19、They exhibit the same temperature characteristics as the oxidized ceramic formulation. 1.5 Overview All classes of ceramic capacitors are available in a variety of physical forms, ranging from disc or rectangular single layer and multilayer types, e.g. multilayer ceramic chip (MLCC), feed-through st
20、yles, and combinations of these. In all their variations, ceramic dielectric capacitors are used more than any other single dielectric family. High usage is the result of low cost, good volumetric efficiency, excellent high frequency capabilities, and inherent reliability. EIA-521-A Page 2 2 Definit
21、ion of ceramic capacitors 2.1 Mechanical 2.1.1 Single layer This type of device utilizes a single dielectric layer. The form of this dielectric may be a flat disc, rectangular block, or tubular shape. The single layer dielectric typically has a minimum thickness of 0.2 mm (0.008 in). These component
22、s are most often constructed with leads and coated with an insulating material. Multiple devices are often mechanically paralleled to increase the total capacitance. 2.1.2 Multilayer (MLCC) Multilayer ceramic capacitors utilize a number of thin dielectric and electrode layers, measured on the micron
23、 level. Because the layers are stacked in the unsintered “green” state, it is possible to achieve much thinner dielectrics than in the single layer type. This results in much greater volumetric efficiency. The multiple layers are sintered into a monolithic structure that has excellent mechanical str
24、ength. MLCCs may be used in chip form in surface mount applications, or they may be assembled into encapsulated or unencapsulated axial or radial leaded units used in circuit boards or other circuit applications. 2.1.2.1 Single and multilayer construction Typical constructions are detailed in Figure
25、 1. Figure 1Single and multilayer construction EIA-521-A Page 3 2.2 Electrical 2.2.1 Capacitance Capacitors are electrical storage devices used in electrical and electronic equipment principally as energy storing, decoupling, coupling, bypassing or filtering, DC current blocking, voltage transient s
26、uppressing, and voltage multiplying applications. The capacitance (C) of a capacitor is determined by the relative permittivity of the dielectric material (r), the absolute permittivity (0= 8.85 x 10-12F/m), the overlap of the active plate area (A), and the thickness of the dielectric (d) between th
27、e plates, as shown in Equation 1: 0 rACd= (1) Note: r0is often called dielectric constant, or K value In simplified form, capacitance is expressed as follows: Single layer ceramics (equation 2): 0.00885rACd=(2) where C = capacitance (pF) 0.00885 = constant (0= 8.85 x 10-12F/m) r= relative permittivi
28、ty A = overlap area of one electrode in square mm d = dielectric thickness in mm Multilayer ceramics (equation 3): ( )0.008851rACNd= (3) where N = number of electrode layers NOTETypical dielectric constants are listed in Table 1. EIA-521-A Page 4 2.2.2 Dissipation Factor and Quality Factor The dissi
29、pation factor (DF) of a capacitor is the energy losses in the capacitor, and is the tangent of the angle by which the current lags the 90 vector of the voltage. The DF can also be expressed as an equivalent series resistor, R (equation 4): DF= (2fC) R (4) The dissipation factor is highly dependent u
30、pon frequency, voltage, temperature, and dielectric composition, and is listed as a dimensionless unit or as a percent, e.g., a dissipation factor of 0.010 is expressed as 1.0%. Quality Factor (Q) is typically used as a measure of energy losses in higher frequency applications with Class 1 capacitor
31、s. A typical value for Q is 1000. Q is the reciprocal of DF (equation 5): Q=1/DF (5) Listed in Table 1 are typical dissipation factors for ceramic capacitors. 2.2.3 Insulation resistance The insulation resistance (IR) is a measure of the ability of the charged capacitor to resist loss of charge thro
32、ugh the mechanism of DC leakage current. Under the influence of a DC field, ions will move from one atomic interstitial site to another and will generate a DC current. With increasing temperature, the mobility of these charge carriers increases, causing a decrease in the insulation resistance. Other
33、 factors that influence the insulation resistance of a ceramic capacitor are dielectric composition, dielectric thickness, defect sites in the dielectric layers, and the number of dielectric layers (total plate area or capacitance value). For the latter reason, the IR limits are expressed as the pro
34、duct of IR (megohms) times capacitance (microfarads), yielding a minimum requirement expressed in megohms-microfarads (or ohm-farads, which is equivalent). Table 1 gives typical values of IR for the various ceramic characteristics. Table 1Typical performance Dielectric Class (typical TC) Typical K T
