摘要:

The current problems of assessing the reliability of semiconductor devices are discussed, and reference is made to the order of reliability required in typical applications.The evidence from life tests carried out on devices drawn from production lines of transistors and diodes shows how variations in operating conditions and assessment levels affect the apparent reliability of the devices. This type of appraisal gives a useful guide to the reliability of semiconductor devices in typical service use.The incidence of inoperative failures, the trends shown by measurements of major characteristics during life, and the form of life-survival curves are discussed, and a brief reference is made to the equipment used in carrying out the tests.

DOI:10.1049/pi-b-2.1959.0177

出版商:IEE    

年代:1959

数据来源: IET

摘要:

A total of 660 transistors, purchased to a specification involving 100% initial testing, including damp heat cycling, have been placed on life test in groups with junction temperatures at 50, 60, 70, 80, 90 and 100°C, with power dissipations such as to give junction temperature rises of 0, 10 or 20°C above the temperature of the mounting, and with collector voltages of 0, −1, −4 and some of −20 volts. From the data so far accumulated and analysed it appears that most of the units will end their lives owing to excessive rise of collector leakage current, that there is no significant correlation between life and initial value of collector leakage current, and that positive correlation exists between deterioration of noise figure at 1 kc/s and deterioration of leakage current, the deterioration being markedly more common for units aged at the higher voltages.

DOI:10.1049/pi-b-2.1959.0178

出版商:IEE    

年代:1959

数据来源: IET

摘要:

An experimental study is described of the effect of various forms of surface contamination upon the slow growth of excess reverse current in germaniump-njunctions (‘creep effect’).

DOI:10.1049/pi-b-2.1959.0179

出版商:IEE    

年代:1959

数据来源: IET

摘要:

The widespread use of semiconductor rectifiers, with their extremely high conversion efficiency, ability to operate at high reverse voltages and consequent small size, has brought in its train problems peculiar to these devices. It is most important, therefore, that the electrical ratings should be established on both a systematic and rigorous basis with the specific problems in mind.Certain electrical parameters such as forward and reverse voltage and current, thermal resistance and junction temperature, have obvious effects on the electrical rating of the rectifier. Others, such as thermal capacitance and carrier storage time, affect the rating indirectly, but are no less important.In the paper, some of the factors which influence the rating of germanium and silicon junction rectifiers are considered, and the procedure for obtaining the curves of rectified current rating as function of ambient temperature is given. Determination of overload characteristics and the associated use of thermal-electrical analogue techniques are described. Methods for deriving the derating factor for parallel operation, operation at higher mains frequency and at high altitude are also given.

DOI:10.1049/pi-b-2.1959.0180

出版商:IEE    

年代:1959

数据来源: IET

摘要:

Two theories of breakdown mechanism in silicon junction diodes have at present been advanced, avalanche and field emission, one by Zener and the other by Von Hippel and Fröhlich. At various times physicists have supported one or the other of these theories operating independently, but the development of the low-voltage silicon reference diode has indicated that the two methods of breakdown can occur simultaneously.An explanation of the peculiar behaviour of the voltage/temperature coefficient of such diodes can be made by incorporating both breakdown mechanisms. It is shown that very-close-tolerance devices must be used in experimental work.Comparison of the breakdown theories with experimental results shows that the breakdown of diodes at voltages less than 4.5 volts is due to field emission, greater than 6.5 volts is due to avalanche effects, and between 4.5 and 6.5 volts is due to a combination of both effects.Confirmation of these results is made by noise measurements.A characteristic surface of temperature coefficient of breakdown voltage shows skew properties which suggests that a diode having zero temperature coefficient over a wide range cannot exist for the currents and voltages considered.

