JPH01295169A - Composite diaphragm and its production and piezoelectric acceleration sensor formed by using composite diaphragm - Google Patents

Abstract

PURPOSE:To obtain stable output and excellent frequency characteristics by forming a tight contact layer consisting of a 1st metallic layer consisting of chromium or titanium and the 2nd metallic layer consisting of an arbitrary metal on a piezoelectric material layer and forming a vibration film thereon, thereby forming the composite diaphragm. CONSTITUTION:The composite diaphragm 1 is constituted by forming the tight contact layer 13 consisting of the 1st metallic layer 4 and the 2nd metallic layer 5 on the piezoelectric material layer 2 formed on an electrode not shown in the figure and laminating the vibration film 6 on this layer 3. The piezoelectric layer 2 consists of a high-polymer piezoelectric film. The metallic layer 4 consists of the titanium or chromium and the film thickness thereof is >=100A. The metallic layer 5 consists of an arbitrary metal. The vibration film 6 consists of a material which has a relatively high Young's modulus and is strong to impact force. The decrease in the output and the fluctuation, etc., in the output by the viscoelasticity of the adhesive layer are thereby decreased and the composite diaphragm having high performance is obtd.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a composite diaphragm with stable output and excellent frequency characteristics over a long period of time, a method for manufacturing the same, and a method for using this composite diaphragm as a piezoelectric element. This relates to piezoelectric acceleration sensors.

[Prior art and its problems] Polymer-based piezoelectric materials such as polyvinylidene fluoride have P b
(Z r, Ti) 03 series (abbreviated as PZT) and P
bT i O3, B aT io , (P b, L
a) (Z r, Ti) 03 (abbreviated as P LZT) Compared to ceramic-based piezoelectric materials, (1) Excellent flexibility.

■It has excellent processability and can be made into thin films and large areas.

■Since the dielectric constant is small, the voltage output constant (g) is large.

■Excellent insulation.

This feature makes it suitable for use as a diaphragm for piezoelectric elements and acoustic components.

However, when a polymeric piezoelectric film is used alone as a piezoelectric element or a diaphragm, there are problems in that the resonant frequency becomes low and the protrusion changes as the frequency changes. In order to solve this problem, attempts have been made to use a metal foil with a high elastic modulus bonded to a polymer piezoelectric film, but this method requires an adhesive layer between the metal foil and the polymer piezoelectric film. , a decrease in output due to the viscoelasticity of the adhesive layer,
New problems arise, such as variations in output due to non-uniformity of the adhesive layer and decreased durability due to peeling.

This invention was made in order to solve the problem described in item 1, and provides a composite diaphragm that can provide stable output and excellent frequency characteristics over a long period of time, a method for manufacturing the same, and a method for manufacturing the composite diaphragm. 3. ``Means for Solving the Problems'' The composite diaphragm according to claim 1 of the present invention has a film thickness of 10
An adhesion layer consisting of a first metal layer made of 0 or more chromium or titanium and a second metal layer made of any metal is placed on one or both sides of the piezoelectric layer made of a polymeric piezoelectric film. In order to manufacture this composite diaphragm, a deposition rate of 500% is applied to one or both sides of the piezoelectric layer.
Forming a 146th metal layer and a second metal layer consecutively without breaking airtightness using a sputtering method of Å/s or less to form an adhesive layer, and forming a vibrating membrane on one of the adhesive layers by an electroplating method; or on one or both sides of the piezoelectric layer,
The first and second metal layers are successively formed and adhered without breaking airtightness using a vacuum evaporation method with a distance between the piezoelectric layer and the evaporation source of 20 cm or more and 50 cm or less and a pressure of 2 X l O-5 Torr or less. The solution was to form a vibrating membrane on one of the adhesion layers by electroplating.

=3- Furthermore, the piezoelectric acceleration sensor according to claim 4 of the present invention has a composite diaphragm according to claim 1 as a means for solving the problem.

[Operation] An adhesive layer consisting of a first metal layer made of chromium or titanium and a second metal layer made of any metal is formed on the piezoelectric layer, and a vibrating membrane is formed on this to generate complex vibration. Since it is made of a plate, it is possible to increase the adhesion between the piezoelectric layer and the diaphragm, and since no adhesive is used, the characteristics of the piezoelectric layer do not deteriorate, and the resonant frequency of the composite diaphragm can be increased. It is possible to increase the frequency range for measurement and measurement.

