Thermal shock test apparatus and thermal shock test method

Abstract

A thermal shock testing device (10) comprises: a sample chamber (4) in which a sample (11) to be evaluated is placed and sealed; a chiller (2) that cools the sample chamber (4) to a prescribed temperature by using a coolant (5); a lamp heater (6) that heats the sample (11) to be evaluated to a target temperature; a temperature sensor (7) that detects the temperature of the sample (11) to be evaluated; and a control device (1) that controls operation of the chiller (2) and the energization / shut-off of the lamp heater (6). After the sample chamber (4) is cooled to the prescribed temperature, the sample (11) to be evaluated is heated to the target temperature by using the lamp heater (6), then energization of the lamp heater (6) is shut off, and a thermal shock is applied to the sample (11) to be evaluated, thereby making it possible to perform a thermal shock test in a short time.

Description

Technical Field

[0001] This application relates to a thermal shock test apparatus and a thermal shock test method.

Background Art

[0002] In recent years, from the perspective of energy conservation, development has been actively carried out to apply semiconductor devices based on silicon carbide (SiC) or gallium nitride (GaN) as next-generation devices to power modules. The operating temperature of semiconductor devices used in power modules is set to 175°C or higher from the perspective of reducing power loss, and it is considered that the temperature will reach 300°C in the future, and high reliability is required. In addition, when trying to achieve both high operating temperature and high reliability, long life is required, and accordingly, there is a problem that the evaluation period also extends.

[0003] Furthermore, these days, the usage applications of semiconductor devices have become diverse. For example, after a thermal shock test, a low-temperature holding test is performed, and then a power cycle test in which the semiconductor device is operated and energized for heating is added, which is a user-specific test method called a composite cycle test, and the test conditions cover a wide range. Thus, when new test methods are required, the reliability evaluation period becomes even longer, and there is a problem that the development period of new power modules becomes longer.

[0004] On the other hand, in the environmental test apparatus of Patent Document 1, a rotating heat-insulating wall is provided to divide the test tank for storing the test specimen into a low-temperature and humidity-controlled section and a high-temperature and humidity-controlled section, each equipped with a low-temperature conditioner and a high-temperature conditioner, which are heat source devices. An environmental test apparatus is disclosed that includes a fulcrum and an electric motor that can rotate the rotating heat-insulating wall by at least 180° with the center of the test tank as the fulcrum. Further, since the test specimen can be mounted on the rotating heat-insulating wall, space is secured in the test tank, and a local heating device such as a far-infrared lamp or a local cooling device such as a spot-type air cooler is provided in an appropriate space area in the test tank. It is possible to perform local heating or cooling while conducting a temperature and humidity test on the test specimen.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in the environmental test apparatus of the above Patent Document 1, the temperature in the environmental test tank is adjusted by providing a local heating device such as a far-infrared lamp or a local cooling device such as a spot-type air cooler. However, since the inside of the tank is not kept at a low temperature or a high temperature in advance, there is a problem that it is difficult to perform heating or cooling in a short time.

[0007] The present application has been made to solve the above problems, and an object thereof is to provide a thermal shock test apparatus capable of performing a thermal shock test on an evaluation sample in a short time and at high speed.

Means for Solving the Problems

[0008] The thermal shock test device disclosed in the present application includes a sample chamber where the sample to be evaluated is placed and sealed, a chiller that circulates a refrigerant in the sample chamber to cool the sample chamber, a heater installed in the sample chamber to heat the sample to be evaluated, a temperature sensor that detects the temperature of the sample to be evaluated, and a control device that controls the operation of the chiller and the energization and interruption of power supply to the heater based on the temperature. After the sample chamber is cooled to a predetermined temperature by the chiller, the heater is energized, and after the sample to be evaluated is heated to the target temperature, the power supply to the heater is interrupted, and the sample to be evaluated is cooled.

[0009] In addition, the thermal shock test method disclosed in the present application includes a step of placing and sealing the sample to be evaluated in the sample chamber, a step of circulating the refrigerant of the chiller in the sample chamber to cool the sample chamber to a predetermined temperature, a step of energizing the heater installed in the sample chamber to heat the sample to be evaluated to the target temperature, and a step of interrupting the power supply to the heater to cool the sample to be evaluated.

Advantages of the Invention

[0010] According to the thermal shock test device of the present application, in a state where the sample chamber is cooled to a predetermined temperature by the chiller, the sample to be evaluated can be heated by using a heater that can locally and rapidly increase the temperature from a low-temperature environment, thereby applying a thermal shock to the sample to be evaluated. It is possible to perform a highly reliable thermal shock evaluation test in a short time and at high speed, and there is an effect that the evaluation time can be shortened.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0012] Embodiment 1. FIG. 1 is a schematic configuration diagram showing the overall structure of the thermal shock test apparatus according to Embodiment 1. FIG. 2 is a diagram showing an example of the temperature distribution on the tube surface of the lamp heater used in the thermal shock test apparatus according to Embodiment 1.

