JP2009027052A - Processing method for piezoelectric element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a processing method for piezoelectric element capable of preventing breakage of a square pillar, when slicing. <P>SOLUTION: The processing method for piezoelectric element by a cutting device includes a first slicing process for slicing the piezoelectric element at a plurality of times in a first direction in a predetermined width at a predetermined interval, and a second slicing process for slicing the piezoelectric element at a plurality of times, in a second direction that is orthogonal to the first direction in a predetermined width at a predetermined interval. In the first and second slicing processes, a cutting blade rotates at a peripheral speed 1,400-4,100 m/min and a feed speed of the piezoelectric element is 1-5 mm/sec, while cooling water is supplied to the surface of the piezoelectric element. The square pillar, formed in the second slicing process, has longitudinal and lateral lengths of 15-30 μm, a height of 300-400 μm, and the interval between the square pillars is 15-30 μm. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for processing a piezoelectric element used as an ultrasonic probe.

  Ultrasonic probes using piezoelectric elements (piezoelectric ceramics) have been improved to improve sensitivity year by year, and are widely used in medical equipment such as ultrasonic diagnostic apparatuses. One of the methods for improving the sensitivity is to reduce the size of the piezoelectric vibrator or change its shape.

  As the piezoelectric element, for example, piezoelectric ceramics such as lead zirconate titanate (PZT), lead titanate, barium titanate, bismuth titanate, etc. are used. In particular, PZT piezoelectric ceramics have a higher electromechanical coupling coefficient. Since it has a dielectric constant, it is widely used.

  In particular, recently, an ultrasonic probe in which piezoelectric transducers are arranged in an array of square prisms that require vertical and horizontal slicing, rather than rectangular prisms sliced in only one direction. A child has been proposed.

  As for the size of the piezoelectric vibrator, the aspect ratio of the regular square column is 15-30 μm and the height is 300-400 μm, and the processing difficulty is greatly increased. Improvement is needed.

  Dicing is a processing method that uses a dicing device (cutting device) to divide a plate (work) with a cutting blade that rotates at high speed. However, compared to processing methods such as etching and laser, the control of the height and shape of the prisms. It is a processing method that is often used because it can be easily processed and can be processed with high accuracy at a relatively low cost.

  For example, Japanese Patent Laid-Open No. 11-318893 discloses an ultrasonic probe in which regular quadrangular prism piezoelectric vibrators are arranged in an array. This publication does not mention any method for slicing the piezoelectric element.

  However, from the description that the insulating filler is filled in the gap between the piezoelectric vibrators sliced in one direction to improve the strength, in order to increase the rigidity at the time of processing the piezoelectric element which is a brittle material, It has been suggested that after slicing in the direction, the groove is filled with an insulating resin, and then the piezoelectric element is rotated 90 ° to perform slicing again.

However, with this processing method, the insulating resin as the filler is harder to cut than the lead zirconate titanate that is the material of the piezoelectric element, which may cause the square column to be damaged. In particular, when a cutting blade with a small abrasive grain size (for example, mesh size # 1500 to # 3000) is used in order to suppress the size of the quadrangular prism to be small and to prevent chipping during processing as much as possible, Clogging occurs, and the square column can be damaged, and eventually the square column can be damaged.
JP 11-318893 A

  Therefore, as a result of examining a method for realizing processing of a fine quadrangular prism without filling a resin in the slice groove of the piezoelectric element, the inventor of the present application investigated the cause of the occurrence of the quadrangular prism breakage, and the cause I came to find.

  That is, optimization of the machining conditions when the cutting blade collides with the workpiece (piezoelectric element) at high speed, optimization of the machining conditions that the high load is applied to the workpiece, and the impact of the cooling water accelerated by the high-speed rotating cutting blade on the workpiece As a result, it has been found that a phenomenon that the quadrangular prism breaks from the processed soba has occurred.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a method for processing a piezoelectric element capable of preventing damage to a rectangular column during slicing. .

  According to the present invention, a chuck table for holding a plate-like piezoelectric element, a cutting means for rotatably supporting a cutting blade for cutting the piezoelectric element held by the chuck table, and the chuck table with respect to the cutting blade A piezoelectric element machining method using a cutting device comprising a chuck table feed means that moves and a cooling water supply means that supplies cooling water to the surface of the piezoelectric element, wherein the piezoelectric element is moved in a first direction. A first slicing step of slicing a plurality of times at a predetermined width and a predetermined interval; and a second slicing of the piezoelectric element at a predetermined width and a predetermined interval in a second direction orthogonal to the first direction. A slicing step, wherein the first and second slicing steps supply the cutting blade 1400 while supplying cooling water to the surface of the piezoelectric element by the cooling water supply means. While rotating at a peripheral speed of 4100 m / min and carrying out the feed speed of the piezoelectric element at 1 to 5 mm / sec, the rectangular column formed in the second slicing step has a vertical and horizontal length of 15 to 30 μm. Further, there is provided a method for processing a piezoelectric element, characterized in that the height is 300 to 400 μm and the interval between the square pillars is 15 to 30 μm.

