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Über dieses Buch

This book on electrostatic discharge phenomena is essentially a translation and update ofa Swedish edition from 1992. The book is intended for people working with electronic circuits and equipments, in application and development. All personnel should be aware of the ESD-hazards, especially those responsible for quality. ESD-prevention is a part of TQM (Total Quality Management). The book is also usable for courses on the subject. Background It was soon realised that the MOS-circuits (MOS=Metal Oxide Semiconductor), which appeared in the beginning of the 1960-ties were sensitive to electrostatic discharges. But a severe accident accelerated the search for materials that do not generate electric charges. In April 1964 three people were working inside a satellite at Cape Kennedy Space Center. They suddenly screamed "we are burning". They died. The satellite incapsulation was covered with untreated plastics to protect against dust. When the plastics was pulled off both this and the metal incapsulating got charged. A discharge from the metal ignited inflammable parts of the satellite. Eleven more people were injured and the cost of the accident amounted to about 55 billions USD.

Inhaltsverzeichnis

Frontmatter

1. The discovery of static electricity and its manifestation

Abstract
Already in the stone age our ancestors were fascinated by the mysterious phenomenon of static electricity. Thales from Miletos (mathematician) described about 600 years B.C. how the material amber could become ”animated” and attract dust and down. In 1600, William Gilbert, English physician and physicist, published his famous work ”De magnete” the first scientific treatment of magnetic and electric phenomena, pointing out their different character. He also postulated that earth is a great magnet.
Sten Hellström

2. Relation to electronics

Abstract
In the first chapter was shown how static electricity, i.e. electric charges can be created. These charges are transferable by different ways to electronic components.
Sten Hellström

3. ESD-testing and models

Abstract
In the 60-ties a very high vulnerability of the new discrete MOS-components was realised. They failed often without any apparent reason. A thorough failure analysis of damaged components started to settle failure mechanisms. This led to the understanding that electrostatic discharges caused voltage breakdown in the thin silicon gate oxide of the MOS-circuits. The accidents happened during the handling of the circuits. The operators had been charged triboelectrically and by touching some pin of the circuit a discharge destroyed it. The thickness of the oxides was normally about 1000 Å, corresponding to a breakdown voltage 100V. The failure mode was often a short circuit between gate and source or drain. About 50% of all failures were caused by ESD.
Sten Hellström

4. Susceptibility for ESD

Abstract
In respect of the performance and included application of electronic components different requirements as to ESD-susceptibility are given. Some are given in MIL-Std-883C others in STACK, a mainly European norm. Test performances are found in them. This cannot prevent any company or other users to formulate its own requirements. Fig. 51 can serve as a guidance. Fig. 52 gives thresholds.
Sten Hellström

5. Failure analysis

Abstract
By failure analysis it is possible to find out what has happened to a component that does not function properly and why. Only the failure mechanisms being known the cause of failure can be eliminated. Thus avoiding future problems. The more severe the consequences of a failure is the more important it is to deduce the causes.
Sten Hellström

6. Latent failures

Abstract
The concept latent failure related to electronic circuits implies that some kind of damage occurred, but the circuit is still functioning within specification. The word latent comes from the word “latents” = hidden. In this context it means that either the life-time of the circuit is shortened or that it will fail for a minor stress, that would not harm an undamaged circuit. The French expression for latent failure is “defaillance potentielle” (potential failure). This phenomenon has become rather important as results of ESD-stresses, though it can have other causes.
Sten Hellström

7. Indirect ESD

Abstract
In the preceding chapters phenomena associated with electrostatic discharges into or inside circuit elements (direct ESD) were treated. Damages are caused by currents (diffusion, melting) or voltage (breakdown).
Sten Hellström

8. Other types of perturbations in electronics

Abstract
Noise is the most common perturbation in electronics. Taken in its most wide sense any disturbance or signal apt to hide the proper signal characterizes a noise phenomenon. It can be so called ripple from the current supply due to insufficient filtering. Noise is generated in microphones from vibrations of its components. Signals from outside can interfere with signals inside a system. Certain perturbation phenomena are able to be suppressed or totally eliminated, other are beyond control. The most well-known source of noise is, however, the thermal motion of the electrons in electronic components. This has a statistical character and appears both in active and passive components. Likewise the proper signal the noise is amplified!
Sten Hellström

9. The impact of electric fields and electromagnetic waves on the organism

Abstract
Since the very beginning of creation we are surrounded by different forms of radiation. Sunshine and cosmic radiation. The former is of electromagnetic character, while the latter also contains particles of very high energy. Radioactive radiation emanates partly from the earth surface. This often contains uranium and thorium with their daughter products (as radium with the gas radon). It is anticipated that the ions in the air are created mostly by radioactive irradiation from the earth.
Sten Hellström

10. Simulation methods

Abstract
The temperature is a crucial factor in the damaging of components, exposed to ESD-transients. A way to study the influence of the temperature is to simulate mathematically the behavior of components, when stressed by electrical transients.
Sten Hellström

11. Protection methods — Antistatic materials

Abstract
In the sixties MOS-components were regarded as very ESD-sensitive. But when new component technologies were introduced, especially IC:s, it was realised that other circuit elements could be sensitive to ESD. The narrow conductors, the small distances between circuits and the thin oxide layers increase the sensitivity. Now all kind of electronic components even passive, are considered sensitive to ESD. This has started activities to avoid or preferable eliminate ESD hazards. A general measure in that direction is to increase the relative humidity (RH-value). By that otherwise insulating surfaces are rendered slightly conductive, thus counteracting charge formation. Alternatively ionizers can be used producing ions that neutralize charge of opposite sign, a method often used in clean rooms. The aim is to create an ESD-safe environment. But these actions are often not enough. This chapter will describe all protection methods. Another early measure was to supply electronic circuits with special protection circuits, incorporated in the circuitry. The function of them is to reduce voltage and currents of transients to a harmless level and dissipate energy developed by them.
Sten Hellström

12. Failure frequency and costs for ESD

Abstract
Information about the frequency of ESD-failures, both in production and field use, is of great importance. Due to high costs for the necessary, time — consuming failure analysis sufficient data can be difficult to get.
Sten Hellström

Backmatter

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