JPH09129794A - Semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable reduction in unevenness of element temperature by alternately arraying codling fins and semiconductor elements with the cooling fins located at the ends and raising the cooling efficiency of the cooling fins other than the cooling fins at both ends so as to be higher than the cooling efficiency of the cooling fins at both ends. SOLUTION: Seven cooling fins 1021-1027 and six flat thyristor elements 1011-1016 are alternately provided in parallel with the cooling fins 1021-1027 located at the ends. Cooling media for the cooling fins 1021-1027 are introduced in parallel through insulating pipes 1041-1047. On the insulating pipes 1041 and 1047 at both ends, flow rate regulating valves 1051 and 1052 are provided so that the cooling efficiency of the cooling fins 1022-1026 other than the cooling fins 1021 and 1027 at both ends is raised to be higher than the cooling efficiency of the cooling fins 1021 and 1027. Thus, unevenness of temperature of the thyristor elements 1011-1016 may be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a large capacity semiconductor device.

[0002]

2. Description of the Related Art A semiconductor rectifying device having a high withstand voltage and a large current capacity rectifying function is used in a device handling a large amount of electric power such as an inverter for a rolling mill. High-voltage semiconductor rectifiers include elements such as diodes, thyristors, GTOs (gate turn-off thyristors), triacs, reverse conducting thyristors and insulated gate thyristors. As these large-capacity semiconductor rectifiers, there are used flat semiconductor rectifiers having two main electrodes and being pressed by both main electrode surfaces to make electrical contact.

Further, in a large capacity device, a plurality of semiconductor rectifying elements are used in parallel, in series, or connected in a bridge type. When the temperature of the semiconductor rectifying element becomes higher than the rated value, the voltage blocking capability is lowered, loss is increased, etc., and it becomes difficult to obtain normal device operation. For this reason, a large-capacity flat semiconductor rectifying element is used by pressing the cooling fins on both sides under pressure.

Examples of such conventional techniques include, for example, JP-A-57-183060, JP-A-58-131754, and JP-A-58-131754.
Some are described in Japanese Patent No. 59-9949.

[0005]

There is a blocking state recovery charge defined by the time integral value of the flowing current when the semiconductor rectifying device changes from the forward conduction state to the blocking state. Hereinafter, this is called Qrr. When many large-capacity semiconductor rectifiers are connected, the voltage sharing is determined by the value of Qrr. That is, the blocking voltage applied to the element having a large Qrr is small, and conversely, the blocking voltage applied to the element having a small Qrr is large. Therefore, if the variation of Qrr becomes large, the element may be damaged. Therefore, when a plurality of elements are connected in series or in parallel, a semiconductor rectifying element having more uniform element characteristics is generally selected and used. However, even if elements with the same characteristics are used,
If there is variation in the cooling performance, the temperature of the semiconductor layer will be different, and the characteristics of the element itself will fluctuate.

The above-mentioned prior art is intended to reduce variations in cooling efficiency of semiconductor elements. Since the medium used for cooling is introduced into the cooling fins in the series, the temperature of the medium heats up as the distance from the fan rises and becomes high.
It causes variations in element temperature. These conventional techniques are techniques for reducing the temperature gradient due to the distance from the cooling fan. When the refrigerants are introduced in parallel, the refrigerants have the same temperature. Therefore, the temperature variation of the cooling medium that occurs when the cooling medium is introduced into the cooling fins is made uniform.

However, when three or more flat semiconductor devices are brought into pressure contact with each of them being sandwiched by cooling fins, the same cooling medium, the same amount and the same structure of the cooling fins are used. However, even though the semiconductor rectifying element is applied with almost the same load to generate heat, the voltage sharing of the semiconductor elements at both ends becomes large.

[0008]

In the present invention, three or more flat semiconductor elements having a rectifying function are cooled from both sides by cooling fins, and the number of cooling fins is one more than the number of semiconductor elements. In the semiconductor device in which the cooling fins and the semiconductor rectifying elements are alternately arranged with the cooling fins as the outermost ends, the cooling medium is introduced in parallel to the cooling fins, and the pressurizing contact is made from the outside of the cooling fins, The cooling efficiency of the other cooling fins is higher than that of the other cooling fins.

The above means has the following actions.

First, the problems described in the problems to be solved by the present invention occur due to the following reasons.

