WO2019244991A1

WO2019244991A1 - Sensor module

Info

Publication number: WO2019244991A1
Application number: PCT/JP2019/024560
Authority: WO
Inventors: 祐汰相澤; 小川　隆志; 佑紀丸山
Original assignee: ミネベアミツミ株式会社
Priority date: 2018-06-21
Filing date: 2019-06-20
Publication date: 2019-12-26
Also published as: JP2023138686A; JP2019219313A

Abstract

This sensor module has: a strain gauge that comprises a flexible substrate and a resistor that is formed on the substrate from a material that includes chromium and/or nickel; and a deformable body that transmits strain to the strain gauge. The strain gauge is adhered to the deformable body such that the resistor faces the deformable body.

Description

Sensor module

The present invention relates to a sensor module.

ひずみ Strain gauges that are attached to an object to be measured and detect strain of the object to be measured are known. The strain gauge includes a resistor for detecting strain, and a material containing, for example, Cr (chromium) or Ni (nickel) is used as a material of the resistor. Further, the resistor is formed on, for example, a base material made of an insulating resin and is covered with a protective film (for example, see Patent Document 1).

ひずみ This strain gauge can be used as a sensor module, for example, by bonding the base material side to a strain body via an adhesive layer.

JP 2016-74934 A

However, in the above strain gauge, since a protective film is provided to protect the resistor from moisture and the like, a step of coating the resistor with the protective film is necessary in addition to the step of forming the resistor on the base material. become. Therefore, when the above-described strain gauge is used for a sensor module, there is a problem that the cost of the entire sensor module increases.

The present invention has been made in view of the above points, and has as its object to suppress an increase in cost of a sensor module.

The present sensor module includes a strain gauge having a flexible base material, a resistor formed on the base material from a material containing at least one of chromium and nickel, and a strain gauge for transmitting strain to the strain gauge. A strain body, and the strain gauge is bonded to the strain body with the resistor facing the strain body.

According to the disclosed technology, it is possible to suppress an increase in the cost of the sensor module.

FIG. 2 is a plan view illustrating the sensor module according to the first embodiment. FIG. 2 is a cross-sectional view (part 1) illustrating the sensor module according to the first embodiment. FIG. 3 is a cross-sectional view (part 2) illustrating the sensor module according to the first embodiment.

Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and redundant description may be omitted.

<First Embodiment>
FIG. 1 is a plan view illustrating the sensor module according to the first embodiment. FIG. 2 is a cross-sectional view illustrating the sensor module according to the first embodiment, and shows a cross section taken along line AA in FIG. Referring to FIGS. 1 and 2, the sensor module 5 includes a strain gauge 1, a strain body 110, and an adhesive layer 120. The strain gauge 1 has a base material 10, a resistor 30, and a terminal 41.

In the present embodiment, for the sake of convenience, in the sensor module 5, the substrate 10 side is the upper side or one side, and the strain generating element 110 side is the lower side or the other side. Also, the surface of each part on the base material 10 side is defined as one surface or upper surface, and the surface on the strain generating body 110 side is defined as the other surface or lower surface. However, the sensor module 5 can be used upside down, or can be arranged at any angle. The plan view refers to viewing the target from the normal direction of the upper surface 10a of the base material 10, and the planar shape refers to the shape of the target viewed from the normal direction of the upper surface 10a of the base material 10. And

In the strain gauge 1, the base material 10 is a member serving as a base layer for forming the resistor 30 and the like, and has flexibility. The substrate 10 has an upper surface 10a and a lower surface 10b. The thickness of the base material 10 is not particularly limited and can be appropriately selected depending on the purpose. For example, the thickness can be about 5 μm to 500 μm. In particular, when the thickness of the base material 10 is 5 μm to 200 μm, the transferability of strain from the surface of the strain generating body 110 bonded to the lower surface 10 b of the base material 10 via the adhesive layer 120 and the dimensional stability to the environment Is preferable in terms of insulating property.

The substrate 10 is made of, for example, PI (polyimide) resin, epoxy resin, PEEK (polyetheretherketone) resin, PEN (polyethylene naphthalate) resin, PET (polyethylene terephthalate) resin, PPS (polyphenylene sulfide) resin, polyolefin resin, and the like. From an insulating resin film. Note that a film refers to a member having a thickness of about 500 μm or less and having flexibility.

Here, “formed from an insulating resin film” does not prevent the base material 10 from containing fillers, impurities, and the like in the insulating resin film. The substrate 10 may be formed from, for example, an insulating resin film containing a filler such as silica or alumina.

