JPH08223695A - Ultrasonic probe and its production - Google Patents

Abstract

PURPOSE: To reduce the deterioration with age at the junction parts among an ultrasonic oscillator, an acoustic lens and an ultrasonic absorbing material and also to secure the excellent acoustic characteristic. CONSTITUTION: An ultrasonic oscillator 1 and an acoustic lens 5 made of quarz are set on a pressure jig and both junction faces are closely put together with pressure after the pollution layers such as the oxides, etc., are eliminated on the junction faces by means of a beam source. Thus the oscillator 1 and the lens 5 can be put together with pressure. In the same way, the oscillator 1 and an ultrasonic absorbing member 7 are put together with pressure. An Au/Cr evaporation film 4 is formed on one of both sides of the lens 5, and the films 4 (metallic films for formation of electrode 2 and 3) are formed on both sides of the oscillator 1. Therefore, the oscillator 1, the lens 5 and the member 7 can be joined together with pressure. In such a constitution, it is possible to obtain an ultrasonic probe which has the excellent acoustic characteristic that never changes for a long period of time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bonding structure between an ultrasonic oscillator, an acoustic lens and an ultrasonic absorber in an ultrasonic probe and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, for assembling an ultrasonic probe,
As a method of joining the ultrasonic oscillator, the acoustic lens, and the ultrasonic absorber, a method using an organic adhesive such as an epoxy resin has been mainly adopted.

However, when an electrically insulating organic adhesive such as an epoxy resin is used to bond the ultrasonic oscillator to the acoustic lens and the ultrasonic absorber, some problems have been recognized. First, since the epoxy resin adhesive used for joining changes with time, there is a possibility that the acoustic characteristics of the ultrasonic probe may deteriorate over time, and there is a problem that the reliability of measurement is impaired.

In general, the difference in acoustic impedance between the epoxy resin-based organic adhesive, the ultrasonic oscillator and the acoustic lens is extremely large. When the lenses are bonded, the organic adhesive forms an acoustic boundary layer, which results in the reflection of ultrasonic waves. Therefore, there is also a problem that the ultrasonic wave does not sufficiently propagate from the ultrasonic oscillator to the acoustic lens, and good acoustic characteristics are not exhibited.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a structure of an ultrasonic probe which has a small change with time in the joint between the ultrasonic oscillator and the acoustic lens and which has good acoustic characteristics. It is to provide the manufacturing method.

[0006]

The above object is to join an ultrasonic oscillator, an ultrasonic absorber, and an acoustic lens by physical pressure contact without using an electrical insulator, and to attach the ultrasonic oscillator and the acoustic lens. For joining, it is achieved by irradiating the joining surface with an ion beam or an atom beam in a vacuum and then performing pressure welding. In particular, in the present invention, quartz is used as the material of the acoustic lens, and Au is bonded to the joint surface of the acoustic lens with the ultrasonic oscillator.
/ Cr vapor deposition film is provided.

[0007]

By irradiating the bonding surface of the ultrasonic oscillator and the acoustic lens with an ion beam or an atom beam in a vacuum, the contaminated layer such as an oxide film or water adhering to the bonding surface is removed. As a result, the joint surface becomes a clean and active surface, and if pressure is applied to bring it into close contact, an extremely good pressure-welded joint is formed.

The term "pressure welding" used throughout this specification means that the surfaces to be joined are cleaned and brought into contact with each other at a high pressure to cause diffusion on the surfaces to join them. .

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in more detail below with reference to the drawings.

FIG. 1 is a schematic sectional view showing the structure of an ultrasonic probe according to the present invention. The bonding surface of the acoustic lens 5 to be bonded to the ultrasonic oscillator 1 made of a piezoelectric element is previously Au / C.
An r vapor deposition film 4 is provided. Other metal vapor deposition films can also be used. Since Au is exposed on the surface of the Au / Cr film, it is chemically stable. This Au / Cr film can be formed by a vapor deposition method such as sputtering or vacuum evaporation. Such film forming methods are known to those skilled in the art. First, a Cr film is formed and A is formed on it.
A u film is formed. The Cr film promotes the bonding between the lens and the metal. The film thickness of the Au / Cr vapor deposition film 4 is not particularly limited depending on the roughness of the vapor deposition surface and the like, but in general, it is preferably 3 μm or more. If it is less than 3 μm, a sufficient bonding effect may not be obtained. On the other hand, the upper limit of the film thickness of the Au / Cr film depends on the thickness of the ultrasonic oscillator used, but is preferably about 1/10 of the thickness of the ultrasonic oscillator. For example, 2
If it is 5 MHz, the upper limit is about 8 μm. If the Au / Cr vapor deposition film 4 thicker than this is used, inconveniences such as interface reflection waves may occur, which is not preferable.

