Strain gauge and sensor module

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 Art

[0002] A strain gauge is known which is attached to a measurement object to detect the strain of the measurement object. The strain gauge includes a resistor for detecting strain, and as the material of the resistor, for example, a material containing Cr (chromium) or Ni (nickel) is used. Further, for example, both ends of the resistor are used as electrodes, and external connection lead wires or the like are joined to the electrodes by solder to enable signal input / output with electronic components (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when using a lead wire for the electrical connection between the electrode and the electronic component, there is a problem that the entire device becomes large.

[0005] The present invention has been made in view of the above points, and an object thereof is to miniaturize the strain gauge.

Means for Solving the Problems

[0006] This strain gauge has a flexible resin base material, a functional layer formed directly on one surface of the base material from metal, alloy, or a metal compound, a resistor mainly composed of α-Cr formed from a film containing Cr, CrN, and Cr2N directly on one surface of the functional layer, a pair of wiring patterns formed on the base material and electrically connected to both ends of the resistor, and a pair of electrodes formed on the base material and electrically connected to each of the wiring patterns. The functional layer has a function of promoting crystal growth of the α-Cr and forming a film mainly composed of the α-Cr. The thickness of the resistor is 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 having a lower resistance than the first layer laminated on the first layer, and an electronic component mounting region capable of mounting an electronic component electrically connected to the electrode is defined on the base material.

Advantages of the Invention

[0007] According to the disclosed technology, the strain gauge can be miniaturized.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Mode for Carrying Out the Invention

[0009] Hereinafter, modes 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.

[0010] 〈First Embodiment〉 FIG. 1 is a plan view exemplifying a strain gauge according to the first embodiment. FIG. 2 is a cross-sectional view exemplifying the strain gauge according to the first embodiment, showing a cross-section along line A-A in FIG. 1. Referring to FIGS. 1 and 2, the strain gauge 1 has a base material 10, a resistor 30, a wiring pattern 40, and an electrode 40A.

[0011] In this embodiment, for convenience, in the strain gauge 1, the side where the resistor 30 of the base material 10 is provided is the upper side or one side, and the side where the resistor 30 is not provided is the lower side or the other side. Also, the surface on the side where the resistor 30 of each part is provided is one surface or the upper surface, and the surface on the side where the resistor 30 is not provided is the other surface or the lower surface. However, the strain gauge 1 can be used in an upside-down state or arranged at an arbitrary angle. Also, a plan view means viewing an object from the normal direction of the upper surface 10a of the base material 10, and a planar shape means the shape of an object viewed from the normal direction of the upper surface 10a of the base material 10.

[0012] The base material 10 is a member serving as a base layer for forming the resistor 30 and the like, and has flexibility. The thickness of the base material 10 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 10 is 5 μm to 200 μm, it is preferable in terms of the transmission of strain from the surface of the strain-generating body joined to the lower surface of the base material 10 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.

[0013] The base material 10 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, or a polyolefin resin. Here, the film refers to a member having a thickness of about 500 μm or less and having flexibility.

[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 capable of mounting an electronic component electrically connected to the electrode 40A is defined on the upper surface 10a of the base material 10. The electronic components that can be mounted in the electronic component mounting region 101 are active components such as semiconductor chips and passive components such as capacitors. A wiring pattern electrically connected to the electronic component may be formed in the electronic component mounting region 101.

[0016] The resistor 30 is a thin film formed on the base material 10 in a predetermined pattern and is a sensing part that undergoes strain and causes a resistance change. The resistor 30 may be formed directly on the upper surface 10a of the base material 10, or may be formed on the upper surface 10a of the base material 10 via another layer. In FIG. 1, for convenience, the resistor 30 is shown in a matte pattern.

[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. Examples of the material containing Cr include a Cr mixed-phase film. Examples of the material containing Ni include Ni-Cu (nickel copper). Examples of the material containing both Cr and Ni include Ni-Cr (nickel chromium).

[0018] Here, the Cr mixed-phase film is a film in which Cr, CrN, Cr2N, etc. are mixed. The Cr mixed-phase film may contain inevitable impurities such as chromium oxide.

[0019] The thickness of the resistor 30 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 30 is 0.1 μm or more, it is preferable in terms of improving the crystallinity of the crystals constituting the resistor 30 (for example, the crystallinity of α-Cr), and when it is 1 μm or less, it is more preferable in terms of reducing film cracks caused by internal stress of the film constituting the resistor 30 and warping from the base material 10.

