Temperature sensor and manufacturing method therefor

Abstract

The present invention comprises: a chip that includes a thermopile, and a first conductive part for outputting a thermo-electromotive signal generated by the thermopile; a flexible first film that includes a cavity which is provided on one surface of the film and is capable of accommodating the chip, a second conductive part which is electrically connected to the first conductive part, while the chip is accommodated in the cavity, and which has at least a portion thereof provided in the cavity, and an electrode that is electrically connected to the second conductive part to output the thermo-electromotive signal to a predetermined device; and a flexible second film that is bonded to the one surface of the first film to seal the chip.

Description

Temperature sensor and manufacturing method

[0001] The present invention relates to a temperature sensor using a thermopile and a manufacturing method thereof.

[0002] 2. Description of the Related Art A temperature sensor is known that measures the temperature of an object by bringing one surface into contact with the surface of the object (see Patent Document 1).

[0003] JP 2015-114291 A U.S. Patent Application Publication No. 2000 / 13942

[0004] The temperature sensor described in Patent Document 1 is configured by providing a heat flux sensor on a main board and encasing the heat flux sensor in a housing that forms a space around the heat flux sensor. The heat flux sensor is a small temperature difference sensor manufactured using a MEMS (Micro Electro Mechanical Systems) process. The heat flux sensor has a thermopile formed by connecting multiple thermocouples in series, each made of P-type polysilicon and N-type polysilicon. The heat flux sensor is isolated and protected from the space by being covered by the housing, and measures the temperature of the object to be measured based on the temperature difference between the air temperature on the housing side and the temperature of the object to be measured.

[0005] On the other hand, Patent Document 2 discloses a heat flow meter that uses a flexible substrate without using MEMS as a heat flux sensor. The heat flow meter described in Patent Document 2 uses a flexible substrate, which ensures a certain degree of flexibility. However, the measurement points are dispersed due to the arrangement of the thermocouples, making it unsuitable for measuring the temperature of a specific point. Furthermore, this heat flow meter requires the thermocouples and heat conduction pads to be arranged over a wide area on the flexible substrate, which also reduces flexibility.

[0006] As described above, the temperature sensor described in Patent Document 1 is configured so that the heat flux sensor is covered with a housing, making it difficult to provide the flexibility required to fit the shape of the object to be measured. Furthermore, as mentioned above, it is also difficult to provide the heat flux sensor described in Patent Document 2 with the desired flexibility. Therefore, these sensors may be unable to be applied to the shape of the object to be measured.

[0007] The present invention has been made in view of the above circumstances, and has an object to provide a temperature sensor that can accommodate various shapes of measurement objects.

[0008] A temperature sensor according to one aspect of the present invention comprises a chip having a thermopile and a first conductive portion for outputting a thermoelectric signal generated by the thermopile; a flexible first film having a cavity provided on one side capable of accommodating the chip, a second conductive portion at least a portion of which is provided within the cavity and electrically connected to the first conductive portion when the chip is accommodated in the cavity, and an electrode electrically connected to the second conductive portion for outputting the thermoelectric signal to a specified device; and a flexible second film bonded to the one side of the first film so as to seal the chip.

[0009] A manufacturing method according to one aspect of the present invention includes the steps of: placing a flexible first film at a predetermined position, the film having on one side thereof a cavity, a first electrode, and a conductive path extending from the cavity to the first electrode; placing a conductive member within the cavity so as to be in electrical contact with a portion of the conductive path exposed within the cavity; placing a chip within the cavity, the chip having a thermopile and a second electrode for outputting a thermoelectric signal generated by the thermopile, so that the second electrode and the conductive member are electrically connected; and bonding a flexible second film formed of an insulating material to the one side of the first film so as to seal the chip.

[0010] According to the present invention, it is possible to provide a temperature sensor that can accommodate various shapes of measurement objects.

[0011] FIG. 1 is a diagram showing an example of a temperature sensor; FIG. 2 is a diagram showing an example of a temperature sensor with an enlarged main surface; FIG. 3 is a diagram showing an example of a temperature sensor in which a plurality of chips are connected in series; FIG. 4 is a diagram showing an example of wiring connections when a plurality of chips are connected in series and in parallel; FIG. 5 is a diagram showing an example of a chip configuration; FIG. 6 is a flowchart of a method for manufacturing a temperature sensor; and FIG. 7 is a schematic diagram showing the assembly of components of a temperature sensor.

