General Technical Information 1 Inductive components for electronic equipment Especially in this age of fully-electronic and highly-integrated equipment, inductive components are indispensable. They are used to store energy intermittently in switch-mode power supplies and DC/DC converters, as parts of high-frequency circuits, as filter elements and last but not least as interference suppression components to ensure EMC. Of course, the demands placed on inductors depend on how and where they are to be used. In HF circuits, coils with high quality factors and resonance frequencies are needed. In EMC applications, high inductances are required in order to achieve good interference suppression characteristics, low Q factors being more desirable here due to the need to avoid resonances. EPCOS provides suitable inductive components for all applications. This data book contains a wide selection of standard components, from SMT types (starting with SIMID 0402) right up to the 4-line high-current inductors for power electronics applications. Attention is drawn to the excellent HF characteristics and the extremely high reliability of the components, achieved thanks to large-scale production automation and many years of experience in the manufacture of this kind of components. An overview of typical applications for inductors and chokes Application Inductance Current rating Resonance frequency low very high HF circuits, low resonant circuits EMC high ∗ Filter circuits high high Switch-mode ∗ ∗ power supplies, DC/DC converters ∗ depends on the specific application 1.1 high high medium Q factor DC resistance very high low low low high very low very low low HF circuits SMT styles (SIMID product range) and leaded RF chokes are especially suitable for RF and other high-frequency circuits. Typical applications are resonant circuits and frequency-selective filters of the type being increasingly used in telecommunications engineering and automotive electronics. In some cases, special demands on the inductive components arise, for example, when used in transmitter output circuits of mobile telephones (high Q factors and resonance frequencies) and in airbag control circuits (high pulse currents). 1.2 Filter circuits When inductive components are used for filters in power supplies for electronics, high inductances, the lowest possible DC resistance and a low Q factor are required. The impedance should have a wideband frequency characteristic. In addition to the current rating, the maximum permissible pulse current (switching transient currents) and adequately high core material saturation are of importance. Chokes belonging to all type series presented here can be used for this range of applications, from the SIMID types right up to chokes with powder cores and one or two lines. 9 04/00 General Technical Information 1.3 Switch-mode power supplies, DC/DC converters Inductive components are used for magnetic energy storage in all kinds of switch-mode power supplies and DC/DC converters. For example, the SIMID 1812 product range is used in low-power stepup converters in automobile electronics and in battery-powered equipment. They can be subjected for short periods to currents which are the quadruple of their current rating without any saturation effects occurring. 1.4 EMC applications For broadband interference suppression, current-compensated chokes with ring cores or D cores and powder core chokes are especially suitable. Apart from use as filters in mains and other power supply lines, such chokes are important for data lines as used in telecommunications engineering, e. g. in NTBAs (Network Termination Basic Access Units, ISDN), in line cards in telephone exchanges (ISDN and analog) and in the fast-expanding CAN bus application field (CAN = Controller Area Network) in automotive electronics. Almost all the component families are approved in accordance with the main international standards. All chokes for low-frequency mains networks are dimensioned and tested in compliance with the applicable EN and IEC standards. Inductive components with particularly good RF characteristics are achieved by the use of ungapped cores. The manufacturing methods developed by EPCOS lead to good reproducibility of the attenuation characteristics and enable the production of high-quality components at a favorable price. The company’s many years of experience guarantee that customers quickly and economically obtain just the right solutions to their EMC problems. Our own EMC laboratory in Regensburg or one of our European EMC partner laboratories is at your disposal at all times to help with professional advice and in carrying out measurements (also refer to the chapter on “Services”). 