Strain gauges, sensor modules

Abstract

To provide a smaller strain gauge.SOLUTION: The strain gauge comprises: a flexible resin substrate; a functional layer formed of metal, alloy, or a metal compound disposed directly on one surface of the substrate; a resistor disposed directly on one surface of the functional layer, formed of a film containing Cr, CrN and Cr2 N and primarily containing α-Cr; a pair of wiring patterns formed on the substrate and electrically connected to both ends of the resistor; and a pair of electrodes formed on the substrate and electrically connected to the wiring pattern. The functional layer has a function of promoting crystal growth of α-Cr and depositing a film primarily containing α-Cr. The resistor has a thickness of 0.05 μm or more and 2 μm or less. The functional layer has a thickness of 1 nm or more and 100 nm or less. The wiring pattern includes a first layer extending from the resistor, and a second layer deposited on the first layer and having lower resistance than the first layer. An electronic component mounting region on which electronic components electrically connected to the electrodes can be mounted is defined on the substrate.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a strain gauge and a sensor module. [Background technology]

[0002] Strain gauges are known that are attached to a measurement object to detect strain on the object. The strain gauge includes a resistor that detects strain, and the resistor is made of, for example, a material containing Cr (chromium) or Ni (nickel). Furthermore, for example, both ends of the resistor are used as electrodes, and lead wires for external connection are joined to the electrodes by soldering, enabling signal input and output with electronic components (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-74934 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when lead wires are used to electrically connect the electrodes and the electronic components, the overall size of the device increases.

[0005] The present invention has been made in view of the above points, and has an object to reduce the size of a strain gauge. [Means for solving the problem]

[0006] This strain gauge comprises a flexible resin substrate, a functional layer formed directly on one side of the substrate from a metal, alloy, or metal compound, a resistor whose main component is α-Cr and formed from a film containing Cr, CrN, and CrN directly on one side of the functional layer, a pair of wiring patterns formed on the substrate and electrically connected to both ends of the resistor, and a pair of electrodes formed on the substrate and electrically connected to each of the wiring patterns, wherein the functional layer has the function of promoting crystal growth of the α-Cr and forming the film whose main component is α-Cr, the resistor has a thickness of 0.05 μm to 2 μm, and the functional layer has a thickness of 1 nm to 100 nm, the wiring pattern includes a first layer extending from the resistor and a second layer stacked on the first layer and having a lower resistance than the first layer, and an electronic component mounting area is defined on the substrate in which electronic components electrically connected to the electrodes can be mounted. [Effects of the Invention]

[0007] According to the disclosed technology, the strain gauge can be made smaller. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a plan view illustrating a strain gauge according to a first embodiment. [Figure 2] 1 is a cross-sectional view illustrating a strain gauge according to a first embodiment. [Figure 3] FIG. 2 is a plan view illustrating a strain gauge according to a first modified example of the first embodiment. [Figure 4] 1 is a cross-sectional view illustrating a strain gauge according to a first modified example of the first embodiment. [Figure 5] 10 is a plan view (part 1) illustrating a strain gauge according to a second modification of the first embodiment. FIG. [Figure 6] 10 is a second plan view illustrating a strain gauge according to a second modification of the first embodiment; FIG. [Figure 7] FIG. 10 is a plan view illustrating a strain gauge according to a third modification of the first embodiment. [Figure 8] FIG. 10 is a cross-sectional view illustrating a sensor module according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following describes the preferred embodiments of the present invention with reference to the accompanying drawings. In the drawings, the same components are designated by the same reference numerals, and redundant explanations may be omitted.

[0010] First Embodiment Fig. 1 is a plan view illustrating a strain gauge according to a first embodiment. Fig. 2 is a cross-sectional view illustrating the strain gauge according to the first embodiment, taken along line AA in Fig. 1. Referring to Figs. 1 and 2, the strain gauge 1 has a substrate 10, a resistor 30, a wiring pattern 40, and an electrode 40A.

[0011] In this embodiment, for convenience, the side of the strain gauge 1 on which the resistor 30 of the substrate 10 is provided is referred to as the upper side or one side, and the side on which the resistor 30 is not provided is referred to as the lower side or the other side. Furthermore, the surface on which the resistor 30 of each portion is provided is referred to as the one side or upper side, and the surface on which the resistor 30 is not provided is referred to as the other side or lower side. However, the strain gauge 1 can be used upside down or positioned at any angle. Furthermore, a planar view refers to viewing an object from the normal direction of the upper surface 10a of the substrate 10, and a planar shape refers to the shape of the object viewed from the normal direction of the upper surface 10a of the substrate 10.