[0012] The following describes embodiments of the present invention. In the following description of the drawings, the same or similar components are denoted by the same or similar reference numerals. The drawings are illustrative, and the dimensions and shapes of each part are schematic. The technical scope of the present invention should not be interpreted as being limited to the embodiments.

[0013] ===Configuration of Temperature Sensor 100=== The temperature sensor 100 will be described with reference to Figures 1 to 4. Figure 1 is a diagram showing an example of the temperature sensor 100. Figure 2 is a diagram showing an example of a temperature sensor 100a with an enlarged main surface. Figure 3 is a diagram showing an example of a temperature sensor 100b in which multiple chips 110 are connected in series. Figure 4 is a diagram showing an example of a connection state when multiple chips 110 are connected in series and in parallel.

[0014] The temperature sensor 100 is a sensor that can measure heat emitted from a measurement object or heat flowing from the measurement object to another object with high speed response and high accuracy.

[0015] As shown in FIG. 1, the temperature sensor 100 includes, for example, a chip 110, a first film 120, and a second film .

[0016] The chip 110 is a MEMS type element, and outputs a thermoelectric signal indicating an electromotive force ΔV generated based on a temperature difference ΔT between a membrane cavity 112 (to be described later) and a silicon substrate 111. The configuration of the chip 110 will be described in detail later.

[0017] The first film 120 is a flexible film that can accommodate the chip 110. The first film 120 includes, for example, a film portion 121, a cavity 122, a conductive portion 123, an electrode 124, and a support plate 125.

[0018] The film portion 121 is made of an insulating material such as polyimide, and is a flexible film having a thickness of, for example, about 400 μm so as to obtain the required flexibility and strength.

[0019] The cavity 122 is a space capable of accommodating the chip 110 provided on one surface of the film part 121. That is, the cavity 122 has a depth (e.g., 300 μm) that is approximately the same as the thickness (e.g., 300 μm) of the chip 110. Note that the position where the cavity 122 is provided within the one surface is not limited.

[0020] The conductive portions 123 are formed of a conductive material such as copper foil and are configured as a pair of wiring patterns. Each of the conductive portions 123 is provided, for example, so that one end is exposed at the bottom of the cavity 122 and the other end is electrically connected to the electrode 124. Specifically, the conductive portions 123 are provided so that at least a portion of the conductive portions 123 is exposed within the cavity 122 so that the conductive portions 123 and the electrodes 115 of the chip 110 are electrically connected when the chip 110 is housed in the cavity 122.

[0021] The electrodes 124 are formed of a conductive material such as copper foil and are configured as a pair of wiring patterns. Each of the electrodes 124 is electrically connected to a corresponding one of the electrodes 115 of the chip 110 and is an electrode for outputting a thermoelectric signal to a predetermined device. Each of the electrodes 124 is electrically connected to a corresponding one of the conductive portions 123 and is provided so as to be exposed on one surface of the film portion 121.

[0022] The support plate 125 is, for example, a member that supports the electrode 124. The support plate 125 is provided on the surface of the first film 120 opposite to the surface of the first film 120 on which the electrode 124 is provided. The support plate 125 is provided so as to overlap at least the electrode 124 in a planar view, and preferably is provided so as to overlap the electrode 124 and a portion of the second film 130 bonded to the first film 120 in a planar view. The support plate 125 is formed, for example, from a resin material. This makes it possible to prevent deformation that may occur in the temperature sensor 100 due to pressure applied to the electrode 124, which is electrically connected to an external device.

[0023] The second film 130 is a flexible film capable of transmitting the heat flow of the measurement object to the chip 110. Specifically, one side of the second film 130 contacts the measurement object and receives the heat flow, and the other side is bonded to the chip 110 and transmits the heat from the measurement object to the chip 110. The second film 130 has the required flexibility and strength and is formed with a thickness that does not increase thermal resistance, preferably a thickness of 50 μm or less. The second film 130 may be made of either an insulating material or a conductive material. The second film 130 is bonded to one side of the film portion 121 with the chip 110 housed in the cavity 122 of the first film 120. As a result, one side of the chip 110 is in close contact with the second film 130, and heat from the measurement object is transmitted to the chip 110 via the second film 130. Here, the temperature sensor 100 is configured so that the electrodes 124 are exposed with the second film 130 bonded to the film portion 121 .