1.4.1 Propagation of interference Interference voltages and currents can be grouped into common-mode interference, differentialmode interference and unsymmetrical interference: 1a 1b 1c Us Uas Uus1 Uus2 U = V = voltage SSB1465-P asymmetrical asymmetrische propagation Ausbreitung symmetrical symmetrische propagation Ausbreitung unsymmetrical unsymmetrische propagation Ausbreitung Fig. 1 Propagation modes SSB1465-P ■ Common-mode interference (asymmetrical interference): – occurs between all lines in a cable and reference potential (fig. 1a), – occurs mainly at high frequencies (from approximately 1 MHz upwards). ■ Differential-mode interference (symmetrical interference): – occurs between two lines (L-L, L-N) (fig. 1b), – occurs mainly at low frequencies (up to several hundred kHz). 10 04/00 General Technical Information ■ Unsymmetrical interference: – This term is used to describe interference on a single line, relative to the reference potential (fig. 1c) 1.4.2 Characteristics of interferences In order to be able to choose the correct EMC measures, we need to know the characteristics of the interferences, how they are propagated and the mechanisms by which they are coupled into the circuit. In principle, the interferences can also be classified according to their range (fig. 2). At low frequencies, it can be assumed that the interference only spreads along conductive structures, at high frequencies only by means of electromagnetic radiation. In the MHz frequency range, the term coupling is generally used to describe the mechanism. Analogously, conducted interference on lines at frequencies of up to several hundred kHz are mainly symmetrical (differential mode), at higher frequencies, they are asymmetrical (common mode). This is because the coupling factor and the effects of parasitic capacitance and inductance between the conductors increase with frequency. X capacitors and single chokes are suitable as suppression measures for the differential mode components. Where asymmetrical, i.e. common-mode interference has to be eliminated, current-compensated chokes and Y capacitors are mainly used, the prerequisite for this being, however, a welldesigned, EMC-compliant grounding and wiring system. The categorization of types of interference and suppression measures and their relation to the frequency ranges is reflected in the frequency limits for interference voltage and interference field strength measurements. SSB1558-D Differential mode Common mode Field Interference characteristic Line Coupling Field Interference propagation X cap Pc ch. Y cap Cc ch. Ground Interference voltage 10 _2 10 _1 10 0 Remedies Shielding Field strength 10 1 10 2 Max. ratings MHz 10 3 f Fig. 2 Frequency range overview Pc ch. = Iron powder core chokes, but also all single chokes/ X cap = X capacitors Cc ch. = Current-compensated chokes / Y cap = Y capacitors 11 04/00 General Technical Information 2 Electromagnetic compatibility (EMC) 2.1 Introduction For as long as electronic transmission equipment such as radio, television, and telephone has been in existence, it has had a history of susceptibility to interference from other electronic devices. Legal regulations on interference suppression (electromagnetic and radio frequency interference, EMI and RFI) have been in existence since 1928. These regulations protect transmission paths and reception equipment by limiting the emitted interference. In view of the increasing number of electrical and electronic appliances in use, not only the principles of interference suppression must be observed, but also, in the sense of electromagnetic compatibility (EMC), it must be ensured that all equipment is able to operate simultaneously without problems. EMC is defined as the ability of electrical equipment to function satisfactorily in its electromagnetic environment without affecting other equipment in this environment to an impermissible extent. The European Communities’ EMC Directive (89/336/EEC) came into force on the 1. 1. 1996. It has been transformed into corresponding legislation in the individual EU (European Union) member states. With this, it has become mandatory to design electronic equipment to comply with the protection objectives of this Directive; i.e. to meet the requirements for electromagnetic emission and electromagnetic immunity as laid down in the corresponding EN standards (European Standards). The concept of EMC includes both electromagnetic emission (EME) and electromagnetic immunity/ susceptibility (EMS), see fig. 3. EMC = Electromagnetic compatibility EMC Emission Susceptibility EME EMS CE RE Interference source Fig. 3 Conducted Radiated Propagation CS EME = Electromagnetic emission EMS = Electromagnetic immunity/susceptibility CE = Conducted emission CS = Susceptibility to conducted emission RE = Radiated emission RS = Susceptibility to radiated emission RS Disturbed equipment EMC terms An interference source may generate conducted or radiated electromagnetic energy, i.e. conducted emission (CE) or radiated emission (RE). This also applies to the propagation paths and to the electromagnetic susceptibility of disturbed equipment. In order to work out economical solutions, it is necessary consider both phenomena, i.e. propagation and susceptibility, to an equal extent, and not just one aspect, e.g. conducted emission. 