Thermal resistance evaluation device, thermal resistance evaluation method, and thermal resistance evaluation program

Abstract

To provide a thermal resistance evaluation device, a method therefor, and a program with which it is possible to evaluate thermal resistance of an evaluation object that has low thermal resistance, said device and method evaluating the thermal resistance of a heat radiation substrate.SOLUTION: A thermal resistance evaluation device comprises: a high-temperature block 11 that is almost kept at a first temperature; a low-temperature block 21; a circulating device 22 that circulates constant-temperature water almost kept at a second temperature to a circulation path 23 passing inside of the low-temperature block 21; and a calculation unit 41 that calculates a rate of heat flow from the high-temperature block 11 side to the low-temperature block 21 side, on the basis of a temperature difference in constant-temperature water between the inlet side and outlet side temperatures of the low-temperature block 21 when a sample is disposed between the high-temperature block 11 and the low-temperature block 21, and a flow rate and a calorific capacity of constant-temperature water. An evaluation function that indicates heat flow rate dependency of thermal resistance of a standard sample is acquired from the heat flow rate calculated when a standard sample having known thermal resistance is disposed in place. The heat flow rate calculated when an unknown sample whose thermal resistance is unknown is disposed in place, is applied to the evaluation function so as to calculate the thermal resistance of the unknown sample.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a thermal resistance evaluation device, a thermal resistance evaluation method, and a thermal resistance evaluation program for evaluating the thermal resistance of a heat dissipation substrate.

Background Art

[0002] As a method for evaluating the thermal resistance of an entire sample, there is a temperature gradient method. This method is based on the steady-state method and is standardized as JIS H7903 and ASTM D 5470.

[0003] For example, in the temperature gradient method (one-direction heat flow steady-state comparison method) described in JIS H7903, heat is made to flow in one direction through two standard rods made of a bar material with a known thermal conductivity and a test piece sandwiched between the two standard rods. The effective thermal conductivity is obtained from the temperature distribution at steady state in the test piece and the standard rods.

Prior Art Documents

Non-Patent Documents

[0004]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the case where the evaluation target is a heat dissipation substrate with a small thermal resistance, etc., the thermal resistance of the standard rod becomes larger than the thermal resistance of the test piece, it becomes difficult for a temperature difference to occur in the test piece, and the temperature distribution necessary for evaluation cannot be obtained. For this reason, when the test piece is a heat dissipation substrate with a small thermal resistance, etc., the difference in thermal resistance between the test piece and the standard rod cannot be detected as a heat flow rate, and the temperature gradient method cannot be used.

[0006] This invention has been made in consideration of these circumstances, and aims to provide a thermal resistance evaluation device, a thermal resistance evaluation method, and a thermal resistance evaluation program for evaluating the thermal resistance of a heat dissipation substrate capable of evaluating the thermal resistance of an object to be evaluated that has low thermal resistance. [Means for solving the problem]

