Patent Description:
Strain gauges are known to be attached to measured objects to detect strain on the measured objects. Such a strain gauge includes a resistor that detects strain, and as resistor material, for example, material containing Cr (chromium) or Ni (nickel) is used. The resistor is formed on a substrate made of, for example, an insulating resin (see, for example, Patent document <NUM>).

However, when the strain gauge is used for a given measured object having great stiffness, the stain gauge is required to be highly sensitive. However, conventional strain gauges are less sensitive, and if a conventional strain gauge is used as a sensor, use of the sensor may be difficult for the measured object with the great stiffness.

In view of the point described above, an object of the present invention is to provide an accelerator and the like having a highly sensitive sensor. To this end, the invention is disclosed in claim <NUM>, dependent claims being directed to preferred embodiments.

An accelerator is an automobile accelerator. The accelerator includes a sensor configured to detect a force to press the accelerator. The sensor includes a flexible substrate and a resistor formed of a film containing Cr, CrN, and Cr<NUM>N, on or above the substrate. The sensor is configured to detect the force to press the accelerator as a change in a resistance value of the resistor.

According to the disclosed technique, an accelerator and the like having a highly sensitive sensor can be provided.

One or more embodiments will be hereinafter described with reference to the drawings. In each figure, the same numerals denote the same components, and duplicative description may be omitted.

<FIG> is a plan view of an example of a strain gauge according to a first embodiment. <FIG> is a cross-sectional view of an example of the strain gauge according to the first embodiment, and illustrates a cross section taken along the A-A line in <FIG>. With reference to <FIG>, the strain gauge <NUM> includes a substrate <NUM>, a functional layer <NUM>, a resistor <NUM>, terminal sections <NUM>, and a cover layer <NUM>. Note that in <FIG>, an outer edge of the cover layer <NUM> is only expressed by a dashed line in order to indicate the resistor <NUM>, for the sake of convenience.

Note that in the present embodiment, for the sake of convenience, with respect to the strain gauge <NUM>, the side of the substrate <NUM> where the resistor <NUM> is provided is referred to as an upper side or one side; and the side of the substrate <NUM> where the resistor <NUM> is not provided is referred to as a lower side or another side. Further, for each component, the surface on the side where the resistor <NUM> is provided is referred to as one surface or an upper surface; and the surface on the side where the resistor <NUM> is not provided is referred to as another surface or a lower surface. However, the strain gauge <NUM> can be used in a state of being upside down, or be disposed at any angle. Further, a plan view means that an object is viewed from the direction normal to an upper surface 10a of the substrate <NUM>, and a planar shape refers to a shape of an object when viewed from the direction normal to the upper surface 10a of the substrate <NUM>.

The substrate <NUM> is a member that is a base layer for forming the resistor <NUM> or the like and is flexible. The thickness of the substrate <NUM> is not particularly restricted, and can be appropriately selected for any purpose. For example, such a thickness can be approximately between <NUM> and <NUM>. In particular, when the thickness of the substrate <NUM> is between <NUM> and <NUM>, it is preferable in terms of strain transfer from a flexure element surface that is bonded to a lower surface of the substrate <NUM> via an adhesive layer or the like; and dimensional stability with respect to environment, and when the thickness is <NUM> or more, it is further preferable in terms of insulation.

The substrate <NUM> can be formed of an insulating resin film such as a PI (polyimide) resin, an epoxy resin, a PEEK (polyether ether ketone) resin, a PEN (polyethylene naphthalate) resin, a PET (polyethylene terephthalate) resin, a PPS (polyphenylene sulfide) resin, or a polyolefin resin. Note that the film refers to a flexible member having a thickness of about <NUM> or less.

Here, the "formed of an insulating resin film" is not intended to preclude the substrate <NUM> from containing fillers, impurities, or the like in the insulating resin film. The substrate <NUM> may be formed of, for example, an insulating resin film containing fillers such as silica or alumina.

Except for resin, examples of the material of the substrate <NUM> include Sio<NUM>, ZrO<NUM> (including YSZ), Si, Si<NUM>N<NUM>, Al<NUM>O<NUM> (including a sapphire), ZnO, perovskite ceramic (CaTiO<NUM> or BaTiO<NUM>), and the like. As the material of the substrate <NUM>, metal such as aluminum, an aluminum alloy (duralumin), or titanium, may be also used. In this case, for example, an insulating film is formed on a metallic substrate <NUM>.

The functional layer <NUM> is formed, as a lower layer of the resistor <NUM>, on the upper surface 10a of the substrate <NUM>. In other words, a planar shape of the functional layer <NUM> is approximately the same as the planar shape of the resistor <NUM> illustrated in <FIG>. The thickness of the functional layer <NUM> can be approximately between <NUM> and <NUM>, for example.

In the present application, the functional layer refers to a layer that has a function of promoting crystal growth of the resistor <NUM> that is at least an upper layer. The functional layer <NUM> preferably further has a function of preventing oxidation of the resistor <NUM> caused by oxygen and moisture included in the substrate <NUM>, as well as a function of improving adhesion between the substrate <NUM> and the resistor <NUM>. The functional layer <NUM> may further have other functions.

The insulating resin film that constitutes the substrate <NUM> contains oxygen and moisture. In this regard, particularly when the resistor <NUM> includes Cr (chromium), it is effective for the functional layer <NUM> to have a function of preventing oxidation of the resistor <NUM>, because Cr forms an autoxidized film.

The material of the functional layer <NUM> is not particularly restricted as long as it is material having a function of promoting crystal growth of the resistor <NUM> that is at least an upper layer. Such material can be appropriately selected for any purpose, and includes one or more types of metals selected from the group consisting of, 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), and Al (aluminum); an alloy of any metals from among the group; or a compound of any metal from among the group.

Examples of the above alloy include FeCr, TiAl, FeNi, NiCr, CrCu, and the like. Examples of the above compound include TiN, TaN, Si<NUM>N<NUM>, TiO<NUM>, Ta<NUM>O<NUM>, SiO<NUM>, and the like.

The resistor <NUM> is a thin film formed in a predetermined pattern and above the upper surface of the functional layer <NUM>, and is a sensitive section where resistance varies according to strain. Note that in <FIG>, for the sake of convenience, the resistor <NUM> is illustrated in a crepe pattern.

The resistor <NUM> can be formed of, for example, material including Cr (chromium), material including Ni (nickel), or material including both of Cr and Ni. In other words, the resistor <NUM> can be formed of material including at least one among Cr and Ni. An example of the material including Cr includes a Cr composite film. An example of the material including nickel includes Cu-Ni (copper nickel). An example of the material including both of Cr and Ni includes Ni-Cr (nickel chromium).

Here, the Cr composite film is a composite film of Cr, CrN, Cr<NUM>N, and the like. The Cr composite film may include incidental impurities such as chromium oxide. A portion of the material that constitutes the functional layer <NUM> is diffused into the Cr composite film. The material that constitutes the functional layer <NUM>, and nitrogen may form a compound. For example, when the functional layer <NUM> is formed of Ti, the Cr composite film may include Ti or TiN (titanium nitride).

The thickness of the resistor <NUM> is not particularly restricted, and can be appropriately selected for any purpose. The thickness can be, for example, approximately between <NUM> and <NUM>. In particular, when the thickness of the resistor <NUM> is <NUM> or more, it is preferable in terms of improvement in crystallinity (e.g., crystallinity of α-Cr) of a crystal that constitutes the resistor <NUM>, and when the thickness of the resistor <NUM> is <NUM> or less, it is further preferable in terms of reduction in cracks of a given film caused by internal stress of the film that constitutes the resistor <NUM>, or reduction in warp in the substrate <NUM>.

With the resistor <NUM> being formed on the functional layer <NUM>, the resistor <NUM> can be formed by a stable crystalline phase and thus stability of gauge characteristics (a gauge factor, a gauge factor temperature coefficient TCS, and a temperature coefficient of resistance TCR) can be improved.

For example, when the resistor <NUM> is the Cr composite film, in a case of providing the functional layer <NUM>, the resistor <NUM> can be formed with α-Cr (alpha-chromium) as the main component. Because α-Cr has a stable crystalline phase, the stability of the gauge characteristics can be improved.

Here, a main component means that a target substance has <NUM>% by weight or more of total substances that constitute the resistor. When the resistor <NUM> is the Cr composite film, the resistor <NUM> preferably includes α-Cr of <NUM>% by weight or more, from the viewpoint of improving the gauge characteristics. Note that α-Cr is Cr having a bcc structure (body-centered cubic structure).

Also, by diffusing a metal (e.g., Ti) that constitutes the functional layer <NUM> into the Cr composite film, the gauge characteristics can be improved. Specifically, the gauge factor of the strain gauge <NUM> can be <NUM> or more, as well as the gauge factor temperature coefficient TCS and temperature coefficient of resistance TCR being able to be each in the range of from -<NUM> ppm/°C to +<NUM> ppm/°C.

Note that the expansion coefficient of the substrate <NUM> is preferably between <NUM> ppm/K and <NUM> ppm/K, from the viewpoint of reducing warp in the substrate <NUM>, where the internal stress of the resistor <NUM> is assumed to be close to zero. The expansion coefficient of the substrate <NUM> can be adjusted by, for example, selecting the material of the substrate <NUM>, selecting the material of the filler contained in the substrate <NUM>, adjusting the content, and the like.

When the resistor <NUM> is formed above the substrate <NUM>, pinholes may be generated in the resistor <NUM>. If the number of pinholes generated in the resistor <NUM> exceeds a predetermined value, the gauge characteristics might deteriorate, or the resistor might not serve as a strain gauge. The inventors have recognized that one cause of the pinhole generated in the resistor <NUM> relates to filler protruding from the upper surface 10a of the substrate <NUM>.

In other words, when the substrate <NUM> includes a filler, a portion of the filler protrudes from the upper surface 10a of the substrate <NUM>, so that surface unevenness on the upper surface 10a of the substrate <NUM> increases. As a result, the number of pinholes generated in the resistor <NUM> formed above the upper surface 10a of the substrate <NUM> increases, which results in deterioration of the gauge characteristics, and the like.

The inventors have found that, when the thickness of the resistor <NUM> is <NUM> or more, in a case where the surface unevenness on the upper surface 10a of the substrate <NUM> is <NUM> or less, the number of pinholes generated in the resistor <NUM> can be suppressed to maintain the gauge characteristics.

In other words, when the thickness of the resistor <NUM> is <NUM> or more, the surface unevenness on the upper surface 10a of the substrate <NUM> is preferably <NUM> or less, from the viewpoint of reducing the number of pinholes generated in the resistor <NUM> that is formed above the upper surface 10a of the substrate <NUM> to maintain the gauge characteristics. When the surface unevenness is <NUM> or less, even in a case where the substrate <NUM> includes fillers, the gauge characteristics do not deteriorate. Note that the surface unevenness on the upper surface 10a of the substrate <NUM> may be <NUM>.

The surface unevenness on the upper surface 10a of the substrate <NUM> can be reduced by, for example, heating the substrate <NUM>. Alternatively, instead of heating of the substrate <NUM>, a method of scraping a protrusion by approximately vertically irradiating the upper surface 10a of the substrate <NUM> with laser light, a method of cutting a protrusion by moving a water cutter or the like to be parallel to the upper surface 10a of the substrate <NUM>, a method of polishing the upper surface 10a of the substrate <NUM> with a grinding wheel, a method of pressing the substrate <NUM> while heating (heat press), or the like, may be used.

