JP5043311B2 - Piezoelectric laminate and manufacturing method thereof, piezoelectric speaker, electronic device - Google Patents

Description

  The present invention relates to a piezoelectric laminated body in which piezoelectric bodies are laminated, a manufacturing method thereof, a piezoelectric speaker, and an electronic device, and more specifically, improvement of stress in the laminated body, prevention of fusion during firing, adhesion of external electrodes. It is about improvement.

  A speaker using a piezoelectric body is widely used as a simple electroacoustic conversion means, and in particular, in recent years, it has been widely used in the fields of cellular phones and portable information terminals. For example, Patent Document 1 below discloses a piezoelectric speaker that uses a piezoelectric laminate as a drive source.

  This piezoelectric laminate has a structure in which a plurality of piezoelectric sheets and electrodes are alternately laminated. As the piezoelectric sheet, for example, lead zirconate titanate (PZT) -based piezoelectric ceramics having a perovskite crystal structure is used. As the electrode, Pt, Pd, Ag / Pd, or the like is used. These piezoelectric ceramics and electrode materials are alternately laminated and fired at the same time to produce a piezoelectric laminate. The number of stacked layers is suitably 3 to 5 layers from the viewpoint of the displacement amount, rigidity, cost, handling, etc. of the piezoelectric laminate.

  FIG. 5 shows a laminated example of five layers. The state of the piezoelectric sheet and the electrode pattern is shown in FIG. 4A, and the electrode portion of FIG. 1A is extracted and shown in FIG. If it demonstrates from the lowest layer, the electrode 902 is formed in the back surface of the piezoelectric sheet 900, and the electrode 904 is formed in the surface. The electrode 904 is formed with lands or openings (exposed portions of the piezoelectric sheet) 906 for hole connection. A connection hole 908 is formed in the piezoelectric sheet 900 in the opening 906. An electrode 912 is formed on the surface of the next piezoelectric sheet 910, and an opening 914 for hole connection is formed in the electrode 912. A connection hole 916 is formed in the piezoelectric sheet 910 in the opening 914. Note that no electrode is formed on the back side of the piezoelectric sheet 910.

  Similarly, an electrode 922 and an opening 924 are formed on the surface of the next piezoelectric sheet 920, but no electrode is formed on the back surface. A connection hole 926 is formed in the piezoelectric sheet 920 in the opening 924. An electrode 932 and an opening 934 are formed on the surface of the next piezoelectric sheet 930, but no electrode is formed on the back surface. A connection hole 936 is formed in the piezoelectric sheet 930 in the opening 934. An electrode 942 is formed on the surface of the next piezoelectric sheet 940, but no electrode is formed on the back surface.

  In addition, in the piezoelectric sheets 910, 920, 930, and 940, connection holes are formed on the back side corresponding to the connection holes 908, 914, 924, and 934 of the piezoelectric sheet laminated on the lower side (not shown). )

When the piezoelectric sheets 900 to 940 on which the electrode patterns are formed as described above are stacked, the result is as shown in FIG. That is, the electrodes 902, 912, and 932 are connected by the connection hole 950, and the electrodes 904, 922, and 942 are connected by the connection hole 952. Conventionally, the piezoelectric sheets 900, 910,..., 940 and the electrodes 902, 904, 912,.
JP 2003-47092 A

Conventionally, when firing a ceramic thin plate (piezoelectric sheet or laminated body thereof), a plurality of these are fired in order to prevent bending and warping of the thin plate. At this time, in order to prevent fusion of the laminated ceramic thin plates, peeling powder (spraying powder) is used. The release powder is used by adhering to the surfaces to be overlapped or by interposing them in the form of a sheet between the surfaces to be overlapped. In general, zirconia powder is often used as the release powder. In addition, as a method for preventing fusion, for example, there is a method of firing with a thin plate interposed. For example, zirconia or stabilized zirconia is used as the plate. In order to reduce the fusion between the plate and the thin plate, the plate may be blasted. Furthermore, as shown in Patent Document 2 below, there is a method in which coarse particles are mixed in a raw ceramic thin plate or zirconia coarse particles are mixed.
Japanese Patent Publication No. 3-2821

