JPH07263616A - Transistor - Google Patents

Abstract

PURPOSE:To enable the title transistor to be protected from the thermal breakdown without providing a temperature detecting element nor a control circuit. CONSTITUTION:The title transistor chip 2 is mounted on a collector lead 6 of a mount base 3 so as to be electrically connected to each other through the intermediary of a thermistor chip 9 having positive temperature characteristics. On the other hand, a base electrode 4 and an emitter electrode 5 are respectively bonded onto a base lead 7 and an emitter lead 8. At this time, the collector lead 6 of the transistor is kept in the connected state to the collector electrode of the transistor chip 2 through the intermediary of the thermistor 9. When the collector current is increased to raise the temperature of the transistor chip 2 making the temperature of the thermistor 9 exceed a specific value, the resistance value thereof rapidly increases to limit the collector current thereby automatically suppressing the temperature raise in the transistor chip 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transistor mounted on a mount base so as to electrically connect a collector electrode formed on the lower surface of a chip to a mount base, and more particularly to protection from thermal breakdown due to overcurrent or the like. The present invention relates to a transistor.

[0002]

2. Description of the Related Art In a circuit that uses a bipolar power transistor to supply power to a load such as a motor, if an overcurrent flows through the load for some reason, the internal loss of the power transistor increases and the amount of heat radiation is insufficient. Then, the transistor is overheated, and when the current further increases or the current partially concentrates inside the transistor, the transistor may be thermally destroyed. Therefore, conventionally, the internal temperature of the transistor is detected, and when the temperature exceeds the rated temperature, the base current is cut off to turn off the transistor to prevent thermal destruction due to overcurrent.

In this case, in the transistor, when a constant bias voltage VBE is applied between the base and the emitter, the forward rising voltage of the base-emitter junction decreases as the temperature inside the chip increases. The base current increases, and the collector current increases accordingly. Then, the collector loss, which is determined by the collector saturation voltage and the collector current, increases more and more, and the heat generation inside the transistor increases, causing thermal destruction.

Therefore, as a structure for detecting the temperature of the transistor, for example, a structure in which a temperature detecting element such as a thermistor is separately provided from the outside to the transistor for detection, or a temperature detecting element is integrally provided in the chip of the transistor. There are configurations etc. Then, a control circuit is provided to control the base current based on the detected temperature signal from those temperature detecting elements to suppress the collector current and reduce the amount of heat generation, thereby protecting from thermal destruction. There is something.

[0005]

However, in the conventional device as described above, there is a problem that the number of circuit components increases because the temperature detecting element is separately provided, and such a problem is solved. Even if the temperature detection element is provided integrally with the transistor chip, a control circuit for controlling the base current based on the temperature detection signal is required, and the number of circuit components for that purpose increases. there were.

The present invention has been made in view of the above circumstances, and an object thereof is to automatically suppress the flow of an overcurrent as a function of the transistor chip itself without using a separate component or providing a circuit. Another object of the present invention is to provide a transistor capable of preventing the element from being thermally destroyed.

[0007]

The present invention is directed to a transistor mounted so that a collector electrode formed on the lower surface side of a chip is electrically connected to a mount base. It is characterized in that a resistor having a positive resistance characteristic with respect to temperature is interposed between the base and the base.

The resistor may be formed in a plate-shaped chip. Further, the resistor may be integrally formed as a thin film resistor layer on the collector electrode surface or the mount base surface.

[0009]

According to the transistor of the first aspect, since the resistor having the positive resistance characteristic with respect to temperature is interposed between the lower surface side collector electrode of the chip forming the transistor and the mount base, the on operation is performed. Due to this, when the collector current is flowing for some reason while the collector current is flowing, the temperature of the transistor chip rises due to heat generation of the transistor chip due to an increase in collector loss. As a result, when the temperature of the resistor connected in series with the transistor rises, its resistance value increases and the collector current is reduced or cut off. Therefore, since the collector current flowing through the transistor is reduced, heat generation is also suppressed, so that the transistor is automatically protected from thermal breakdown due to temperature rise.