Note that the surface unevenness means arithmetical mean roughness, and is generally expressed by Ra. The surface unevenness can be measured by, for example, three-dimensional optical interferometry.

The terminal sections <NUM> respectively extend from both end portions of the resistor <NUM> and are each wider than the resistor <NUM> to be in an approximately rectangular shape, in a plan view. The terminal sections <NUM> are a pair of electrodes from which a change in a resistance value of the resistor <NUM> according to strain is output externally, where, for example, a lead wire for an external connection, or the like is joined. For example, the resistor <NUM> extends from one of the terminal sections <NUM>, with zigzagged hairpin turns, to be connected to another terminal section <NUM>. The upper surface of each terminal section <NUM> may be coated with a metal allowing for greater solderability than the terminal section <NUM>. Note that for the sake of convenience, the resistor <NUM> and the terminal sections <NUM> are expressed by different numerals. However, the resistor and the terminal sections can be integrally formed of the same material, in the same process.

The cover layer <NUM> is an insulating resin layer, which is disposed on and above the upper surface 10a of the substrate <NUM>, such that the resistor <NUM> is coated and the terminal sections <NUM> are exposed. With the cover layer <NUM> being provided, mechanical damage, and the like can be prevented from occurring in the resistor <NUM>. Additionally, with the cover layer <NUM> being provided, the resistor <NUM> can be protected against moisture, and the like. Note that the cover layer <NUM> may be provided to cover all portions except for the terminal sections <NUM>.

The cover layer <NUM> can be formed of an insulating resin such as a PI resin, an epoxy resin, a PEEK resin, a PEN resin, a PET resin, or a PPS resin, a composite resin (e.g., a silicone resin or a polyolefin resin). The cover layer <NUM> may contain fillers or pigments. The thickness of the cover layer <NUM> is not particularly restricted, and can be appropriately selected for any purpose. For example, the thickness may be approximately between <NUM> and <NUM>.

<FIG> are diagrams illustrating the process of manufacturing the strain gauge according to the first embodiment, and each illustrate a cross section corresponding to <FIG>. In order to manufacture the strain gauge <NUM>, first, in the process illustrated in <FIG>, the substrate <NUM> is prepared and the functional layer <NUM> is formed on the upper surface 10a of the substrate <NUM>. The material and thickness for each of the substrate <NUM> and the functional layer <NUM> are the same as the material and thickness described above.

The functional layer <NUM> can be vacuum-deposited by, for example, conventional sputtering in which a raw material capable of forming the functional layer <NUM> is the target and in which an Ar (argon) gas is supplied to a chamber. By using conventional sputtering, the functional layer <NUM> is deposited while the upper surface 10a of the substrate <NUM> is etched with Ar. Thus, a deposited amount of film of the functional layer <NUM> is minimized and thus an effect of improving adhesion can be obtained.

However, this is an example of a method of depositing the functional layer <NUM>, and the functional layer <NUM> may be formed by other methods. For example, before depositing the functional layer <NUM>, the upper surface 10a of the substrate <NUM> is activated by plasma treatment or the like using Ar, etc. to thereby obtain the effect of improving the adhesion, and subsequently, the functional layer <NUM> may be vacuum-deposited by magnetron sputtering.

Next, in the process illustrated in <FIG>, the resistor <NUM> and the terminal sections <NUM> are formed on the entire upper surface of the functional layer <NUM>, and then the functional layer <NUM>, the resistor <NUM>, and the terminal sections <NUM> are each patterned in the planar shape as illustrated in <FIG>, by photolithography. The material and thickness for each of the resistor <NUM> and the terminal sections <NUM> are the same as the material and thickness described above. The resistor <NUM> and the terminal sections <NUM> can be integrally formed of the same material. The resistor <NUM> and the terminal sections <NUM> can be deposited by, for example, magnetron sputtering in which a raw material capable of forming the resistor <NUM> and the terminal sections <NUM> is a target. Instead of the magnetron sputtering, the resistor <NUM> and the terminal sections <NUM> may be deposited by reactive sputtering, vapor deposition, arc ion plating, pulsed laser deposition, or the like.

A combination of the material of the functional layer <NUM> and the material of the resistor <NUM> and the terminal sections <NUM> is not particularly restricted, and can be appropriately selected for any purpose. For example, Ti is used for the functional layer <NUM>, and a Cr composite film formed with α-Cr (alpha-chromium) as the main component can be deposited as the resistor <NUM> and the terminal sections <NUM>.

In this case, each of the resistor <NUM> and the terminal sections <NUM> can be deposited by, for example, magnetron sputtering in which a raw material capable of forming the Cr composite film is the target and in which an Ar gas is supplied to a chamber. Alternatively, the resistor <NUM> and the terminal sections <NUM> may be deposited by reactive sputtering in which pure Cr is the target and in which an appropriate amount of nitrogen gas, as well as an Ar gas, are supplied to a chamber.

In such methods, a growth face of the Cr composite film is defined by the functional layer <NUM> formed of Ti, and a Cr composite film formed with α-Cr as the main component having a stable crystalline structure can be deposited. Also, Ti that constitutes the functional layer <NUM> is diffused into the Cr composite film, so that the gauge characteristics are improved. For example, the gauge factor of the strain gauge <NUM> can be <NUM> or more, as well as the gauge factor temperature coefficient TCS and temperature coefficient of resistance TCR can be each in the range of from -<NUM> ppm/°c to +<NUM> ppm/°C.

Note that when the resistor <NUM> is a Cr composite film, the functional layer <NUM> formed of Ti includes all functions of a function of promoting crystal growth of the resistor <NUM>, a function of preventing oxidation of the resistor <NUM> caused by oxygen or moisture contained in the substrate <NUM>, and a function of improving adhesion between the substrate <NUM> and the resistor <NUM>. Instead of Ti, when the functional layer <NUM> is formed of Ta, Si, Al, or Fe, the functional layer also includes the same functions.

Next, in the process illustrated in <FIG>, the cover layer <NUM> is formed on and above the upper surface 10a of the substrate <NUM>, such that the resistor <NUM> is coated and the terminal sections <NUM> are exposed. The material and thickness of the cover layer <NUM> are the same as the material and thickness described above. For example, the cover layer <NUM> can be fabricated, such that a thermosetting insulating resin film in a semi-cured state is laminated on the upper surface 10a of the substrate <NUM>, and such that the resistor <NUM> is coated and the terminal sections <NUM> are exposed; subsequently, heat is added and curing is performed. The cover layer <NUM> may be formed, such that a thermosetting insulating resin that is liquid or paste-like is applied to the upper surface 10a of the substrate <NUM>, and such that the resistor <NUM> is coated and the terminal sections <NUM> are exposed; subsequently, heat is added and curing is performed. In the above process, the strain gauge <NUM> is completed.

As described above, with the functional layer <NUM> being provided in the lower layer of the resistor <NUM>, the crystal growth of the resistor <NUM> can be promoted and thus the resistor <NUM> having a stable crystalline phase can be fabricated. As a result, with respect to the strain gauge <NUM>, the stability of the gauge characteristics can be improved. Also, the material that constitutes the functional layer <NUM> is diffused into the resistor <NUM>, so that the gauge characteristics of the strain gauge <NUM> can be thereby improved.

First modification of the first embodiment provides an example of a strain gauge in which an insulating layer is provided in a lower layer of the cover layer. Note that in the first modification of the first embodiment, the description for the same components as the embodiment that has been described may be omitted.

<FIG> is a cross-sectional view illustrating an example of the strain gauge according to the first modification of the first embodiment, and illustrates a cross section corresponding to <FIG>. With reference to <FIG>, the strain gauge 1A differs from the strain gauge <NUM> (see <FIG>, etc.) in that an insulating layer <NUM> is provided in the lower layer of the cover layer <NUM>. Note that the cover layer <NUM> may be provided to cover all portions except for the terminal sections <NUM>.

The insulating layer <NUM> is provided on and above the upper surface 10a of the substrate <NUM>, such that the resistor <NUM> is coated and the terminal sections <NUM> are exposed. For example, the cover layer <NUM> can be provided to cover a portion of a side surface of the insulating layer <NUM>, and an upper surface thereof.

The material of the insulating layer <NUM> is not particularly restricted as long as the material has higher resistance than the resistor <NUM> and the cover layer <NUM>. The material can be appropriately selected for any purpose. For example, an oxide or a nitride, such as Si, W, Ti, or Ta, can be used. The thickness of the insulating layer <NUM> is not particularly restricted, and can be appropriately selected for any purpose. For example, the thickness can be approximately between <NUM> and <NUM>.

The method of forming the insulating layer <NUM> is not particularly restricted, and can be appropriately selected for any purpose. For example, a vacuum process such as sputtering or chemical vapor deposition (CVD), or, a solution process such as spin coating or a sol-gel process can be used.

In such a manner, with the insulating layer <NUM> being provided in the lower layer of the cover layer <NUM>, insulation and environmental sealing can be improved in comparison to the case where the cover layer <NUM> alone is used. In such a manner, the insulating layer <NUM> can be appropriately provided according to a specification required for the insulation and environmental sealing.

The second embodiment provides an example of a strain gauge in which each electrode has a laminated structure. Note that in the second embodiment, the description for the same components as the embodiment that has been described may be omitted.

<FIG> is a plan view illustrating an example of a strain gauge according to the second embodiment. <FIG> is a cross-sectional view illustrating an example of the strain gauge according to the second embodiment, and illustrates a cross section taken along the line B-B in <FIG>. With reference to <FIG> and <FIG>, the strain gauge <NUM> includes electrodes 40A in each of which a plurality of layers are laminated. Note that the cover layer <NUM> may be provided to cover all portions except for the electrodes 40A.

Each electrode 40A has a laminated structure in which a plurality of metallic layers are laminated. Specifically, each electrode 40A includes a terminal section <NUM> extending from a corresponding end portion from among both end portions of the resistor <NUM>; a metallic layer <NUM> formed on an upper surface of the terminal section <NUM>, a metallic layer <NUM> formed on an upper surface of the metallic layer <NUM>, and a metallic layer <NUM> formed on an upper surface of the metallic layer <NUM>. The metallic layer <NUM> is a typical example of a first metallic layer according to the present disclosure, and the metallic layer <NUM> is a typical example of a second metallic layer according to the present disclosure.

The material of the metallic layer <NUM> is not particularly restricted, and can be appropriately selected for any purpose. For example, Cu (copper) can be used. The thickness of the metallic layer <NUM> is not particularly restricted, and can be appropriately selected for any purpose. For example, the thickness can be approximately between <NUM> and <NUM>.

Preferably, the material of the metallic layer <NUM> includes Cu, a Cu alloy, Ni, or a Ni alloy. The thickness of the metallic layer <NUM> is determined in consideration of solderability to the electrode 40A, and is preferably <NUM> or more, and more preferably <NUM> or more. When the material of the metallic layer <NUM> includes Cu, a Cu alloy, Ni, or a Ni alloy and the thickness of the metallic layer <NUM> is <NUM> or more, dissolution of metallization is ameliorated. Also, when the material of the metallic layer <NUM> includes Cu, a Cu alloy, Ni, or a Ni alloy and the thickness of the metallic layer <NUM> is <NUM> or more, dissolution of metallization is further ameliorated. Note that the thickness of the metallic layer <NUM> is preferably <NUM> or less in terms of ease of electrolytic plating.

