RU2724148C1 - Method of measuring thermal resistance of transition-case of power semiconductor devices - Google Patents

Abstract

FIELD: control and measuring equipment.SUBSTANCE: invention relates to control and measurement equipment, in particular, to measurement of thermal parameters of power semiconductor devices (PSD) in housing design. Semiconductor crystal is heated by passing through it direct current of the specified amplitude I. During heating the value I and voltage drop U on the tested device are measured. Value of heating power P is calculated by expression P=IU. After time t equal to three times the thermal constant of the device design t=3τ, the heating current source is switched off. Simultaneously, a measuring current source is connected and the value of the heat-sensitive parameter is measured at the moment of heating current source disconnection, which is represented by direct voltage drop on the Ucrystal. After time t=3τat the end of the process of natural redistribution of heat accumulated by the semiconductor crystal along the structure of the device design, including the solid body of the housing of the instrument housing, the value of the heat-sensitive parameter Uis repeatedly measured. Obtained values are used to calculate the difference U-Uand determine the difference between the transition and the case temperature of the test device K⋅(U-U)=T-T, where Kis the value of the temperature coefficient of the forward voltage. Value of heat resistance transition-case Ris calculated as ratio of obtained values T-Tand power P.EFFECT: providing nondestructive control of thermal resistance of a transition-case PSD, shorter measurement time and ultimately increasing yield of articles in a process cycle of their serial production.1 cl, 8 dwg

Description

The invention relates to a control and measuring technique, in particular, to a method for measuring the thermal resistance of the transition-case of power semiconductor devices by the transition function of the heat-sensitive parameter and can be used in the technique of measuring the thermal parameters of power semiconductor devices (SPP) in the housing design.

State of the art

A known method of controlling the thermal regime of power semiconductor devices, including the use of the concept of transitional thermal impedance (see Ershov A.B., Khorolsky V.Ya., Atanov I.V., Efanov A.V. // Electrical Engineering, No. 3, 2019. p. 14-19).

The disadvantage of this method of controlling the thermal regime of power semiconductor devices is the need for direct control of the temperature value of the housing of the device.

Known method for measuring the thermal resistance of a transition-body diode, based on dependence of the forward voltage of the diode at a constant current of temperature, comprising the steps of that through a controlled diode passes straight initial current I _nach small quantities, excluding appreciable self-heating of the diode, is then fed to the diode heating pulse direct current of the same amplitude I _m and duration τ _u , the power dissipated in the diode is measured, and in the intervals between the heating current pulses, the change in the direct voltage of the _TP diode U, used as a temperature-sensitive parameter, is measured (see GOST 19656. 15-84 Microwave semiconductor diodes. Methods of measuring the thermal resistance of the transition-case and pulsed thermal resistance).

The disadvantage of this method is the low accuracy due to the large measurement error of the pulse voltage U _TP (t) due to the influence of transient thermal and electrical processes when the diode switches from one mode - heating mode to another - measurement mode (see, for example, I. Vikulin ., Stafeev V.I. Physics of semiconductor devices - M: Sov. Radio, 1980.P. 51).

A known method for determining the thermal resistance of the transition-case of semiconductor diodes, which consists in applying to the controlled diode heating current pulses, in the intervals between which a constant initial current is passed through the diode and the change in the direct voltage of the diode is measured, in measuring the heating power and determining the thermal resistance from the obtained values, moreover, the amplitude of the heating current pulses is modulated according to a harmonic law with a period that is an order of magnitude higher than the transition-case thermal constant for a given type of diode, and the change in the temperature-sensitive parameter - the direct voltage of the diode and heating power is determined by measuring the amplitudes of the alternating current components and the voltage at the modulation frequency ( see RF patent 2003128 for the invention "Method for determining the thermal resistance of the transition-case of semiconductor diodes // V.A. Sergeev, V.V. Yudin - Bull. 41-42, 1993).

The most significant drawback of this method is the long measurement time, which is (taking into account the need to measure several electrical quantities at the modulation frequency) several hundred thermal transition time-case time constants for this type of diode. When used in devices that implement the method, selective voltmeters with a narrow passband, the measurement time increases by several times.

Another significant drawback of the known method is the complexity of the hardware implementation, due to the complexity of the simultaneous measurement of several analog signals at a low or infralow frequency.