Further, an adhesive layer consisting of the first and second metal layers is formed on the piezoelectric layer by vacuum evaporation or sputtering.
Since the layers are formed continuously without breaking airtightness, an oxide layer can be formed between each layer, and the adhesion between each layer can be increased.

Furthermore, since the adhesion layer is formed by vacuum evaporation or sputtering under mild conditions, -4 = the piezoelectric layer is not altered by heat during manufacture.

Furthermore, if the vibrating membrane is formed by electroplating, a uniform vibrating membrane with few pits can be easily obtained, and the vibrating membrane can be formed at room temperature, thereby preventing thermal deformation of the piezoelectric layer and deterioration of piezoelectric properties. I'm never invited.

In addition, a composite diaphragm with excellent frequency and piezoelectric characteristics is used, and acceleration is detected from the amount of electricity generated as the composite diaphragm is distorted, making it possible to use a piezoelectric acceleration sensor that can perform highly sensitive measurements. can.

[Example] The present invention will be explained in detail below.

FIG. 1 shows an example of a composite diaphragm 1 of the present invention. This composite diaphragm 1 includes a piezoelectric layer 2 formed on an electrode (not shown) and an adhesion layer 3 made of a first metal layer 4 and a second metal layer 5. A vibrating membrane 6 is laminated thereon.

This piezoelectric layer 2 is made of a polymeric piezoelectric film, and its +N material includes polyvinyl fluoride, polyhynylidene fluoride (PVDF), polyvinyl chloride, nylon 9, nylon 11, polycarbonate, poly(m-phenylene isophthalate). (amide) vinylidene fluoride-edileno tetrafluoride copolymer, vinylidene fluoride-vinyl fluoride copolymer,
Vinylidene fluoride-ethylene trifluoride copolymer, vinylidene cyanide-vinyl acetate copolymer, a mixture of two or more thereof, or a mixture of these and other thermoplastic resins are suitable. In addition to this, P b(Z
r, T i)03, PbTiO3, (P b, L
a) (Z r, Ti)03, BaTiO2, Ba(
Z r, T i) 03, (B a, S r) T103
A mixture of a fine powder of an inorganic piezoelectric material such as a thermoplastic resin or a thermosetting resin in a polymer such as a thermoplastic resin or a thermosetting resin may also be used.

The adhesive layer 3 formed on the piezoelectric layer 2 is for bonding the piezoelectric layer 2 and the vibrating membrane 6, and is composed of a first metal layer 4 and a second metal layer 5. ing. This first metal layer 4 is made of titanium or chromium, which is a material with a small mass so as not to adversely affect the vibration of the diaphragm 6, and has high mechanical strength in order to improve the durability of the composite diaphragm 1. The thickness is preferably 100 Å or more. If the film thickness is less than 100 mm, it will not be possible to obtain sufficient strength to bring the piezoelectric layer 2 and the vibrating membrane 6 into close contact. The second metal layer 5 is used as an electrode when forming the vibrating membrane 6 by electroplating on the first metal layer 4 made of titanium or chromium having high electrical resistance, and is made of any metal. However, metals such as nickel, copper, silver, platinum, and gold, which have relatively high conductivity and are not corroded by plating solutions, are particularly suitable. Second
If the vibrating membrane 6 is formed directly on the first metal layer 4 by electroplating without providing the metal layer 5, the electric resistance of titanium or chromium constituting the first metal layer 4 will cause vibrations to be caused by the electroplating. It is not possible to increase the current density when forming the membrane 6, and the vibrating membrane 6 thus formed has coarse particles and lacks adhesion.

The vibrating membrane 6 laminated on the adhesive layer 3 is made of a material that has a relatively high Young's modulus and is strong against impact. Examples of these materials include iron, copper, nickel, chromium, gold, silver, and tin. One metal, copper-tin alloy, nickel alloy, etc.

