JP4868270B2 - Piezoelectric actuator element - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a piezoelectric actuator element used for positioning of a magnetic head and displacement and positioning of various precision parts such as optical equipment, precision equipment, and measuring equipment, and a manufacturing method thereof, and in particular, an HDD that requires high air cleanliness. The present invention relates to a piezoelectric actuator element for positioning a magnetic head used in a recording apparatus such as a (hard disk drive).
[0002]
[Prior art]
A piezoelectric element using a piezoelectric phenomenon that obtains displacement by applying a voltage is excellent in minute displacement control and responsiveness, and has been conventionally used in various minute displacement control devices.
In recent years, with the increase in recording density of hard disks, which are recording devices, in computers, home appliances, etc., advanced positioning control of recording / reading heads has been required, and it has been conventionally used as a displacement mechanism for these heads. Positioning has become difficult with only a VCM (voice coil motor) using permanent magnets. For this reason, for example, as disclosed in JP-A-2-2677782 and JP-A-9-265738, primary positioning is performed by VCM, and secondary positioning is performed in combination with piezoelectric actuator elements, in other words, minute displacement. Actuator came out.
The conventional manufacturing method of such a piezoelectric actuator element will be outlined.
First, a ceramic powder material, a binder, a solvent, and the like are kneaded to prepare a paste, which is molded to produce a green sheet. Further, a conductive material, a binder, a solvent, and the like are kneaded, and an internal electrode layer paste is prepared. Next, the internal electrode layer paste is printed on the green sheet so as to have a predetermined pattern, and then a predetermined number of the pastes are stacked and pressed to obtain a stacked body. The laminated body is subjected to a desired shape processing by punching or the like and then fired to obtain a thin plate-like sintered body. Alternatively, the thin plate-shaped sintered body is processed so as to have a desired shape, or the thin plate-shaped sintered body is cut into an appropriate size, and then the shape processing is performed. Shape processing refers to processing for providing a hole or notch in a thin plate-like sintered body.
[0003]
[Problems to be solved by the invention]
When the above-described piezoelectric actuator element is used in an HDD (hard disk drive) or the like, an extremely thin piezoelectric actuator element is required and high dimensional accuracy is required. In response to such dimensional requirements, sintering of thin articles, particularly those with a thickness of 0.5 mm or less, is expected to have the required dimensions by grinding, dicer processing, etc., since problems such as warpage and characteristic deterioration are assumed. It is common. However, in the piezoelectric actuator element obtained in this way, particles (fine particles) generated by the processing or particles that have started to peel off from the processed surface of the piezoelectric actuator element are mounted on the HDD device, and then the piezoelectric actuator element is Decreasing reliability, such as dropping from the actuator element and adhering to the magnetic disk surface, damaging the magnetic recording data, or in some cases making the HDD used by the actuator element inaccessible due to particles generated by itself There were inherent factors. This is not limited to HDDs, but has a universal problem of generating particles in a clean environment. An object of the present invention is to provide a highly reliable piezoelectric actuator element for a magnetic recording apparatus by solving problems caused by the generation of particles.
[0004]
[Means for Solving the Problems]
As a result of searching for the cause of the generation of particles, the present inventor has found that there are many fine particles dropped from the surface of the piezoelectric actuator element, and reached the present invention.
