JP3446685B2 - Piezo acoustic components - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric acoustic component such as a piezoelectric buzzer and a piezoelectric receiver.

[0002]

2. Description of the Related Art Conventionally, a piezoelectric acoustic component has been widely used as a piezoelectric buzzer or a piezoelectric receiver which generates an alarm sound or an operation sound in electronic devices, home electric appliances, mobile phones and the like. This type of piezoelectric acoustic component is disclosed in, for example, Japanese Patent Laid-Open No. 7-10.
As described in Japanese Patent No. 7593 and Japanese Patent Application Laid-Open No. 7-203590, a circular metal plate is attached to a single-sided electrode of a circular piezoelectric plate to form a unimorph type vibration plate, and a peripheral portion of the metal plate of the vibration plate is formed. In general, the case is supported in a circular case and the opening of the case is closed with a cover.

[0003]

However, when such a circular diaphragm is used, there is a problem in that the production efficiency is poor, the acoustic conversion efficiency is low, and it is difficult to make it compact. First, the production efficiency will be described. In manufacturing a conventional piezoelectric acoustic component, as shown in FIG.
The circular piezoelectric plate 42 is punched out by
After the circular metal plate 43 is attached to the one-sided electrode, the vibration plate 44 is applied by applying a high-voltage DC electric field between the two-sided electrodes and polarization.
To get The vibrating plate 44 is housed in the case 45, and lead wires 46 and 47 connected to the other surface electrode of the piezoelectric plate 42 and the metal plate 43 are led out of the case 45.

However, as described above, the green sheet 4
When the piezoelectric plate 42 is punched out from 0 in a disk shape, punching scraps increase and the yield of the material is poor. Further, since the individual processing such as electrode formation and polarization starts after punching, the processing efficiency is poor. Further, in order to determine the dimension required for the design by the individual element dimensions, the punching die 41 for the green sheet is used.
Must be made according to the element dimensions. Therefore, there is a drawback that the production efficiency is low as a whole.

Next, the acoustic conversion efficiency will be described.
As shown in FIG. 2 (a), the disc-shaped diaphragm 44 has its peripheral edge fixed by the case 45, and therefore the maximum displacement point P
Is only the center point, the displacement volume is small, and the acoustic conversion efficiency is low. Therefore, there is a drawback that the sound pressure is low relative to the input energy. Further, since the periphery of the diaphragm is constrained, the frequency becomes high, and if a piezoelectric diaphragm having a low frequency is to be obtained, the radius dimension becomes large.

[0006] Therefore, an object of the present invention is to obtain a small-sized piezoelectric acoustic component having high production efficiency, good acoustic conversion efficiency.

[0007]

In order to achieve the above object, the invention according to claim 1 adheres a single-sided electrode of a rectangular piezoelectric plate having electrodes on front and back surfaces to at least one surface of a rectangular metal plate. An insulating cap having an upper wall portion and four side wall portions, and a supporting portion for supporting the diaphragm inside the two side wall portions facing each other;
A plate-shaped substrate on which the electrode part is formed, the vibrating plate is housed in the cap, and two opposing sides of the vibrating plate and the supporting part are fixed with an adhesive or an elastic sealing material.
The gap between the remaining two sides of the diaphragm and the cap is sealed with an elastic sealing material to form an acoustic space between the diaphragm and the upper wall portion of the cap, and the side wall portion of the cap on the substrate. The opening end is bonded, the metal plate is electrically connected to the first electrode portion, and the other surface electrode of the piezoelectric plate is electrically connected to the second electrode portion. A piezoelectric acoustic component characterized by the above.

Since the piezoelectric plate is rectangular, even if the piezoelectric plate is punched from the green sheet, the scraps can be reduced and the material efficiency is good. Moreover, since the work such as electrode formation and polarization can be performed in the state of the parent substrate, the production efficiency is good. further,
Since the dimensions required for design are determined by the parent board cut dimensions,
It is not necessary to make a die for punching a green sheet each time as in the conventional case. In other words, compared to the conventional method, the number of dies, jigs, piezoelectric material types, etc. in the green sheet punching to parent board cutting steps can be reduced, which is advantageous in terms of investment amount and production efficiency.