Here, the dissolution of metallization means that the material constituting the electrode 40A is dissolved in solder for jointing the electrode 40A, and that the thickness of the electrode 40A is reduced or the material disappears. When the dissolution of metallization occurs, adhesion strength or tensile strength with a lead wire, or the like to be jointed to the electrode 40A may be reduced. Thus, it is preferable that no dissolution of metallization occur.

For the material of the metallic layer <NUM>, material having better solder wettability than the metallic layer <NUM> can be selected. For example, when the material of the metallic layer <NUM> includes Cu, a Cu alloy, Ni, or a Ni alloy, the material of the metallic layer <NUM> can include Au (gold). When the surface of Cu, a Cu alloy, Ni, or a Ni alloy is coated with Au, oxidation and corrosion for Cu, a Cu alloy, Ni, or a Ni alloy can be prevented, as well as great solder wettability being able to be provided. Instead of Au, when the material of the metallic layer <NUM> includes Pt (platinum), the metallic layer <NUM> has the same effect. The thickness of the metallic layer <NUM> is not particularly restricted, and can be appropriately selected for any purpose. For example, the thickness can be approximately between <NUM> and <NUM>.

Note that each terminal section <NUM> is exposed around a given laminated section of the metallic layers <NUM>, <NUM>, and <NUM>, in a plan view. However, each terminal section <NUM> may have the same planar shape as the laminated section of the metallic layers <NUM>, <NUM>, and <NUM>.

<FIG> illustrate a process of manufacturing a strain gauge according to a second embodiment, and illustrate a cross section corresponding to <FIG>. In order to manufacture the strain gauge <NUM>, a process that is similar to that in <FIG> according to the first embodiment is first performed, and then in the process illustrated in <FIG>, a metallic layer <NUM> is formed on an upper surface of the functional layer <NUM>. The metallic layer <NUM> is a layer that is finally patterned to serve as the resistor <NUM> and terminal sections <NUM>. In such a manner, the material and thickness of the metallic layer <NUM> are the same as the material and thickness for each of the above resistor <NUM> and terminal sections <NUM>.

The metallic layer <NUM> can be deposited by magnetron sputtering in which, for example, a raw material capable of forming the metallic layer <NUM> is the target. Instead of the magnetron sputtering, the metallic layer <NUM> may be deposited by reactive sputtering, vapor deposition, arc ion plating, pulsed laser deposition, or the like.

Next, in the process illustrated in <FIG>, a seed layer <NUM> as the metallic layer <NUM> is formed by, for example, sputtering, electroless plating, or the like, to cover an upper surface of the metallic layer <NUM>.

Next, in the process illustrated in <FIG>, a photosensitive resist <NUM> is formed on the entire upper surface of the seed layer <NUM>, and by exposing and developing, an opening 800x for exposing a region in which each electrode 40A is to be formed is formed. As the resist <NUM>, for example, a dry film resist, or the like can be used.

Next, in the process illustrated in <FIG>, a given metallic layer <NUM> is formed on the seed layer <NUM> that is exposed in the opening 800x, by for example, electrolytic plating in which the seed layer <NUM> is set as a power supply path, and further, a given metallic layer <NUM> is formed on the metallic layer <NUM>. The electrolytic plating is suitable because it has high takt and allows for formation of a low stress electrolytic plating layer as the metallic layer <NUM>. When the electrolytic plating layer whose thickness is increased has low stress, warp in the strain gauge <NUM> can be prevented. Note that the metallic layer <NUM> may be formed on the metallic layer <NUM>, by electroless plating.

Note that in forming the metallic layer <NUM>, side surfaces of the metallic layer <NUM> are coated with the resist <NUM>, so that the metallic layer <NUM> is formed only on the upper surface of the metallic layer <NUM> and is not on the side surfaces thereof.

Next, in the process illustrated in <FIG>, the resist <NUM> illustrated in <FIG> is removed. The resist <NUM> can be removed by, for example, immersing the material of the resist <NUM> in a dissolvable solution.

Next, in the process illustrated in <FIG>, a photosensitive resist <NUM> is formed on the entire upper surface of the seed layer <NUM>, and by exposing and developing, a planar shape that is the same as that of the resistor <NUM> and terminal sections <NUM> in <FIG> is patterned. As the resist <NUM>, for example, a dry film resist, or the like can be used.

Next, in the process illustrated in <FIG>, the resist <NUM> is used as an etch mask, and the functional layer <NUM>, the metallic layer <NUM>, and the seed layer <NUM> that are exposed from the resist <NUM> are removed, so that the functional layer <NUM>, the resistor <NUM>, and the terminal sections <NUM> each of which has the planar shape in <FIG> are formed. For example, with wet etching, unwanted portions of the functional layer <NUM>; the metallic layer <NUM>; and the seed layer <NUM> can be removed. Note that at this point, the seed layer <NUM> is formed on the resistor <NUM>.

Next, in the process illustrated in <FIG>, the metallic layer <NUM> and the metallic layer <NUM> are used as etch masks, and an unwanted seed layer <NUM> that is exposed from the metallic layer <NUM> and the metallic layer <NUM> is removed, so that the metallic layer <NUM> is formed. For example, by wet etching using etching liquid with which the seed layer <NUM> is etched and with which the functional layer <NUM> and the resistor <NUM> are not etched, the unwanted seed layer <NUM> can be removed.

After the process illustrated in <FIG>, as is the case with the process in <FIG>, the cover layer <NUM> with which the resistor <NUM> is coated and that exposes the electrodes 40A is formed on and above the upper surface 10a of the substrate <NUM>, so that the strain gauge <NUM> is completed.

As described above, as each electrode 40A, a given metallic layer <NUM> formed of a thick film (<NUM> or more), which is formed of Cu, a Cu alloy, Ni, or a Ni alloy, is formed above a given terminal section <NUM>, and further, a given metallic layer <NUM> formed of material (Au or Pt) that has better solder wettability than the metallic layer <NUM> is formed in the outermost surface layer. Thereby, dissolution of metallization can be prevented, as well as improving solder wettability.

First modification of the second embodiment provides an example of electrodes each having a layer structure different from that in the second embodiment. Note that in the first modification of the second embodiment, the description for the same components as the embodiments that have been described may be omitted.

<FIG> is a cross-sectional view illustrating an example of a strain gauge according to the first modification of the second embodiment, and illustrates a cross section corresponding to <FIG>. With reference to <FIG>, the strain gauge 2A differs from the strain gauge <NUM> (see <FIG>, etc.) in that the electrodes 40A are replaced with electrodes 40B. Additionally, the cover layer <NUM> is provided to approximately cover all portions except for the electrodes 40B, which differs from the strain gauge <NUM> (see <FIG>, etc.).

Each electrode 40B has a laminated structure in which a plurality of metallic layers are laminated. Specifically, each electrode 40B includes a terminal section <NUM> extending from a corresponding end portion from among both end portions of the resistor <NUM>, a metallic layer <NUM> formed on an upper surface of the terminal section <NUM>, a metallic layer <NUM> formed on an upper surface of the metallic layer <NUM>, a metallic layer <NUM> formed on an upper surface of the metallic layer <NUM>, and a metallic layer <NUM> formed on an upper surface of the metallic layer <NUM>. In other words, each electrode 40B has a structure in which the metallic layer <NUM> is provided between the metallic layer <NUM> and the metallic layer <NUM> of a given electrode 40A.

The material of the metallic layer <NUM> is not particularly restricted, and can be appropriately selected for any purpose. For example, Ni can be used. Instead of Ni, NiP (nickel phosphorus) or Pd may be used. Also, as the metallic layer <NUM>, Ni/Pd (a metallic layer in which a Ni layer and a Pd layer are laminated in this order) may be used. The thickness of the metallic layer <NUM> is not particularly restricted, and can be appropriately selected for any purpose. For example, the thickness can be approximately between <NUM> and <NUM>.

In the process illustrated in <FIG>, the metallic layer <NUM> can be formed on the metallic layer <NUM> by, for example, electrolytic plating in which the seed layer <NUM> is set as a power supply path.

In such a manner, the number of electrode layers is not particularly restricted, and the number of layers may be increased as necessary. In this case as well, a given metallic layer <NUM> formed of a thick film (<NUM> or more), which is formed of Cu, a Cu alloy, Ni, or a Ni alloy, is formed above a given terminal section <NUM>, and further, a given metallic layer <NUM> formed of material (Au or Pt) that has better solder wettability than the metallic layer <NUM> is formed in the outermost surface layer. Thereby, as is the case with the second embodiment, the dissolution of metallization can be prevented, as well as improving the solder wettability.

Second modification of the second embodiment provides another example of electrodes each having a different layer structure from that in the second embodiment. Note that in the second modification of the second embodiment, the description for the same components as the embodiments that have been described may be omitted.

<FIG> is a cross-sectional view illustrating an example of a strain gauge according to the second modification of the second embodiment, and illustrates a cross section corresponding to <FIG>. With reference to <FIG>, the strain gauge 2B differs from the strain gauge 2A (see <FIG>) in that the electrodes 40B are replaced with electrodes 40C. Additionally, the cover layer <NUM> is provided to approximately cover all portions except for the electrodes 40C, which differs from the strain gauge <NUM> (see <FIG>, and the like).

Each electrode 40C has a laminated structure in which a plurality of metallic layers are laminated. Specifically, each electrode 40C includes a terminal section <NUM> extending from a corresponding end portion from among both end portions of the resistor <NUM>, a metallic layer <NUM> formed on an upper surface of the terminal section <NUM>, a metallic layer <NUM> formed on an upper surface of the metallic layer <NUM>, a metallic layer 45A formed on an upper surface and side surfaces of the metallic layer <NUM> and on side surfaces of the metallic layer <NUM>, and a metallic layer 44A formed on an upper surface and side surfaces of the metallic layer 45A. For example, the material and thickness for each of the metallic layers 44A and 45A can be the same as the material and thickness of the metallic layers <NUM> and <NUM>. Note that the metallic layer 44A is a typical example of a second metallic layer according to the present disclosure.

In order to form each electrode 40C, first, in the process illustrated in <FIG>, for example, a given metallic layer <NUM> is formed by, for example, electrolytic plating in which the seed layer <NUM> is set as a power supply path, and then the resist <NUM> is removed as is the case with the process illustrated in <FIG>, without forming a given metallic layer <NUM>. Next, the same process as that in <FIG> is performed. Subsequently, a given metallic layer 45A can be formed on the upper surface and side surfaces of the metallic layer <NUM> and on the side surfaces of the metallic layer <NUM>, by electroless plating, for example. Additionally, a given metallic layer 44A can be formed on the upper surface and side surfaces of the metallic layer 45A, by electroless plating, for example.

As described above, each electrode can be fabricated by appropriately using both of electrolytic plating and electroless plating. In the structure of each electrode 40C, a given metallic layer <NUM> formed of a thick film (<NUM> or more), which is formed of Cu, a Cu alloy, Ni, or a Ni alloy, is formed above a given terminal section <NUM>, and further, a given metallic layer 44A formed of material (Au or Pt) that has better solder wettability than the metallic layer <NUM> is formed in the outermost layer. Note, however, that the metallic layer 44A of the outermost layer is formed, via the metallic layer 45A, toward the side surfaces of each of the metallic layers <NUM> and <NUM>, in addition to the upper surface of the metallic layer <NUM>. Thus, in comparison to the electrodes 40A or the electrodes 40B, the effect of preventing oxidation and corrosion of Cu, a Cu alloy, Ni, or a Ni alloy that constitutes the metallic layer <NUM> can be further enhanced, as well as the solder wettability can be further improved.

