Sensor module, battery pack

Abstract

To provide a sensor module capable of detecting the state of a battery with high accuracy.SOLUTION: A sensor module includes a metallic elastic body that is adhered to the outer surface of a housing that contains a battery, and a strain gauge provided on one side of the elastic body, the other side of the elastic body has a plurality of spaced-apart adhesive areas that are adhered to the housing, the strain gauge is positioned in an area of the one side of the elastic body that does not face the adhesive areas, and the resistor of the strain gauge is formed from a material containing at least one of chromium and nickel.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a sensor module and a battery pack.

Background Art

[0002] In a battery pack used for mobile devices or the like, the battery may expand due to a decrease in the life of the battery in the battery pack, causing liquid leakage or the like. Therefore, in a battery pack, it is important to detect the expansion of the battery, and various devices for detecting the expansion of the battery have been proposed.

[0003] As an example, there is a device that detects the internal pressure with a strain gauge disposed in the inner space of a lithium secondary battery and displays the detected internal pressure on a display. With this device, it is possible to determine whether the lithium secondary battery is normal or abnormal by monitoring the displayed internal pressure (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, since the strain caused by the expansion of the battery is small, it has been difficult to accurately detect with the conventionally proposed devices.

[0006] The present invention has been made in view of the above points, and an object thereof is to provide a sensor module capable of accurately detecting the state of a battery.

Means for Solving the Problems

[0007] This sensor module has a metal strain body adhered to the outer surface of a housing that houses a battery, and a strain gauge provided on one surface of the strain body. On the other surface of the strain body, a plurality of adhesive regions that are adhered to the housing and are spaced apart from each other are defined. The strain gauge is disposed in a region that does not face the adhesive region on one surface of the strain body, and the resistor of the strain gauge is formed of a material containing at least one of chromium and nickel.

Advantages of the Invention

[0008] According to the disclosed technology, it is possible to provide a sensor module capable of accurately detecting the state of a battery.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings. In each drawing, the same reference numerals are assigned to the same components, and redundant descriptions may be omitted.

[0011] In addition, in each of the following embodiments and modification examples, an example of detecting the swelling of the battery is mainly shown, but the present invention is not limited thereto, and the sensor module according to each embodiment can detect various states of the battery. Various states of the battery include, for example, contraction of the battery, presence or absence of convex portions and concave portions, shape distribution, temperature, etc., in addition to the swelling of the battery.

[0012] <First Embodiment> FIG. 1 is a plan view illustrating a battery pack according to the first embodiment. FIG. 2 is a cross-sectional view illustrating the battery pack according to the first embodiment, showing a cross-section along line A-A in FIG. 1.

[0013] Referring to FIGS. 1 and 2, the battery pack 1 has a housing 10, a sensor module 20, and adhesive layers 31 and 32. The battery pack 1 is a battery pack in which the sensor module 20 is adhered to the outer surface of the housing 10 that houses the battery, and can be widely used in various electronic devices such as personal computers and smartphones, and portable terminals.

[0014] The housing 10 is a case that houses the battery and is formed of, for example, metal or resin. Inside the housing 10, members other than the battery, such as a circuit board and external output terminals, may be housed. The battery housed in the housing 10 is, for example, a secondary battery such as a lithium ion battery, and a plurality of batteries are housed by being connected in parallel and / or in series as appropriate.

[0015] The sensor module 20 is a sensor that detects deformation of the housing 10 due to swelling of the battery. The sensor module 20 has a strain generating body 50 and a strain gauge 100 disposed on one surface of the strain generating body 50 via an adhesive layer 70.

[0016] The strain generating body 50 is rectangular in plan view and bent in an L shape in cross-sectional view. The strain gauge 100 is provided via the adhesive layer 70 in the vicinity of the bent portion where the long side and the short side of the L shape are connected on the upper surface of the long side of the L shape of the strain generating body 50. In other words, the strain gauge 100 is disposed above the corner where the upper surface and the side surface of the housing 10 are connected.

[0017] The material of the adhesive layer 70 is not particularly limited and can be appropriately selected according to the purpose. For example, epoxy resin, modified epoxy resin, silicone resin, modified silicone resin, urethane resin, modified urethane resin, etc. can be used. Also, a double-sided tape can be used as the adhesive layer 70. The thickness of the adhesive layer 70 is not particularly limited and can be appropriately selected according to the purpose. For example, it can be about 0.1 μm to 50 μm.

[0018] On the lower surface of the strain generating body 50, a plurality of spaced-apart adhesive regions that are adhered to the housing 10 are defined. In the example of FIG. 2, one adhesive region is defined at each of the end portions of the long side and the short side of the L-shape. An adhesive layer 31 is provided in the adhesive region on the long side, and an adhesive layer 32 is provided in the adhesive region on the short side. In the strain generating body 50, the bent portion of the L-shape is a non-adhesive region that is not adhered to the housing 10.

[0019] The long side of the L-shape of the strain generating body 50 is adhered to the upper surface of the housing 10 via the adhesive layer 31, and the short side of the L-shape of the strain generating body 50 is adhered to the side surface of the housing 10 via the adhesive layer 32. The adhesive layers 31 and 32 can be the same as, for example, the adhesive layer 70.

