JPH11304775A - Ultrasonic probe and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic probe which can sufficiently exhibit its performance without causing the deterioration of its piezoelectric element. SOLUTION: An ultrasonic probe is constituted in such a way that a piezoelectric element 1 carrying metallic films for forming electrodes on both surfaces is joined with an acoustic lens 10 carrying a conductive metallic thin film 4 on one surface, by press-contacting the surface of the element 1 carrying the thin film for forming a lower electrode 3 with the surface of the lens 10 carrying the metallic thin film 4, and a damper material 6 is bonded to the surface of the element 1 carrying the metallic film for forming an upper electrode 2. Then the joined body is housed in a housing 11 made of a conductive metal, and the space formed of the housing 11, acoustic lens 10, piezoelectric element 1, and damper material 6 is filled up with a synthetic resin material containing conductive metal power. Finally, the metal powder contained in the resin material is deposited in the corner sections demarcated by the upper surface of the thin film 4 of the lens 10 on the outer peripheral edge side of the film 4 and the internal surface of the housing 11 by the agency of a centrifugal force, so as to electrically connect the lower electrode 3 to the housing 11 by rotating the housing 11 along the axial line of the housing 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic probe for irradiating a sample with ultrasonic waves to detect a defect on the surface or inside of the sample, and a method for manufacturing the same. More specifically, the present invention relates to an ultrasonic probe capable of sufficiently exhibiting performance without causing deterioration of a piezoelectric element, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, an ultrasonic inspection apparatus has been used for nondestructive inspection in various fields. An ultrasonic probe used in such an ultrasonic inspection device has a piezoelectric element. An ultrasonic beam is generated by applying a voltage to the electrodes provided on both sides of the piezoelectric element, the beam is irradiated into the object to be inspected, and an echo reflected from the object to be inspected is received by the piezoelectric element. The structure in the test object is analyzed by converting it into an electric signal and performing signal processing.

[0003] An ultrasonic inspection apparatus can inspect the internal structure of an inspected object without applying any physical or mechanical deformation, and is extremely safe and does not require dangerous means such as radiation. It is an effective non-destructive inspection device.

Various types of ultrasonic probes have been used in ultrasonic inspection apparatuses. For example, JP-A-1-291
No. 844 discloses an ultrasonic wave in which a front surface electrode and a back surface electrode are provided on both surfaces of a piezoelectric element made of a piezoelectric material such as PZT, and a damping layer formed by mixing tungsten powder with epoxy-based synthetic resin is bonded to the back surface electrode. A probe is disclosed. In this ultrasonic probe, a conductor is directly soldered to the front electrode and the back electrode of the piezoelectric element. For this reason, the electrical characteristics of the piezoelectric element are degraded due to a load generated by the curing shrinkage of the solder; thermal cracks or thermal strains due to soldering cause micro cracks in the piezoelectric element; workability due to soldering is poor, Increases manufacturing cost; heating causes part of the piezoelectric element to be depolarized by soldering; or mass concentration occurs in part of the piezoelectric element due to soldering, and characteristics change depending on the soldering position. It is known that inconveniences occur.

An ultrasonic probe in which the disadvantages of the soldering ultrasonic probe are improved is disclosed in Japanese Patent Application Laid-Open No. 5-227594. In this improved ultrasonic probe, vacuum deposition is performed on the surface of the damping layer, and the surface and the upper electrode of the piezoelectric element are joined via a conductive adhesive. Further, the upper housing and the lower housing are joined via an insulating layer.

In the ultrasonic probe disclosed in Japanese Patent Application Laid-Open No. 5-227594, an electrode is formed by vacuum evaporation on the surface of a damping layer formed by mixing a tungsten powder with a synthetic resin. Since the surface of the damping layer becomes uneven due to the vacuum deposition, it is difficult to uniformly join the damping layer to the back surface of the piezoelectric element via a conductive adhesive. Also, the higher the frequency, the higher the frequency of the irregularities on the surface, which may cause disturbance (tailing) of the oscillation waveform.

