RU2087919C1 - Device for measuring junction-to-case thermal resistance of semiconductor diodes - Google Patents

Abstract

FIELD: semiconductor engineering. SUBSTANCE: device has initial current supply, heating current supplies, control-pulse generator, inverting amplifier-limiter, first detector of temperature-sensing parameter voltage, second detector of diode heating current and voltage, selective voltmeter, electronic switch, first diode heating current and voltage measuring mode switch, second switch for measuring voltage of temperature-sensing parameter and heating power components, low-value current-connecting resistor, and isolating capacitor. EFFECT: reduced hardware cost for measuring thermal resistance. 1 dwg

Description

 The invention relates to techniques for measuring the parameters of semiconductor diodes and can be used on output quality control and to assess their temperature reserves.

 The invention is aimed at solving the problem of reducing hardware costs and the time of measuring thermal resistance.

 A known method of measuring thermal resistance is the transition of the housing of the diodes (see, for example, GOST 19656. 15 84. Semiconductor microwave diodes. Methods of measuring thermal resistance of the transition of the housing and pulsed thermal resistance. P. 15, 16) using the dependence of the direct voltage of the diode on temperature during heating its direct current pulses, which consists in the fact that the diode under study is given a small direct initial current, excluding the self-heating of the diode, direct current heating pulses are fed to the diode, the dissipated diode power and measure the change in the forward voltage of the diode used as a temperature-sensitive parameter.

 The disadvantage of this method is the large error in measuring the amplitude of the voltage pulse of the diode, which varies exponentially, as well as the error caused by the influence of the residual potential on the diode.

 The closest in technical essence to the claimed invention is a device selected as a prototype (see, for example, Description of the invention to patent N 2003128, Sergeyev V.A. Yudin V.V. Method for determining thermal resistance transition of a case of semiconductor diodes. Publ. 15. 11 93. Bull. N 41 42), containing the studied diode, source of initial current, source of heating current, generator of control pulses, amplifier-limiter, voltmeter of actual value, oscilloscope, inverting amplifier-limiter, detector, selector ny voltmeter, current collection low resistance resistor, an electronic switch current and switch the measurement mode.

The disadvantage of the prototype is the large hardware costs for the implementation of the amplifier-limiter in automatic mode by restricting the measured signal from below to the value of the smallest envelope of current I _ogre and voltage across the diode U _ogre , which will be different for different types of diodes. When manually setting the levels of I _ogre and U _ogre , the measurement time increases.

 The purpose of the invention is the reduction of hardware costs when measuring thermal resistance.

 To achieve this goal, the claimed invention, a device for measuring thermal resistance, the transition of the case of semiconductor diodes contains the following general, defined by a specific concept, essential features, the totality of which is aimed at solving only one problem associated with the purpose of the invention, namely, the source of the initial current, the source of heating current, the control generator pulses, inverting limiter amplifier, temperature-sensitive parameter voltage detector, heating current detector and diode voltage, selective voltmeter, electronic current switch, switch for measuring the heating current and diode voltage, switch for measuring the temperature of the temperature-sensitive parameter and heating power components (heating current and diode voltage), collector low-resistance resistor, isolation capacitor.

In relation to the prototype of the claimed invention has the following distinctive features. In the prototype, the measurement of the heating current I and the voltage across the diode U, which are components when determining the heating power ΔP I • U and are complex waveforms, is possible only with automatic or manual limitation of the signal level by the value of the smallest amplitude of the envelope of the heating current or diode voltage. In the present invention, measurement is performed by the authors of modulating (envelope) of the heating current and the diode voltage and the waveform is taken into account in the final expression for determining heat resistance as a coefficient which depends on the pulse duration τ _and the heating current and the repetition period T, the values of which are known. Since the modeling signal is a simple harmonic signal, its measurement is possible with a selective voltmeter, used in the prototype only when measuring the voltage of a temperature-sensitive parameter.

The measurement of the modulating signal at a frequency of Ω _{m is} possible with the introduction of a second detector to demodulate the amplitude-pulse modulated heating current and voltage at the diode. The isolation capacitor C _{p is} designed to cut off the constant component of the heating current and the voltage of the diode. The second switch of the measurement mode switches the voltmeter from the voltage measurement mode of the temperature-sensitive parameter to the measurement mode of the heating power components.

Between the distinguishing features and the purpose of the invention there is the following causal relationship. To measure the components of the heating power ΔP, the second detector demodulates the heating current and the voltage across the diode. From the detector output, a signal at a modulation frequency Ω _m, for example, a heating current, has the form
i = (I _m sinΩ _m t + I _m ) + I _ogre , (1)
where I _{m the} amplitude value of the heating current,
I _{ogre is the} smallest amplitude of the envelope of the heating current.