(см. пат. RU №2240573, МПК G01R 31/26, опубл. 20.11.2004 г.).The closest in technical essence and the achieved positive effect and adopted by the authors for the prototype is the express method for measuring the thermal resistance of the junction-case R _thjc power semiconductor devices (SPP) in the housing _design , in which the test device is heated with direct current to a predetermined (based on the transition temperature of the device did not exceed 125 ° C) of the temperature of the device body. Then, in the cooling interval at the time t = 3τ _0, simultaneously with fixing the temperature of the instrument case, the values of the temperature-sensitive parameter are also fixed, which is used as the value of the voltage drop across the crystal of the device. The fixed value of the heat-sensitive parameter is converted using the linear dependence of the temperature coefficient of the forward voltage into the corresponding value of the transition temperature. The calculation of the thermal resistance of the transition-case (R _thjc ) of the SPP is carried out according to the ratio of the difference between the temperatures of the transition and the case of the SPP to the amount of power allocated to the device by a constant heating current

(see Pat. RU No. 2240573, IPC G01R 31/26, published on November 20, 2004).

This express method allows you to:

- dramatically reduce, compared with the regulatory methods for determining the parameter R _thjc , the measurement time;

- reduce hardware, energy and labor costs when testing the stability of SPP to static thermal overloads.

The disadvantages of this rapid method are:

- the need for direct control of the temperature value of the housing of the device, and therefore this method is a method of destructive testing and does not provide the possibility of continuous control of the specified parameter;

- the need to heat the housing of the SPP to a temperature of <125 ° C, which, combined with the need to install a temperature sensor on the base of the device body, causes a significant (few minutes) time to determine the desired parameter. At the same time, when the device is heated to a temperature of <125 ° C, the difference between the transition temperature T _j (semiconductor crystal) and the device body T _c , determined by the transition-to-case static resistance R _thjc and, accordingly, the accuracy of its determination, will not increase compared to the state at which the case of the device has not yet warmed up to a temperature significantly higher than the ambient temperature.

прибора в установившемся тепловом режиме, когда измеряемая температура не изменяется по отношению к окружающей среде.Thus, the thermal resistance of the transition-case (R _thjc ) SPP is defined as the ratio of the difference between the transition temperature (T _j ) and the temperature of the case (T _c ) SPP at a controlled point to the power dissipation

instrument in steady-state thermal mode when the measured temperature does not change with respect to the environment.

For SPP, they are currently normatively installed (see GOST 24461-80. Power semiconductor devices. Methods of measurement and testing), [Silicon rectifier diodes for currents 10, 25, 50 and 80 A. Specifications TU IDZHK.432312.011 TU-LU. Introduction date 05/30/2014] two methods for measuring the thermal resistance of the junction-case [1 p. 2.8.4.1, p. 2.8.4.2] with heating the device with a source of heating direct current and with heating the environment, respectively, the procedure for which measures the temperature of the case the device in a steady thermal state using a thermocouple and a DC potentiometer with a thermocouple immersion depth in the body of the device body at a control point, for example, for power silicon diodes of a pin design like 2D412-10, 2D412-10X, 2D422-25, 2D422-25X, 2D432- 50, 2D432-50X, 2D432-80, 2D432-80X (1.5 ± 0.5) mm [2 p. 6.3.4], and at the end of the test procedure, the devices are rejected. The calculation of the thermal resistance R _thjc , in particular for the design of power devices with one-sided cooling, is performed according to the expression:

where T _j is the transition temperature, indirectly determined by the value of the measured voltage drop across the device at the time of switching off the heating direct current source and simultaneously connecting the measuring current source; T _with - the temperature of the housing of the device, measured using a thermocouple at the time of shutdown of the heating current source; I, U - current and voltage drop on the device at the moment of reaching the established heat balance

These methods of measuring the thermal resistance of the transition-housing SPP have the following disadvantages:

1. are destructive control methods;

2. Designed for random control and do not provide continuous control of the specified parameter;

3. due to the duration of reaching a steady state of heat between the housing of the SPP and the environment, these methods require a long time to determine the specified parameter;

4. require significantly greater hardware, energy and labor costs.