12 04/00 General Technical Information EMC components are used to reduce conducted electromagnetic interference to the limits in an EMC plan or to reduce this interference below the limit values specified in the EMC regulations. These components may be installed either in the source of potential interference or in the disturbed equipment (fig. 4). RE Power supply RE CE CE Source CE CE RE Disturbed equipment CE RE SA Signal line CE Control line CE Filter Fig. 4 Interference currents Interference voltages RE Electric field Magnetic field Electromagnetic field Susceptibility model and filtering EPCOS offers EMI suppression components with a well-balanced range of rated voltages and currents for power supply lines as well as for signal and control lines. 13 04/00 General Technical Information 2.2 Interference sources and disturbed equipment Interference source An interference source is an electrical device or electrical equipment which emits electromagnetic interference. We can differentiate between two main groups of interference sources corresponding to the type of frequency spectrum emitted (fig. 5). Interference source (emission) Discrete frequency spectrum (Sine-wave, low energy) Continuous frequency spectrum (Impulses, high energy) µP systems RF generators Medical equipment Data processing systems Microwave equipment Ultrasonic equipment RF welding apparatus Radio and TV receivers Switch-mode power supplies Frequency converters UPS systems Electronic ballast circuits Fig. 5 Switchgear (contactors, relays) Household appliances Gas discharge lamps Power supplies and battery chargers Ignition systems Welding apparatus Motors with brushes Oscillating drives Atmospheric discharges Sources of interference Interference sources with discrete frequency spectra (e.g. high frequency generators and microprocessor systems) emit interference energy which is concentrated on narrow frequency bands. Switchgear and electric motors in household appliances, however, distribute their interference energy over broad frequency bands and are considered to belong to the group of interference sources having a continuous frequency spectrum. 14 04/00 General Technical Information Disturbed equipment Electrical devices, equipment and/or systems subject to interference and which can be adversely affected by it are termed disturbed equipment. In the same way as interference sources, disturbed equipment can also be categorized corresponding to frequency characteristics. A distinction can be made between narrowband and broadband susceptibility (fig. 6). Narrowband systems include radio and TV sets, for example, whereas data processing systems are generally specified as broadband systems. Disturbed equipment (affected by EMI) Narrowband susceptibility Broadband susceptibility Radio and TV receivers Radio reception equipment Modems Data transmission systems Telemetric radio transmission devices Frequency-coded signalling equipment Fig. 6 2.3 Digital and analog systems Data processing systems Process control computers Control systems Video transmission systems Interface lines Disturbed equipment Propagation of electromagnetic interference and EMC measurement techniques As previously mentioned, an interference source causes both conducted and radiated electromagnetic interference. Propagation along lines can be detected by measuring the interference current and the interference voltage (fig. 7). The effect of magnetic and electric interference fields on their immediate vicinity is assessed by measuring the radiated magnetic and electric field components. This method of propagation is also frequently termed electric or magnetic coupling (near field). In higher frequency ranges, characterized by the fact that device dimensions are in the order of magnitude of the wavelength under consideration, the interference energy is mainly radiated directly (far field). Conducted and radiated propagation must also be taken into consideration when measuring the susceptibility of disturbed equipment. Interference sources e.g. sine-wave generators as well as pulse generators with a wide variety of pulse shapes are used for such tests. 