Acoustic laminate, ultrasonic probe, manufacturing method for acoustic laminate, and manufacturing method for ultrasonic probe

Abstract

To achieve stable conduction while bonding a piezoelectric body to an acoustic matching layer using a thin film.SOLUTION: An acoustic laminate has a backing, a flexible printed circuit (FPC), and a piezoelectric body and an acoustic matching layer each of which is coated with a metal layer at least on the lamination surface. The acoustic matching layer and the piezoelectric body are bonded to each other using a bonding layer formed from a low-melting-point metal. The low-melting-point metal is suitably 58%Bi-42%Sn.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] SUMMARY OF THE DISCLOSURE The embodiments disclosed in this specification and the drawings relate to acoustic stacks, ultrasonic probes, methods of making acoustic stacks, and methods of making ultrasonic probes. [Background technology]

[0002] The acoustic laminate of the ultrasonic probe has a backing, an FPC (Flexible Printed Circuit) on which an electrode pattern is formed, a single crystal piezoelectric body (hereinafter simply referred to as a "piezoelectric body"), and an acoustic matching layer. The acoustic laminate generally has a structure in which a backing is provided on the rear surface of the FPC, and a piezoelectric body and an acoustic matching layer are laminated in that order on the front surface of the FPC.

[0003] Here, the surfaces of the backing, the piezoelectric body, and the acoustic matching layer have some degree of unevenness. For example, the arithmetic mean roughness Ra of the piezoelectric body is about 0.2 to 0.3, and the arithmetic mean roughness Ra of the acoustic matching layer is about 0.2 to 1.0. Since voltage is applied from both the front and rear sides of the piezoelectric body, metal layers are vapor-deposited on the surfaces of the piezoelectric body and the acoustic matching layer. Then, the piezoelectric body on which the metal layer is vapor-deposited is bonded to the FPC via a bonding layer, and the acoustic matching layer on which the metal layer is vapor-deposited is bonded to the piezoelectric body via a bonding layer.

[0004] However, in order to reduce the effect on the ultrasonic waves generated by the piezoelectric body, the bonding layer between the piezoelectric body and the acoustic matching layer needs to be thin (for example, 5 μm or less), because if the bonding layer is thick, it will have a large effect on the ultrasonic waves.

[0005] Furthermore, when a thin film adhesive is used to bond the piezoelectric body and the acoustic matching layer, electrical continuity is not uniform due to partial electrical continuity at the contact points of the surface protrusions between the piezoelectric body and the acoustic matching layer. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2011 / 033666 Summary of the Invention [Problem to be solved by the invention]

[0007] One of the problems to be solved by the embodiments disclosed in this specification and the drawings is to realize stable conduction while bonding a piezoelectric body and an acoustic matching layer with a thin film. However, the problems to be solved by the embodiments disclosed in this specification and the drawings are not limited to the above problem. Problems corresponding to the effects of each configuration shown in each embodiment described later can also be positioned as other problems. [Means for solving the problem]

[0008] The acoustic laminate according to the embodiment includes a backing, an FPC, and an acoustic laminate having a piezoelectric body and an acoustic matching layer, each of which is coated with a metal layer on at least the lamination surface. The acoustic matching layer and the piezoelectric body are bonded to each other by a bonding layer formed of a low melting point metal. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view showing an example of the configuration of an acoustic laminate according to an embodiment. [Diagram 2] FIG. 2 is a cross-sectional view showing an example of the configuration of an acoustic laminate according to a comparative example. [Diagram 3] FIG. 3 is a partially enlarged view of an acoustic laminate according to a comparative example. [Figure 4] FIG. 4 is a partially enlarged view of an acoustic laminate according to a comparative example. [Diagram 5] FIG. 5 is a partially enlarged view of an acoustic laminate according to a comparative example. [Figure 6] FIG. 6 is a flowchart showing a joining flow of an acoustic laminate according to an embodiment. [Figure 7] FIG. 7 is a diagram for explaining the mechanism of removing an oxide film by ultrasonic waves in the acoustic stack according to the embodiment. [Figure 8] FIG. 8 is a diagram for explaining a film forming and bonding process for an acoustic laminate according to an embodiment. [Figure 9] FIG. 9 is a diagram for explaining an ultrasonic bonding process for an acoustic laminate according to an embodiment. [Figure 10] FIG. 10 is a diagram for explaining an induction heating bonding process for an acoustic laminate according to an embodiment. [Figure 11] FIG. 11 is a graph showing a bonding state by film formation in an acoustic stack according to an embodiment. [Figure 12] FIG. 12 is a diagram showing the measurement results of the film thickness of a bonding layer formed in an acoustic stack according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of an acoustic stack, an ultrasonic probe, a method for manufacturing an acoustic stack, and a method for manufacturing an ultrasonic probe will be described in detail with reference to the drawings.