In this example, the adhesive layer 3 was formed only on one side of the piezoelectric layer 2, but as shown in FIG. When a composite diaphragm 1 is obtained by laminating a diaphragm 6 on the diaphragm 6, it becomes an electrode with superior adhesion to the piezoelectric layer 2 and corrosion resistance compared to conventional electrode materials.
The adhesion layer 3 on which the diaphragm 6 is not laminated can be used, which is suitable for improving the corrosion resistance and strength of the composite diaphragm 1.

To manufacture such a composite diaphragm 1, a piezoelectric layer 2 is first prepared, and a first metal layer 4 and a second metal layer are deposited on this piezoelectric layer 2 by sputtering or vacuum deposition without breaking the airtightness. The metal layer 5 is formed continuously. Adhesion layer 3
Forming the first metal layer 4 and the second metal layer 5 constituting the first metal layer 4 continuously by a sputtering method or a vacuum evaporation method without breaking airtightness is a method for forming the first metal layer 4. 8- It is difficult to deposit chromium or titanium by chemical methods such as plating, and the characteristics of the polymer piezoelectric film constituting the piezoelectric layer 2 are difficult to deposit at temperatures close to the melting points of these metals. This is because formation at a temperature close to room temperature is preferable since deterioration occurs. For these reasons, when using the sputtering method, the deposition rate is 5
A deposition rate of 00 Å/s or less is desirable; if the deposition rate is higher than this, the sputtered metal particles will become large and coarse, and the adhesion with the piezoelectric layer 2 may deteriorate, resulting in peeling, which is not preferable. In addition, when using the vacuum evaporation method, the pressure is
It is desirable to maintain the X I at 0-5 Torr or less, and the distance between the evaporation source and the sample to be 20 cm or more and less than 50 cm,
If the pressure is further increased or the distance to the evaporation source is shortened, the piezoelectric layer 2 will be thermally denatured by the heat of the metal particles being evaporated, which is undesirable.
If it is more than cm, the deposition rate of the metal particles will become extremely low, which is not preferable. Furthermore, since the first metal layer 4 and the second metal layer 5 are formed continuously without breaking airtightness, an oxide layer is not formed between each layer, so that the adhesion between each layer is improved. It can improve the properties.

A piezoelectric layer 2 with an adhesive layer 3 formed thereon by the above process.
The vibrating membrane 6 can be formed on the second metal layer 5 by immersing the vibrating membrane 6 in a plating solution containing metal ions constituting the vibrating membrane 6 and performing electroplating using the second metal layer 5 as a cathode. can. The plating conditions at this time are, for example, to form the vibrating membrane 6 by nickel plating, a nickel sulfamate bath is used, electrolysis is performed by a constant current method, and the current density I (mA
/am2) and the thickness t (μm) of the electrode metal using the equation (1
) is desirable.

■≦50×t (1) If the current density l exceeds this condition, the formed plating film will be burnt and many pits will appear on its surface.

In the composite diaphragm 1 of the present invention, the diaphragm 6 is formed by plating, so deterioration of the diaphragm 1 due to burns during plating and non-uniformity of the diaphragm due to a large number of pits may deteriorate the characteristics of the composite diaphragm 1. Preferably avoided in order to connect directly.

Furthermore, if this vibrating membrane 6 is formed by electroless plating,
This is not preferable since the adhesion with the adhesive layer 3 may deteriorate and peeling may occur.

Since the composite diaphragm l formed in this way is made by adhering the piezoelectric layer 2 and the diaphragm 6 to each other through the adhesive layer 3, the piezoelectric layer and the diaphragm are bonded together using an adhesive. Compared to conventional diaphragms made of diaphragms, there is no output drop in the low frequency range, output variation is reduced, and the resonant frequency is higher, resulting in a wider measurement frequency range. Furthermore, after forming the first metal layer 4 and the second metal layer 5 constituting the adhesion layer 3 all at once without breaking airtightness, the vibrating membrane 6 was formed on the adhesion layer 3 by electroplating. No oxide layer is formed between the layers, and the piezoelectric layer 2 and adhesive layer 3
The adhesion between the adhesion layer 3 and the diaphragm 6 is increased, separation can be prevented, and a highly durable composite diaphragm can be obtained. Further, the composite diaphragm 1 shown in FIG.
In this case, adhesive layers 3 are provided on both sides of the piezoelectric layer 2, and the adhesive layer 3 on which the diaphragm 6 is not formed can be used as an electrode, resulting in improved durability compared to conventional diaphragms. can be improved.