[0012] The substrate 10 is a flexible member that serves as a base layer for forming the resistor 30 and the like. The thickness of the substrate 10 is not particularly limited and can be appropriately selected depending on the purpose, but can be, for example, about 5 μm to 500 μm. In particular, a thickness of 5 μm to 200 μm is preferable in terms of the transferability of strain from the surface of the strain generator bonded to the lower surface of the substrate 10 via an adhesive layer or the like and dimensional stability against the environment, and a thickness of 10 μm or more is even more preferable in terms of insulation properties.

[0013] The substrate 10 can be formed from an insulating resin film such as PI (polyimide) resin, epoxy resin, PEEK (polyether ether ketone) resin, PEN (polyethylene naphthalate) resin, PET (polyethylene terephthalate) resin, PPS (polyphenylene sulfide) resin, polyolefin resin, etc. The film refers to a flexible member having a thickness of about 500 μm or less.

[0014] Here, "formed from an insulating resin film" does not prevent the base material 10 from containing fillers, impurities, etc. in the insulating resin film. The base material 10 may be formed from an insulating resin film containing fillers such as silica or alumina, for example.

[0015] An electronic component mounting region 101 is defined on the upper surface 10a of the substrate 10, where electronic components electrically connected to the electrodes 40A can be mounted. The electronic components that can be mounted in the electronic component mounting region 101 include active components such as semiconductor chips and passive components such as capacitors. A wiring pattern electrically connected to the electronic components may be formed within the electronic component mounting region 101.

[0016] The resistor 30 is a thin film formed in a predetermined pattern on the substrate 10, and is a sensing part that generates a resistance change when strain is applied. The resistor 30 may be formed directly on the upper surface 10a of the substrate 10, or may be formed on the upper surface 10a of the substrate 10 via another layer. For convenience, the resistor 30 is shown in FIG. 1 with a matte finish.

[0017] The resistor 30 can be formed from, for example, a material containing Cr (chromium), a material containing Ni (nickel), or a material containing both Cr and Ni. That is, the resistor 30 can be formed from a material containing at least one of Cr and Ni. An example of a material containing Cr is a Cr mixed phase film. An example of a material containing Ni is Ni-Cu (nickel copper). An example of a material containing both Cr and Ni is Ni-Cr (nickel chromium).

[0018] Here, the Cr mixed phase film is a film containing a mixture of Cr, CrN, Cr2N, etc. The Cr mixed phase film may contain inevitable impurities such as chromium oxide.

[0019] The thickness of resistor 30 is not particularly limited and can be appropriately selected depending on the purpose, but can be, for example, about 0.05 μm to 2 μm. In particular, a thickness of resistor 30 of 0.1 μm or more is preferable because it improves the crystallinity of the crystals constituting resistor 30 (for example, the crystallinity of α-Cr), and a thickness of 1 μm or less is even more preferable because it reduces cracks in the film constituting resistor 30 and warpage from substrate 10 caused by internal stress in the film.

[0020] For example, when the resistor 30 is a Cr mixed-phase film, the stability of the gauge characteristics can be improved by using α-Cr (alpha chromium), which has a stable crystalline phase, as the main component. Furthermore, by using α-Cr as the main component of the resistor 30, the gauge factor of the strain gauge 1 can be 10 or more, and the temperature coefficient of gauge factor (TCS) and temperature coefficient of resistance (TCR) can be within the range of −1000 ppm / °C to +1000 ppm / °C. Here, “main component” means that the target substance accounts for 50 mass% or more of all materials constituting the resistor. From the viewpoint of improving the gauge characteristics, however, it is preferable that the resistor 30 contains α-Cr at 80 wt% or more. Note that α-Cr is Cr with a bcc structure (body-centered cubic lattice structure).

[0021] The wiring pattern 40 is a pair of wiring patterns electrically connected to both ends of the resistor 30. The wiring pattern 40 has a first layer 41 and a second layer 42 laminated on the first layer 41. The first layer 41 extends from both ends of the resistor 30 and is formed in a generally rectangular shape wider than the resistor 30 in a plan view. The second layer 42 is laminated on the top surface of the first layer 41. For example, the resistor 30 extends from one side of the wiring pattern 40 while folding back in a zigzag pattern and is connected to the other side of the wiring pattern 40. The wiring pattern 40 is not limited to a linear shape and can be any pattern. Furthermore, the wiring pattern 40 can have any width and length.

