DIN IEC/TR 61340-1:2014-06

Static electricity has been known for around 2 500 years but until recently had little impact on humankind. More recently in the last century the nature of static electricity became better understood and the principles of charge separation and accumulation could be described. Despite this improved understanding, it remains difficult to predict with certainty the polarity and magnitude of charges built up in any situation due to the many factors involved, and to, many electrostatics remains a "black art" rather than a science. The development of modern materials, especially polymers, and their nearly ubiquitous application in fields such as floor materials, furnishings, clothing and engineering materials has made static electricity an everyday phenomenon. In some industries, such as electronics manufacture and processes using flammable materials, unintended and invisible electrostatic discharges can lead to substantial component damage or unreliability, or risk of fire or explosion. In everyday life, experience of electrostatic shocks to personnel has become commonplace. This has led to an increasing need to understand such phenomena, and to specify materials, equipment and procedures for use in preventing and controlling electrostatic problems in the human environment. This technical report gives an overview of the field of electrostatics and has been prepared to give the user a view of the background, principles, methods of measurement and industrial applications prepared in conformity with IEC/TC 101 publications. This part of IEC 61340, which is a technical report, describes the fundamental principles of electrostatic phenomena including charge generation, retention and dissipation and electrostatic discharges. Methods for measuring electrostatic phenomena and related properties of materials are described in a general way. Hazards and problems associated with electrostatic phenomena and principles of their control are outlined. Useful applications of electrostatic effects are summarized. The purpose of this technical report is to serve as a reference for the development of electrostatics related standards, and to provide guidance for their end-users. Only the most common terms for electrostatics are listed and explained in this Technical Report. Special terms were not included, they can be found in the relevant standards. The main cause of electrostatic charging is triboelectric charging (frictional charging). If two previously uncharged substances come into contact, charge transfer will, in general, occur at their common boundary. On separation, each surface will carry an additional charge of equal magnitude but of opposite polarity. Conducting or dissipative objects can become charged by induction if they reside in an electrical field produced by other charged objects or conductors at high potential at their vicinity. Any object can become charged if charged particles or molecules accumulate on it. It is very important to have some appreciation of these phenomena in order to enable the proper implementation of test procedures and unambiguous interpretation of the resultant data. Further comments are included in this technical report with the descriptions of the individual test methods, where considered necessary. Electrostatic discharges vary greatly in type and their effect as causes of electrostatic problems can be very different. Discharges between metal structures, such as sparks between charged parts and earth, cause the worst damages. However, discharges from charged insulators can also be harmful. Breakdowns of the insulating layers of a semiconductor can occur for voltages lower than 50 V and other forms of damage such as local fusion of semiconductor material require only a few micro-joules of energy. An electrostatic discharge occurs when the electrostatic field exceeds the breakdown strength of the atmospheric gas, which is usually air. As a guide, the breakdown strength for flat or large radius surfaces 10 mm or more apart is about 3 MV/m under normal ambient conditions. Electrostatic discharges vary greatly in type and depend in a detailed way on the factors that cause them. The several types of discharges can be classified as described in this Technical Report, although the differentiation between the various types is not completely definitive. Electrostatic discharge (ESD) is a serious threat to electronic components and systems. Electronic components have a wide range of susceptibility to ESD. Examples of the most susceptible types include semiconductors, magneto-resistive (MR) heads, and thin film resistors. An electronic potential, as low as 10 V, can cause the failure of certain components. Due to this high susceptibility, it can be assumed that all types of electrostatic discharge can harm sensitive electronic components. ESD damage can result in immediate catastrophic failure, latent damage or soft damage. Catastrophic damage can result in immediate failure or degradation of a component, causing the component or the system to cease functioning or to no longer meeting the requirements. A component with a latent damage can have changes in its characteristics, but nevertheless meet the requirements. However, it can become weakened by the ESD event. A component with latent damage can be more susceptible to a succeeding ESD or any other stress. It is therefore an increased possibility that such a component will fail prematurely. Soft errors occur when a programmed component is exposed to an ESD and the installed data are changed. False signals can appear in the system, due to conducted or radiated electromagnetic interference sourced by an electrostatic discharge. In this report, reference is made even to useful applications of electrostatic effects. The ubiquitous photocopier and inkjet printer are two machines which contribute enormously to information technology. The electrographic process is entirely based on electrostatic effects and the inkjet printer uses the precise deflection of accurately sized and charged ink drops. In the former process, the optical image is transformed into a charge pattern on a corona charged photoconductor which is subsequently developed by the adhesion of counter-charged developer particles. The final stage is the transfer of the developed image on to the copy paper, again, by means of an electrostatic field. Corona charging of dust particles, the electrical properties of the captured effluent dust layers and the generation of stable high electric fields all contribute to the efficiency of electrostatic precipitators. Electrostatic painting, crop spraying, flocking and ore beneficiation and plastics separation are all either viable or burgeoning industrial processes. It is certainly the case that effective implementation of any means to control and utilize electrostatic effects is crucially dependent on quantitative data for the electrostatic parameters and relevant materials properties. The modifications of the first Corrigendum to IEC/TR 61340-1 from March 2013 have already been included in this consolidated German version. The responsible committee is DKE/K 185 "Elektrostatik" ("Electrostatics") of the DKE (German Commission for Electrical, Electronic and Information Technologies) at DIN and VDE.