15 04/00 General Technical Information Netzzuführung Stromwandler Power supply Current Voltage probe Tastkopf probe NetzLine impedance stabilization Nachbildung network Broadband dipole antenna Breitbandantenne I int Ι S Messempfänger Selective voltmeter VUintS PSint Messempfänger Selective voltmeter Spektrumanalysator Spectrum analyzer Speicheroszillograph Storage oscilloscope Transientenrekorder Transient recorder Hint = Magnetic interference fields Eint = Electrical interference fields Pint = Electromagnetic interference fields (radiated emission) Iint = Interference current Vint = Interference voltage Source Quelle EEint S H HSint Loop antenna Rahmenantenne Stabantenne Rod antenna NearNahfeldkopplung field coupling Messempfänger Selective voltmeter Messempfänger Selective voltmeter SSB0016-2 SSB0016-2 Fig. 7 2.4 Propagation of electromagnetic interference and EMC measurement techniques EMC regulations und legislation A wide range of legislation and of harmonized standards have come into force and been published in the field of EMC in the past few years. In the European Union, the EMC Directive 89/336/EEC of the Council of the European Communites has come into effect on the 1st of January 1996. As of this date, all electronic equipment must comply with the protection objectives of the EMC Directive. The conformity with the respective standards must be guaranteed by the manufacturer or importer in the form of a declaration of conformity. A CE mark of conformity must be applied to all equipment. As a matter of principle, all electrical or electronic equipment, installations and systems must meet the protection requirements of the EMC Directive and/or national EMC legislation. A declaration of conformity by the manufacturer or importer and a CE mark are required for most equipment. Exceptions to this rule and special rulings are described in detail in the EMC laws. New, harmonized European standards have been drawn up in relation to the EEC’s EMC Directive and the national EMC laws. These specify measurement procedures and limit values or test severities, both for interference emission and for the interference susceptibility (or rather, immunity to interference) of electronic devices, equipment and systems. The subdivision of the European standards into various categories (cf. following table) makes it easier to find the rules that apply to the respective equipment. The generic standards always apply to all equipment for which there is no specific product family standard or dedicated product standard. The basic standards contain information on interference phenomena and general measuring methods. 16 04/00 General Technical Information The following standards and regulations form the framework of the conformity tests: EMC standards Germany Europe International Generic standards define the EMC environment in which a device is to operate according to its intended use Emission residential industrial DIN EN 50081-1 DIN EN 50081-2 EN 50081-1 EN 50081-2 — Susceptibility residential industrial DIN EN 50082-1 DIN EN 50082-2 EN 50082-1 EN 50082-2 — Basic standards describe physical phenomena and measurement procedures Basics DIN VDE 0843 Measuring equipment DIN VDE 0876 Measuring methods DIN VDE 0877 emission susceptibility EN 61000 IEC 61000 CISPR 16-1 EN 61000-4-1 CISPR 16-2 IEC 61000-4-1 Harmonics DIN VDE 0838 EN 60555-2 IEC 61000-3-2 Interference factors e.g. ESD EM fields Burst Surge Injection DIN VDE 0843-2 DIN VDE 0843-3 DIN VDE 0843-4 DIN VDE 0843-5 DIN VDE 0843-6 EN 61000-4-2 EN 61000-4-3 EN 61000-4-4 EN 61000-4-5 EN 61000-4-6 IEC 61000-4-2 IEC 61000-4-3 IEC 61000-4-4 IEC 61000-4-5 IEC 61000-4-6 EN 55011 1) CISPR 11 1) Product standards define limit values for emission and susceptibility ISM equipment emission susceptibility DIN VDE 0875 T11 1) Household appliances emission susceptibility DIN VDE 0875 T14-1 EN 55014-1 DIN VDE 0875 T14-2 EN 55014-2 CISPR 14-1 CISPR 14-2 Lighting emission susceptibility DIN VDE 0875 T15-1 EN 55015-1 DIN VDE 0875 T15-2 EN 55015-2 CISPR 15 IEC 3439 Radio and TV equipment emission susceptibility DIN VDE 0872 T13 DIN VDE 0872 T20 EN 55013 EN 55020 CISPR 13 CISPR 20 High-voltage systems emission DIN VDE 0873 EN 55018 CISPR 18 ITE equipment emission susceptibility DIN VDE 0878 DIN VDE 0878 EN 55022 EN 55022 CISPR 22 CISPR 22 Vehicles DIN VDE 0879 DIN VDE 0839 EN 72245 CISPR 25 ISO 11451/ S2 emission susceptibility 1) Is governed by the safety and quality standards of the product families. 