JP4044541B2 - Method for manufacturing piezoelectric vibrator - Google Patents

Description

  The present invention relates to a piezoelectric vibrator that performs bending deformation, and more particularly, to a method for manufacturing a piezoelectric vibrator suitable as a piezoelectric vibrator for a diaphragm.

  Some diaphragms such as a diaphragm type small pump use a vibrator made of a piezoelectric ceramic plate (hereinafter referred to as a piezoelectric vibrator). For example, it is disclosed in Patent Document 1.

  Such a diaphragm has a configuration in which a piezoelectric bimorph formed by sandwiching an intermediate layer plate called a shim between two piezoelectric ceramic plates is molded entirely with an elastomer material such as silicone rubber. At that time, the lead wire for bending and vibrating the piezoelectric bimorph was constituted by soldering an electric wire to an electrode formed on the surface of the piezoelectric ceramic plate.

JP 2000-265963 A

  Incidentally, a piezoelectric vibrator for a diaphragm of a small pump is required to be downsized, particularly thin. There is a demand for thin pumps, especially for fuel cell fuel supply devices, injection of chemicals such as infusions, and water cooling for various electronic devices, etc., and thin areas that cannot be realized with conventional electromagnetic diaphragm-type small pumps and electromagnetic centrifugal pumps Application in is expected. For example, a diaphragm-type small pump for cooling a CPU of a notebook computer requires a height of 6 mm or less because of space. At that time, the thickness of the piezoelectric vibrator is 1.5 mm or less because a mechanism part such as a check valve for generating a flow or a casing for fixing the piezoelectric vibrator is required at least about 4.5 mm. It will be necessary.

  However, a conventional piezoelectric vibrator for a diaphragm has a structure in which an electric wire is connected to a surface electrode with solder and this is covered with silicone rubber or the like, so that silicone rubber or the like is formed to a thickness greater than the solder point height. There is a need. Furthermore, it is necessary to affix a waterproof film such as a PTFE (fluororesin) sheet on the water contact surface side in order to suppress water permeability. For this reason, the thickness of the piezoelectric diaphragm for a conventional diaphragm type small pump is: thickness of piezoelectric vibrator = piezoelectric bimorph thickness + mold thickness × 2 layers + waterproof film thickness, for example, piezoelectric bimorph thickness: 1.0 mm When the mold thickness is 1.0 mm and the waterproof film thickness is 0.1 mm, the thickness of the piezoelectric vibrator is 1.0 mm + 1.0 mm × 2 layers + 0.1 mm = 3.1 mm. As a result, the total thickness of the diaphragm type small pump including the casing thickness of 4.5 mm is 7.6 mm, and there is a problem that it cannot be used for cooling the laptop computer.

  In addition, in the conventional piezoelectric bimorph used for this kind of application, an intermediate layer called shim material is configured using a metal plate such as a stainless steel alloy or a copper alloy, and a part of this is used as a solder attachment part other than the adhesive part. It is usual to take a configuration in which the lead wire to the drive power source is taken out by exposing the wire and soldering the wire. However, since the solder attachment portion is exposed to the outside of the piezoelectric ceramic and is a portion to which voltage is applied, it has been necessary to mold with an insulating elastomer material such as silicone rubber. In addition, since the solder fixing part is covered with an elastomeric material such as silicone rubber, the solder point is stressed every time the piezoelectric vibrator is bent and the wire is peeled off from the piezoelectric ceramic surface electrode when used continuously. There was also a problem.

  Accordingly, an object of the present invention is to provide a method of manufacturing a piezoelectric vibrator that is used in a piezoelectric vibrator for a diaphragm and the like, and is thinner, highly reliable, and easy to manufacture.

In order to solve the problem, a method for manufacturing a piezoelectric vibrator according to the present invention includes a bimorph-type piezoelectric vibrator bonded so as to sandwich an elastic plate between two piezoelectric ceramic plates, and bonded to the outer surface of the piezoelectric ceramic plate. In the method of manufacturing a piezoelectric vibrator in which a lead wire is drawn out from an electrode formed on a main surface of the piezoelectric ceramic plate by a flat cable, the elastic plate is made of a thermosetting resin as a fiber material. A sheet-like prepreg impregnated with a wire core of the flat cable sandwiched between the surface of the prepreg and the electrode of the piezoelectric ceramic plate, and the moisture resistance of the electrode on the other main surface of the piezoelectric ceramic plate Sandwiching the other core of the flat cable together with an adhesive between the sheets and pressurizing the whole, and the prepreg and the front by heating Characterized in that it comprises a step of curing the adhesive.