  First, in the technique described in Patent Document 1, piezoelectric sheets 900, 910,..., 940 and electrodes 902, 904, 912,. Baking at the same time. However, since the thermal expansion coefficients of the piezoelectric material and the electrode material are different, residual stress due to the thermal expansion difference is generated in the cooling process after densification, that is, after the holding at the maximum temperature is finished. . Commonly used electrode materials for simultaneous firing (Pt, Pd, Ag / Pd, etc.) have a larger thermal expansion coefficient than PZT ceramics which are piezoelectric materials. For this reason, compressive stress acts on the ceramic part after cooling in the surface direction. When such residual compressive stress is present, the crystal lattice of PZT ceramics is distorted, and the piezoelectric characteristics may be deteriorated as compared with the unstressed state.

  On the other hand, regarding the firing of the laminated body, it is a lead-based material in which peeling powder is applied to prevent fusion, or when it is made into a sheet and interposed on the overlapping surface, fusion occurs when the peeling powder is small. This causes inconveniences such as affecting the sinterability of the ceramic itself and ineffective if the amount is too small. A size of about 10 μm or more is required, but if it is too large, it becomes a base point for deformation. In addition, the release powder remains after firing, and it is difficult to remove all by washing. In addition, in the process of printing the electrode after firing, there is a risk of adversely affecting the characteristics and reliability.

  In addition, in the method using a plate, first, a thin plate must be prepared, which is expensive. Although the plate is initially not problematic, as the frequency of use increases, lead diffuses when used for lead-based materials. Since lead diffuses along the grain boundary, it causes warping of the plate itself, and as a result, warpage of the ceramic increases. Furthermore, the zirconia lump falls off from the plate and remains as a foreign substance. Therefore, in any method using release powder or a plate, it is difficult to prevent the ceramic thin plate from being fused and to sufficiently suppress warpage and bending.

  Furthermore, as described in Patent Document 2, the method of mixing coarse particles partially causes a difference in activity and makes the sinterability non-uniform. I can't say that. In the case of this method, there is also a possibility that the reliability of the product may be affected by the problem of sinterability unless measures such as changing the sheet for each layer are taken for the lamination type.

  The present invention focuses on the above points, and an object of the present invention is to reduce the residual stress of the piezoelectric laminate and suppress the deterioration of the piezoelectric characteristics. Another object is to prevent fusion during firing of the laminate and to improve the adhesion of the external electrodes.

In order to achieve the above object, the present invention is directed to laminating an internal electrode and an external electrode with a piezoelectric sheet interposed therebetween, and arranging the piezoelectric sheet in a laminating direction so that the laminated internal electrodes are alternately connected to different external electrodes. When manufacturing a piezoelectric laminate having a connection hole penetrating therethrough, a first piezoelectric sheet in which the internal electrode and the connection hole are formed, and a second connection hole in which only the connection hole for connecting to the external electrode is formed A piezoelectric sheet is obtained, and a plurality of the first piezoelectric sheets are laminated, and the second piezoelectric sheet is further laminated on the first piezoelectric sheet from which the internal electrode is exposed after lamination to form a laminated body and crimped. Then, the laminated body after the compression bonding obtained in the step is fired, and the outer side of the fired laminated body is exposed using a low-temperature process so as to be electrically connected to the connection hole. To form the electrode, the time to pressure bonding, by crimping across the laminate rough surface of the sheet having a predetermined surface roughness, the surface on which the external electrodes of the laminate is formed, predetermined surface Roughness is formed . The above and other objects, features and advantages of the present invention will become apparent from the following detailed description and the accompanying drawings.

According to the present invention, since the external electrode of the piezoelectric laminate is formed by a low-temperature process after firing the laminate in which the first and second piezoelectric sheets and the internal electrodes are laminated, the residual stress of the piezoelectric laminate is reduced. Deterioration of piezoelectric characteristics can be suppressed. Further, when the laminated body in which the first and second piezoelectric sheets and the internal electrodes are laminated, the laminated body is crimped by sandwiching the laminated body with a rough surface of a sheet having a predetermined surface roughness, so that the laminated body Since a predetermined surface roughness is formed on the surface on which the external electrode is formed, it is possible to prevent fusion during firing of the laminate and improve the adhesion of the external electrode.

