JPH05102352A - Cooler for semiconductor power module - Google Patents

Abstract

PURPOSE:To prevent the breakdown of a semiconductor element occurring attendant upon the heat fatigue of soldering by making small the temperature difference arising at on time and off time of the semiconductor element to the vicinity of zero. CONSTITUTION:A heater 24 and a temperature sensing element 25 are fixed closely, in addition to a semiconductor power module 2, onto a cooling fin 1, and the operation, the stoppage, and the changeover of the heater 24 and the operation, the stoppage, and tile changeover of the cooling fin 3 are performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor power module which mainly constitutes a power supply unit which functions by controlling the energization of a semiconductor power module fixed on a metal plate such as copper or iron by soldering a semiconductor element. The present invention relates to a cooling device.

[0002]

2. Description of the Related Art Conventionally, a method shown in FIG. 5 has been generally used as an example of a method for cooling a semiconductor power module in a power supply unit. In FIG. 5, 1 is a cooling fin, and 2 is a semiconductor power module in which a semiconductor element is fixed to a metal base (not shown) such as copper or iron by soldering. It is fixed. Reference numeral 3 denotes a cooling fan, which is arranged above the cooling fin 1 so as to blow air to the cooling fin 1.

Next, the operation will be described. When the power supply unit is operated to control the energization of the semiconductor power module 2 to flow a current, power loss (switching loss and on loss of the semiconductor element) in the semiconductor power module 2 occurs and heat is generated. The generated heat is conducted to the cooling fin 1 via the metal base of the semiconductor power module 2.
On the other hand, the cooling fin 1 is constantly cooled by the air blown by the cooling fan 3, and the temperature of the cooling fin 1 is: It has become almost constant. Next, when the operation of the power supply unit is stopped, the power loss in the semiconductor power module 2 disappears. At this time, since the cooling fins 3 cool the cooling fins 1 by blowing air, the temperature of the cooling fins 1 is cooled toward the temperature of the blowing air. As a result, the semiconductor power module 2 has the cooling fin 1
It will be cooled as the temperature decreases.

As a second conventional example, for example, FIG.
There are those shown in FIGS. 8 and 9. This example is described in JP-A-2-25
It is one disclosed example disclosed in Japanese Patent No. 2260.

In FIG. 7, 31 is an air-cooled pressure contact type semiconductor device, 32 is a temperature detecting means, and the pressure contact type semiconductor device 31 is shown.
The temperature of the internal semiconductor element is detected by the thermocouple 35, converted into an electric signal and output. Reference numeral 33 is control means, which is detection means 3
The electric signal output from the signal line 2 through the signal line 36 is received and discriminated, and the fan 34 is controlled based on the discrimination result.

The operation and operation of the cooling method for the pressure contact type semiconductor device will be described below. As indicated by P in the control pattern diagram shown in FIG. 8, the control means 33 is set to control the air flow rate of the fan 34 so as to be proportional to the semiconductor element temperature. The horizontal axis of FIG. 8 is the element temperature, and the vertical axis is the air flow rate. When the pressure contact type semiconductor device is used, for example, in a semiconductor circuit breaker and the like, the semiconductor device inside the device repeats the power loss pattern as shown in FIG. 9 and the temperature of the semiconductor device rises due to energy accumulation. The horizontal axis of FIG. 9 represents time and the vertical axis represents power loss. The detection means 32 is
This temperature is captured by the thermocouple 35 and converted into an electric signal and output to the control means 33. The control means 33 receives this electric signal and controls the air flow rate of the fan 34 as shown by the curve P in FIG. 8 as described above. As a result, the semiconductor element temperature change is shown by the curve a in FIG. Take the form. The horizontal axis of FIG. 10 represents time, and the vertical axis represents element junction temperature. That is, when the temperature rises due to the power loss from t _{1 to} t ₂ in FIG. 9, cooling is performed in proportion to the temperature, and the higher the semiconductor element temperature is, the stronger the cooling is performed. The temperature is reduced. Also becomes gentle descent of the device temperature since the time of further time t ₂ ~t ₃ of the power loss is not temperature drop decreases the cooling efficiency according to the element temperature decreases. Therefore, the element temperature change ΔT ₁ becomes extremely small. Assuming that the air flow rate of the cooling fan 34 is extremely strengthened and fixed (P (A) in FIG. 8) and extremely weakly fixed (P in FIG. 8).
In (B)), the respective semiconductor element temperature changes become the a curve and the c curve in FIG. In the case of b, the maximum point of the element temperature is reduced because the cooling efficiency is always good, but the temperature drop ΔT ₂ becomes larger than ΔT ₁ because the temperature drop is remarkable when the element temperature falls. Further, in the curve c, since the cooling efficiency is poor, the highest point and the lowest point of the element temperature are higher than those of A and A, and the temperature change ΔT ₃ thereof is larger than ΔT ₁ and ΔT ₂ . In this conventional example, the cooling efficiency of the pressure contact type semiconductor element is changed to reduce the temperature change of the internal semiconductor element at the time of ON and OFF, thereby preventing the destruction due to the current concentration due to the thermal strain of the semiconductor element. To do.