[0005]
The present invention sinters a molded body in which a green sheet and an electrode pattern are laminated to form a preliminary sintered body of 0.5 mm or less, and after processing the preliminary sintered body, the processed surface is sintered. Secondary sintering as a binding skin, and when the primary sintering and / or secondary sintering, a sintered object is disposed on a plate of a piezoelectric sintered body made of a piezoelectric material. A method of manufacturing a piezoelectric actuator element for a magnetic recording apparatus, comprising sintering.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
First, a method for manufacturing the piezoelectric actuator element of the present invention will be described. In the present invention, the piezoelectric material is a ceramic piezoelectric material such as PZT {Pb (Zr, Ti) O3}, PT (PbTiO3), PLZT {(Pb, La) (Zr, Ti) O3}, barium titanate (BaTiO3), etc. Is preferred. The piezoelectric material powder is molded to obtain a molded body. Usually, a piezoelectric material powder is made into a slurry with an appropriate solvent to produce a green sheet by a doctor blade method, and a predetermined electrode pattern is printed and laminated in many cases. However, the present invention is not limited thereto, and a compact may be produced by molding a piezoelectric material powder with a mold. Next, the compact is sintered. When Pb such as PZT, PT, and PLZT is contained , the compact is disposed on a piezoelectric sintered compact plate made from a piezoelectric material powder. And sinter. Thereby, replenishment of lead (Pb), which is a main constituent element of the piezoelectric material that evaporates and scatters from the surface of the molded body due to sintering, can be performed. As a result, the sintered density is improved, and even a thin element having a thickness of 0.5 mm or less can be sintered without warping, so that post-processing is not required as in the prior art. Furthermore, when strict dimensional accuracy is required, the molded body is primarily sintered to obtain a pre-sintered body, and then subjected to secondary sintering by cutting and dicing with a diamond blade or the like. May be. When lead that easily evaporates is lost from the surface of the piezoelectric body due to primary sintering, secondary sintering can lead to diffusion of lead from the inside of the piezoelectric body toward the surface of the piezoelectric body and improve the lead density on the surface. The surface layer roughened by the processing is repaired, and the surface is sintered and the sintered skin can be stabilized so that particles are not generated. Here, the primary sintering is performed so as to obtain a final density or a sintering density close thereto, and the conditions vary depending on the composition of the piezoelectric material and the electrode material , but are approximately 1030 to 1160 ° C. for about 2 hours in the atmosphere. Sinter. And it is preferable to perform secondary sintering provided with the annealing effect below the temperature of primary sintering so that it may not oversinter. In addition, by applying a secondary sintering while applying a load by placing a plate-like article on the sintered body subjected to the primary sintering, the warp that would occur due to the sintering is corrected in advance. Thus, it is possible to obtain a piezoelectric actuator element that does not require post-processing and causes particle generation. In the primary sintering and / or secondary sintering, if the object to be sintered is placed and sintered on a plate of a piezoelectric sintered body made of a piezoelectric material, molding is performed by sintering. Lead (Pb), which is the main constituent element of the piezoelectric material that evaporates and scatters from the surface of the body, can be supplied. As a result, the sintered density is improved and sintering can be performed without warping, so no post-processing is required. As described above, since the present invention employs an unprecedented manufacturing method, a piezoelectric actuator element in which the element thickness is 0.5 mm or less and the surface of the element remains substantially sintered is obtained. Can do. And a lower limit can manufacture to about 50-70 micrometers.
[0007]
As described above, it is possible to provide a piezoelectric actuator element in which the generation of particles is suppressed. However, a further effect can be obtained by covering a part or all of the piezoelectric actuator element with a flexible resin. In particular, the generation of particles can be prevented. Conventionally, a piezoelectric actuator coated with a resin has been disclosed, but the resin coating according to the present invention is completely different in its purpose and function. In other words, the coating according to the present invention is mainly intended to prevent deterioration of insulation resistance caused by silver migration or the like by blocking the electrode portion from the external environment containing moisture. It aims at suppressing the scattering of the particles from. Further, the conventional resin coating has a thickness of sub-millimeters to millimeters due to the difference in purpose, whereas the resin coating of the present invention has a thickness of 1 μm to 100 μm, preferably 3 μm to 20 μm. If the coating is too thick, it is difficult to maintain high dimensional accuracy, and the purpose is to prevent particle scattering, so there is no practical benefit of making it thicker than necessary. On the other hand, if the coating is too thin, defects are likely to occur in the coating, and the scattering of the particles cannot be sufficiently prevented. By covering the resin, it is possible to provide a function of ensuring insulation between the piezoelectric actuator element and other members at the same time. Also from the viewpoint of insulation, the thickness is preferably equal to or greater than the above-mentioned fixed value. The type of the resin is not particularly limited, but it is preferable that the resin has flexibility so as not to disturb the thin piezoelectric actuator element. Further, silicon-based, sulfur-based, and chlorine-based gases that adversely affect the hard disk drive and materials that do not generate contamination are preferable. Further, in consideration of the environmental temperature in the hard disk drive and the heat generated from the element itself, it is preferable that substantially no alteration occurs even at about 60 ° C., more preferably about 100 ° C. The film forming method is not particularly limited, but the film can be formed by, for example, vapor deposition or spraying. The coating is preferably formed on the entire piezoelectric actuator element. However, it may be formed on a part of the piezoelectric actuator element depending on the assembly arrangement, such as reducing the exposed portion of the piezoelectric actuator element by bonding with other members. A sufficient effect can be obtained.