нормативно установлен (см. ГОСТ 19656.15-84. Диоды полупроводниковые СВЧ. Способы измерения теплового сопротивления переход-корпус и импульсного теплового сопротивления) способ ([3, п. 2 Способ измерения

с использованием зависимости прямого напряжения диода от температуры и разогревом импульсами прямого тока]) в соответствии с которым как температура корпуса прибора, так и температура его перехода определяются косвенно - по функции термочувствительного параметра, в качестве которой используется зависимость прямого падения напряжения на приборе от его температуры. При этом, приращение температуры перехода по отношению к установившейся в результате разогрева прибора импульсами прямого тока температуре корпуса испытуемого прибора обеспечивается в результате рассеивания в СВЧ диоде определенной мощности импульса прямого тока. Изменение прямого напряжения диода СВЧ под действием импульса прямого тока показано на фиг. 1, [3, Черт. 3].To measure the thermal resistance of the transition-housing of semiconductor microwave diodes

normatively installed (see GOST 19656.15-84. Microwave semiconductor diodes. Methods for measuring the thermal resistance of the transition-case and pulsed thermal resistance) method ([3, p. 2 Method of measurement

using the dependence of the direct voltage of the diode on the temperature and heating by direct current pulses]) in accordance with which both the temperature of the device case and the temperature of its transition are determined indirectly by the function of the heat-sensitive parameter, which is used as the dependence of the direct voltage drop on the device on its temperature . Moreover, the transition temperature increment with respect to the temperature of the case of the device under test, which is established as a result of heating of the device by direct current pulses, is ensured by the dissipation of a certain direct current pulse power in the microwave diode. The change in the forward voltage of the microwave diode under the action of a forward current pulse is shown in FIG. 1, [3, Damn. 3].

The pulse repetition period T is chosen from the condition:

where τ _T is the thermal time constant of the design of the device.

выбирают из условия:Impulse duration

choose from the condition:

The indicated method for measuring the thermal resistance of the junction-case does not provide for a procedure for directly measuring the temperature of the case of a microwave device, which is why it is a method of non-destructive testing of this parameter. However, due to the fact that the measurements must be made in a state of heat balance between the temperature of the instrument housing and the ambient temperature, this method has all the other disadvantages of the above regulatory methods for determining the thermal resistance of the transition-housing SPP. It is very important that, due to the considered features, the indicated procedure for determining the thermal resistance of the transition-case of semiconductor microwave diodes is quite lengthy.

A feature of the design of powerful SPPs in the housing design, due to the need to ensure thermal stability to the effects of sharp dynamic current overloads, is the presence of a massive base of the device body, which has a high heat capacity. This design provides relatively fast absorption of energy by the massive SPP body emitted in the semiconductor crystal during short-term current overload with further slow transfer of excess accumulated energy to the environment.

When the SPP is heated by direct current, the heat flux from the semiconductor crystal through the soldered layer propagates to the massive body of the power device and further into the surrounding space. To increase the efficiency of heat removal from the SPP housing to the surrounding space, radiators of natural air cooling, forced air cooling, liquid cooling systems, etc. are usually used. The use of forced cooling systems can significantly reduce the value of the thermal resistance of the housing-environment. The efficiency of heat removal from the semiconductor crystal to the SPP case in practice is mainly determined by the quality of the junction of the crystal with the SPP case. A eutectic alloy or a soldered layer, if they are of poor quality, can provide significant thermal resistance to the heat flux propagating through the physical structure of the SPP. Therefore, monitoring the thermal resistance of the SPP is one of the most effective ways to control the quality of this most important technological operation, along with monitoring the devices for vibration resistance, vibration resistance and thermal cycling, and the inability to fully control this parameter in the process of mass production of devices makes the entire existing monitoring system flawed.

With sufficient accuracy for practice, the thermal processes under consideration are described using equivalent thermal models from R _i C _i - chains, where R _i is the thermal resistance [C / W], C _i is the heat capacity [J / ° C], τ _i = R _i C _i is the thermal time constant of the i-th chain. The number and connection scheme of the used circuits of the equivalent thermal model is determined by the design of the corresponding type of SPP and the requirements for the accuracy of modeling of thermal processes. For uncontrolled power switches (power diodes), a chain with a thermal time constant τ ₀ = R ₀ C ₀ corresponds to the structure of the first soldered layer (semiconductor crystal - solder). Accordingly, τ ₁ = R ₁ C ₁ is the second (solder is the massive copper base of the device body), τ ₂ = R ₂ C ₂ is the third (the base of the device body is the cooler (radiator)). To increase the efficiency of heat removal from the base of the device to the cooler (radiator), heat-conducting paste is usually used.