17 04/00 General Technical Information The following table shows the most important standards in the field of immunity to interference. Standard Test characteristics Phenomena EN 61000-4-4 IEC 61000-4-4 5/50 ns (single impulse) 15 kHz burst Burst Cause: switching processes EN 61000-4-5 IEC 61000-4-5 1,2 / 50 ms (open-circuit voltage) Surge (high-energy transients) 8 / 20 ms (short-circuit current) Cause: lightning strikes mains lines, switching processes EN 61000-4-6 (ENV 50141) IEC 801-6 1 V, 3 V, 10 V 150 kHz … 80 MHz High-frequency coupling Narrow-band interference 3 V/m, 10 V/m 80 … 1000 MHz High-frequency interference fields Conducted interference Radiated interference EN 61000-4-3 (ENV 50140) IEC 801-3 Electrostatic discharge (ESD) EN 61000-4-2 IEC 61000-4-2 Up to 8 kV 5 / 50 ns Electrostatic discharge Voltage dips, short interruptions and variations EN 61000-4-11 IEC 61000-4-11 0,7 VR 0,4 VR 1 … 50 ms optional VR = 0 10 ms Electrostatic discharge The IEC 1000 or EN 61000 series of standards are planned as central EMC standards into which all EMC regulations (e.g. IEC 801, IEC 555) are to be integrated in the next few years. 2.5 Propagation of conducted interference In order to be able to choose suitable interference suppression components, the way in which conducted interference is propagated needs to be known (fig. 8). Interference source Disturbed equipment Common-mode interference current Differential-mode interference current Cp: Parasitic capacitance R: Resistance Fig. 8 Common-mode and differential-mode interference 18 04/00 General Technical Information An interference source which is at a floating potential primarily emits differential-mode, i.e. symmetrical interference which is propagated along the connected lines. On power lines, the interference current will flow towards the disturbed equipment on one wire and away from it on the other wire, just as the mains current does. Symmetrical or differential-mode interference occurs mainly at low frequencies (up to several hundred kHz). However, parasitic capacitances in interference sources and disturbed equipment or intended ground connections, also lead to an interference current in the ground circuit. This interference current flows towards the disturbed equipment through both the connecting lines and returns to the interference source through the ground lines.The currents on the connecting lines are in common mode and the interference is thus designated as common-mode or asymmetrical interference. Since the parasitic capacitances will tend towards representing a short-circuit with increasing frequencies and the coupling to the connecting cables and the equipment itself will increase correspondingly, common-mode interference becomes dominant at multiple-MHz frequencies. In European usage, the concept of an “unsymmetrical interference” is used, in addition to the two components described above, to describe interference. This term is used to describe the interference voltage between a line and reference ground potential. 2.6 Filter circuits and line impedance Interference suppression filters are virtually always designed as reflecting lowpass filters, i.e. they reach their highest insertion loss when they are - on the one hand - mismatched to the impedance of the interference source or disturbed equipment and - on the other hand - mismatched to the impedance of the line. Possible filter circuits for various line, interference source and disturbed equipment impedance conditions are shown in fig. 9. Line impedance Impedance of source of interference / disturbed equipment low high high high high unknown high unknown low low low unknown low unknown Fig. 9 Filter circuits and impedance relationships 19 04/00 General Technical Information It is, therefore, necessary to find out the internal impedances so that optimum filter circuit designs as well as economical solutions can be implemented. The internal impedances of the power networks under consideration are usually known from calculations and extensive measurements, whereas the impedances of interference sources or disturbed equipment are, in most cases, not or only inadequately known. For this reason, it is impossible to design the most suitable filter solution without measuring the equipment characteristics. In this context, we offer all our customers the competent assistance of our skilled staff, both on-site and in our EMC laboratory in Regensburg (also see chapter on “Services offered”, page 32). 3 Selection criteria for EMC components To comply with currently valid regulations, a frequency range of 150 kHz to 1000 MHz has to be taken into consideration, in most cases, in order to ensure electromagnetic compatibility; in addition, however, factors such as low-frequency line interference should be considered. EMC components must thus have favorable RF characteristics and are ususally required to be effective over a broad frequency range. For individual components (inductors) the RF characteristics are specified by stating the impedance as a function of frequency. 