JPH08111446A - Temperature measuring apparatus at junction of semiconductor device - Google Patents

Abstract

PURPOSE: To detect a defective product correctly by providing a memory circuit for periodically sampling & holding the voltage at a P-N junction of a semiconductor device a plurality of times during an interval when a current sufficiently higher than a normal current is fed, and means for displaying the output from the memory means. CONSTITUTION: During an interval TS, a switch 5 is turned ON to feed a chip 1 with power thus heating the chip 1. During an interval TS, the switch 5 is turned OFF and during the turn OFF interval, a sampling switch 7 is turned ON to sample & hold the base-emitter voltage VBE of a transistor Q. Power supply and sampling of VBE are repeated alternately and the VBE is measured repeatedly for one chip 1. The sampled & held VBE is expressed in terms of temperature and presented on an oscilloscope 11. Since variation of voltage at a P-N junction (temperature at P-N junction) can be grasped when a semiconductor device is heating, detecting bonding of the semiconductor device can be detected correctly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring the temperature of a junction in a semiconductor device such as a transistor.

[0002]

2. Description of the Related Art In manufacturing a transistor, a chip 61 of a transistor is bonded to a frame 60 as shown in FIG. 6 and it is inspected whether or not the bonding is correctly performed. Insufficient bonding makes it difficult for the heat generated in the transistor to be transferred to the frame when power is applied to the transistor, so that the temperature of the junction (PN junction) of the transistor increases and the transistor is destroyed.

Therefore, such defectively bonded transistors must be disposed of as defective products.
Since the temperature at the junction has a correlation with the base-emitter voltage V _BE of the transistor, the bonding state can be indirectly known by looking at V _BE . In addition, in FIG. 6 and FIG.
B is a base, E is an emitter, and C is a collector.

In the conventional measuring device shown in FIG. 8, first, the switch 80 is turned off so that only 1 mA of the first constant current source 81 flows through the transistor, and V _BE is measured.
Next, the switch 80 is turned on to allow a large current to flow from the second constant current source 82 to the transistor for a certain period of time.

That is, in this conventional example, a pulse is applied to the measuring circuit 83 at time t1 in FIG. 9 to measure the V _BE of the transistor. Next, the switch 80 is turned on and power is applied for a certain time W as shown in FIG. At this time, if the bonding is normal, the heat is sufficiently transferred to the frame 60, so that the temperature of the transistor rises at a predetermined inclination. If the bonding is inadequate, the heat transfer will be poor and the transistor temperature will be quite high.

[0006] After a period W plus the power, it weighed again V _BE at time t2, measuring the difference between V _BE at t1.
Note that the higher the transistor temperature, the smaller V _BE . In this way, V _BE by adding power
It is possible to determine whether or not the bonding is sufficient by observing the magnitude of the change in In FIG. 9, (c)
Is a good product with correct bonding.
Is a defective product with insufficient bonding.

[0007]

However, this conventional example has the following drawbacks. That is, in this method, it is possible to make a judgment only before and after the power is applied, and the change in the middle cannot be understood. Therefore, some defective products may pass the inspection as non-defective products.

For example, in the case of a defective product, the temperature rises greatly with the application of power, but due to the heating, the insufficient contact state between the chip 60 and the solder 70 is temporarily improved, and as shown in FIG. The chip 61 drops to the frame 60 side, and the temperature of the chip 61 once drops and then rises again as shown in FIG. Then, at the time point (t2) when the power is switched, the temperature is almost the same as that of the non-defective product, so that the product is determined to be the non-defective product in spite of the defective product.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a semiconductor junction temperature measuring device capable of reliably finding a defective product.

[0010]

In order to achieve the above object, the measuring apparatus of the present invention comprises a current supplying means for supplying a semiconductor device with a current sufficiently larger than that during the normal operation of the semiconductor device; PN of the semiconductor device during
A storage circuit that periodically samples and holds the voltage of the junction multiple times; and a display unit that displays the output of the storage circuit are provided.