при последовательном соединении R_iC_i - цепочек и нагреве прибора постоянным током определяется суммой показательных функций с параметрами эквивалентной тепловой модели:The rate of establishment of thermal equilibrium is determined by the values of thermal time constants R _i C _i - chains. Total transient thermal resistance of the device

when R _i C _i - chains are connected in series and the device is heated by direct current, it is determined by the sum of exponential functions with parameters of the equivalent thermal model:

- at the stage of heating the device

- at the stage of cooling the device

значительно меньше теплоемкости основания корпуса прибора

Теплоемкость паяного слоя

настолько мала по сравнению с величиной теплоемкости основания корпуса прибора

что ее обычно не учитывают. Выражения (4) и (5) для переходного теплового сопротивления переход-корпус прибора Z_thjc(t) в этом случае преобразуются к виду:It is characteristic for the construction of an SPP that the specific heat of a semiconductor crystal

significantly less heat capacity of the base of the device

The heat capacity of the soldered layer

so small compared to the heat capacity of the base of the device

that it’s usually not taken into account. Expressions (4) and (5) for the transitional thermal resistance of the transition-case of the device Z _thjc (t) in this case are converted to:

- at the stage of heating the device

- at the stage of cooling the device

From the expressions (6) and (7) it follows that the value of the static thermal resistance of the transition-housing SPP is determined by the value (R ₀ + R ₁ ), i.e. almost the quality of the soldered connection of the semiconductor crystal with the base of the device body. The function of establishing the transition temperature of the SPP T _j (t) is determined by the expression:

Graphically, this dependence has the form shown in FIG. 2.

при этом разность между данными температурами перестает изменяться T_j(t)-T_c(t)=const, a Z_thjc(t)=R_thjc. На этапе нагрева прибора температура перехода (кристалла полупроводника) прибора вначале быстро (по экспоненциальной зависимости) достигнет температуры соответствующей величине мощности, выделяемой в кристалле греющим током Р=IU, а затем медленно температура корпуса прибора будет увеличиваться до температуры кристалла полупроводника. Аналогично, на этапе остывания температура перехода (кристалла полупроводника) вначале быстро, (по экспоненциальной зависимости) достигнет температуры корпуса прибора, а затем медленно температура перехода (кристалла полупроводника) и температура основания корпуса прибора будут уменьшаться до температуры окружающей среды. При этом если корпус прибора не разогревать до температуры окружающей среды, то при отключении греющего тока по истечении времени t>3τ₀ наступит устойчивое тепловое равновесие между температурами перехода, основания корпуса прибора и окружающей среды. В этом состоянии величина падения напряжения на переходе прибора (величина термочувствительного параметра) будет практически соответствовать температуре корпуса прибора и окружающей среды (фиг. 3).For exponential expressions (6) and (7) at t> 3τ _{0, the} exponential terms become negligible both at the stage of heating the device with direct current and at the stage of its cooling when the heating current is turned off. At the stage of heating the device with a heating current at t> 3τ _0, further exposure to the heating current leads only to a slow proportional increase in temperatures T _j (t) and

the difference between these temperatures ceases to change T _j (t) -T _c (t) = const, and Z _thjc (t) = R _thjc . At the stage of heating the device, the transition temperature (semiconductor crystal) of the device first quickly (exponentially) reaches the temperature corresponding to the power released in the crystal by the heating current P = IU, and then the temperature of the device body slowly increases to the temperature of the semiconductor crystal. Similarly, at the cooling stage, the transition temperature (of the semiconductor crystal) first quickly (exponentially) reaches the temperature of the instrument case, and then the transition temperature (of the semiconductor crystal) and the base temperature of the instrument case decrease slowly to ambient temperature. Moreover, if the instrument case is not heated to ambient temperature, then when the heating current is switched off after a time t> 3τ _0, a stable thermal equilibrium will occur between the transition temperatures, the base of the device case and the environment. In this state, the magnitude of the voltage drop at the junction of the device (the value of the thermosensitive parameter) will practically correspond to the temperature of the device body and the environment (Fig. 3).