[0020] On the opposite side (the housing 10 side) of the region where the strain gauge 100 of the strain generating body 50 is disposed, no adhesive layer is disposed, and a space S is provided. In other words, the strain gauge 100 is disposed in a region that does not face the adhesive region on the upper surface of the strain generating body 50. By providing the space S, the strain generating body 50 can easily expand and contract as the housing 10 deforms due to the expansion of the battery. Therefore, the change in the resistance value of the strain gauge 100 becomes large, and the deformation of the housing 10 can be detected with high sensitivity.

[0021] The distortion body 50 is made of metal. As the material of the distortion body 50, for example, SUS (stainless steel), Al, Fe, etc. can be used. Among these, it is preferable to use SUS in terms of the point of lowering the height and the ease of correcting the strain gauge for the distortion body. The thickness of the distortion body 50 can be, for example, about 0.05 mm or more and 0.2 mm or less. By setting the thickness of the distortion body 50 to 0.05 mm or more, the necessary rigidity can be obtained and the space S can be secured. By setting the thickness of the distortion body 50 to 0.2 mm or less, the distortion body 50 can expand and contract sufficiently.

[0022] FIG. 3 is a cross-sectional view (part 1) illustrating the state in which the housing is deformed due to the expansion of the battery. As shown in FIG. 3, for example, when gas is generated inside the battery disposed in the housing 10, the battery expands, the central portions of the upper and lower surfaces of the housing 10 bulge, and the corner portions also deform. Then, strain occurs in the central portion and the corner portions of the housing 10.

[0023] In FIG. 3, it can be seen that the distortion body 50 is also deformed as the housing 10 is deformed due to the expansion of the battery. Thereby, the resistance value of the strain gauge 100 changes, and the deformation of the housing 10 can be detected. That is, the expansion of the battery housed inside the housing 10 can be detected.

[0024] In this way, when the distortion body 50 is adhered to the housing 10, by providing a space S between the lower surface of the distortion body 50 and the housing 10 and arranging the strain gauge 100 on the space S which is a region not facing the adhesion region on the upper surface of the distortion body 50, the deformation of the housing 10 due to the expansion of the battery can be detected with high sensitivity.

[0025] Here, the strain gauge 100 will be described.

[0026] FIG. 4 is a plan view illustrating a strain gauge according to the first embodiment. FIG. 5 is a cross-sectional view illustrating the strain gauge according to the first embodiment, showing a cross-section along line B-B in FIG. 4. Referring to FIGS. 4 and 5, the strain gauge 100 includes a base material 110, a resistor 130, a wiring 140, an electrode 150, and a cover layer 160. In FIG. 4, for convenience, only the outer edge of the cover layer 160 is shown by a dashed line. Note that the cover layer 160 may be provided as necessary.

[0027] The base material 110 is a member serving as a base layer for forming the resistor 130 and the like, and has flexibility. The thickness of the base material 110 is not particularly limited and can be appropriately selected according to the purpose. For example, it can be about 5 μm to 500 μm. In particular, when the thickness of the base material 110 is 5 μm to 200 μm, it is preferable in terms of the transmission of strain from the surface of the strained body joined to the lower surface of the base material 110 via an adhesive layer or the like and the dimensional stability against the environment. When it is 10 μm or more, it is more preferable in terms of insulation.

[0028] The base material 110 can be formed from an insulating resin film such as a PI (polyimide) resin, an epoxy resin, a PEEK (polyetheretherketone) resin, a PEN (polyethylene naphthalate) resin, a PET (polyethylene terephthalate) resin, a PPS (polyphenylene sulfide) resin, an LCP (liquid crystal polymer) resin, or a polyolefin resin. Note that a film refers to a member having a thickness of about 500 μm or less and having flexibility.

[0029] Here, "formed from an insulating resin film" does not prevent the base material 110 from containing fillers, impurities, or the like in the insulating resin film. The base material 110 may be formed from an insulating resin film containing fillers such as silica or alumina.

[0030] Examples of materials other than the resin of the base material 110 include crystalline materials such as SiO2, ZrO2 (including YSZ), Si, Si2N3, Al2O3 (including sapphire), ZnO, perovskite-based ceramics (CaTiO3, BaTiO3), etc., and in addition, amorphous glass, etc. may be mentioned. Further, as the material of the base material 110, metals such as aluminum, aluminum alloy (duralumin), and titanium may be used. In this case, for example, an insulating film is formed on the metal base material 110.

[0031] The resistor 130 is a thin film formed on the base material 110 in a predetermined pattern, and is a sensing portion that undergoes strain and causes a resistance change. The resistor 130 may be formed directly on the upper surface 110a of the base material 110, or may be formed on the upper surface 110a of the base material 110 via another layer. In FIG. 4, for convenience, the resistor 130 is shown as a dark embossed pattern.