DOI:10.1049/pi-b-2.1959.0181

出版商:IEE    

年代:1959

数据来源: IET

摘要:

The emitter-base forward characteristic with the collector at base potential is given as the physical boundary line of the initial region of the collector and emitter characteristics, respectively, in the common-emitter circuit. Using two examples, the formation of the initial region of the emitter and collector characteristics, respectively, of constant input voltage is examined and explained. The emitter-current/collector-voltage curve at constant input voltage is discussed. The rise of emitter current at constant input voltage is explained by a decrease in input resistance, caused by the collector-base forward current. The decrease of emitter current in the region of small collector voltages arises from the increase in the charge carrier concentrations at the collector junction, by which the gradient of the charge carriers between emitter and collector is smoothed and thus the current is decreased. To explain the collector characteristics a current distribution factorAxis defined in the initial region, the value of which is in approximate agreement with the current gainAbeyond the initial region. With the current distribution factor so defined and using the collector-base forward characteristic, we can construct, with the aid of the emitter characteristics, a family of collector characteristics which, within the range of the accuracy of measurement, corresponds to the measured values. The dependence of the envelopes limiting the collector characteristics to small collector voltages and of the collector voltage, whose collector current is zero, upon the geometry of the transistor is explained.A simple construction of the envelope is shown.Steep envelopes and small collector voltages forIC= 0 may be obtained by means of a high current gain, a small distance between base and emitter and as little overlapping of the projections of base and collector as possible.

DOI:10.1049/pi-b-2.1959.0182

出版商:IEE    

年代:1959

数据来源: IET

摘要:

The paper discusses the properties of a junction transistor which determine the limits of the three basic ratings, namely the maximum collector voltage, collector current and power dissipation, and describes methods of measurement. The effects of the limitations on the various circuit configurations are also discussed.The maximum value of both the direct and alternating voltages that may be applied to a transistor are dependent upon the variation of the characteristics with voltage. The most important of these factors are surface leakage, avalanche multiplication and collector/ emitter punch-through. The last is an absolute limitation whereas the first two result in a variation of the current gain and output impedance. The effects of these variations are very dependent upon the circuit arrangement and the possible parameter tolerances. The collector leakage current can also result in thermal instability. In general the important value of the leakage current, from the circuit-performance aspect, is that at high temperature. However, to simplify measuring and for life considerations, a low-temperature test may be more suitable.The maximum current rating is normally determined by the decrease in current gain at high emitter currents. Again this limitation is dependent upon the circuit arrangement and it is not possible to set an absolute limit. For linear-amplifier applications the variation of current gain with emitter current should be low, whereas, in switching applications, only the gain at high current is of importance.The power dissipation rating of a transistor is basically determined by the effect of a high internal temperature on its life. However, a convenient method of expressing the rating, as a function of ambient temperature, is by means of a maximum junction temperature and a thermal resistance. Since the total thermal resistance is dependent upon the mounting arrangements, the user must consider both the electrical and thermal properties of any transistor circuit. The transient power rating of a transistor is also of importance in many switching circuits.

DOI:10.1049/pi-b-2.1959.0183

出版商:IEE    

年代:1959

数据来源: IET

摘要:

In a previous paper the authors have described the principle of a method for studying the recombination surface of a transistor. This paper discusses the physical concepts on which the method is based, and outlines how it may be applied, in conjunction with other techniques, to the systematic study of the effects of any surface treatment. Some practical details of the apparatus and techniques are described and the value of the method is illustrated by an example.

DOI:10.1049/pi-b-2.1959.0184

出版商:IEE    

年代:1959

数据来源: IET

DOI:10.1049/pi-b-2.1959.0186

出版商:IEE    

年代:1959

数据来源: IET

摘要:

The paper reviews, from the viewpoint of design engineers, various approximations to the common-base intrinsic current gain of junction transistors. The basis of this comparison is the familiar expression for α derived directly from the semiconductor diffusion and continuity equations.A 2-pole approximation is considered in detail. It is shown that both the sinusoidal and transient response predicted using this expression is in good agreement with that predicted using the exact theory. For most practical transistors the parameters of this approximation remain reasonably constant.In the response to a step function of emitter current, the 2-pole equation closely describes the initial time delay arising from the transit time of minority carriers across the base region. The collector response to unit charge inserted into the base in the form of σ function also gives good agreement with the results obtained from the exact theory.The various approximations are compared by graphical presentation of the results.

DOI:10.1049/pi-b-2.1959.0187

出版商:IEE    

年代:1959

数据来源: IET