The present invention will be further described. In the present invention, a sheet, rubber plate, resin material, etc. having moisture resistance is applied to the surface of the piezoelectric bimorph that applies the strain change of the piezoelectric body, moisture prevention, electrical insulation and taking out to the drive power supply One of the features is to take out with a flat cable sandwiched between the sheet, rubber plate, resin material and the like and the surface electrode of the piezoelectric ceramic plate.

In the configuration of the present invention, the moisture-proof sheet has three roles of moisture-proof, electrical insulation, and flat cable fixing. Regarding moisture proofing, by preventing water from permeating the surface of the piezoelectric bimorph as a material of the surface of the diaphragm, there is an effect of protecting the piezoelectric bimorph. Regarding electrical insulation, there is an effect of electrically insulating the liquid and the piezoelectric bimorph surface electrode when the conductive liquid comes into contact therewith. The flat cable is fixed by arranging the flat cable so as to be in contact with the electrode formed on the surface of the piezoelectric ceramic, and sandwiching and adhering it with a moisture-proof sheet. In the conventional method of fixing the wire with the solder, the thickness of the solder point is obscured. Therefore, it is indispensable to mold the elastomer material with a thickness equal to or greater than the thickness of the solder point. However, the flat cable of the present invention is sandwiched and bonded. This method reduces the thickness of the flat cable, so that even when a moisture-proof sheet such as a Teflon (registered trademark) sheet is attached, the surface has small irregularities and the piezoelectric vibrator is fixed with a resin O-ring. If this is the case, the problem of airtightness will not occur. It is desirable to use a material that is as soft as possible for the moisture-proof sheet so as not to prevent the displacement of the piezoelectric bimorph that performs bending vibration.

The present invention is a semi-cured state in which a thermosetting resin is impregnated in a fiber material such as carbon fiber, glass fiber, and aramid fiber, which is called a prepreg, in an intermediate layer serving as a shim material in a piezoelectric bimorph that applies a strain change of a piezoelectric body One of the characteristics is that it is made of a tape-shaped intermediate material, and a flat cable is sandwiched and cured when the shim material and the piezoelectric body are bonded together by thermosetting to form a drive power supply electric wire. According to the present invention, an intermediate layer called shim is formed and a drive power supply is taken out by arranging a flat cable so as to be in contact with an electrode formed on the surface of a piezoelectric ceramic, and sandwiching and bonding with a tape-like intermediate material of a prepreg. A structure in which electric wires can be formed simultaneously. In the conventional method of connecting electric wires with solder, it is indispensable to mold the insulating elastomer material to electrically insulate the solder points. However, with the method of sandwiching and bonding the flat cable of the present invention, all the wire parts of the flat cable are used. Since it is sandwiched and cured between an intermediate layer called a shim and piezoelectric ceramics, a portion where a potential difference occurs is not exposed to the outside of the piezoelectric bimorph, and there is no need for processing such as molding. The tape-like intermediate material of the prepreg used for the shim material may be a conductive material such as carbon fiber or an insulating material such as glass fiber as long as the flat cable to be sandwiched is in contact with the electrode formed on the surface of the piezoelectric ceramic. Absent.

The present invention, be formed driving power deriving the wire is simultaneously bonded or cured in manufacturing piezoelectric bimorph first or second Sensing number three or more flat cables so that the configuration of the present invention arranged desirable. In this configuration, between the electrode formed on the surface of one piezoelectric ceramic and the moisture-proof sheet, between the electrode formed on the surface of the other piezoelectric ceramic and the moisture-proof sheet, an intermediate layer called a shim material, and at least one piezoelectric ceramic A flat cable is sandwiched between the electrodes formed on the surface. The flat cable may be one in which a plurality of conductors are formed on the same insulator, or one in which a plurality of conductors are respectively formed. It is desirable that the flat cable has a conductor thickness (dimension in the thickness direction) of 0.05 m or less. When the flat cable is sandwiched and bonded between the electrode formed on the surface of the piezoelectric ceramic and the moisture-proof sheet, a step is formed on the surface of the moisture-proof sheet. If this level difference is large, there will be a problem of airtightness such as a gap formed when fixed on the O-ring to cause liquid leakage. However, if a flat cable having a thickness of 0.05 mm or less is used, the effect of the level difference is reduced, and if it is fixed with an O-ring made of an elastomer material such as a fluororesin, there is no problem of airtightness such as liquid leakage. Therefore, it is desirable to use a thinner flat cable within the allowable range of the voltage and current of the applied power supply.

  With this configuration, it is possible to provide a diaphragm vibrator for a diaphragm having a lower profile because the thickness of the solder point is eliminated. In addition, it is possible to provide a piezoelectric vibrator for a diaphragm that is not affected by the vulnerability associated with soldering.