The resistor 30 is a thin film formed on the lower surface 10b of the base material 10 in a predetermined pattern, and is a sensing portion that undergoes a strain and undergoes a resistance change. The resistor 30 may be formed directly on the lower surface 10b of the substrate 10, or may be formed on the lower surface 10b of the substrate 10 via another layer. In FIG. 1, the resistor 30 is shown in a satin pattern for convenience.

The resistor 30 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 30 can be formed from a material containing at least one of Cr and Ni. As a material containing Cr, for example, a Cr mixed-phase film is given. As a material containing Ni, for example, Cu—Ni (copper nickel) is given. As a material containing both Cr and Ni, for example, Ni—Cr (nickel chrome) can be mentioned.

Here, the Cr mixed phase film is a film in which Cr, CrN, Cr ₂ N and the like are mixed. The Cr mixed phase film may contain unavoidable impurities such as chromium oxide.

The thickness of the resistor 30 is not particularly limited and can be appropriately selected depending on the purpose. For example, the thickness can be about 0.05 μm to 2 μm. In particular, when the thickness of the resistor 30 is 0.1 μm or more, the crystallinity of the crystal constituting the resistor 30 (for example, the crystallinity of α-Cr) is improved. It is further preferable that cracks in the film and warpage from the base material 10 due to the internal stress of the film constituting the film 30 can be reduced.

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 a main component. Further, since the resistor 30 contains α-Cr as a main component, the gauge factor of the strain gauge 1 is 10 or more, and the gauge factor temperature coefficient TCS and the resistance temperature coefficient TCR are within the range of −1000 ppm / ° C. to +1000 ppm / ° C. It can be. Here, the main component means that the target substance occupies 50% by mass or more of all the substances constituting the resistor. From the viewpoint of improving the gauge characteristics, the resistor 30 contains α-Cr at 80% by weight. It is preferable to include the above. Note that α-Cr is Cr having a bcc structure (body-centered cubic lattice structure).

The terminal portions 41 extend from both ends of the resistor 30 and are formed in a substantially rectangular shape with a width wider than that of the resistor 30 in plan view. The terminal portion 41 is a pair of electrodes for outputting a change in the resistance value of the resistor 30 caused by the strain to the outside.

{For example, a part of the side surface of each terminal portion 41 is exposed to the outside of the strain gauge 1, and a lead wire or the like for external connection is joined to the exposed portion. However, if a part of each terminal part 41 is exposed to the outside of the strain gauge 1, the exposed part may not be the side surface of each terminal part 41. For example, a through hole or a notch may be provided in the base material 10 to expose a part or all of the upper surface of each terminal portion 41.

The resistor 30 extends from one of the terminal portions 41 in a zigzag manner, for example, and is connected to the other terminal portion 41. The top and side surfaces of the terminal 41 may be covered with a metal having better solderability than the terminal 41. Note that the resistor 30 and the terminal portion 41 are denoted by different reference numerals for convenience, but they can be integrally formed of the same material in the same step.

In the sensor module 5, the lower surface 10 b side of the base material 10 is bonded to the upper surface 110 a of the strain body 110 via the bonding layer 120. That is, the strain gauge 1 is bonded to the strain body 110 with the resistor 30 facing the strain body 110 side.

The strain generating element 110 is formed of, for example, a metal such as Fe, SUS (stainless steel), or Al, or a resin such as PEEK, and is deformed according to an applied force, and transmits the generated strain to the strain gauge 1. It is. The strain gauge 1 can detect the strain generated in the strain body 110 as a change in the resistance value of the resistor 30.

The adhesive layer 120 is sandwiched between the strain gauge 1 and the strain body 110 and covers the resistor 30. The adhesive layer 120 is not particularly limited as long as it has a function of bonding the strain gauge 1 and the strain body 110, and can be appropriately selected depending on the purpose. For example, an epoxy resin, a modified epoxy resin, a silicone resin , Modified silicone resin, urethane resin, modified urethane resin and the like can be used. Further, a material such as a bonding sheet may be used. However, when the strain body 110 is a conductor, it is necessary to select an insulating material for the adhesive layer 120. The thickness of the adhesive layer 120 is not particularly limited and can be appropriately selected depending on the purpose. For example, the thickness can be about 0.1 μm to 50 μm.