[0008]
【Example】
A piezoelectric actuator element 1 shown in FIG. 3 was manufactured by using PZT (piezoelectric constant d ₃₁ = −285 × 10 ⁻¹² m / V) as a piezoelectric material and utilizing lamination of green sheets by a doctor blade method. The piezoelectric material layer had a thickness of 20 μm, and a 10-layer laminate (total thickness: 0.2 mm) of 8 layers sandwiched between electrode layers 5 on both sides and one upper and lower layer serving as a lid. The displacement generator 2 has a length of 2 mm, a width of 0.5 mm, and a thickness of 0.2 mm. The width of the slit hole 3 between the two displacement generators is 0.5 mm, and the displacement generator is subjected to polarization treatment. did.
A voltage of 20 V was applied to this actuator in the same direction as the polarization direction.
Generation of particles by reciprocating between two predetermined addresses on a magnetic disk for 7 consecutive days by an evaluation device built in the HDD so that this piezoelectric actuator element is primarily positioned by VCM and secondaryly positioned by piezoelectric actuator element. Was observed. As a comparative example, a conventional product fabricated and post-processed was used.
FIG. 1 shows a photomicrograph showing the surface texture of the piezoelectric actuator element according to the present invention, and FIG. 2 shows a photomicrograph showing the surface texture of the piezoelectric actuator element of the comparative example. In FIG. 1 according to the present invention, the particles are firmly bonded to each other, and there is no particle that is likely to peel off on the surface. In FIG. 2 of the comparative example, due to processing deterioration, the presence of particles that are likely to be peeled off is observed.
The number of particles is evaluated by applying the same adhesive tape to one surface of the piezoelectric actuator element after the test, peeling it off with the same force, and then measuring the surface of the tape contacting the element with a microscope 100 μm × 100 μm The number of particles having a size of 1 μm or more existing in the region was counted. In the present invention, there were two particles, but in the comparative example, there were as many as 50 particles.
[0009]
After a piezoelectric actuator element was fabricated in the same manner as in the above-described example, a film was formed by spraying a vinyl acetate resin on the surface of the element, and the same evaluation as in the above-described example was performed. The thickness of the coating was 8 μm. Particles of 1 μm or more were not confirmed in a 100 μm × 100 μm region of the tape surface in contact with the device.
[0010]
【Effect of the invention】
According to the present invention, generation of particles can be prevented, and a piezoelectric actuator element suitable for use in a clean environment such as an HDD (hard disk drive) can be provided.
[Brief description of the drawings]
FIG. 1 is a metallographic micrograph of the surface texture of a piezoelectric actuator element of the present invention.
FIG. 2 is a metallographic micrograph of the surface texture of a piezoelectric actuator element of a comparative example.
FIG. 3 is a perspective view of a piezoelectric actuator element according to an embodiment of the present invention.

Claims (1)

Sintering the green sheet and the green body and electrode body laminated body to make a pre-sintered body of 0.5 mm or less, and after processing the pre-sintered body, the processed surface is sintered Secondary sintering and
A piezoelectric material for a magnetic recording device, wherein a sintered object is disposed on a plate of a piezoelectric sintered body made of a piezoelectric material and sintered during the primary sintering and / or secondary sintering. Actuator element manufacturing method.

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