[0007] The thermal resistance evaluation apparatus according to the present invention is a thermal resistance evaluation apparatus for evaluating the thermal resistance of an unknown sample whose thermal resistance is unknown, in order to solve the above-mentioned problems, and comprises: a high-temperature block maintained at a first temperature; a low-temperature block; a circulation device that circulates constant-temperature water maintained at a second temperature lower than the first temperature in a circulation path passing through the low-temperature block; a calculation unit that calculates the heat flow rate from the high-temperature block side to the low-temperature block side based on the temperature difference between the inlet and outlet temperatures of the constant-temperature water in the low-temperature block, the flow velocity of the constant-temperature water in the circulation path, and the heat capacity of the constant-temperature water when a sample is placed between the high-temperature block and the low-temperature block; an acquisition unit that obtains an evaluation function showing the dependence of the thermal resistance of the standard sample on the heat flow rate from the heat flow rate calculated by the calculation unit when a standard sample with known thermal resistance is placed between the high-temperature block and the low-temperature block; and a thermal resistance evaluation unit that calculates the thermal resistance of the unknown sample by applying the heat flow rate calculated by the calculation unit when the unknown sample is placed between the high-temperature block and the low-temperature block to the evaluation function. Furthermore, the thermal resistance evaluation method according to the present invention is a thermal resistance evaluation method for evaluating the thermal resistance of an unknown sample whose thermal resistance is unknown, comprising the steps of: preparing a high-temperature block maintained at a first temperature, a low-temperature block, and a circulation device that circulates constant-temperature water maintained at a second temperature lower than the first temperature through a circulation path passing through the low-temperature block; and placing a standard sample with known thermal resistance between the high-temperature block and the low-temperature block, and evaluating the high-temperature block based on the temperature difference between the inlet and outlet temperatures of the constant-temperature water in the low-temperature block, the flow velocity of the constant-temperature water in the circulation path, and the heat capacity of the constant-temperature water. The method comprises the steps of: calculating the heat flow rate from the lock side to the low-temperature block side, and obtaining an evaluation function showing the heat flow rate dependence of the thermal resistance of the standard sample from the calculated heat flow rate; and arranging the unknown sample between the high-temperature block and the low-temperature block, calculating the heat flow rate from the high-temperature block side to the low-temperature block side based on the temperature difference between the inlet and outlet temperatures of the constant-temperature water in the circulation path of the constant-temperature water, and the heat capacity of the constant-temperature water, and applying the calculated heat flow rate to the evaluation function to calculate the thermal resistance of the unknown sample. Furthermore, the thermal resistance evaluation program according to the present invention evaluates the thermal resistance of an unknown sample whose thermal resistance is unknown, based on information obtained from a thermal resistance evaluation device comprising a high-temperature block maintained at a first temperature, a low-temperature block, and a circulation device that circulates constant-temperature water maintained at a second temperature lower than the first temperature through a circulation path passing through the low-temperature block, and is based on the temperature difference between the inlet and outlet temperatures of the constant-temperature water in the low-temperature block, the flow velocity of the constant-temperature water in the circulation path, and the heat capacity of the constant-temperature water, which are obtained when a standard sample with known thermal resistance is placed between the high-temperature block and the low-temperature block. The computer is made to perform the following steps: calculate the heat flow rate from the high-temperature block to the low-temperature block, and obtain an evaluation function showing the heat flow rate dependence of the thermal resistance of the standard sample from the calculated heat flow rate; and calculate the heat flow rate from the high-temperature block to the low-temperature block based on the temperature difference between the inlet and outlet temperatures of the constant-temperature water in the low-temperature block, the flow velocity of the constant-temperature water in the circulation path, and the heat capacity of the constant-temperature water, which are obtained when the unknown sample is placed between the high-temperature block and the low-temperature block, and apply the calculated heat flow rate to the evaluation function to calculate the thermal resistance of the unknown sample. [Effects of the Invention]

[0008] The thermal resistance evaluation apparatus, thermal resistance evaluation method, and thermal resistance evaluation program according to the present invention can evaluate the thermal resistance of an object to be evaluated that has low thermal resistance. [Brief explanation of the drawing]

[0009] [Figure 1] A schematic diagram illustrating the thermal resistance evaluation apparatus in this embodiment. [Figure 2] A graph showing an example of an evaluation function. [Modes for carrying out the invention]

[0010] Embodiments of the thermal resistance evaluation apparatus 1, thermal resistance evaluation method, and thermal resistance evaluation program according to the present invention will be described based on the attached drawings.

[0011] The thermal resistance evaluation apparatus 1, thermal resistance evaluation method, and thermal resistance evaluation program in this embodiment are used to evaluate the thermal resistance of an unknown sample whose thermal resistance is unknown. In the following description, the present invention will be explained using an example in which the object of evaluation is a heat dissipation substrate with low thermal resistance. The present invention is particularly effective for such heat dissipation substrates, but the object of evaluation is not limited to this.

[0012] Figure 1 is a schematic diagram illustrating the thermal resistance evaluation device 1 in this embodiment.

[0013] The thermal resistance evaluation device 1 includes a high-temperature block 11, a heater 12, a high-temperature side temperature sensor 13, a low-temperature block 21, a circulation device 22, a low-temperature side temperature sensor 26, a flow meter 27, and a calculation device 40.

[0014] The high-temperature block 11 is a block-shaped member mainly formed from a material with good thermal conductivity (for example, copper (Cu), aluminum (Al), or nickel (Ni)). The surface of the high-temperature block 11 facing downwards in the figure is the contact surface with the sample 2 via the thermal bonding material 30 (described later).