греющего тока при определении величины теплового сопротивления прибора и определяют саму теоретическую возможность определения данного параметра по динамике теплового состояния прибора как в режиме его разогрева, так и в режиме его охлаждения. Однако в режиме разогрева величина падения напряжения на приборе определяется величиной греющего тока. Это практически делает несостоятельной процедуру определения искомого значения R_thjc в данном режиме. В режиме же охлаждения прибора он не подвергается воздействию греющего тока и может быть подвержен воздействию измерительного тока, величина которого не оказывает существенного значения на изменение его температуры.The exponential nature of functions (6) and (7) makes demands on the duration of the exposure interval

heating current when determining the value of the thermal resistance of the device and determine the very theoretical possibility of determining this parameter from the dynamics of the thermal state of the device both in its heating mode and in its cooling mode. However, in the heating mode, the value of the voltage drop across the device is determined by the value of the heating current. This practically makes the procedure for determining the desired value of R _thjc in this mode _inconsistent . In the cooling mode of the device, it is not exposed to the heating current and may be affected by the measuring current, the value of which does not significantly affect the change in its temperature.

Disclosure of invention

The objective of the invention is to develop a method for determining the thermal resistance of the junction-case power semiconductor devices (SPP) by the transition function of a heat-sensitive parameter with the possibility of operational non-destructive control of the value of R _thjc , and also has the immediate goal of providing continuous continuous quality control of the technological operation of soldering a semiconductor crystal to the base of the power semiconductor device housing in a hydrogen furnace and at the same time to ensure the maximum reduction in control time, hardware, energy and labor costs.

The technical result that can be achieved using the proposed method is to ensure the possibility of non-destructive and, thus, continuous control of the value of R _thjc , and at the same time to maximize the reduction of control time, hardware, energy and labor costs.

силового полупроводникового прибора.The technical result is achieved using a method for determining the thermal resistance of the transition to the housing of the SPP by the transition function of the heat-sensitive parameter, namely, that the semiconductor crystal is heated by passing a constant current of a given amplitude I through it, the value of the heating current I and the voltage drop U on the tested device are measured when passing through the heating current, calculate the value of the heating power P by the expression P = IU, after a time t equal to the triple value of the thermal constant of the device design t = 3τ _{T, the} heating current source is turned off, while at the moment the heating current source is turned off, the measuring current source is connected and the value is measured the transition function of the heat-sensitive parameter at the time of switching off the heating current source, which is used as a direct voltage drop on the crystal U _np1 , in the mode of natural redistribution of heat accumulated by the semiconductor crystal over the structure and the device including the massive body of the base of the device body after a time t equal to the triple value of the thermal constant of the device design t = 3τ _T , then re-measure the value of the transition function of the heat-sensitive parameter U _np2 , calculate the difference U _np1 -U _np2 , multiply the obtained value by a predefined the value of the temperature coefficient of the direct voltage K _T , thus obtaining the desired difference between the transition temperatures and the case of the device _under test K _T ⋅ (U _np1 -U _np2 ) = T _J -T _C and the value of the thermal transition-case resistance is calculated from the obtained values

power semiconductor device.

Однако, в отличие от экспресс-метода измерения величины теплового сопротивления переход-корпус СПП в корпусном исполнении (см. патент RU №2240573) нагрев корпуса прибора постоянным греющим током производится не до фиксированного значения температуры (<125°С), а до величины практически не превышающей температуру окружающей среды (см. фиг. 4).Thus, the technical result is achieved by using the procedure for determining the value of the thermal resistance of the transition-housing according to the dynamic characteristic of the transitional thermal resistance of the device

However, unlike the express method of measuring the thermal resistance of the transition to the housing of the SPP in the housing design (see patent RU No. 2240573), the heating of the device housing with a constant heating current is not carried out to a fixed temperature (<125 ° C), but to a value practically not exceeding the ambient temperature (see Fig. 4).

In the proposed method, the temperature of the case of the device and the temperature of its transition are determined indirectly by the function of the heat-sensitive parameter, since this happens when determining this parameter with the above method of determining it for microwave diodes. However, obtaining the function of the heat-sensitive parameter does not occur as a reaction to the effect of a separate rectangular pulse of the heating current under the influence of a sequence of such pulses, but as a reaction to the effect of a negative jump in the constant (heating) current with a value comparable to the value of the rated current of the device when it is turned off, t. e. reactions to the effects of transient function. The maximum reduction in the time required to measure the desired parameter is achieved by heating the semiconductor crystal not to a thermal state at which the temperature of the device’s case is much higher than the ambient temperature, but to a temperature of the device’s case at which it practically does not exceed the ambient temperature, i.e. to the a priori initially existing thermal balance between the temperature of the instrument case and the ambient temperature.