[0007]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an ultrasonic probe which can sufficiently exhibit its performance without causing deterioration of the piezoelectric element.

[0008]

An object of the present invention is to provide an acoustic lens having a conductive metal thin film on one surface and a piezoelectric element having an electrode forming metal film on both surfaces on the surface having the conductive metal thin film. The lower electrode is joined by pressure contact on the metal film surface side, and the damper material is joined to the upper electrode metal film surface of the piezoelectric element, and the joined body is housed in a conductive metal housing. And a space formed by the acoustic lens, the piezoelectric element and the damper material is filled with a synthetic resin material having a conductive metal powder, and the housing is rotated along the axis of the housing, thereby applying a centrifugal force. Depositing the conductive metal powder in the synthetic resin material on the corner defined by the outer peripheral upper surface of the conductive metal thin film of the acoustic lens and the inner wall surface of the housing; It is solved by connecting electrically the electrode and the housing.

[0009]

FIG. 1 is a schematic partial sectional view of an assembling structure of an ultrasonic probe according to the present invention. In FIG. 1, a piezoelectric element 1 and an acoustic lens 10 are described in Japanese Patent Application Laid-Open No. H8-223695.
No. 6,009,045, the bonding is performed without an adhesive by a pressure bonding method as disclosed in Japanese Patent Application Laid-Open Publication No. H11-157,036. The press-contact assembly of the piezoelectric element 1 and the acoustic lens 10 is inserted into the housing 11, and the outer peripheral surface side of the acoustic lens 10 and the inner wall surface side of the housing 11 are fixed with an adhesive or the like. After that, the damper material 6 is formed on the piezoelectric element 1. As the damper material 6 here, a material obtained by mixing a tungsten powder with a synthetic resin is used.

After the damper member 6 is solidified, the synthetic resin and the tungsten powder are similarly put around the damper member 6 and rotated around the center axis of the housing 11. Due to the centrifugal force caused by the rotation, the tungsten powder is deposited on the corner between the upper part of the acoustic lens 10 and the inner wall surface of the housing 11 to form the conduction part 12.

An upper electrode 2 such as, for example, an Au / Cr film exists between the piezoelectric element 1 and the damper material 6, and an Au / C film, for example, exists between the piezoelectric element 1 and the acoustic lens 10.
There is a lower electrode 3 such as an r film. In order to ensure conduction between the lower electrode 3 and the housing 11, an Au / Cr vapor-deposited film 4 or the like is provided on the upper surface of the acoustic lens 10. Therefore, the lower electrode 3 and the acoustic lens 10
/ Cr film 4. The conductive portion 12 is formed between the lower electrode 3 and the housing 11 because the tungsten powder contacts the deposited film 4.

A signal lead wire 7 is connected to the upper electrode 2 by a conductive paste 5.
The GND lead 9 can be taken out from the upper part of the lead wire by the solder part 8.

With such a configuration, the ultrasonic probe according to the present invention can apply a voltage between the signal lead-out line 7 and the GND lead-out line 9 without damaging the piezoelectric element 1 and can stably operate. And sufficient performance can be obtained.

The rotation speed for depositing the tungsten powder on the corner between the upper part of the acoustic lens 10 and the inner wall surface of the housing 11 is not particularly limited, but is generally 30.
It is preferable to be within the range of 00 rpm to 3600 rpm. If the rotation speed is less than 3000 rpm, the tungsten powder may not be deposited on the corner between the upper part of the acoustic lens 10 and the inner wall surface of the housing 11 irrespective of the rotation time. On the other hand, when the rotation speed is 36
If it exceeds 00 rpm, there is no particular problem, but it is only uneconomical because it only costs electricity. Generally, the rotation speed and the rotation time have an inverse correlation. That is, the higher the rotation speed, the shorter the rotation time required for depositing the tungsten powder. Conversely, when the rotation speed is low, the rotation time required for depositing the tungsten powder increases.