  Hereinafter, the best mode for carrying out the present invention will be described in detail based on examples.

  First, Embodiment 1 of the present invention will be described with reference to FIG. In this embodiment, three piezoelectric sheets are laminated. FIG. 1A shows a state of the piezoelectric sheet and the electrode pattern, and a plan view of the piezoelectric sheet 110 is shown in FIG. FIG. 1B shows an electrode portion extracted from FIG. In these drawings, an internal electrode 102 is formed on the surface of the lowermost piezoelectric sheet 100. An opening 104 for hole connection is formed in the internal electrode 102. In addition, a connection hole 106 for connecting to the back side of the piezoelectric sheet 100 is formed in the opening 104. Note that no electrode pattern is formed on the back surface of the piezoelectric sheet 100.

  Next, internal electrodes 112 are formed on the surface of the piezoelectric sheet 110. An opening 114 for hole connection is formed in the internal electrode 112. In addition, a connection hole 116 for connecting to the back surface side of the piezoelectric sheet 110 is formed in the opening 114. Further, a connection hole 118 for connecting to the connection hole 106 of the piezoelectric sheet 100 is formed. Next, the uppermost piezoelectric sheet 120 has no electrode pattern on either the front or back, but a connection hole 122 for connecting to the connection hole 116 of the lower piezoelectric sheet 110 is formed.

As the piezoelectric sheets 100, 110, 120, PZT ceramics are used. Specifically, for (1) PbTiO ₂ —PbZrO _{2 having} a phase boundary composition, or (2) for the above (1), in order to change the Curie point according to the operating temperature range and to improve other characteristics, A material added with a small amount of an additive such as Mn or Zn is used. Then, the PZT ceramic powder pulverized to a particle size of 1 μm or less is dispersed in water or an organic solvent, and an appropriate binder is added to form a slurry. Next, the slurry is formed into a sheet by a known method such as a doctor blade method.

  As the internal electrodes 102 and 112, a metal that does not melt at the sintering temperature of the PZT ceramics or does not react with oxidation or lead is used. Specifically, platinum and silver / palladium alloy are suitable. First, the metal for the internal electrodes 102 and 112 is applied to the dried PZT-based ceramic piezoelectric sheets 100, 110 and 120. As a coating method, a known method such as a screen printing method using a paste can be used. Further, in order to connect the electrodes in the vertical direction, holes are made in the piezoelectric sheets 100, 110, 120, and the inside is filled with metal to form connection holes 106, 116. At this time, the openings 104 and 114 are formed in the electrode pattern so that the electrodes can be alternately connected in the stacking direction. In addition, the external electrodes are not initially printed, but filling printing of the connection holes 122 is also performed on the outermost piezoelectric sheet 120 so that the external electrodes and the connection holes 116 can be connected later.

  As described above, the piezoelectric sheets 100, 110, 120 that have been printed on only the internal electrodes 102, 112 are laminated and integrated by thermocompression bonding or the like. At the time of this thermocompression bonding, thermocompression bonding is performed with a laminated piezoelectric sheet sandwiched between sheets having a predetermined surface roughness. This sheet can be used as long as it is a sheet having a rough surface, such as a PET film whose surface is sandblasted or the like, paper, or non-woven fabric. And this laminated body is cut out to a desired shape (FIG. 1 shows the state after cutting out), and it is set as a molded object. Next, the compact is fired and sintered at the sintering temperature of the PZT ceramic. In the case of standard PZT ceramics, this temperature is about 900 to 1200 ° C. After firing, the main cross section is shown in FIG. That is, the internal electrode 112 is drawn to the lower surface side of the drawing by the connection holes 130 (106 and 118) that penetrate the opening 104 of the internal electrode 102, and the internal electrode 102 is connected to the connection hole 132 that penetrates the opening 114 of the internal electrode 112. By (116 and 122), it is pulled out to the upper surface side of the figure.