[0032] The resistor 130 has a structure in which a plurality of elongated portions are arranged at a predetermined interval with their longitudinal directions facing the same direction (the direction of line B-B in FIG. 4), and the ends of adjacent elongated portions are alternately connected to form a zigzag fold as a whole. The longitudinal direction of the plurality of elongated portions becomes the grid direction, and the direction perpendicular to the grid direction becomes the grid width direction (the direction perpendicular to line B-B in FIG. 4).

[0033] One end portion in the longitudinal direction of the two outermost elongated portions in the grid width direction is bent in the grid width direction to form respective ends 130e1 and 130e2 of the resistor 130 in the grid width direction. The respective ends 130e1 and 130e2 of the resistor 130 in the grid width direction are electrically connected to the electrodes 150 via the wirings 140. In other words, the wirings 140 electrically connect the respective ends 130e1 and 130e2 of the resistor 130 in the grid width direction to the respective electrodes 150.

[0034] The resistor 130 can be formed of, for example, a material containing Cr (chromium), a material containing Ni (nickel), or a material containing both Cr and Ni. That is, the resistor 130 can be formed of a material containing at least one of Cr and Ni. Examples of the material containing Cr include a Cr mixed-phase film. Examples of the material containing Ni include Cu-Ni (copper nickel). Examples of the material containing both Cr and Ni include Ni-Cr (nickel chromium).

[0035] Here, the Cr mixed-phase film is a film in which Cr, CrN, Cr2N, etc. are in a mixed phase. The Cr mixed-phase film may contain inevitable impurities such as chromium oxide.

[0036] The thickness of the resistor 130 is not particularly limited and can be appropriately selected according to the purpose. For example, it can be about 0.05 μm to 2 μm. In particular, when the thickness of the resistor 130 is 0.1 μm or more, it is preferable in that the crystallinity of the crystals constituting the resistor 130 (for example, the crystallinity of α-Cr) is improved. Further, when the thickness of the resistor 130 is 1 μm or less, it is more preferable in that cracks in the film due to internal stress of the film constituting the resistor 130 and warping from the base material 110 can be reduced. The width of the resistor 130 can be optimized according to the required specifications such as the resistance value and lateral sensitivity, and considering measures against disconnection, for example, it can be about 10 μm to 100 μm.

[0037] For example, when the resistor 130 is a Cr mixed-phase film, the stability of the gauge characteristics can be improved by using α-Cr (alpha chromium), which is a stable crystal phase, as the main component. Further, when the resistor 130 has α-Cr as the main component, the gauge factor of the strain gauge 100 can be 10 or more, and the gauge factor temperature coefficient TCS and the resistance temperature coefficient TCR can be in the range of -1000 ppm / °C to +1000 ppm / °C. Here, the main component means that the target substance occupies 50% by weight or more of all the substances constituting the resistor. From the viewpoint of improving the gauge characteristics, the resistor 130 preferably contains 80% by weight or more of α-Cr, and more preferably 90% by weight or more. Note that α-Cr is Cr having a bcc structure (body-centered cubic lattice structure).

[0038] Further, when the resistor 130 is a Cr mixed-phase film, it is preferable that CrN and Cr2N contained in the Cr mixed-phase film are 20% by weight or less. By having CrN and Cr2N contained in the Cr mixed-phase film be 20% by weight or less, a decrease in the gauge factor can be suppressed.

[0039] Also, the ratio of Cr2N in CrN and Cr2N is preferably 80% by weight or more and less than 90% by weight, and more preferably 90% by weight or more and less than 95% by weight. By having the ratio of Cr2N in CrN and Cr2N be 90% by weight or more and less than 95% by weight, due to Cr2N having semiconductor-like properties, a decrease in TCR (negative TCR) becomes more prominent. Furthermore, by reducing ceramization, brittle fracture is reduced.

[0040] On the other hand, when a small amount of N2 or atomic N is mixed and present in the film, due to them escaping outside the film by an external environment (for example, under a high-temperature environment), a change in film stress occurs. By creating chemically stable CrN, the generation of the above-mentioned unstable N can be avoided, and a stable strain gauge can be obtained.

[0041] The wiring 140 is formed on the base material 110 and is electrically connected to the resistor 130 and the electrode 150. The wiring 140 has a first metal layer 141 and a second metal layer 142 laminated on the upper surface of the first metal layer 141. The wiring 140 is not limited to a linear shape and can have any pattern. Also, the wiring 140 can have any width and any length. In FIG. 4, for the sake of convenience, the wiring 140 and the electrode 150 are shown in a matte pattern thinner than the resistor 130.

[0042] The electrode 150 is formed on the base material 110 and is electrically connected to the resistor 130 via the wiring 140. For example, it is formed in a substantially rectangular shape with a width wider than that of the wiring 140. The electrode 150 is a pair of electrodes for outputting to the outside the change in the resistance value of the resistor 130 caused by strain. For example, lead wires for external connection, flexible substrates, etc. are joined thereto. The base material 110 and the wiring 140 may be extended so that the electrode 150 is positioned at the end of the strain generating body 50. Thereby, the electrical connection between the electrode 150 and the outside becomes easy.