As the synthetic resin, an epoxy resin, an acrylic resin or the like can be used. The property of the synthetic resin is a viscous liquid or the like. After the conductive portion is formed by centrifugal separation, the synthetic resin is solidified by a polymerization reaction. As a synthetic resin such as an epoxy resin or an acrylic resin, a mixture of two liquids can be used. That is, it is a two-liquid mixed system of the main agent and the curing agent. The weight ratio between the main agent and the curing agent is, for example, about 10: 1.

The amount of the tungsten powder mixed with the synthetic resin is not particularly limited. What is necessary is just the compounding quantity necessary and sufficient to form the conduction part 12 reliably. Generally, the amount of the tungsten powder is preferably in the range of 60 wt% to 70 wt%. 60wt% of tungsten powder
If it is less than 10 mm, it is difficult to reliably form the conductive portion 12.
On the other hand, when the blending amount of the tungsten powder exceeds 70 wt%,
Although the formation of the conductive portion 12 is easy, it is uneconomical only by adding a tag stainless steel.

As a metal for forming the conductive portion 12, a conductive heavy metal such as lead can be used in addition to tungsten. Tungsten is preferred because it has a large specific gravity and is chemically stable.

FIG. 2 is a schematic sectional view of the piezoelectric element 1. As described above, for example, an Au / Cr film for the upper electrode 2 is provided on the upper surface of the piezoelectric element 1, and an Au / Cr film for the lower electrode 3 is provided on the lower surface. Other conductive metal films (for example, Ag films) can also be used. Au
The / Cr film can be formed by a vapor deposition method such as vacuum evaporation or sputtering. Such deposition methods are known to those skilled in the art. Although the thickness of the Au / Cr film is not particularly limited by the roughness of the deposition surface, it is generally preferable that the thickness be in the range of 3000 to 5000 angstroms (hereinafter indicated by the symbol “A”).
If it is less than 3000A, due to the surface roughness of the piezoelectric element 1,
Inconveniences such as the absence of the upper electrode 2 occur,
If it exceeds 5000A, there is no particular problem, but it is only uneconomical. The lower electrode 3 is made of Au similarly to the upper electrode 2.
/ Cr film. The thickness of the lower electrode 3 is not particularly limited, but is generally 3000 to 5000.
It is preferably within the range of A. If it is less than 3000 A, the surface roughness of the piezoelectric element 1 causes inconveniences such as the absence of the lower electrode 3.
There is no particular problem in super, but it is only uneconomical.

Further, on the lower surface of the lower electrode 3 (that is, the surface to be bonded to the acoustic lens 10), a lead vapor-deposited film 14 is provided to promote the pressure bonding with the acoustic lens 10.
The lead deposition film can be formed by a vapor deposition method such as vacuum deposition or sputtering. Such deposition methods are known to those skilled in the art. The thickness depends on the surface roughness of the piezoelectric element 1, but is about 3 μm in the 25 to 50 MHz class. Also, at 15 MHz or less,
It is about μm. The lead vapor deposition film 14 is used to fill the surface roughness of the piezoelectric element 1 and to promote pressure bonding. Therefore, the lower limit of the thickness of the lead vapor-deposited film 14 may be any value that is necessary and sufficient to achieve this purpose. Such a lower limit can be easily determined by those skilled in the art. In addition to the lead deposition film, an indium / lead (In / Pb) alloy or the like can be used in the same manner.

The lead vapor deposition film 14 and A on the acoustic lens 10 side
When the u / Cr vapor-deposited film 4 is brought into pressure contact, metal diffusion occurs between the two films, and they are joined. The Au / Cr evaporated film 4 on the acoustic lens 10 side can be formed by a vapor deposition method such as vacuum evaporation or sputtering. Such deposition methods are known to those skilled in the art. Au / Cr deposited film 4
Is not particularly limited, but is generally from 0.3 μm to
It is preferable that it is within the range of 0.5 μm. 0.3 μm
If it is less than 10 mm, there is a possibility that inconvenience may occur in the pressure welding with the piezoelectric element 1. On the other hand, if it exceeds 0.5 μm, there is no particular problem, but it is only uneconomical.