The present invention, the moisture-proof sheet Shore hardness D80 or less and a thickness may be desirable to use polymeric materials 0.01～0.50Mm. When the moisture-proof sheet is a hard material with little elongation, displacement of the piezoelectric bimorph is hindered and performance as a vibrator is deteriorated. Similarly, when the thickness of the moisture-proof sheet is increased, the displacement of the piezoelectric bimorph is hindered, and the performance as a vibrator is deteriorated. It is necessary to select at least the range of the hardness and thickness. Needless to say, it is necessary to take a moisture-proof sheet having an optimal hardness and thickness in consideration of moisture resistance and strength.

In the present invention, as the polymer material, fluorine resin, neoprene rubber, may be used a urethane polymer.

In the present invention, it is possible to produce driving power deriving the wire is simultaneously bonded or cured in manufacturing piezoelectric bimorph arranged Sensing number three or more flat cables. In this configuration, between the electrode formed on the surface of one piezoelectric ceramic and the moisture-proof sheet, between the electrode formed on the surface of the other piezoelectric ceramic and the moisture-proof sheet, an intermediate layer called a shim material, and at least one piezoelectric ceramic Each of the flat cables is sandwiched between electrodes formed on the surface and is cured by pressure to form a piezoelectric vibrator by a single process. With this configuration, the soldering process becomes unnecessary, the operation cost can be reduced, and a cheaper piezoelectric vibrator can be provided.

  As described above, according to the configuration of the present invention, it is possible to manufacture a piezoelectric vibrator for a diaphragm that is thinner than the conventional one, and a lower-profile application that could not be used with the conventional vibrator. However, a method of manufacturing a piezoelectric vibrator for a diaphragm having sufficient performance can be provided. In addition, since the manufacturing method is simplified, it is possible to provide a method for manufacturing a piezoelectric vibrator for a diaphragm that is less expensive than the conventional one.

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing a piezoelectric vibrator manufactured according to the present invention. The overall shape of the piezoelectric vibrator is a shape in which a flat cable terminal is drawn from a disk-like piezoelectric bimorph. In FIG. 1, la and lb are piezoelectric ceramic plates having electrodes formed on their surfaces, 2 is a shim material, a composite of a fiber material and a polymer material obtained by curing a prepreg, and 3a and 3b are moisture-proof sheets. 4 is a flat cable, 5a, 5b, 5c, and 5d are the cores (conductive wires) of the flat cable.

  In the manufacturing method, (1) joining the shim material 2 and the piezoelectric ceramic plates 1a and 1b, (2) joining the electrodes of the piezoelectric ceramic plates 1a and 1b and the wire cores 5c and 5d, and (3) the piezoelectric ceramic plate 1a. 1b and the wire cores 5a and 5b, and (4) the piezoelectric ceramic plates 1a and 1b and the moisture-proof sheets 3a and 3b are joined together.

  In this joining, the prepreg to be the shim material 2 plays an important role. That is, a prepreg is used that not only functions as an elastic plate after being cured, but also functions as an adhesive with the piezoelectric ceramic plates 1a, 1b and the wire cores 5c, 5d. Further, since the joining by the prepreg is performed simultaneously with the adhesion between the piezoelectric ceramic plate 1a or 1b and the moisture-proof sheet 3a or 3b, it is desirable that the curing temperature is close.

  Further, the moisture-proof sheets 3a and 3b not only have a moisture-proof function, but also do not attenuate bimorph vibration, and also have an important electrical insulating property, and therefore, polymer materials such as fluororesin, neoprene rubber, and urethane polymer are used.

  By the way, when the conductivity of the shim material 2 is sufficient, either the wire core 5c or 5d of the flat cable 4 may be omitted, and a flat cable having three wire cores (conductive wires) may be used. In addition, when the electrical resistance is increased by limiting the thickness (dimension in the thickness direction) of the flat cable core, connect two or more cores to one electrode of the piezoelectric ceramic plate. Also good.