[0043] The electrode 150 has a pair of first metal layers 151 and second metal layers 152 laminated on the upper surfaces of the respective first metal layers 151. The first metal layer 151 is electrically connected to the terminals 130e1 and 130e2 of the resistor 130 via the first metal layer 141 of the wiring 140. The first metal layer 151 is formed in a substantially rectangular shape in plan view. The first metal layer 151 may be formed with the same width as the wiring 140.

[0044] Note that although the resistor 130, the first metal layer 141, and the first metal layer 151 are given different reference numerals for convenience, they can be integrally formed of the same material in the same process. Therefore, the resistor 130, the first metal layer 141, and the first metal layer 151 have substantially the same thickness. Also, although the second metal layer 142 and the second metal layer 152 are given different reference numerals for convenience, they can be integrally formed of the same material in the same process. Therefore, the second metal layer 142 and the second metal layer 152 have substantially the same thickness.

[0045] The second metal layers 142 and 152 are formed of a material having a lower resistance than the resistor 130 (the first metal layers 141 and 151). The material of the second metal layers 142 and 152 is not particularly limited as long as it has a lower resistance than the resistor 130, and can be appropriately selected according to the purpose. For example, when the resistor 130 is a Cr mixed-phase film, the materials of the second metal layers 142 and 152 include Cu, Ni, Al, Ag, Au, Pt, etc., or alloys of any of these metals, compounds of any of these metals, or laminated films obtained by appropriately laminating any of these metals, alloys, and compounds. The thicknesses of the second metal layers 142 and 152 are not particularly limited and can be appropriately selected according to the purpose. For example, they can be about 3 μm to 5 μm.

[0046] The second metal layers 142 and 152 may be formed on a part of the upper surfaces of the first metal layers 141 and 151, or may be formed on the entire upper surfaces of the first metal layers 141 and 151. One or more other metal layers may be further laminated on the upper surface of the second metal layer 152. For example, the second metal layer 152 may be a copper layer, and a gold layer may be laminated on the upper surface of the copper layer. Alternatively, the second metal layer 152 may be a copper layer, and a palladium layer and a gold layer may be sequentially laminated on the upper surface of the copper layer. By making the uppermost layer of the electrode 150 a gold layer, the solder wetting property of the electrode 150 can be improved.

[0047] Thus, the wiring 140 has a structure in which the second metal layer 142 is laminated on the first metal layer 141 made of the same material as the resistor 130. Therefore, the resistance of the wiring 140 is lower than that of the resistor 130, so that it can be suppressed that the wiring 140 functions as a resistor. As a result, the strain detection accuracy by the resistor 130 can be improved.

[0048] In other words, by providing the wiring 140 having a lower resistance than the resistor 130, the substantial sensing part of the strain gauge 100 can be limited to the local region where the resistor 130 is formed. Therefore, the strain detection accuracy by the resistor 130 can be improved.

[0049] In particular, in a highly sensitive strain gauge with a gauge factor of 10 or more using a Cr mixed-phase film as the resistor 130, reducing the resistance of the wiring 140 to be lower than that of the resistor 130 and restricting the substantial sensing portion to the local region where the resistor 130 is formed exhibits a remarkable effect in improving the strain detection accuracy. Further, reducing the resistance of the wiring 140 to be lower than that of the resistor 130 also has the effect of reducing the cross sensitivity.

[0050] The cover layer 160 is formed on the base material 110, covers the resistor 130 and the wiring 140, and exposes the electrode 150. A part of the wiring 140 may be exposed from the cover layer 160. By providing the cover layer 160 that covers the resistor 130 and the wiring 140, it is possible to prevent mechanical damage or the like from occurring in the resistor 130 and the wiring 140. Further, by providing the cover layer 160, the resistor 130 and the wiring 140 can be protected from moisture or the like. Note that the cover layer 160 may be provided so as to cover the entire portion except the electrode 150.

[0051] The cover layer 160 can be formed from an insulating resin such as a PI resin, an epoxy resin, a PEEK resin, a PEN resin, a PET resin, a PPS resin, a composite resin (for example, a silicone resin, a polyolefin resin), etc. The cover layer 160 may contain a filler or a pigment. The thickness of the cover layer 160 is not particularly limited and can be appropriately selected according to the purpose, but can be, for example, about 2 μm to 30 μm.

[0052] To manufacture the strain gauge 100, first, the base material 110 is prepared, and a metal layer (for convenience, referred to as metal layer A) is formed on the upper surface 110a of the base material 110. The metal layer A is a layer that is finally patterned into the resistor 130, the first metal layer 141, and the first metal layer 151. Therefore, the material and thickness of the metal layer A are the same as those of the aforementioned resistor 130, first metal layer 141, and first metal layer 151.

[0053] The metal layer A can be formed, for example, by magnetron sputtering using a raw material capable of forming the metal layer A as a target. Instead of the magnetron sputtering method, the metal layer A may be formed using a reactive sputtering method, an evaporation method, an arc ion plating method, a pulsed laser deposition method, or the like.