Generally, a flat semiconductor element is cooled from both sides by cooling fins, the number of cooling fins is one more than the number of semiconductor elements, and the cooling fins and the semiconductor elements are alternately arranged with the cooling fins being the end portions. . As already mentioned,
A cooling medium is introduced into the cooling fins in order to make the element temperature uniform. Therefore, when three or more semiconductor elements are brought into pressure contact with each other, the cooling fins at the outermost ends cool only the adjacent semiconductor elements at the outermost ends.

On the other hand, since the cooling fins other than the outermost portion have the semiconductor elements on both sides thereof, the two semiconductor elements on both sides thereof are cooled.

The cooling medium flowing in the cooling fins is heated and heated when passing through the fins. Therefore, the temperature rises in the other fins are higher than the temperature rise of the cooling medium in the cooling fins at the extreme end. For this reason, the cooling efficiency of the fins at the outermost end is higher than the cooling efficiency of the other fins. Therefore, the temperatures of the semiconductor elements at both end portions adjacent to the cooling fin at the end portion having high cooling efficiency are lower than the temperatures of the other semiconductor elements. As a result, when the temperature variation of the semiconductor element becomes larger than the allowable value, only the outermost semiconductor element has a lower Qrr than the other semiconductor elements due to the temperature dependency of Qrr, and the imbalance in the reverse voltage applied is applied. Occurs.

Therefore, in such a semiconductor device, the cooling efficiency of the cooling fins other than the cooling fins is increased as compared with the cooling efficiency of the cooling fins at the extreme ends, so that the heat flow rate to the fins at the extreme ends is increased. , And the heat flow rate flowing from one surface of the other fin. As a result, it becomes possible to make the temperatures of the semiconductor elements at both ends the same regardless of the inside or inside. Further, by making the temperatures of the semiconductor elements equal, it is possible to eliminate the variation of Qrr and further reduce the variation of the reverse voltage applied.

The present invention will be described more specifically.

By cooling the cooling fins at both ends of the semiconductor device with air and cooling the other cooling fins by circulating water or oil, it is possible to reduce variations in element temperature. This is because the water-cooled or oil-cooled fins have higher heat exchange efficiency than the air-cooled cooling fins, and therefore the heat dissipation efficiency of the inner cooling fins is higher than that of the outermost cooling fins. .

Further, since the number of water-cooled or oil-cooled fins is reduced by two per module as compared with the conventional method, even if the total flow rate of the circulating cooling medium is the same,
Since the flow rate per fin increases, the element temperature can be reduced.

Further, by lowering the flow rate of the cooling medium in the both endmost cooling fins than the flow rate of the cooling medium in the other cooling fins, the internal cooling fins radiate heat more than the endmost cooling fins. It is possible to improve efficiency and reduce variations in element temperature. Further, as for the number of fins, in the internal fins, the flow rate per fin increases in the internal fins, so that the element temperature can be reduced, the loss can be reduced, and the reliability can be improved.

Further, by providing a means for lowering the conductance of the circulation path of the cooling fin at the endmost than the conductance of the cooling fins other than that, the water amount of the fin at the endmost can be freely adjusted and the same effect can be obtained. be able to.

Further, even when the cooling medium of the same flow rate flows in any of the fins, the cooling efficiency of the fins has a distribution by setting the temperature of the cooling medium at the inlet of the fins high only for the fins at the extreme ends. The element temperature can be kept constant.

In addition, a conductor is provided between the semiconductor element at the end and the cooling fin at the end, and pressure is applied by the conductor so that the amount of heat flowing from the element at the end to the fin at the end. Can be adjusted, and the element temperature can be kept constant.

Further, the thermal resistance of the cooling fins at the end is made higher than the thermal resistance of the other cooling fins, and the amount of heat flowing from the element at the end to the fin at the end is adjusted to keep the element temperature constant. Can be

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a semiconductor device in which a plurality of thyristors, which is a first embodiment of the present invention, are connected in series.
(Hereinafter, referred to as a thyristor module) and the flow rate of the cooling medium flowing through each cooling fin are shown. This module consists of 6 flat thyristors (1011, 1012, 1013, 101
4,1015,1016) and seven cooling fins (102
1,1022,1023,1024,1025,102
6, 1027) and a pressurizer (1030).