Next, an example will be given and further described. The external dimensions of the piezoelectric vibrator manufactured by the manufacturing method of this example are 37 mm in diameter and 1.4 mm in thickness, and the cross section is as shown in FIG. La and lb are piezoelectric ceramic plates having a diameter of 35 mm and a thickness of 0.36 mm, and a silver electrode having a diameter of 33 mm is formed on the surface. N-17 material made by NEC TOKIN was used as the material. The relative dielectric constant is 4200, and the piezoelectric constant is d ₃₁ = −280 × 10 ⁻¹² m / V. 2 is a carbon fiber shim material having a diameter of 35 mm and a thickness of 0.25 mm used for the intermediate layer, and 3a and 3b are moisture-proof sheets having a thickness of 0.2 mm using PTFE sheets. 4 is a flat cable, 5a, 5b, 5c, and 5d are flat cable cores, and the wire thickness is 0.035 mm. In this example, a flat cable having four wire cores was used. The wire cores 5a and 5c are in contact with the upper and lower electrodes of the piezoelectric ceramic plate 1a, respectively. The wire cores 5b and 5d are in contact with the upper and lower electrodes of the piezoelectric ceramic plate 1b.

Before showing the method of manufacturing the piezoelectric vibrator, a comparative example manufactured by the conventional technique will be described.

  FIG. 5 shows a cross section of a piezoelectric vibrator for a diaphragm small pump of a comparative example. The outer dimensions are a diameter of 37 mm and a thickness of 3.1 mm, and 6a and 6b are piezoelectric ceramic plates having a diameter of 35 mm and a thickness of 0.36 mm as in the above embodiment, and a silver electrode having a diameter of 33 mm is formed on the surface. N-17 material manufactured by NEC TOKIN was used. 7 is a shim material of a phosphor bronze plate having a thickness of 0.25 mm used as an intermediate layer, and 8 is a silicone resin having a total thickness of 3 mm. 9 is a waterproof sheet having a thickness of 0.1 mm, and a PTFE sheet was used. 10a, 10b and 10c are electric wires, the electric wire 10a is soldered to the shim material 7, the electric wires 10b and 10c are soldered to the surface electrodes of the piezoelectric ceramic plates 6a and 6b, respectively, and 11a, 11b and 11c are solder points.

Table 1 shows a comparison of piezoelectric vibrators for diaphragm small pumps manufactured according to the embodiment of the present invention and comparative examples.

As shown in Table 1, when the piezoelectric vibrators for diaphragm small pumps according to the examples of the present invention and the comparative examples are compared, the thickness of the present invention can be reduced to half or less although the diameter does not change in the present invention. In the case of the conventional piezoelectric vibrator, the solder points shown in 11b and 11c are about 0.5 to 0.7 mm in consideration of the height of the continuous electric wire. In order to cover the convex part of the solder point with a mold, it is manufactured. In consideration of the variation, it is necessary to have a thickness of about 1 mm from the surface of the piezoelectric ceramic plate. Further, since the silicone rubber has a high water absorption rate and may absorb water from the surface in contact with water and affect the quality of the internal piezoelectric bimorph, it is necessary to attach a waterproof sheet to at least the surface in contact with water. As a result, the thickness of the piezoelectric vibrator = piezoelectric bimorph thickness + mold thickness × 2 layers + waterproof film thickness. Piezoelectric bimorph thickness: (0.36 × 2 + 0.25) mm, mold thickness: 1.0 mm, waterproof sheet Since the thickness is 0.1 mm, the thickness of the piezoelectric vibrator = about 1.0 mm + 1.0 mm × 2 layers + 0.1 mm = about 3.1 mm.

On the other hand, according to the embodiment of the present invention, by directly attaching a waterproof sheet (moisture-proof sheet) to the piezoelectric ceramic, the thickness of the piezoelectric vibrator of this embodiment = piezoelectric bimorph thickness + waterproof sheet × 2 layers, Piezoelectric bimorph thickness: (0.36 × 2 + 0.25) mm and waterproof sheet thickness 0.2 mm, so that the thickness of the piezoelectric vibrator = about 1.0 mm + 0.2 mm × 2 layers = about 1.4 mm. As a result, a low profile of about 1.7 mm can be realized, and it can be used for applications requiring high profile such as thin pumps.

Next, we compared the amount of displacement of the diaphragm miniature piezoelectric vibrator pump of Comparative Example to be due to an embodiment of the present invention. The piezoelectric vibrator is fixed by an O-ring having a diameter of 33 mm so as to suppress the top and bottom of the piezoelectric vibrator. A voltage of 100 Vrms is applied between the wire cores 5a and 5b and the wire cores 5c and 5d to cause the piezoelectric vibrator to flexurally vibrate. The amount was measured. As a result, a sufficient performance can be obtained as the piezoelectric vibrator diaphragm has been confirmed by a large difference in the amount of displacement in the diaphragm miniature piezoelectric vibrator pump of Comparative Example with those according to this embodiment the present invention not observed.

  Next, the manufacturing process of the present embodiment will be described. First, the piezoelectric ceramic plates 1a and 1b are manufactured by the following steps.

