JP2003161662A - Pressure sensor and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a film pressure sensor which can form a scan electrode at micropitch, and also can detect pressure at micropitch because any load seldom transfers to adjacent scan electrodes even when the load is applied. <P>SOLUTION: In the pressure sensor, a conductive circuit is mounted on both faces of a piezoelectric resin film so as to be flush with the film surface. This conductive circuit comprises a plurality of parallel linear patterns, a connective circuit extending from one end of each linear pattern, and an electrode connected to the connective circuit, locating these linear patterns on both sides of the piezoelectric resin film crosswise each other. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a pressure sensor and a manufacturing method thereof. More specifically, the present invention relates to a film-shaped pressure sensor and a manufacturing method thereof.

[0002]

2. Description of the Related Art It has been widely practiced to obtain a film-shaped pressure sensor having flexibility. For example,
A resin having a piezoelectric property such as polyvinylidene fluoride is molded into a film, or a powder such as a ceramic having a piezoelectric property is added to an electrically insulating resin, and this is molded into a film to obtain Electrodes are vapor-deposited on both sides, or a conductor foil is attached.

For example, Japanese Patent Application Laid-Open No. 63-208734 and Japanese Patent No. 2557796 disclose a piezoelectric sensor in which a plurality of scanning electrodes are formed in a matrix on the front and back sides of a piezoelectric film.

However, in JP-A-63-208734, electrodes are produced by vapor deposition, and it is difficult to obtain a fine conductor circuit. Further, the piezoelectric film is polarized by applying a voltage to the scan electrodes formed in a matrix, but since the electric field is applied only to the intersections of the scan electrodes, the electric field cannot be applied uniformly. , It cannot be polarized efficiently.

Further, in Japanese Patent No. 2557796, scanning electrodes are formed by forming conductive films on both surfaces of a piezoelectric film and etching them. However, it is difficult to obtain a fine conductor circuit by etching, and the scanning electrodes are difficult to obtain. It is not possible to make the interval of fine. In addition, the scanning electrode 1 produced by etching has the piezoelectric film 1 as shown in FIG.
Since it is formed so as to project on the surface of 05, when a load is applied on the scan electrodes, the load is also transmitted to the scan electrodes that are adjacent to each other, and it is difficult to detect the pressure at a minute pitch.

[0006]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems in a film-shaped pressure sensor, allows the scanning electrodes to be formed at a fine pitch, and is adjacent even when a load is applied. An object of the present invention is to provide a film-shaped pressure sensor capable of detecting a pressure at a fine pitch and a method for manufacturing the film-shaped pressure sensor, in which a load is less likely to be transmitted to a matching scanning electrode.

[0007]

The pressure sensor of the present invention is characterized in that conductor circuits are embedded on both surfaces of a resin film having piezoelectricity so as to be flush with the surface of the film.

In the pressure sensor, the resin film having piezoelectricity is preferably polyvinylidene fluoride.

In the present invention, the conductor circuit preferably comprises a plurality of linear patterns arranged in parallel, connecting circuits extending from one end of each linear pattern, and electrodes connected to the connecting circuits. The linear pattern is
It is any one of the above-mentioned pressure sensors arranged so as to intersect with each other.

Further, in the above-mentioned sensor, more preferably, the linear patterns of the conductor circuit are more than the widths of the linear patterns between adjacent intersecting portions at the portions intersecting each other with the resin film having piezoelectricity interposed therebetween. Also has a wide width.

The present invention further includes (A) a step of forming a conductor circuit on a metal plate by electroplating, and (B) a conductor circuit surface formed on the metal plate on the front and back of the resin film having piezoelectricity. Facing each other and crimping so that the conductor circuit is embedded in the film, (C) applying a voltage between the front and back metal plates to polarize the resin film having piezoelectricity, and (D) the metal plate. Is a method for manufacturing a pressure sensor including a step of removing by etching. Also, the conductor circuit is preferably copper.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The resin film having piezoelectricity used in the present invention may be one generally used for pressure sensors. For example, a polymeric piezoelectric film made of polyvinylidene fluoride or ethylene fluoride, or a film formed by adding a piezoelectric ceramic powder such as lead zirconate titanate or barium titanate to a polymer solution can be used. The film formed of polyvinylidene fluoride has a large g31 constant representing the performance of the piezoelectric material as a pressure sensor, and is suitable for the pressure sensor of the present invention.

