KR20050109335A - Ultrasonic probe and preparing method thereof - Google Patents

Abstract

The present invention relates to an ultrasonic transducer and a method of manufacturing the same, and the ultrasonic transducer according to the present invention includes two electrodes (a first electrode and a second electrode) positioned on an ultrasonic transceiving surface and an opposite surface of a piezoelectric single crystal wafer. It has a structure separated by grooves formed on the main surface of the piezoelectric single crystal wafer at a predetermined distance inward from each other side of the single crystal, so that the grounding electrode plate is connected to the first electrode on the side of the piezoelectric single crystal. Since the bonded and signal printed circuit board can be fixedly bonded to the second electrode on the main surface of the piezoelectric single crystal wafer in a terminal structure folded at right angles, an unnecessary vibration can be effectively generated by electrode separation due to groove formation while exhibiting excellent piezoelectric characteristics. Can be suppressed.

Description

Ultrasonic probe and manufacturing method thereof {ULTRASONIC PROBE AND PREPARING METHOD THEREOF}

The present invention relates to a novel ultrasonic transducer and a method for manufacturing the same, and more particularly, to an ultrasonic transducer having excellent performance with no high temperature treatment and reduced vibration.

Recently, there has been a demand for piezoelectric materials of superior properties to lead zirconia titanate (Pb (Zr, Ti) O ₃ , hereinafter PZT), and such materials include lead zirconia niobate-lead titanate (Pb (Zn _1/3 Nb _{2). / 3)} O ₃ -PbTiO _3, below PZN-PT) or lead magnesium niobate-lead titanate _{(Pb (Mg 1/3 Nb 2/3)} O 3 -PbTiO 3, hereinafter PMN-PT) single crystal piezoelectric developed It became.

These piezoelectric single crystals have an electromechanical coupling coefficient (k ₃₃ ) that exhibits electro-acoustic conversion efficiency over conventional PZT ceramics, and the piezoelectric coefficient (d ₃₃ ), which determines the emission and reception performance, is about two times better. It is shown. However, the PMN-PT single crystal has a disadvantage in that its phase transition temperature is lower than that of PZT, which is very weak to heat. In the case of PZT, the phase transition temperature is in the range of 200 to 385 ° C, whereas for example, 0.67PMN-0.33PT, the phase transition temperature is about 150 ° C. Therefore, when heat higher than the phase transition temperature is applied to these piezoelectric single crystals, the polarization treatment is released and vibration is impossible. Due to the low phase transition temperature as described above, the PMN-PT single crystal is very sensitive to the heat generated in the transducer manufacturing process and is also affected by the heat applied during the curing process required for bonding of the stacks.

Meanwhile, in the manufacturing process of the probe, a soldering process or an epoxy paste bonding process is generally used for electrical connection between the wafer and the flexible printed circuit board (FPCB). The soldering process is simple, but the heat applied to the process is a problem, and the use of epoxy paste does not require excessive heat on the wafer, but there is a layer between the wafer and the backing layer. Due to the insertion, the characteristics of the transducer may be adversely affected, and also, since the FPCB needs to be precisely manufactured and bonded, there is a disadvantage in that the cost is high.

Recently, it has been attempted to reduce the thickness of the epoxy layer inserted using silver epoxy paste, which is more conductive than ordinary epoxy paste, but the problem is still not solved.

Accordingly, an object of the present invention is to provide a novel electrode design and FPCB bonding method that can be electrically connected to a wafer well without affecting the performance of the transducer in fabricating the transducer using a piezoelectric single crystal wafer.