The upper electrode 2 is provided on one surface of the ultrasonic oscillator 1.
And the lower electrode 3 is provided on the other surface. The upper electrode 2 can be formed of, for example, an Au / Cr film. Other metals can of course be used. The method of forming the upper electrode is not particularly limited, but the upper electrode can be formed by a method such as vapor deposition such as sputtering or vacuum deposition. The thickness of the upper electrode 2 is not particularly limited, but in general, it is preferably within the range of 3000 Å to 5000 Å. If it is less than 3000 Å, the surface roughness of the ultrasonic oscillator 1 causes a disadvantage such as the absence of the upper electrode 2, and if it exceeds 5000 Å, there is no particular problem, but it is uneconomical. Further, the lower electrode 3 can be formed of an Au / Cr film, like the upper electrode 2. Other metals can of course be used. The method of forming the lower electrode 3 is not particularly limited, but the lower electrode 3 can be formed by a method such as vapor deposition such as sputtering or vacuum deposition. The thickness of the lower electrode 3 is not particularly limited, but is generally 3000 Å to 500
It is preferably in the range of 0Å. If it is less than 3000 Å, the surface roughness of the ultrasonic oscillator 1 causes a disadvantage such as the absence of the upper electrode 3, and 500
Above 0Å there is no particular problem, but it is only uneconomical. Since the Au / Cr vapor deposition film is used as the material for forming the lower electrode 3, the Au / Cr vapor deposition film 4 of the acoustic lens 5 and the Au-Au junction at the time of joining are chemically stable, which is preferable.

The acoustic lens 5 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, since only the Au / Cr film exists between the acoustic lens 5 and the ultrasonic oscillator 1, there is almost no generation of reflected waves due to this film during oscillation, and good acoustic characteristics can be obtained.

The piezoelectric element forming the ultrasonic oscillator 1 is PZ.
T (Pb (Zr, Ti) 0 3 based ceramic) or Pb
TiO ₃ (lead titanate) or the like can be used. Such materials are well known to those of ordinary skill in the art.

An electrode connecting lead wire 6 is connected to one end of the Au / Cr vapor deposition film 4 of the acoustic lens 5. This connection can be made by using, for example, a silver paste or a room temperature curable conductive resin.

FIG. 2 is a schematic view illustrating one step of the method for manufacturing an ultrasonic probe of the present invention. In FIG. 2, reference numeral 1
Is an ultrasonic oscillator made of a piezoelectric element, 5 is an acoustic lens made of quartz, 13a and 13b are beam sources that generate atom beams, 14a and 14b are pressure jigs, and these are vacuum processing chambers. It is located within 20. A duct 22 connected to an evacuation means (not shown) is provided at an appropriate position in the vacuum processing chamber 20.

First, the ultrasonic oscillator 1 and the acoustic lens 5 are mounted on the pressing jigs 14a and 14b, respectively, and the atmosphere in the vacuum processing chamber 20 is evacuated from the duct 22. Next, an atom beam of argon is generated from the beam sources 13a and 13b, and the beams are irradiated to the joint surfaces of the ultrasonic oscillator 1 and the acoustic lens 5, respectively, and a contamination layer (for example, natural oxidation) existing on these joint surfaces is irradiated. Substance or physically adsorbed water). Since the joint surface becomes a clean and active surface by this operation, the joint surfaces of both members are brought into close contact with each other by using the pressure jigs 14a and 14b, and the pressure is continuously applied for a predetermined time.
Diffusion occurs at the joint surfaces of both members, and the ultrasonic oscillator 1 and the acoustic lens 2 can be pressure-bonded to each other. The pressure jig is for performing pressure contact bonding between the respective members, and can be configured by a hydraulic cylinder or the like.

When the pressure welding of the ultrasonic oscillator 1 and the acoustic lens 5 is completed, the ultrasonic oscillator 1 and the pressing jig 14a are separated. Then, as shown in FIG. 3, the pressing jig 14a
The ultrasonic absorber 7 is attached to. While maintaining the vacuum pressure during the pressure contact of the ultrasonic oscillator 1, the other bonding surface of the ultrasonic oscillator 1 not bonded to the acoustic lens 5 and the ultrasonic absorber 7
The bonding surface of the is irradiated with the atom beam of argon generated from the beam sources 13a and 13b, and the contamination layer (for example, natural oxide or physically adsorbed water) existing on these bonding surfaces.
Is removed. Since the joint surface becomes a clean and active surface by this operation, the joint surfaces of both members are brought into close contact with each other by using the pressure jigs 14a and 14b, and pressure is continued for a predetermined time, so that the joint surfaces of both members are diffused. Then, the ultrasonic oscillator 1 and the ultrasonic absorber 7 can be pressure-bonded to each other. Thus, the acoustic lens 5 and the ultrasonic absorbing material 7 can be integrally pressure-bonded to each other with the ultrasonic oscillator 1 interposed therebetween without using a conventional epoxy resin-based organic adhesive. it can.