  After the firing and cooling are finished, in this embodiment, external electrodes 140 and 142 are formed on the front and back surfaces of the obtained sintered body of FIG. 1D, as shown in FIG. At this time, the external electrodes 140 and 142 are connected to the connection holes 130 and 132 so as to cover the lead portions of the connection holes 130 and 132 on the front and back surfaces. As a method for forming the external electrode, a known method is used as long as the temperature of the main surface of the laminated body does not exceed 200 ° C. at which a substantial stress may occur, such as a sputtering method or a plating method. be able to. As the electrode material, gold, silver, nickel, aluminum, or the like can be used as long as it is a sputtering method. Moreover, if it is a plating method, electroless nickel plating etc. can be used.

  By using such a low-temperature process, the residual stress generated in the PZT-based ceramics can be greatly reduced as compared with the case where the external electrode is fired simultaneously with the internal electrode. In addition, the deterioration of the piezoelectric characteristics can be suppressed to a small level. That is, the magnitude of the thermal stress generated in the cooling process after firing or sintering depends on the volume ratio between the PZT ceramic and the electrode. That is, by not firing the internal electrodes 102 and 112 and the external electrodes 140 and 142 at the same time, the number of electrode layers is halved in the case of three piezoelectric sheets, and the number of electrode layers is two in the case of five piezoelectric sheets described later. / 3 and less. For this reason, the residual compressive stress which generate | occur | produces in a piezoelectric sheet can be made small so much. If the residual stress is reduced, the distortion of the lattice is also reduced, and a characteristic closer to a no-stress state can be obtained.

  As described above, the external electrodes 140 and 142 are formed by a low-temperature process after the laminated body is sintered, so that the residual compressive stress of the piezoelectric sheets 100, 110, and 120 can be reduced, and the accompanying deterioration of piezoelectric characteristics can be suppressed. it can. Therefore, if a piezoelectric speaker is configured using the piezoelectric laminate manufactured as described above, the sound pressure can be increased as compared with the case where the external electrodes 140 and 142 are simultaneously fired. This effect is particularly significant when the piezoelectric sheets 100, 110, and 120 are thin, and a thin piezoelectric element that improves the electric field strength and increases the sound pressure by thinning the layer is obtained. The effect is great. In addition, good results appear when the aspect ratio, that is, the ratio of the diameter of the electrode to the distance between the electrodes is 100 or more, and particularly when the ratio is 500 or more, a more remarkable effect can be obtained. Further, if the surface roughness Ra of the external electrode forming surface of the laminated body after firing is 0.40 to 0.75 μm, the adhesion of the external electrodes 140 and 142 can be further improved, and a plurality of during the sintering. Even if these laminates are superposed, fusion can be prevented.

  Next, Embodiment 2 of the present invention will be described with reference to FIG. Although the embodiment described above is an example in which three layers of piezoelectric sheets are laminated, this embodiment is an example in which five layers of piezoelectric sheets are laminated. FIG. 2 (A) shows the state of the piezoelectric sheet and the electrode pattern, and FIG. 2 (B) shows the electrode portion extracted from FIG. 2 (A). In these drawings, an electrode 202 is formed on the surface of the lowermost piezoelectric sheet 200. The electrode 202 has an opening 204 for hole connection. In addition, a connection hole 206 for connecting to the back side of the piezoelectric sheet 200 is formed in the opening 204. Note that no electrode pattern is formed on the back surface of the piezoelectric sheet 200.

  Next, an electrode 212 is formed on the surface of the piezoelectric sheet 210. The electrode 212 has an opening 214 for hole connection. In addition, a connection hole 216 for connecting to the back side of the piezoelectric sheet 210 is formed in the opening 214. Further, a connection hole 218 for connecting to the connection hole 206 of the piezoelectric sheet 200 is formed. The same applies to the piezoelectric sheets 220 and 230 as illustrated.

  Next, the uppermost piezoelectric sheet 240 has no electrode pattern on either the front or back, but a connection hole 242 for connecting to the connection hole 236 of the lower piezoelectric sheet 230 is formed. The materials of the piezoelectric sheets 200, 210, ..., 240 and the electrodes 202, 212, ..., 232 are the same as those in the first embodiment.