где

- тепловая постоянная времени конструкции прибора, зависящая от конкретного типа СПП. Данная величина для конкретного типа СПП определяется экспериментально по переходной функции термочувствительного параметра.The transition heating time (semiconductor crystal) is determined from the condition

Where

- thermal time constant of the design of the device, depending on the specific type of SPP. This value for a specific type of SPP is determined experimentally by the transition function of the heat-sensitive parameter.

производится в момент непосредственно предшествующий отключению греющего тока по измеренным величинам греющего тока I и падения напряжения на приборе U, обусловленного протеканием греющего тока

Determination of heating power

is made at the moment immediately preceding the shutdown of the heating current according to the measured values of the heating current I and the voltage drop on the device U, due to the flow of the heating current

The determination of the transition temperatures at the time of switching off the heating current and at the time t = 3τ is made by the value of the thermosensitive parameter, which is the magnitude of the voltage drop across the device U, due to the flow of the measuring current. To transfer the value of the heat-sensitive parameter to the corresponding value of the transition temperature, a linear dependence of the heat-sensitive parameter on the transition temperature is used (Fig. 5), which determines the value of the temperature coefficient of the forward voltage during the flow of direct current K _T.

The value of the temperature coefficient of the direct voltage at the transition K _T for a particular type of SPP is practically unchanged and is determined by the expression:

This value shows the change (decrease) in the voltage drop at the junction of the device with an increase in its temperature by 1 ° C.

In practice, to calculate the value of the thermal resistance of the junction-case R _thjc, there is no need to calculate the values of the transition temperatures T _j and the housing of the SPP T _s . In accordance with the expression [1], it is sufficient to determine the difference in the recorded values of the corresponding values of the heat-sensitive parameter, the multiplication of which by the value of K _T will give the value T _j -T _e .

The calculation of the thermal resistance R _thjc , in particular for the design of power devices with one-sided cooling, is performed according to the expression (1).

Brief description of drawings and other materials

In FIG. Figure 1 gives a method for determining the thermal resistance of the transition-case of power semiconductor devices, using the transition function of the heat-sensitive parameter, shows the diagrams of the heating current and direct voltage drop at the transition of the microwave diode in the process of determining the value of the thermal resistance of the transition-case of the microwave diode according to GOST 19656.15-84.

In FIG. 2, also, plots of the graphs of the dependence of the transition temperatures T _j (semiconductor crystal) and the case of the SPP T _c when exposed to direct direct current for a time exceeding the triple value of the thermal time constant of the design of the device are shown.

In FIG. Figure 3 also shows diagrams of the plots of the dependence of the direct direct current acting on the device over a time exceeding the triple value of the thermal constant of the device design time, the voltage drop across the device due to the influence of the measuring current on it and the corresponding dependence of the transition temperature T _j (semiconductor crystal).

In FIG. 4, also, the practically obtained transient function of the thermosensitive parameter for the 2D422-25 rotor diode (manufacturer Optron-Stavropol AO) is shown when the test device is exposed to direct heating direct current for a time equal to the triple value of the thermal time constant of the device design.

In FIG. 5, also, the practically obtained dependence of the thermosensitive parameter on the transition temperature for the 2D422-25 rotor diode (manufacturer Optron-Stavropol AO) is determined, which determines the value of the temperature coefficient of direct voltage during direct current flow K _T.

In FIG. 6, also, a block diagram of the device is shown, performed on a digital signal processing controller that automatically implements the algorithm of the proposed method for determining the value of thermal resistance transition-housing SPP, the front panel of the device.

In FIG. 7, also, a table, the results of monitoring the magnitude of the thermal resistance of the transition-housing SPP for a sample of 25 devices.

In FIG. 8, too, control of thermal resistance by tightened standards.

The implementation of the invention

The technical implementation of the proposed method for determining the magnitude of the thermal resistance of the transition-housing power semiconductor devices by the transition function of the heat-sensitive parameter in the housing design is as follows:

At the initial stage, data on the types of tested SPPs containing the values of the nominal heating current I _loaded are entered into the program for the digital signal processing controller _{dsPIC33EP128GP.} , heating time of the tested devices with a given current t _load. and the magnitude of their temperature coefficient of direct voltage K _T.