3 and 4 show a detection section 8 of a piezoelectric acceleration sensor 7 using the composite diaphragm 1 of the present invention. This detection part 8 is formed by forming a concentric circular hole 9 with a diameter d in the center of the composite diaphragm l of the present invention to form an annular shape, and the peripheral edge thereof is sandwiched by a fixed frame 1O11O, which is also annular. The composite diaphragm 1 consists of a piezoelectric layer 2 made of a polymer piezoelectric film formed on an annular electrode (not shown), and a titanium or chromium film with a thickness of 100 Å or more on the piezoelectric layer 2. A first metal layer 4 and an arbitrary metal layer 5 consisting of
The second metal layer 5 is formed by forming an adhesion layer 3 continuously without breaking airtightness, and then forming a vibrating membrane 6 on this adhesion layer 3 by electroplating, and the second metal layer 5 is used as an electrode. is also working. As shown in FIG. 5, the detection unit 8 having the above configuration is housed in a conductive shield case 11, and includes an electrode (not shown) on which a piezoelectric layer 2 is formed and a second metal layer. 5 is attached with a terminal (not shown) for extracting an electrical signal generated by the vibration of the composite diaphragm l, and the output signal from this terminal is measured via the impedance conversion circuit 12. It has become. Further, the terminal of the detection section 8 and the impedance conversion circuit 12 are connected by a low noise cable 13, and the shield case 11 is grounded.

When the piezoelectric acceleration sensor 7 having such a configuration receives an external force, the inner portion of the composite diaphragm 1 fixed by the fixed frame 10.10 generates a strain proportional to the acceleration of the external force, and this strain causes the piezoelectric Body layer 2 generates an electric charge. In this case, since the diaphragm 6 is formed on the adhesive layer 3 by electroplating, its thickness can be changed arbitrarily while keeping it uniform, so that the composite diaphragm 1 is most susceptible to vibration and distortion. You can select the desired film thickness. Also, the vibrating membrane 6
Since there is no adhesive layer between the piezoelectric layer 2 and the piezoelectric layer 2,
A piezoelectric acceleration sensor whose output angle is stabilized in a low frequency region of Hz or less and whose frequency characteristics change little over time can be obtained.

In this example, a circular hole is provided in the center of a disc-shaped piezoelectric layer to form an annular shape, and an adhesive layer and a diaphragm are laminated on this to form a composite diaphragm. This is used to create a piezoelectric acceleration sensor. However,
The composite diaphragm used in the piezoelectric acceleration sensor of the present invention is not limited to this example, and may be a disc-shaped composite diaphragm without circular holes.

[Experiment example] (Peeling test) Under the manufacturing conditions shown in Table 1, a first metal layer, a second metal layer, and a vibrating membrane were laminated on polyvinylidene fluoride with a thickness of 30 μm to form a composite. A diaphragm was formed and designated as Experimental Examples 1 to Comparative Examples 13.

Note that the vapor deposition conditions for forming the first and second metal layers are a pressure of 1.5×10 −5 T in the vacuum vapor deposition method.

rr, the distance between the sample and the evaporation source was 25 cm, the sputtering method had a pressure of 5 x 10-3 Torr, a deposition rate of 350 Å/s, and the electroplating conditions for forming the vibrating membrane were high concentration sulfamic acid. Using a nickel bath,
Temperature 50°C1 Current density 1 = 2.5 mA/cm2
And so. In Comparative Example 7, the airtightness was broken after forming the first metal layer, the piezoelectric layer on which the first metal layer was formed was left in the air, and then the second metal layer was formed. 8
was formed with a distance of 15 cm between the sample and the evaporation source during vacuum evaporation, and Comparative Example 9 was formed with a pressure of 3 x 10 during evaporation.
-5 Torr, Comparative Example 12 was formed with a deposition rate of 750 Å/s during sputtering, and the other Comparative Examples were manufactured under the same conditions as Experimental Examples 1 to 5.

A surface peeling test was conducted in which a surface adhesive tape was adhered to the surface of the diaphragm of each of the composite diaphragms of Experimental Examples 1 to Comparative Example 13 and then peeled off. The test results are also shown in Table 1. As a result, it was found that all of Experimental Examples 1 to 5, which were formed according to the manufacturing method of the present invention as set forth in claim 2 or 3, were composite diaphragms with good adhesion that hardly caused peeling.