In the method of manufacturing the pressure sensor of the present invention, first, the patterned plating resist 102 is formed on the metal plate 101 (FIG. 2A). This plating resist 102 can be formed, for example, by laminating an ultraviolet-sensitive dry film resist on the metal plate 101, selectively exposing it with a negative film or the like, and then developing it. The metal plate 101 may be made of any material as long as it is suitable for this manufacturing method, but in particular, it has resistance to the chemical solution used and can be finally removed by etching. It is necessary. Examples of the material of the metal plate 101 include copper, copper alloy, 42 alloy, nickel and the like. In particular, a metal plate made of copper or a copper alloy is preferable because it can be easily obtained as a lead frame material and can be easily removed by etching after forming a circuit. Further, by using a copper plate having a thickness of 100 μm or more, positioning holes can be formed, so that the circuits can be easily aligned and stacked.

Next, a resist metal 103 is formed by electrolytic plating using the metal plate 101 as an electrolytic plating lead (power supply electrode) (FIG. 2B). By this electrolytic plating, a resist metal 103 is formed on a portion of the metal plate 101 where the plating resist 102 is not formed. The material of the resist metal 103 may be any material as long as it is suitable for this manufacturing method, but in particular, it may have resistance to a chemical solution used when finally removing the metal plate 101 by etching. is necessary. Examples of the material of the resist metal 103 include nickel, gold, tin,
Examples include silver, solder, palladium and the like. The purpose of forming the resist metal 103 is to prevent the conductor circuit 104 shown in FIG. 2C from being corroded or corroded by the chemical solution used for etching the metal plate 101. Therefore, when the conductor circuit 104 shown in FIG. 2C has resistance to the chemical solution used for etching the metal plate 101, the resist metal 103 is unnecessary. The resist metal 103 does not have to have the same pattern as the conductor circuit 104, and the resist metal 103 may be formed on the entire surface of the metal plate 101 before forming the plating resist 102 on the metal plate 101.

Next, the conductor circuit 104 is formed by electrolytic plating using the metal plate 101 as an electrolytic plating lead (feeding electrode) (FIG. 2C). By this electrolytic plating,
A conductor circuit 104 is formed on a portion of the metal plate 101 where the plating resist 102 is not formed. Conductor circuit 1
As the material of 04, any material may be used as long as it is suitable for this manufacturing method, but in particular, it is necessary to have resistance to a chemical solution used when finally removing the resist metal 103 by etching. Is. In practice, since the conductor circuit 104 finally exists inside the piezoelectric film 105, it is a good idea to select a resist metal 103 that can be etched with a chemical solution that does not erode or corrode the conductor circuit 104. As the material of the conductor circuit 104, for example,
Copper, nickel, gold, tin, silver, palladium, etc. may be mentioned. Furthermore, by using copper, a stable conductor circuit 104 with low resistance can be obtained.

Next, the plating resist 102 is removed to obtain a metal plate on which a conductor circuit is formed (FIG. 2 (d)).
Two metal plates thus obtained are prepared, and the conductor circuit surfaces of the metal plates are arranged so as to face the front and back surfaces of the resin film 105 having piezoelectricity, and the conductor circuits are embedded in the film. So that the metal plate is crimped (Fig. 2
(E)).

The method of crimping the metal plate is performed by a flat plate press,
A roll laminator method can be used. In the flat plate press, a method of applying pressure with a hydraulic press or a method of applying pressure while heating with a hot platen press can be used. You may press under reduced pressure by a vacuum press. It is better to use heating together with a roll laminator, using a vacuum laminator,
You may pressurize while heating under reduced pressure. The method of using both vacuum and heating is suitable for the production method of the present invention, because the conductor circuit can be embedded in the film without voids.

Next, using the metal plates exposed on the front and back as electrodes, a high voltage is applied to polarize the resin film having piezoelectricity to develop piezoelectricity. At this time, the whole may be heated.

Next, the metal plate 101 is removed by etching (FIG. 2 (f)). Metal plate 101 and conductor circuit 104
And a resist metal 103 is formed between the resist metal 103 and the resist metal 103. Since the resist metal 103 has resistance to a chemical used for removing the metal plate 101 by etching, the metal plate 101 is etched. Also resist metal 10
3 is not corroded and corroded, and as a result conductor circuit 1
04 is not eroded or corroded. When the material of the metal plate 101 is copper and the material of the resist metal is nickel, tin, or solder, a commercially available ammonia-based etching solution can be used. When the material of the metal plate 101 is copper and the material of the resist metal is gold, most etching solutions including ferric chloride solution and cupric chloride solution can be used.