Pure water is used as a cooling medium flowing through each cooling fin. Pure water is applied to each fin with an insulating pipe made of Teflon (1041, 1042, 1043, 1044, 10).
45, 1046, 1047) and introduced in parallel. The flow rate of pure water is adjusted by the flow rate adjusting valves (1051, 1052) in the Teflon pipes introduced into the cooling fins at the extreme ends of both. As shown in the graph at the top of Figure 1, fin 1 has 7.5 liters / minute, fin 2 has
Therefore, the cooling water is introduced into the fins 6 at a flow rate of about 12.5 liters / minute and the fins 7 at a flow rate of 9 liters / minute to cool each thyristor.

FIG. 2 shows the thyristor module according to the prior art, the element temperature of each thyristor and the reverse voltage applied after turn-off. Also in this module, as in FIG. 1, six flat thyristors (3011, 3012, 301)
3, 3014, 3015, 3016) and seven cooling fins (3021, 3022, 3023, 3024, 302)
5, 3026, 3027) and a pressurizer (3030). Cooling water with a flow rate of 7.1 liters / minute circulates in all the fins, and the water temperature at the fin inlet is almost the same. The total amount of water in the seven fins is the same as that of the embodiment of the present invention shown in FIG.

The element temperature when the module of FIG. 2 is continuously operating is 37 degrees in the element 1 and 6 in the elements 2 to 5.
5 degrees and 51 degrees for element 6. Further, the reverse voltage applied after the turn-off is 1 kV in the elements 2 to 5, whereas 2 kV, which is twice that in the elements 1 and 6, is applied.

On the other hand, the element temperature and the reverse voltage in the case of the embodiment of the present invention described in FIG. 1 are shown in FIG. Element temperature is 50 degrees, reverse voltage is all 1.3 k
V is constant. Moreover, since the reverse voltage is made uniform, the total loss is about 5% compared to the module of FIG.
The degree is decreasing. Further, FIG. 3 shows an example of the device current and the device voltage at the time of turn-off. The element 1 at the end has the same characteristics as the element 2 inside thereof.

On the other hand, FIG. 4 shows a current-voltage waveform example in the conventional module when the current decreases at the same timing as in FIG. This figure shows the waveforms of the element 1 to which the maximum voltage is applied and the element 2 to which the minimum voltage is applied, which are shown in FIG.

In the device 2, the period from the application of the reverse voltage to the application of the forward voltage is shorter than that of the device 1, and the forward voltage is applied within the time shorter than the turn-off time of the device 2. , A false ignition occurs after the forward voltage is applied, and it turns on. In order to prevent such a malfunction, in the conventional technique, it is necessary to control from an external circuit so that the turn-off period is longer than the turn-off time of each element. On the other hand, according to the present embodiment, the control range can be expanded to the off period which is equivalent to the turn off period of the device.

Although the loss of the semiconductor element is almost the same during the steady operation, the loss fluctuates due to the fluctuation of the power transmission amount due to the fluctuation of the load and the amount of water shown in FIG. The amount of water may deviate. In such a case, the amount of water may be controlled as follows.

FIG. 7 shows a schematic diagram of the water amount calculation unit. Current (I1 to I6) voltage (V1 to V6) of each semiconductor element
Is monitored at any time, arithmetic processing is performed based on a given constant, and the element temperature can be controlled to a preset temperature by adjusting the amount of water based on the arithmetic result.

FIG. 8 shows a model of a module used in the arithmetic unit. The parameters given in advance include the thermal resistance from the semiconductor substrate of the thyristor to the anode pressing electrode surface (RthA), the thermal resistance to the cathode pressing electrode surface (RthK), and the cooling fin surface to the cooling water. Thermal resistance (RThf) and the contact thermal resistance (Rthc) between the semiconductor element and the cooling fin. From this, the loss of each semiconductor element is obtained based on actual measurement. Based on these values, the thermal resistance (RthW1 to Rth) of the circulating water such that the temperature (Tj1 to Tj6) of each semiconductor element becomes a predetermined value.
W7) is calculated. Further, the amount of circulating water that gives these values is calculated. As a result, the element temperature can be controlled at high speed even if the loss varies due to the variation of the load.

(Second Embodiment) FIG. 5 shows a second embodiment of the present invention.

This module, like the first embodiment, includes six flat thyristors (1011, 1012, 1013, 101).
4,1015,1016). In addition, five cooling fins (5011, 5012, 50) that circulate cooling oil
13, 5014, 5015). Furthermore, the air-cooling cooling fins (5021, 5
022). These thyristors and cooling fins are pressed against each other by a pressurizer (1030).