[0054] From the viewpoint of stabilizing the gauge characteristics, before forming the metal layer A, it is preferable to vacuum deposit a functional layer with a predetermined film thickness on the upper surface 110a of the base material 110 as an underlayer by, for example, a conventional sputtering method.

[0055] In the present application, the functional layer refers to a layer having a function of promoting the crystal growth of at least the upper metal layer A (resistor 130). The functional layer preferably further has a function of preventing the oxidation of the metal layer A by oxygen or moisture contained in the base material 110 and a function of improving the adhesion between the base material 110 and the metal layer A. The functional layer may further have other functions.

[0056] Since the insulating resin film constituting the base material 110 contains oxygen and moisture, particularly when the metal layer A contains Cr, Cr forms a self-oxidized film, so it is effective for the functional layer to have a function of preventing the oxidation of the metal layer A.

[0057] The material of the functional layer is not particularly limited as long as it has a function of promoting the crystal growth of at least the upper metal layer A (resistor 130), and can be appropriately selected according to the purpose. For example, Cr (chromium), Ti (titanium), V (vanadium), Nb (niobium), Ta (tantalum), Ni (nickel), Y (yttrium), Zr (zirconium), Hf (hafnium), Si (silicon), C (carbon), Zn (zinc), Cu (copper), Bi (bismuth), Fe (iron), Mo (molybdenum), W (tungsten), Ru (ruthenium), Rh (rhodium), Re (rhenium), Os (osmium), Ir (iridium), Pt (platinum), Pd (palladium), Ag (silver), Au (gold), Co (cobalt), Mn (manganese), Al (aluminum), one or more metals selected from the group consisting of, an alloy of any metal in this group, or a compound of any metal in this group can be mentioned.

[0058] Examples of the above alloys include FeCr, TiAl, FeNi, NiCr, CrCu, etc. Examples of the above compounds include TiN, TaN, Si3N4, TiO2, Ta2O5, SiO2, etc.

[0059] When the functional layer is formed of a conductive material such as a metal or an alloy, the film thickness of the functional layer is preferably 1 / 20 or less of the film thickness of the resistor. In such a range, the crystal growth of α-Cr can be promoted, and at the same time, a part of the current flowing through the resistor can flow into the functional layer, preventing the detection sensitivity of strain from decreasing.

[0060] When the functional layer is formed of a conductive material such as a metal or an alloy, the film thickness of the functional layer is more preferably 1 / 50 or less of the film thickness of the resistor. In such a range, the crystal growth of α-Cr can be promoted, and at the same time, a part of the current flowing through the resistor can flow into the functional layer, further preventing the detection sensitivity of strain from decreasing.

[0061] When the functional layer is formed of a conductive material such as a metal or an alloy, it is more preferable that the film thickness of the functional layer is 1 / 100 or less of the film thickness of the resistor. When it is within such a range, a part of the current flowing through the resistor can flow into the functional layer, and it is possible to further prevent the detection sensitivity of strain from decreasing.

[0062] When the functional layer is formed of an insulating material such as an oxide or a nitride, the film thickness of the functional layer is preferably 1 nm to 1 μm. When it is within such a range, the crystal growth of α-Cr can be promoted, and the film can be easily formed without cracks in the functional layer.

[0063] When the functional layer is formed of an insulating material such as an oxide or a nitride, the film thickness of the functional layer is more preferably 1 nm to 0.8 μm. When it is within such a range, the crystal growth of α-Cr can be promoted, and the film can be formed more easily without cracks in the functional layer.

[0064] When the functional layer is formed of an insulating material such as an oxide or a nitride, the film thickness of the functional layer is still more preferably 1 nm to 0.5 μm. When it is within such a range, the crystal growth of α-Cr can be promoted, and the film can be formed even more easily without cracks in the functional layer.

[0065] Note that the planar shape of the functional layer is patterned to be substantially the same as the planar shape of the resistor shown in FIG. 4, for example. However, the planar shape of the functional layer is not limited to the case where it is substantially the same as the planar shape of the resistor. When the functional layer is formed of an insulating material, it does not have to be patterned into the same shape as the planar shape of the resistor. In this case, the functional layer may be formed in a solid shape at least in the region where the resistor is formed. Alternatively, the functional layer may be formed in a solid shape over the entire upper surface of the base material 110.

[0066] In addition, when the functional layer is formed of an insulating material, the functional layer is formed relatively thick so that its thickness is 50 nm or more and 1 μm or less, and is formed in a solid state. As a result, the thickness and surface area of the functional layer increase, and thus heat generated when the resistor generates heat can be dissipated to the substrate 110 side. As a result, in the strain gauge 100, it is possible to suppress a decrease in measurement accuracy due to self-heating of the resistor.

[0067] The functional layer can be formed by vacuum deposition, for example, by a conventional sputtering method in which a raw material capable of forming the functional layer is used as a target and Ar (argon) gas is introduced into the chamber. By using the conventional sputtering method, the functional layer is formed while etching the upper surface 110a of the substrate 110 with Ar, so that the deposition amount of the functional layer can be minimized and the adhesion improvement effect can be obtained.

