CN110376240B - Longitudinal heat flow method micron line heat conductivity coefficient testing device - Google Patents
Longitudinal heat flow method micron line heat conductivity coefficient testing device Download PDFInfo
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- CN110376240B CN110376240B CN201910600729.5A CN201910600729A CN110376240B CN 110376240 B CN110376240 B CN 110376240B CN 201910600729 A CN201910600729 A CN 201910600729A CN 110376240 B CN110376240 B CN 110376240B
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N25/00—Investigating or analyzing materials by the use of thermal means
- G01N25/20—Investigating or analyzing materials by the use of thermal means by investigating the development of heat, i.e. calorimetry, e.g. by measuring specific heat, by measuring thermal conductivity
Abstract
The invention discloses a longitudinal heat flow method micrometer line heat conductivity coefficient testing device which is composed of a testing device, a base and an optional pressing block for connecting the testing device and the base. The testing device is cut by adopting a low-heat-conductivity insulating plate, the center of the device is provided with a heat source and a heat sink, and metal coils for heating and detecting are prepared on the surfaces of the heat source and the heat sink, wherein the heating coil is used for generating joule heat to heat the heat source, and the detecting coil is used for detecting the temperature of the heat source and the heat sink. The heat source and the heat sink are respectively connected with the edge of the device through six long and thin beams. The sample is suspended between the heat source and the heat sink of the test device, the device is supported by two ends of the base, the two edges of the device connected by the slender beam are supported, and the test device and the base are connected together by using the pressing block. And leading out wires from the bonding pads at the edge of the testing device and connecting the wires to an external testing system. The device has simple structure and convenient operation, and can accurately test the longitudinal heat conductivity coefficient of the insulated micron line.
Description
Technical Field
The invention relates to a testing device, in particular to a longitudinal heat flow method microwire heat conductivity coefficient testing device, and belongs to the technical field of solid material thermophysical property parameter testing.
Background
The microwire of the present invention generally refers to a fiber with a diameter of micrometer magnitude, or a strip-like film with a thickness of micrometer magnitude. The longitudinal thermal conductivity of the microwire can be measured by a direct electrical method or a 3 ω method. Both methods require a heating current of direct or alternating current to be applied to the sample to be measured, and thus require the material to be measured to be a conductor or a semiconductor. If the sample is an insulator, a metal film is deposited on the surface of the sample and then the test is performed. But the consistency of the thickness and quality of the deposited metal film in the length direction of the sample cannot be guaranteed, so that the test result has great uncertainty.
The longitudinal heat flow method can be used to test the longitudinal thermal conductivity of the microwire. In the method, a micron line is placed on a heat source and a heat sink, and heat is conducted from the heat source to the heat sink through a tested sample during testing and finally conducted to a substrate through the heat sink. Compared with a direct current method or a 3 omega method, the method has the advantage that no requirement is made on the conductivity of the tested sample. However, there are also some difficulties in achieving high precision measurement of the longitudinal thermal conductivity of the microwire using this method. For example, to improve the relative accuracy of the heat sink temperature measurement, it is desirable that heat conducted through the measured microwire can generate a sufficiently high temperature rise on the heat sink. This requires that the thermal resistance between the heat sink and the substrate should not be too small, comparable to that of the measured microwire. This brings great challenges to the design of the longitudinal heat flux micrometer line thermal conductivity test device. Those skilled in the art have attempted to solve the above problems, but none of the prior art solutions are ideal.
Disclosure of Invention
The invention provides a device for testing the heat conductivity coefficient of a microwire by a longitudinal heat flow method aiming at the problems in the prior art. When the tested sample is a conductor or a semiconductor, the device can also realize the measurement of the conductivity and the Seebeck coefficient of the sample.
In order to achieve the purpose, the technical scheme of the invention is that the longitudinal heat flow method micrometer line heat conductivity coefficient testing device comprises a testing device, a base and an optional pressing block for connecting the testing device and the base;
the testing device is cut by adopting an insulating plate with low heat conductivity coefficient, the center of the device is provided with a heat source and a heat sink, and the heat source and the heat sink are respectively connected with the edge of the device through six long and thin beams. The method is characterized in that metal heating coils are uniformly distributed on one surface of a heat source, current is applied to the heating coils, and the coils can generate Joule heat, so that the temperature rise of the heat source is realized.