In addition to the above, as a method for extending the life of the combustion control electronic element in Japanese Patent Laid-Open No. 2-195244, only the power source of the heating element of the electronic element to be kept at a predetermined temperature by the heating element is always energized. Discloses a method of relaxing the frequency of thermal shock applied to an electronic element to extend the life of the electronic element.

[0008]

As described above, especially in FIG.
In the cooling device for a semiconductor power module shown in the conventional example, as described above, the semiconductor power module 2 repeatedly generates heat and cools due to the operation and stop of the power supply unit. The temperature of the semiconductor power module 2 is drastically reduced to a great extent, so that the change of the element temperature of the semiconductor power module 2 becomes very large as shown in FIG. In FIG. 6, the horizontal axis represents time and the vertical axis represents temperature, but T ₁ is
The operating period of the power supply unit, T ₂ is the stop period, t ₁ is the semiconductor element maximum temperature rise value during the stop period, and t ₂ is the blowing temperature. When such a change in temperature is applied to the semiconductor power module 2, thermal fatigue occurs in the solder fixing the semiconductor element, which causes solder cracking and eventually chipping, which results in the semiconductor element operating the power supply unit. There is a problem in that the semiconductor element is damaged due to insufficient cooling during the period, which causes an abnormal temperature rise.

A second conventional example (Japanese Patent Laid-Open No. 2522/1990)
No. 60) discloses a method of changing the cooling method depending on the temperature state of the semiconductor element to reduce the temperature change. However, when the semiconductor element is off, the blowing efficiency of the cooling fan is simply reduced. There is a problem that there is a limit in reducing the difference ΔT.

The present invention is intended not for the pressure contact type semiconductor device as in the second conventional example, but for fixing a semiconductor element by soldering. Therefore, in the conventional example of FIG. 5, unless the temperature difference ΔT when the device is turned on and off is made as small as possible (for example, close to zero), damage to the semiconductor device due to thermal fatigue of solder cannot be prevented. The method was not established.

The present invention has been made in order to solve the above problems, and can reduce the temperature difference ΔT generated when the semiconductor element is turned on and off to near zero, and is particularly associated with thermal fatigue caused by soldering. An object of the present invention is to provide a cooling device capable of preventing damage to a semiconductor element that occurs.

[0012]

A cooling device for a semiconductor power module according to the present invention is closely fixed to a metal plate of a power supply unit composed of a semiconductor power module in which a semiconductor element is fixed on a metal plate via solder. A cooling fin, a cooling fan that blows the cooling fin, an electric heating element that is fixed to the cooling fin, and a temperature sensitive element that is closely attached to the cooling fin in the vicinity of the semiconductor power module (second
Temperature sensitive element may be added) and an amplifier operated by the output of this temperature sensitive element (a second amplifier may be added)
And a comparator that uses the output of this amplifier as one input and the set temperature of the temperature setter as the other input, and a cooling fan drive circuit and a heating element drive circuit that operate at the output of this comparator. , The operation of the heating element is stopped so that the temperature change on the cooling fin detected by the temperature sensing element is minimized regardless of the operation of the semiconductor power module.
The switching, the operation of the cooling fan, the stop, and the switching are performed.

[0013]

According to the present invention, the temperature change of the cooling fin tightly fixed to the semiconductor power module can be minimized regardless of whether the semiconductor power module is operated or stopped. Therefore, the semiconductor element is made of copper or iron. Even in a semiconductor power module of a type fixed to a metal base via solder, the thermal fatigue applied to the solder can be reduced. That is, the thermal fatigue applied to the solder portion, which has been the cause of the damage such as the cracking of the solder and the breakage of the solder, which has been conventionally seen, is minimized.