Note that the same effect is obtained even when a given metallic layer 44A is formed directly on the upper surface and side surfaces of a given metallic layer <NUM> and on the side surfaces of a given metallic layer <NUM>, without forming a given metallic layer 45A. In other words, the metallic layer 44A may directly or indirectly cover the upper surface and side surfaces of the metallic layer <NUM> and the side surfaces of the metallic layer <NUM>.

A third embodiment provides an example of a sensor module using a strain gauge. Note that in the third embodiment, the description for the same components as the embodiments that have been described may be omitted.

<FIG> is a cross-sectional view illustrating an example of the sensor module according to the third embodiment, and illustrates a cross section corresponding to <FIG>. With reference to <FIG>, the sensor module <NUM> includes the strain gauge <NUM>, a flexure element <NUM>, and an adhesive layer <NUM>. Note that the cover layer <NUM> may be provided to cover all portions except for the terminal sections <NUM>.

In the sensor module <NUM>, an upper surface 110a of the flexure element <NUM> is secured to the lower surface 10b of the substrate <NUM>, via the adhesive layer <NUM>. For example, the flexure element <NUM> is an object that is formed of a metal such as Fe, SUS (stainless steel), or Al, or, a resin such as PEEK, and that is deformed (causes strain) according to an applied force. The strain gauge <NUM> can detect strain generated in the flexure element <NUM>, as a change in a resistance value of the resistor <NUM>.

The material of the adhesive layer <NUM> is not particularly restricted as long as it has a function of securing the flexure element <NUM> to the strain gauge <NUM>. The material can be appropriately selected for any purpose. For example, an epoxy resin, a modified epoxy resin, a silicone resin, a modified silicone resin, a urethane resin, a modified urethane resin, or the like can be used. Also, material such as a bonding sheet may be used. The thickness of the adhesive layer <NUM> is not particularly restricted, and can be appropriately selected for any purpose. For example, the thickness can be approximately between <NUM> and <NUM>.

In order to manufacture the sensor module <NUM>, after the strain gauge <NUM> is fabricated, for example, any material described above, which constitutes the adhesive layer <NUM>, is applied to the lower surface 10b of the substrate <NUM> and/or the upper surface 110a of the flexure element <NUM>. Then, the lower surface 10b of the substrate <NUM> is situated facing the upper surface 110a of the flexure element <NUM>, and the strain gauge <NUM> is disposed above the flexure element <NUM>, through the applied material. Alternatively, the bonding sheet may be interposed between the flexure element <NUM> and the substrate <NUM>.

Next, the strain gauge <NUM> is heated to a predetermined temperature while being pressed toward the flexure element <NUM>, and the applied material is cured, so that the adhesive layer <NUM> is formed. Thereby, the lower surface 10b of the substrate <NUM> is secured to the upper surface 110a of the flexure element <NUM>, through the adhesive layer <NUM>, so that the sensor module <NUM> is completed. For example, the sensor module <NUM> can be applied in measurement of load, pressure, torque, acceleration, or the like.

Note that for the sensor module <NUM>, the strain gauge 1A, <NUM>, 2A, or 2B may be used instead of the strain gauge <NUM>.

First, in an advance test, Ti as the functional layer <NUM> was vacuum-deposited on the upper surface 10a of the substrate <NUM> formed of a polyimide resin that had a thickness of <NUM>, by conventional sputtering. In this case, five samples for each of which Ti was deposited were fabricated in order to target multiple film thicknesses.

Next, for the fabricated five samples, X-ray fluorescence (XRF) analysis was performed to obtain the result as illustrated in <FIG>. From an X-ray peak in <FIG>, it was confirmed that Ti was present, and from X-ray intensity of each sample at the X-ray peak, it was confirmed that a film thickness of a given Ti film could be controlled to be in the range of from <NUM> to <NUM>.

Next, in Example <NUM>, Ti as the functional layer <NUM>, which had a film thickness of <NUM>, was vacuum-deposited on the upper surface 10a of the substrate <NUM> formed of a polyimide resin that had a thickness of <NUM>, by conventional sputtering.

Subsequently, a Cr composite film, as the resistor <NUM> and the terminal sections <NUM>, was deposited on the entire upper surface of the functional layer <NUM>, by magnetron sputtering, and then the functional layer <NUM>, the resistor <NUM>, and the terminal sections <NUM> were patterned by photolithography, as illustrated in <FIG>.

In comparative example <NUM>, without forming the functional layer <NUM>, a Cr composite film, as the resistor <NUM> and the terminal sections <NUM>, was deposited on the upper surface 10a of the substrate <NUM> formed of a polyimide resin that had a thickness of <NUM>, by magnetron sputtering. Then, patterning was performed by photolithography, as illustrated in <FIG>. Note that for the sample used in Example <NUM> and the sample used in comparative example <NUM>, all deposition conditions for the resistor <NUM> and the terminal sections <NUM> are the same.

Next, for a given sample used in Example <NUM> and a given sample used in comparative example <NUM>, X-ray diffraction evaluation was performed to obtain the result illustrated in <FIG> illustrates an X-ray diffraction pattern at a diffraction angle of 2θ being in the range of from <NUM> to <NUM> degrees, and a diffraction peak in Example <NUM> is shifted to the right in comparison to a diffraction peak in comparative example <NUM>. Further, the diffraction peak in Example <NUM> is greater than the diffraction peak in comparative example <NUM>.

The diffraction peak in Example <NUM> is situated in proximity to a diffraction line of α-Cr (<NUM>). This is considered that when the functional layer <NUM> formed of Ti was provided, crystal growth of α-Cr was promoted to thereby form a Cr composite film with α-Cr as the main component.

Next, multiple samples used in Example <NUM> and comparative example <NUM> were fabricated, and gauge characteristics were measured. As a result, a gauge factor for each sample in Example <NUM> was between <NUM> and <NUM>. In contrast, a gauge factor for each sample in comparative example <NUM> was less than <NUM>.

Also, for each sample in Example <NUM>, the gauge factor temperature coefficient TCS and temperature coefficient of resistance TCR were each in the range of from -<NUM> ppm/°c to +<NUM> ppm/°C. In contrast, for each sample in comparative example <NUM>, the gauge factor temperature coefficient TCS and temperature coefficient of resistance TCR were not each in the range of from -<NUM> ppm/°c to +<NUM> ppm/°C.

As described above, with the functional layer <NUM> formed of Ti being provided, crystal growth of α-Cr was promoted and a Cr composite film was formed with α-Cr as the main component, so that a strain gauge that had a gauge factor of <NUM> or more, and that had the gauge factor temperature coefficient TCS and temperature coefficient of resistance TCR being each in the range of from -<NUM> ppm/°c to +<NUM> ppm/°c, was fabricated. Note that the diffusion effect of Ti into the Cr composite film is considered to cause the improvement in the gauge characteristics.

In Example <NUM>, multiple substrates <NUM> each formed of a polyimide resin that had a thickness of <NUM> and that had a different expansion coefficient were prepared. Then, when a Cr-composite film, as a given resistor <NUM>, was deposited, a relationship between an expansion coefficient of a given substrate <NUM> and internal stress of the resistor <NUM> was checked, to thereby obtain the result illustrated in <FIG>.

The internal stress of the resistor <NUM> was estimated by measuring warp in an evaluation sample and using the Stoney formula given by Formula (<NUM>). Note that as can be seen from Formula (<NUM>), the internal stress of the resistor <NUM> illustrated in <FIG> indicates a value per unit thickness and does not depend on the thickness of the resistor <NUM>. <NUM>]<MAT> Note that in Formula (<NUM>), E denotes Young's modulus, ν denotes Poisson's ratio, D denotes the thickness of the substrate <NUM>, t denotes the thickness of the resistor <NUM>, and R denotes change in radius of curvature in the substrate <NUM>.

From <FIG>, when the expansion coefficient of the substrate <NUM> is in the range of from <NUM> ppm/K to <NUM> ppm/K, the internal stress of the resistor <NUM> can be maintained to be in the range of ±<NUM> GPa. Where, ±<NUM> GPa indicates values expressing a permittable warp in the strain gauge <NUM> for functioning, and was experimentally determined by the inventors.

In other words, when the expansion coefficient of the substrate <NUM> is out of the range of from <NUM> ppm/K to <NUM> ppm/K, the internal stress of the resistor <NUM> is out of the range of ±<NUM> GPa and thus warp in the strain gauge <NUM> would increase, so that the strain gauge <NUM> would not function as a strain gauge. Therefore, the expansion coefficient of the substrate <NUM> is required to be in the range of from <NUM> ppm/K to <NUM> ppm/K. Note that the material of the substrate <NUM> does not necessarily include a polyimide resin.

The expansion coefficient of the substrate <NUM> can be in the range of from <NUM> ppm/K to <NUM> ppm/K, by selecting the material of the substrate <NUM>, selecting the material of the filler contained in the substrate <NUM>, adjusting the content, and the like.

As described above, with the expansion coefficient of the substrate <NUM> being in the range of from <NUM> ppm/K to <NUM> ppm/K, a difference in the expansion coefficient between the substrate <NUM> and the resistor <NUM>, as well as other factors, are absorbed, so that the internal stress of the resistor <NUM> can be in the range of ±<NUM> GPa. As a result, warp in the strain gauge <NUM> is reduced to thereby cause the strain gauge <NUM> to be able to function stably in a manner such that great gauge characteristics are maintained.

In Example <NUM>, multiple substrates <NUM> each formed of a polyimide resin that had a thickness of <NUM> and that contained fillers were prepared. Three sets of samples, each of which included a sample not being subject to heat treatment, a sample being subject to heat treatment at a temperature of <NUM>, a sample being subject to heat treatment at a temperature of <NUM>, and a sample being subject to heat treatment at a temperature of <NUM>, were fabricated. Then, the samples were returned to be at normal temperature, and surface unevenness on the upper surface 10a of each substrate <NUM> was measured by three-dimensional optical interference.

Next, the resistor <NUM> having a film thickness of <NUM> was deposited on the upper surface 10a of each substrate <NUM>, by magnetron sputtering, and patterning was performed by photolithography, as illustrated in <FIG>. Then, the number of pinholes that were generated in the resistor <NUM> was measured by a light transmission method in which light was transmitted from a back surface of a given sample.

Next, based on a measured result, a relationship between surface unevenness on the upper surface 10a of a given substrate <NUM> and the number of pinholes that were generated in a given resistor <NUM> was summarized in <FIG>. Note that each bar graph illustrated in <FIG> shows surface unevenness, and a line graph shows the number of pinholes. Additionally, for the horizontal axis, <NUM>, <NUM>, and <NUM> each indicate a temperature when a given substrate <NUM> was subject to heat treatment, and Incomplete indicates that heat treatment is not carried out.

<FIG> indicates that when a given substrate <NUM> is heated at temperatures between <NUM> and <NUM>, the surface unevenness on the upper surface 10a of the substrate <NUM> is <NUM> or less, which is about half of surface unevenness in a case of being incomplete, and that as a result, the number of pinholes in the resistor <NUM> is drastically reduced to about <NUM>/<NUM>. Note, however, that in consideration of resistance to thermal temperature of a polyimide resin, when heat treatment is carried out at temperatures exceeding <NUM>, alteration or deterioration may occur. Accordingly, it is preferable that the heat treatment be carried out at temperatures between <NUM> and <NUM>. Note that it is considered that the surface unevenness is reduced by heat treatment because fillers are contained in a polyimide resin that constitutes the substrate <NUM>, during thermal shrinkage caused by the heat treatment.