In the present invention, the two opposite sides of the rectangular diaphragm are fixed to the supporting portion of the cap, and the gap between the remaining two sides and the cap is sealed with the elastic sealing material. When a predetermined frequency signal is input between the metal plate and the other surface electrode of the piezoelectric plate, the piezoelectric plate expands and contracts in a predetermined direction, and accordingly, the diaphragm bends and deforms in the length bending mode. At this time, the diaphragm vibrates vertically with both ends fixed to the cap as nodes, and as shown in FIG. 2B, the maximum displacement point P exists along the center line in the length direction of the diaphragm. To do. That is, the displacement volume becomes larger than that of the conventional disc-shaped diaphragm. This displacement volume serves as energy for moving the air, so that the acoustic conversion efficiency can be increased. The gap between the widthwise ends of the diaphragm and the cap is sealed with a sealing material. However, since the sealing material has elasticity, displacement of the diaphragm is not hindered and sound pressure may be reduced. Absent. Furthermore, the diaphragm is fixed at both ends in its length direction, but the part between them can be freely displaced,
It is possible to obtain a lower frequency than that of a conventional disc-shaped diaphragm. On the contrary, if the same frequency is obtained, the size can be reduced.

In the present invention, the adhesive means one having a high Young's modulus in a cured state and strongly restraining the end portion of the diaphragm. Further, the elastic sealing material refers to a material having a low Young's modulus in a cured state, a weak binding force of the diaphragm, and allowing displacement of the diaphragm. Since some elastic sealing materials have an adhesive force to the diaphragm and the cap, they can be used in place of the adhesive.

FIG. 3 is a comparative diagram showing the relationship between the dimensions of a circular diaphragm and a rectangular diaphragm and the resonance frequency. As is clear from the figure, the rectangular diaphragm can have smaller dimensions (length, diameter) than the circular diaphragm if the frequencies are the same. Conversely, if the dimensions are the same, lower frequencies can be obtained. For comparison, a piezoelectric plate having a thickness of 50
4 μm thick with a thickness of 50 μm as a metal plate using PmT Pm
2Ni was used. The ratio of the length L to the width W of the rectangular diaphragm is 1.67.

In the present invention, the cap to which the vibration plate is fixed is adhered and fixed onto the plate-shaped substrate. Then, by electrically connecting the metal plate to the first electrode portion of the substrate and electrically connecting the other surface electrode of the piezoelectric plate to the second electrode portion of the substrate, the piezoelectric acoustic component is formed. Obtainable. It is also possible to form a surface mount type by drawing the first and second electrode portions provided on the substrate to the back surface of the substrate.

According to a second aspect of the present invention, the piezoelectric plate is adhered to only one surface of the metal plate and at a position deviated to one side of two sides fixed to the supporting portion of the cap, and the piezoelectric plate of the vibrating plate is adhered. It is desirable to provide an exposed portion of the metal plate on the other side of the face and to fix the diaphragm to the support portion of the cap so that the metal plate faces the upper wall portion of the cap. The piezoelectric plate of the vibrating plate may be fixed toward the upper wall portion of the cap, but in this case, since the surface electrode of the piezoelectric plate and the substrate do not face each other, the surface electrode of the piezoelectric plate should be the second electrode of the substrate. It becomes difficult to connect to the electrode part. On the other hand, if the metal plate of the vibration plate is fixed toward the upper wall portion of the cap, the surface electrode of the piezoelectric plate and the substrate face each other, so that the surface electrode and the second electrode portion can be easily connected. Become. Moreover, since the exposed portion of the metal plate is exposed on one side of the vibration plate, the connection between the metal plate and the first electrode portion becomes easy.

According to a third aspect, the exposed portion of the metal plate is first
It is desirable to connect the second electrode portion to the second electrode portion with a conductive adhesive, and to connect the other electrode of the piezoelectric plate with the conductive adhesive. In other words, when the cap is bonded and fixed to the substrate,
It is possible to simultaneously connect the metal plate and the first electrode portion and the other surface electrode of the piezoelectric plate and the second electrode portion,
This is because the connection work becomes easy.