  Preferably, the peripheral speed of the cutting blade is 1500 to 3900 m / min, and the cooling water supplied from the cooling water supply means forms a water layer having a thickness of 1 to 5 mm on the upper surface of the piezoelectric element.

  According to the piezoelectric element processing method of the present invention, the piezoelectric element is sliced in the vertical direction and the horizontal direction without damaging the quadrangular column to form a plurality of square columns aligned in the vertical direction and the horizontal direction. Can do.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows the appearance of a cutting device (dicing device) 2 used for slicing according to the present invention. Reference numeral 4 denotes a chuck table that holds a workpiece (a piezoelectric element in the present invention), and is configured to be rotatable while being moved in the X-axis direction by a feed mechanism (not shown).

  An alignment unit 6 is disposed above the movement path of the chuck table 4 in the X-axis direction. The alignment unit 6 includes an imaging unit such as a CCD camera that images the surface of the piezoelectric element to be cut, and an image acquired by the imaging unit is displayed on the display unit 14.

  On the left side of the alignment means 6, a cutting means 8 for cutting a work (piezoelectric element) held on the chuck table 4 is disposed. The cutting means 8 is configured integrally with the alignment means 6 and is configured to be movable in the Y-axis direction and the Z-axis direction in conjunction with each other.

  The cutting means 8 is configured by attaching a cutting blade 10 to the tip of a rotatable spindle 9 and is movable in the Y-axis direction and the Z-axis direction. The cutting blade 10 is located on an extension line in the X-axis direction of an imaging unit (not shown).

  A cooling water supply means 12 is arranged upstream of the piezoelectric element 18 to be cut and supplies cooling water to the surface of the piezoelectric element as shown in FIGS. A transparent slide cover 16 opens the slide cover 16 when the workpiece is carried in and out, and closes the slide cover 16 when the workpiece is cut.

  Referring to FIG. 2, a perspective view of the piezoelectric element 18 after cutting is shown. The piezoelectric element 18 is made of, for example, piezoelectric ceramics such as lead zirconate titanate (PZT), lead titanate, barium titanate, bismuth titanate, etc., and in particular, an electric machine having high lead zirconate titanate (PZT). It is preferable because it has a coupling coefficient and a dielectric constant.

  According to the piezoelectric element processing method of the embodiment of the present invention, the piezoelectric element 18 is sliced a plurality of times at a predetermined width and a predetermined interval in the first direction (X1 direction) in the first slicing step. Next, after rotating the piezoelectric element 18 by 90 °, in the second slicing step, the piezoelectric element 18 is moved a plurality of times in the second direction (X2 direction) orthogonal to the first direction at the predetermined width and the predetermined interval. Sliced.

  By going through the first and second slicing steps, a plurality of square pillars 20 aligned in the X1 direction and the X2 direction are formed. In FIG. 2, the vertical axis of the square column 20 is a, the horizontal column is b, and the interval between adjacent rectangular columns 20 is c. Moreover, it is preferable that it is t / a = 10-27, when the height of the square pillar 20 is set to t.

  Preferably, the rectangular column 20 formed in the first and second slicing steps has a length a of 15 to 30 μm, a height t of 300 to 400 μm, and a distance c between the rectangular columns 20 of 15 to 15 μm. 30 μm.

  Next, with reference to FIG. 3 and FIG. 4, the processing method of the piezoelectric element concerning embodiment of this invention is demonstrated in detail. 3 is a plan view when the piezoelectric element 18 is processed, and FIG. 4 is a cross-sectional view thereof. The piezoelectric element 18 is attached to the adhesive tape 24, and the outer peripheral edge of the adhesive tape 24 is attached to the annular frame 22. As a result, the piezoelectric element 18 is supported by the annular frame 22 via the adhesive tape 24.

  The piezoelectric element 18 is sucked and held on the chuck table 4 via an adhesive tape 24. In this state, the first slicing step in the X1 direction in FIG. 2 is performed by moving the chuck table 4 in the X-axis direction while rotating the cutting blade 10.