[0015] The heater 12 is located inside the high-temperature block 11 and controls the temperature of the high-temperature block 11 to maintain it at a nearly constant first temperature (e.g., 50 degrees Celsius).

[0016] The high-temperature side temperature sensor 13 is positioned near the contact surface of the high-temperature block 11 and measures the temperature of the high-temperature block 11. The high-temperature side temperature sensor 13 is, for example, a platinum resistance thermometer or a thermocouple. The temperature measured by the high-temperature side temperature sensor 13 is used for temperature control of the high-temperature block 11 in the heater 12.

[0017] The low-temperature block 21 is a block-shaped member mainly formed from a material with good thermal conductivity, similar to the high-temperature block 11. The surface of the low-temperature block 21 facing upward in the figure is the contact surface with the sample 2 via the thermal bonding material 30.

[0018] The high-temperature block 11 and the low-temperature block 21 are defined as the "high-temperature" block and the "low-temperature" block because, during the evaluation of the thermal resistance, they are controlled such that the former is relatively at a high temperature and the latter at a low temperature.

[0019] The circulation device 22 circulates the constant-temperature water in the circulation path 23 and controls the low-temperature block 21 to a temperature lower than that of the high-temperature block 11. The circulation device 22 has a circulation path 23 and a device main body 24.

[0020] The circulation path 23 is a flow path of the constant-temperature water that passes through the inside of the low-temperature block 21 and circulates between the inside of the low-temperature block 21 and the device main body 24.

[0021] The device main body 24 maintains (cools) the constant-temperature water at a second temperature (for example, 20 degrees) lower than the first temperature. The device main body 24 sends out the constant-temperature water controlled to the second temperature into the circulation path 23 by a pump. Thereby, the constant-temperature water cools the low-temperature block 21.

[0022] The low-temperature side temperature sensors 26 are arranged at the inlet side and the outlet side of the low-temperature block 21 of the circulation path 23, and measure the inlet side temperature and the outlet side temperature of the low-temperature block 21.

[0023] The flow meter 27 is arranged at a required position of the circulation path 23, and obtains the flow velocity of the constant-temperature water by measuring the flow rate of the constant-temperature water in the circulation path 23.

[0024] The thermal bonding materials 30 are a pair of members that thermally contact the contact surfaces of the high-temperature block 11 and the low-temperature block 21 and the sample 2 to improve the thermal conductivity. The thermal bonding materials 30 are, for example, sheet-like members having excellent thermal conductivity (low thermal resistance).

[0025] The arithmetic unit 40 is a computer composed of a CPU, a ROM, a RAM, etc., and executes a thermal resistance evaluation program. This thermal resistance evaluation program is executed to evaluate the unknown thermal resistance of the evaluation object, and causes the arithmetic unit 40 to function as a heat flow rate calculation unit 41, a function acquisition unit 42, and a thermal resistance evaluation unit 43.

[0026] The heat flow rate calculation unit 41 (calculation unit) calculates the heat flow rate from the high-temperature block 11 to the low-temperature block 21. Specifically, the heat flow rate calculation unit 41 is connected to the low-temperature side temperature sensor 26 and flow meter 27, and acquires the measurement results of each. Based on the inlet temperature Tin, outlet temperature Tout (temperature difference between the inlet temperature Tin and the outlet temperature Tout), flow velocity v, and volumetric specific heat capacity C of the constant-temperature water, which are acquired when the sample 2 is placed between the high-temperature block 11 and the low-temperature block 21, the heat flow rate calculation unit 41 calculates the heat flow rate Q, which is the amount of heat that has flowed into the constant-temperature water, from the following equation 1.

[0027] [Formula 1] Heat flow Q = Cv(Tout - Tin)

[0028] The function acquisition unit 42 (acquisition unit) acquires an evaluation function showing the heat flow dependence of thermal resistance from the heat flow rate Qs calculated by the heat flow rate calculation unit 41 when a standard sample is placed as sample 2 between the high-temperature block 11 and the low-temperature block 21. The standard sample is a sample made of a material with a known thermal resistance, such as copper (Cu), aluminum (Al), S50C (carbon steel for machine structures), SUS304 (stainless steel), or quartz glass (SiO2).