[0014]

Embodiment 1 An embodiment of the present invention will be described below with reference to the drawings. Figure 1
1 shows a power supply unit. In FIG. 1, 1 is a cooling fin, and 2 is a semiconductor power module in which a semiconductor element is soldered and fixed to a metal base (not shown) such as copper or iron. It is fixed on the cooling fin 1 with screws or the like. Reference numeral 3 denotes a cooling fan, which is arranged at a position where air can be blown to the cooling fin 1. Reference numeral 24 is a heating element, which is closely fixed on the cooling fin 1. 25
Is a temperature sensitive element, and again, on the cooling fin 1,
It is tightly fixed near the semiconductor power module 2. Reference numeral 26 is an amplifier, which operates by using the output of the temperature sensitive element 25 as an input. Reference numeral 27 is a comparator, and the output of the amplifier 26 is input to one comparison input section, and the output of the temperature setter 28 is input to the other comparison input section. Reference numeral 29 is a cooling fan drive circuit, which receives the output of the comparator 27 as an input, and the output thereof is input to the cooling fan 3. Reference numeral 30 denotes a heating element drive circuit, which also receives the output of the comparator 27 as an input, and the output thereof is input to the heating element 24.

Next, the operation will be described. When the power supply unit is operated to control the energization of the semiconductor power module 2 to flow a current, power loss (switching loss and on loss of semiconductor elements) in the semiconductor power module 2 occurs and heat is generated. The generated heat is conducted to the cooling fin 1 via the metal base of the semiconductor power module 2. As a result, the temperature of the cooling fin 1 starts to rise. The temperature of the cooling fin 1 is constantly detected by the temperature sensitive element 25 and transmitted to the amplifier 26. The output of the amplifier 26 is further input to one comparison input of the comparator 27, and when it becomes larger than the other comparison input, that is, the output of the temperature setter 28, the output of the comparator 27 changes. This output change signal is transmitted to the cooling fan drive circuit 29, and as a result,
The cooling fan 3 starts driving and starts blowing air toward the cooling fin 1. At the same time, the output change signal is also transmitted to the heating element drive circuit 30 to stop the heating of the heating element 24. Therefore, after the output change, the temperature rise of the cooling fin 1 can be suppressed low. Next, when the operation of the power supply unit is stopped, the power loss in the semiconductor power module 2 disappears. Then, the temperature of the cooling fin 1 does not generate anything, so that it begins to drop rapidly. As described above, the temperature of the cooling fin 1 is always detected by the temperature sensing element 25, and when the temperature falls below the set output equivalent temperature of the temperature setting device 28, the output of the comparator 27 returns to the original value even if it changes again. , Cooling fan drive circuit 29, heating element drive circuit 30
Is transmitted to. As a result, the driving of the cooling fan 3 is stopped, the air supply to the cooling fin 1 is stopped, and at the same time, the operation of the heating element 24 is started. Therefore, after the output of the comparator 27 is changed again (returned to the original), the temperature decrease of the cooling fin 1 is suppressed to be low.

FIG. 2 shows changes in the temperature of the cooling fin 1 over time. In FIG. 2, the horizontal axis represents time and the vertical axis represents temperature. In FIG. 2, T ₁ is an operation period of the power supply unit, a period in which heat is generated in the semiconductor power module 2, and T ₂ is a stop period of the power supply unit. T
₁₁ and T ₂₂ are periods during which the cooling fan 3 is stopped and the heating element 24 is operating, T ₁₂ and T ₂₁ are during driving of the cooling fan 3 and the heating element 24 is stopped, and t ₂ is blast temperature, t
₃ indicates the set temperature of the temperature setter 28.

Embodiment 2 FIG. 3 shows another embodiment. In the figure, reference numeral 32 denotes a second temperature sensitive element, which is arranged so as to detect the blowing temperature of the cooling fan 3. Reference numeral 31 is a second amplifier, which receives the output of the second temperature sensitive element 32 as an input. Reference numeral 28a denotes a temperature setting device, which receives the output of the second amplifier 31 as an input, and the output thereof is input to the comparison input of the comparator 27. Since the other parts are the same as those in the first embodiment, the description thereof will be omitted.