In order to manufacture the strain gauge 1, first, the base material 10 is prepared, and the planar resistor 30 and the terminal portion 41 shown in FIG. 1 are formed on the lower surface 10b of the base material 10. The materials and thicknesses of the resistor 30 and the terminal portion 41 are as described above. The resistor 30 and the terminal 41 can be integrally formed of the same material.

The resistor 30 and the terminal portion 41 can be formed by, for example, forming a film by a magnetron sputtering method using a material capable of forming the resistor 30 and the terminal portion 41 as a target, and patterning the film by photolithography. The resistor 30 and the terminal portion 41 may be formed by a reactive sputtering method, an evaporation method, an arc ion plating method, a pulse laser deposition method, or the like instead of the magnetron sputtering method.

From the viewpoint of stabilizing the gauge characteristics, before forming the resistor 30 and the terminal portion 41, a function having a film thickness of about 1 nm to 100 nm as a base layer on the lower surface 10b of the base material 10 by, for example, a conventional sputtering method. Preferably, the layer is deposited in a vacuum. After the resistor 30 and the terminal 41 are formed on the entire lower surface of the functional layer, the functional layer is patterned by photolithography together with the resistor 30 and the terminal 41 into the planar shape shown in FIG.

において In the present application, the functional layer refers to a layer having a function of promoting crystal growth of at least the upper layer of the resistor 30. The functional layer preferably further has a function of preventing the resistor 30 from being oxidized by oxygen or moisture contained in the substrate 10 and a function of improving the adhesion between the substrate 10 and the resistor 30. The functional layer may further have another function.

Since the insulating resin film constituting the base material 10 contains oxygen and moisture, especially when the resistor 30 contains Cr, Cr forms a self-oxidized film, so that the functional layer has a function of preventing oxidation of the resistor 30. Providing is effective.

The material of the functional layer is not particularly limited as long as it has a function of promoting the crystal growth of the resistor 30 as the upper layer, 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), Fe (iron), Mo (molybdenum), W (tungsten), Ru (ruthenium), Rh (rhodium), Re (rhenium), Os (osmium), Ir ( Selected from the group consisting of iridium), Pt (platinum), Pd (palladium), Ag (silver), Au (gold), Co (cobalt), Mn (manganese), and Al (aluminum) One or more metals, or metal alloys of this group, or a compound of any one of metals of this group and the like.

Examples of the above alloy include FeCr, TiAl, FeNi, NiCr, CrCu and the like. Examples of the above compound include TiN, TaN, Si ₃ N ₄ , TiO ₂ , Ta ₂ O ₅ , and SiO ₂ .

The functional layer can be formed, for example, by a conventional sputtering method using a material capable of forming the functional layer as a target and introducing an Ar (argon) gas into the chamber. By using the conventional sputtering method, the functional layer is formed while etching the lower surface 10b of the base material 10 with Ar, so that the effect of improving the adhesion can be obtained by minimizing the amount of the functional layer formed.

However, this is an example of a method for forming a functional layer, and the functional layer may be formed by another method. For example, before the functional layer is formed, the lower surface 10b of the base material 10 is activated by plasma treatment using Ar or the like to obtain an adhesion improving effect, and then the functional layer is vacuum-formed by magnetron sputtering. May be used.

The combination of the material of the functional layer and the material of the resistor 30 and the terminal portion 41 is not particularly limited and can be appropriately selected depending on the purpose. For example, Ti is used for the functional layer, and the resistor 30 and the terminal portion 41 are used. It is possible to form a Cr mixed phase film containing α-Cr (alpha chromium) as a main component.

In this case, for example, the resistor 30 and the terminal portion 41 can be formed by a magnetron sputtering method using a raw material capable of forming a Cr mixed-phase film as a target and introducing Ar gas into the chamber. Alternatively, the resistor 30 and the terminal portion 41 may be formed by a reactive sputtering method by introducing an appropriate amount of nitrogen gas together with Ar gas into a chamber using pure Cr as a target.

According to 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 having α-Cr as a main component, which has a stable crystal structure, can be formed. Further, the gauge characteristics are improved by diffusing Ti constituting the functional layer into the Cr mixed phase film. For example, 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. When the functional layer is formed of Ti, the Cr mixed phase film may include Ti or TiN (titanium nitride).

When the resistor 30 is a Cr mixed phase film, the functional layer made of Ti has a function of promoting the crystal growth of the resistor 30 and a function of preventing the resistor 30 from being oxidized by oxygen or moisture contained in the base material 10. , And all the functions of improving the adhesion between the substrate 10 and the resistor 30. The same applies when Ta, Si, Al, or Fe is used instead of Ti as the functional layer.