[0013] First, the overall configuration of the thermal shock test apparatus 10 according to Embodiment 1 will be described with reference to FIG. 1. The thermal shock test apparatus 10 includes a sample chamber 4 in which an evaluation sample 11 is placed and sealed, a chiller 2 through which a refrigerant 5 circulates through a refrigerant pipe 3 to cool the inside of the sample chamber 4 to a predetermined temperature, a lamp heater 6 installed facing the evaluation sample 11 in the sample chamber 4 to heat the evaluation sample 11, a temperature sensor 7 for detecting the temperature of the evaluation sample 11, and a control device 1 for controlling the operation of the chiller 2 and the energization and interruption of the lamp heater 6 according to the temperature of the evaluation sample 11.

[0014] The thermal shock test is one of the environmental tests for confirming how resistant an electronic component or device is to changes in the ambient temperature. By repeatedly applying a temperature difference between high and low temperatures, the resistance to temperature changes is evaluated in a short time. Since power semiconductor devices are required to have high-temperature stress resistance against high currents, tests in the range where the target high-temperature side temperature is from 250°C to 300°C and the low-temperature side temperature to be maintained is from -70°C to 0°C are required. In practice, the target high-temperature temperature and the predetermined temperature to be maintained at low temperature are determined according to the requirements of the evaluation test of the evaluation sample.

[0015] In the thermal shock test, rapid switching from low temperature to high temperature and from high temperature to low temperature is required. In the present application, the switching of the exposure test of the evaluation sample 11 between high temperature and low temperature is performed rapidly by a combination of the chiller 2 that cools the sample chamber 4 and the lamp heater 6 that heats the evaluation sample 11.

[0016] As an example of the evaluation sample 11, in this embodiment, as shown in FIG. 1, a semiconductor module in which a semiconductor element 13 is mounted on a lead frame 15 via a bonding material 14 is cited. Here, further, the portion where the semiconductor element 13 is mounted is sealed with a mold resin 12. This evaluation sample 11 may be formed of any constituent material, and there are no particular restrictions on the constituent material. However, generally, aluminum or a shiny material is difficult to absorb the heat of the lamp heater 6 and requires time for heating. However, since other parts are heated and the whole is heated as a result, it is possible to heat without problems. For example, by applying a carbon spray to the surface of shiny aluminum, heat can be absorbed and heating becomes possible. The surface of the evaluation sample 11 may be arbitrarily modified.

[0017] The sample chamber 4 holds the evaluation sample 11 placed therein in a sealed state and cooled to a predetermined temperature (here, a low temperature of less than 0°C to about -10°C) by a refrigerant 5 circulated through a refrigerant pipe 3 by a chiller 2. Generally, when taking the evaluation sample 11 in and out of the sample chamber 4, the inside of the sample chamber 4 is evacuated by a pump (not shown) or returned to the atmosphere. As the refrigerant (circulating liquid) 5, a fluorine-based, alcohol-based refrigerant, or a mixture thereof can be selected and used according to the target cooling temperature. The material of the refrigerant 5 may be determined in consideration of the inner wall of the sample chamber 4 and the material used for the evaluation sample 11 so as not to cause problems of corrosion and icing.

[0018] For example, an anti-icing coating agent may be applied to the inner wall surface of the sample chamber 4. Alternatively, a water-repellent coating that prevents moisture from adhering or a surface modification having a surface structure that enables water repellency may be performed. Further, by covering the periphery outside the sample chamber 4 with a heat insulating member such as glass wool, it is possible to efficiently cool the inside of the sample chamber 4 and maintain it at a constant temperature. Also, the sample chamber 4 may have a vacuum heat insulation structure.

[0019] As a heater for heating the sample to be evaluated 11, the lamp heater 6 is installed at a position facing the sample to be evaluated 11 in the sample chamber 4 on which the sample to be evaluated 11 is placed. Here, as the lamp heater 6, the case where a halogen lamp is used as the heater is called a lamp heater. The halogen lamp, for example, energizes a filament mainly composed of tungsten to make it hot, and utilizes the light radiated therefrom (the wavelength is an electromagnetic wave in the near-infrared region to the visible region). The efficiency of converting to visible light is very low, at 10% or less, but the efficiency of converting to all electromagnetic waves including infrared light is around 90%, making it a very efficient heating means. The temperature of the filament is approximately 2500°C to 3000°C, and when condensed, non-contact and clean heating can be achieved at 1300°C to 1500°C.