It is preferable that the elastic sealing material is an insulating material and the sealing material is applied to all four sides of the diaphragm. That is, since the metal plate and the other surface electrode of the piezoelectric plate are close to each other, when connecting the other surface electrode of the piezoelectric plate and the second electrode portion using the conductive adhesive, the metal plate and the other surface electrode are connected. Easy to short circuit with the electrode. Therefore, if a sealing material is applied around the metal plate in advance, this short circuit can be prevented. Further, by sealing all four sides of the diaphragm with the elastic sealing material, air leakage is eliminated and the sound pressure characteristic is improved. When applying the elastic sealing material to all four sides of the diaphragm, a method of attaching the diaphragm to the cap only with the elastic sealing material without using an adhesive and a diaphragm fixed with the adhesive There is a method in which the elastic sealing material is overlapped and applied on the two sides. The latter method is effective when air leakage cannot be completely prevented by the adhesive alone.

[0016]

4 to 7 show a piezoelectric buzzer which is a first embodiment of a piezoelectric acoustic component according to the present invention. The piezoelectric buzzer is generally composed of a unimorph type diaphragm 1, a cap 4 and a substrate 10.

As shown in FIG. 7, the vibrating plate 1 has thin-film or thick-film electrodes 2a and 2b on the front and back surfaces, and has a rectangular piezoelectric plate 2 polarized in the thickness direction. The piezoelectric plate 2 is formed into a rectangular shape having the same size and a slightly long length.
And a metal plate 3 that is face-bonded to the back electrode 2b via a conductive adhesive or the like. The back electrode 2b
Alternatively, the back surface electrode 2b may be omitted by directly bonding the metal plate 3 to the back surface of the piezoelectric plate 2 via a conductive adhesive or the like. In this embodiment, the piezoelectric plate 2 is bonded to the metal plate 3 at a position deviated to one side in the length direction,
On the other side of the metal plate 3 in the length direction, there is an exposed portion 3a where the metal plate 3 is exposed.

As the piezoelectric plate 2, a piezoelectric ceramic such as PZT is used. Further, the metal plate 3 is preferably a material having both good conductivity and spring elasticity, and particularly a material having a Young's modulus close to that of the piezoelectric plate 2. Therefore, for example, phosphor bronze or 42Ni is used. When the metal plate 3 is 42Ni, the coefficient of thermal expansion is close to that of ceramic (PZT or the like), so that a more reliable one can be obtained.

The diaphragm 1 can be manufactured by the following steps. First, a rectangular parent substrate is punched out from a ceramic green sheet by a punching die, and after forming electrodes, polarization, etc. on the parent substrate,
The parent board is bonded to the mother board of the metal plate with a conductive adhesive or the like.
Then, the bonded parent substrate and mother metal plate can be cut into a rectangular shape by vertical and horizontal cut lines using a dicer or the like to obtain a diaphragm. In this way, the rectangular metal plate 3
The use of the rectangular piezoelectric plate 2 has advantages that material efficiency and production efficiency are good and equipment cost can be reduced.

The diaphragm 1 has a cap 4 which is turned upside down.
It is housed inside and is fixed at both ends in its length direction. That is, the cap 4 is formed of an insulating material such as ceramics or resin in a box shape having an upper wall portion 4a and four side wall portions 4b, and both end portions of the diaphragm 1 are provided inside two opposing side wall portions 4b. The supporting portion 4c for supporting is integrally formed. The smaller the support section 4c is, the better the sound pressure and the smaller the resonance frequency. Cap 4
When the resin is composed of LCP (liquid crystal polymer),
SPS (Syndiotactic Polystyrene), PPS
Heat resistant resins such as (polyphenylene sulfide) and epoxy are desirable. A sound output hole 4d is formed in the center of the upper wall 4a, a notch 4e is formed in the opening edge of two opposing side walls 4b, and an opening edge of the remaining one side wall 4b is formed. The braking hole 4f is formed.