Next, the operation will be described. The second temperature sensitive element 32 always detects the temperature of the air blown to cool the cooling fin 1, and the output of the second temperature sensitive element 32 is the amplifier 31.
Is input to the temperature setter 28a, and the set value of the temperature setter 28a is changed according to the temperature of the blown air. At this time,
Temperature sensitive element 25, amplifier 26, heating element 24, comparator 27,
The operations of the cooling fan drive circuit 29 and the heating element drive circuit 30 are the same as those in the first embodiment already described. FIG. 4 shows that when the blast temperature changes from t _{2 to} t ₃ , the output of the temperature setting device 28a has a constant value t ₄ ,
As in the present embodiment, the temperature change of the cooling fin 1 when changed to t ₅ is shown. The curve a shows the case where the output of the temperature setter 28a is constant, and the curve b shows the case where the temperature setting device 28a is operated in this embodiment. T ₁ is the operation period of the power supply unit, and T ₂ is the stop period of the power supply unit. Also, T ₁₁ , T ₁₁₁ , T
₂₂ and T ₂₂₁ are the periods when the cooling fan 3 is stopped and the heating element 24 is operating, while T ₁₂ , T ₁₂₁ , T ₂₁ , and T ₂₁₁ are driving the cooling fan 3 and the heating element 24 is stopped. It is a period. As can be seen from FIG. 4, although the average temperature of the cooling fins 1 is changed by automatically changing the period during which the cooling fins 1 are forcibly cooled by the blowing air, the average temperature of the cooling fins 1 changes according to the operation and stoppage of the power supply unit. The heat change of repeating
It can be kept small. As a result, the thermal fatigue applied to the solder of the semiconductor power module can be suppressed to a small level.

[0019]

As described above, according to the present invention, in the cooling device for the semiconductor power module, the heat generating element and the temperature sensitive element are closely fixed to the cooling fin, in addition to the semiconductor power module, and the temperature sensitive element is fixed. Since the change in the temperature on the cooling fin detected in step 3 is minimized regardless of whether the semiconductor power module is activated or deactivated, the heating element is switched on and off and the cooling fan is switched on and off. Even when applied to a type semiconductor power module in which a semiconductor element is fixed on a plate with solder, thermal fatigue of the solder can be prevented and a long-life power supply unit can be obtained.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a cooling device for a semiconductor power module applied to a power supply unit according to an embodiment of the present invention.

FIG. 2 is a functional operation explanatory diagram of the embodiment shown in FIG. 1 of the present invention.

FIG. 3 is a cooling device for a semiconductor power module applied to a power supply unit according to another embodiment of the present invention.

FIG. 4 is a functional operation explanatory diagram of the embodiment shown in FIG. 3 of the present invention.

FIG. 5 is a structural diagram showing a conventional cooling device for a semiconductor power module.

6 is a functional operation explanatory view of the conventional example shown in FIG.

FIG. 7 is a structural diagram showing another conventional semiconductor cooling device.

8 is a functional operation explanatory view of the conventional semiconductor cooling device shown in FIG.

9 is a functional operation explanatory view of the conventional semiconductor cooling device shown in FIG.

FIG. 10 is a functional operation explanatory diagram of the conventional semiconductor cooling device shown in FIG. 7;

[Explanation of symbols]

 1 Cooling Fin 2 Semiconductor Power Module 3 Cooling Fan 24 Heating Element 25 Temperature Sensing Element 26 Amplifier 27 Comparator 28 Temperature Setting Device 28a Temperature Setting Device 29 Cooling Fan Driving Circuit 30 Heating Element Driving Circuit 31 Second Amplifier 32 Second Sensing Temperature element

Claims (2)

[Claims] 1. A heat generated by energization of the semiconductor power module, which is closely fixed to the metal plate of a power supply unit that functions to control the energization of a semiconductor power module having a structure in which a semiconductor element is fixed on a metal plate via solder. On the cooling fin, a cooling fan provided so as to conduct heat to the cooling fin, a cooling fan disposed so as to be able to blow air to the cooling fin, an electric heating element closely fixed to the cooling fin, and A temperature-sensitive element closely fixed to the vicinity of the semiconductor power module, an amplifier that operates using the output of this temperature-sensitive element as an input, the output of this amplifier as one input, and the set output for temperature setting is input as the other input. And a cooling fan drive circuit and a heating element drive circuit that receive the output of this comparator as input. When the set constant value is reached, the cooling fan is driven to rotate, and the heat generating action of the heating element is stopped. Conversely, when the cooling fin temperature becomes equal to or lower than the preset fixed value, the cooling fan of the cooling fan is stopped. A cooling device for a semiconductor power module, which has a means for stopping the rotational driving and operating the heating element to generate heat. 2. A second temperature sensitive element provided at an air inlet of a cooling fan of a power supply unit, and a second amplifier having an output of the temperature sensitive element as an input, the output of the second amplifier. The cooling device for a semiconductor power module according to claim 1, wherein the cooling power is input to a temperature setting device, and a set output value of the temperature setting device is controlled by a blowing temperature of the cooling fan.