According to consideration by the inventors, the number of pinholes (about <NUM>) in the case of Incomplete, as illustrated in <FIG>, indicates a level of the gauge characteristics deteriorating. In contrast, the number of pinholes (about <NUM>) after heat treatment, indicates a level of the gauge characteristics not being adversely affected. In other words, when the resistor <NUM> having a film thickness of <NUM> is used, in a case where the surface unevenness on the upper surface 10a of the substrate <NUM> is <NUM> or less, it was confirmed that the number of pinholes that were generated in the resistor <NUM> could be reduced to indicate a level of the gauge characteristics not being adversely affected.

Note that when the resistor <NUM> having a film thickness of greater than <NUM> is used, it is obvious that when the surface unevenness on the upper surface 10a of the substrate <NUM> is <NUM> or less, the number of pinholes that are generated in the resistor <NUM> can be reduced to indicate a level of the gauge characteristics not being adversely affected. In other words, with the surface unevenness on the upper surface 10a of the substrate <NUM> being <NUM> or less, when the resistor <NUM> having a film thickness of <NUM> or more is used, the number of pinholes that are generated in the resistor <NUM> can be reduced to indicate a level of the gauge characteristics not being adversely affected.

As described above, with the substrate <NUM> being subject to heat treatment, the surface unevenness on the upper surface 10a of the substrate <NUM> can be <NUM> or less, and as a result, the number of pinholes that are generated in the resistor <NUM> having a film thickness of <NUM> or more can be significantly reduced. As a result, the strain gauge <NUM> can function stably in a manner such that great gauge characteristics are maintained.

Note that in order to reduce the number of pinholes that are generated in the resistor <NUM>, it is important to reduce the surface unevenness on the upper surface 10a of the substrate <NUM>, and a method of reducing surface unevenness is not important. In the above description, the method of reducing surface unevenness by heat treatment has been described, but is not limited to this case. Any method may be used as long as the surface unevenness on the upper surface 10a of the substrate <NUM> can be reduced.

The surface unevenness on the upper surface 10a of the substrate <NUM> can be reduced by, for example, a method of scraping a protrusion by approximately vertically irradiating the upper surface 10a of the substrate <NUM>, with laser light; a method of cutting a protrusion by moving a water cutter or the like to be parallel to the upper surface 10a of the substrate <NUM>; a method of polishing the upper surface 10a of the substrate <NUM> with a grinding wheel; a method of pressing the substrate <NUM> while heating (heat press); or the like.

Further, in order to reduce the number of pinholes that are generated in the resistor <NUM>, it is important to reduce the surface unevenness on the upper surface 10a of the substrate <NUM>, and is not necessarily limited to being directed to surface unevenness caused by the fillers that are present. It is effective to reduce surface unevenness not being caused by the fillers that are present, by various methods described above. For example, when surface unevenness on the substrate <NUM> without containing fillers is greater than <NUM>, in a case where the surface unevenness on the upper surface 10a of the substrate <NUM> is <NUM> or less, by various methods described above, the number of pinholes that are generated in the resistor <NUM> having a film thickness of <NUM> or more can be reduced to a level of the gauge characteristics not being adversely affected.

In Example <NUM>, the process illustrated in <FIG> was modified as described in the first modification of the second embodiment, the strain gauge 2A with the electrodes 40B was fabricated, and the presence or absence of dissolution of metallization was checked. Specifically, <NUM> types of samples in each of which Cu was used for the metallic layers <NUM> and <NUM>, in each of which NiP was used for the metallic layer <NUM>, in each of which Au was used for the metallic layer <NUM>, and in each of which the thickness of a given metallic layer was changed were fabricated (samples No. <NUM> to No. <NUM>), and then the presence or absence of dissolution of metallization was checked.

Table <NUM> shows results. Note that in Table <NUM>, the film thickness "<NUM>" indicates that no metallic layer was formed. The "poor" indicates that dissolution of metallization occurred in soldering being first performed. The "good" indicates that although no dissolution of metallization occurred in soldering being first performed, little dissolution of metallization occurred in soldering being performed second (where soldering refinement, etc. was assumed). Additionally, the "excellent" indicates that dissolution of metallization occurred neither in soldering being performed first nor second.

As shown in Table <NUM>, it was confirmed that when the thickness of Cu was <NUM> or more, dissolution of metallization was improved, and that when the thickness was <NUM> or more, the dissolution of metallization was further improved. Additionally, from the results for sample <NUM> and sample <NUM>, it was confirmed that the presence or absence of dissolution of metallization was determined only according to the thickness of Cu and was not determined upon the presence or absence of each of NiP and Au. Note, however, that as described above, in order to prevent dissolution of metallization and improve solder wettability, a metallic layer formed of Au or an equivalent material (Pt or the like) is required.

A fourth embodiment provides an example of a sensor having a different structure from the structure in the first embodiment. Note that in the fourth embodiment, the description for the same components as the embodiments that have been described may be omitted.

<FIG> is a plan view of an example of the sensor according to the fourth embodiment. <FIG> is a cross-sectional view of an example of the sensor according to the fourth embodiment, and illustrates the cross section taken along the C-C line in <FIG>.

Referring to <FIG>, a sensor 6A is an aggregation of individual sensors <NUM> (strain gauges). In the present embodiment, for example, the sensor 6A includes six individual sensors <NUM>. However, the number of individual sensors <NUM> is not limited to six.

The sensor 6A includes the substrate <NUM> common to the individual sensors <NUM>, and includes a resistor <NUM> and terminal sections <NUM> that are provided in each individual sensor <NUM>. The individual sensors <NUM> are disposed on one side of the same substrate <NUM>. Each individual sensor <NUM> has the same characteristics as the strain gauge <NUM>.

The cover layer <NUM>, as described in the first embodiment, may be provided on and above the upper surface 10a of the substrate <NUM>, such that resistors <NUM> of the individual sensors <NUM> are coated and the terminal sections <NUM> are exposed. With the cover layer <NUM> being provided, mechanical damage, and the like can be prevented from occurring in the resistors <NUM> of the individual sensors <NUM>. Additionally, with the cover layer <NUM> being provided, the resistors <NUM> of the individual sensors <NUM> can be protected against moisture, and the like. Note that the cover layer <NUM> may be provided to cover all portions except for the terminal sections <NUM>.

The sensor 6A may be attached to a surface of an object to be measured, or may be embedded in the object to be measured.

As described above, with use of the sensor 6A that is the aggregation of individual sensors <NUM> (strain gauges), a state of a measured object may be detected. In such a manner, it may be more convenient in comparison to a manner of employing multiple strain gauges <NUM>. Note that the state of the measured object includes strain, expansion, contraction, deformation, or the like of the measured object.

A fifth embodiment provides an example of a sensor capable of obtaining three dimensional information. Note that in the fifth embodiment, the description for the same components as those in the embodiments described previously may be omitted.

<FIG> is a plan view of an example of a sensor according to the fifth embodiment. <FIG> is a cross-sectional view of an example of the sensor according to the fifth embodiment, and illustrates the cross section taken along the D-D line in <FIG>.

Referring to <FIG> and <FIG>, a sensor 6B includes resistors 30B, and terminal sections 41B and 42B.

Each resistor 30B includes resistive portions 31B and 32B that are laminated via the substrate <NUM>. In such a case, the resistor 30B is a collective term for the multiple resistive portions 31B and 32B. In particular, when the resistive portions 31B and 32B are distinguished from each other, they are referred to as the resistor 30B. Note that in <FIG>, for the sake of convenience, the resistive portions 31B and 32B are each illustrated in a crepe pattern.

The multiple resistive portions 31B are thin films of which the longitudinal direction of each is directed to the X direction and that are juxtaposed in the Y direction at predetermined intervals, on the upper surface 10a of the substrate <NUM>. The multiple resistive portions 32B are thin films of which the longitudinal direction of each is directed to the Y direction and that are juxtaposed in the X direction at predetermined intervals, on the lower surface 10b of the substrate <NUM>. Note, however, that the multiple resistive portions 31B and the multiple resistive portions 32B may intersect while not being required to be perpendicular to each other in a plan view.

The width of the resistor 30B is not particularly restricted, and can be appropriately selected for any purpose. For example, the width can be approximately between <NUM> and <NUM> (<NUM>). A pitch between resistors <NUM> next to each other is not particularly restricted, and can be appropriately selected for any purpose. For example, the pitch can be approximately between <NUM> and <NUM>. Note that in <FIG> and <FIG>, ten resistive portions 31B and ten resistive portions 32B are illustrated. However, the number for each of the resistive portion 31B and the resistive portion 32B can be appropriately varied as necessary. For each resistor 30B, the material, the thickness, the manufacturing method, and the like can be adopted as in the resistor <NUM>.

On the upper surface 10a of the substrate <NUM>, given terminal sections 41B respectively extend from both end portions of each resistive portion 31B, and are each wider than the resistive portion 31B to be formed in an approximately rectangular shape, in a plan view. The terminal sections 41B are a pair of electrodes from which a change in a given resistance value of the resistive portion 31B in accordance with the press force is output externally, where, for example, a flexible substrate or lead wire for external connection, or the like is joined. The upper surface of each terminal section 41B may be coated with a metal allowing for greater solderability than the terminal section 41B. Note that for the sake of convenience, the resistive portions 31B and the terminal sections 41B are expressed by different numerals. However, a given resistive portion 31B and given terminal sections 41B can be integrally formed of the same material, in the same process.

On the lower surface 10b of the substrate <NUM>, given terminal sections 42B respectively extend from both end portions of each resistive portion 32B, and are each wider than the resistive portion 32B to be formed in an approximately rectangular shape, in a plan view. The terminal sections 42B are a pair of electrodes from which a change in a given resistance value of the resistive portion 32B in accordance with the press force is output externally, where, for example, a flexible substrate or lead wire for external connection, or the like is joined. The upper surface of each terminal section 42B may be coated with a metal allowing for greater solderability than the terminal section 42B. Note that for the sake of convenience, the resistive portions 32B and the terminal sections 42B are expressed by different numerals. However, a given resistive portion 32B and given terminal sections 42B can be integrally formed of the same material, in the same process.

Note that through interconnects (through holes) are provided through the substrate <NUM>, and the terminal sections 41B and 42B may be collected on the upper surface 10a side or the lower surface 10b side of the substrate <NUM>.

The cover layer <NUM>, as described in the first embodiment, may be provided on and above the upper surface 10a of the substrate <NUM>, such that the resistive portions 31B are coated and the terminal sections 41B are exposed. The cover layer <NUM>, as described in the first embodiment, may be also provided on and above the lower surface 10b of the substrate <NUM>, such that the resistive portions 32B are coated and the terminal sections 42B are exposed. By providing the cover layers, mechanical damage and the like can be prevented from occurring in the resistive portions 31B and 32B. Further, by providing the cover layers, the resistive portions 31B and 32B can be protected against moisture and the like. Note that one or more cover layers <NUM> may be provided to cover all portions except for the terminal sections 41B and 42B.

As illustrated in <FIG>, a sensor module <NUM> can be implemented by the sensor 6B and a controller <NUM>. In the sensor module <NUM>, the sensor 6B is attached to an object to be measured, and a state of the measured object can be detected by the controller <NUM>. Multiple sensors 6B may be attached to the object to be measured.