The diaphragm 1 is housed inside the cap 4 so that the metal plate 3 faces the upper wall portion 4a.
The two short sides are placed on the support portion 4c and fixed with an adhesive 5 (see FIG. 5). As the adhesive 5, a known insulating adhesive such as an epoxy type, a urethane type, or a silicone type may be used. With the two short sides of the diaphragm 1 fixed to the support portion 4c of the cap 4, the two long sides of the diaphragm 1 have a slight gap between them and the inner surface of the cap 4, This gap is sealed with an elastic sealing material 6 such as silicone rubber. Thereby, the acoustic space 7 is formed between the diaphragm 1 and the upper wall portion 4a of the cap 4.

After the diaphragm 1 is fixed to the cap 4 as described above, the cap 4 is adhered to the substrate 10. Board 10
Is a rectangular flat plate made of an insulating material such as ceramics or resin. When it is made of resin, LCP, SP
A heat resistant resin such as S, PPS, epoxy (including glass epoxy) is used. Electrode portions 13 and 14 for external connection, which extend from the front surface to the back surface through the through hole grooves 11 and 12, are formed at both ends of the substrate 10 in the longitudinal direction. Conductive pastes 15 and 16 are applied on the two notched portions 4e of the cap 4 facing each other, that is, the exposed portions 3a of the metal plate 3 located at both ends of the vibration plate 1 and the surface electrodes 2a of the piezoelectric plate 2 to form the cap 4 The opening edge of the cap 4 is adhered onto the substrate 10 in a state where the insulating adhesive 19 (see FIG. 6) is applied by transfer or the like to the opening edge of or the cap bonding portion of the substrate 10. At this time, the exposed portion 3a of the metal plate 3 and the electrode portion 13 of the substrate 10 are connected by the conductive paste 15.
The surface electrode 2 a of the piezoelectric plate 2 and the electrode portion 14 of the substrate 10 are connected by the conductive paste 16. In this state, the conductive pastes 15 and 16 and the insulating adhesive 19 are heat-cured or naturally-cured to complete the surface-mounted piezoelectric acoustic component.

Electrode portions 13 and 1 provided on the substrate 10
Predetermined frequency signal between 4 (AC signal or square wave signal)
If both ends of the diaphragm 1 in the length direction are
Since both ends in the width direction of the vibration plate 1 are fixed to the supporting portion 4c of the vibration plate 1 by elastic sealing members 6 so as to be elastically displaceable, the vibration plate 1 operates in the length bending mode with the both ends in the length direction as fulcrums. It can vibrate and generate a predetermined buzzer sound. The buzzer sound is emitted to the outside from the sound emission hole 4d of the cap 4.

In the above embodiment, the metal plate 3 of the diaphragm 1 is fixed toward the upper wall portion 4a of the cap 4. The reason is that since the surface electrode 2a of the piezoelectric plate 2 and the exposed portion 3a of the metal plate 3 face the substrate 10, connection between the surface electrode 2a and the electrode portion 14 and connection between the exposed portion 3a and the electrode portion 13 are performed. This is because the connection can be easily made using the conductive pastes 15 and 16.

Further, in the above embodiment, the two short sides of the diaphragm 1 are fixed with the adhesive 5 and the two long sides of the diaphragm 1 are sealed with the elastic sealing material 6. The stopping material 6 may be applied on the two sides of the diaphragm 1 fixed by the adhesive 5 on the shorter side. The first reason is that the surface electrode 2a of the piezoelectric plate 2 is attached to the electrode portion 14 of the substrate 10 by the conductive adhesive 16, as described later.
When connecting by 18, the conductive adhesive 16 may adhere to the metal plate 3 to cause a short circuit. Therefore, an insulating film is formed on the peripheral edge of the metal plate 3 by the elastic sealing material 6, This is to prevent a short circuit. The second reason is that by sealing the entire circumference of the diaphragm 1 with the elastic sealing material 6, it is possible to more reliably prevent air leakage between the front side and the back side of the diaphragm 1.