[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 is a stable crystal phase, as the main component. Also, when the resistor 30 has α-Cr as the main component, the gauge factor of the strain gauge 1 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 mass% or more of all the substances constituting the resistor. From the viewpoint of improving the gauge characteristics, it is preferable that the resistor 30 contains 80 wt% or more of α-Cr. 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 substantially rectangular shape that is wider than the resistor 30 in a plan view. The second layer 42 is laminated on the upper surface of the first layer 41. The resistor 30 extends, for example, while being folded back in a zigzag manner from one of the wiring patterns 40 and is connected to the other wiring pattern 40. The wiring pattern 40 is not limited to a straight line and can be any pattern. Also, the wiring pattern 40 can have any width and any length.

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

[0023] Note that although the resistor 30 and the first layer 41 are given different reference numerals for convenience, the two can be integrally formed of the same material in the same process.

[0024] The second layer 42 is a layer having a lower resistance than the first layer 41. The material of the second layer 42 is not particularly limited as long as it has a lower resistance than the first layer 41, and can be appropriately selected according to the purpose. For example, Cu, a Cu alloy, Ni, or a Ni alloy can be used. 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 the laminated film include Cu / Ni / Au, Cu / NiP / Au, Cu / Pd / Au, Cu / Pt / Au, Ni / Au, NiP / Au, etc. Note that 'AA / BB' means a laminated film in which the AA layer and the BB layer are laminated in this order on the upper surface of the lower layer (the same applies to cases of 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] Note that although the wiring pattern 40 and the electrode 40A are given different reference numerals for convenience, the two can be integrally formed of 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, only Au or the like may be formed on the uppermost layer of the electrode 40A to improve the connection reliability.

[0027] In this way, by selecting the material of the second layer 42, the connection reliability with the electronic component can be improved without depending 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 an arbitrary position on the upper surface 10a of the base material 10. The external input / output terminal can be electrically connected to an electronic component mounted in the electronic component mounting region 101 and enables signal input / output between the 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 base material 10 so as to cover the resistor 30 and the wiring pattern 40 and expose the electrode 40A and the electronic component mounting region 101. By providing the cover layer 60A, mechanical damage or the like to the resistor 30 and the wiring pattern 40 can be prevented. In addition, by providing the cover layer 60A, the resistor 30 and the wiring pattern 40 can be protected from moisture and the like. Note that the cover layer 60A may be provided so as to cover the entire portion except for the electrode 40A and the electronic component mounting region 101.

[0030] The cover layer 60A can be formed of an insulating resin such as a PI resin, an epoxy resin, a PEEK resin, a PEN resin, a PET resin, a PPS resin, or a composite resin (for example, a silicone resin or a polyolefin resin). The cover layer 60A may contain a filler or a pigment. The thickness of the cover layer 60A is not particularly limited and can be appropriately selected according to the purpose. For example, it can be about 2 μm to 30 μm.

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

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

[0033] From the viewpoint of stabilizing the gauge characteristics, before forming the resistor 30 and the first layer 41, it is preferable to vacuum deposit a functional layer having a film thickness of about 1 nm to 100 nm on the upper surface 10a of the base material 10 as an underlayer by, for example, a conventional sputtering method. Note that after forming the resistor 30 and the first layer 41 over 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. 1 by photolithography.

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

[0035] Since the insulating resin film constituting the base material 10 contains oxygen and moisture, particularly when the resistor 30 contains Cr, Cr forms a self-oxidized film, and thus it is effective for the functional layer to have a function of preventing oxidation of the resistor 30.

[0036] The material of the functional layer is not particularly limited as long as it has a function of promoting crystal growth of at least the upper-layer resistor 30 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 these, an alloy of any of the metals in this group, or a compound of any of the metals in this group can be mentioned.

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

[0038] 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 10a of the substrate 10 with Ar, so that the deposition amount of the functional layer can be minimized and the adhesion improvement effect can be obtained.

[0039] However, this is only an example of the method for forming the functional layer, and the functional layer may be formed by other methods. For example, an adhesion improvement effect can be obtained by activating the upper surface 10a of the substrate 10 by plasma treatment using Ar or the like before forming the functional layer, and then a method of forming the functional layer by vacuum deposition by a magnetron sputtering method may be used.

[0040] The combination of the material of the functional layer and the materials of the resistor 30 and the first layer 41 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 resistor 30 and the first layer 41.

[0041] In this case, for example, the resistor 30 and the first layer 41 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 can be used as a target, and an appropriate amount of nitrogen gas can be introduced into the chamber together with Ar gas, and the resistor 30 and the first layer 41 may be formed by a reactive sputtering method.