1) An organic binder and an organic solvent are mixed into a piezoelectric ceramic raw material powder (N-17 material manufactured by NEC TOKIN) to make a slurry.
2) Sheet the slurry with the doctor blade method.
3) An electrode paste mainly composed of silver and palladium is printed on the required sheet as an internal electrode layer and dried.
4) The sheets are stacked and heated and pressed to cut into the required shape.
5) Heat from 500 ° C to 600 ° C and incinerate organic substances such as binder in a few hours.
6) Firing is performed in a sealed container at a temperature of 1000 ° C. to 1200 ° C. for 1 to 6 hours.
7) Apply or print the electrode for the electric terminal and the outermost skin on the end face, and bake at 500 to 600 ° C.
8) Heat to about 100 ° C. in insulating oil and apply a DC electric field of 2 to 3 kV / mm between the terminals for polarization treatment.

  Next, the next process will be described based on the drawings.

FIG. 3 is an exploded perspective view showing the piezoelectric vibrator manufactured according to this embodiment. The flat cable 4 has four wire cores 5a, 5b, 5c, and 5d. The wire core 5a is the upper surface electrode of the piezoelectric ceramic plate 1a, the wire core 5b is the lower surface electrode of the piezoelectric ceramic plate 1b, the wire core 5c is the lower surface electrode of the piezoelectric ceramic plate 1a, and the wire core 5d is the electrode on the upper surface of the piezoelectric ceramic plate 1b. And put them in contact with each other. The piezoelectric ceramic plates 1a and 1b and the shim material 2 (see FIG. 1) are bonded with a semi-cured adhesive impregnated in the carbon fiber of the prepreg 32. The ceramic plates 1a and 1b and the moisture-proof sheets 3a and 3b are bonded by applying an epoxy adhesive. After all the members are bonded together, they are heated and cured at 130 ° C. for 90 minutes while being pressurized. At this time, it is important to select a semi-cured adhesive impregnated in the carbon fiber of the prepreg 32 and an epoxy adhesive that are cured under the same heating conditions.

  As a result, the obtained piezoelectric vibrator is configured such that the flat cable 4 comes out of the circular bimorph 41 as shown in the perspective view of FIG.

  Next, the manufacturing process of the piezoelectric vibrator for the diaphragm small pump of the example of the present invention and the comparative example will be compared. FIG. 2 shows an outline of the manufacturing process of the embodiment of the present invention and the comparative example, FIG. 2 (a) is a flowchart showing the process of the embodiment of the present invention, and FIG. 2 (b) is a flowchart showing the process of the comparative example. is there.

  As described above, in the piezoelectric vibrator for the diaphragm small-sized pump of the comparative example, since there are a soldering process and a silicone resin molding process, the number of processes is increased, which hinders cost reduction. On the other hand, in the present invention, since the bonding of each member can be performed by one process, the number of processes can be reduced and a cheaper piezoelectric vibrator can be provided.

Sectional drawing which shows the piezoelectric vibrator produced by this invention. The outline of the manufacturing process of the Example of this invention and a comparative example is shown, Fig.2 (a) is a flowchart which shows the process of the Example of this invention, FIG.2 (b) is the flowchart which shows the process of a comparative example. The disassembled perspective view of the piezoelectric vibrator produced by the Example. FIG. 3 is an external perspective view of a piezoelectric vibrator manufactured according to an example. Sectional drawing of the piezoelectric vibrator of a comparative example.

Explanation of symbols

1a, 1b, 6a, 6b Piezoelectric ceramic plates 2, 7 Shim materials 3a, 3b Moisture-proof sheet 4 Flat cables 5a, 5b, 5c, 5d Wire core 8 Silicone resin 9 Waterproof sheets 10a, 10b, 10c Electric wires 11a, 11b, 11c Solder Point 32 Prepreg 41 Circular bimorph

Claims (1)

A bimorph type piezoelectric vibrator joined so as to sandwich an elastic plate between two piezoelectric ceramic plates, and a moisture-proof sheet joined to the outer surface of the piezoelectric ceramic plate, and formed on the main surface of the piezoelectric ceramic plate In the method for manufacturing a piezoelectric vibrator in which a lead wire is drawn out from an electrode by a flat cable, the elastic plate is a sheet-like prepreg in which a fiber material is impregnated with a thermosetting resin , and the surface of the prepreg and the piezoelectric ceramic plate The wire core of the flat cable is sandwiched between the electrode and the electrode of the other main surface of the piezoelectric ceramic plate and the other wire core together with the adhesive between the moisture-proof sheet and the whole of the flat cable. And a step of curing the prepreg and the adhesive by increasing the temperature. Method.

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