  As described above, the piezoelectric sheets 200, 210,..., 240 that have been printed on only the internal electrodes are stacked, and fired and sintered in the same manner as in the first embodiment. After firing, the main cross section is shown in FIG. That is, the electrodes 212 and 232 are drawn to the lower surface side of the drawing by the connection holes 250 (206, 218, 226, and 238) that penetrate the openings 204 and 224, and the electrodes 202 and 222 are connected to the openings 214 and 234. The hole 252 (214, 228, 234, 242) is drawn to the upper surface side of the figure. After the completion of firing and cooling, external electrodes 260 and 262 are formed on the front and back surfaces of the obtained sintered body of FIG. 2C by a low temperature process, as shown in FIG. Also in the present embodiment, as in the first embodiment, the residual compressive stress is reduced to 2/3 and the piezoelectric characteristics are improved as compared with the case where the external electrode and the internal electrode are fired simultaneously.

  Next, Embodiment 3 of the present invention will be described with reference to FIG. In this embodiment, the electrodes are divided into two and are connected alternately. FIG. 3A shows the state of the piezoelectric sheet and the electrode pattern. The solid line in FIG. 3B shows the electrode portion taken out from FIG. 3A. In these drawings, divided electrodes 302 and 306 are formed on the surface of the lowermost piezoelectric sheet 300, and connection lands 304 and 308 are formed, respectively. An electrode pattern is not formed on the back surface of the piezoelectric sheet 300. Split electrodes 312 and 316 are formed on the surface of the next piezoelectric sheet 310, and connection lands 314 and 318 are formed, respectively. An electrode pattern is not formed on the back surface of the piezoelectric sheet 310.

  Next, the uppermost piezoelectric sheet 320 has no electrode pattern on either the front or back, but connection holes 322 and 324 for connecting to the connection lands 314 and 318 of the lower piezoelectric sheet 310 are formed. . The materials of the piezoelectric sheets 300, 310, 320 and the electrodes 302, 306,..., 316 are the same as those in the first embodiment.

  As described above, the piezoelectric sheets 300, 310, and 320 that have been printed on only the internal electrodes are stacked, and fired and sintered in the same manner as in the first embodiment. After firing, as shown by the chain line in FIG. 3B, external divided electrodes 500, 504, 510, and 514 are formed by a low-temperature process. Accordingly, the divided electrodes 504, 302, 316, and 510 are connected through the connection hole 600, and the divided electrodes 500, 306, 312, and 514 are connected through the connection hole 602. By such connection, it becomes possible to apply a voltage so that the upper and lower sides have different polarities. Also according to the present embodiment, the same effect as the above-described embodiment can be obtained.

Next, experimental examples performed in connection with the present invention will be described. First, according to Experimental Examples 1 to 8 and Comparative Examples 1 to 8, the external electrode is formed after firing the laminate and the external electrode and the internal electrode are simultaneously laminated and fired, and the experimental example From 9 to 12, investigations were made on nickel sputtering material for forming the external electrode.
(1) Experimental Example 1 PZT (Pb (Zr _0.5 Ti _0.5 ) O ₂ ) was used as a material, and this was dispersed in a mixed solvent of toluene and ethanol, and a polyvinyl butyrate binder Was added to form a sheet. The thickness of this piezoelectric sheet was 20 μm. On the dried piezoelectric sheet, it printed with the Pt paste so that it might become 18 mm in diameter and 2 micrometers in thickness. The print pattern is as shown in FIG. As shown in FIG. 1A, two printed piezoelectric sheets and one unprinted piezoelectric sheet were provided with connection holes, and the same electrode paste was filled and printed. After printing, lamination and thermocompression bonding were performed, and a molded body was punched out with a φ19 mold. This molded body was fired in air at 1200 ° C. to obtain a laminated piezoelectric body shown in FIG. Next, an external electrode having a thickness of 50 nm was formed on the surface of the laminated piezoelectric material by silver sputtering as shown in FIG. Subsequently, the deviation of the diffraction peak of PZT was accurately measured with an X-ray diffractometer, and the residual stress was calculated therefrom. Further, the piezoelectric laminate was attached to an aluminum frame with a silicon adhesive, and the displacement when a DC voltage of 1 V was applied was measured with a laser interferometer.