Further, the measuring apparatus of the present invention comprises: a first current supply means for supplying a predetermined current to the semiconductor device; a second current for supplying the semiconductor device with a current sufficiently larger than the first current supply means. Supply means; pulse generation means for generating a pulse for periodically operating the second current supply means; sample-hold circuit for sample-holding the voltage of the PN junction of the semiconductor device; and each time the pulse ends. And a sampling pulse generation circuit that outputs a sampling pulse that is delayed from the end.

In this case, further, there is provided means for continuously applying the sampling pulse to the sample hold circuit after the pulse is deenergized. The semiconductor device is a bipolar transistor, and the voltage of the PN junction is base
It is the voltage between the emitters.

[0013]

According to the structure of the present invention, the measuring device is provided with a current supply means for supplying a sufficiently large current to the semiconductor device as compared with the normal operation of the semiconductor device; and a PN of the semiconductor device during the period of supplying the current. Since a storage circuit for periodically sampling and holding the voltage of the junction portion a plurality of times; and a display means for displaying the output of the storage circuit are provided, the PN junction portion is provided within a period in which a large current is applied to the semiconductor device. Will be measured many times.

Also, first current supply means for applying a predetermined current to the semiconductor device; second current supply means for applying a current sufficiently larger than the first current supply means to the semiconductor device; and second current supply means. Pulse generating means for generating a pulse for periodically operating the current supplying means; a sample-hold circuit for sample-holding the voltage of the PN junction of the semiconductor device; When the sampling pulse generating circuit that outputs the generated sampling pulse is provided, the timing control of heating or measurement is performed by the pulse. Furthermore,
Since the sampling pulse is delayed from the time when the pulse for supplying a large current is deenergized, the voltage of the PN junction (and thus the PN junction Temperature) is measured.

Further, when the means for continuously supplying the sampling pulse to the sample and hold circuit after the pulse is deenergized is provided, the semiconductor device is no longer heated (a large current is not supplied), and thus the PN junction portion is no longer heated. You can see the temperature drop.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing the configuration of this embodiment. In the figure, for a chip 1 of a bipolar transistor Q bonded to a frame, a DC power supply 2A is connected between its collector and base, and a DC power supply 2B and a first constant current source 3 are connected between its emitter and base. Along with
A series circuit of a second constant current source 4 and a switch 5 is connected to both ends of the first constant current source 3.

Here, the first constant current source 3 is 1 mA in order to measure the base-emitter voltage V _BE of the transistor Q.
A constant current I ₁ is constantly supplied, and when the switch 5 is turned on, the second constant current source 4 supplies a large current I ₂ within several tens mA to several A so as to apply power to heat the chip 1. To do. Reference numeral 6 is a buffer whose input terminal is connected to the base and emitter of the transistor Q and which receives the base-emitter voltage V _{BE of the} transistor. Reference numeral 7 is a switch for sampling the output of the buffer, and 8 is a capacitor for holding the sampling output.

Therefore, the switch 7 and the capacitor 8 form a sample hold circuit. Reference numeral 9 denotes a conversion circuit that converts the base-emitter voltage V _BE of the sample-held transistor into temperature and outputs the same. The output is supplied to the oscilloscope 11 through the output terminal 10 of the measuring device.

In the present embodiment, during the period TP of FIG. 2, the switch 5 is turned on to apply power to the chip 1 to heat the chip 1. Next, the switch 5 is turned off during the TS period,
During this OFF period, the sampling switch 7 is turned ON to sample and hold the base-emitter voltage V _BE of the transistor Q. This power supply and V _BE capture are repeated alternately, and one chip 1 can receive V power many times.
Measure _BE .

The sample-held V _BE is converted into temperature and is displayed on the oscilloscope 11. A voltage as shown in FIG. 2B is applied to the oscilloscope 11, but TP has a short time interval of 19.8 ms and TS has a time interval of 0.2 ms. It appears as a continuous waveform.

FIG. 3 shows the conversion circuit 9, output terminal 10,
A concrete example concerning a portion excluding the oscilloscope is shown. Here, the same parts as those in FIG. 1 are designated by the same reference numerals. The first constant current source 3 is a junction FET
The second constant current source 4 is composed of MOS transistors 14 and 17 and resistors 15 and 16 which are connected as shown in the figure. Reference numeral 18 is a pulse generation source for generating a positive pulse P for the switch, and the positive pulse P has a pulse width corresponding to the TP period of FIG. 2 described above.