  At this time, the first slicing step by the cutting blade 10 is performed while supplying the cooling water from the cooling water supply means 12 to the surface of the piezoelectric element 18 as indicated by the arrow 13. Preferably, the cooling water 13 supplied from the cooling water supply means 12 forms a water layer having a thickness of 1 to 5 mm on the surface of the piezoelectric element 18.

  Thereby, the heating of the piezoelectric element 18 and the cutting blade 10 during the slice processing of the piezoelectric element 18 can be prevented. Reference numeral 26 denotes a cutting water supply means that is normally attached to the cutting apparatus 2, but the supply of the cutting water from the cutting water supply means 26 is stopped when slicing the piezoelectric element 18 of this embodiment.

  When all the slicing processes in the X1 direction shown in FIG. 2 are completed, the chuck table 4 is rotated by 90 °, and the slicing process in the X2 direction is similarly performed. Thereby, a plurality of quadrangular prisms 20 aligned in the X1 direction and the X2 direction as shown in FIG. 2 can be formed. Preferably, the quadrangular prism 20 is a regular quadrangular prism.

  Table 1 shows the results of various experiments performed by changing the feed speed of the piezoelectric element 18, the blade peripheral speed of the cutting blade 10, and the amount of cooling water supplied from the cooling water supply means 12.

表１を観察すると、切削ブレード１０の周速が１３００ｍ／分以下であると角柱作成成功率が非常に低くなっており、また切削ブレード１０の周速が４２００ｍ／分以上でも角柱作成成功率が悪化している。よって、切削ブレード１０の周速は１４００〜４１００ｍ／分の範囲内が好ましく、より好ましくは１５００〜３９００ｍ／分の範囲内である。

Observing Table 1, when the peripheral speed of the cutting blade 10 is 1300 m / min or less, the prism creation success rate is very low, and even when the peripheral speed of the cutting blade 10 is 4200 m / min or more, the prism creation success rate is high. It is getting worse. Therefore, the peripheral speed of the cutting blade 10 is preferably in the range of 1400 to 4100 m / min, and more preferably in the range of 1500 to 3900 m / min.

  Further, the prisms were created by changing the feed speed of the piezoelectric element 18 in various ways. When the feed rate was 7 mm / sec, the prism creation success rate was extremely deteriorated. Conversely, when a very slow feed rate of 0.5 mm / sec was adopted, the prism creation success rate was similarly deteriorated. Therefore, the feed speed of the piezoelectric element 18 at the time of cutting is preferably in the range of 1 to 5 mm / second.

  In most experiments, the experiment was conducted while the supply of the cutting water from the cutting water supply means 26 was stopped and the cooling water supply means 12 was supplying 1.5 l / min of cooling water. 1, the cooling water supply is stopped and a small amount of cutting water, that is, 0.3 l / min of cutting water is supplied from the cutting means 26, while the feed speed of the piezoelectric element 18 is 3 mm / second and the peripheral speed of the cutting blade 10 is about 3300 m. When the experiment was performed at a rate of 10 minutes, the success rate of prism creation was 90.3%.

  From this result, when slicing the piezoelectric element 18 while supplying cutting water from the cutting water supply means 26, the cutting water accelerated by the cutting blade 10 hits the piezoelectric element 18. It has been found that the probability of becoming higher is higher.

  Therefore, in the slice processing method of the piezoelectric element of the present embodiment, it has been found that it is preferable to stop the supply of the cutting water from the cutting means 26 and perform the slicing process while supplying the cooling water from the cooling water supply means 12. . The reason is considered that the cooling water supply means 12 is arranged at a considerable distance from the cutting blade 10, so that the cooling water is not likely to be accelerated by the high speed rotation of the cutting blade 10.

  As a comparative example, FIG. 5 shows a cross-sectional view when processing the workpiece (piezoelectric element) 18 while supplying cutting water from the cutting water supply means 26. This processing condition is the same as the experiment No. in Table 1. Corresponds to 1. That is, in this case, the cutting water 27 supplied from the cutting water supply means 26 is accelerated by the high speed rotation of the cutting blade 10 and collides with the piezoelectric element 18 being cut. As a result, the success rate of prism creation is deteriorated.

  FIG. 6 shows how the machining load changes when the feed speed of the piezoelectric element 18 is slow (A) and when it is fast (B). Reference numeral 28 denotes diamond abrasive grains electrodeposited on the outer periphery of the cutting blade 10. In fact, countless abrasive grains are electrodeposited, but only one is shown as a substitute.