(Frequency characteristic test) Vapor deposition conditions were [pressure], 5XIO-5T on a piezoelectric layer made of polyvinylidene fluoride having a thickness of 30 μm.

rr, the first metal layer made of chromium with a thickness of 500 mm and the second metal layer made of nickel with a thickness of 2500 mm were made airtight using a vacuum evaporation method with a distance of 25 cm between the sample and the evaporation source. Formed continuously without breaking, then heated in a high concentration nickel sulfamate bath at a temperature of 50°C and a current density of I.
A composite diaphragm was manufactured by forming a 30 μm thick diaphragm under conditions of 2.5 mA, and this was designated as Experimental Example 14.

On the other hand, a composite diaphragm was prepared by bonding a 30 μm thick copper foil to a 30 μm thick piezoelectric layer made of polyvinylidene fluoride using evokino resin, and this was designated as Comparative Example 15.

A sine wave with a constant volume of 1000 μbar was applied to Experimental Example 14 and Comparative Example 15 while changing the frequency.

The output at each frequency of Experimental Example I4 and Comparative Example 15 at this time is shown in FIG. Furthermore, the output variations in Experimental Example 14 and Comparative Example 15 are as follows: frequency 200Hz, sound pressure 1000Hz
When a 71 bar sine wave is applied, in Experimental Example 14, the average value of 1.3V for 10 samples is within 105, whereas in Comparative Example I5, the average value of 1.5V for IQ samples is within 105V. Some of them exceeded 100%, making them extremely large.

As a result, the vibrating composite plate of the present invention in which the adhesion layer and the vibrating membrane are formed into a piezoelectric layer is different from the conventional vibrating membrane and piezoelectric layer in which the vibrating membrane and the piezoelectric layer are bonded using an adhesive such as evokino resin. Compared to a diaphragm, the viscoelasticity of the adhesive will not have a negative effect on the diaphragm, so high output can be obtained stably over a wide range, and the characteristics of +-J especially at low frequencies. I found it to be excellent.

(Performance evaluation of piezoelectric acceleration sensor) A disk with a diameter of 7 mm was created from polyvinylidene fluoride with a thickness of 9 μm, and a circular hole with a diameter of 4 mm was formed in the center of this disk to create an annular piezoelectric layer. . This piezoelectric layer was manufactured under the manufacturing conditions shown in Table 2.
A composite diaphragm was formed by laminating the metal layer and the diaphragm, respectively, to form Experimental Example 16 to Comparative Example 22. For adhesive layers other than Comparative Example I8, the vapor deposition conditions were set to a pressure of 1.5
10-5 Torr.

Using a vacuum evaporation method with a distance between the sample and the evaporation source of 25 cm, the first metal layer and the second metal layer were successively formed without breaking airtightness. After forming the layers, the piezoelectric layer on which the first metal layer was formed was left in the air, and then the second metal layer was formed. In addition, the vibrating membrane is
For Experimental Example 16 to Comparative Example 20, high concentration nickel sulfamate bath, temperature 50° C., current density I = 2.
Formed using an electroplating method at 5 mA/cm2,
Comparative Examples 21 and 22 were formed by bonding nickel foil with Evokin resin.

(Hereinafter, blank space) Using each composite diaphragm formed in this way, the fifth
Piezoelectric acceleration sensors as shown in the figure were manufactured and 1.5 G was applied to these piezoelectric acceleration sensors.

Durability was investigated by applying a sine wave of 2001 (z) for 2000 hours and measuring the rate of decrease in output at that time. The results are shown in Table 3 and FIG.

Further, for Experimental Example 16 and Comparative Example 22, the frequency characteristics were investigated by applying sinusoidal vibration of the IG while changing the frequency and measuring the output at each frequency. The results are shown in FIG.

From these results, the piezoelectric acceleration sensor of the present invention can withstand long-term use, provide stable output, and has frequency characteristics that allow high output to be obtained in the low frequency range, where conventional devices could not provide high output. It was found to be of good quality.