[0068] However, this is an example of a method for forming the functional layer, and the functional layer may be formed by other methods. For example, before forming the functional layer, an adhesion improvement effect may be obtained by activating the upper surface 110a of the substrate 110 by plasma treatment using Ar or the like, and then a method of forming the functional layer by vacuum deposition by a magnetron sputtering method may be used.

[0069] The combination of the material of the functional layer and the material of the metal layer A is not particularly limited and can be appropriately selected according to the purpose. For example, Ti can be used as the functional layer, and a Cr mixed-phase film mainly composed of α-Cr (alpha chromium) can be formed as the metal layer A.

[0070] In this case, for example, the metal layer A can be formed by a magnetron sputtering method in which a raw material capable of forming a Cr mixed-phase film is used as a target and Ar gas is introduced into the chamber. Alternatively, pure Cr may be used as a target, and an appropriate amount of nitrogen gas may be introduced into the chamber together with Ar gas, and the metal layer A may be formed by a reactive sputtering method. At this time, by changing the introduction amount and pressure (nitrogen partial pressure) of nitrogen gas or providing a heating step to adjust the heating temperature, the ratios of CrN and Cr2N contained in the Cr mixed-phase film and the ratio of Cr2N in CrN and Cr2N can be adjusted.

[0071] In these methods, the growth surface of the Cr mixed-phase film is defined by the functional layer made of Ti, and a Cr mixed-phase film mainly composed of α-Cr with a stable crystal structure can be formed. Further, by the diffusion of Ti constituting the functional layer into the Cr mixed-phase film, the gauge characteristics are improved. For example, the gauge factor of the strain gauge 100 can be set to 10 or more, and the gauge factor temperature coefficient TCS and the resistance temperature coefficient TCR can be in the range of -1000 ppm / °C to +1000 ppm / °C. Note that when the functional layer is formed of Ti, the Cr mixed-phase film may contain Ti or TiN (titanium nitride).

[0072] Note that when the metal layer A is a Cr mixed-phase film, the functional layer made of Ti has all of the functions of promoting the crystal growth of the metal layer A, preventing the oxidation of the metal layer A by oxygen and moisture contained in the base material 110, and improving the adhesion between the base material 110 and the metal layer A. The same applies when Ta, Si, Al, or Fe is used instead of Ti as the functional layer.

[0073] Thus, by providing the functional layer under the metal layer A, the crystal growth of the metal layer A can be promoted, and a metal layer A composed of a stable crystal phase can be fabricated. As a result, the stability of the gauge characteristics can be improved in the strain gauge 100. Further, by the diffusion of the material constituting the functional layer into the metal layer A, the gauge characteristics can be improved in the strain gauge 100.

[0074] Next, a second metal layer 142 and a second metal layer 152 are formed on the upper surface of the metal layer A. The second metal layer 142 and the second metal layer 152 can be formed, for example, by a photolithography method.

[0075] Specifically, first, a seed layer is formed, for example, by sputtering or electroless plating, so as to cover the upper surface of the metal layer A. Next, a photosensitive resist is formed over the entire upper surface of the seed layer, and is exposed and developed to form an opening that exposes the regions for forming the second metal layer 142 and the second metal layer 152. At this time, by adjusting the shape of the opening in the resist, the pattern of the second metal layer 142 can be made into an arbitrary shape. As the resist, for example, a dry film resist or the like can be used.

[0076] Next, for example, by an electroplating method using the seed layer as a power supply path, the second metal layer 142 and the second metal layer 152 are formed on the seed layer exposed within the opening. The electroplating method is suitable in that it has a high tact and can form an electroplated layer with low stress as the second metal layer 142 and the second metal layer 152. By making the electroplated layer with a thick film thickness have low stress, warping of the strain gauge 100 can be prevented. Note that the second metal layer 142 and the second metal layer 152 may be formed by an electroless plating method.

[0077] Next, the resist is removed. The resist can be removed, for example, by immersing it in a solution capable of dissolving the resist material.

[0078] Next, a photosensitive resist is formed over the entire upper surface of the seed layer, and is exposed and developed to be patterned into the same planar shape as the resistor 130, the wiring 140, and the electrode 150 in FIG. 4. As the resist, for example, a dry film resist or the like can be used. Then, using the resist as an etching mask, the metal layer A and the seed layer exposed from the resist are removed to form the resistor 130, the wiring 140, and the electrode 150 having the planar shape in FIG. 4.

[0079] For example, by wet etching, unnecessary portions of the metal layer A and the seed layer can be removed. When a functional layer is formed under the metal layer A, the functional layer is patterned into the planar shape shown in FIG. 4 in the same manner as the resistor 130, the wiring 140, and the electrode 150 by etching. At this point, a seed layer is formed on the resistor 130, the first metal layer 141, and the first metal layer 151.

[0080] Next, using the second metal layer 142 and the second metal layer 152 as an etching mask, the unnecessary seed layer exposed from the second metal layer 142 and the second metal layer 152 is removed, thereby forming the second metal layer 142 and the second metal layer 152. Note that the seed layer immediately below the second metal layer 142 and the second metal layer 152 remains. For example, the unnecessary seed layer can be removed by wet etching using an etching solution in which the seed layer is etched and the functional layer, the resistor 130, the wiring 140, and the electrode 150 are not etched.