During the period of the positive pulse P, the transistor 14 is turned on.
N The resistors 15 and 16 are turned on by turning on the transistor 14.
Since a current flows through, a positive voltage is applied to the gate of the transistor 17. Therefore, the transistor 17 is also turned on.
To do. When the transistor 17 turns on, the transistor 1
The gate voltage of 4 is a voltage obtained by dividing 5 V, which is the peak value of the positive pulse, by the resistance of the resistor 9 and the resistor when the transistor 17 is conducting.
Therefore, the current flowing through the transistor 14 is the variable resistor 16
It becomes a constant value depending on the setting value of.

The sampling switch 7 is composed of a light emitting diode 41 and a photo MOS transistor 42. When the light emitting diode 41 is turned on, the photo switch M is turned on.
The OS transistor 42 is turned on. The switch control circuit 20 controls the light emitting diode 41.
Is.

The switch control circuit 20 receives the pulse P from the pulse generator 18 and generates a pulse P1 of 50 μs width in synchronization with the fall of the pulse P as shown in FIG. It has a vibrator 21 and a second mono-multivibrator 22 which generates a pulse P2 having a width of 50 μs in synchronization with the falling edge of the output pulse P1 of the first mono-multivibrator 21. The pulse P2 is given to the switch 7, and the switch 47 is turned on during the period of the pulse P2.

In this way, the pulse P delayed without turning on the switch 7 immediately in synchronization with the fall of the pulse P
It turns on in 2 immediately after the pulse P is deenergized (that is, immediately after the large current is cut off while the large current is flowing).
The reason is that there is a transient disturbance in the current flowing through the transistor Q, and if V _BE is measured at that time, a correct value may not be read. Therefore, after waiting for the current to settle down, that is, after 50 μs has passed after the deenergization of P, the switch 7 is turned on to read (sample) V _BE .

Reference numeral 23 is a free-run oscillator, which is generated at a cycle substantially the same as that of the pulse P, and which has a sampling switch 7
Turn on. However, during the period in which the pulse P is repeatedly generated, the reset is continued and no output is generated. The pulse P is integrated through the line 27 by the resistor 28 and the capacitor 24 to give a positive DC bias to the base of the transistor 25. Therefore, the transistor is turned on, and the reset terminal 26 of the free-run oscillator 23 is fixed to the ground potential.

Therefore, the free-run oscillator 23 does not operate. Therefore, the switch 47 is not controlled by the free-run oscillator during this period. However, when the pulse P is no longer generated after the preset heating period passes, the transistor 25 is turned off and the reset terminal 26 is supplied with the voltage VCC from the power supply line 29, so that the free-run oscillator 23 oscillates. Generate a pulse.

FIG. 5 illustrates this. As shown in FIG. 4A, when the heating pulse P is deenergized and the time constant determined by the resistor 28 and the capacitor 24 has passed (that is, in the range B), the pulse P3 of the free-run oscillator 23 is generated. To do. Only one P2 is generated after the pulse P is deenergized and is not output thereafter.

Even after the pulse P is deenergized in this way,
The reason why V _BE is sampled at P3 is as follows. That is, since P2 does not occur after P is deenergized, V _BE cannot be newly sampled. Therefore, the output of the sample hold circuit remains constant.

However, since the P is deenergized and the power is turned off, the temperature of the chip should be lowered. Therefore,
The pulse P3 is used to sample how the temperature of the chip has dropped. In this case, the pulse P3 may have a pulse width of about 200 μs.

That is, in the case of P2, power is applied,
Since it is used after the power is turned off, the pulse width is narrow because it is selected to occur 50 μs after the fall of the pulse P so as not to be affected by the transient state, but in the case of P3, P is Since it does not exist, the transient phenomenon itself does not exist, so it has the same width (200μ) as TS.
m).