The front panel of the device contains a digital signal processing controller 1 dsPIC33EP128GP, a keypad button, a Select button 2, an LCD display 3, a display panel 4, a port 5 expander, a matching interface device 6, a tested power semiconductor device 7, a contacting device 8, a power switch 9 , matching the interface device 10, the source 11 of the heating current, the outputs of the measuring shunt 12, the scaling device 13 controls the magnitude of the voltage drop 13, the source 14 of the secondary power supply.

At the first measurement stage (see Fig. 6), the dsPIC33EP128GP digital signal processing controller 1, using the "Select" button 2, enters the data on the type of tested SPP 7. The input of this information is controlled by visualizing them on the LCD display 3 and the display panel 4. Display panel 4 contains light indicators (LEDs) (not shown in FIG.) For each of the types of devices under test, light indicators accompanying the measurement cycle, an indication of the absence of the device under test in the contacting device and its inoperability “Device marriage”. The selection process for the type of instrument under test is accompanied by a short beep. Controller 1 controls the display elements through the port expander of the controller 5 and matching interface device 6.

At the second stage, at the command of the operator, using the “RUN” button (not shown in Fig.), The test SPP 7, previously fixed in the contacting device 8 with the power key 9, is connected to the stabilized source 11 of the heating source 11 through the matching interface device 10 by the digital signal processing controller dsPIC33EP128GP 1 current. At the same time, the outputs of the measuring shunt 12 and the scaling device (MU) 13 for controlling the voltage drop to measure the values of the heating current and the direct voltage drop on the tested device 7 are connected to the inputs of the ADC of the controller 1. At the moment of switching on the heating current source 11, the first program timer is turned on.

(единицы микросекунд) величина падения напряжения на испытуемом приборе

фиксируется и заносится в оперативную память контроллера 1. Далее контроллер 1 производит расчет величины

и заносит рассчитанную величину в оперативную память контроллера 1. Одновременно включается третий программный таймер.At the third stage, the heating time of the tested device t _{load is} monitored _. , the value of the heating current I _load. and direct voltage drop on it U _np. . After the set heating time of the tested power semiconductor device 7 by the heating current, the value of the heating current and the voltage drop on the tested device 7 are recorded and entered into the RAM of the controller 1 for subsequent calculation of the value of the heating power (IU = P). Next, the heating current source 11 is turned off and at the same time the second program delay timer for monitoring the voltage drop on the tested device 7 for the transient in the input circuit of the ADC of the controller 1 is turned on. At the same time, in order to increase the accuracy of measuring the voltage drop at the break point of the first kind of function U _j (t) the frequency of sampling the signal increases by a multiple. After the delay time

(units of microseconds) the voltage drop across the instrument under test

fixed and entered into the RAM of controller 1. Next, controller 1 calculates the value

and enters the calculated value into the RAM of controller 1. At the same time, the third program timer starts.

помещения ее в оперативную память контроллера 1 и производится фиксация момента достижения данной величины.In the fourth stage are controlled moment of reaching the voltage drop across the test device 7 values 0,368U _j (t _LOAD. + T _ass.) And the time to reach a given value, counting it from the moment of switching on the third software timer. The value thus determined corresponds to the value of the thermal time constant of the device τ _T. This value is entered into the RAM of controller 1. Next, the fourth program timer is turned on, and the value is calculated

placing it in the RAM of controller 1 and fixing the moment it reaches this value.

в момент

Данная величина заносится в оперативную память контроллера 1.At the fifth stage, the value of the voltage drop on the tested device 7 is fixed

in the moment

This value is recorded in the RAM of the controller 1.