According to the transistor of the second aspect, since the resistor is a plate-shaped chip, it is manufactured by mounting the transistor chip in a state of being mounted and connected to the mount base during assembly. Therefore, the transistor chip and the mount base can be easily formed without any special processing.

According to the transistor of the third aspect, since the resistor is integrally formed as a thin film resistor layer on the collector electrode surface or the surface of the mount base, it is not necessary to use a separate component when assembling. The assembly work can be performed in the same manner as a normal mount.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a PNP type transistor will be described below with reference to FIGS. FIG. 1 shows the appearance of a transistor chip 2 and a mount base 3 that form a power transistor 1. The transistor chip 2 made of silicon is
The collector region is, for example, a P-type silicon substrate on which an N-type base region and a P-type emitter region are formed by impurity diffusion or the like. On the upper surface, a base electrode 4 electrically connected to the base region and An emitter electrode 5 electrically connected to the emitter region is formed. Although not shown, a collector electrode electrically connected to the collector region is formed on the lower surface side of the transistor chip 2.

The mount base 3 made of copper is arranged in a state where the collector lead 6, the base lead 7 and the emitter lead 8 are separated from each other, and the upper surface of the collector lead 6 has a resistor having a positive resistance characteristic with respect to temperature. The plate-shaped thermistor chip 9 is mounted so as to be electrically connected by a conductive bonding material such as solder. In this case, the thermistor chip 9 is a so-called PTC thermistor, and has a positive temperature resistance characteristic in which the resistance value increases as the temperature rises.

On the collector lead 6, the above-mentioned transistor chip 2 is mounted via a thermistor chip 9 in a state of being electrically connected by soldering or the like. The base lead 7 and the base electrode 4 formed on the transistor chip 2 are electrically connected by a bonding wire 10. Further, the emitter lead 8 and the emitter electrode 5 formed on the transistor chip 2 are electrically connected by a bonding wire 11. The transistor 1 is formed in a state in which the package 12 is formed by sealing the portions of the leads 6 to 8 corresponding to the transistor chip 2 with an insulating resin or the like.

FIG. 3 shows an equivalent circuit of the transistor 1. The base electrode 4 of the transistor chip 2 is connected to the base terminal B, the emitter electrode 5 is connected to the emitter terminal E, and the collector electrode is a thermistor chip 9 in series. It is in a state of being connected to the collector terminal C via.

Next, the operation of this embodiment will be described with reference to FIGS. 4 and 5. The resistance value Rs of the thermistor chip 9 changes with a positive temperature characteristic as the temperature changes, as shown by the solid line in FIG. 4, for example. That is, when the temperature of the thermistor chip 9 is lower than 150 ° C., the resistance value is extremely low (1 Ω or less), which is substantially equivalent to the fact that there is almost no resistance. When it exceeds, the resistance value Rs rapidly increases and k
It will change up to Ω order.

As a result, in the equivalent circuit of FIG. 3, when the collector current IC of the transistor 1 increases and the amount of heat generated by the collector loss increases, the resistance of the thermistor chip 9 increases from around the temperature of the transistor chip 2 exceeding 150 ° C. The value Rs rapidly increases. As a result, the collector current IC flowing through the transistor chip 2 is largely limited by the state thermistor chip 9 interposed in series, and as shown by the broken line in FIG. From then on, it decreases sharply until it is almost shut off.

When the collector current IC is drastically reduced in this way, the collector loss in the transistor chip 2 is also reduced and the amount of heat generated is reduced, so that the temperature rise of the transistor chip 2 is suppressed and thermal destruction occurs. It will automatically prevent you from doing so.

Therefore, for example, when a circuit for driving the transistor 1 by connecting it in series with a load such as a motor and turning it on and off is constructed, as shown in FIG. When an excessive collector current IC flows due to a cause and the transistor chip 2 generates heat, the resistance value Rs is increased by the temperature rise of the thermistor chip 9 and the collector current IC automatically increases.
Will be suppressed.