Next, the resist metal 103 is removed by etching to obtain a film pressure sensor (see FIG. 2).
(G)). Since the conductor circuit 104 has resistance to a chemical solution used for removing the resist metal 103 by etching, the conductor circuit 104 is not corroded or corroded. Therefore, the conductor metal 104 is exposed by removing the resist metal 103. Conductor circuit 104
When the material is copper and the resist metal is nickel, tin, or solder, a commercially available solder / nickel stripping agent (for example, Pewtax: trade name, manufactured by Mitsubishi Gas Chemical Co., Inc.) can be used. Material of the conductor circuit 104 is copper, resist metal 1
When the material of 03 is gold, it is difficult to etch the resist metal 103 without eroding / corroding the conductor circuit 104. In this case, the step of etching the resist metal 103 may be omitted.

Although the conductor circuit can be formed in any shape, it is preferable that the conductor circuits are arranged in a matrix in order to detect a minute in-plane pressure. For example, the linear patterns (303, 313) arranged in parallel are formed so as to intersect each other on the front and back of the resin film having piezoelectricity (FIG. 3 (301, 302)). More preferably, the intersecting portions are orthogonal. When pressure is applied to a point where the patterns on the front and back sides intersect with each other with the resin film having piezoelectricity sandwiched therebetween, a potential difference is generated between the films having piezoelectricity sandwiched between the two patterns.

The conductor circuits may be formed in a linear pattern having the same width, but in the opposing conductor circuits (401, 411), the intersecting portion (403) at which the pressure of the linear pattern (402, 412) is desired to be detected. , 413) and the width between adjacent crossing portions on the same plane is narrowed, the adjacent crossing portions can be detected separately even when the pitch of the crossing portions is narrow. When forming a conductor circuit in a straight line with the same width, it is better to make the thickness of the conductor circuit as thin as possible, and when pressure is applied to the intersection, the output voltage is also applied to the next intersection due to the deformation of the conductor circuit. Can be prevented. In particular, in the pressure sensor of the present invention, since the conductor circuit is embedded in the resin film having piezoelectricity, there is an advantage that there is little disconnection even if the width of the connecting portion of the above-mentioned adjacent intersecting portions is narrowed. is there.

Further, the linear pattern of the conductor circuit (30
3, 313) are arranged in a matrix from one end,
Connecting circuit (30
4, 314) are formed at the tip of the electrodes (30
5, 315) to the front and back of the resin having piezoelectricity (301,
By forming the substrate 302), the matrix portion is formed with a fine pitch, and it is possible to easily connect to the outside.

[0024]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.

[Example 1] Surface-roughened 150 μm
Thick rolled copper plate (metal plate 101, Furukawa Electric Co., Ltd., EFT
EC-64T: trade name, a dry film resist (AQ-2058: trade name, manufactured by Asahi Kasei) is roll-laminated, exposed and developed using a predetermined negative film, and a plating resist required for forming the conductor circuit 104. (Plating resist 102) was formed. Next, nickel (resist metal 103) was formed by electrolytic plating using the rolled copper plate as a lead for electrolytic plating, and further electrolytic copper plating was performed to form 300 linear conductor circuits 104 arranged in parallel at a pitch of 50 μm. . In the conductor circuit, the thickness of nickel was 3 μm, the thickness of copper was 10 μm, the width of the intersecting portion was 35 μm, and the width of the connecting portion with the adjacent intersecting portion was 10 μm. Next, a polyvinylidene fluoride film having a thickness of 50 μm is prepared, and the two rolled copper plates with conductor circuits obtained above are arranged so that the conductor circuits face each other on both sides of the film, and the crossing portions of the conductor circuits are arranged. Were perpendicular to each other, and they were pressure bonded at 150 ° C. and 3 MPa using a hot platen press. Put the obtained laminate in a silicone oil bath at 60 ° C,
A rolled copper plate is used as an electrode, and a DC voltage of 300 V is applied to both ends.
The polyvinylidene fluoride film was polarized by applying for 0 minutes. Next, the rolled copper plates on both sides were removed by etching using an ammonia-based etching solution, and further, nickel was removed by etching using a solder / nickel stripping agent (Pewtax: trade name, manufactured by Mitsubishi Gas Chemical Co., Inc.). . One surface of the obtained pressure sensor was fixed to a glass plate with an insulating tape, and the other surface was pressed with a finger with a force of about 50 g. By processing the output signal obtained from each intersection, the fingerprint was obtained. Was able to be detected.