где Т_м период модулирующего сигнала.In the expression (1) the sum of the currents in the parentheses represents the current being integral power increment ΔP _Res current I creates a heating capacity constant value and does not affect the determination of the thermal resistance. We rewrite expression (1) in the form
i = I _m sinΩ _m t + I _m (2)
The effective value of the heating current I is written as

where T _{m the} period of the modulating signal.

Решая выражение (4), получим выражение для действующего значения тока на выходе второго детектора
I_д= I_m(3τ_и/2T)^1/2 (5)
Выражая ток I_m через измеренное значение тока селективным вольтметром

окончательно получим выражение для греющего тока через измеренное действующее значение огибающей переменного тока

на частоте модуляции Ω_м в зависимости от скважности греющих импульсов

Учитывая, что изменение напряжения на диоде при подаче на него греющего тока по форме повторяет его, так как измерение осуществляется на линейном участке ВАХ диода, то по аналогии с греющим током I запишем измерение напряжения U через измеренное действующее значение напряжения

селективным вольтметром

Приращение греющей мощности

и выражение для определения теплового сопротивления переход корпус диодов будет иметь вид

где TKU известный температурный коэффициент напряжения температурочувствительного параметра,
К величина постоянная, входящие в нее параметры задаются предварительно

.Taking into account pulses modeled by amplitude and duration T (see, for example, G. Fikhtengolts, Differential and integral calculus course. Vol. 11, seventh edition. M. Nauka, 1969, p. 154)

Solving expression (4), we obtain an expression for the effective current value at the output of the second detector
I _d = I _m (3τ _and / 2T) ^1/2 (5)
Expressing current I _m through the measured current value selective voltmeter

we finally obtain the expression for the heating current through the measured effective value of the alternating current envelope

at a modulation frequency Ω _m depending on the duty cycle of the heating pulses

Considering that a change in the voltage on the diode when a heating current is applied to it in shape repeats it, since the measurement is carried out on the linear portion of the I – V characteristic of the diode, then, by analogy with the heating current I, we write the voltage measurement U through the measured effective voltage value

selective voltmeter

Heating power increment

and the expression for determining the thermal resistance of the transition case of the diodes will be

where TKU is the known temperature coefficient of voltage of the temperature-sensitive parameter,
K is a constant value, the parameters included in it are predefined

.

температурочувствительного параметра, так и при измерении тока

и напряжения

Измерение тока можно осуществить однажды перед измерением партии диодов.The second switch allows you to use a selective voltmeter as when measuring voltage

temperature-sensitive parameter, and when measuring current

and voltage

Current measurement can be done once before measuring a batch of diodes.

 According to the information available to the author, the set of essential features characterizing the essence of the claimed invention is not known from the prior art, which allows us to conclude that the invention meets the criterion of "novelty."

 According to the authors, the essence of the claimed invention does not follow explicitly from the prior art for the specialist, since the above effect on the obtained technical result of the new property of the object does not reveal the totality of features that distinguish the claimed invention from the prototype, which allows us to conclude that it the criterion of "inventive step".

и напряжения

обуславливающего достижение поставленной цели уменьшение аппаратурных затрат при измерении теплового сопротивления, что позволяет сделать вывод о соответствии изобретения критерию "промышленная применимость".The set of essential features characterizing the essence of the invention, in principle, can be repeatedly used in measuring the thermal resistance of semiconductor devices having a pn junction or a group of pn junctions (transistors, microcircuits, etc.) to obtain a technical result consisting in determination of the heating current I and the voltage across the diode U through the measured effective values of the current envelope

and voltage

causing the achievement of the goal to reduce hardware costs when measuring thermal resistance, which allows us to conclude that the invention meets the criterion of "industrial applicability".

 The invention is illustrated by graphic material (see drawing), which shows a block diagram of a device containing an initial current source 1, a heating current source 2, a control pulse generator 3, an inverting limiter amplifier 4, detectors 5 and 6, a selective voltmeter 7, studied ID diode, electronic current commutator CE, measurement mode switches K1 and K2, collector low-resistance resistor R, isolation capacitor Cf.

 The inventive device for measuring thermal resistance, the transition housing of the semiconductor diodes contains an initial current source 1, the output of which is connected to one of the switched inputs of the CE electronic switch, a heating current source 2, the output of which is connected to another switched input of the CE electronic switch, a control pulse generator 3, the output of which is connected to the control input of the electronic switch KE, the investigated diode ID, the first output of which is connected to the output of the electric of the FE switch, inverting the amplifier-limiter 4, the input of which is connected to the first output of the studied ID diode, a detector 5, the input of which is connected to the output of the amplifier-limiter 4, and the output with the first fixed contact of the second switch K2 of the measurement mode, detector 6, input which is connected to the movable contact of the first group of switch K1.1, and the output through the isolation capacitor Cp is connected to the second fixed contact of the second switch K2, a selective voltmeter 7, the input of which is connected to the movable contact of mutator K2, the current collection low resistance resistor R, connected to the second terminal of the diode and IDs associated with the second fixed contact K1.1 switch of the first group and the first contact of the second switch group K1. 2 and with a common power bus on the other hand, and the second contact of the second group of switch K1.2 is connected to a common power bus.