In the sensor module <NUM>, the terminal sections 41B and 42B of the sensor 6B are each connected to the controller <NUM>, by using, for example, a flexible substrate, a lead wire, or the like.

Based on information obtained through given terminal sections 41B and 42B, coordinates of a given location at which the sensor 6B is pressed, or a multitude of a pressing force can be detected. For example, each resistive portion 31B of the sensor 6B can be used to perform detection with respect to an X-coordinate, and each resistive portion 32B can be used to perform detection with respect to a Y-coordinate.

As illustrated in <FIG>, for example, the controller <NUM> can include an analog front end unit <NUM> and a signal processing unit <NUM>.

The analog front end unit <NUM> includes, for example, an input signal selection switch, a bridge circuit, an amplifier, an analog-to-digital conversion circuit (A/D conversion circuit), and the like. The analog front end unit <NUM> may include a temperature compensation circuit.

In the analog front end unit <NUM>, for example, all of the terminal sections <NUM> and <NUM> of the sensor 6B are connected to the input signal selection switch, and a pair of electrodes is selected by the input signal selection switch. A given pair of electrodes selected by the input signal selection switch is connected to the bridge circuit.

In such a case, one side of the bridge circuit is comprised of a given resistive portion between a given pair of electrodes selected by the input signal selection switch, and the other three sides are each comprised of fixed resistance. With such a configuration, as the output of the bridge circuit, a voltage (analog signal) corresponding to a resistance value of the resistive portion between a given pair of electrodes selected by the input signal selection switch can be obtained. Note that the input signal selection switch is configured to be able to be controlled by the signal processing unit <NUM>.

An output voltage of the bridge circuit is amplified by the amplifier and then is converted to a digital signal by the A/D conversion circuit. The digital signal is transmitted to the signal processing unit <NUM>. When the analog front end unit <NUM> includes a temperature compensation circuit, a digital signal for which temperature compensation is performed is transmitted to the signal processing unit <NUM>. By performing switching through the input signal selection switch at high speed, digital signals corresponding to resistance values associated with all of the terminal sections 41B and 42B of the sensor 6B can be transmitted to the signal processing unit <NUM> in an extremely short amount of time.

Based on information transmitted from the analog front end unit <NUM>, the signal processing unit <NUM> can identify one or more coordinates of locations at which the sensor 6B is pressed, as well as detecting the magnitude of a given press force.

When resistance values for multiple resistive portions 31B or resistance values for multiple resistive portions 32B are varied, it can be detected that the sensor 6B is pressed at corresponding multiple locations.

Note that when the magnitude of the pressing force is decreased, or the like, there are cases where only one or more resistive portions that are closer to the pressed side and that are among the resistive portions 31B and the resistive portions 32B are pressed while any resistive portion that is far from the pressed side is not pressed. In this case, only a resistance value between a pair of electrodes associated with each of the resistive portions that is closer to the pressed side, continuously varies in accordance with the magnitude of the pressing force. In such a case, the signal processing unit <NUM> can detect the magnitude of the press force based on the magnitude of variations in a given resistance value of the resistive portion that is closer to the pressed side.

In other words, at least one resistive portion among a given resistive portion 31B and a given resistive portion 32B is pressed, and a resistance value between a pair of electrodes associated with the at least one resistive portion (resistive portion 31B and/or resistive portion 32B) constantly varies in accordance with the magnitude of the pressing force. Regardless of whether either one of the resistive portion 31B and the resistive portion 32B is pressed or both are pressed, the signal processing unit <NUM> can detect the magnitude of the pressing force based on the magnitude of variations in a given resistance value of the resistive portion that is closer to the pressed side.

The signal processing unit <NUM> can include, for example, a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), a main memory, and the like.

In this case, various functions of the signal processing unit <NUM> can be implemented by executing a program stored in the ROM or the like, where the program is read out to a main memory and is executed by the CPU. However, a portion or all of the signal processing unit <NUM> may be implemented by hardware only. The signal processing unit <NUM> may be also configured physically by a plurality of devices or the like.

As described above, in the fifth embodiment, the sensor 6B with juxtaposed multiple resistive portions 31B of which the longitudinal direction of each is directed to a first direction and juxtaposed multiple resistive portions 32B of which the longitudinal direction of each is directed to a second direction intersecting with the first direction is used.

As described above, when the resistive portions 31B and 32B are pressed, the pressed resistive portions 31B and 32B are deflected in accordance with a pressing force, and thus a resistance value between a given pair of electrodes associated with the pressed resistive portions 31B and 32B varies continuously in accordance with the magnitude of the pressing force. That is, with use of the sensor 6B, 3D information (coordinates of the pressed location and the magnitude of the pressing force) can be obtained. In such a manner, information about the entire object to be measured is obtained, and thus a position of the measured object where the state of the object is varied can be identified in detail. Accordingly, the state of the measured object can be detected accurately.

In particular, when the resistive portions 31B and 32B are each formed of a Cr composite film, sensitivity of a resistance value with respect to a force (a change amount of the resistance value for each of the resistive portions 31B and 32B with respect to the same pressing force) is significantly improved in comparison to a case where the resistive portions 31B and 32B are each formed of Cu-Ni or Ni-Cr. When the resistive portions 31B and 32B are each formed of the Cr composite film, sensitivity of the resistance value with respect to the force is about <NUM> to <NUM> times greater than that in a case where the resistive portions 31B and 32B are each formed of Cu-Ni or Ni-Cr. For this reason, by forming each of the resistive portions 31B and 32B of a Cr composite film, detection accuracy of coordinates of the pressed location can be improved, and the pressing force can be detected with high sensitivity.

When sensibility of the resistance value with respect to a given pressing force is increased, a control can be implemented such that, a predetermined operation is performed when it is detected that the pressing force is at weak level, another operation is performed when it is detected that the pressing force is at middle level, and still another operation is performed when it is detected that the pressing force is at strong level. Alternatively, a control can be implemented such that, no operation is performed when it is detected that the pressing force is at weak or middle level, and a predetermined operation is performed only when it is detected that the pressing force is at strong level.

When sensibility of the resistance value with respect to a given pressing force is increased, a signal with increased S/N can be obtained. Thus, signal detection can be performed accurately even when the number of times the A/D conversion circuit of the analog front end unit <NUM> performs averaging is reduced. By reducing the number of times the A/D conversion circuit performs averaging, a time required for one A/D conversion can be decreased, so that the input signal selection switch can perform switching at a higher speed. As a result, a fast movement transferred to the tactile sensor <NUM> can also be detected.

When each resistor 30B is formed of a Cr composite film, the size of the sensor 6B can be reduced. Thus, flexibility in a choice of installation locations can be improved.

The first modification of the fifth embodiment provides an example in which the resistive portions of the sensor body are each disposed in a zigzag pattern. Note that in the first modification of the fifth embodiment, the description for the same components as those in the embodiments described previously may be omitted.

<FIG> is a plan view illustrating an example of the sensor according to the first modification of the fifth embodiment, and illustrates the plane corresponding to <FIG>. Referring to <FIG>, a sensor 6C differs from the sensor 6B (see <FIG> and <FIG>) in that a resistor 30C is used instead of the resistor 30B.

The resistor 30C includes resistive portions 31C and 32C. Each resistive portion 31C is disposed in a zigzag pattern formed between a pair of given terminal sections 41B. Each resistive portion 31C is also disposed in a zigzag pattern formed between a pair of given terminal sections 42B. For example, the material and thickness for each of the resistive portions 31C and 32C can be the same as the material and thickness for each of the resistive portions 31B and 32B.

In such a configuration, when the resistive portions 31C and 32C are each disposed in a zigzag pattern, a resistance value between a given pair of terminal sections 41B and a resistance value between a given pair of terminal sections 42B can be increased in comparison to a case where their resistive portions are each disposed in a linear pattern. As a result, when pressed, a change amount of the resistance value between a given pair of terminal sections 41B, and a change amount of the resistance value between a given pair of terminal sections 42B, are increased. Thus, detection accuracy of coordinates of the pressed location can be improved, and a given force can be detected with higher sensitivity.

A resistance value between the pair of the terminal sections 41B, as well as a resistance value between the pair of the terminal sections 42B, can be increased, thereby allowing reductions in power consumption for the sensor 6C.

In a sixth embodiment, an application example in which a Cr composite film is used as a material of the resistor <NUM> in the strain gauge according to the first embodiment is shown. Note that in the sixth embodiment, the description of the same components as those in the embodiments described previously may be omitted.

For the strain gauge <NUM> according to the first embodiment, when a Cr composite film is used as the material of the resistor <NUM>, higher sensitivity (<NUM>% or more the sensitivity of conventional strain gauges) and a smaller size (<NUM>/<NUM> or less the size of conventional strain gauges) can be set. In the following description, the strain gauge <NUM> using a Cr composite film is referred to as a strain gauge <NUM>, for the sake of convenience.

For example, the output of the conventional strain gauge is about <NUM> mV/<NUM> V, while the output of the strain gauge <NUM> can be <NUM> mV/<NUM> V or more. Also, the size (gauge length × gauge width) of the conventional strain gauge is about <NUM> × <NUM>, while the size (gauge length × gauge width) of the strain gauge <NUM> can be reduced to be about <NUM> × <NUM>.

In general, strain gauges are used when attached to flexure elements (metal or the like). Conventional strain gauges have low sensitivity, and thus design choices of material of a given flexure element are constrained in order to ensure sensor characteristics.

In contrast, the strain gauge <NUM> has higher sensitivity than that of the conventional strain gauges, design constraints, such as when the conventional strain gauges are used, are mitigated greatly, and thus flexibility in the material choice of a given flexure element can be improved.

Further, a smaller size of the strain gauge <NUM> is set in comparison to the conventional strain gauges, and thus installation at a location that could not hitherto be used for fine measurement becomes possible.

The strain gauge <NUM> is a film-type flexible gauge. In this regard, small-sized strain gauges <NUM>, as well as strain gauges in various sizes, can be manufactured and supplied.

The strain gauge <NUM> is lightweight and can be attached at a desired measurement location. Thus, advantageously, desired locations can be directly measured in comparison to a case of using a micro electro mechanical systems (MEMS) sensor or the like that requires an electronic board to be mounted when similar measurement is performed.

The strain gauge <NUM> is very small and mass of the strain gauge <NUM> is negligible, and thus the strain gauge <NUM> is not influenced by inertia. Accordingly, the strain gauge <NUM> is excellent in sensitivity, stability, and fatigue life.

The strain gauge <NUM> can also be self-temperature compensated. In this case, any measured object with a different coefficient of thermal expansion can be used regardless of whether the object is metal or plastic.

The strain gauge <NUM> is highly sensitive and can detect small displacement. Thus, the strain gauge <NUM> can also be used for a measured object having great stiffness.

With the characteristics described above, the strain gauge <NUM> can be applied in various manners. Specific examples of the application of the strain gauge <NUM> will be described below.

Air resistance on an automobile is invisible and unstable, and the air resistance is difficult to be measured. In such a manner, it is difficult to understand a downforce created on an automobile body, an air diagram of a lift force, and the like. In light of the point described above, in the example of the first application, the strain gauge <NUM> is used to detect wind pressure or the like applied to a driving automobile.

<FIG> is a schematic diagram illustrating an example of an air flow when the automobile is traveling. When an automobile <NUM> is traveling, an air flow occurs as illustrated by the arrows in <FIG>, for example. When such an air flow causes a higher driving speed of the automobile <NUM>, a lift force acts on an automobile body and thus the automobile body attempts to float, which may result in unstable driving.