In order to achieve the above object, in the present invention

(A) a piezoelectric single crystal substrate having a first main surface, a second main surface, a first side surface, and a second side surface,

(B) two grooves formed on the first main surface and the second main surface of the piezoelectric single crystal substrate, respectively, spaced apart from the second side surface and the first side surface of the piezoelectric single crystal substrate and extending in the longitudinal direction of the piezoelectric single crystal substrate. (A) a part of the first side and the second main surface of the piezoelectric single crystal substrate and a first electrode layer substantially covering the first main surface, and (b) a part of the second side and the first main surface of the piezoelectric single crystal substrate And a second electrode layer substantially covering the second main surface,

(C) a back layer bonded to the electrode layer located on the second main surface of the piezoelectric single crystal substrate,

(D) an electrode plate for ground bonded to the first electrode layer on the first side of the piezoelectric single crystal substrate, and

(E) the terminal portion is folded at right angles and has a structure including a flexible printed circuit board for signaling, past the second electrode layer on the second side of the piezoelectric single crystal substrate and bonded to the second electrode layer in front of a groove located on the first main surface. An ultrasonic transducer is provided.

In the present invention,

(1) depositing an electrode layer on the first main surface, the second main surface, the first side, and the second side of the piezoelectric single crystal substrate,

(2) grooves are formed in the longitudinal direction of the piezoelectric single crystal substrate at positions spaced apart from the second side surface and the first side surface on the first main surface and the electrode layer on the second main surface of the piezoelectric single crystal substrate, respectively, The electrode layer formed in step 1) is separated into a first electrode layer and a second electrode layer,

(3) forming a backing layer on the electrode layer located on the second main surface of the piezoelectric single crystal substrate,

(4) A grounding electrode plate is bonded to the first electrode layer located on the first side of the piezoelectric single crystal substrate, and the second electrode layer is positioned on the first main surface past the second electrode layer on the second side of the piezoelectric single crystal substrate. Provided is a method of manufacturing an ultrasonic probe, comprising bonding a flexible printed circuit board for a signal having a structure in which a distal end is folded at right angles in front of a groove.

Hereinafter, the present invention will be described in more detail.

Ultrasonic transducers generally include a wafer using a piezoelectric single crystal, an ultrasonic transmitting / receiving element having a pair of electrodes positioned on the opposite side of the ultrasonic transmitting / receiving surface of the wafer, and an acoustic matching layer formed on the electrode connected to the transmitting / receiving surface And a ground electrode plate and a flexible printed circuit board for signaling, respectively, connected to the electrodes on the ultrasonic transceiving surface and the electrodes on the opposite side thereof. In addition, an acoustic lens is positioned on the acoustic matching layer to cover the entire acoustic matching layer.

The ultrasonic probe according to the present invention is characterized in that two electrodes (first electrode and second electrode) positioned on the ultrasonic transceiving surface of the piezoelectric single crystal wafer and on the opposite side thereof have an electrode layer and a ground electrode plate or printed from each other side of the piezoelectric single crystal. It has a structure separated by a groove formed in the inner position of the epoxy paste coating distance for bonding the circuit board, so that the grounding electrode plate is bonded to the first electrode on the side of the piezoelectric single crystal and the signal printed circuit The substrate is fixedly bonded to the second electrode in a terminal structure folded at right angles.

The ultrasonic probe according to the present invention can be manufactured by a process as shown in FIGS. 2 and 3.

First, as shown in FIG. 2A, a piezoelectric single crystal wafer substrate 10 having a first main surface 10a, a second main surface 10b, a first side surface 10c, and a second side surface 10d is prepared. Similarly, the electrode layers may be sputtered, electron-beam, thermal evaporation or electroplating on the four sides 10a, 10b, 10c and 10d of the single crystal wafer. (20 '') is deposited.

The single crystal substrate used in the ultrasonic probe of the present invention has a thickness in the range of 20 to 500,000 μm, preferably in the range of 50 to 400 μm. The electrode layer may be composed of a conductive film, such as chromium, copper, nickel, gold, respectively, the electrode thickness may be in the range of 100 to 10,000Å.