[0011] FIG. 1 is a cross-sectional view showing an example of the configuration of an acoustic laminate 1 according to an embodiment. The acoustic laminate 1 is provided in an ultrasonic probe 100, and includes a backing 11, an FPC (Flexible Printed Circuit) 12 on which an electrode pattern is formed, a piezoelectric body 13, and an acoustic matching layer 14. The acoustic laminate 1 has a structure in which the backing 11 is provided on the rear surface of the FPC 12, and the piezoelectric body 13 and the acoustic matching layer 14 are laminated in that order on the front surface of the FPC 12. Hereinafter, the acoustic laminate 1 will be described as a laminate in which the backing 11, the FPC 12, the piezoelectric body 13, and the acoustic matching layer 14 are laminated in that order, but is not limited to this case. For example, the acoustic laminate 1 may be a laminate in which the FPC 12, the backing 11, the piezoelectric body 13, and the acoustic matching layer 14 are laminated in that order.

[0012] The backing 11 absorbs ultrasonic waves traveling rearward from the piezoelectric body 13 to suppress excess vibration. The FPC 12 is a wiring material in which an electric circuit is formed on an extremely thin insulating film. The piezoelectric body 13 has electrodes formed on both sides to generate ultrasonic waves. The acoustic matching layer 14 is made of a sintered body or the like.

[0013] Here, the backing 11, the piezoelectric body 13, and the acoustic matching layer 14 have some unevenness on their surfaces. For example, the arithmetic mean roughness Ra of the piezoelectric body 13 is about 0.2 to 0.3, and the arithmetic mean roughness Ra of the acoustic matching layer 14 is about 0.2 to 1.0. Since a voltage is applied from both the front and back sides of the piezoelectric body 13, the surfaces of the piezoelectric body 13 and the acoustic matching layer 14 (at least the front and rear surfaces, which are the lamination surfaces) are each coated (deposited) with a metal layer (deposited metal layers 23, 24). If necessary, an oxide film (reference numeral 232 shown in FIG. 7) is removed from the surfaces of the deposited metal layers 23, 24 by a method described later. The acoustic laminate 1 is formed by bonding the acoustic matching layer 14, on which the deposited metal layer 24 is deposited, to the piezoelectric body 13, on which the deposited metal layer 23 is deposited, via a thin film bonding layer 33. The thin film bonding layer 33 is formed using a low melting point metal. The low melting point metal is, for example, 58% Bi-42% Sn. If the low melting point metal is 58% Bi-42% Sn, a thin film can be realized as described later.

[0014] At least the lamination surfaces of the backing 11 and the FPC 12 may be coated (deposited) with a metal layer, similar to the deposited metal layers 23 and 24. The backing 11 and the FPC 12, and the FPC 12 and the piezoelectric body 13 are bonded with thin film bonding layers 31 and 32 formed of a low melting point metal, similar to the thin film bonding layer 33. However, this is not limited to this case, and at least one of the thin film bonding layers 31 and 32 may not be formed of a low melting point metal. In this case, at least one of the thin film bonding layers 31 and 32 is formed of, for example, Au-Sn.