Comparative Example 1 A polyvinylidene fluoride film having a thickness of 50 μm was prepared, and rolled copper foil having a thickness of 18 μm was pressure-bonded to both surfaces at 150 ° C. and 3 MPa using a hot platen press. The obtained laminate was put in a silicone oil bath at 60 ° C., a rolled copper foil was used as an electrode, and a DC voltage of 300 V was applied to both ends for 10 minutes to polarize the polyvinylidene fluoride film. By forming a resist on a rolled copper foil and etching it, 300 conductor circuits arranged in parallel at a pitch of 50 μm were formed, but the copper foil was partially overetched in the etching process, and a uniform circuit could be obtained. I could not do it.

Comparative Example 2 A polyvinylidene fluoride film having a thickness of 50 μm was prepared, and rolled copper foils having a thickness of 18 μm were pressure-bonded on both sides at 150 ° C. and 3 MPa using a hot platen press. The obtained laminate was put in a silicone oil bath at 60 ° C., a rolled copper foil was used as an electrode, and a DC voltage of 300 V was applied to both ends for 10 minutes to polarize the polyvinylidene fluoride film. A resist was formed on the rolled copper foil, and etching was performed to form 150 conductor circuits having a width of 50 μm arranged in parallel at a pitch of 80 μm. The conductor circuit was linearly etched. At this time, the respective circuits were made to be orthogonal on the front and back of the film. One surface of the obtained pressure sensor was fixed to the glass plate with an insulating tape, and the other surface was pressed with a finger with a force of about 50 g. The output signal obtained was the crossing part corresponding to the crest of the fingerprint. A fingerprint could not be detected because an output signal was output from the adjacent crossing part of the electrode due to the pressure due to the distortion of the copper foil.

[0028]

According to the present invention, the scanning electrodes can be formed at a fine pitch, and even if a load is applied, the load is not easily transmitted to the adjacent scanning electrodes, and the pressure can be detected at a fine pitch. The pressure sensor of is obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a conventional pressure sensor.

FIG. 2 is a cross-sectional view showing an example of the method for manufacturing the pressure sensor according to the embodiment of the present invention.

FIG. 3 is a diagram showing conductor circuits on the front and back of a resin film having piezoelectricity.

FIG. 4 is a diagram showing an example in which a width of a crossing portion of a linear pattern in a conductor circuit is widened.

[Explanation of symbols]

1 scanning electrode 101 metal plate 102 plating resist 103 Resist metal 104 wiring pattern 105 Piezoelectric film 301 Resin film surface conductor circuit having piezoelectricity 302 Conductor circuit on backside of resin film having piezoelectricity 303, 313, 402, 412 Linear pattern 304,314 Connection circuit 305,315 electrodes 401 First Conductor Circuit 403,413 intersection 411 Second conductor circuit

Claims (6)

[Claims] 1. Both sides of a resin film having piezoelectricity,
A pressure sensor in which a conductor circuit is embedded so that it is flush with the surface of the film. 2. The pressure sensor according to claim 1, wherein the resin film having piezoelectricity is polyvinylidene fluoride. 3. A conductor circuit comprising a plurality of linear patterns arranged in parallel, connecting circuits extending from one end of each linear pattern, and electrodes connected to the connecting circuits. The pressure sensor according to claim 1 or 2, wherein the striped patterns are arranged so as to intersect each other. 4. The linear pattern has a width wider than a width of the linear pattern between adjacent intersecting portions at portions where the linear patterns intersect each other with the resin film having piezoelectricity interposed therebetween. pressure sensor. 5. A step of (A) forming a conductor circuit on a metal plate by electroplating, and (B) a front surface and a back surface of a resin film having piezoelectricity, the conductor circuit surfaces formed on the metal plate being opposed to each other. And (C) a step of applying a voltage between the front and back metal plates to polarize the resin film having piezoelectricity, and (D) removing the metal plates by etching. A method of manufacturing a pressure sensor, the method including the step of: 6. The method of manufacturing a pressure sensor according to claim 4, wherein the conductor circuit is copper.