4 Arrangement of EMC components When designing filter circuits using individual components, observe the following basic rules: ■ The components should be arranged along the lines (see example in fig. 10) to avoid capacitive and inductive coupling between components and between filter inputs and outputs. ■ As insertion loss of a filter circuit in the MHz range is mainly determined by the capacitors con- nected to ground, the connecting leads of these capacitors should be as inductance-free as possible, i.e. short. ■ Filter circuits which are to be installed in devices with limited space must be shielded. Chokeint Fig. 10 Correct arrangement of filter components, e.g. on a PC board 20 04/00 General Technical Information When using off-the-shelf filters, observe the following rules: ■ Ensure a proper electrically conductive connection between the filter case and/or filter ground and the metallic case of the interference source or disturbed equipment, and ■ provide sufficient RF decoupling between the lines at the filter input (line causing the interfer- ence) and the filter output (filtered line), if necessary by using shielding partitions. 5 Approvals All products by EPCOS AG are basically designed to conform to the German VDE regulations and/or EN standards. The respective regulations or standards are given for each component type. Many of our components have also been approval-tested in accordance with national and international regulations. The approval marks and quality assurance marks are listed in the data sheets. Examples of approval marks: UL USA VDE Germany Example of a quality assurance mark: CECC quality assurance mark In future, chokes will be tested in accordance with the new European standard EN 138 100. A uniform European mark of conformity has not yet been defined. For the time being the national marks of conformity are used (e.g. VDE) and the corresponding European standards is stated beside the mark. 6 Safety regulations When selecting EMC components – in particular in case of power line applications – the safety regulations applicable to the relevant equipment must be observed. 21 04/00 General Technical Information 7 Electrical characteristics 7.1 Rated voltage VR The rated voltage VR is the maximum ac or dc voltage which can be continuously applied to the component at temperatures between the lower category temperature Tmin and the upper category temperature Tmax. 7.2 Test voltage VT The test voltage VT is the ac or dc voltage which may be applied to the component for the specified test duration in the course of final inspection (100% end of line testing). This test may be repeated once as an incoming goods inspection test. 7.3 Rated current IR The rated current lR is ac or dc current at which the component may be continuously operated under the nominal operating conditions. For components with 1, 2 or 3 lines, the rated current is specified for simultaneous flow of a current of this value through all lines. During ac operation, higher thermal loads may be caused due to waveforms which deviate from a pure sine wave. Where necessary, such cases must be taken into consideration. 7.4 Overcurrent The rated current may be exceeded briefly. Details on permissible currents and load duration can be obtained upon request. 7.5 Pulse handling capability Saturation effects (e.g in the ferrite cores used) may occur when high-energy pulses are applied to the components and these may lead to impaired interference suppression. The maximum permissible voltage-time integral area is used to characterize the pulse handling capability of chokes. For standard components a range from 1 to 10 mVs can be assumed. More specific data can be obtained upon request. 7.6 Current derating Iop/IR At ambient temperatures above the operating temperature stated in the data sheet, the operating current must be reduced according to the derating curve. 7.7 Rated inductance LR The rated inductance LR is the inductance which has been used to designate the choke, as measured at the frequency fL. 22 04/00 General Technical Information 7.8 Stray inductance LS The stray inductance LS (also termed leakage inductance) is the inductance measured through both coils when a current-compensated choke is short-circuited at one end. This affects symmetrical interference. Fig. 11 7.9 Stray inductance Inductance decrease ∆L/L0 The inductance decrease ∆L/L0 is the drop in inductance at a given current relative to the initial inductance L0 measured at zero current. The data sheets specify this as a percentage. This decrease is caused by the magnetization of the core material, which is a function of the field strength, as induced by the operating current. Generally the decrease is less than 10 % . 