[0029] The function acquisition unit 42 measures the heat flow rate using, for example, two types of standard samples, and fits the correlation with the obtained thermal resistance to acquire an evaluation function consisting of an arbitrary function. Alternatively, the function acquisition unit 42 may use four or five types of standard samples, and depending on the unknown sample to be evaluated, any evaluation function can be acquired using any standard sample and fitting (approximation) method. The function acquisition unit 42 stores the acquired evaluation function in advance prior to the thermal resistance evaluation by the thermal resistance evaluation unit 43.

[0030] The thermal resistance evaluation unit 43 calculates and evaluates the thermal resistance of the unknown sample by applying the heat flow rate Qu calculated by the heat flow rate calculation unit 41 when the unknown sample is placed as sample 2 between the high-temperature block 11 and the low-temperature block 21 to an evaluation function.

[0031] Next, we will explain the method for evaluating thermal resistance using the thermal resistance evaluation device 1.

[0032] First, a standard sample with known thermal resistance is placed between the high-temperature block 11 and the low-temperature block 21 of the thermal resistance evaluation device 1 via a thermal bonding material 30. Next, the heater 12 heats the high-temperature block 11 while monitoring the temperature with the high-temperature side temperature sensor 13, maintaining the high-temperature block 11 at a first temperature. The circulation device 22 cools the low-temperature block 21 with constant-temperature water by circulating constant-temperature water, which is maintained at a second temperature, through the circulation path 23.

[0033] The computing unit 40 executes the procedure described below by running the thermal resistance evaluation program.

[0034] The heat flow rate calculation unit 41 calculates the heat flow rate Qs (amount of heat flowing to the constant temperature water) from the high temperature block 11 to the low temperature block 21 based on the temperature difference between the inlet temperature Tin and the outlet temperature Tout of the low temperature block 21 of the constant temperature water, the flow velocity v in the circulation path 23 of the constant temperature water, and the volumetric specific heat capacity C of the constant temperature water (Equation 1).

[0035] Furthermore, the function acquisition unit 42 acquires and stores an evaluation function that shows the heat flow dependence of the thermal resistance of the standard sample from the calculated heat flow rate Qs of the standard sample. Here, Figure 2 is a graph showing an example of the evaluation function.

[0036] Next, the standard sample placed in the thermal resistance evaluation device 1 is replaced with an unknown sample. The heat flow rate calculation unit 41 measures the heat flow rate Qu for the unknown sample using the same procedure as for the heat flow rate Qs. The thermal resistance evaluation unit 43 calculates the thermal resistance of the unknown sample by applying the calculated heat flow rate Qu to the evaluation function, thereby evaluating the thermal resistance of the unknown sample. This concludes the thermal resistance evaluation method.

[0037] The thermal resistance evaluation apparatus 1, method, and program in this embodiment are capable of suitably evaluating thermal resistance even when the object to be evaluated is an unknown sample with low thermal resistance. In other words, evaluation methods using the temperature gradient method, which are suitable for materials with low thermal conductivity such as thermoelectric conversion elements, are difficult to apply to objects to be evaluated that have low thermal resistance, such as heat dissipation substrates, due to their measurement principle. Another known method for evaluating thermal resistance (heat dissipation) is the flash method. However, when the object to be evaluated is a composite material in which multiple layers are laminated, such as a layer made of a pair of materials with high thermal conductivity and a layer made of insulating material placed between them, the accuracy of the measurement results may not be obtained depending on the bonding conditions of the multiple layers. For this reason, the flash method is also not suitable for evaluating the thermal resistance of a heat dissipation substrate which is a composite material.

[0038] In contrast, the thermal resistance evaluation device 1 in this embodiment has the low-temperature block 21 also perform the measurement of heat flow rate. Furthermore, the thermal resistance of the unknown sample is evaluated by applying the calculated heat flow rate of the unknown sample to a previously acquired evaluation function relating to the heat flow rate dependence of thermal resistance. As a result, the thermal resistance evaluation device 1, its method, and program in this embodiment can suitably evaluate even heat dissipation substrates for which evaluation of thermal resistance using the temperature gradient method is difficult.