[0024] In this way, the temperature sensor 100 has a structure in which the chip 110, which is a small MEMS element, is sealed with a flexible film, so that the chip 110 comes into point contact with the curved surface of the object to be measured, and therefore can be appropriately installed under a variety of installation conditions. Furthermore, the temperature sensor 100 is also capable of measuring the temperature difference between two objects to be measured, because the chip 110, which includes the membrane cavity 112, which has low mechanical strength, is protected on its entire periphery by the cavity 122 of the first film 120 and the second film 130.

[0025] The area of ​​the main surfaces of the temperature sensor 100 may be changed to correspond to the size of the object to be measured. For example, as shown in FIG. 2, the temperature sensor 100a has the same size as the chip 110, but the areas of the main surfaces of the first film 120 and the second film 130 are increased. The chip 110 shown in FIG. 2 is the same size as the chip 110 shown in FIG. 1. As shown in FIG. 2, the temperature sensor 110a is configured such that the areas of the main surfaces of the first film 120a and the second film 130a are larger than those of the first film 120 and the second film 130, compared to the temperature sensor 100 shown in FIG. 1. Since the temperature sensor 100a measures the temperature difference using the chip 110, which is a MEMS-type element, even if the area of ​​the film housing the chip 110 is increased, the sensitivity of the temperature sensor does not change. In other words, by configuring the temperature sensor 100a to be sealed in a flexible film, it can be easily sized and shaped appropriately for the size and shape of the object to be measured.

[0026] The temperature sensor 100 may also be configured to include multiple chips 110. For example, as shown in FIGS. 3 and 4(a), the temperature sensor 100b has multiple chips 110b connected in series. This allows the temperature sensor 100b to measure temperature with higher accuracy than the temperature sensor 100. Specifically, the temperature sensor 100b has multiple cavities 122b on one surface of the first film 120b, each capable of accommodating one of the chips 110b1 to 110b3. The bottoms of the multiple cavities 122b are provided so that the conductive portions 123b of the chips 110b1 to 110b3 are exposed. As shown in Figures 3 and 4(a), in temperature sensor 100b, one electrode of first chip 110b1 is electrically connected to one electrode 124b1 of first film 120b, first chip 110b1, second chip 110b2 and third chip 110b3 are connected in series, and the other electrode of third chip 110b3 is electrically connected to the other electrode 124b2 of first film 120b.

[0027] Furthermore, for example, as shown in FIG. 4B , the temperature sensor 100c may be configured with multiple chips 110 connected in parallel. In other words, the temperature sensor 100c may be configured with multiple chips 110 individually provided. Specifically, the temperature sensor 100c includes multiple cavities on one surface of the first film 120, each capable of accommodating one of the multiple chips 110. The bottom of each of the multiple cavities is provided so that the conductive portions 123 of the multiple chips 110 are exposed. As shown in FIG. 4B , the multiple chips 110 are connected in parallel so that one electrode of each of the multiple chips 110 is connected to a reference potential and a thermoelectric signal is output from the other electrode. In this way, by connecting the multiple chips 110 in parallel to a flexible film, the temperature sensor 100c is able to accurately measure the in-plane distribution of the measurement object while appropriately contacting the measurement object according to its shape.

[0028] Furthermore, the temperature sensor 100c can output the results of measuring the temperature difference within the surface of the second film 130 of the temperature sensor 100 using multiple chips 110, and by analyzing the results using a control unit (not shown), the contact state of the temperature sensor 100c with the object to be measured can be identified.

[0029] As described above, the temperature sensor 100 can accommodate multiple chips 110 in a flexible film, and therefore the shape, size, number of chips 110, placement position of the chips 110, and wiring method of each of the multiple chips 110 can be adjusted, making it possible to easily and inexpensively provide an optimal temperature sensor depending on conditions such as the shape and size of the object to be measured.

