JPH07318608A - Method for inspection of transistor - Google Patents

Abstract

PURPOSE:To provide a method for inspection of transistors capable of inspecting the good or bad of the transistors that constitutes an inverter in a condition wherein the transistors are set in the inverter without damaging the inspection accuracy. CONSTITUTION:The good or bad of transistors that form an inverter 10 is inspected in a condition wherein the transistors are set in the inverter 10. Only the transistor Q1 to be inspected in the condition wherein the transistors are set in the inverter 10 is controlled to be in an ON state. A prescribed value of current is allowed to a collector from a current source 1 during a time period whereby a junction temperature of the transistor Q1 rises to a prescribed level. When a difference between a collector-emitter saturation voltage of the transistor Q1 at a time when the prescribed value of current is allowed to flown to the collector from the current source 1 and that after the prescribed length of time has elapsed is in a prescribed range, it is judged that the transistor Q1 is good. Likewise, each of the transistor Q2-Q6 is inspected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transistor inspection method for inspecting the quality of a transistor which constitutes an inverter in a state of being incorporated in the inverter.

[0002]

The transistors that are built into the Related Art inverter in order to maintain the inverter reliability, the emitter of the transistor at room temperature - the collector saturation voltage - examination of the emitter current characteristic (V _CE -I _C characteristic), further predetermined It is necessary to inspect the V _CE -I _C characteristics of the transistor after the temperature is raised to the temperature. Therefore, from the state to inspect the quality of the transistors constituting the inverter constituting the inverter, and remove the transistor inspected transistor inverter, the curve tracer to V _CE -I _C characteristic of the inspected transistor characteristics It was drawn in the form of a curve, and the quality was judged by whether or not the characteristic curve was within a predetermined range from the reference V _CE -I _C characteristic curve of the transistor under inspection. The junction temperature ambient temperature the V _CE -I _C characteristic is the temperature of the joint portion, for example 25 ° C.
And in the case of 125 ° C. V _CE -I _C characteristic observed when the both temperatures both had a good time with the reference V _CE -I _C characteristic curve of the test object transistors within a predetermined range.

[0003]

However, when the conventional transistor inspection method as described above is used,
The transistor had to be removed from the inverter every time the transistor was inspected, and there was a problem that the number of steps required for the currently used inverter was extremely high. Furthermore, it is necessary to raise the temperature from room temperature (25 ° C.) to 125 ° C., which takes time. Further, there is a problem that a dedicated measuring instrument such as a curve tracer is required for measurement, and the number of man-hours for acceptance inspection of transistors is excessive in a mass production line for transistor inspection.

An object of the present invention is to provide a transistor inspection method capable of inspecting the quality of a transistor constituting an inverter in a state of being incorporated in the inverter without impairing inspection accuracy.

[0005]

SUMMARY OF THE INVENTION A transistor inspection method of the present invention is a transistor inspection method for inspecting the quality of a transistor which constitutes an inverter in a state where the transistor is incorporated in an inverter. Only the transistor to be inspected is controlled to the ON state, a current of a predetermined value is passed from the current source to the collector until the junction temperature of the transistor to be inspected reaches a predetermined temperature, and a current of a predetermined value is passed from the current source to the collector. When the difference between the collector-emitter saturation voltage of the transistor to be inspected and the collector-emitter saturation voltage of the transistor to be inspected at the time is within a predetermined range, the transistor to be inspected is determined to be non-defective. Is characterized by.

[0006]

According to the transistor inspection method of the present invention, only the transistor to be inspected in the state of being incorporated in the inverter is controlled to be in the ON state, and the collector of the transistor to be inspected receives a current of a predetermined value from the current source and the junction of the transistor to be inspected. The collector-emitter saturation voltage of the transistor to be inspected when the current is supplied to the collector of the transistor to be inspected at a predetermined value from the current source until the temperature reaches the predetermined value, and the transistor to be inspected after the lapse of the period When the difference between the collector-emitter saturation voltage of and the value within a predetermined range, the transistor to be inspected is determined to be non-defective. Therefore, the transistor to be inspected can be inspected in a state of being incorporated in the inverter, and the number of steps required for the inspection is reduced.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A transistor inspection method according to the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a block diagram showing a configuration of an inverter in a state in which a circuit for carrying out the method of the present invention is connected.

The inverter 10 includes transistors Q ₁ and Q ₂ connected in series and transistors Q ₃ and Q connected in series.
₄ , the transistors Q ₅ and Q ₆ connected in series, the control circuit 7 for controlling the transistors Q _{1 to} Q ₆ to be turned on and off at their respective timings, and the transistor Q ₁
And a flywheel diode D ₁ to D ₆ connected in parallel to each to Q _6, and is configured to apply a DC voltage to the series connected respectively of the transistor pair and the smoothing capacitor C _1.

A case of inspecting the transistor Q ₁ in the inverter 10 will be described.