(Hereinafter, blank space) [Effects of the Invention] As explained above, the composite diaphragm according to claim 1 of the present invention comprises a first metal layer made of chromium or titanium with a thickness of 100 Å or more and an arbitrary metal layer. An adhesion layer consisting of a second metal layer made of It is possible to improve the adhesion with the material and the durability, and
Since no adhesive is used, a reduction in output and variations in output due to the viscoelasticity of the adhesive layer can be reduced, and a high-performance composite diaphragm can be obtained.

Such a composite diaphragm has a deposition rate of 500 Å/s on one or both sides of the piezoelectric layer as described in claim 2.
The following sputtering method is used to continuously form a first and second metal layer without breaking airtightness to form an adhesive layer, and a vibrating membrane is formed on one of the adhesive layers by electroplating.
Alternatively, as described in claim 3, a vacuum evaporation method is used on one or both sides of the piezoelectric layer with a distance between the piezoelectric layer and the evaporation source of 20 cm or more and 50 cm or less and a pressure of J 2 X 10-5 Toor or less. The first and second metal layers are continuously formed to form an adhesive layer without breaking airtightness, and the vibrating membrane is formed on one of the adhesive layers by electroplating, so there is no oxide layer between each layer. The adhesion between each layer can be improved. Furthermore, since the adhesion layer is formed by vacuum evaporation or sputtering under mild conditions, the piezoelectric layer will not be altered by heat during manufacturing, and the resonant frequency range will be high, allowing complex vibrations to be measured over a wide frequency range. Boards can be manufactured. Furthermore, since the vibrating membrane is formed by electroplating, it is possible to obtain a uniform vibrating membrane with a desired film thickness in a package with few bits, and since it can be formed at room temperature, thermal deformation of the piezoelectric layer can be avoided. It is possible to manufacture an excellent composite diaphragm with no deterioration in piezoelectric properties.

Furthermore, the piezoelectric acceleration sensor according to claim 4 of the present invention includes:
The device has the composite diaphragm according to claim 1, and since acceleration is detected from the amount of electricity generated due to distortion of the composite diaphragm, it has excellent frequency characteristics and piezoelectric characteristics,
It becomes possible to perform highly sensitive measurements over a wide range.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view showing an example of the composite diaphragm according to claim 1 of the present invention, FIG. 2 is a schematic sectional view showing another example of the composite diaphragm according to claim 1, and FIG. is a schematic sectional view showing an example of a detection part of the piezoelectric acceleration sensor according to claim 4, FIG. 4 is a schematic front view thereof, and FIG. 5 is a schematic configuration diagram thereof,
FIG. 6 is a graph showing the frequency characteristics of a composite diaphragm formed by the manufacturing method according to claim 3 of the present invention;
FIG. 7 is a graph showing the durability of the piezoelectric acceleration sensor according to claim 4 of the present invention, and FIG. 8 is a graph showing its frequency characteristics. 1 Composite diaphragm, 2 Piezoelectric layer, 3 Adhesive layer, 4 First metal layer, 5 Second metal layer, 6 Vibration membrane, 7 Piezoelectric acceleration sensor.

Claims (4)

[Claims] (1) An adhesive layer consisting of a first metal layer made of chromium or titanium with a thickness of 100 Å or more and a second metal layer made of an arbitrary metal is placed on one side or on a piezoelectric layer made of a polymer piezoelectric film. Composite diaphragm formed on both sides with a diaphragm formed on one adhesive layer. (2) Deposition rate 50 on one or both sides of the piezoelectric layer
The first and second metal layers are successively formed using a sputtering method of 0 Å/s or less to form an adhesive layer without breaking airtightness, and a vibrating membrane is formed on one of the adhesive layers by electroplating. A method for manufacturing a composite diaphragm according to claim 1, characterized in that: (3) On one or both sides of the piezoelectric layer, the distance between the piezoelectric layer and the evaporation source is set at 20 cm or more and 50 cm or less, and the pressure is 2×1.
Using a vacuum evaporation method at 0^-^5 Torr or less, the first and second metal layers are successively formed without breaking the airtightness to form an adhesive layer, and a vibrating membrane is formed on one of the adhesive layers by electroplating. The method for manufacturing a composite diaphragm according to claim 1, characterized in that: (4) A piezoelectric acceleration sensor having the composite diaphragm according to claim 1