[0030] <<Chip 110>> An example of the configuration of the chip 110 will be described in detail with reference to Fig. 5. Fig. 5 is a diagram showing an example of the configuration of the chip 110. Fig. 5(a) is a plan view showing an example of a simplified appearance of the chip 110. Fig. 5(b) is a cross-sectional view showing a cross section of the chip 110 taken along line A-A in Fig. 5(a).

[0031] As shown in FIG. 5, the chip 110 includes a silicon substrate 111 , a membrane cavity 112 , an insulating film 113 , a thermopile 114 , and an electrode 115 .

[0032] The silicon substrate 111 is a silicon single crystal substrate having a thickness of, for example, 300 μm.

[0033] The membrane cavity 112 is a cavity formed by anisotropic etching in the center of the silicon substrate 111. The membrane cavity 112 is, for example, a space that slopes toward the center of the silicon substrate 111. Note that while Fig. 5 shows a structure etched from the front surface of the silicon substrate 111, the cavity may be etched from the back surface of the silicon substrate 111 to penetrate the silicon substrate 111.

[0034] The insulating film 113 is an insulating film formed by laminating an insulating film made of silicon dioxide and having a thickness of, for example, 100 to 500 nm, and an insulating film made of silicon nitride and having a thickness of, for example, 100 to 500 nm.

[0035] The thermopile 114 is composed of, for example, a thermoelectric thin film 114a and lead portions 114b. The thermoelectric thin film 114a is made of a material with a large Seebeck coefficient, for example, n-type polycrystalline silicon Si1 and p-type polycrystalline silicon Si2. The thermoelectric thin film 114a is configured so that the n-type polycrystalline silicon Si1 and the p-type polycrystalline silicon Si2 overlap in a planar view (Z direction in FIG. 5 ). The thermopile 114 is formed by, for example, repeatedly forming layers by chemical vapor deposition and sputtering, and patterning the silicon substrate 111 by photolithography, thereby forming the thermoelectric thin film 114a and lead portions 114b.

[0036] The lead portion 114b may be made of, for example, aluminum, with a thickness of 500 to 1000 nm and a line width of 5 to 50 μm.

[0037] The thermoelectric thin film 114a is arranged so that one end overlaps the membrane cavity 112 in a plan view (viewed from the Z direction in FIG. 5 , which is the up-down direction), and the other end overlaps the silicon substrate 111 in a plan view. That is, in a plan view, the thermoelectric thin film 114a has one end overlapping the membrane cavity 112 (for example, the end that receives heat from the object to be measured) and the other end overlapping the silicon substrate 111 (for example, the end that receives heat from the silicon substrate 111). The other ends of the multiple thermoelectric thin films 114a are connected in series via lead portions 114b.

[0038] The electrode 115 is an electrode provided at the end of the lead portion 114b that electrically connects the multiple thermoelectric thin films 114a. The electrode 115 is electrically connected to the conductive portion 123 of the first film 120. The chip 110 outputs a thermoelectric signal from the electrode 115 to the outside.

[0039] Although the above description has been given of the chip 110 having a single stage of thermoelectric thin film 114a, the present invention is not limited to this and may have multiple stages of thermoelectric thin film 114a in the Z direction, for example. This allows the temperature sensor 100 to measure temperature (heat flow) with higher sensitivity.

[0040] Furthermore, although the above description has been given of the membrane cavity 112 of the chip 110 being hollow, this is not limiting, and for example, the cavity of the membrane cavity 112 may be filled with a material with low heat capacity and low thermal conductivity (such as polyimide), which allows the chip 110 to physically withstand the pressure (pressure in the Z direction) applied toward the first film 120 when it is sealed in the cavity 122.

[0041] 6 and 7, an example of a method for manufacturing the temperature sensor 100 will be described. Fig. 6 is a flowchart of the method for manufacturing the temperature sensor 100. Fig. 7 is a schematic diagram showing the assembly of the components of the temperature sensor 100.

[0042] In step S100, a chip 110 for measuring the temperature difference between the front and rear surfaces using a thermopile 114 is prepared.