8 to 10 show a second embodiment of the present invention. Here, the cap 1 is loaded with the diaphragm 1, and the four sides of the diaphragm 1 are sealed with the elastic sealing material 6 and adhered. In this case, since both ends in the length direction of the diaphragm 1 are bonded to the support portion 4c by the elastic sealing material 6 instead of the adhesive 5, the length direction of the diaphragm 1 is longer than that in the first embodiment. The restraint force at both ends is reduced, and the displacement of the diaphragm 1 can be increased,
Sound pressure can be increased.

In this case, the conductive pastes 15 and 16 are applied to both ends of the vibration plate 1 in the length direction, and
By applying similar conductive pastes 17 and 18 on the electrode portions 13 and 14 of the substrate 10 facing the diaphragm 10, when the cap 4 is adhered to the substrate 10, the diaphragm 1 and the electrode portion 13 of the substrate 10 are adhered. , 14 can be more reliably electrically connected. Further, it is not necessary to fix the cap 4 to the substrate 10 before the conductive pastes 15 and 16 are cured,
After the conductive pastes 15 and 16 are applied to the diaphragm 1 and cured, the cap 4 can be bonded to the substrate 10.

FIG. 11 shows an example in which the piezoelectric acoustic component according to the third embodiment of the present invention is of a lead type. In this embodiment, the substrate 10 is extended in the longitudinal direction and the extension 10
Two electrode parts 1 exposed to the outside from the cap bonding part on a
3 and 14 are extended and these electrode portions 13 and 14 are
The lead terminals 20 and 21 are connected to each other by soldering or the like. In this case, the diaphragm 1 and the cap 4 are exactly the same as those in FIGS. 4 to 10,
By changing the shapes of the substrate 10 and the electrode parts 13 and 14,
A lead type piezoelectric acoustic component can be easily constructed. Further, since the mounting by reflow soldering is not performed, a material having low heat resistance may be used for the cap 4 and the substrate 10.

In the first to third embodiments, one substrate 1
Although a cap 4 having one diaphragm 1 fixed thereon was bonded to 0, a plurality of spaces were formed in the cap 4 by a partition wall or the like, and a plurality of diaphragms 1 having different frequencies were fixed in these spaces. Alternatively, this may be bonded to one substrate 10. In this case, if individual electrode portions are formed on the substrate 10 corresponding to each diaphragm 1 and these electrode portions and each diaphragm 1 are individually connected, a plurality of different sounds are generated from each diaphragm 1. You can also

The metal plate and the piezoelectric plate are not limited to rectangular shapes, but may be square shapes. Further, in the above embodiment,
Although the unimorph type diaphragm in which the piezoelectric plate is attached to one surface of the metal plate has been described, a bimorph type diaphragm in which the piezoelectric plates are attached to both surfaces of the metal plate may be used. Further, although the conductive adhesive (conductive paste) is used for connecting the metal plate and the first electrode portion and connecting the other surface electrode of the piezoelectric plate and the second electrode portion, other means (solder or It is also possible to connect using a conductive wire or the like). The present invention can be applied to a piezoelectric receiver, a piezoelectric speaker, a piezoelectric sounder, a ringer, etc. in addition to the piezoelectric buzzer.

[0031]

As is apparent from the above description, claim 1
According to the invention described in (1), since the rectangular diaphragm is used,
Since it is possible to reduce the number of molds, jigs, and piezoelectric material types in the processes from punching of the green sheet to cutting of the parent board, and the material efficiency is high, the production efficiency can be improved and the manufacturing cost can be reduced. Further, since the two opposite sides of the rectangular diaphragm are fixed to the support portion of the cap and the gap between the other two sides of the diaphragm and the cap is sealed, the maximum displacement point is in the length direction of the diaphragm. It exists along the center line and can increase the displacement volume. Therefore, the acoustic conversion efficiency can be increased as compared with the disk-shaped diaphragm. The rectangular diaphragm has its two sides fixed, but the portion between them can be freely displaced, so that a lower frequency can be obtained as compared with the conventional disk-shaped diaphragm. On the contrary, if the same frequency is obtained, the size can be reduced.