[0015] On the other hand, FIG. 2 is a cross-sectional view showing an example of the configuration of an acoustic laminate 1A according to a comparative example. The acoustic laminate 1A is provided in an ultrasonic probe 100A, and includes a backing 11A, an FPC 12A, a piezoelectric body 13A, and an acoustic matching layer 14A. The acoustic laminate 1A has a structure in which the backing 11A is provided on the rear surface of the FPC 12A, and the piezoelectric body 13A and the acoustic matching layer 14A are laminated in that order on the front surface of the FPC 12A. The backing 11A, like the backing 11, absorbs ultrasonic waves directed from the piezoelectric body 13A to the rear side to suppress unnecessary vibration. The piezoelectric body 13A, like the piezoelectric body 13, generates ultrasonic waves by forming electrodes on both the front and rear surfaces. The acoustic matching layer 14A is made of a sintered body or the like. Metal layers are vapor-deposited on the surfaces of the piezoelectric body 13A and the acoustic matching layer 14A (vapor-deposited metal layers 23A, 24A). The acoustic laminate 1A is formed by bonding an acoustic matching layer 14A, on which a vapor-deposited metal layer 24A is deposited, to a piezoelectric body 13A, on which a vapor-deposited metal layer 23A is deposited, via a bonding layer 33A. Similarly, the backing 11A and the FPC 12A, and the FPC 12A and the piezoelectric body 13A are bonded by bonding layers 31A and 32A, respectively, in the same manner as the bonding layer 33A.

[0016] Here, a case where an adhesive is used for the bonding layer 33A shown in Fig. 2 will be described with reference to Fig. 3. Fig. 3 shows an enlarged view of region R shown in Fig. 2. An adhesive that is easy to make thin and can accommodate surface irregularities is used for bonding the piezoelectric body 13A and the acoustic matching layer 14A with the bonding layer 33A. In thin-film bonding using such an adhesive, electrical current flows only partially where the piezoelectric body 13A and the acoustic matching layer 14A come into contact with the convex surface portions, and therefore the conductive portions are not uniform.

[0017] In addition, a case where a conductive adhesive is used for the adhesive layer 33A shown in Fig. 2 will be described with reference to Fig. 4. Fig. 4 shows an enlarged view of an area R' corresponding to the area R shown in Fig. 2. A conductive adhesive of a silver nanoparticle adhesive is used as an adhesive having electrical conductivity. However, in this case, it is difficult to make the adhesive thin due to the influence of viscosity, binder material, etc.

[0018] Furthermore, the case where room temperature bonding is performed will be described with reference to Fig. 5. Fig. 5 shows an enlarged view (lower part) of region R'' corresponding to region R shown in Fig. 2, and the state prior to that (upper part). To perform room temperature bonding, the surfaces of piezoelectric body 13A and acoustic matching layer 14A need to be smoothed to approximately mirror finish. While the surfaces of backing 11A and piezoelectric body 13A can be polished, the sintered body used in acoustic matching layer 14A has granular agglomerates and is therefore difficult to smooth.

[0019] Among the bonding methods described in Fig. 3 to Fig. 5, the bonding method using an adhesive shown in Fig. 3 will be described below. As described above, the bonding method using an adhesive has a problem in that it is not possible to achieve both stable conduction over the entire surface including the uneven parts and a thin-film bonding layer that has little effect on ultrasonic waves. Therefore, in the acoustic laminate 1 shown in Fig. 1, a thin film of a low-melting point metal is used as the thin-film bonding layer 33 between the piezoelectric body 13 and the acoustic matching layer 14. This makes it possible to realize stable conduction over the entire surface between the piezoelectric body 13 and the acoustic matching layer 14 while suppressing the effect on ultrasonic waves.

[0020] Next, a flow including the joining process will be described with reference to the flowchart shown in Fig. 6. In Fig. 6, the reference characters "ST" followed by numbers indicate each step in the flowchart.