The acoustic lens 10 is made of quartz. Quartz is chemically very stable and has excellent corrosion resistance. Therefore, the problem of corrosion that occurs in the case of a metallic acoustic lens does not occur at all. Further, an Au / Cr film, a lead film, and an Au / Cr film exist between the acoustic lens 10 and the piezoelectric element 1, but there is almost no generation of a reflected wave due to this film at the time of oscillation and good acoustic characteristics. Is obtained.

The piezoelectric element 1 is made of PZT (Pb (Zr, Ti)
0 ₃ based ceramic) or PbTiO ₃ (lead titanate) or the like can be used. Such materials are well-known to those skilled in the art.

FIG. 3 is a schematic view of a step of pressing and joining the piezoelectric element 1 and the acoustic lens 10. In FIG. 3, reference numeral 1 denotes a piezoelectric element (not shown, but this piezoelectric element has an upper electrode 2 and a lower electrode 3 on the upper and lower surfaces, respectively, as shown in FIG. Further has a lead vapor-deposited film 14), 10 is an acoustic lens made of quartz, 33a and 33b are beam sources for generating an atom beam, 34a and 34b are pressing jigs, and these are inside the vacuum processing chamber 30. Are located in At an appropriate place in the vacuum processing chamber 30, there is provided a duct 32 connected to a vacuum evacuation means (not shown).

First, the piezoelectric element 1 and the acoustic lens 10 are mounted on the pressing jigs 34a and 34b, respectively, and the atmosphere in the vacuum processing chamber 30 is evacuated from the duct 32. Next, an atom beam of argon is generated from the beam sources 33a and 33b, and the beam is irradiated on the bonding surfaces of the piezoelectric element 1 and the acoustic lens 10, respectively, and a contaminant layer (for example, native oxide or Physisorbed water). Since the bonding surface becomes a clean and active surface by this operation, the bonding surfaces of the two members are brought into close contact with each other using the pressing jigs 34a and 34b, and the diffusion is performed at the bonding surface of the two members by continuing to pressurize for a predetermined time. Happens, the piezoelectric element 1 and the acoustic lens 1
0 can be press-welded. The pressing jig is for performing pressure welding between the members, and can be constituted by a hydraulic cylinder or the like.

In the present invention, the piezoelectric element 1 and the acoustic lens 10
An ion beam or an atom beam is used as a means for cleaning each bonding surface of the above, because an active surface is created in a vacuum state, and bonding is performed in the same chamber while maintaining the state. . As the surface cleaning means, there are plasma, organic solvent, ultrapure water and the like, but it is most preferable to use an ion beam or an atom beam to perform the surface activation and the bonding in the same chamber. As the ion beam or the atom beam, for example, a beam such as argon can be suitably used.

The reason why the vacuum processing chamber 30 is used is to efficiently perform a cleaning process using an ion beam or an atom beam. The vacuum pressure suitable for this purpose is not particularly limited, but is generally preferably about 10 ^-6 Torr. If the vacuum pressure in the vacuum processing chamber 30 is lower than this, re-contamination of the bonding surface is not prevented, and if the vacuum pressure is higher than this, the effect of the cleaning process itself is further enhanced. It is simply uneconomical because it must not be done.