The current from the current source 1 is connected through the switch means 2 and the ammeter 3 so as to be supplied to the point A to which the collector of the transistor Q ₁ is connected.
Ground point C to which the emitter of ₁ is connected. Further, the voltmeter 4 is connected so as to measure the voltage between points A and C, and the DC power source 5 is connected to the base of the transistor Q _1.
Is applied to control only the transistor Q _{1 in the} on state. The inverter 10 is deactivated, the switch means 2 is controlled to be in the ON state, and only the transistor Q ₁ is energized.

Here, the junction temperature of the transistor Q ₁ when the output current value of the current source 1 reaches the current value I _C from the start of energization is Tj (0), for example, 25 ° C., and the switch means 2 is an ammeter. It is set to turn off when the junction temperature of the transistor Q ₁ reaches Tj (t), for example, 125 ° C. after the current value measured by 3 reaches the current value I _C.

When the switch means 2 is turned on, the current flowing through the collector of the transistor Q ₁ gradually increases and is maintained at the predetermined current value I _C. The current value I _C is measured by the ammeter 3, the current flows from the collector of the transistor Q ₁ to the emitter, and the waveform of the collector current is shown in FIG.
As shown in (a). In FIG. 2A, the vertical axis shows the current value measured by the ammeter 3, and the horizontal axis shows the time measured from the time when the switch means 2 is turned on. The emitter of the transistor Q ₁ at the time of measuring the current value of the ammeter 3 reaches the current value I _C - collector saturation voltage V _CE (sat) {hereinafter, the emitter - emitter collector saturation voltage V _CE (sat) - Collector Voltage V
_CE , or simply V _CE } is measured by the voltmeter 4, and V _CE is as shown in FIG. 2 (b).

In this case, the current value from the current source 1 is such that when the collector current increases and reaches the collector current I _C , the junction temperature of the transistor Q ₁ is Tj (0), for example, still 25 ° C., The value measured by the voltmeter 4 when the collector current of the transistor Q ₁ reaches I _C is read. The measured value at this time is V _CE (0).

The current value of the current flowing out of the current source 1 is I _C
From the current source 1 when a predetermined period of time has elapsed, that is, when the junction temperature of the transistor Q ₁ reaches Tj (t), for example, 125 ° C., the switch means 2 is turned off. To stop the current supply. As a result, the current supply from the current source 1 to the collector of the transistor Q ₁ is cut off. The measured value of the voltmeter 4 at the time when the switch means 2 is controlled to the off state is read. The measured value at this time is V _CE (t). The V _CE of the transistor Q ₁ from the on state of the switch means 2 to the off state thereof is as shown in FIG. 2 (b).

The current flowing into the smoothing capacitor C ₁ flows only during a predetermined period when the switch means 2 is turned on, and the charging current does not flow after being charged to a constant voltage.
When is turned off, the discharge current from the smoothing capacitor C ₁ flows to the collector of the transistor Q ₁ , but it immediately drops and does not cause a measurement error.

The period from when the switching means 2 is turned on to when the current from the current source 1 reaches I _C is the transistor Q ₁
2B, which is a period until the junction temperature reaches Tj (0), for example, 25 ° C., and is referred to as an initial period in FIG. During the period from when the current from the current source 1 reaches the current value I _C until the switch means 2 is turned off, that is, the period when the current is maintained at the current value I _C , the junction temperature of the transistor Q ₁ is Tj ( 0), for example 25 ° C. to Tj (t),
For example, the period until reaching 125 ° C.
In (b), it is described as a heating period. This is because the junction temperature of the transistor Q ₁ is increased by energization during this heating period. If the relationship of FIG. 2B is shown by the relationship between the voltage V _CE and the collector current, as shown in FIG. _2C , the current value I _C is reached from the initial period and the current value I _C is maintained until the end of the heating period. The period during which the current value I _C is maintained is the heating period. The voltage V _CE (0) when the current from the current source 1 reaches I _C and the voltage V _CE (t) when the switch means 2 is off, that is, the junction temperature is Tj (t),
For example, if the difference from the voltage V _CE (t) when reaching 125 ° C. is ΔV _CE , then ΔV _CE {= V _CE (0) −V _CE (t)}
Is within a predetermined range, the transistor Q ₁ is judged to be normal.

Generally, the thermal resistance Zth of a normal diode is
(T) is published by the manufacturer and is defined as shown in equation (1).

[0019]

[Equation 1]

In the equation (1), P is the power consumed by the diode, and Tjd (0), Tjd (t), and Tad are the junction temperatures (Tjd (0), Tjd (t), and Tad) when the energization current reaches a predetermined current value from the start of energization. ° K), the junction temperature (° K) and the ambient temperature (° K) of the diode when the energization of a predetermined current value is continued for a predetermined period.

From the above, the power P to be dissipated in the diode to obtain the junction temperature Tjd (t) is obtained. From this, the power required to reach the target junction temperature can be obtained. In the above example, the energization time until the target junction temperature of 125 ° C. is obtained.

On the other hand, the junction temperature Tjd and the forward voltage Vf have the relationship shown in the equation (2).

[0023]

[Equation 2]

In the equation (2), n is an emission coefficient, k is a Boltzmann constant, q is an electron charge, If is a forward current, and Is is a saturation current.