  (2) Experimental Examples 2 to 12: Using the method according to Experimental Example 1, the material of the piezoelectric sheet is PZT-PMN low-temperature sintered material, the electrode material is Ag / Pd, and the firing temperature is 900. ℃ (Experimental Examples 2, 4, 6, 8, 10, 12), Piezoelectric sheet thickness of 15 μm (Experimental Examples 3, 4, 7, 8, 11, 12), Number of piezoelectric sheets stacked The same measurement was carried out for each of the five layers (Experimental Examples 5, 6, 7, and 8) and the sputtering material for forming the external electrode made of nickel (Experimental Examples 9, 10, 11, and 12). .

On the other hand, corresponding to Experimental Examples 1 to 8 described above, the external electrodes were also formed by printing with the same paste as that of the internal electrodes before sintering, and were fired simultaneously as Comparative Examples 1 to 8. Table 1 below summarizes the conditions and measurement results of these experimental examples and comparative examples.

  As is clear from comparison of the residual stresses of the experimental examples 1 to 8 in which the external electrodes are formed after the lamination firing and the comparative examples 1 to 8 in which the external electrodes and the internal electrodes are laminated and fired at the same time, the comparative example is more residual. The stress value is 1.5 to 2 times that of the experimental example. Also, the dielectric constant related to the piezoelectric characteristics is smaller in the comparative example having a large residual stress than in the experimental example having a small residual stress, and the finally obtained displacement amount is also smaller in the comparative example than in the experimental example. Yes. Furthermore, as shown in Experimental Examples 9 to 12, the same effect was recognized even when a base metal such as nickel was used as the electrode material for the electrode materials manufactured within the range shown in the present invention.

Next, examination was carried out on the surface roughness of the laminate before firing according to Experimental Examples 13-21. 4A is an exploded perspective view showing a laminated structure of Experimental Examples 13 to 21, FIG. 4B is a perspective view showing a state of superposition before firing, and FIG. 4C is a laminated view after firing. It is sectional drawing of a body. Table 2 summarizes the conditions and test results of Experimental Examples 13-21.
(3) Experimental Examples 13 to 21: An organic solvent, a binder, a dispersant, a plasticizer, and the like are added to a PZT material powder to form a slurry, and the slurry is formed into a piezoelectric sheet having a thickness of 27 μm by a doctor blade method. . After the piezoelectric sheet was cut into a predetermined size, as shown in FIG. 4A, three piezoelectric sheets 100, 110, 120 were stacked to form a laminate 160. In addition, the internal electrodes 102 and 112 are appropriately printed on the piezoelectric sheets 100, 110, and 120 in the same manner as in the first embodiment. When the laminate 160 is pressure-bonded, the sandblasted PET sheets 150 and 152 are placed on both sides so that the sandblasted surface faces the laminate 160. Table 2 below shows the surface roughness of the PET sheets 150 and 152 of Experimental Examples 13 to 21.

  The roughness of the sandblasted surfaces of the PET sheets 150 and 152 is pressure-transferred onto the surface of the laminated body 160 after the pressure-bonding. For example, in Experimental Example 18, when the surface roughness Ra of the PET sheets 150 and 152 is 0.7 μm, the surface of the laminate 160 after pressure bonding (that is, the state before firing shown in FIG. 4B). The roughness Ra is 0.63 μm. After punching out this to a predetermined size, as shown in FIG. 4B, 20 layers of the stacked body 160 are stacked and placed on the setter 162. The PET sheets 150 and 152 are peeled off during the punching. Then, after stacking 20 layers of the laminated body 160, a zirconia thin plate having a weight of 0.8 g was placed, carbon chips were placed on the four corners of the sheath, covered, and fired at a predetermined temperature. After firing, put in an ultrasonic cleaner (40 kHz, 100 W, internal volume 2 L), apply vibration for 10 to 30 seconds, and then dry the moisture to form an external electrode as shown in FIG. A laminate 160 having a predetermined roughness on the surface was obtained.