[0022] The electrodes 40A are electrically connected to each of the wiring patterns 40. The electrodes 40A are a pair of electrodes for outputting a change in the resistance value of the resistor 30 caused by strain, and are electrically connectable to an electronic component mounted in the electronic component mounting region 101. The electrodes 40A may be formed to have a width different from that of the wiring patterns 40.

[0023] Although the resistor 30 and the first layer 41 are denoted by different reference numerals for convenience, they can be integrally formed from the same material in the same process.

[0024] The second layer 42 has a lower resistance than the first layer 41. The material of the second layer 42 is not particularly limited and can be appropriately selected depending on the purpose as long as it has a lower resistance than the first layer 41, and examples of materials that can be used include Cu, a Cu alloy, Ni, and a Ni alloy. The thickness of the second layer 42 can be, for example, about 0.5 μm to 30 μm.

[0025] The second layer 42 may be a laminated film. Examples of laminated films include Cu / Ni / Au, Cu / NiP / Au, Cu / Pd / Au, Cu / Pt / Au, Ni / Au, and NiP / Au. Note that "AA / BB" refers to a laminated film in which an AA layer and a BB layer are laminated in that order on the upper surface of a lower layer (the same applies to three or more layers). In these laminated films, a Cu alloy may be used instead of Cu, and a Ni alloy may be used instead of Ni.

[0026] Although the wiring pattern 40 and the electrode 40A are given different reference numerals for convenience, they can be integrally formed from the same material in the same process. However, the layer structure of the electrode 40A may be different from that of the wiring pattern 40. For example, Au or the like may be formed only on the top layer of the electrode 40A to improve connection reliability.

[0027] By selecting the material of the second layer 42 in this way, it is possible to improve the reliability of connection with the electronic component without relying on the material of the first layer 41, which is the same material as the resistor 30.

[0028] In addition, an external input / output terminal can be provided at any position on the upper surface 10a of the substrate 10, which can be electrically connected to the electronic components mounted in the electronic component mounting area 101 and can input and output signals to and from an external circuit electrically connected to the strain gauge 1.

[0029] A cover layer 60A (first insulating resin layer) may be provided on the upper surface 10a of the substrate 10 so as to cover the resistor 30 and the wiring pattern 40 and expose the electrodes 40A and the electronic component mounting region 101. By providing the cover layer 60A, it is possible to prevent mechanical damage, etc. from occurring to the resistor 30 and the wiring pattern 40. Furthermore, by providing the cover layer 60A, it is possible to protect the resistor 30 and the wiring pattern 40 from moisture, etc. The cover layer 60A may be provided so as to cover the entire portion except for the electrodes 40A and the electronic component mounting region 101.

[0030] The cover layer 60A can be formed from an insulating resin such as PI resin, epoxy resin, PEEK resin, PEN resin, PET resin, PPS resin, or composite resin (e.g., silicone resin or polyolefin resin). The cover layer 60A may contain a filler or a pigment. There are no particular restrictions on the thickness of the cover layer 60A and it can be appropriately selected depending on the purpose, but it can be, for example, about 2 μm to 30 μm.

[0031] To manufacture the strain gauge 1, first, a substrate 10 is prepared, and then the resistor 30 and first layer 41 having the planar shape shown in Fig. 1 are formed on the upper surface 10a of the substrate 10. The material and thickness of the resistor 30 and first layer 41 are as described above. The resistor 30 and the first layer 41 can be integrally formed from the same material.

[0032] The resistor 30 and the first layer 41 can be formed, for example, by depositing a film by magnetron sputtering using a target made of a material capable of forming the resistor 30 and the first layer 41, and then patterning the film by photolithography. Instead of magnetron sputtering, the resistor 30 and the first layer 41 may be deposited by reactive sputtering, vapor deposition, arc ion plating, pulsed laser deposition, or the like.

[0033] From the viewpoint of stabilizing the gauge characteristics, it is preferable to vacuum-form a functional layer having a thickness of about 1 nm to 100 nm on the upper surface 10a of the substrate 10 by, for example, conventional sputtering as a base layer before forming the resistor 30 and the first layer 41. After the resistor 30 and the first layer 41 are formed on the entire upper surface of the functional layer, the functional layer is patterned together with the resistor 30 and the first layer 41 into the planar shape shown in FIG.