[0039] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the claims. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents. [Explanation of symbols]

[0040] 1. Thermal resistance evaluation device 2 samples 11 High-temperature block 12 Heaters 13. High-temperature side temperature sensor 21 Low-temperature blocks 22 Circulation device 23 Circulation path 24 Main unit of the device 26 Low-temperature sensor 27 Flow meter 30 Thermal bonding material 40 Arithmetic unit 41 Heat flow calculation section 41 Calculation Section 42 Function acquisition section 43 Thermal resistance evaluation unit

Claims

1. A thermal resistance evaluation device for evaluating the thermal resistance of an unknown sample whose thermal resistance is unknown, A high-temperature block maintained at approximately the first temperature, Low-temperature blocks and A circulation device that circulates constant-temperature water, maintained at a second temperature lower than the first temperature, through a circulation path passing through the low-temperature block, A calculation unit calculates the heat flow rate from the high-temperature block to the low-temperature block based on the temperature difference between the inlet and outlet temperatures of the constant-temperature water in the low-temperature block when a sample is placed between the high-temperature block and the low-temperature block, the flow velocity of the constant-temperature water in the circulation path, and the heat capacity of the constant-temperature water. An acquisition unit that fits the correlation obtained from the heat flow rate calculated by the calculation unit when a standard sample with known thermal resistance is placed between the high-temperature block and the low-temperature block to multiple types of standard samples and obtains an evaluation function showing the dependence of the thermal resistance on the heat flow rate, A thermal resistance evaluation device comprising: a thermal resistance evaluation unit that calculates the thermal resistance of the unknown sample by applying the heat flow rate calculated by the calculation unit when the unknown sample is placed between the high-temperature block and the low-temperature block to the evaluation function.

2. The thermal resistance evaluation apparatus according to claim 1, wherein the unknown sample is a composite material in which multiple layers are stacked.

3. A method for evaluating the thermal resistance of an unknown sample whose thermal resistance is unknown, A step of preparing a high-temperature block maintained at approximately a first temperature, a low-temperature block, and a circulation device that circulates constant-temperature water maintained at approximately a second temperature lower than the first temperature through a circulation path passing through the low-temperature block, The process involves placing a standard sample with known thermal resistance between the high-temperature block and the low-temperature block, calculating the heat flow rate from the high-temperature block to the low-temperature block based on the temperature difference between the inlet and outlet temperatures of the constant-temperature water in the circulation path, and the heat capacity of the constant-temperature water, fitting the correlation obtained from the calculated heat flow rate to multiple types of standard samples, and obtaining an evaluation function that shows the dependence of the thermal resistance on the heat flow rate. A method for evaluating thermal resistance, comprising the steps of: placing the unknown sample between the high-temperature block and the low-temperature block; calculating the heat flow rate from the high-temperature block to the low-temperature block based on the temperature difference between the inlet and outlet temperatures of the constant-temperature water in the circulation path of the constant-temperature water and the heat capacity of the constant-temperature water; and applying the calculated heat flow rate to the evaluation function to calculate the thermal resistance of the unknown sample.

4. A thermal resistance evaluation program that evaluates the thermal resistance of an unknown sample whose thermal resistance is unknown, based on information obtained from a thermal resistance evaluation device comprising a high-temperature block maintained at approximately a first temperature, a low-temperature block, and a circulation device that circulates constant-temperature water maintained at approximately a second temperature lower than the first temperature through a circulation path passing through the low-temperature block, A procedure for obtaining an evaluation function that shows the dependence of the thermal resistance on the thermal flow rate of the thermal resistance, based on the temperature difference between the inlet and outlet temperatures of the constant-temperature water in the low-temperature block, the flow velocity of the constant-temperature water in the circulation path, and the heat capacity of the constant-temperature water, obtained when a standard sample with a known thermal resistance is placed between the high-temperature block and the low-temperature block, and then fitting the correlation obtained from the calculated thermal flow rate to multiple types of standard samples, and further, A procedure for calculating the heat flow rate from the high-temperature block to the low-temperature block based on the temperature difference between the inlet and outlet temperatures of the constant-temperature water in the low-temperature block, the flow velocity of the constant-temperature water in the circulation path, and the heat capacity of the constant-temperature water, obtained when the unknown sample is placed between the high-temperature block and the low-temperature block, and applying the calculated heat flow rate to the evaluation function to calculate the thermal resistance of the unknown sample, A thermal resistance evaluation program that is executed by a computer.

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