[0043] In step S101, as shown in FIG. 7(a), a first film 120 having a cavity 122 and a conductive portion 123 electrically connected to an electrode 124 (not shown) is exposed at the bottom of the cavity 122 (inside the cavity 122) is placed in a predetermined position.

[0044] 7B, in step S102, the chip 110 is accommodated in the cavity 122 so that a portion of the conductive portion 123 exposed at the bottom of the cavity 122 of the first film 120 is in electrical contact with the electrode 115 of the chip 110. At this time, a conductive member 140 may be disposed between the electrode 115 of the chip 110 and the conductive portion 123 in the cavity 122.

[0045] The conductive member 140 is a conductive material, such as an anisotropic conductive sheet, that can electrically connect the conductive portion 123 and the chip electrode 115. This allows the temperature sensor 100 to be configured without exposing the conductive path for electrically connecting the electrode 115 of the chip 110 and the conductive portion 123 to the outside, making the temperature sensor 100 independent of the environment in which it is installed.

[0046] 7(c), in step S103, the chip 110 is placed in the cavity 122, and pressure is applied in the Z direction to ensure electrical continuity between the electrodes 115 of the chip 110 and the conductive portions 123 of the first film 120. Here, the chip 110 may be formed by filling the cavity of the membrane cavity 112 with a material with a low heat capacity, such as polyimide. This makes it possible to reduce damage to the chip 110, such as deformation of the chip 110, when pressure is applied in the Z direction in step S103.

[0047] 7(d), after the chip 110 is accommodated in the cavity 122, the second film 130 is bonded to the main surface of the first film 120 where the cavity 122 is provided, thereby completing the temperature sensor 100. In this temperature sensor 100, the exposed outer surface of the second film 130 is the surface that comes into contact with the object to be measured.

[0048] Summary <1> The temperature sensor 100 comprises: a chip 110 having a thermopile 114 and an electrode 115 (first conductive portion) for outputting a thermoelectric signal generated by the thermopile 114; a flexible first film 120 having a cavity 122 provided on one side thereof that can accommodate the chip 110; a conductive portion 123 (second conductive portion) at least a portion of which is provided within the cavity 122 and electrically connected to the electrode 115 (first conductive portion) when the chip 110 is accommodated in the cavity 122; and an electrode 124 that is electrically connected to the conductive portion 123 (second conductive portion) for outputting a thermoelectric signal to a predetermined device; and a flexible second film 130 that is bonded to one side of the first film 120 so as to seal the chip 110. As a result, the chip 110 is embedded in flexible films 120 and 130, so that even if the object to be measured has a curved surface, the chip 110 will come into point contact, allowing it to be installed appropriately under a variety of installation conditions.

[0049] <2> The temperature sensor 100 further includes a conductive member 140 provided within the cavity 122 between the conductive portion 123 (second conductive portion) of the first film 120 and the electrode 115 (first conductive portion) of the chip 110. This allows the temperature sensor 100 to be configured without exposing the conductive path for electrically connecting the electrode 115 of the chip 110 and the conductive portion 123 to the outside, and therefore is not dependent on the environment in which the temperature sensor 100 is installed.

[0050] <3> The chip 110 in the temperature sensor 100 includes a silicon substrate 111 provided with a membrane cavity 112 (cavity), and a thermopile 114. One end of the thermopile 114 is arranged to overlap the membrane cavity 112 (cavity) in a plan view, and the other end is arranged to overlap the silicon substrate 111 in a plan view. This enables the temperature sensor 100 to measure temperature with high accuracy.

[0051] <4> The temperature sensor according to any one of <1> to <3>, wherein the membrane cavity 112 (cavity) in the temperature sensor 100 is filled with a material having a lower heat capacity and thermal conductivity than the silicon substrate 111. This allows the chip 110 in the temperature sensor 100 to physically withstand pressure in the vertical direction (Z direction) applied to the chip 110 when the chip 110 is sealed in the cavity 122.

[0052] <5> The temperature sensor according to any one of <1> to <4>, wherein the temperature sensors 100b and 100c have a first chip and a second chip electrically connected to the first chip as the chip 110. This enables the temperature sensor 100b to measure temperature with higher accuracy than the temperature sensor 100.

[0053] <6> The first chip 110b1 of the temperature sensor 100b is connected in series with the second chip 110b2. This allows the temperature sensor 100b to measure temperature with higher accuracy than the temperature sensor 100.