Полученная разность значений термочувствительного параметра умножается на соответствующую величину температурного коэффициента прямого напряжения К_T. Рассчитанное таким образом значение соответствует разности температур перехода и корпуса СПП. Искомое значение величины теплового сопротивления переход-корпус R_thjc рассчитывается в соответствии с выражением (1) как отношение разности температур перехода и корпуса СПП к величине ранее определенной греющей мощности Р. Рассчитанная величина теплового сопротивления переход-корпус СПП выводится на экран LCD дисплея 3.At the sixth stage, the controller 1 calculates the value of the thermal resistance of the transition-housing of the SPP and displays this value on the LCD screen 3. At the beginning, the value of the heating power P is calculated from the values of the voltage drop measured at the third stage of the tested power device 7 U when flowing through it heating current I and the value of this current according to the formula IU = P. Then, the difference in the values of the voltage drops across the tested power device 7 is determined at the time of switching off the heating current source 11 and at the moment

The obtained difference in the values of the heat-sensitive parameter is multiplied by the corresponding value of the temperature coefficient of the forward voltage K _T. The value calculated in this way corresponds to the temperature difference between the transition and the housing of the SPP. The desired value of the value of the thermal resistance of the transition to the housing R _{thjc is} calculated in accordance with expression (1) as the ratio of the difference between the temperatures of the transition and the housing of the SPP to the value of the previously determined heating power P. The calculated value of the thermal resistance of the transition to the housing SPP is displayed on the LCD screen 3.

Table 1 below shows the results of monitoring the thermal resistance of the transition to the case of 2D422-25 rotor diodes for a sample of 20 devices by the proposed method, by heating the device to a fixed value of the temperature of the device case (patent RU No. 2240573) and the results of independent monitoring according to tightened standards.

The above control results indicate that both methods provide sufficient practical accuracy for determining the desired parameter. However, the proposed method due to the lack of the need to integrate a thermal sensor into the body of the device body allows non-destructive testing of this parameter by replacing the next controlled device in the contacting device and pressing the RUN button by the operator. The time for displaying the control result on the LCD screen 3 does not exceed units of seconds.

A more detailed analysis of the proposed method made it possible to identify important features of various approaches to its technical implementation:

1) Due to the fact that the magnitude of the measuring current does not have a practical effect on the heating of the semiconductor crystal of the device 7, it is possible to connect the source (in Fig. Not shown) of the measuring current simultaneously with the connection of the heating current source 11. However, due to the fact that in this case the greatest influence on the accuracy of determining the desired value of the thermal resistance of the transition-housing of the SPP at the time of switching off the heating current source 11 is exerted by the sampling frequency of the signal, it becomes necessary to increase this frequency in order to ensure the required accuracy.

где

- тепловая постоянная времени конструкции прибора 7 практически не успевает происходить. Датчики температуры (на фиг. не показаны) данный нагрев не регистрируют.2) From a formal point of view, heating of the base of an SPP case should begin simultaneously with heating of the semiconductor crystal of the device and, in contrast to heating a semiconductor crystal, not linearly, but exponentially. However, in practice, due to the fact that the thermal capacity of the semiconductor crystal is so small compared with the thermal capacity of the base of the device casing 7, the heating of the base of the device casing at the moment of turning on the heating current source 11 and up to

Where

- the thermal time constant of the design of the device 7 practically does not have time to occur. Temperature sensors (not shown in FIG.) Do not register this heating.

The invention in comparison with the prototype and other and well-known technical solutions has the following advantages:

- providing the possibility of non-destructive and, thus, continuous control of the value of R _thjc ;

- ensuring the maximum reduction in control time, hardware, energy and labor costs.

Claims (1)

The method for determining the thermal resistance of the transition to the housing of the SPP by the transition function of the heat-sensitive parameter, namely, that the semiconductor crystal is heated by passing a constant current of a given amplitude I through it, the value of the heating current I and the voltage drop U on the test device during the passage of the heating current are measured, calculate the value of the heating power P according to the expression P = IU, after a time t equal to the triple value of the thermal constant of the device design t = 3τ _T , the heating current source is turned off, characterized in that at the time the heating current source is turned off, the measuring current source is connected and the value is measured the transition function of the heat-sensitive parameter at the time of switching off the heating current source, which is used as a direct voltage drop on the crystal U _np1 , in the mode of natural redistribution of heat accumulated by the semiconductor crystal over the structure of the device, including massive the body of the base of the device’s body, after a time t equal to the triple value of the thermal constant of the device’s design t = 3τ _T , then re-measure the value of the transition function of the heat-sensitive parameter U _np2 , calculate the difference U _np1 -U _np2 , multiply the obtained value by a predetermined temperature forward voltage coefficient K _T , thus obtaining the desired difference between the transition temperatures and the case of the device _under test K _T ⋅ (U _np1 -U _np2 ) = T _J -T _C and the value of the transition-housing thermal resistance is calculated from the obtained values

power semiconductor device.

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