[0020] However, when using concentrated light, only a part of the sample to be evaluated 11 can be heated. Therefore, in the present application, a lamp heater called a parallel light type that can perform isothermal heating within a certain range is used. For example, in an actual thermal shock test of a semiconductor device, a test at several thousand degrees Celsius is not performed (the mold resin melts or the bonding material melts and breaks). Therefore, since there is no need to condense the light, a parallel light type lamp heater is adopted.

[0021] Fig. 2 shows an example of the temperature distribution on the tube surface of the lamp heater 6. Here, 95% of the peak temperature is defined as the isothermal length A. The dimension B of the sample to be evaluated 11 is preferably within 80% of the isothermal length A of the peak temperature on the tube surface in the longitudinal direction of the lamp heater 6. Thereby, it becomes possible to apply a uniform thermal load to the sample to be evaluated 11.

[0022] The temperature sensor 7 detects the temperature of the sample under evaluation 11. In FIG. 1, a thermocouple is attached to the lead frame 15 on which the semiconductor element 13 is mounted, detects the temperature of the sample under evaluation 11, and sends a signal to the control device 1 described later. Here, the case of using a thermocouple is described as the temperature sensor 7. As the temperature sensor 7, a window may be provided in the wall of the sample chamber 4 to optically detect the temperature of the sample under evaluation 11 in a non-contact manner.

[0023] The control device 1 determines that the temperature of the sample under evaluation 11 detected by the operation of the chiller 2 that cools the sample chamber 4 and the temperature sensor 7 has reached a predetermined low temperature and a target high temperature, and controls the energization and interruption of the lamp heater 6. A thermocouple is attached to the sample under evaluation 11 as the temperature sensor 7, and the thermocouple is connected to the control device 1. Based on the temperature detected by the thermocouple, the control device 1 performs the operation of the chiller 2, the energization and interruption of the lamp heater 6. Also, by adjusting the output of the lamp heater 6, it is possible to control the heating rate.

[0024] The problem of ice formation on the surface of the lamp heater 6 can be further addressed, for example, by always operating the lamp heater 6 at a low output to prevent ice from adhering to the surface of the lamp heater 6 due to the cooling of the sample chamber 4, so that the radiant light of the lamp heater 6 is not properly absorbed by the sample under evaluation 11. Alternatively, it is possible to apply a water-repellent coating agent or the like to the surface of the lamp heater 6 that can suppress ice formation. The above applies when the refrigerant 5 contains moisture. For example, in the case of a fluorine-based refrigerant, it is possible to suppress ice formation by making at least the sample chamber 4 a sealed space to prevent the intrusion of moisture. Also, alcohol-based refrigerants such as ethanol may be used according to the corresponding temperature. Further, a plurality of refrigerants may be mixed. The chiller 2 may be selected according to the temperature to be cooled. Also, regarding the cooling means, since the sample chamber may be at a low temperature (negative temperature), even if the refrigerant is not directly flowed, it is possible to keep the sample chamber at a low temperature by having a flow path in any of the upper surface, wall surface, and bottom surface constituting the sample chamber and having the refrigerant flow in the flow path.

[0025] When performing a thermal shock test, first, place the sample under evaluation 11 in the sample chamber 4 and attach the temperature sensor 7 to the sample under evaluation 11 (in FIG. 1, it is attached to the lead frame 15). Then, after sealing the sample chamber 4, evacuate it with a pump and circulate the refrigerant 5 of the chiller 2 in the sample chamber 4 for cooling. After the control device 1 confirms that the temperature of the sample under evaluation 11 has been cooled to a predetermined low temperature by the temperature sensor 7, start energizing the lamp heater 6 and heat the sample under evaluation 11 to the target temperature. After confirming that the temperature of the sample under evaluation 11 has reached the target high temperature, cut off the power supply to the lamp heater 6. Then, the sample under evaluation 11 is cooled by the refrigerant 5 of the chiller 2. By repeating this temperature cycle, the thermal shock test is carried out.

[0026] In the present embodiment, the case where a lamp heater is used as a heater capable of locally heating has been described. However, other heat sources may be used. Further, when heating the sample to be evaluated with a lamp heater, the case where heating is performed in a state where a refrigerant is circulated has been described. However, the circulation of the refrigerant may be temporarily stopped. Further, as the sample to be evaluated, a semiconductor module has been exemplified here. However, it can also be applied to other test materials. The place where the sample to be evaluated is placed in the sample chamber is not limited to the bottom surface, and other places are also possible. In this case, the position of the lamp heater may be arranged at a position facing the sample to be evaluated.