7.10 DC resistance Rtyp, Rmin, Rmax The dc resistance is the resistance of a line as measured using direct current at a temperature of 20 °C, whereby the measuring current must be kept well below the rated current. Rtyp Rmin Rmax typical value minimum value maximum value 7.11 Winding capacitance, parasitic capacitance CP Parasitic capacitances (CP), which impair the RF characteristics of the components, are related to the component geometry. These capacitances may affect the two lines mutually (symmetrically) as well as the line-to-ground circuit (asymmetrically). The design of all EMC components supplied by EPCOS minimizes the parasitic effects. Due to this, these components have excellent interference suppression characteristics right up to high frequencies. 7.12 Quality factor Q The quality factor Q is the quotient of the imaginary component of the impedance divided by the real component. 7.13 Measuring frequencies fQ, fL fQ is the frequency for which the quality factor Q of a choke is specified. fL is the frequency at which the inductance of a choke is determined. 23 04/00 General Technical Information 7.14 Insertion loss The insertion loss is a criterium for the effectivity of interference suppression components, as measured by using a standardized measurement circuit (fig. 12). Reference measurement U = V = Voltage Insertion loss measurement Fig. 12 Definition of insertion loss The input terminals of the equipment under test are connected to an RF generator with impedance Z (usually 50 Ω) . At the output end of the component, the voltage is measured using a selective voltmeter having the same impedance Z. The insertion loss is then calculated from the quotient of the no-load generator voltage V0 and half the output voltage V2. 24 04/00 General Technical Information 8 Mechanical properties 8.1 Potting (economy potting, complete potting) We distinguish between economy potting and complete potting. Economy potting is used to fix the the core and windings in the case and the windings on the core. This is an economical technique which enables a single resin casting procedure to be used. Because of this, most chokes supplied by EPCOS are produced using this method. Complete potting is only required when the thermal conductitvity of economy potting is not adequate or if the customer has special demands. Complete potting requires several process steps to ensure complete embedding of the core and the windings. Economy potting 8.2 Complete potting Types of winding EPCOS uses different types of winding to suit the respective technical requirements: – single-layer winding – multilayer winding – random winding The different types of winding lead to different inductance characteristics, especially at high frequencies. Single-layer winding: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 The winding pitch is equal to or greater than the wire diameter. The coil is wound in one direction only. The only capacitances (parasitic capacitances) are those between one turn to the next. In comparison to all other types of winding, this type of winding leads to the lowest possible capacitances and thus the highest resonance frequencies. 25 04/00 General Technical Information Multilayer winding: 19 18 17 16 15 14 13 12 11 1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 10 19 18 17 16 15 14 13 12 11 The winding pitch is equal to the wire diameter. The coil is wound with several layers. This leads to parasitic capacitances between the layers in addition to the turn-to-turn capacitances. In comparison to all other types of winding, this type leads to the highest capacitances and thus the lowest resonance frequencies. Random winding: 4 7 9 12 16 18 1 2 3 5 6 8 10 11 13 14 15 17 19 1 2 3 5 6 8 10 11 13 14 15 17 19 4 7 9 12 16 18 14 The winding pitch is smaller than the wire diameter. The coil is wound in one direction only. This method of winding a coil does not permit the final position of a turn to be predetermined exactly. The cross section of this type of winding clearly shows a disorderly, “random” arrangement of the turns. This leads to the parasitic capacitances being only minimally greater than those achieved by singlelayer winding, and the resonance frequencies are equal to those achieved by single-layer winding. 26 04/00 General Technical Information 8.3 RF characteristics of various types of winding Figure 13 shows the relation between the impedance and the frequency for two chokes of equal inductance. One of the chokes has a two-layer winding and the other is randomly wound. The choke with random windings has a considerably higher first resonance frequency. The spurious resonances are very much higher than 10 MHz. The impedance at frequencies above the first resonance frequency is approximately five times higher. This leads to better interference suppression at high frequencies. 