[0034] In this application, the functional layer refers to a layer having a function of promoting crystal growth of at least the upper layer, the resistor 30. The functional layer preferably also has a function of preventing oxidation of the resistor 30 due to oxygen or moisture contained in the substrate 10, and a function of improving adhesion between the substrate 10 and the resistor 30. The functional layer may also have other functions.

[0035] The insulating resin film that constitutes the substrate 10 contains oxygen and moisture, and since Cr forms a self-oxidized film, it is effective for the functional layer to have the function of preventing oxidation of the resistor 30, especially when the resistor 30 contains Cr.

[0036] The material of the functional layer is not particularly limited as long as it has the function of promoting the crystal growth of at least the upper layer, the resistor 30, and can be appropriately selected depending on 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), Examples of suitable metals include one or more metals selected from the group consisting of 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), and Al (aluminum), alloys of any of the metals in this group, and compounds of any of the metals in this group.

[0037] Examples of the alloys include FeCr, TiAl, FeNi, NiCr, CrCu, etc. Examples of the compounds include TiN, TaN, Si3N4, TiO2, Ta2O5, SiO2, etc.

[0038] The functional layer can be formed in vacuum by conventional sputtering, for example, using a target made of a material capable of forming the functional layer and introducing Ar (argon) gas into a chamber. By using conventional sputtering, the functional layer is formed while etching the upper surface 10a of the substrate 10 with Ar, thereby minimizing the amount of the functional layer formed and achieving an improvement in adhesion.

[0039] However, this is just one example of a method for forming the functional layer, and the functional layer may be formed by other methods. For example, a method may be used in which the upper surface 10a of the substrate 10 is activated by plasma treatment using Ar or the like before forming the functional layer, thereby improving adhesion, and then the functional layer is vacuum-formed by magnetron sputtering.

[0040] There are no particular restrictions on the combination of the material of the functional layer with the material of the resistor 30 and the first layer 41, and it can be selected appropriately depending on the purpose. For example, it is possible to use Ti for the functional layer and form a Cr mixed phase film with α-Cr (alpha chromium) as the main component for the resistor 30 and the first layer 41.

[0041] In this case, resistor 30 and first layer 41 can be formed by magnetron sputtering using a target made of a material capable of forming a Cr mixed phase film and introducing Ar gas into a chamber. Alternatively, resistor 30 and first layer 41 can be formed by reactive sputtering using pure Cr as a target and introducing an appropriate amount of nitrogen gas into a chamber together with Ar gas.

[0042] In these methods, the Ti functional layer defines the growth plane of the Cr mixed-phase film, allowing the formation of a Cr mixed-phase film primarily composed of α-Cr, which has a stable crystal structure. Furthermore, the Ti constituting the functional layer diffuses into the Cr mixed-phase film, improving the gauge characteristics. For example, the gauge factor of the strain gauge 1 can be set to 10 or more, and the temperature coefficient of gauge factor (TCS) and temperature coefficient of resistance (TCR) can be set within the ranges of -1000 ppm / °C to +1000 ppm / °C. When the functional layer is made of Ti, the Cr mixed-phase film may contain Ti or TiN (titanium nitride).

[0043] When the resistor 30 is a Cr mixed phase film, the functional layer made of Ti has all of the following functions: promoting crystal growth of the resistor 30, preventing oxidation of the resistor 30 due to oxygen and moisture contained in the substrate 10, and improving adhesion between the substrate 10 and the resistor 30. The same applies when Ta, Si, Al, or Fe is used as the functional layer instead of Ti.

[0044] In this way, by providing a functional layer below the resistor 30, it is possible to promote crystal growth of the resistor 30, and to produce a resistor 30 consisting of a stable crystalline phase. As a result, it is possible to improve the stability of the gauge characteristics of the strain gauge 1. Furthermore, by diffusing the material constituting the functional layer into the resistor 30, it is possible to improve the gauge characteristics of the strain gauge 1.

[0045] After forming the resistor 30 and the first layer 41, the second layer 42 is laminated on the first layer 41. The material and thickness of the second layer 42 are as described above. The second layer 42 can be formed by, for example, electrolytic plating or electroless plating.