  As a result, it was possible to prevent fusion after firing by transferring an appropriate roughness to the laminate 160 by the blasted PET sheets 150 and 152. Further, in this method, the laminate 160 is hardly deformed, and a shape defect such as an ellipse does not occur. Looking at the influence of the surface roughness of the PET sheets 150 and 152 on the ultrasonic peeling, as shown in Table 2, the roughness Ra of the fired laminate is 0.40 μm or more, that is, the PET sheet 150 and When the roughness Ra of 152 was 0.6 μm or more, it was confirmed that peeling was possible with a probability of almost 100%. On the other hand, when the roughness Ra of the PET sheets 150 and 152 is 1.2 μm or more (that is, the roughness Ra of the fired laminate 160 is 0.90 μm or more), during the removal work of the PET sheets 150 and 152, There was a phenomenon that the sheet was cut. Therefore, as shown in Experimental Examples 13 to 21, when the laminate 160 is thin, the surface roughness Ra of the laminate 160 after firing is in an appropriate range of about 0.40 to 0.75 μm. In addition, since it seems that such a range of roughness is influenced also by the thickness of laminated body 160 itself, when using a thicker laminated body, it is thought that the appropriate range of roughness also spreads.

  Thus, the adhesion of the external electrode can be enhanced by forming a predetermined roughness on the surface of the laminate 160 where the external electrode is to be formed. In addition, it is possible to reduce the inconveniences such as fusion between the laminates 160 at the time of firing, prevention of deformation, and foreign matter defects, cracks, pinhole defects, etc., which are generated by the conventional spacer method.

In addition, this invention is not limited to the Example mentioned above, A various change can be added in the range which does not deviate from the summary of this invention. For example, the following are also included.
(1) The materials, shapes, and dimensions shown in the above-described embodiments are examples, and can be appropriately changed so as to achieve the same effect. For example, in the embodiment, in order to provide a predetermined roughness on the surface of the laminate of piezoelectric sheets, a PET sheet having a blasted surface is used and the surface of the laminate is sandwiched between the blast surfaces. However, this is also an example, and an organic blast film other than PET, paper, nonwoven fabric, or the like may be used.
(2) The number of stacked piezoelectric sheets is also arbitrary, and may be appropriately increased or decreased as necessary. Further, the number of stacked layers of the laminated body shown in the experimental example is also an example, and may be appropriately changed as necessary, for example, increased to about 40 or reduced to about 12.
(3) In the above-described embodiment, the overall shape of the piezoelectric sheet or electrode is substantially circular. However, the shape can be appropriately changed as long as the same effect is obtained.
(4) When a piezoelectric speaker is constructed using the piezoelectric laminate of the present invention, the piezoelectric laminate may be attached to a diaphragm made of metal or the like. In this case, a bimorph structure in which the piezoelectric laminate is provided on the front and back of the diaphragm may be used, or a unimorph structure in which the piezoelectric laminate is provided on only one of the front and back surfaces.
(5) In Example 3 described above, the electrode is divided into two on the main surface of the piezoelectric sheet, but this is also an example, and the number of divisions may be changed as appropriate so as to achieve the same effect.
(6) Preferable application examples of the piezoelectric speaker using the piezoelectric laminate of the present invention include speakers of various electronic devices such as a mobile phone, a personal digital assistant (PDA), a voice recorder, and a PC (personal computer). It does not prevent application to other known various electronic devices.

  According to the present invention, since the external electrode is formed by a low-temperature process after sintering the laminated body, the residual compressive stress of the piezoelectric sheet can be reduced, and the accompanying deterioration of piezoelectric characteristics can be suppressed. Suitable for improving pressure. In addition, when the laminate is crimped, the surface on which the external electrode is formed is provided with a predetermined surface roughness, which improves the adhesion of the external electrode, prevents fusion during sintering, and improves molding defects. Is preferred.