In light of the situation described above, the automobile <NUM> includes a front spoiler <NUM>, side spoilers <NUM>, and a rear spoiler (rear wing) <NUM>. With the automobile <NUM> including the front spoiler <NUM>, the side spoilers <NUM>, and the rear spoiler <NUM>, downforces act in the directions represented by the arrows, and even if the speed is increased, the lift force acting against the automobile body is reduced. Thus, floating of the automobile body is reduced, thereby allowing for stable driving.

<FIG> is a perspective view of an example not part of the invention as claimed of a given automotive spoiler to which the strain gauge <NUM> is attached. An automobile 500A illustrated in <FIG> includes a front spoiler 510A, side spoilers 520A, and a rear spoiler (rear wing) 530A. The strain gauge <NUM> is attached to at least one among the front spoiler 510A, the side spoilers 520A, and the rear spoiler (rear wing) 530A.

For example, the strain gauge <NUM> may be attached to a surface of at least one spoiler among the front spoiler 510A, the side spoilers 520A, and the rear spoiler (rear wing) 530A, or may be embedded in the at least one spoiler. Alternatively, an air intake is disposed at at least one spoiler among the front spoiler 510A, the side spoilers 520A, and the rear spoiler (rear wing) 530A, and the strain gauge <NUM> may be attached at a location where a flow of drawn air is concentrated, or may be embedded at the location.

As described above, by attaching the strain gauge <NUM> to a given spoiler, wind pressure of a given surface of the spoiler can be sensed to detect a lift force and downforce applied to the automobile body.

Further, by displaying a detected value on a center information display (CID), an E-cockpit display, a head-up display, or the like, downforces against the automobile body can be visualized, and air diagrams can be quantified.

While the spoilers are lightweight and are formed of resin in many cases, a lightweight, flexible strain gauge <NUM> that is formed on a flexible substrate is easily attached, and further, such a strain gauge <NUM> can detect air pressure with high sensitivity.

When a given spoiler is configured to be movable by a motor or the like, the spoiler can be moved based on wind pressure detected by the strain gauge <NUM> to thereby optimize the lift force or downforce to act against the automobile body. Accordingly, driving can be achieved more stably.

As described above, the strain gauge <NUM> is highly sensitive and thus can easily detect the wind pressure applied to a given spoiler. Also, by displaying a detected result on a given display, an air flow such as a downforce can be visualized. Additionally, by providing feedback for a detected result by the strain gauge <NUM> to a variable spoiler, a lift force and downforce acting against the automobile body are actively adjusted, thereby allowing for more stable driving. Further, by changing from a detected result to a corresponding effect level of fuel consumption that is caused by air resistance, information on fuel consumption can be visualized. Note that the strain gauge <NUM> may be used in an electric automobile, a hybrid automobile, or the like, as well as an engine-driven automobile.

Note that one or more strain gauges <NUM> may be used. Alternatively, instead of a given strain gauge <NUM>, the strain gauge 1A, <NUM>, 2A, or 2B, or the sensor 6A, 6B, or 6C, in which a Cr composite film is used as material of a given resistor, may be used.

Automobile accelerators are formed of materials (material that is hard to bend) having great stiffness. Sensors using conventional strain gauges could not accurately perform sensing as auxiliary sensors for a pressing force. In other words, the conventional strain gauges are of low sensitivity and thus only members formed of materials that are easily bent could be objects to be measured. Alternatively, in a case where a member formed of material that is easily bent could be the object to be measured, a given strain gauge is attached to such a measured object, via a flexure element formed of a material (material that is easy to bend) having less stiffness. In view of the point described above, in the example of the second application, an example in which the strain gauge <NUM> is used to detect a force to press an accelerator is illustrated.

Note that examples of the material having great stiffness (material that is hard to bend) include an aluminum alloy (duralumin), titanium, and the like. Examples of the material having less stiffness (material that is easy to bend) include aluminum, and the like.

<FIG> is a perspective view of an example of the automobile accelerator to which the strain gauge <NUM> is attached. In <FIG>, the strain gauge <NUM> is attached to a side surface of an automobile accelerator <NUM>. However, the strain gauge <NUM> may be attached to the back or the like of the accelerator <NUM>. Alternatively, the strain gauge <NUM> may be embedded in the accelerator <NUM>.

By attaching the strain gauge <NUM> to the accelerator <NUM>, the force to press the accelerator <NUM> can be detected. With use of the strain gauge <NUM> having great stiffness, even if the accelerator <NUM> is formed of a material (material that is hard to bend) having great stiffness, sensing can be performed with high sensitivity, and thus the pressing force can be detected more accurately.

As described above, the strain gauge <NUM> is highly sensitive, and even if the accelerator <NUM> is formed of a material (material that is hard to bend) having great stiffness, the pressing force can be detected with high accuracy. Thus, improvement in a speed control and fuel consumption of automobiles can be expected.

For example, a gripping force applied to an automobile steering wheel can be detected by dedicated sensors that are disposed at the steering wheel. For example, the dedicated sensors are respectively disposed at symmetrical two locations where gripping is likely to be performed, and grip forces to be applied at the disposed locations can be detected. Each dedicated sensor can be disposed, for example, between a core and an outer sheath of the steering wheel. However, in such arrangement, a problem in steering wheel design may arise negatively affecting some luxury automobiles. In view of the point described above, in the example of the third application, an example in which the strain gauge <NUM> is used to detect a force to grip the steering wheel is illustrated.

<FIG> are perspective views of a comparative example of the automobile steering wheel to which the dedicated sensors are attached. <FIG> is a perspective view of the steering wheel, as well as illustrating an enlarged internal structure of the steering wheel. <FIG> is a cross-sectional view taken along the E-E line in <FIG>.

In the comparative example illustrated in <FIG>, a steering wheel 550X has a structure in which each dedicated sensor 3X to detect a gripping force is disposed to be attached to the outer periphery of a resin portion <NUM> such as urethane, where the outer periphery of a core <NUM> formed of a material (for example, metal) with great stiffness is coated with the resin portion <NUM>, and the outer periphery of the dedicated sensor 3X is coated with an outer sheath <NUM> formed of leather or the like. The respective dedicated sensors 3X are arranged at symmetrical two locations of the annular steering wheel 550X where gripping is likely to be performed.

Each dedicated sensor 3X is less sensitive than the strain gauge <NUM>, and if the dedicated sensor 3X is attached inside the core <NUM> formed of metal or the like that is hard to deform, it is difficult to perform sensing. For this reason, in the steering wheel 550X, each dedicated sensor 3X is attached to the outer periphery of the resin portion <NUM> that is easy to deform.

In contrast, the strain gauge <NUM> is highly sensitive, and even if the strain gauge <NUM> is attached inside the core <NUM>, as illustrated in the cross-sectional view of the steering wheel <NUM> in <FIG>, a gripping force can be sensed. In other words, the strain gauge <NUM> is highly sensitive and thus can detect even a slight gripping force. In such a manner, even if the strain gauge <NUM> is attached inside the core <NUM>, the gripping force can be sensed. Note that <FIG> illustrates the cross section corresponding to <FIG>.

Also, as illustrated in <FIG>, when the strain gauge <NUM> is disposed around the entirety of the circumference on the steering wheel <NUM>, a gripping force can be detected in all directions. In this case, a given gripping force can be detected not only during normal driving as illustrated in <FIG>, but also in a case of gripping the steering wheel <NUM> at various positions, such as when the steering wheel is turned as illustrated in <FIG> and <FIG>. However, the strain gauge <NUM> is not necessarily required to be disposed around the entirety of the circumference on the steering wheel <NUM>, and may be disposed in at least a portion of the steering wheel <NUM>.

As described above, the strain gauge <NUM> is highly sensitive, and even if the strain gauge <NUM> is attached inside the core <NUM> with great stiffness, a given gripping force can be detected. Also, when the strain gauge <NUM> is attached inside the core <NUM>, designs of the steering wheel <NUM> are not influenced. Accordingly, the appearance of the steering wheel <NUM> is improved.

Further, when the strain gauge <NUM> with high sensitivity is disposed around the entirety of the circumference on the steering wheel <NUM>, a given gripping force can be detected even if the steering wheel is operated in association with turning, such as a right turn, a left turn, or rounding of a curve.

Automotive door knobs (door handles) are used as keyholes into which keys to lock doors are inserted, or levers employed during opening or closing of doors. However, for some luxury automobiles, negative images of body designs might be instilled, and thus it is considered to remove the doorknobs. The doorknobs are not flat and consequently are likely to be damaged disadvantageously. In view of the point described above, in the example of the fourth application, an example of a door without using any doorknob is illustrated, where the strain gauge <NUM> is used to unlock a locked door.

<FIG> is a perspective view of an example of the automobile door to which the strain gauge <NUM> is attached. <FIG> is a cross-sectional view of an example of the automobile door to which the strain gauge <NUM> is attached. A door <NUM> illustrated in <FIG> and <FIG> includes an inner panel <NUM> and an outer panel <NUM>, without including any doorknob. The strain gauge <NUM> is attached at a predetermined location inside the outer panel <NUM>. Alternatively, the strain gauge <NUM> may be embedded in the outer panel <NUM>.

By disposing the strain gauge <NUM> at the predetermined location of the door <NUM> on the outer panel <NUM> side, the predetermined location can be detected to be pressed, thereby allowing for unlocking of a locked door. For example, when a structure that opens or closes the door through power of a motor or the like is used, and the predetermined location at which the strain gauge <NUM> is attached is detected to be pressed, the locked door can be unlocked through power of the motor or the like, thereby enabling the door to be open.

By disposing the strain gauge <NUM> at the predetermined position of the door <NUM> on the outer panel <NUM> side, sensing can be performed inside the outer panel <NUM>, and thus designs of the automobile body are not negatively affected. Also, the strain gauge <NUM> is highly sensitive, thereby allowing for reliable detection of unlocking of a given locked door.

For example, when strain gauges <NUM> on the outer panel <NUM> side are disposed at multiple positions, and then are pressed in a predetermined specific order, a configuration that unlocks a locked door, as well as opening or closing of the door, may be used. In such a configuration, erroneous detection can be avoided and only a specific person can unlock a given locked door, as well as opening or closing of the door. Accordingly, authentication for a door lock can be also implemented.

Alternatively, the sensor 6B (see <FIG> and <FIG>) on the outer panel <NUM> side is disposed at a predetermined location, and the sensor 6B may detect that a predetermined specific input pattern is traced with a figure or the like. In this case as well, erroneous detection can be avoided, and only a specific person can unlock a locked door, as well as opening or closing of the door. Accordingly, authentication for the door lock can be implemented.

As described above, with use of the strain gauge <NUM>, any door knob is not used when the door is opened or closed, and flexibility in the body design is improved. Thus, designing forms of bodies targeted for some luxury automobiles can be provided. Further, a new opening and closing system that marks less of scratching during opening of closing of a door can be proposed.

Electronic stability control (ESC) to detect an unstable state of an attitude of a vehicle, such as automobile oversteer or understeer, relates to an active safety system that controls "turning" in association with automobile basic performance. In the ESC, for example, tilt sensors are used. Specifically, "pendulum type" tilt sensors each of which detects deviation from a weight suspended in a gravity direction, relative to a tilted object, or "float type" tilt sensors each of which detects deviation from a liquid level, relative to the tilted object, are used. MEMS-type acceleration sensors, gyroscopes (angular velocity sensors), or the like are also used. However, problems in accuracy of the tilt sensors may arise, and further, the acceleration sensors, gyros (angular velocity sensors), or the like may require high costs, thereby causing problems in increased costs. In view of the point described above, in the example of the fifth application, an example in which strain gauges <NUM> are used to detect an attitude of the automobile is illustrated.