[0046] After forming the second layer 42, if necessary, a cover layer 60A is provided on the upper surface 10a of the substrate 10 to cover the resistor 30 and the wiring pattern 40 and expose the electrodes 40A and the electronic component mounting area 101, thereby completing the strain gauge 1. The cover layer 60A can be produced, for example, by laminating a semi-cured thermosetting insulating resin film on the upper surface 10a of the substrate 10 so as to cover the resistor 30 and the wiring pattern 40 and expose the electrodes 40A and the electronic component mounting area 101, and then heating and curing the film. The cover layer 60A may also be produced by applying a liquid or paste-like thermosetting insulating resin to the upper surface 10a of the substrate 10 so as to cover the resistor 30 and the wiring pattern 40 and expose the electrodes 40A and the electronic component mounting area 101, and then heating and curing the resin.

[0047] In this way, in the strain gauge 1, the resistor 30, wiring pattern 40, electrodes 40A, and electronic component mounting area 101 are provided on the top surface 10a of a single substrate 10. This allows the electronic component mounted on the electronic component mounting area 101 to be connected to the electrodes 40A over a short distance using metal wires or the like, thereby shortening the distance from the resistor 30 to the electronic component, thereby achieving a compact strain gauge 1. This structure is particularly effective for compact strain gauges where it is difficult to connect the resistor and electronic component using lead wires with solder or the like.

[0048] Furthermore, by shortening the distance from the resistor 30 to the electronic component, noise resistance can be improved.

[0049] Moreover, the electrode 40A has a structure in which the second layer 42 is laminated on the first layer 41. Therefore, by selecting the material of the second layer 42, it is possible to improve the reliability of connection with the electronic component without depending on the material of the first layer 41, which is the same material as the resistor 30.

[0050] <Modification 1 of the First Embodiment> In Modification 1 of the first embodiment, an example of a strain gauge in which an electronic component is mounted in an electronic component mounting area is shown. Note that in Modification 1 of the first embodiment, the description of the same components as those in the already described embodiments may be omitted.

[0051] Fig. 3 is a plan view illustrating a strain gauge according to Modification 1 of the first embodiment. Fig. 4 is a cross-sectional view illustrating the strain gauge according to Modification 1 of the first embodiment, taken along line BB in Fig. 3.

[0052] 3 and 4, the strain gauge 1A has an electronic component 200 mounted on the electronic component mounting area 101 of the strain gauge 1.

[0053] The electronic component 200 is, for example, a semiconductor chip that amplifies and temperature compensates for an electrical signal input from the resistor 30 via the wiring pattern 40 and the electrode 40A. Passive components such as a capacitor may be mounted together with the semiconductor chip. The electronic component 200 is mounted in an electronic component mounting region 101 defined on the upper surface 10a of the substrate 10, for example, via an adhesive layer such as a die attach film.

[0054] Electrode 200A of electronic component 200 is electrically connected to electrode 40A via metal wire 210 such as a gold wire or a copper wire. Electrode 200A and electrode 40A can be connected by wire bonding, for example.

[0055] When the cover layer 60A is not provided on the upper surface 10a of the substrate 10, a cover layer 60B (second insulating resin layer) may be provided on the upper surface 10a of the substrate 10 so as to cover the resistor 30, the wiring pattern 40, the electrodes 40A, the electronic component 200, and the metal wire 210. By providing the cover layer 60B, it is possible to prevent mechanical damage and the like from occurring to the resistor 30, the wiring pattern 40, the electrodes 40A, the electronic component 200, and the metal wire 210. Furthermore, by providing the cover layer 60B, it is possible to protect the resistor 30, the wiring pattern 40, the electrodes 40A, the electronic component 200, and the metal wire 210 from moisture and the like.

[0056] The cover layer 60B can be formed from an insulating resin such as PI resin, epoxy resin, PEEK resin, PEN resin, PET resin, PPS resin, or a composite resin (e.g., silicone resin or polyolefin resin). The cover layer 60B may contain a filler or pigment. The thickness of the cover layer 60B is not particularly limited and can be appropriately selected depending on the purpose, but may be, for example, approximately 2 μm to 30 μm. The cover layer 60B can be produced, for example, by laminating a semi-cured thermosetting insulating resin film on the upper surface 10a of the substrate 10 so as to cover the wiring pattern 40, electrodes 40A, electronic components 200, and metal wires 210, and then heating and curing the film. The cover layer 60B may also be produced by applying a liquid or paste-like thermosetting insulating resin to the upper surface 10a of the substrate 10 so as to cover the wiring pattern 40, electrodes 40A, electronic components 200, and metal wires 210, and then heating and curing the film.