[0027] As described above, according to the thermal shock test apparatus according to the first embodiment, in a state where the refrigerant of the chiller is circulated in the sample chamber and cooled to a predetermined temperature, the sample to be evaluated is heated to a high temperature by using a lamp heater capable of locally and rapidly increasing the temperature from a low temperature environment, so that a thermal shock can be applied to the sample to be evaluated, and a highly reliable thermal shock evaluation test can be performed in a short time and at high speed, and there is an effect that the evaluation time can be shortened.

[0028] Embodiment 2. FIG. 3 is a diagram showing a flowchart for explaining the thermal shock test method according to the second embodiment. The thermal shock test apparatus 10 and its configuration are the same as those in the first embodiment, and thus the description thereof will be omitted.

[0029] With reference to FIG. 1, the thermal shock test method will be described using the flowchart of FIG. 3. Here, the case where the thermal shock test is performed on the sample to be evaluated 11 between two temperatures of low temperature and high temperature will be described as an example.

[0030] First, in the step of S01, the temperature sensor 7 is attached to the sample to be evaluated 11 and placed in the sample chamber 4. Then, the inside of the sample chamber 4 is sealed, and the inside of the sample chamber 4 is evacuated (not shown).

[0031] Next, in the step S02, the refrigerant 5 is circulated in the sample chamber 4, and the temperature sensor 7 is used to confirm that the evaluated sample 11 has been cooled to a low temperature of a predetermined temperature.

[0032] Subsequently, in the step S03, a predetermined low temperature is maintained for a predetermined time, and then the lamp heater 6 is energized, and the temperature sensor 7 is used to confirm that the evaluated sample 11 has been heated to a high temperature that is the target temperature.

[0033] Furthermore, in the step S04, the evaluated sample 11 is maintained at a high temperature for a predetermined time, and then the power supply to the lamp heater 6 is cut off to cool the evaluated sample 11. Thereby, the process of the thermal shock test is completed.

[0034] According to the content of the target thermal shock test, the above steps of low temperature and high temperature are repeated the required number of times to perform the thermal shock test. Also, if necessary, it is possible to perform the test with other temperature patterns. In the above series of steps, the control device 1 controls the chiller 2 and the lamp heater 6 based on the temperature detected by the temperature sensor 7.

[0035] Thus, according to the thermal shock test method according to the second embodiment, the refrigerant of the chiller is circulated in the sample chamber to cool it to a predetermined temperature, and the evaluated sample is locally and rapidly heated from a low temperature environment by the lamp heater to be heated to a high temperature, thereby applying a thermal shock to the evaluated sample, and it is possible to perform a highly reliable thermal shock evaluation test in a short time and at high speed, achieving the effect of shortening the evaluation time.

[0036] Also, although various exemplary embodiments and examples are described in the present application, the various features, aspects, and functions described in one or more of the embodiments are not limited to the application of a specific embodiment, but can be applied to the embodiments alone or in various combinations. Accordingly, numerous modifications that are not illustrated are envisioned within the scope of the technology disclosed in the present specification. For example, when modifying, adding, or omitting at least one component, or even when extracting at least one component and combining it with the components of other embodiments shall be included.

Explanation of Signs

[0037] 1 Control device, 2 Chiller, 3 Refrigerant pipe, 4 Sample chamber, 5 Refrigerant, 6 Lamp heater, 7 Temperature sensor, 10 Thermal shock test device, 11 Sample to be evaluated, 12 Mold resin, 13 Semiconductor element, 14 Bonding material, 15 Lead frame.

Claims

1. A sample chamber on which a sample to be evaluated is placed and sealed, A chiller that circulates a refrigerant in the sample chamber to cool the sample chamber, A heater installed in the sample chamber to heat the sample to be evaluated, A temperature sensor that detects the temperature of the sample to be evaluated, A control device that controls the operation of the chiller and the energization and interruption of power supply to the heater based on the temperature, and After the sample chamber is cooled to a predetermined temperature by the chiller, power is supplied to the heater, after the sample to be evaluated is heated to a target temperature, power supply to the heater is interrupted, and the sample to be evaluated is cooled, characterized in that it is a thermal shock test device.

2. The thermal shock test device according to claim 1, characterized in that the heater is a parallel light type of lamp heater.

3. The lamp heater is installed facing the sample to be evaluated, and the size of the sample to be evaluated is within 80% of the soaking length of the peak temperature on the tube surface of the lamp heater, characterized in that it is a thermal shock test device according to claim 2.

4. A step of placing and sealing a sample to be evaluated in a sample chamber, A step of circulating the refrigerant of the chiller in the sample chamber to cool the sample chamber to a predetermined temperature, A step of energizing the heater installed in the sample chamber to heat the sample to be evaluated to a target temperature, A step of interrupting the power supply to the heater to cool the sample to be evaluated, And characterized in that it is a thermal shock test method.

5. The thermal shock test method according to claim 4, characterized in that the heater is a parallel light type of lamp heater.

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