And measuring the temperatures of the heat source and the heat sink by adopting a resistance temperature measurement method. For this purpose, metal detection coils are uniformly distributed on one surface of the heat sink, and the temperature of the heat sink is obtained by detecting the resistance change of the coils. For the heat source, the heating coil may be used as the detection coil at the same time, or a special detection coil may be prepared on the other surface of the heat source. The first scheme can simplify the preparation process of the device, but the heating circuit and the detection circuit are coupled together, so that the detection difficulty is increased. The second scheme is through increasing a preparation process, independently separates heating circuit and detection circuitry, has reduced the detection degree of difficulty.
When the tested sample is a conductor or a semiconductor, the heating coil and the detection coil are encapsulated by using insulating glue in order to avoid the electric short circuit between the heating/detection coil and the tested sample.
Two bare electrodes are respectively prepared on the front surfaces of the heat source and the heat sink and at the adjacent edge positions of the heat source and the heat sink. The four electrodes are used for measuring the conductivity and the Seebeck coefficient of the conductor and the semiconductor micron line.
The tested sample is lapped on the heat source and the heat sink. When the heat conductivity coefficient of the sample is only required to be tested, the contact part of the tested sample and the heat source and the heat sink is coated with silver glue or similar products, so that the contact thermal resistance between the tested sample and the heat source and the heat sink is reduced. When the heat conductivity coefficient of a sample needs to be tested, and the conductivity and the Seebeck coefficient of the sample need to be tested simultaneously, the sample to be tested is ensured to be in full contact with exposed electrodes on a heat source and a heat sink, and the contact part is coated with conductive adhesive, so that the sample and the electrodes are ensured to have good electric contact.
The edge portion of the device is provided with a pad. The heat source, the heating coil above the heat sink, the detection coil, and the electrode are connected to the pad via an elongated beam of the device, and are connected to an external circuit by bonding a wire to the pad.
The device is supported by two ends of the base, and the support positions are two edges of the device connected by the slender beam. The heat source and the heat sink of the device become suspension, and the heat on the heat source and the heat sink needs to be conducted to the edge of the device through the slender beam and then conducted into the base. Because the device is cut from the low-heat-conductivity insulating plate, and the slender beam has a small cross section, the length of the slender beam is adjusted to ensure that the thermal resistance between the heat sink and the base is comparable to that of the measured micrometer wire, thereby ensuring that the heat conducted through the measured micrometer wire can generate enough high temperature rise on the heat sink.
In order to conduct heat transmitted from the slender beam of the device out in time and ensure that the edge temperature of the device is ambient temperature, the substrate material needs to have high thermal conductivity. Meanwhile, the edge of the device is tightly attached to the base, and the thermal contact resistance between the device and the base is reduced. For this purpose, a press block may be used to achieve a tight fit between the device and the base. In order to achieve the effect of attaching and ensure that the device cannot be crushed, the pressing block can be formed by stacking a rigid material and a flexible material.
During testing, the device is placed in the vacuum constant temperature cavity to eliminate the influence of convective heat transfer on a test result and provide a set environmental temperature for the base.
Establishing a heat conduction model according to the Fourier law to obtain the heat conductivity G of the measured micron linesComprises the following steps:
wherein Q ish、QlJoule heat generated in the heating coil and an elongated beam, respectively, is calculated by measuring the heating current, the voltage drop across the coil and the elongated beam. Delta Th、ΔTsRespectively, the temperature rise on the heat source and the heat sink, and can be expressed as:
in the formula, R (I) and R (0) are resistances of the detection coil when the heating current is I and 0, respectively, α is a resistance temperature coefficient, and subscripts and h denote a heat source and a heat sink, respectively. In the test, the resistance of the detection coil is tested by using an alternating-current four-pin ohm method to obtain R (I) and R (0), alpha can be obtained based on the R (0) at different temperatures, and delta T is calculated by the formulah、ΔTs。
Obtaining the longitudinal thermal conductivity G of the samplesThereafter, the thermal conductivity κ of the sample can be calculated:
wherein, A is the cross section area of the micrometer line sample to be tested, and L is the length of the suspended section sample.
Compared with the prior art, the invention has the advantages that (1) the device can realize high-precision measurement of the longitudinal heat conductivity coefficient of the microwire by reasonably designing the thermal resistance among the heat source, the heat sink and the substrate; (2) the device can test the longitudinal heat conductivity coefficient of the micron line, and can simultaneously measure the conductivity and the Seebeck coefficient of a sample when the tested sample conducts electricity.
Drawings
FIG. 1 is a schematic view of the overall structural assembly of the present invention;
FIG. 2 is a schematic diagram of the front side structure of the device;
fig. 3 is a schematic diagram of the device backside structure.