In the present invention, an ion beam or an atom beam is used as a means for cleaning the bonding surfaces of the ultrasonic oscillator 1, the acoustic lens 5 and the ultrasonic absorbing material 7, because the vacuum state is used. This is for forming an active surface and for bonding in the same chamber while maintaining the state. Plasma, an organic solvent, ultrapure water, or the like is used as the surface cleaning means, but it is most preferable to use an ion beam or an atom beam in order to perform surface activation and bonding in the same chamber. As an ion beam or atom beam,
For example, a beam of argon or the like can be preferably used.

The vacuum processing chamber 20 is used in order to efficiently perform the cleaning process by the ion beam or atom beam. The vacuum pressure suitable for this purpose is not particularly limited, but is generally preferably about 10 ^-6 Torr. When the vacuum pressure in the vacuum processing chamber 20 is lower than this, recontamination of the joint surface cannot be prevented, and when the vacuum pressure is higher than this, the effect of the cleaning process itself is further enhanced. It is uneconomical because it cannot happen.

As the beam sources 13a and 13b, for example, a device 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 atom beam required for the cleaning treatment 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 the pressure welding between the members is obtained. As a general index, the output of ion beam or atom beam is 1
It is preferably about keV, 25 mA. Output is 1
If the keV is less than 25 mA, the cleaning of the joint surface may be insufficient. On the other hand, the output is 1 keV, 25 m
If it exceeds A, it is not preferable because it causes inconvenience such as formation of large holes in the joint surface. Also,
The beam irradiation time is not particularly limited as long as it is long enough for cleaning the bonding surface. In order to obtain the desired degree of cleanliness of the joint 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 longer if a low power beam is used. As a general index, when using a beam having an output of about 1 keV and 25 mA, the irradiation time is about 600 seconds.

The pressurizing pressure and the pressurizing time of each member by the pressing jigs 14a and 14b are not particularly limited as long as they are the size and length necessary and sufficient for forming the pressure welding 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 applied is too high, the quartz acoustic lens 5 may be damaged. Generally, the upper limit of the pressurizing pressure is determined by the objects to be joined.

In this embodiment, the material to be joined, that is, the piezoelectric element 1,
Although both the acoustic lens 5 and the ultrasonic absorber 7 are bonded at room temperature, if the materials to be bonded are heated using a heater or the like to raise the temperature of the bonding surface to a certain range and then bond, the bonding strength is further improved. To rise.

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

Next, the assembly structure of the ultrasonic probe manufactured by using the present invention will be described with reference to FIG. In FIG. 4, reference numeral 1 is an ultrasonic oscillator, 5 is an acoustic lens, 6 is a lower electrode connecting lead wire, 7 is an ultrasonic absorbing material, 8 is an upper electrode connecting lead wire, 9 is a filling material, and 10 is a protective material. A case and 11 are terminals, respectively. The basic components themselves are almost the same as the ultrasonic probe using the conventional epoxy resin adhesive. For example, as described above, the ultrasonic oscillator 1 can use a piezoelectric element and PT (lead titanate) that are well known to those skilled in the art. Quartz is used as the acoustic lens 5. Lead, tin, or the like can be used as the ultrasonic absorber 7. The ultrasonic absorber has a function of suppressing ultrasonic vibration. The lower electrode lead wire 6 is connected to the inner wall surface of the protective case 10. The upper electrode connecting lead wire 8 is connected to the upper surface of the ultrasonic absorber 7. It may be connected to the lower surface of the ultrasonic absorber. The lead wire 8 is insulated by the insulating material 12 and taken out of the protective case 10. As the filler 9, for example, an epoxy resin or the like can be used. The protective case 10 is made of metal and also serves as a conductor of the acoustic lens side electrode.

Next, the operation of the ultrasonic probe of the present invention will be described. When a pulse voltage is applied to the ultrasonic oscillator 1 via the terminal 11 by a pulse voltage generator (not shown),
Ultrasonic pulse is generated. The generated ultrasonic waves are incident on a subject (not shown) via the acoustic lens 5 to perform ultrasonic flaw detection.

Table 1 below shows a typical piezoelectric element (PbTiO ₃ -based ceramics) as a material of an ultrasonic oscillator, quartz used as a material of an acoustic lens, and an epoxy resin typical as a material of an organic adhesive. Indicates acoustic impedance.

[0027]

[Table 1]

From Table 1 above, it can be seen that the acoustic impedance of the epoxy resin is smaller than that of the piezoelectric element and quartz.