[0057] When the cover layer 60A is provided on the upper surface 10a of the substrate 10, a cover layer 60B may be further provided to cover the cover layer 60A, the electrodes 40A, the electronic components 200, and the metal wires 210. By providing the cover layer 60B, it is possible to prevent mechanical damage and the like from occurring to the electrodes 40A, the electronic components 200, and the metal wires 210 that are not covered by the cover layer 60A. Furthermore, by providing the cover layer 60B, it is possible to protect the electrodes 40A, the electronic components 200, and the metal wires 210 that are not covered by the cover layer 60A from moisture and the like. The cover layers 60A and 60B may be formed from the same material or different materials.

[0058] In this way, in strain gauge 1A, resistor 30, wiring pattern 40, electrode 40A, and electronic component 200 are provided on top surface 10a of a single substrate 10. Electrode 200A of electronic component 200 can be connected to electrode 40A over a short distance using metal wire 210, which makes it possible to shorten the distance from resistor 30 to electronic component 200, thereby realizing a compact strain gauge 1A. This structure is particularly effective for compact strain gauges where it is difficult to connect a resistor and an electronic component using lead wires with solder or the like.

[0059] Furthermore, by shortening the distance from the resistor 30 to the electronic component 200, noise resistance can be improved.

[0060] Moreover, electrode 40A has a structure in which second layer 42 is laminated on first layer 41. Therefore, by selecting the material of second layer 42, it is possible to improve the connection reliability with electronic component 200 without depending on the material of first layer 41, which is the same material as resistor 30.

[0061] 3 and 4 show an example in which electrode 40A and electrode 200A are connected by metal wire 210, but electronic component 200 may be flip-chip mounted on top surface 10a of substrate 10. In this case, routing of wiring pattern 40 is changed so that electrode 40A is disposed within electronic component mounting region 101, and electrode 40A within electronic component mounting region 101 and electrode 200A of electronic component 200 can be connected using a solder ball or the like.

[0062] <Modification 2 of the First Embodiment> In the second modification of the first embodiment, an example of a strain gauge including a plurality of resistors etc. In the second modification of the first embodiment, the description of the same components as those in the already described embodiment may be omitted.

[0063] 5 is a plan view illustrating a strain gauge according to Modification 2 of the first embodiment. The cross-sectional structure of the strain gauge according to Modification 2 of the first embodiment is the same as that in FIG. 2, so the cross-sectional view is omitted.

[0064] 5, strain gauge 1B differs from strain gauge 1 (see FIGS. 1 and 2) in that it has multiple sets of resistors 30, wiring patterns 40, and electrodes 40A. In the example of FIG. 5, strain gauge 1B has three sets of resistors 30, wiring patterns 40, and electrodes 40A, but this is not limited to this, and the strain gauge according to this embodiment may have two sets of resistors 30, wiring patterns 40, and electrodes 40A, or may have four or more sets. Furthermore, the number of resistors 30 and the number of electrodes 40A do not have to be the same.

[0065] For example, as in the strain gauge 1C shown in Fig. 6, four sets of resistors 30 may be connected by wiring patterns 40 to form a Wheatstone bridge circuit. In this case, four connection points between the resistors 30 are connected to electrodes 40A via the wiring patterns 40. Note that the grid direction of each resistor 30 in Fig. 6 is an example and is not limited to this.

[0066] 6, positioning marks 105 are formed near the four corners of the electronic component mounting area 101. The positioning marks 105 are marks used for positioning when mounting electronic components in the electronic component mounting area 101. By forming the positioning marks 105, the mounting positions of the electronic components become clear, and the positions can be controlled using a chip mounter or the like, and the electronic components can be mounted with high positional accuracy in the electronic component mounting area 101. The positioning marks 105 can be formed, for example, in the same process as the resistor 30, the wiring pattern 40, and the electrodes 40A. However, the positioning marks 105 may be formed as needed, and the formation of the positioning marks 105 is not essential.

[0067] 5 and 6, a cover layer 60A may be provided on the upper surface 10a of the substrate 10 so as to cover the resistor 30 and the wiring pattern 40 and expose the electrodes 40A and the electronic component mounting region 101. The material, thickness, and manufacturing method of the cover layer 60A are as described above.