Subsequently, as shown in FIG. 2C, grooves 30 and 30 ′ are formed in the electrode layers on the first and second main surfaces of the piezoelectric single crystal wafer, respectively, to separate the electrode layers 20 ″ into two electrode layers 20 and 20 ′. Such separation can be performed by, for example, dicing a groove of a predetermined depth using a dicing saw, and specifically, the grooves 30 and 30 'are respectively formed of the piezoelectric single crystal wafer. (A) a first electrode layer positioned within a predetermined distance from the second side and the first side of the substrate, the electrode layer covering (a) a portion of the first side and the second main surface and a first main surface of the piezoelectric single crystal wafer; A second electrode layer substantially covering the second side, part of the first main surface, and the second main surface of the piezoelectric single crystal wafer is separated into an electrode plate for grounding later and the second electrode layer for later signaling. Combined with FPCB.

The grooves 30 and 30 'are respectively positioned at an inner side of a wafer or more from a side surface of a wafer, for example, an adhesive coating distance for bonding an electrode layer and a ground electrode plate or a printed circuit board (FPCB), for example, about 1 to 1.5 mm. It is preferable for provision of an adhesive application space to be formed in an inner position. The groove is also preferably formed in the depth of the range of 70 to 80% of the wafer thickness in terms of suppressing vibration generation. The adhesive may be an epoxy paste, preferably a silver epoxy paste.

Subsequently, as shown in FIG. 3A, a backing layer 40 is formed on the wafer 100 on which the electrode layer is formed, that is, on the electrode layer located on the second main surface of the piezoelectric single crystal wafer. Next, as shown in FIGS. 3B and 3C, the ground electrode plate 50 is bonded to the first electrode layer 20 positioned on the first side surface 10c of the piezoelectric single crystal wafer using the silver epoxy paste 70. A signal flexible printed circuit board (FPCB) 60 is bonded to the second electrode layer 20 ', which passes through the second electrode layer on the second side 10d of the piezoelectric single crystal substrate. 1 is bonded to the second electrode layer 20 within the limit of not exceeding the groove 30 located on the main surface 10a. At this time, the signal FPCB is fixed at the distal ends folded at right angles, which does not significantly affect the vibration of the wafer.

Subsequently, as shown in FIG. 3D, the acoustic matching layer 80 is adhered to the electrode layer positioned on the first main surface of the piezoelectric single crystal wafer, and the acoustic lens is covered thereon to complete the ultrasonic probe according to the present invention. The acoustic matching layer may be one or more layers.

When the ultrasonic transducer is manufactured by the manufacturing process according to the present invention, an effective vibration characteristic is shown, which has advantages such as wide bandwidth and high sensitivity.

The piezoelectric single crystal that can be used in the ultrasonic probe according to the present invention is, for example, a conventional ferroelectric piezoelectric single crystal, for example, preferably PMN-PT including, but not limited to, a material having a composition of Formula 1 below.

x [A] y [B] z [C] -p [P] n [N]

Wherein [A] is lead magnesium niobate [Pb (Mg _1/3 Nb _2/3 ) O ₃ ] or lead zinc niobate [Pb (Zn _1/3 Nb _2/3 ) O ₃ ], [B] is lead titanate [PbTiO ₃ ], [C] is lithium tantalate [LiTaO ₃ ] or lithium niobate [LiNbO ₃ ], and [P] is platinum, gold, silver, palladium and rhodium One metal selected from the group consisting of [N] is an oxide of one metal selected from the group consisting of nickel, cobalt, iron, strontium, scandium, ruthenium, copper and cadmium, and x is 0.65 to 0.98 Number of ranges, y is a number ranging from 0.01 to 0.34, z is a number ranging from 0.01 to 0.1, and p and n are each numbers ranging from 0.01 to 5, respectively.

The piezoelectric single crystal having the composition of Formula 1 may be prepared as disclosed in Korean Patent No. 392754, having a dielectric constant value of 5500 or more at room temperature and a low temperature coefficient in a wide temperature range of -20 to 90 ° C. Has characteristics.