(A) and (B) are exploded perspective views showing an electrode pattern and a laminated structure of Example 1 of the present invention, (C) is a plan view, (D) is a sectional view of the laminated body after firing, (E) is It is sectional drawing of the laminated body after external electrode formation. (A) and (B) are exploded perspective views showing an electrode pattern and a laminated structure of Example 2 of the present invention, (C) is a sectional view of the laminated body after firing, and (D) is a laminated body after forming external electrodes. FIG. It is a disassembled perspective view which shows the electrode pattern and laminated structure of Example 3 of this invention. (A) is an exploded perspective view showing the laminated structure of Experimental Examples 13 to 21 of the present invention, (B) is a perspective view showing a state before firing of the laminated body of the Experimental Example, and (C) is a laminated layer after firing. It is sectional drawing of a body. (A) and (B) are exploded perspective views showing an electrode pattern and a laminated structure of a conventional piezoelectric laminate, and (C) is a sectional view at the time of lamination.

Explanation of symbols

100, 110, 120: Piezoelectric sheet 102, 112: Internal electrode 104, 114: Opening 106, 116, 118, 122, 130, 132: Connection hole 140, 142: External electrode 150, 152: PET sheet 160: Laminate 162 : Setters 200, 210, 220, 230, 240: Piezoelectric sheets 202, 212, 222, 232: Electrodes 204, 214, 224, 234: Openings 206, 216, 218, 226, 228, 236, 238, 242, 250, 252: Connection holes 260, 262: External electrodes 300, 310, 320: Piezoelectric sheets 302, 306, 312, 316: Electrodes 304, 308, 314, 318: Connection lands 322, 324: Connection holes 500, 504, 510, 514 : Divided electrodes 600 and 602: Connection holes 900 and 9 0,920,930,940: piezoelectric sheets 902,904,912,922,932,942: electrodes 906,914,924,934: opening 908,916,926,936,950,952: contact hole

Claims (9)

A piezoelectric laminate in which internal electrodes and external electrodes are laminated with a piezoelectric sheet interposed therebetween, and a connection hole is formed through the piezoelectric sheet in the laminating direction so that the laminated internal electrodes are alternately connected to different external electrodes. A manufacturing method of
Obtaining a first piezoelectric sheet in which the internal electrode and the connection hole are formed, and a second piezoelectric sheet in which only the connection hole for connecting to the external electrode is formed;
A step of laminating a plurality of the first piezoelectric sheets, further laminating the second piezoelectric sheet on the first piezoelectric sheet from which the internal electrode is exposed after the lamination, and press-bonding the laminate;
Firing the post-compression laminate obtained by the step;
Forming an external electrode using a low-temperature process so as to be electrically connected to the connection hole on the surface where the connection hole of the fired laminate obtained by the step is exposed;
With including,
In the crimping step, a predetermined surface roughness is formed on a surface of the laminate on which the external electrode is formed by crimping the laminate with a rough surface of a sheet having a predetermined surface roughness. A method for manufacturing a piezoelectric laminate, comprising:   The method for manufacturing a piezoelectric laminate according to claim 1, wherein the total number of the first and second piezoelectric sheets is 3 to 5 layers.   2. The method for manufacturing a piezoelectric laminate according to claim 1, wherein the internal electrode and the external electrode are divided on main surfaces of the first piezoelectric sheet and the second piezoelectric sheet.   2. The method for manufacturing a piezoelectric laminate according to claim 1, wherein the low temperature process is a sputtering method or a plating method.   The method for manufacturing a piezoelectric laminate according to claim 1, wherein the external electrode is formed by the low temperature process at a temperature of the laminate of less than 200 ° C. Piezoelectric laminate, characterized in that it is manufactured by any of the method according to claim 1-5. 2. The piezoelectric laminate manufactured by the manufacturing method according to claim 1 , wherein a surface roughness of a surface on which the external electrode is formed is 0.40 to 0.75 μm after firing. Laminated body. The piezoelectric laminate according to claim 6 or 7, wherein the piezoelectric speaker, characterized in that mounted on at least one surface of the diaphragm. An electronic apparatus using the piezoelectric speaker according to claim 8 .

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