[0068] In this way, in the strain gauge 1B or 1C, multiple sets of resistors 30, wiring patterns 40, electrodes 40A, and electronic component mounting area 101 are provided on the upper surface 10a of a single substrate 10. This makes it possible to realize a compact strain gauge 1B or 1C that can detect strain in multiple areas. Other effects are the same as those of the first embodiment.

[0069] <Third Modification of the First Embodiment> In the third modification of the first embodiment, an example of a strain gauge is shown, which includes a plurality of resistors and has electronic components mounted in the electronic component mounting area. Note that in the third modification of the first embodiment, the description of the same components as those in the previously described embodiments may be omitted.

[0070] 7 is a plan view illustrating a strain gauge according to Modification 3 of the first embodiment. The cross-sectional structure of the strain gauge according to Modification 3 of the first embodiment is the same as that in FIG. 4, and therefore the cross-sectional view is omitted.

[0071] Referring to FIG. 7, the strain gauge 1D is obtained by mounting an electronic component 200 on the electronic component mounting area 101 of the strain gauge 1B.

[0072] The electronic component 200 is, for example, a semiconductor chip that amplifies and temperature-compensates electrical signals input from the resistors 30 via the wiring pattern 40 and the electrodes 40A, and has the function of independently processing electrical signals input from the multiple resistors 30. Passive components such as capacitors may also be mounted together with the semiconductor chip. The electronic component 200 is mounted in an electronic component mounting region 101 defined on the upper surface 10a of the substrate 10, for example, via an adhesive layer such as a die attach film.

[0073] Electrodes 200A of electronic component 200 are electrically connected to each pair of electrodes 40A via metal wires 210 such as gold wires or copper wires. Electrodes 200A and electrodes 40A can be connected by wire bonding, for example.

[0074] However, an electronic component may be individually mounted for each set of resistor 30, wiring pattern 40, and electrode 40A.

[0075] 7, a cover layer 60A may be provided on the upper surface 10a of the substrate 10 so as to cover the resistor 30 and the wiring pattern 40 and expose the electrodes 40A and the electronic component mounting region 101. Alternatively, a cover layer 60B may be provided on the upper surface 10a of the substrate 10 so as to cover the resistor 30, the wiring pattern 40, the electrodes 40A, the electronic component 200, and the metal wires 210. Alternatively, a cover layer 60A may be provided on the upper surface 10a of the substrate 10 so as to cover the resistor 30 and the wiring pattern 40 and expose the electrodes 40A and the electronic component mounting region 101, and a further cover layer 60B may be provided so as to cover the cover layer 60A, the electrodes 40A, the electronic component 200, and the metal wires 210. The materials, thicknesses, and manufacturing methods of the cover layers 60A and 60B are as described above.

[0076] Moreover, strain gauge 1C may be used in place of strain gauge 1B.

[0077] In this way, in the strain gauge 1D, multiple sets of resistors 30, wiring patterns 40, electrodes 40A, and electronic components 200 are provided on the top surface 10a of a single substrate 10. The electrodes 200A of the electronic component 200 can be connected to each set of electrodes 40A over a short distance using metal wires 210, which makes it possible to shorten the distance from each set of resistors 30 to the electronic component 200, thereby realizing a compact strain gauge 1D that can detect strain in multiple regions. Other effects are the same as those of the first modification of the first embodiment.

[0078] 7 shows an example in which each set of electrodes 40A and electrodes 200A are connected by metal wires 210, but electronic component 200 may be flip-chip mounted on top surface 10a of substrate 10. In this case, the routing of each set of wiring pattern 40 is changed so that each set of electrodes 40A is disposed within electronic component mounting region 101, and each set of electrodes 40A within electronic component mounting region 101 and electrodes 200A of electronic component 200 can be connected using solder balls or the like.

[0079] Second Embodiment In the second embodiment, an example of a sensor module using a strain gauge will be described. Note that in the second embodiment, the description of the same components as those in the already described embodiments may be omitted.

[0080] Fig. 8 is a cross-sectional view illustrating a sensor module according to the second embodiment, showing a cross section corresponding to Fig. 4. Referring to Fig. 8, the sensor module 5 has a strain gauge 1A, a flexure element 510, and an adhesive layer 520.

[0081] In the sensor module 5, the upper surface 510a of the flexure element 510 is fixed to the lower surface 10b of the substrate 10 via an adhesive layer 520. The flexure element 510 is an object formed from, for example, a metal such as Fe, SUS (stainless steel), or Al, or a resin such as PEEK, and deforms (generates strain) in response to an applied force. The strain gauge 1A can detect the strain generated in the flexure element 510 as a change in the resistance value of the resistor 30.