By the way, assuming that the acoustic impedances of two substances bonded on a plane are Z ₁ and Z ₂ , respectively, the sound pressure reflectance r at the bonding interface between them is expressed by the following equation. _{r = (Z 2 -Z 1)} / (Z 2 + Z 1) ... (1)

For example, when a piezoelectric element and an epoxy resin are bonded, substituting the numerical value of the acoustic impedance in Table 1 into the equation (1), r = -0.81 (where-(minus) is the phase Which means inversion). That is, it is understood that 81% of the ultrasonic waves generated by the piezoelectric element are reflected at the bonding interface, so that the ultrasonic waves do not propagate efficiently to the acoustic lens.

On the other hand, when the piezoelectric element and quartz are directly pressure-bonded to each other, r = -0.44 is obtained from the above equation (1), and the reflection of ultrasonic waves at the bonding interface is reduced.
Ultrasonic waves generated by the piezoelectric element can be efficiently propagated to the acoustic lens.

By vapor-depositing Au / Cr on the quartz acoustic lens, the sound absorbing agent Pb can be bonded stably and evenly, so that damping can be made effective. When the pulse wave is transmitted, the number of received waves is as short as a few wavelengths. However, when an organic adhesive such as an epoxy resin is used as the joining means, the joining surface may be uneven. In addition, it is difficult to set the thickness to about Au / Cr vapor deposition film. As a result, the wave number is 4-7
It will be as long as the wavelength.

[0033]

The ultrasonic probe by the pressure welding method of the present invention does not have an acoustic boundary layer such as an adhesive between the ultrasonic oscillator and the acoustic lens, and therefore exhibits good acoustic characteristics. Further, according to the present invention, since it is possible to perform strong pressure welding without using an organic adhesive that may change with time during joining, an ultrasonic probe whose performance does not change for a long time is provided. can do.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an example of an ultrasonic probe of the present invention.

FIG. 2 is a schematic view illustrating one step of the method for manufacturing an ultrasonic probe of the present invention.

FIG. 3 is a schematic view illustrating another step of the method for manufacturing an ultrasonic probe of the present invention.

FIG. 4 is a schematic cross-sectional view of an example of the assembly structure of the ultrasonic probe of the present invention.

[Explanation of symbols]

 1 Ultrasonic Oscillator 2 Upper Electrode 3 Lower Electrode 4 Au / Cr Evaporated Film 5 Acoustic Lens 6 Lower Electrode Connecting Lead Wire 7 Ultrasonic Absorber 8 Upper Electrode Connecting Lead Wire 9 Filling Material 10 Protective Case 13a, 13b Beam Source 14a, 14b Pressure jig 20 Vacuum processing chamber 22 Exhaust duct

Claims (6)

[Claims] 1. An ultrasonic absorber, an ultrasonic absorber having an electrode-forming metal film on both sides, and an acoustic lens are pressure-bonded to each other with an ultrasonic oscillator interposed therebetween. A characteristic ultrasonic probe. 2. The ultrasonic probe according to claim 1, wherein the acoustic lens is made of quartz, and an Au / Cr vapor deposition film is provided on a bonding surface of the acoustic lens with the ultrasonic oscillator. 3. The ultrasonic probe according to claim 1, wherein the electrode forming metal film is an Au / Cr film, and the ultrasonic absorbing material is lead or tin. 4. A joint surface between an ultrasonic oscillator and an acoustic lens,
Ions in vacuum on the joint surface of the acoustic lens with the ultrasonic oscillator, the joint surface of the ultrasonic oscillator with the ultrasonic absorber, and the joint surface of the ultrasonic absorber with the ultrasonic oscillator. Beam or atom beam is applied, and the ultrasonic absorber, the ultrasonic oscillator, and the acoustic lens are brought into close contact with each other while being pressed, and the ultrasonic oscillator is sandwiched between the ultrasonic absorber and the ultrasonic absorber. A method for manufacturing an ultrasonic probe, characterized in that a sound wave oscillator and an acoustic lens are pressure-bonded to each other. 5. The acoustic lens is made of quartz, and an Au / Cr vapor deposition film is provided on a bonding surface of the acoustic lens with the ultrasonic oscillator, and the ultrasonic oscillator has metal films for electrode formation on both surfaces thereof. The method of claim 4, wherein the ultrasonic absorber comprises lead or tin. 6. In the pressure welding of the ultrasonic absorber, the ultrasonic oscillator and the acoustic lens, the ultrasonic oscillator and the ultrasonic absorber are pressed after the ultrasonic oscillator and the acoustic lens are pressure welded to each other. The method according to claim 4, wherein the material is pressure-welded.