According to the second aspect of the present invention, the piezoelectric plate is adhered to only one surface of the metal plate and at a position deviated to one side of the two sides fixed to the support portion of the cap, and the piezoelectric plate of the vibration plate is bonded. Since the exposed part of the metal plate is provided on the other side of the surface to which the plate is bonded, and the vibration plate is fixed to the support part of the cap so that the metal plate faces the upper wall side of the cap, the surface electrode of the piezoelectric plate And the substrate face each other, which facilitates connection between the surface electrode and the second electrode portion. Moreover, since the exposed portion of the metal plate is exposed on one side of the vibration plate, there is an effect that the connection between the metal plate and the first electrode portion becomes easy.

[Brief description of drawings]

FIG. 1 is a diagram showing a manufacturing process of a conventional piezoelectric buzzer.

FIG. 2 is a comparison diagram of displacement distributions of a circular diaphragm and a rectangular diaphragm.

FIG. 3 is a diagram showing a relationship between dimensions of a circular diaphragm and a rectangular diaphragm and a resonance frequency.

FIG. 4 is a perspective view of a piezoelectric buzzer that is a first embodiment of a piezoelectric acoustic component according to the present invention.

5 is a sectional view taken along line XX of FIG.

6 is a cross-sectional view taken along line YY of FIG.

FIG. 7 is a perspective view of a diaphragm.

FIG. 8 is an exploded perspective view of a cap and a diaphragm of a piezoelectric buzzer, which is a second embodiment of the piezoelectric acoustic component according to the present invention, as viewed from the back surface side.

9 is a perspective view of a state where the cap and the diaphragm of the piezoelectric buzzer of FIG. 8 are viewed from the back surface side, and is an assembled state.

10 is an exploded perspective view of a cap and a substrate of the piezoelectric buzzer of FIG.

FIG. 11 is a perspective view of a piezoelectric buzzer which is a third embodiment of the piezoelectric acoustic component according to the present invention.

[Explanation of symbols]

1 diaphragm 2 Piezoelectric plate 2a Surface electrode 3 metal plates 4 cap 4a Upper wall part 4b side wall 4c support 5 adhesive 6 Elastic sealing material 10 substrates 13 First electrode part 14 Second electrode part 15-18 Conductive paste (conductive adhesive)

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ identification code FI G10K 9/12 101G (58) Fields investigated (Int.Cl. ⁷ , DB name) G10K 9/122 H03H 9/10 H04R 17 / 00

Claims (4)

(57) [Claims] 1. A vibrating plate formed by adhering a single-sided electrode of a rectangular piezoelectric plate having electrodes on the front and back surfaces to at least one surface of a rectangular metal plate, an upper wall portion and four side wall portions. An insulating cap having a supporting portion for supporting the diaphragm inside two side wall portions facing each other; and a flat plate-shaped substrate on which first and second electrode portions are formed. The diaphragm is housed, the two opposite sides of the diaphragm and the supporting portion are fixed with an adhesive or an elastic sealing material, and the remaining two parts of the diaphragm
The gap between the side and the cap is sealed with an elastic sealing material, an acoustic space is formed between the diaphragm and the upper wall of the cap, and the side wall opening end of the cap is bonded onto the substrate. At the same time, the metal plate is electrically connected to the first electrode portion, and the other surface electrode of the piezoelectric plate is electrically connected to the second electrode portion. Acoustic parts. 2. The piezoelectric plate is adhered to only one surface of a metal plate and at a position biased to one side of two sides fixed to a supporting portion of a cap, and the surface of the vibrating plate to which the piezoelectric plate is adhered is bonded. The exposed part of the metal plate is provided on the other side, and the diaphragm is fixed to the support part of the cap with the metal plate facing the upper wall part of the cap. Piezo acoustic components. 3. The metal plate is connected to a first electrode portion by a conductive adhesive, and the other surface electrode of the piezoelectric plate is connected to a second electrode portion by a conductive adhesive. The piezoelectric acoustic component according to claim 1 or 2. 4. The elastic sealing material is formed of an insulating material,
The piezoelectric acoustic component according to any one of claims 1 to 3, wherein the piezoelectric acoustic component is applied to all four sides of the diaphragm.