[0082] The adhesive layer 520 is not particularly limited and can be made of any material that functions to bond the strain gauge 1A and the flexure element 510 together, and can be selected appropriately depending on the purpose. For example, epoxy resin, modified epoxy resin, silicone resin, modified silicone resin, urethane resin, modified urethane resin, etc. can be used. Alternatively, a material such as a bonding sheet can be used. The thickness of the adhesive layer 520 is not particularly limited and can be selected appropriately depending on the purpose, and can be, for example, about 0.1 μm to 50 μm.

[0083] To manufacture the sensor module 5, after fabricating the strain gauge 1A, for example, one of the above materials to become the adhesive layer 520 is applied to the lower surface 10b of the substrate 10 and / or the upper surface 510a of the flexure element 510. Then, the lower surface 10b of the substrate 10 is placed opposite the upper surface 510a of the flexure element 510, and the strain gauge 1A is placed on the flexure element 510 with the applied material sandwiched between them. Alternatively, a bonding sheet may be sandwiched between the flexure element 510 and the substrate 10.

[0084] Next, the strain gauge 1A is heated to a predetermined temperature while being pressed against the flexure element 510, and the applied material is cured to form the adhesive layer 520. As a result, the upper surface 510a of the flexure element 510 and the lower surface 10b of the substrate 10 are fixed to each other via the adhesive layer 520, completing the sensor module 5. The sensor module 5 can be used to measure, for example, load, pressure, torque, acceleration, etc.

[0085] In addition, strain gauge 1A may be replaced by strain gauge 1, 1B, 1C, or 1D in sensor module 5. However, when strain gauge 1, 1B, or 1C is used, cover layer 60A may be provided as needed, but cover layer 60B is not provided.

[0086] The above describes in detail preferred embodiments, but 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 of the claims. [Explanation of symbols]

[0087] 1, 1A, 1B, 1C, 1D strain gauge, 5 sensor module, 10 substrate, 10a, 510a upper surface, 10b lower surface, 30 resistor, 40 wiring pattern 40A, 200A electrode, 41 first layer, 42 second layer, 60A, 60B cover layer, 101 electronic component mounting area, 105 positioning mark, 200 electronic component, 210 metal wire, 510 strain element, 520 adhesive layer

Claims

1. a flexible resin substrate; a functional layer formed of a metal, an alloy, or a metal compound directly on one surface of the substrate; Cr, CrN, and Cr are directly applied to one surface of the functional layer. ２ a resistor formed from a film containing N and containing α-Cr as a main component; a pair of wiring patterns formed on the substrate and electrically connected to both ends of the resistor; a pair of electrodes formed on the substrate and electrically connected to the respective wiring patterns; the functional layer has a function of promoting crystal growth of the α-Cr and forming a film containing the α-Cr as a main component; The resistor has a thickness of 0.05 μm or more and 2 μm or less, The thickness of the functional layer is 1 nm or more and 100 nm or less, the wiring pattern includes a first layer extending from the resistor and a second layer stacked on the first layer and having a lower resistance than the first layer; The strain gauge has an electronic component mounting area defined on the substrate, on which an electronic component electrically connected to the electrodes can be mounted.

2. 2. The strain gauge according to claim 1, wherein the substrate has a plurality of sets of the resistor, the wiring pattern, and the electrode.

3. 3. The strain gauge according to claim 1, further comprising an electronic component mounted in the electronic component mounting area.

4. an electronic component mounted in the electronic component mounting area; 3. The strain gauge according to claim 2, wherein the electronic component includes a semiconductor chip electrically connected to a plurality of sets of the electrodes.

5. 5. The strain gauge according to claim 1, further comprising a first insulating resin layer that covers the resistor and the wiring pattern.

6. 5. The strain gauge according to claim 3, further comprising a second insulating resin layer that covers the resistor, the wiring pattern, the electrodes, and the electronic component.

7. a first insulating resin layer that covers the resistor and the wiring pattern; 5. The strain gauge according to claim 3, further comprising: a second insulating resin layer that covers the first insulating resin layer, the electrodes, and the electronic component.

8. A strain gauge according to any one of claims 1 to 7; a strain-generating element provided on the other surface side of the base material.

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