As the beam sources 33a and 33b, for example, devices known to those skilled in the art such as a beam gun commercially available from Atomtech can be used. The output of the ion beam or the atom beam required for the cleaning process of the bonding surface is not particularly limited. Any output may be used as long as the degree of cleanliness necessary and sufficient to establish pressure welding between members is obtained. As a general index, the output of the ion beam or atom beam is 1
KeV, preferably about 25 mA. Output is 1
If the keV is less than 25 mA, the cleaning of the bonding surface may be insufficient. On the other hand, the output is 1 keV, 25 m
It is not preferable to greatly exceed A because disadvantages such as formation of large holes or the like in the joint surface occur. Also,
The beam irradiation time is not particularly limited as long as it is long enough to clean the bonding surface. In order to obtain a desired degree of cleaning of the bonding surface, the beam output and the beam irradiation time have an inverse relationship. For example, if you use a high power beam,
The irradiation time is short, while the irradiation time is long if a low power beam is used. When a beam having an output of about 1 keV and about 25 mA is used as a general index, the irradiation time is about 600 seconds.

The pressing pressure and pressing time of each member by the pressing jigs 34a and 34b are not particularly limited, as long as they are large and long enough to form a pressure-welded joint between the members. Generally, when using a pressurizing pressure of 12.5 MPa or more, the pressurizing time is about 30 seconds. If the pressure is too high, the quartz acoustic lens 5 may be damaged. Generally, the upper limit of the pressurizing pressure is determined by the workpiece.

The piezoelectric element 1 and the acoustic lens 10 can be joined at room temperature. However, if the material to be joined is heated by using a heater or the like and the temperature of the joining surface is raised to a certain range before joining, the joining strength is increased. Rises further.

The bonding can be performed in a vacuum.
After the irradiation with the atom beam, the bonding may be performed after the atmosphere is filled with an inert gas such as argon or nitrogen. Forming an inert gas atmosphere can prevent reoxidation and recontamination of the member.

[0031]

As described above, according to the present invention,
Since there is no change over time in the joint with the piezoelectric element and no damage is given to the piezoelectric element, the performance of the piezoelectric element can be sufficiently brought out and a stable state can be maintained.
Therefore, the quality of the ultrasonic search image can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic partial sectional view of an assembling structure of an ultrasonic probe according to the present invention.

FIG. 2 is a schematic sectional view of a piezoelectric element.

FIG. 3 is a schematic view of a step of pressing and joining a piezoelectric element and an acoustic lens.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Piezoelectric element 2 Upper electrode 3 Lower electrode 4 Gold (Au) vapor deposition film 5 Conductive paste 6 Damper material 7 Signal lead wire 8 Solder part 9 GND lead wire 10 Acoustic lens 11 Housing 12 Conductive part 13 Epoxy resin

Claims (4)

[Claims] 1. An acoustic lens having a conductive metal thin film on at least one surface in a metal housing, a piezoelectric element having an electrode forming metal film on both surfaces, and a damper material, wherein the acoustic lens is An ultrasonic probe, on the side having the conductive metal thin film, which is pressure-bonded to a piezoelectric element having an electrode-forming metal film on both sides, wherein an outer peripheral edge of the conductive metal thin film of the acoustic lens is provided; An ultrasonic probe, wherein an upper surface and the inner wall surface of the housing are electrically connected along a peripheral edge by a synthetic resin layer having a conductive metal deposition portion. 2. The ultrasonic probe according to claim 1, wherein the conductive metal deposition portion is made of tungsten. 3. An acoustic lens having a conductive metal thin film on one surface, a piezoelectric element having an electrode forming metal film on both surfaces on the surface side having the conductive metal thin film, and a metal film serving as a lower electrode thereof. Pressure bonding on the surface side, a damper material on the metal film surface side to be the upper electrode of the piezoelectric element, and this joined body is accommodated in a conductive metal housing, and the housing and the acoustic lens, the piezoelectric element, A space formed by the damper material is filled with a synthetic resin material having a conductive metal powder, and the housing is rotated along an axis of the housing, and the conductive resin in the synthetic resin material is acted on by centrifugal force. Conductive metal powder is deposited on a corner defined by the upper surface of the outer peripheral edge of the conductive metal thin film of the acoustic lens and the inner wall surface of the housing, thereby electrically connecting the lower electrode and the housing. A method for producing an ultrasonic probe, comprising: 4. The method of claim 3, wherein said conductive metal deposit comprises tungsten.