[0081] Thereafter, if necessary, a strain gauge 100 is completed by providing a cover layer 160 on the upper surface 110a of the base material 110 that covers the resistor 130 and the wiring 140 and exposes the electrode 150. The cover layer 160 can be produced, for example, by laminating a semi-cured thermosetting insulating resin film on the upper surface 110a of the base material 110 so as to cover the resistor 130 and the wiring 140 and expose the electrode 150, and then heating and curing it. The cover layer 160 may also be produced by applying a liquid or paste-like thermosetting insulating resin on the upper surface 110a of the base material 110 so as to cover the resistor 130 and the wiring 140 and expose the electrode 150, and then heating and curing it.

[0082] Thus, the Cr mixed-phase film has high sensitivity. Therefore, by using the strain gauge 100 with the Cr mixed-phase film as the resistor 130 in the sensor module 20, the sensitivity of the resistance value to the expansion of the battery is significantly improved compared to the case where the resistor 130 is formed of Cu-Ni or Ni-Cr. When the resistor 130 is formed of the Cr mixed-phase film, the sensitivity of the resistance value to the expansion of the battery is approximately 5 to 10 times that in the case where the resistor 130 is formed of Cu-Ni or Ni-Cr. Therefore, by forming the resistor 130 of the Cr mixed-phase film, it becomes possible to accurately detect the expansion of the battery.

[0083] <Second Embodiment> In the second embodiment, examples of a sensor module in which the shape of the strain generating body is different and a battery pack to which this is applied are shown. In the second embodiment, the description of the same components as those in the already described embodiments may be omitted.

[0084] FIG. 6 is a plan view illustrating a battery pack according to the second embodiment. FIG. 7 is a cross-sectional view illustrating the battery pack according to the second embodiment, showing a cross-section along the line C-C in FIG. 6.

[0085] Referring to FIGS. 6 and 7, the battery pack 1A is different from the battery pack 1 (see FIGS. 1 to 3, etc.) in that the sensor module 20 is replaced with the sensor module 20A.

[0086] The sensor module 20A is a sensor that detects the deformation of the housing 10 due to the expansion of the battery. The sensor module 20A includes a strain generating body 50A and a strain gauge 100 disposed on one surface of the strain generating body 50A via an adhesive layer 70.

[0087] The strain generating body 50A is an elongated flat plate and is not bent like the strain generating body 50. The strain generating body 50A is approximately rectangular in plan view, but has a stress concentration portion 51 partially. The stress concentration portion 51 is a region formed such that the cross-sectional area in the short side direction of the strain generating body 50A is smaller than other regions. The strain gauge 100 is disposed at the stress concentration portion 51.

[0088] The stress concentration portion 51 has two constrictions that face each other across the strain gauge 100 in a plan view. In the example of FIG. 6, the stress concentration portion 51 is formed by providing two trapezoidal constrictions on the two long sides of the rectangle so as to face each other across the strain gauge 100, but the shape is not limited to this. Further, the position of the constriction is not necessarily limited to near the center in the longitudinal direction of the strained body 50A, and it may be provided at a position offset from the center. For example, a constriction may be provided at a position close to the adhesive region within the non-adhesive region.

[0089] A plurality of adhesive regions to be adhered to the housing 10 are defined on the lower surface of the strained body 50A. In the example of FIG. 7, one adhesive region is defined at each of both ends in the longitudinal direction of the strained body 50A. An adhesive layer 31 is provided in the adhesive region on one end side, and an adhesive layer 32 is provided in the adhesive region on the other end side. In the strained body 50A, the region excluding both ends is a non-adhesive region that is not adhered to the housing 10. Note that the stress concentration portion 51 is provided in the non-adhesive region.

[0090] In a cross-sectional view in the longitudinal direction of the strained body 50A, it is preferable that the length of the region between the two adhesive regions (that is, the length of the non-adhesive region) is longer than the total length of the adhesive regions. Since the strain gauge 100 can detect the strain in the non-adhesive region, by making the non-adhesive region longer, the deformation of the housing 10 due to the expansion of the battery can be detected in a longer region of the strained body 50A.

[0091] For example, when the housing 10 is formed of metal, if the strain gauge 100 is directly attached to the upper surface of the housing 10 without passing through the strained body 50A, only the strain in the region where the strain gauge 100 is attached can be detected. On the other hand, by attaching the elongated strained body 50A having the strain gauge 100 to the upper surface of the housing 10 by supporting both ends, the strain in a wide range between the two supported points can be detected.

[0092] One end side in the longitudinal direction of the distortion generating body 50A is adhered to the upper surface of the housing 10 via the adhesive layer 31, and the other end side in the longitudinal direction of the distortion generating body 50A is adhered to the upper surface of the housing 10 via the adhesive layer 32. The strain gauge 100 is preferably arranged near the center of the stress concentration portion 51 on the upper surface of the distortion generating body 50A. In other words, the strain gauge 100 is preferably arranged in a region on the upper surface of the distortion generating body 50A where the cross-sectional area in the short side direction is the smallest among the stress concentration portions 51.