которое измеряется селективным вольтметром 7 на частоте модуляции Ω_м подключенным через контакты коммутатора К2, находящегося в положении

. При переключении коммутатора в положение измерения составляющих греющей мощности ΔP измеряются или напряжение на диоде

, или ток с токосъемного резистора

в зависимости от положения коммутатора К1 (U или I). Сигнал с диода ИД при закороченном резисторе R (при измерении напряжения диода U) или с токосъемного резистора R (при измерении греющего тока I) демодулируется детектором 6. Конденсатором Ср отсекается постоянная составляющая сигнала и селективным вольтметром измеряется напряжение сигнала, соответствующее огибающей напряжения на диоде

или греющего тока

на частоте модуляции Ω.In the process, the source of the initial current 1 generates a constant current I _beg. , and the source of the heating current is 2 current, which varies in harmony with the modulation frequency Ω _m and has a constant component exceeding I _m (see, for example, expression (1) of the description of the invention). The generator of control pulses 3 generates pulses of duration τ _and and the repetition period T, fed to the control input of the electronic switch KE. During the action of a pulse of duration τ _and from the output of the electronic switchboard QE, the pulse of the heating current arrives at the anode of the investigated ID diode, the amplitude of which changes according to the harmonic law. During the pause between pulses τ _{p the} current d I receives the current I _beg . The current pulses at the collector resistor R are converted into voltage pulses. When measuring the voltage across the diode U, the collector resistor R is shorted by the contacts of the switch K1.2. The same voltage is supplied to the input of the inverting amplifier-limiter 4 and the detector 5 detects the voltage of the temperature-sensitive parameter

which is measured by a selective voltmeter 7 at a modulation frequency Ω _m connected through the contacts of the switch K2, located in position

. When the switch is switched to the measurement position of the heating power components ΔP, the diode voltage is measured or

, or current from a collector resistor

depending on the position of the switch K1 (U or I). The signal from the ID diode with a shorted resistor R (when measuring the voltage of the diode U) or from the collector resistor R (when measuring the heating current I) is demodulated by the detector 6. The constant component of the signal is cut off by the capacitor Cp and the signal voltage corresponding to the envelope of the voltage across the diode is measured with a selective voltmeter.

or heating current

at the modulation frequency Ω.

 To determine the thermal resistance of the junction of the investigated diode case, the measured values are substituted into expressions (6), (7) and (8) of the description of the invention.

 As shown by the results of a pilot test, when using the inventive device for measuring thermal resistance, the transition of the case of semiconductor diodes provides a reduction in hardware costs.

 According to the data of the experiments, the claimed invention can be used in the national economy and in comparison with the prototype has the following advantages, namely, the overall dimensions of the device have significantly decreased, its price and increased reliability.

 The inventive device for measuring the thermal resistance of the transition - the case of semiconductor diodes is of considerable interest to the national economy, as it will simplify the measurement procedure.

 The claimed solution does not adversely affect the state of the environment.

Claims (1)

 A device for measuring the thermal resistance of a junction box of semiconductor diodes, containing an initial current source in the form of a direct current source, a heating current source in the form of a pulse source modulated in harmonic law with a period of an order of magnitude greater than the thermal time constant of the junction of the studied diode connected through a switching contact electronic current commutator to the diode in series and a collector low-resistance resistor, a control pulse generator, connected by an output to the control input of the electronic current commutator, an inverting limiter amplifier connected by an input to the diode under study, and by an output through a first detector with a selective voltmeter, in addition, the first measurement mode switch, the first fixed contact of the first group of which is connected to the common point of the first output of the studied a diode, an electronic switch, and an inverting amplifier-limiter, and the second fixed contact is connected to the common point of the second terminal of the diode under study, low resistance a plug-in resistor and a first contact of the second group, the second contact of which is connected to a common terminal of the circuit, characterized in that a second detector, a second measurement mode switch and a separation capacitor are introduced, while the input of the second detector is connected to a movable contact of the first group of the first measurement mode switch, and the output of the second detector through a separation capacitor is connected to the first fixed contact of the second switch of the measurement mode, the second fixed contact of which is connected to the output of the first etektora and its stationary contact connected to the input of the selective voltmeter.