The specific implementation mode is as follows:
example 1: referring to fig. 1 and 2, a longitudinal heat flux microwire thermal conductivity testing apparatus is composed of a testing device 100, a base 200, and an optional pressing block 300 for connecting the two; the testing device is cut by adopting an insulating plate with low heat conductivity coefficient, the center of the device is provided with a heat source 101 and a heat sink 107, and the heat source and the heat sink are respectively connected with the edge of the device through six long and thin beams. A metal heating coil 108 is uniformly formed on one surface of the heat source, and joule heat is generated from the coil by applying a current to the heating coil, thereby increasing the temperature of the heat source.
And measuring the temperatures of the heat source and the heat sink by adopting a resistance temperature measurement method. For this purpose, metal detection coils are uniformly distributed on one surface of the heat sink, and the temperature of the heat sink is obtained by detecting the resistance change of the coils. For the heat source, the heating coil may be used as the detection coil at the same time, or a special detection coil may be prepared on the other surface of the heat source. The first scheme can simplify the preparation process of the device, but the heating circuit and the detection circuit are coupled together, so that the detection difficulty is increased. The second scheme is through increasing a preparation process, independently separates heating circuit and detection circuitry, has reduced the detection degree of difficulty.
When the tested sample is a conductor or a semiconductor, the heating coil and the detection coil are encapsulated by using insulating glue in order to avoid the electric short circuit between the heating/detection coil and the tested sample. Two bare electrodes are respectively prepared on the front surfaces of the heat source and the heat sink and at the adjacent edge positions of the heat source and the heat sink. The four electrodes are used for measuring the conductivity and the Seebeck coefficient of the conductor and the semiconductor micron line.
The tested sample is lapped on the heat source and the heat sink. When the heat conductivity coefficient of the sample is only required to be tested, the contact part of the tested sample and the heat source and the heat sink is coated with silver glue or similar products, so that the contact thermal resistance between the tested sample and the heat source and the heat sink is reduced. When the heat conductivity coefficient of a sample needs to be tested, and the conductivity and the Seebeck coefficient of the sample need to be tested simultaneously, the sample to be tested is ensured to be in full contact with exposed electrodes on a heat source and a heat sink, and the contact part is coated with conductive adhesive, so that the sample and the electrodes are ensured to have good electric contact.
The edge portion of the device is provided with a pad. The heat source, the heating coil above the heat sink, the detection coil, and the electrode are connected to the pad via an elongated beam of the device, and are connected to an external circuit by bonding a wire to the pad.
The device is supported by two ends of the base, and the support positions are two edges of the device connected by the slender beam. The heat source and the heat sink of the device become suspension, and the heat on the heat source and the heat sink needs to be conducted to the edge of the device through the slender beam and then conducted into the base. Because the device is cut from the low-heat-conductivity insulating plate, and the slender beam has a small cross section, the length of the slender beam is adjusted to ensure that the thermal resistance between the heat sink and the base is comparable to that of the measured micrometer wire, thereby ensuring that the heat conducted through the measured micrometer wire can generate enough high temperature rise on the heat sink.
In order to conduct heat transmitted from the slender beam of the device out in time and ensure that the edge temperature of the device is ambient temperature, the substrate material needs to have high thermal conductivity. Meanwhile, the edge of the device is tightly attached to the base, and the thermal contact resistance between the device and the base is reduced. For this purpose, a press block may be used to achieve a tight fit between the device and the base. In order to achieve the effect of attaching and ensure that the device cannot be crushed, the pressing block can be formed by stacking a rigid material and a flexible material.
During testing, the device is placed in the vacuum constant temperature cavity to eliminate the influence of convective heat transfer on a test result and provide a set environmental temperature for the base.
The heat conduction model is established according to the Fourier law, and canObtaining the thermal conductivity G of the measured micron linesComprises the following steps:
wherein Q ish、QlJoule heat generated in the heating coil and an elongated beam, respectively, is calculated by measuring the heating current, the voltage drop across the coil and the elongated beam. Delta Th、ΔTsRespectively, the temperature rise on the heat source and the heat sink, and can be expressed as:
in the formula, R (I) and R (0) are resistances of the detection coil when the heating current is I and 0, respectively, α is a resistance temperature coefficient, and subscripts and h denote a heat source and a heat sink, respectively. In the test, the resistance of the detection coil is tested by using an alternating-current four-pin ohm method to obtain R (I) and R (0), alpha can be obtained based on the R (0) at different temperatures, and delta T is calculated by the formulah、ΔTs。
Obtaining the longitudinal thermal conductivity G of the samplesThereafter, the thermal conductivity κ of the sample can be calculated:
wherein, A is the cross section area of the micrometer line sample to be tested, and L is the length of the suspended section sample.