[0054] <7> The first chip 110 in the temperature sensor 100c is connected in parallel with the second chip 110. As a result, the temperature sensor 100c has multiple chips 110 independently provided on a flexible film, which allows the temperature sensor 100c to accurately measure the in-plane distribution of the object to be measured while making appropriate contact according to the shape of the object to be measured.

[0055] <8> The method for manufacturing the temperature sensor 100 includes the steps of: arranging, at a predetermined position, a flexible first film 120 having a cavity 122, an electrode 124 (first electrode), and a conductive portion 123 (conductive path) provided on one surface thereof, the conductive portion 123 being provided between the cavity 122 and the electrode 124 (first electrode); and arranging a conductive member 140 in the cavity 122 so as to be in electrical contact with a portion of the conductive portion 123 (conductive path) exposed in the cavity 122. The method includes the steps of placing a chip 110 including a thermopile 114 and an electrode 115 (second electrode) for outputting a thermoelectric signal generated by the thermopile 114 in the cavity 122 so that the electrode 115 (second electrode) is electrically connected to the conductive member 140, and bonding a flexible second film 130 made of an insulating material to one surface of the first film 120 so as to seal the chip 110. This structure embeds the chip 110 in the flexible films 120 and 130, so that the chip 110 makes point contact with the object to be measured even when the object has a curved surface, allowing it to be appropriately installed under various installation conditions. Furthermore, the temperature sensor 100 can be configured without exposing the conductive path for electrically connecting the electrode 115 of the chip 110 to the conductive portion 123.

[0056] The embodiments described through the above embodiments of the invention can be combined, modified, or improved as appropriate depending on the application, and the present invention is not limited to the above-described embodiments. It is clear from the claims that such combinations, modifications, or improvements are also included within the technical scope of the present invention.

[0057] 100...temperature sensor, 110...chip, 111...silicon substrate, 112...membrane cavity portion, 113...insulating film, 114...thermopile, 115...electrode, 120...first film, 130...second film, 121...film portion, 122...cavity, 123...conductive portion, 124...electrode, 125...support plate, 130...second film, 140...conductive member.

Claims

1. A chip comprising a thermopile and a first conductive part for outputting a pyroelectric signal generated by the thermopile; a first flexible film having a cavity provided on one surface thereof for accommodating the chip; a second conductive part provided at least partially in the cavity and electrically connected to the first conductive part in a state where the chip is accommodated in the cavity; and an electrode for outputting the pyroelectric signal to a predetermined device and electrically connected to the second conductive part; a first flexible film; and a second flexible film having flexibility and joined to the one surface of the first flexible film so as to seal the chip.

2. The temperature sensor according to claim 1, further comprising an anisotropic conductive sheet provided between the second conductive part of the first flexible film and the first conductive part of the chip in the cavity for electrically connecting the first conductive part and the second conductive part.

3. The temperature sensor according to claim 1 or 2, wherein the chip includes a silicon substrate provided with a cavity portion and the thermopile, and one end of the thermopile is arranged so as to overlap the cavity portion in plan view, and the other end is arranged so as to overlap the silicon substrate in plan view.

4. The temperature sensor according to claim 3, wherein the cavity portion is filled with a material having a smaller heat capacity and heat conduction than the silicon substrate.

5. The temperature sensor according to claim 1, having a first chip and a second chip as the chip.

6. The temperature sensor according to claim 5, wherein the first chip is connected in series with the second chip.

7. The temperature sensor according to claim 5, wherein the first chip is connected in parallel with the second chip. Step of disposing a flexible first film provided with a cavity, a first electrode, and a conductive path provided between the cavity and the first electrode on one surface at a predetermined position; Step of disposing a conductive member in the cavity so as to be in electrical contact with a part of the conductive path exposed in the cavity; Step of disposing a chip including a thermopile having a thermopile and a second electrode for outputting a thermoelectric signal generated by the thermopile in the cavity such that the second electrode and the conductive member are electrically connected; Step of joining a flexible second film formed of an insulating material to the one surface of the first film so as to seal the chip, the method for manufacturing a temperature sensor including these steps.

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