When the ultrasonic probe of the present invention uses a piezoelectric single crystal having the composition of Formula 1 as a piezoelectric element, it may obtain a relative dielectric constant in the range of about 1,000 to 10,000 when polarized. The piezoelectric element composed of the piezoelectric single crystal of Chemical Formula 1 has a larger relative dielectric constant than the piezoelectric element made of PZT-based ceramics, which is commercially available, so that it can be easily matched with a transmission / reception circuit, thereby providing a stray capacity of a cable or a device. The loss caused by capacitance is reduced, and thus a high sensitivity signal can be obtained. In the ultrasonic transmitting / receiving element according to the present invention, the sound velocity emitted from the transmitting / receiving surface having the plane direction (001) is 1,200 to 4,000 m / s (frequency constant: 1,400 to 2,000 Hz.m), and the electromechanical coupling coefficient (k ₃₃ ') is large as 80 to 95%.

The ultrasonic probe of the present invention can be applied to medical ultrasonic diagnostics or military / industrial ultrasonic transducers.

Hereinafter, an Example is given and this invention is demonstrated in detail. However, the following examples do not limit the present invention.

Example

An ultrasonic probe as shown in FIG. 1 was manufactured by the process as shown in FIGS. 2 and 3.

First, a <001> plane piezoelectric single crystal wafer 10 having a thickness of 0.4 to 0.5 mm and a size of 25-20 mm x 15-20 mm is prepared (see FIG. 2A), and the first main surface 10a of the single crystal wafer, The electrode layer 20 "(Cr / Cu / Au) is 1000-2000 micrometers thick through the electron-beam deposition method in the 2nd main surface 10b, the 1st side surface 10c, and the 2nd side surface 10d. 2B. Then, grooves 30 and 30 'were cut out by dicing saws in the electrode layers on the first and second main surfaces 10a and 10b of the piezoelectric single crystal substrate, respectively. 20 " was separated into two electrode layers 20, 20 '(see FIG. 2C). At this time, the grooves 30 and 30 'were formed at positions 1-1.5 mm from the second side surface 10d and the first side surface 10c, respectively, and each groove had a depth of 0.25-0.35 mm.

Subsequently, a backing layer 40 is bonded using an epoxy paste to the electrode layer on the second main surface of the piezoelectric single crystal substrate to the wafer 100 on which the electrode layer is formed, and then the silver epoxy paste 70 is attached. The ground electrode plate was bonded to the first electrode layer 20 located on the first side of the piezoelectric single crystal substrate, and the flexible flexible printed circuit board was bonded to the second electrode layer 20 '. At this time, the signal FPCB was folded and fixed at right angles within the limit not exceeding the electrode separation groove 30.

Subsequently, the acoustic matching layer 80 was adhered to the electrode layer located on the first main surface of the piezoelectric single crystal substrate, and the acoustic lens was covered thereon to complete the ultrasonic probe according to the present invention.

Comparative example

According to the conventional masking method, it is performed in the same manner as in the embodiment, except that the electrode is formed by attaching a masking tape to a portion to be isolated and coating the electrode before removing the electrode, and then removing the masking tape to form an isolation part. To prepare an ultrasonic transducer.

Test Example

According to the present invention, the vibration characteristics when the electrode was formed as in the above Examples and Comparative Examples were measured and compared by resonance and anti-resonance methods, and the results are shown in FIGS. 4A and 4B.

When the vibration characteristics of the wafer in which the electrode isolator is formed according to the conventional method of FIG. 4B can be seen, unwanted vibrations occur (inside dashed lines). On the contrary, when the improved electrode isolator forming method is applied according to the present invention, it can be seen that excess vibration is eliminated as shown in FIG. 4A.

In addition, the characteristics of the transducers manufactured according to the above Examples and Comparative Examples were compared, and the results are shown in Table 1 below.

Relative Sensitivity (dB) -6 dB bandwidth Comparative example 0 85.1 Example 1.5 101.9

As can be seen from the above table, when the electrode isolator is formed by a general masking method, the sensitivity is also lowered and the bandwidth is lower in the final manufactured transducer than in the case of forming the electrode according to the present invention.

Ultrasonic transducer manufacturing method including the electrode structure of the novel structure according to the present invention can provide a stable ultrasonic transducer without generating vibration by using a silver epoxy paste capable of performing electrical bonding at a low temperature.