2-layer wdg. Random wdg. Fig. 13 Impedance |Z| versus frequency f comparison between two-layer winding and random winding The RF characteristics of all chokes supplied by EPCOS are within the specifications and reproducible, as the winding processes which we have developed for single-layer, multilayer and random winding ensure that the characteristics of the inductors produced display very little variation. The reproducibility of electrical characteristics of chokes is mainly determined by the production technique used. At EPCOS, coils are wound mainly by automatic machines (either fully or semi-automated). This permits even complicated winding patterns to be produced in large production runs with very little variation in product characteristics. In fig. 14, the impedance curves of several chokes, some wound manually and some by machine, are shown for comparison. With the random winding used in this comparison, the advantages of machine winding are clearly noticeable. 27 04/00 General Technical Information Manually wound Machine wound Fig. 14 Impedance |Z | versus frequency f Reproducibility and scatter achieved by manual and by machine winding techniques. 9 Climatic characteristics 9.1 Upper and lower category temperature Tmax and Tmin The upper category temperature Tmax und the lower category temperature Tmin are defined as the highest and the lowest permissible ambient temperatures, respectively, at which the component can be operated continuously. 9.2 Rated temperature TR The rated temperature TR is defined as the highest ambient temperature at which the component may be operated under nominal conditions. 9.3 Reference temperature for measurements Unless otherwise specified in the data sheets, the reference temperature for all electrical measurements is 20 °C in accordance with IEC 60068-1. 28 04/00 General Technical Information 9.4 IEC climatic category lEC 60068 -1, Appendix A, defines a method of specifying the climatic category by three groups of numbers delimited by slash characters. Example: 55/085/56 – 55 °C + 85 °C 56 days 1st group of numbers: Absolute value of the lower category temperature Tmin as test temperature for test Aa (cold) in accordance with IEC 60068-2-1 2nd group of numbers: Upper category temperature Tmax as test temperature for test Ba (dry heat) in accordance with IEC 60068 -2-2 test duration: 16 h 3rd group of numbers: Number of days denoting the test duration for test Ca (damp heat, steady-state) in accordance with IEC 60068-2-3 at (93 + 2/– 3) % rel. humidity and an ambient temperature of 40 °C 10 Sizes The sizes of surface-mount components are encoded using a four-digit coding system. The code differs depending on the standard which it is based on. The American EIA standards require the length and width to be stated in hundredths of an inch, in European standards and in the IEC draft standards, these dimensions are encoded in tenths of a millimeter. The following table sumarizes the sizes: Length × width (mm) 1,0 × 0,5 1,6 × 0,8 2,0 × 1,2 2,5 × 2,0 3,2 × 2,5 4,5 × 3,2 5,6 × 5,0 EIA IEC/EN 0402 0603 0805 1008 1210 1812 2220 1005 1608 2012 2520 3225 4532 5650 29 04/00 General Technical Information 11 Dangerous substances in components Dangerous substances (as defined by the German regulation “Gefahrstoffverordnung”) are only used in our production and to an extent where the state of the art leaves us no alternative. Wherever possible, we replace them by materials with safe characteristics. Where this is not possible, special staff entrusted with environmental protection and supervision of noxious materials monitor strict adherence to relevant laws and regulations in each of our factories. As part of these efforts to manufacture our products without using dangerous substances as far as possible, we can guarantee for all components presented in this data book that they do not contain the following materials and compounds: – – – – – – – – acryl nitrile aliphatic chlorinated organic componds arsenic compounds asbestos lead carbonate and lead sulphide halogenated dioxines and furanes cadmium chlorinated fluorocarbons (CFC), nor are they used in component manufacture. Others, – – – – – – – – – formaldehyde pentachlorophenol (PCB) polychlorinated biphenyles (PCB) polychlorinated terphenyles (PCT) mercury compounds creosote ugilec and DBBT (PCB substitutes) organic tin compounds vinyl chloride may be used in manufacture but the components do not contain these. The packaging of our components is generally suitable for ESD areas and free of pollutants. Full details are available from our sales offices. 12 Disposal In the light of the facts stated above on the topic of dangerous substances, all components presented in this book can be disposed of without problems. Most of our components will be accepted by the respective electronic scrap recycling companies for material recycling and/or thermal decompositon. Of course the corresponding local regulations must be observed. 30 04/00