In FIG. 5A, while A is heating,
The measurement period is shown, and B shows the measurement during the period when heating is no longer performed. Further, FIG. 5C shows a waveform (temperature information waveform) displayed on the oscilloscope 11, in which the heating characteristic can be seen in the period A and the cooling characteristic can be seen in the period B. Instead of the oscilloscope 11, a TV monitor, a printer or the like may be used.

[0033]

As described above, the measuring apparatus according to the present invention, as set forth in claim 1, is a current supply means for supplying a semiconductor device with a current sufficiently larger than that during normal operation of the semiconductor device; P of the semiconductor device during the given period
Since a storage circuit that periodically samples and holds the voltage of the N-junction portion; and a display unit that displays the output of the storage circuit are provided, a PN junction is provided during a period when a large current is applied to the semiconductor device. Since the voltage of the part is measured many times, it is possible to grasp the change in the voltage of the PN junction (and thus the temperature of the PN junction) when the semiconductor device is heated. Therefore, a defective bonding or the like of the semiconductor device can be correctly detected.

According to a second aspect of the present invention, there is provided a measuring device comprising: a first current supplying means for applying a predetermined current to the semiconductor device; and a current sufficiently larger than the first current supplying means. Second current supplying means for giving to the device; pulse generating means for generating a pulse for periodically operating the second current supplying means; sample and hold circuit for sampling and holding the voltage of the PN junction of the semiconductor device A sampling pulse generating circuit that outputs a sampling pulse that is generated after each end of the pulse, the sampling pulse being generated later than the end of the pulse, so that in addition to the above effects, the timing of heating and measurement can be controlled by the pulse. There is. Furthermore, since the sampling pulse is delayed from the point of deenergization of the pulse for supplying a large current, the voltage of the PN junction (and thus the PN junction The effect is that the temperature of the part) can be measured.

Further, since the measuring apparatus of the present invention comprises means for continuously applying the sampling pulse to the sample-hold circuit after the pulse is deenergized as described in claim 3, the semiconductor device is no longer heated (larger). It can be understood that the temperature of the PN junction portion is lowered even in the state where no current is supplied).

[Brief description of drawings]

FIG. 1 is a schematic circuit diagram of a junction temperature measuring device for a semiconductor device embodying the present invention.

FIG. 2 is a signal waveform diagram for explaining the operation.

FIG. 3 is a circuit diagram specifically showing a main part of FIG.

FIG. 4 is an explanatory diagram of its operation.

FIG. 5 is a similar operation explanatory diagram.

FIG. 6 is a perspective view of a semiconductor device in which a transistor chip is attached to a frame.

FIG. 7 is a schematic diagram for explaining the bonding.

FIG. 8 is a schematic circuit diagram of a conventional junction temperature measuring device for a semiconductor device.

FIG. 9 is a diagram for explaining the conventional operation.

[Explanation of symbols]

 1 chip Q bipolar transistor 3 first constant current source 4 second constant current source 5 switch 6 buffer 7 sampling switch 8 capacitor 11 oscilloscope P pulse

Claims (4)

[Claims] 1. A current supply means for supplying a semiconductor device with a current sufficiently larger than that during a normal operation of the semiconductor device, and a plurality of periodically applied voltages at a PN junction of the semiconductor device during the period of supplying the current. A junction temperature measuring device for a semiconductor device, comprising: a storage circuit for sampling and holding once; and display means for displaying an output of the storage circuit. 2. A first current supply means for applying a predetermined current to the semiconductor device, a second current supply means for applying a current sufficiently larger than the first current supply means to the semiconductor device, and the second current supply means. Pulse generating means for generating a pulse for periodically operating the current supply means, a sample hold circuit for sample-holding the voltage of the PN junction part of the semiconductor device, and a delay after the end of each pulse. A junction temperature measuring device for a semiconductor device, comprising: a sampling pulse generating circuit that outputs a generated sampling pulse. 3. The junction temperature measuring device for a semiconductor device according to claim 2, further comprising means for continuously applying a sampling pulse to a sample hold circuit after the pulse is deenergized. 4. The semiconductor device is a bipolar transistor, and the voltage at the PN junction is a base-emitter voltage, according to any one of claims 1, 2 and 3. Semiconductor device junction temperature measuring device.