Application example 1: referring to fig. 1 to 3, the apparatus for testing the heat conductivity of a microwire by the longitudinal thermal flow method in the present embodiment is shown in fig. 1, and is composed of a testing device 100, a base 200, and an optional pressing block 300 for connecting the two.
The test device 100 is integrally cut from an FR-4 board with a thickness of 1mm, as shown in fig. 2. FR-4 board has a low thermal conductivity of about 0.294W/m-K. The device 100 comprises a heat source 101 and a heat sink 107, the heat source 101 and the heat sink 107 being connected to the edge 104 of the device 100 by six elongated beams 103, respectively. The heat source 101 and the heat sink 107 are square, and the side length is 10 mm. The distance between the heat source 101 and the heat sink 107 may vary from 4-16mm depending on testing requirements. Uniformly distributed copper heating coils 108 are prepared on the back surfaces of the heat source 101 and the heat sink 107, wherein the line width of copper is 0.2mm, the thickness of the copper is 35 mu m, and the total length of the copper heating coils is about 285 mm. For convenience of use, copper heating coils 108 are prepared on the back surfaces of the heat source 101 and the heat sink 107, so that the heat source 101 and the heat sink 107 of the device 100 are completely symmetrical, and when the device is connected with an external circuit, no distinction is needed between which side is the heat source 101 and which side is the heat sink 107.
The same copper detection coils 102 are prepared on the front surfaces of the heat source 101 and the heat sink 107, and the temperature changes of the heat source 101 and the heat sink 107 can be obtained through the resistance changes of the detection coils 102. The line width of the detection line copper is 0.1mm, the thickness is 35 mu m, and the total length is 273 mm. In order to avoid direct communication between the detection coil 102 and the conductive sample 400 being measured, a layer of ink solder resist (PSR-4000GF5) is applied to the detection coil 102.
Two bare copper electrodes 106 are respectively prepared on the front surfaces of the heat source 101 and the heat sink 107 and at the adjacent edge positions of the heat source and the heat sink. The electrodes 106 are 0.5mm and 0.3mm wide, respectively, with a spacing of 0.9 mm. The four electrodes 106 are externally connected with a power supply 1000, an ammeter 900 and a voltmeter 1100, and are used for measuring the conductivity and the Seebeck coefficient of conductors and semiconductors.
The sample 400 to be measured is lapped on the heat source 101 and the heat sink 107. When the thermal conductivity of the sample 400 is only required to be tested, the contact part of the sample 400 to be tested and the heat source 101 and the heat sink 107 is coated with conductive silver paste or similar products, so that the thermal contact resistance between the sample 400 to be tested and the heat source 101 and the heat sink 107 is reduced. When the thermal conductivity of the sample 400 needs to be tested, and the conductivity and the seebeck coefficient of the sample 400 need to be tested at the same time, the sample 400 to be tested is ensured to be in full contact with the heat source 101 and the electrode 106 on the heat sink 107, and the contact part between the sample 400 and the electrode 106 is coated with the conductive silver adhesive, so that the sample 400 and the electrode 106 are ensured to have good electrical contact.
The front side of the edge 104 of the device 100 prepares the pads 105. The heat source 101, the heating coil 108 on the heat sink 107, the detection coil 102, and the electrode 106 are connected to the pad 105 via the elongated beam 103 of the device 100, and are connected to an external circuit by bonding a wire on the pad 105.
The device 100 is supported at both ends by a base 200 at the edges 104 of the device 100 where elongated beams 103 are attached. Thus, the heat source 101 and the heat sink 107 of the device 100 become suspended, and the heat on the heat source 101 and the heat sink 107 needs to be conducted to the edge 104 of the device 100 through the elongated beam 103 and further into the base 200.
The device 100 is cut from an insulating FR-4 sheet material having a thermal conductivity of 0.294W/m-K, plus the cross-sectional area of the elongate beam 103 is only 0.6mm2The single length of the elongated beam 103 is 13mm, so the total thermal conductance from the heat sink 107 to the base 200 is about 8.14154 x 10-5W/K. Assuming that the length of the suspended section of the measured micrometer wire is 5mm, the width is 1mm, the thickness is 10 micrometers, and the thermal conductivity of the sample is 10W/m-K, the thermal conductivity of the sample is about 2 multiplied by 10-5W/K. The ratio of the two is about 4: 1. thereby ensuring that heat conducted through the measured microwire can generate a sufficiently high temperature rise on the heat sink 107.