According to the present embodiment, since the thermistor chip 9 having a positive temperature characteristic is interposed between the collector electrode of the transistor chip 2 and the collector lead 6, the current flowing in the transistor 1 is When the temperature of the transistor chip 2 rises due to the increase, the resistance value of the thermistor chip 9 increases due to the heat to suppress the collector current IC, so that the temperature of the transistor chip 2 can be lowered. As a result, it is possible to realize a configuration that prevents a problem such as thermal destruction due to heat generation due to an excessive collector current IC, as a simple and inexpensive configuration without separately providing a temperature sensor or a control circuit.

According to this embodiment, the transistor chip 2 is not specially processed, or the collector lead 6 of the mount base 3 is not specially processed.
It can be manufactured simply by adding a simple process.

FIG. 6 shows a second embodiment of the present invention. The difference from the first embodiment is that a thermistor thin film layer 13 as a thin film resistor is provided in place of the thermistor chip 9. That is, the thermistor thin film layer 13
Is formed on the surface of the collector lead 6 by a method such as vapor deposition and has the same electrical characteristics as the thermistor chip 9 in the first embodiment.

Therefore, even with this configuration, the same effect as that of the first embodiment can be obtained, and the thermistor thin film layer 13 is formed in advance on the collector lead 6 of the mount base 3, so that the transistor chip 2 can be obtained. Since it can be carried out by carrying out the same steps as in the conventional case at the time of assembling the collector lead 6 on the collector lead 6, it becomes possible to easily manufacture.

The present invention is not limited to the above embodiment, but can be modified or expanded as follows. The thermistor thin film layer 13 can also be directly formed on the collector electrode on the lower surface side of the transistor chip 2. It can also be applied to NPN transistors. The package is not limited to the resin-sealed package. Further, it can be applied to transistors other than bipolar transistors.

[0025]

As is apparent from the above description, according to the transistor of the present invention, the following effects can be obtained.
That is, according to the transistor of claim 1, since the resistor having the positive resistance characteristic with respect to temperature is interposed between the transistor chip and the mount base,
When the collector current increases during the ON operation and the temperature of the transistor chip rises, the temperature of the resistor connected in series rises and its resistance value increases.
It is possible to reduce or cut off the collector current and suppress the collector current flowing through the transistor to lower the temperature of the transistor chip, which allows the transistor to flow without separately providing a temperature detecting element or a control circuit. This has an excellent effect that the collector current can be automatically reduced to prevent the occurrence of thermal destruction.

According to the transistor of claim 2, since the resistor is a plate-shaped chip, it is manufactured by mounting the transistor chip in a state of being mounted and connected to the mount base during assembly. Therefore, there is an excellent effect that the transistor chip and the mount base can be easily formed without special processing.

According to the transistor of the third aspect, the resistor is integrally formed on the collector electrode surface or the surface of the mount base as a thin film resistor layer, so that it is not necessary to use a separate component when assembling. The excellent effect that the assembling work can be performed in the same manner as a normal mount is achieved.

[Brief description of drawings]

FIG. 1 is an external perspective view of an essential part showing a first embodiment of the present invention.

FIG. 2 is a vertical sectional side view of a transistor chip portion.

FIG. 3 Equivalent circuit of transistor

FIG. 4 is a characteristic diagram of resistance value and collector current with respect to temperature.

FIG. 5 is an operation explanatory view showing a change with time of collector current.

FIG. 6 is a view corresponding to FIG. 2 showing a second embodiment of the present invention.

[Explanation of symbols]

1 is a transistor, 2 is a transistor chip, 3 is a mount base, 4 is a base electrode, 5 is an emitter electrode, 6 is a collector lead, 7 is a base lead, 8 is an emitter lead, 9 is a thermistor chip (resistor), 10, Reference numeral 11 is a bonding wire, 12 is a package, and 13 is a thermistor thin film layer (thin film resistor layer).

Claims (3)

[Claims] 1. A transistor in which a collector electrode formed on the lower surface side of a chip is mounted so as to be electrically connected to a mount base, and a positive resistance characteristic with respect to temperature is provided between the chip and the mount base. A transistor characterized in that a resistor is interposed. 2. The transistor according to claim 1, wherein the resistor is formed on a plate-shaped chip. 3. The transistor according to claim 1, wherein the resistor is a thin film resistor layer integrally formed on the collector electrode surface or the mount base surface.