Simple modifications or changes of the present invention can be easily carried out by those skilled in the art, and all such modifications or changes can be seen to be included in the scope of the present invention.

1 is a perspective view of an ultrasonic probe according to the present invention,

2A to 2C are views illustrating a process of forming an electrode and an electrode separator (groove) on a single crystal wafer in manufacturing an ultrasonic probe according to the present invention.

3A to 3D are views illustrating a manufacturing process of an ultrasonic probe using a wafer having an electrode layer according to the present invention;

4A and 4B are diagrams showing the vibration characteristics of the ultrasonic probe when the electrode is formed according to the Examples and Comparative Examples.

* Explanation of symbols for main parts of the drawings

10: wafer

10a: first principal plane of wafer 10b: second principal plane of wafer

10c: first side of the wafer 10d: second side of the wafer

20 ": electrode layer

20: first electrode layer 20 ': second electrode layer

30: groove as separator on electrode layer 40: back layer

50: grounding electrode plate 60: signal flexible printed circuit board

70: epoxy paste 80: acoustic matching layer

100: wafer on which electrode layer is formed

Claims (10)

(A) a piezoelectric single crystal substrate having a first main surface, a second main surface, a first side surface, and a second side surface, (B) two grooves formed on the first main surface and the second main surface of the piezoelectric single crystal substrate, respectively, spaced apart from the second side surface and the first side surface of the piezoelectric single crystal substrate and extending in the longitudinal direction of the piezoelectric single crystal substrate. (A) a part of the first side and the second main surface of the piezoelectric single crystal substrate and a first electrode layer substantially covering the first main surface, and (b) a part of the second side and the first main surface of the piezoelectric single crystal substrate And a second electrode layer substantially covering the second main surface, (C) a back layer bonded to the electrode layer located on the second main surface of the piezoelectric single crystal substrate, (D) an electrode plate for ground bonded to the first electrode layer on the first side of the piezoelectric single crystal substrate, and (E) An ultrasonic probe comprising a flexible printed circuit board for signaling, the terminal portion of which is folded at right angles and bonded to a second electrode layer in front of a groove located on a first main surface past a second electrode layer on a second side of the piezoelectric single crystal substrate. The method of claim 1, And the groove is formed at an inner side of an adhesive layer for bonding the electrode layer and the ground electrode or the flexible flexible printed circuit board to the signal from the side of the substrate. The method of claim 2, Ultrasonic transducer, characterized in that the groove is formed 1 to 1.5 mm from the side of the substrate. The method of claim 1, Ultrasonic transducer, characterized in that the groove is formed to a depth corresponding to 70 to 80% of the thickness of the wafer. (1) depositing an electrode layer on the first main surface, the second main surface, the first side, and the second side of the piezoelectric single crystal substrate, (2) grooves are formed in the longitudinal direction of the piezoelectric single crystal substrate at positions spaced apart from the second side surface and the first side surface on the first main surface and the electrode layer on the second main surface of the piezoelectric single crystal substrate, respectively, The electrode layer formed in step 1) is separated into a first electrode layer and a second electrode layer, (3) forming a backing layer on the electrode layer located on the second main surface of the piezoelectric single crystal substrate, (4) A grounding electrode plate is bonded to the first electrode layer located on the first side of the piezoelectric single crystal substrate, and the second electrode layer is positioned on the first main surface past the second electrode layer on the second side of the piezoelectric single crystal substrate. A method of manufacturing an ultrasonic probe, comprising bonding a flexible printed circuit board for a signal having a structure in which a distal end is folded at right angles in front of a groove. The method of claim 5, A groove is formed in the groove from the side of the substrate to the inside of the adhesive coating distance for bonding the electrode and the grounding electrode or signal flexible printed circuit board. The method of claim 6, A groove is formed in the inner side of 1 to 1.5 mm from the side of the substrate. The method of claim 6, A method according to claim 1, wherein the adhesive is a silver epoxy paste. The method of claim 5, The groove is formed in a depth corresponding to 70 to 80% of the thickness of the wafer. The method of claim 5, A groove is formed by using a dicing saw.