In order to conduct away the heat transferred from the elongated beam 103 of the device 100 in time and to ensure that the temperature of the edge 104 of the device 100 is ambient, the base 200 is fabricated from oxygen-free copper having a thermal conductivity of about 409W/m-K. Meanwhile, the edge 104 of the device 100 is tightly attached to the base 200, so that the thermal contact resistance between the two is reduced. To this end, a compact 300 is used to achieve a tight fit between the device 100 and the base 200. To achieve the effect of the attachment, the heat source 101, the heating coil 108 on the back of the heat sink 107 need to be connected to the front side and then connected to the pad 105 through the elongated beam 103. In order to ensure that the device 100 is not damaged by pressure, the pressing block 300 is formed by stacking a copper sheet and a PDMS film.
During testing, the device 100 is placed in a vacuum thermostatic chamber to eliminate the influence of convective heat transfer on the test result and to provide a set ambient temperature for the base 200.
It should be noted that the above-mentioned embodiments are not intended to limit the scope of the present invention, and all equivalent modifications and substitutions based on the above-mentioned technical solutions are within the scope of the present invention as defined in the claims.
Claims (5)
1. The longitudinal heat flow method micrometer line heat conductivity coefficient testing device is characterized by comprising a testing device, a base and a pressing block for connecting the testing device and the base;
the testing device is cut by adopting an insulating plate with low heat conductivity coefficient, the center of the device is provided with a heat source and a heat sink, the heat source and the heat sink are respectively connected with the edge of the device through six long and thin beams, a metal heating coil is uniformly distributed on one surface of the heat source, current is applied to the heating coil, and the coil can generate joule heat, so that the temperature rise of the heat source is realized;
the test device is cut from an insulating FR-4 plate with a thermal conductivity of 0.294W/m-K, and the cross-sectional area of the slender beam is 0.6mm2The length of the single long beam is 13mm, and the total heat conductance between the heat sink and the base is 8.14154 multiplied by 10-5W/K, the length of the suspended section of the measured micrometer wire is 5mm, the width is 1mm, the thickness is 10 micrometers, the heat conductivity coefficient of the sample is 10W/m-K, and the heat conductivity of the sample is 2 multiplied by 10-5W/K, ensuring that the heat conducted through the measured micron line can generate enough temperature rise on the heat sink;
the device is supported by two ends of the base, two edges of the device connected with the slender beam are supported at the supporting position, and the device is tightly attached to the base by using a pressing block;
the base is made of oxygen-free copper with the heat conductivity coefficient of 409W/m-K, and in order to achieve the attaching effect and simultaneously ensure that the device cannot be crushed, the pressing block is formed by stacking a rigid material and a flexible material;
two bare electrodes are respectively prepared on the front surfaces of the heat source and the heat sink and at the adjacent edge positions of the heat source and the heat sink, and the four electrodes are used for measuring the conductive performance and the Seebeck coefficient of a conductor and a semiconductor;
measuring the temperature of a heat source and a heat sink by adopting a resistance temperature measurement method, preparing uniformly distributed metal detection coils on one surface of the heat sink, and obtaining the temperature of the heat sink through detecting the resistance change of the coils;
a detection coil is prepared on the other surface of the heat source, so that the heating circuit and the detection circuit are independent, and the detection difficulty is reduced.
2. The device for testing the heat conductivity of microwire by the longitudinal heat flow method according to claim 1, wherein the heating coil and the detection coil are encapsulated with an insulating paste.
3. The apparatus according to claim 2, wherein the testing device is provided with a bonding pad at the edge thereof, and the heat source, the heating coil on the heat sink, the detection coil, and the electrode are connected to the bonding pad via the elongated beam of the device, and connected to an external circuit by soldering a wire to the bonding pad.
4. The device for testing the heat conductivity coefficient of a micron line by the longitudinal heat flow method according to claim 3, wherein the device is placed in a vacuum thermostatic chamber during testing.
5. The measurement method of the longitudinal heat flow method microwire thermal conductivity coefficient test device according to any one of claims 1 to 4 is characterized in that: the tested sample is lapped on the heat source and the heat sink, and when the heat conductivity coefficient of the tested sample is only required to be tested, the contact position of the tested sample and the heat source and the heat sink is coated with silver paste, so that the thermal contact resistance between the tested sample and the heat source and the heat sink is reduced; when the heat conductivity coefficient of a sample needs to be tested, and the conductivity and the Seebeck coefficient of the sample need to be tested simultaneously, the sample to be tested is ensured to be in full contact with exposed electrodes on a heat source and a heat sink, and conductive adhesive is coated on the contact position of the sample and the electrodes, so that the sample and the electrodes are ensured to have good electrical contact.
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