[0093] In the battery pack 1A, similarly to the battery pack 1, a space S is provided on the opposite surface side (housing 10 side) of the region where the strain gauge 100 of the distortion generating body 50A is arranged. In other words, the strain gauge 100 is arranged in a region that does not face the adhesion region on the upper surface of the distortion generating body 50A. By providing the space S, the distortion generating body 50A can easily expand and contract as the housing 10 deforms due to the expansion of the battery, so that the change in the resistance value of the strain gauge 100 becomes large, and the deformation of the housing 10 can be detected with high sensitivity. Note that the material and thickness of the distortion generating body 50A can be the same as those of the distortion generating body 50.

[0094] The length of the distortion generating body 50A in the longitudinal direction preferably matches the length of the housing 10. Thereby, the misalignment when attaching the distortion generating body 50A to the housing 10 can be reduced.

[0095] FIG. 8 is a cross-sectional view (part 2) illustrating a state in which the housing is deformed due to the expansion of the battery. As shown in FIG. 8, for example, when gas is generated inside the battery arranged in the housing 10, the battery expands, the central portions of the upper and lower surfaces of the housing 10 bulge, and the corner portions also deform. Then, strain occurs in the central portion and the corner portions of the housing 10.

[0096] In FIG. 8, it can be seen that the distortion generating body 50A also deforms as the housing 10 deforms due to the expansion of the battery. Thereby, the resistance value of the strain gauge 100 changes, and the deformation of the housing 10 can be detected. That is, the expansion of the battery housed inside the housing 10 can be detected.

[0097] Thus, when adhering the strain generating body 50A to the housing 10, a space S is provided between the lower surface of the strain generating body 50A and the housing 10, and the strain gauge 100 is arranged on the space S which is a region not facing the adhesion region on the upper surface of the strain generating body 50A, so that the deformation of the housing 10 due to the expansion of the battery can be detected with high sensitivity. In particular, by arranging the strain gauge 100 at the stress concentration portion 51, the detection sensitivity of the deformation of the housing 10 due to the expansion of the battery can be improved. It is also preferable to use, for the sensor module 20A, a strain gauge 100 having a Cr mixed-phase film as the resistor 130, similar to the first embodiment.

[0098] As described above, the preferred embodiments have been described in detail. However, the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope described in the claims.

[0099] For example, a stress concentration portion may be provided in the strain generating body 50 having an L-shaped cross section in a sectional view, and the strain gauge 100 may be arranged at the stress concentration portion. Thereby, the detection sensitivity of the deformation of the housing 10 due to the expansion of the battery can be further improved.

[0100] Also, a plurality of sensor modules may be adhered to one housing. Also, one sensor module may have a plurality of strain gauges. For example, one sensor module may have four strain gauges and they may be connected in a full bridge configuration.

Explanation of Reference Numerals

[0101] 1, 1A Battery pack, 10 Housing, 20, 20A Sensor module, 31, 32 Adhesive layer, 50, 50A Strain generating body, 51 Stress concentration portion, 70 Adhesive layer, 100 Strain gauge, 110 Substrate, 110a Upper surface, 130 Resistor, 140 Wiring, 141, 151 First metal layer, 142, 152 Second metal layer, 150 Electrode, 160 Cover layer

Claims

1. a metallic strain element bonded to an outer surface of a housing that houses the battery; A strain gauge is provided on one surface of the strain generating body, A plurality of mutually spaced adhesive regions are defined on the other surface of the strain body and are adhered to the housing, the strain gauge is disposed in a region of one surface of the strain body that does not face the adhesive region, A sensor module, wherein the resistor of the strain gauge is formed from a material containing at least one of chromium and nickel.

2. The sensor module according to claim 1 , wherein the strain element is L-shaped in cross section.

3. The sensor module according to claim 2 , wherein the adhesive regions are defined on each of the long side and the short side of the L-shape.

4. The sensor module according to claim 2 , wherein the L-shaped bent portion is a non-adhesive region that is not adhered to the housing.

5. The strain generating body is an elongated flat plate, The sensor module according to claim 1 , wherein the adhesive regions are defined on both ends of the strain body in a longitudinal direction.

6. The sensor module according to claim 5 , wherein in a cross-sectional view of the strain body in a longitudinal direction, a length of a region between two of the adhesive regions is longer than a total length of the adhesive regions.

7. The sensor module according to claim 5 , wherein a length of the strain generating element in a longitudinal direction coincides with a length of the housing.

8. The strain generating element has a stress concentration portion, The sensor module according to claim 1 , wherein the strain gauge is disposed in the stress concentration portion.

9. The sensor module according to claim 8 , wherein the stress concentrating portion has two constrictions that face each other across the strain gauge in a plan view.

10. The sensor module according to claim 1 , wherein the adhesive region is provided with an adhesive layer.

11. A battery pack comprising the sensor module according to claim 1 adhered to an outer surface of a housing that houses a battery.

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