Therefore, the junction temperatures are TJd (t) and Tjd.
The forward voltage at (0) is Vf (t), Vf
If (0), then ΔVf = {Vf (t) -Vf (0)}.
Becomes as shown in equation (3).

[0026]

[Equation 3]

It is known that the quality of the diode is determined from ΔVf with respect to Tjd (t) and Tjd (0). That is, when ΔVf is within the predetermined range, the diode is determined to be good.

It is known that a forward voltage drop having a correlation with the junction temperature is used for the transistor as in the case of the diode, and the current value I _C from the current source 1 is used.
Can be set, and further, the time for turning off the switch means 2, that is, the period for maintaining the current value I _C can be set.
Further, it is known that the quality of a transistor can be evaluated by ΔV _CE as in the case of a diode. Therefore, when ΔV _CE is within the predetermined range, the transistor Q ₁ is determined to be good, and when it is out of the predetermined range, it is determined to be defective.

By the way, when a single transistor is measured by a curve tracer, ΔV _CE {= V _CE (t) -V _CE when a current having the same waveform and the same current value as in FIG. 2A is passed _. The characteristics between (0)} and the current value I _C are the same as those in FIG. 2C, and ΔV _CE is within the predetermined range for the non-defective transistor.
In the case of a defect, ΔV _CE is out of the predetermined range, which confirms the above.

As described above, the quality of the transistor Q ₁ is determined in the state of being assembled in the inverter 10, so that the period required for the determination can be short.

Further, in the above example, Tj (0) was explained as 25 ° C., but it may be ambient temperature at the time of inspection. In this case, the current value I _C is set and the junction temperature of the transistor Q ₁ is set. Is Tj (t), for example 125
The maintenance time current value I _C may be maintained by obtaining the maintenance time until the temperature reaches ℃.

Further, in the above description, the case where the quality of the transistor Q ₁ is determined has been described as an example, but similar to the case of the transistor Q ₁ , other transistors Q ₂ ,
It is obvious that the quality of Q ₆ can be determined in the state of being connected to the inverter 10. When inspecting the quality of the transistors Q ₂ , ..., Q ₆ , the common connection point of the ammeter 3 and the voltmeter 4 is connected to the collector of the transistor to be inspected and the current from the current source 1 of the collector of the transistor to be inspected is connected. The voltage V _CE between the collector and the emitter of the transistor under test is measured, and the voltage of the DC power supply 5 is applied to the base of the transistor under test to activate only the transistor under test.

Further, since the heating time maintained at the current value I _C is, for example, about 1 second when the current value I _C = 400 A, instead of the ammeter 3 and the voltmeter 4, the current value I _C is changed.
_C and voltage V _CE are preferably obtained by simultaneously observing with a two-phenomenon oscilloscope or a two-channel digitizer. Further, the control of the switch means 2 to the off state is provided by providing a time constant circuit which is charged with a predetermined voltage after the switch means 2 is turned on and a comparison means for comparing the output voltage of the time constant circuit with a reference voltage. The voltage is applied for a predetermined time after the switch means 2 is turned on, for example, Tj (t).
Is set to the output voltage of the time constant circuit at the time of charging until reaching the junction temperature of, and the switch means 2 is set by the output of the comparison means when the output voltage at the time of charging the time constant circuit exceeds the reference voltage. It may be turned off.

[0034]

As described above, according to the transistor inspection method of the present invention, the transistor to be inspected can be inspected in the state of being incorporated in the inverter.
The man-hours for removing and re-assembling from the inverter are unnecessary, and there is an effect that the time and man-hours required for inspecting the transistors forming the inverter can be reduced.

Further, since it is possible to efficiently inspect only the finished product without inspecting the acceptance of the transistor in the mass production line, there is an effect that the number of steps is reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an inverter in a state in which a circuit for implementing a transistor inspection method according to the present invention is connected.

FIG. 2 is a schematic explanatory diagram for explaining a transistor inspection method according to the present invention.

[Explanation of symbols]

1 ... current source 2 ... switching means 3 ... ammeter 4 ... voltmeter 5 ... DC power source 7 ... control circuit 10 ... inverter C ₁ ... smoothing capacitor D ₁ to D ₆ ... flywheel diode Q ₁ to Q ₆
... transistor

Claims (1)

[Claims] 1. A method of inspecting a transistor for inspecting the quality of a transistor that constitutes an inverter in a state of being incorporated in an inverter, wherein only a transistor to be inspected in a state of being incorporated in an inverter is controlled to an ON state and a collector is provided. A current of a predetermined value is supplied from the current source for a period until the junction temperature of the transistor to be tested reaches a predetermined temperature, and a collector-emitter saturation voltage of the transistor to be tested when a current of a predetermined value is supplied to the collector from the current source A method of inspecting a transistor, wherein the transistor to be inspected is determined to be non-defective when the difference between the collector-emitter saturation voltage of the transistor to be inspected after the lapse of the period is a value within a predetermined range.