[0042] 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. Also, since Ti constituting the functional layer diffuses into the Cr mixed-phase film, the gauge characteristics are improved. For example, the gauge factor of the strain gauge 1 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).

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

[0044] In this way, by providing the functional layer under the resistor 30, it becomes possible to promote the crystal growth of the resistor 30, and a resistor 30 composed of a stable crystal phase can be manufactured. As a result, the stability of the gauge characteristics can be improved in the strain gauge 1. Also, since the material constituting the functional layer diffuses into the resistor 30, the gauge characteristics can be improved in 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, for example, by an electrolytic plating method, an electroless plating method, or the like.

[0046] After forming the second layer 42, if necessary, a cover layer 60A is provided on the upper surface 10a of the base material 10 to cover the resistor 30 and the wiring pattern 40 and expose the electrode 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 base material 10 so as to cover the resistor 30 and the wiring pattern 40 and expose the electrode 40A and the electronic component mounting area 101, and then heating and curing it. The cover layer 60A may also be produced by applying a liquid or paste-like thermosetting insulating resin on the upper surface 10a of the base material 10 so as to cover the resistor 30 and the wiring pattern 40 and expose the electrode 40A and the electronic component mounting area 101, and then heating and curing it.

[0047] Thus, in the strain gauge 1, the resistor 30, the wiring pattern 40, the electrode 40A, and the electronic component mounting area 101 are provided on the upper surface 10a of one base material 10. As a result, since the electronic component mounted in the electronic component mounting area 101 and the electrode 40A can be connected at a short distance by a metal wire or the like, the distance from the resistor 30 to the electronic component can be shortened, and a small strain gauge 1 can be realized. This structure is particularly effective for a small strain gauge in which it is difficult to connect the resistor and the electronic component with solder or the like using a lead wire.

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

[0049] Also, 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, the connection reliability with the electronic component can be improved without depending on the material of the first layer 41 which is the same material as the resistor 30.

[0050] <Example 1 of the modification of the first embodiment> Example 1 of the modification of the first embodiment shows an example of a strain gauge with an electronic component mounted in the electronic component mounting area. In Example 1 of the modification of the first embodiment, the description of the same components as those in the already described embodiment 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, showing a cross-section along line B-B in FIG. 3.

[0052] Referring to FIGS. 3 and 4, the strain gauge 1A is obtained by mounting an electronic component 200 on the electronic component mounting region 101 of the strain gauge 1.

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

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

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

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

[0057] When the cover layer 60A is provided on the upper surface 10a of the base material 10, a cover layer 60B may be further provided so as to cover the cover layer 60A, the electrode 40A, the electronic component 200, and the metal wire 210. By providing the cover layer 60B, it is possible to prevent mechanical damage or the like from occurring to the electrode 40A, the electronic component 200, and the metal wire 210 that are not covered by the cover layer 60A. Also, by providing the cover layer 60B, it is possible to protect the electrode 40A, the electronic component 200, and the metal wire 210 that are not covered by the cover layer 60A from moisture or the like. Note that the cover layer 60A and the cover layer 60B may be formed from the same material or from different materials.

[0058] As described above, in the strain gauge 1A, the resistor 30, the wiring pattern 40, the electrode 40A, and the electronic component 200 are provided on the upper surface 10a of one base material 10. Since the electrode 200A of the electronic component 200 and the electrode 40A can be connected at a short distance by the metal wire 210, it is possible to shorten the distance from the resistor 30 to the electronic component 200, and a small strain gauge 1A can be realized. This structure is particularly effective for a small strain gauge in which it is difficult to connect a resistor and an electronic component with solder or the like using a lead wire.

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

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

[0061] In FIGS. 3 and 4, an example of connecting the electrode 40A and the electrode 200A with the metal wire 210 is shown. However, the electronic component 200 may be flip-chip mounted on the upper surface 10a of the base material 10. In this case, the routing of the wiring pattern 40 is changed so that the electrode 40A is arranged within the electronic component mounting region 101, and the electrode 40A within the electronic component mounting region 101 and the electrode 200A of the electronic component 200 can be connected using solder balls or the like.

[0062] <Modification Example 2 of the First Embodiment> In Modification Example 2 of the First Embodiment, an example of a strain gauge including a plurality of resistors and the like is shown. In Modification Example 2 of the First Embodiment, the description of the same components as those in the already described embodiment may be omitted.