[0021] A melting layer 33' melted at a low temperature is formed between the deposited metal layer 23 deposited on the work surface of the piezoelectric body 13 and the deposited metal layer 24 deposited on the work surface of the acoustic matching layer 14 (step ST1). It is determined whether the deposited metal layers 23, 24 deposited on the work surfaces of the piezoelectric body 13 and the acoustic matching layer 14 are made of an oxidizable metal (step ST2). If the determination in step ST2 is YES, that is, if it is determined that the deposited metal layers 23, 24 are made of an oxidizable metal (for example, if the deposited metal layers 23, 24 are made of Cu), an ultrasonic wave is applied to the melting layer 33' melted at a low temperature in the bonding process to remove the oxide film of the deposited metal layers 23, 24 that are in contact with the deposited metal layers 23, 24 (step ST3). The reason for removing the oxide film here is that the bonding strength is reduced due to the presence of the oxide film on the surfaces of the deposited metal layers 23, 24, making it easier for the thin film bonding layer 33 and the deposited metal layers 23, 24 to peel off from each other.

[0022] The mechanism of removing an oxide film by ultrasonic waves will be described with reference to FIG. 7. As shown in FIG. 7(A), the evaporated metal layer 23 of the piezoelectric body 13 and the melted layer 33' that melts at a low temperature are shown. The evaporated metal layer 23 has a main layer 231 that is not oxidized and an oxide film 232 on the surface that is oxidized. When ultrasonic waves are applied to the melted layer 33', micro bubbles are generated inside the melted layer 33' due to the cavitation phenomenon (shown in FIG. 7(B)). Next, the generated bubbles are crushed (burst) by external pressure. Next, a strong impact force is generated around the bubbles when they burst. As a result, a part of the oxide film 232 is destroyed (shown in FIG. 7(C)). The part directly touches the melted layer 33' and is firmly bonded by metal diffusion. The bonding between the evaporated metal layer 24 and the thin film bonding layer 33 is similar to the bonding between the evaporated metal layer 23 and the thin film bonding layer 33, so a description thereof will be omitted.

[0023] 6, the molten layer 33' is cooled, and the piezoelectric body 13 and the acoustic matching layer 14 are bonded to each other by the thin film bonding layer 33 (step ST4, FIG. 7(D)), thereby completing the bonding process. The bonding process is performed in a room temperature air environment, a gas atmosphere, or a vacuum atmosphere.

[0024] On the other hand, if the determination in step ST2 is NO, that is, if it is determined that the deposited metal layers 23, 24 deposited on the work surfaces of the piezoelectric body 13 and the acoustic matching layer 14 are not made of a metal that oxidizes (for example, if the deposited metal layers 23, 24 are made of Au), the molten layer 33' formed in step ST1 is also cooled, and the piezoelectric body 13 and the acoustic matching layer 14 are bonded by the thin film bonding layer 33 (step ST4). If the metal of the deposited metal layers 23, 24 does not oxidize, the use of ultrasonic waves is not essential.

[0025] The acoustic laminate 1 produced by the bonding in step ST4 is placed in a probe housing to produce the ultrasonic probe 100 (step ST5).

[0026] The bonding process in steps ST3 and ST4 in Fig. 7 will be described with reference to Fig. 8 to Fig. 10. Fig. 8 shows a film-forming bonding process, Fig. 9 shows an ultrasonic bonding process, and Fig. 10 shows an induction heating bonding process.

[0027] In the film-forming and bonding process shown in Fig. 8, the heating temperature (melting temperature) of the portion where the melting layer is formed should be slightly higher (e.g., +20°C) than the melting point of the low-melting-point metal (e.g., 140°C). The pressure applied during bonding can be reduced by controlling the initial film thickness. From the viewpoint of piezoelectric polarization, a heating temperature of 200°C or less is appropriate in the manufacturing process of the acoustic laminate 1, so a temperature of around 160°C satisfies this requirement.