  As shown in FIG. 6A, when the feed speed of the piezoelectric element 18 is slow (for example, 2 mm / second), the cutting removal volume 30a per rotation of the cutting blade 10 is small, but the feed speed of the piezoelectric element 18 is fast. In some cases (for example, 4 mm / second), the cutting removal volume 30b per rotation of the cutting blade 10 is larger than 30a when the cutting removal volume 30b is slow.

  Therefore, if the feed speed of the piezoelectric element 18 is high, the volume of the piezoelectric element 18 that the cutting blade 10 cuts per rotation increases, so that the load applied to the piezoelectric element 18 during cutting becomes large, causing damage to the prism. .

  As shown in Table 1, the feed speed of the piezoelectric element 18 is preferably 5 mm / second or less. Even when the feed speed of the piezoelectric element 18 is too slow, the success rate of prism creation is low from Table 1, but this may be due to the vibration of the cutting blade 10 during slicing.

  6A and 6B, the peripheral speed of the cutting blade 10 is a constant peripheral speed (for example, about 1600 mm / min). On the contrary, the feed amount of the piezoelectric element 18 is constant, It is understood that when the peripheral speed of the cutting blade 10 is changed, the cutting removal volume per one rotation of the blade increases as the rotation speed increases.

  Two methods shown in FIG. 7 can be considered for fixing the piezoelectric element during the processing of the piezoelectric element. FIG. 7A shows a fixing method in which the piezoelectric element 18 described above is attached to the adhesive tape 24 and the outer peripheral portion of the adhesive tape 24 is attached to the annular frame 22.

  In the method shown in FIG. 7B, the piezoelectric element 18 is a hard plate-like substrate (plate glass, carbon plate, plastic plate, etc.) 32 and a heat softening resin (hot melt wax) (for example, Nikka Seiko Co., Ltd.). In this method, the substrate 32 is fixed to the chuck table 4 by vacuum.

  For example, the substrate 32 is placed on a hot plate heated to about 130 ° C., the ADFIX wax 34 is melted on the substrate 32, and then the piezoelectric element 18 is placed on the ADFIX wax 34. When the substrate 32 is taken out of the hot plate and the wax is cooled, the wax 34 is cured and exhibits a very strong adhesive force.

  According to this method, the adhesive force is very high as compared with the adhesive tape 24. When the piezoelectric element 18 is peeled off, the piezoelectric element 18 is peeled from the substrate 32 by ultrasonic cleaning by immersion in alcohol or the like.

It is an external appearance perspective view of the cutting device suitable for using for the processing method of this invention. It is a perspective view of the piezoelectric element after slicing and forming a prism. It is a principal part top view of the cutting device used for the processing method of this invention embodiment. It is sectional drawing of the cutting device of FIG. It is sectional drawing of the cutting device for demonstrating a comparative example. FIGS. 6A and 6B are diagrams for explaining the relationship between the piezoelectric element feed speed and the machining load, FIG. 6A shows a case where the feed speed is slow, and FIG. 6B shows a case where the feed speed is fast. FIG. 7A shows a method for fixing a piezoelectric element using an adhesive tape, and FIG. 7B shows a method for fixing a piezoelectric element using a substrate and hot melt wax.

Explanation of symbols

4 Chuck table 10 Cutting blade 12 Cooling water supply means 18 Piezoelectric element 20 Square pillar 22 Frame 24 Adhesive tape 32 Substrate 34 Hot melt wax

Claims (2)

A chuck table for holding a plate-like piezoelectric element, a cutting means for rotatably supporting a cutting blade for cutting the piezoelectric element held on the chuck table, and a chuck table for moving the chuck table relative to the cutting blade A method of processing a piezoelectric element using a cutting device comprising a feeding means and a cooling water supply means for supplying cooling water to the surface of the piezoelectric element,
A first slicing step of slicing the piezoelectric element a plurality of times in a first direction at a predetermined width and a predetermined interval;
A second slicing step of slicing the piezoelectric element in a second direction orthogonal to the first direction at a predetermined width and a predetermined interval,
In the first and second slicing steps, the cutting blade is rotated at a peripheral speed of 1400 to 4100 m / min while supplying cooling water to the surface of the piezoelectric element by the cooling water supply means, and the feeding speed of the piezoelectric element Is carried out at 1 to 5 mm / second,
The rectangular column formed in the second slicing step has a vertical and horizontal length of 15 to 30 μm, a height of 300 to 400 μm, and an interval between the square columns of 15 to 30 μm. Element processing method.   The peripheral speed of the cutting blade is 1500 to 3900 m / min, and the cooling water supply by the cooling water supply means forms a water layer having a thickness of 1 to 5 mm on the surface of the piezoelectric element. The method for processing a piezoelectric element according to claim 1.

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