<FIG> is a perspective view of an example of a <NUM>-axis force sensor with the strain gauges <NUM>. A <NUM>-axis force sensor <NUM> illustrated in <FIG> includes a flexure element <NUM> with an outer frame <NUM> and four beams <NUM>, a weight <NUM>, and multiple strain gauges <NUM>.

The four beams <NUM> are each rectangular prisms and are arranged to form a cross on an inner wall side of the outer frame <NUM>. Two strain gauges <NUM> are arranged side by side, on a given surface among surfaces of each of the beams <NUM>, and the number of strain gauges <NUM> is <NUM> in total. However, shapes of the outer frame <NUM> and the beams <NUM> of the flexure element <NUM>, as well as the number of strain gauges <NUM>, are examples, and are not limited to the examples described above.

In the <NUM>-axial force sensor <NUM>, a sensitive section is formed at an intersection of the four beams <NUM> that are arranged to form the cross, and the weight <NUM> is secured at the sensitive section. In such a manner, for the <NUM>-axis force sensor <NUM>, a translational force and a couple in each of <NUM>-axis directions are detected with one sensor.

For example, the <NUM>-axis force sensor <NUM> can be disposed proximal to the center of gravity G of an automobile 500B illustrated in <FIG>. In such a manner, the weight <NUM> of the <NUM>-axis force sensor <NUM> is tilted in accordance with the attitude of the automobile 500B, and thereby a vertical movement, lateral movement, forward movement, yawing movement, pitching movement, and rolling movement of the automobile 500B can be detected. Accordingly, an attitude control of the automobile body can be performed.

As described above, when the <NUM>-axis force sensor <NUM> with the strain gauges <NUM> is used as a sensor for the attitude control of a given automobile body, the ESC can be simply implemented, and thus an inexpensive and safe ESC system can be implemented. Moreover, with use of one or more highly sensitive strain gauges <NUM>, slight deviation through the attitude caused by oversteer, understeer, or the like can be also detected. Thus, an inexpensive and safe ESC system can be implemented easily.

The attitude control in the example of the fifth application may be used in conjunction with the control for the variable spoiler in the example of the first application. For example, when a given variable spoiler is controlled in order to stabilize the attitude of the automobile body that is detected by the <NUM>-axis force sensor <NUM>, an accident in which a strong wind overturns the automobile 500B can be avoided.

In the example of the sixth application, an example in which strain gauges <NUM> and the like are used to detect an operating state of windshield wipers is illustrated.

<FIG> is a schematic diagram illustrating an example of automobile wipers to which the respective strain gauges <NUM> are attached. In <FIG>, the numerals <NUM> represent two wipers. Each wiper <NUM> includes a wiper arm <NUM>, a wiper blade <NUM>, and a wiper rubber portion <NUM>.

Each strain gauge <NUM> is attached to the surface of the wiper arm <NUM> of a given wiper <NUM>. Alternatively, each strain gauge <NUM> may be embedded in the wiper arm <NUM> of a given wiper <NUM>.

By attaching each strain gauge <NUM> to the wiper arm <NUM> of a given wiper <NUM>, a sliding state and an uneven wiping state of the wiper <NUM> can be detected.

An operating speed of the wiper arm <NUM> of each wiper <NUM> can be also varied based on a detected result by a given strain gauge <NUM>. Alternatively, for each wiper <NUM>, a structure that can vary an angle at which a portion being the wiper rubber portion <NUM> is set is used, and further, the angle at which the portion being the wiper rubber portion <NUM> is set is varied based on a detected result by a given strain gauge <NUM>. Thus, a sliding state and an uneven wiping state of the wiper <NUM> can be also improved. Further, abrasion of a portion of the wiper rubber portion <NUM> of each wiper <NUM> can be detected based on a detected result by a given strain gauge <NUM>.

As illustrated in <FIG>, the sensor 6B may be also attached to a substantially entire bottom (surface opposite the surface to contact a glass surface) of the wiper rubber portion <NUM> of each wiper <NUM>.

When uneven wiping by the wiper rubber portion <NUM> of each wiper <NUM> is detected using a given sensor 6B, feedback for a mounting angle of each of the wiper arm <NUM> and the wiper blade <NUM> is provided. Thus, a glass surface and the wiper rubber portion <NUM> can be uniformly in contact with each other so as to avoid separation or the like from the wiper rubber portion <NUM>.

Specifically, pressure applied to each wiper blade <NUM> is detected by a given sensor 6B that is attached to a back of the wiper rubber portion <NUM>, and thereby feedback is provided to operate a given wiper arm <NUM> in order to optimize a mounting angle of the wiper arm <NUM> in accordance with pressure distribution. Accordingly, uneven wiping through each wiper <NUM> can be reduced.

The automotive wipers remove rain water or debris that adheres to a windshield. However, when operating, the wipers do not move smoothly and consequently friction against a glass occurs, which might result in occurrence of "chattering. " Under a condition in which the "chattering" occurs, the wipers cannot serve as intended roles, and consequently rain water caused by uneven wiping remains on the windshield, as well as forming stripes on the windshield. In worse cases, visibility becomes bad, which might cause a driving problem. Especially in a case of driving at night, sight is instantaneously obstructed due to a great difference in light and dark between a proximal location to a street light and a distant location from the street light, which might cause a great risk.

When the strain gauge <NUM>, the sensor 6B, or the like is attached to a given wiper <NUM>, even if a given wiper rubber portion <NUM> deteriorates due to temperature, ultraviolet light, or the like, or a given wiper arm <NUM> is bent, a given glass surface and the given wiper rubber portion <NUM> constantly come into uniform contact with each other. Thus, the wiper rubber portion <NUM> moves to the left and right without occurrence of "chattering," thereby enabling rain water, dirt, and the like adhering to the glass to be uniformly removed.

In the example of the seventh application, an example in which the strain gauge <NUM> is used to activate an airbag is illustrated.

<FIG> is a schematic diagram illustrating an example of an automobile bumper to which the strain gauge <NUM> is attached, and illustrates an example of a manner of a crashed automobile into a wall. In <FIG>, the strain gauge <NUM> is attached to a bumper <NUM> of an automobile 500C. Alternatively, the strain gauge <NUM> may be embedded in the bumper <NUM>. In <FIG>, the left side of the bumper <NUM> of the automobile 500C hits a wall <NUM>.

By attaching the strain gauge <NUM> to the bumper <NUM>, an impact of the automobile 500C is detected, thereby enabling the airbag to be activated. Alternatively, when the strain gauge <NUM> is attached to a given airbag, the strain gauge <NUM> can also detect whether pressure applied when the airbag is actuated is appropriate.

<FIG> is a schematic diagram illustrating an example of an airbag control system. As illustrated in <FIG>, an airbag system <NUM> is mounted on an automobile 500C. The airbag system <NUM> includes a strain gauge <NUM>, an electronic control unit (ECU) <NUM>, and an airbag controller <NUM>.

The airbag controller <NUM> includes an inflator <NUM> filled with an igniting agent and gas-forming agent, and an airbag <NUM> to be filled with gas that is formed from the gas-forming agent. The strain gauge <NUM> is disposed at the bumper <NUM>, and the airbag <NUM> is disposed in front of a driver's seat of the automobile, on the side of the driver's seat, or the like.

The ECU <NUM> is electrically connected to the strain gauge <NUM>. The ECU <NUM> includes an interface circuit for an on-board LAN such as a controller area network (CAN), and receives various information about the automobile, including the output of the strain gauge <NUM>.

The ECU <NUM> is a control unit that operates the airbag controller <NUM> based on a detected result by the strain gauge <NUM>. The ECU <NUM> is connected to the airbag controller <NUM>, and transmits an instruction to expand the airbag to the inflator <NUM>, based on the output of the strain gauge <NUM>. In such a manner, the igniting agent in the inflator <NUM> is ignited to thereby expand the airbag <NUM>.

For example, as illustrated in <FIG>, when the left side of the bumper <NUM> of the automobile 500C hits the wall <NUM>, the strain gauge <NUM> detects the impact of the body of the automobile 500C as changes in a resistance value of a given resistor, and then output the detected impact to the ECU <NUM>. The ECU <NUM> controls the airbag controller <NUM> based on the output of the strain gauge <NUM>, and the airbag <NUM> is thereby expanded.

Note that in the above example, although the strain gauge <NUM> is provided on the bumper <NUM> of the automobile 500C, the impact of the automobile body does not necessarily occur on the bumper. Accordingly, the strain gauge <NUM> can be provided at a predetermined location of the automobile body where the impact is assumed to occur. For example, the predetermined location may be set with respect to a door, a rear bumper, a spoiler, or other portions.

Further, the ECU <NUM> may have a function of controlling the open or close of a given door, which is used in the system for opening or closing a door, as described in the example of the fourth application, or may have a function of controlling a given wiper, as described in the example of the sixth application.

In the example of the eighth application, an example in which the strain gauge <NUM> is used to detect a malfunction of an engine or a supercharger is illustrated.

<FIG> is a schematic diagram illustrating an example of the strain gauge <NUM> arranged proximal to an automobile engine and supercharger. In <FIG>, the numeral <NUM> represents the supercharger, the numeral <NUM> represents an exhaust turbine, the numeral <NUM> represents an intake valve, and the numeral <NUM> represents an exhaust valve. The strain gauge <NUM> is disposed proximal to the supercharger <NUM>.

By disposing the strain gauge <NUM> proximal to a given engine, or a given supercharger such as a turbocharger or supercharger, malfunctions of the engine or the supercharger can be detected based on changes in pressure, for example. An engine speed can be decreased based on a detected result by the strain gauge <NUM>, or the engine can be stopped based on the detected result by the strain gauge <NUM>.

When temperature of the engine becomes high, a highly heat-resistant material such as ceramic (for example, alumina, zirconia, or a sapphire) is preferably used as the substrate <NUM> of the strain gauge <NUM>, instead of resin.

The preferred embodiments and the like have been described above in detail, but are not limited thereto. Various modifications and alternatives to the above embodiments and the like can be made without departing from a scope set forth in the claims.

This International application claims priority to <CIT>.

Claim 1:
An automotive accelerator (<NUM>) comprising:
a sensor (<NUM>, 6B) configured to detect a force to press the accelerator (<NUM>),
wherein the sensor (<NUM>, 6B) includes:
a flexible substrate (<NUM>);
a functional layer (<NUM>) formed of metal, an alloy, or a metal compound, the functional layer (<NUM>) being provided directly on one surface of the substrate (<NUM>); and
a resistor (<NUM>, 30B) formed of a film containing Cr, CrN, and Cr<NUM>N, the resistor (<NUM>, 30B) being provided directly on one surface of the functional layer (<NUM>), wherein a portion of the material that constitutes the functional layer (<NUM>) is diffused into the film containing Cr, CrN, and Cr<NUM>N,
wherein a main component of the resistor (<NUM>, 30B) is α-Cr,
wherein the functional layer (<NUM>) includes a function of promoting crystal growth of the α-Cr and depositing a film of which a main component is α-Cr, and
wherein the sensor (<NUM>, 6B) is configured to detect the force to press the accelerator (<NUM>) as a change in a resistance value of the resistor (<NUM>, 30B).