[0063] FIG. 5 is a plan view illustrating a strain gauge according to Modification Example 2 of the First Embodiment. Since the cross-sectional structure of the strain gauge according to Modification Example 2 of the First Embodiment is the same as that of FIG. 2, the illustration of the cross-sectional view is omitted.

[0064] Referring to FIG. 5, the strain gauge 1B is different from the strain gauge 1 (see FIGS. 1 and 2) in that it has a plurality of sets of the resistor 30, the wiring pattern 40, and the electrode 40A. In the example of FIG. 5, the strain gauge 1B has three sets of the resistor 30, the wiring pattern 40, and the electrode 40A, but it is not limited thereto. The strain gauge according to the present embodiment may have two sets or four or more sets of the resistor 30, the wiring pattern 40, and the electrode 40A. Also, the number of resistors 30 and the number of electrodes 40A do not have to be the same.

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

[0066] Also, in FIG. 6, positioning marks 105 are formed in the vicinity of the four corners within the electronic component mounting area 101. The positioning mark 105 is a mark used for positioning when mounting an electronic component in the electronic component mounting area 101. By forming the positioning mark 105, the mounting position of the electronic component becomes clear, the position can be controlled by a chip mounter or the like, and the electronic component can be mounted in the electronic component mounting area 101 with high positional accuracy. The positioning mark 105 can be formed, for example, in the same process as the resistor 30, the wiring pattern 40, and the electrode 40A. However, the positioning mark 105 may be formed as necessary, and the formation of the positioning mark 105 is not essential.

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

[0068] As described above, in the strain gauge 1B or 1C, a plurality of sets of resistors 30, wiring patterns 40, electrodes 40A, and an electronic component mounting area 101 are provided on the upper surface 10a of one base material 10. Thereby, a small-sized strain gauge 1B or 1C capable of detecting strain in a plurality of regions can be realized. Other effects are the same as those of the first embodiment.

[0069] <Modification Example 3 of the First Embodiment> In Modification Example 3 of the first embodiment, an example of a strain gauge equipped with a plurality of sets of resistors and the like and having electronic components mounted in the electronic component mounting area is shown. In Modification Example 3 of the first embodiment, the description of the same components as those in the already described embodiments may be omitted.

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

[0071] Referring to FIG. 7, the strain gauge 1D is obtained by mounting an electronic component 200 in 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-corrects an electrical signal input from the resistor 30 via the wiring pattern 40 and the electrode 40A, and has a function of independently processing electrical signals input from a plurality of resistors 30. Passive components such as capacitors may be mounted together with the semiconductor chip. The electronic component 200 is mounted, for example, on the electronic component mounting area 101 defined on the upper surface 10a of the base material 10 via an adhesive layer such as a die attach film.

[0073] The electrode 200A of the electronic component 200 is electrically connected to each set of electrodes 40A via a metal wire 210 such as a gold wire or a copper wire. The electrode 200A and the electrode 40A can be connected, for example, by wire bonding.

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

[0075] In FIG. 7, a cover layer 60A may be provided on the upper surface 10a of the base material 10 so as to cover the resistor 30 and the wiring pattern 40 and expose the electrode 40A and the electronic component mounting area 101. Also, a cover layer 60B may be provided on the upper surface 10a of the base material 10 so as to cover the resistor 30, the wiring pattern 40, the electrode 40A, the electronic component 200, and the metal wire 210. Further, a cover layer 60A may be provided on the upper surface 10a of the base material 10 so as to cover the resistor 30 and the wiring pattern 40 and expose the electrode 40A and the electronic component mounting area 101, and a cover layer 60B may be further provided so as to cover the cover layer 60A, the electrode 40A, the electronic component 200, and the metal wire 210. The materials, thicknesses, and manufacturing methods of the cover layers 60A and 60B are as described above.

[0076] Also, instead of the strain gauge 1B, a strain gauge 1C may be used.

[0077] Thus, in the strain gauge 1D, a plurality of sets of resistors 30, wiring patterns 40, electrodes 40A, and electronic components 200 are provided on the upper surface 10a of one base material 10. Since the electrode 200A of the electronic component 200 and each set of electrodes 40A can be connected at a short distance by the metal wire 210, the distance from each set of resistors 30 to the electronic component 200 can be shortened, and a small strain gauge 1D capable of detecting strain in a plurality of regions can be realized. Other effects are the same as those of Modification 1 of the first embodiment.