Since the water-cooled or oil-cooled fins have higher heat exchange efficiency than the air-cooled cooling fins, the heat dissipation efficiency of the inner cooling fins is higher than that of the cooling fins at the end, and the heat dissipation efficiency is improved. Similar to the above, it becomes possible to make the element temperature uniform. In addition, the number of fins is reduced by 2 per module as compared with the conventional method, so that the flow rate of the total circulating cooling medium is the same, but the element temperature is reduced because the flow rate per fin is increased. You can

(Embodiment 3) FIG. 6 shows a third embodiment of the present invention.

Also in this module, as in the first embodiment, six flat thyristors and seven cooling fins for circulating cooling water are press-contacted by a pressurizer. The difference from FIG. 1 is that the thermal resistance compensation conductors (801, 802) are sandwiched between the thyristors at both ends and the cooling fins. A metal such as molybdenum, tungsten, or copper is used for the thermal resistance compensation conductor. Moreover, a plating process is performed as needed. In this embodiment, oxygen-free copper having a diameter of 155 mm is used. The surface is plated with nickel of several microns. Also, in order to prevent the occurrence of a thermal resistance that greatly differs from the design value on the contact surface with the cooling fin or the thyristor, surface wrapping is applied to make the contact surface flatness within 10 microns, parallelism within 10 microns, and Surface roughness should be within 0.5 micron. The thermal resistance compensating conductors 801 and 802 can have different thicknesses if necessary.

Pure water having the same water temperature and amount is circulated in all the cooling fins. In order to limit the amount of heat that the thermal resistance compensation conductor flows from the element at the end to the cooling fin,
All thyristors have the same element temperature.

[0040]

According to the present invention, it is possible to make uniform the element temperature of a plurality of flat type semiconductor elements that are pressed against each other and prevent variations in characteristics.

[Brief description of the drawings]

FIG. 1 is a flow chart of a cooling medium flowing through a thyristor module and each cooling fin according to a first embodiment of the present invention.

FIG. 2 shows the temperature of a thyristor module according to the prior art and the temperature of each thyristor and the reverse voltage applied after turn-off.

FIG. 3 is an element temperature of each thyristor in the thyristor module of the first embodiment, a reverse voltage, and a current and a voltage when the thyristor is turned off.

FIG. 4 shows current and voltage waveforms when a malfunction occurs in the conventional thyristor module.

FIG. 5 is a thyristor module that is a second embodiment of the present invention.

FIG. 6 is a thyristor module that is a third embodiment of the present invention.

FIG. 7 is a schematic diagram of a water amount calculation unit of a cooling fin.

FIG. 8 is a model used in the arithmetic unit shown in FIG.

[Explanation of symbols]

1011 to 1016, 3011 to 3016 ... Flat thyristor, 1021 to 1027, 3021 to 3027 ... Cooling fin, 1041 to 1047 ... Insulation pipe, 1051, 1052
… Valve for adjusting flow rate.

Claims (5)

[Claims] 1. Three or more flat semiconductor elements are cooled from both sides by cooling fins, the number of cooling fins is one more than the number of flat semiconductor elements, and the cooling fins and the flat semiconductor elements have cooling fins. In a semiconductor device in which the cooling mediums are alternately arranged as the outermost ends, the cooling medium is introduced in parallel to the cooling fins, and they are brought into pressure contact with each other from the outside of the cooling fins, compared with the cooling efficiency of the cooling fins at the outermost ends. A semiconductor device having high cooling efficiency for cooling fins other than the above. 2. The semiconductor rectifier according to claim 1, wherein
A semiconductor device characterized in that the cooling fins at both ends are air-cooled, and the other cooling fins are cooled by circulating water or oil. 3. The semiconductor rectifying device according to claim 1, wherein
Each of the cooling fins circulates a cooling medium to cool it,
A semiconductor device characterized in that the flow rate of the cooling medium in both the endmost cooling fins is smaller than the flow rate of the cooling medium in the other cooling fins. 4. The semiconductor rectifier according to claim 3,
A semiconductor device characterized in that the conductance of the circulation path of the cooling fin at the extreme end is lower than the conductance of the other cooling fins. 5. The semiconductor device according to claim 1, wherein the thermal resistance of the cooling fin at the end is larger than the thermal resistance of the other cooling fins.