As described above, by providing the functional layer below the resistor 30, the crystal growth of the resistor 30 can be promoted, and the resistor 30 having a stable crystal phase can be manufactured. As a result, in the strain gauge 1, the stability of the gauge characteristics can be improved. In addition, since the material forming the functional layer diffuses into the resistor 30, the gauge characteristics of the strain gauge 1 can be improved.

In the case where a functional layer is provided on the lower surface 10b of the base material 10 as a base layer of the resistor 30 and the terminal portion 41, the strain gauge 1 of the sensor module 5 has a sectional shape shown in FIG. The layer indicated by reference numeral 20 is a functional layer. The plane shape of the strain gauge 1 when the functional layer 20 is provided is the same as that in FIG.

In order to manufacture the sensor module 5, after producing the strain gauge 1, for example, any one of the above-described materials to be the adhesive layer 120 is applied to the lower surface 10 b of the base material 10 and / or the upper surface 110 a of the strain body 110. . Then, the lower surface 10b of the base material 10 faces the upper surface 110a of the strain body 110, and the strain gauge 1 is arranged on the strain body 110 with the applied material interposed therebetween. Alternatively, a bonding sheet may be sandwiched between the strain body 110 and the base material 10.

Next, the strain gauge 1 is heated to a predetermined temperature while being pressed against the strain generating element 110, and the applied material is cured to form the adhesive layer 120. As a result, the upper surface 110a of the strain body 110 and the lower surface 10b of the substrate 10 are bonded via the bonding layer 120, and the sensor module 5 is completed. The sensor module 5 can be applied to, for example, measurement of load, pressure, torque, acceleration, and the like.

As described above, in the sensor module 5, the strain gauge 1 is bonded to the strain body 110 with the resistor 30 facing the strain body 110. In other words, the upper surface side of the resistor 30 is covered with the base material 10. By covering the upper surface side of the resistor 30 with the base material 10, it is possible to prevent the resistor 30 from being mechanically damaged or the like. Further, by covering the upper surface side of the resistor 30 with the base material 10, the resistor 30 can be protected from moisture and the like.

By the way, as described above, in the conventional sensor module, a strain gauge in which a resistor and a protective film were formed on a substrate was produced, and the substrate side of the strain gauge was bonded to the strain generating element via an adhesive layer. Structure. In this case, in addition to the step of forming the resistor on the base material, a step of covering the resistor with a protective film is required, so that there is a problem that the cost of the sensor module using the strain gauge increases.

On the other hand, in the sensor module 5, the strain gauge 1 is bonded to the strain body 110 with the resistor 30 facing the strain body 110, and the upper surface of the resistor 30 is covered with the base material 10. ing. That is, in the sensor module 5, since the substrate 10 also functions as a protective film in the conventional sensor module, a step of covering the resistor with the protective film is not required, and the time required for manufacturing is reduced. Thereby, an increase in the cost of the sensor module 5 can be suppressed.

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

This international application claims priority based on Japanese Patent Application No. 2018-117747 filed on June 21, 2018, and the entire contents of Japanese Patent Application No. 2018-117747 are incorporated herein by reference. .

1 strain gauge, 5 sensor module, 10 base material, 10a upper surface, 10b lower surface, 20 functional layer, 30 resistor, 41 terminal part, 110 strain generator, 110a upper surface, 120 adhesive layer

Claims

A flexible base material, and a strain gauge including a resistor formed from a material containing at least one of chromium and nickel on the base material,
And a strain-generating body that transmits strain to the strain gauge,
A sensor module in which the strain gauge is bonded to the strain body with the resistor facing the strain body.
The sensor module according to claim 1, wherein the resistor is formed of a Cr mixed phase film.
The sensor module according to claim 2, wherein the resistor mainly includes alpha chrome.
4. The sensor module according to claim 3, wherein the resistor contains alpha chrome in an amount of 80% by weight or more.
The sensor module according to any one of claims 2 to 4, wherein the resistor includes chromium nitride.
6. The sensor module according to claim 1, further comprising a functional layer formed of a metal, an alloy, or a metal compound below the resistor. 7.
7. The sensor module according to claim 6, wherein the functional layer has a function of promoting crystal growth of the resistor.
An adhesive layer sandwiched between the strain gauge and the strain body,
The sensor module according to claim 1, wherein the adhesive layer covers the resistor.