[0078] In FIG. 7, an example of connecting each set of electrodes 40A and the electrode 200A with the metal wire 210 is shown, but the electronic component 200 may be flip-chip mounted on the upper surface 10a of the base material 10. In this case, the routing of each set of wiring patterns 40 is changed so that each set of electrodes 40A is arranged within the electronic component mounting area 101, and each set of electrodes 40A within the electronic component mounting area 101 and the electrode 200A of the 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 is shown. In the second embodiment, descriptions of the same components as those in the already described embodiments may be omitted.

[0080] FIG. 8 is a cross-sectional view illustrating the 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 strain generating body 510, and an adhesive layer 520.

[0081] In the sensor module 5, the upper surface 510a of the strain generating body 510 is fixed to the lower surface 10b of the base material 10 via the adhesive layer 520. The strain generating body 510 is an object formed of, for example, a metal such as Fe, SUS (stainless steel), 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 strain generating body 510 as a change in the resistance value of the resistor 30.

[0082] The adhesive layer 520 is not particularly limited as long as it has a function of fixing the strain gauge 1A and the strain generating body 510, and can be appropriately selected according to the purpose. For example, an epoxy resin, a modified epoxy resin, a silicone resin, a modified silicone resin, a urethane resin, a modified urethane resin, etc. can be used. Also, a material such as a bonding sheet may be used. The thickness of the adhesive layer 520 is not particularly limited and can be appropriately selected according to the purpose, but can be, for example, about 0.1 μm to 50 μm.

[0083] To manufacture the sensor module 5, after manufacturing the strain gauge 1A, for example, any of the above materials that will become the adhesive layer 520 is applied to the lower surface 10b of the base material 10 and / or the upper surface 510a of the strain generating body 510. Then, the lower surface 10b of the base material 10 is opposed to the upper surface 510a of the strain generating body 510, and the strain gauge 1A is disposed on the strain generating body 510 with the applied material sandwiched therebetween. Or, a bonding sheet may be sandwiched between the strain generating body 510 and the base material 10.

[0084] Next, while pressing the strain gauge 1A against the strained body 510 side, it is heated to a predetermined temperature to cure the applied material or the like, thereby forming the adhesive layer 520. As a result, the upper surface 510a of the strained body 510 and the lower surface 10b of the base material 10 are fixed via the adhesive layer 520, and the sensor module 5 is completed. The sensor module 5 can be applied, for example, to the measurement of load, pressure, torque, acceleration, etc.

[0085] In the sensor module 5, instead of the strain gauge 1A, the strain gauges 1, 1B, 1C, or 1D may be used. However, when using the strain gauges 1, 1B, or 1C, a cover layer 60A may be provided as necessary, but the cover layer 60B is not provided.

[0086] Although the preferred embodiments and the like have been described in detail above, the present invention is not limited to the above-described embodiments and the like, and various modifications and substitutions can be made to the above-described embodiments and the like without departing from the scope described in the claims.

Description of Reference Numerals

[0087] 1, 1A, 1B, 1C, 1D Strain gauges, 5 Sensor module, 10 Base material, 10a, 510a Upper surface, 10b Lower surface, 30 Resistor, 40 Wiring pattern 40A, 200A Electrode, 41 First layer, 42 Second layer, 60A, 60B Cover layers, 101 Electronic component mounting area, 105 Positioning mark, 200 Electronic component, 210 Metal wire, 510 Strained body, 520 Adhesive layer

Claims

1. A resin-based substrate having flexibility, A functional layer formed directly on one surface of the substrate from a metal, an alloy, or a metal compound, On one surface of the functional layer, directly, a resistor mainly composed of α-Cr formed from a film containing Cr, CrN, and Cr ２ N, and 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 each of the wiring patterns, and having, The functional layer has a function of promoting crystal growth of the α-Cr and forming a film mainly composed of the α-Cr, The thickness of the resistor is 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 having a lower resistance than the first layer laminated on the first layer, A strain gauge in which an electronic component mounting area capable of mounting an electronic component electrically connected to the electrode is defined on the substrate.

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

3. The strain gauge according to claim 1 or 2, having an electronic component mounted in the electronic component mounting area.

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

5. The strain gauge according to any one of claims 1 to 4, having a first insulating resin layer covering the resistor and the wiring pattern.

6. The strain gauge according to claim 3 or 4, having a second insulating resin layer covering the resistor, the wiring pattern, the electrode, and the electronic component.

7. A first insulating resin layer covering the resistor and the wiring pattern, The strain gauge according to claim 3 or 4, having a second insulating resin layer covering the first insulating resin layer, the electrode, and the electronic component.

8. A sensor module having the strain gauge according to any one of claims 1 to 7, And a strain generating body provided on the other surface side of the substrate.

Images