35、ypical dissipation factor (DF) % over Temperature Typical insulation resistance (IR) over Temperature -55C +10C +25C +85C +125C +25C +85C +125C I (C0G) 65 100 G 50 G 1 G II (X7R) 2,000 4-6 2-2.5 1.5-2.5 1-1.5 0.7-1.5 2000 M 1000 M 200 M II (X5R) 3,000 4-6 2-2.5 1.5-2.5 1-1.5 2000 M 1000 M 200 M III
36、(Z5U) 8,000 5 3 1 1000 M 500 M III (Y5V) 10,000 3 1.5 0.5 1000 M 500 M IV 8 6 5 2.5 1 5 M 2.5 M EIA-521-A Page 5 3 Factors influencing performance 3.1 Temperature coefficient The capacitance of all ceramic capacitors will vary with temperature. The degree of variation depends upon the dielectric cla
37、ss. Class I dielectrics, which include P150 through N5600, have relatively predictable temperature coefficients as noted in Figure 2. Figure 2Temperature characteristic, C lass I NOTEThe TCC designation for Class I capacitors is based on a t wo point measurement at 85 C and 25 C. The relative nonlin
38、earity is typically more pronounced between 25 C and -55C, although curvature may also occur from 25 C to +125 C. For capacitance values less than 20 pF, the encapsulant and/or fringe effect may alter the apparent temperature coefficient of capacitance (TCC). -60 -40 -20 0 20 40 60 80 100 120 -8 -6
39、-4 -2 0 2 4 6 8 N050 C0G C0G P100 N050 N220 N470 N750 P100 N750 N470 N220 -55 o C 25 o C 125 o C Temperature o C % capacitance changeEIA-521-A Page 6 Class II dielectrics, characterized as semi-stable formulations, have typical temperature characteristics as depicted in Figure 3. Figure 3Typical tem
40、perature characteristic curves, class II Class III dielectrics use less complex modifiers to develop very high dielectric constants, which enables them to achieve higher capacitance than can Class II capacitors. These dielectrics exhibit temperature characteristics as depicted in Figure 4. -60 -35 -
41、10 15 40 65 90 115-100-75-50-250Y5UY5VZ5UY5 Temperature rangeZ5 Temperature rangeTemperature (oC)Change incapacitance(%)Figure 4Typical temperature characteristic curves, class III Class IV dielectrics, which are reduced titanates with a very high dielectric constant, will meet the same temperature
42、coefficient limits as the oxidized formulations from class III (Figure 4). -60 -40 -20 0 20 40 60 80 100 120 140 -40 -30 -20 -10 0 10 20 30 40 X5R X7R X7 temperature range X5 temperature range Temperature o C % capacitance changeEIA-521-A Page 7 3.2 DC voltage coefficient All class II, III, and IV c
43、eramic capacitors exhibit a change in dielectric constant (K) with an applied DC bias. This variation occurs due to the restriction that the voltage stress causes on the freedom on some of the polarization mechanisms of the dielectric. Higher permittivity dielectric material will exhibit a larger ch
44、ange in permittivity for a given DC bias. Class I dielectrics do not exhibit measurable capacitance change with DC bias. Therefore, it is important that this characteristic be taken into account for design purposes. Figure 5 graphically displays a typical voltage coefficient variation of the more pr
45、ominent formulations. NOTEThe curve shown is for capacitors rated at 50V. The high capacitance, low voltage ceramics recently introduced have much thinner dielectric, and may show a pronounced loss of capacitance with applied DC bias. The voltage coefficient may display considerable variation from m
46、anufacturer to manufacturer. The circuit engineer should take this into account during the design phase. Figure 5Typical DC voltage coefficient of a 50 VDC -rated MLCC 3.3 AC voltage coefficient Class II, III, and IV ceramic capacitors exhibit an AC voltage coefficient as represented in the curves o
47、f Figure 6. Accordingly, it is important that the user measure these devices at the recommended rms voltages specified in EIA-198. Failure to do so can create correlation problems between manufacturer and customer. The AC voltage coefficient, like the DC voltage coefficient, should be taken into con
48、sideration when designing for AC voltage applications. Typical capacitance and dissipation factor (DF) changes with AC voltage can be found in the curves of Figure 6. 0 10 20 30 40 50 60 -100 -80 -60 -40 -20 0 20 X7R Y5U Z5U Y5V Applied Voltage (VDC) Change incapacitance (%)EIA-521-A Page 8 0 2 4 6
49、8 10 1201020X7RAC measuring voltage1 kHzChange incapacitance(%)0 2 4 6 8 10 120255070AC measuring voltage 1 kHzChange incapacitance(%)Z5UY5U0 2 4 6 8 10 1201234X7RAC measuring voltage 1 kHzDissipationfactor,DF(%)0 2 4 6 8 10 1202468101214AC measuring voltage 1 kHzDissipationfactor,DF(%)Z5UY5UFigure 6Typical AC voltage coefficient of a 50 VDC -rated MLCC 3.4 Temperature Voltage coefficient (combined effect) The capacitance change over the temperature range wit