[0028] First, as shown in Fig. 8(A), metal powder of the low-melting-point metal M is placed on the deposited metal layer 23 (the same applies to the deposited metal layer 24 on the acoustic matching layer 14) on the surface of the piezoelectric body 13. Alternatively, as shown in Fig. 8(B), a metal bulk of the low-melting-point metal M is placed on the deposited metal layer 23 (the same applies to the deposited metal layer 24 on the surface of the acoustic matching layer 14) on the surface of the piezoelectric body 13. Then, the heating plate P for stretching the low-melting-point metal M and the deposited metal layer 23 are heated to a temperature slightly higher than the melting point of the low-melting-point metal M. The molten low-melting-point metal M is stretched by the heating plate P. At this time, if the deposited metal layer 23 is made of an oxidizable metal, the low-melting-point metal M is stretched while the heating plate P is ultrasonically vibrated as described above. Fig. 8(C) shows a state of a molten layer 33' formed by stretching low-melting-point metal M so as to fill the recessed spaces on the surface of the evaporated metal layer 23 on the surface of the piezoelectric body 13 (as well as the evaporated metal layer 24 on the surface of the acoustic matching layer 14). The right side of Fig. 8(C) is an enlarged view of the region U on the left side.

[0029] The piezoelectric body 13 having the molten layer 33' formed on the deposited metal layer 23 and the molten layer 33' of the acoustic matching layer 14 having the molten layer 33' formed on the deposited metal layer 24 are butted against each other and heated again while applying pressure (shown in FIG. 8(D)). The right side of FIG. 8(D) is an enlarged view of the region V on the left side. The molten layer 33' is then remelted and integrated to complete the bonding. The thickness of the thin film bonding layer 33 obtained by cooling the molten layer 33' is preferably 0.1 μm to 5 μm, and more preferably 1 μm to 3 μm.

[0030] In the ultrasonic bonding process shown in Fig. 9, the heating temperature is applied to only the portion where the melt layer is formed. Therefore, the thermal influence on the piezoelectric body 13 and other resin materials can be reduced. Also, in Fig. 9, it is not essential to form a film of low melting point metal M to fill the recessed space. Foil, sputtering or plating methods may or may not be used.

[0031] 9(A), metal powder (or metal bulk) of low-melting point metal M is placed on the deposited metal layer 23 (or the deposited metal layer 24 on the surface of acoustic matching layer 14) on the surface of piezoelectric body 13. Then, acoustic matching layer 14 is placed so that the deposited metal layer 24 is superimposed on the deposited metal layer 23 on which low-melting point metal M is placed (shown in FIG. 9(B)).

[0032] The lower workpiece, the piezoelectric body 13, is fixed by a fixing device D, and ultrasonic vibration is applied to the upper workpiece, the acoustic matching layer 14, while pressure is applied to the entire surface (shown in FIG. 9(C)). The pressure is applied in the vertical direction of the workpiece, and the vibration is applied in the horizontal direction of the workpiece. Note that the lower workpiece may be the acoustic matching layer 14, while the upper workpiece may be the piezoelectric body 13, and the acoustic matching layer 14 may be fixed.

[0033] The friction heats the molten layer 33', melting the low-melting metal M. The molten low-melting metal M spreads and integrates with the acoustic matching layer 14 by applying pressure from above, forming a film (see FIG. 9(D)). The metal of the deposited metal layers 23 and 24 and the low-melting metal M are diffusion bonded, and the piezoelectric body 13 and the acoustic matching layer 14 are integrated via the molten layer 33'. The thickness of the thin-film bonding layer 33 formed by cooling the molten layer 33' is preferably 0.1 μm to 5 μm, and more preferably 1 μm to 3 μm. The metal of the deposited metal layers 23 and 24 and the low-melting metal M are bonded at the atomic level (see FIG. 9(E)).

[0034] FIG. 10 shows the induction heating bonding process. When a current flows through a coil connected to an AC power source, magnetic lines of force are generated around the coil. If a conductive metal is placed inside (or near) the coil, an "eddy current" flows in the metal in a direction that prevents the change in magnetic flux. Since metal has electrical resistance, Joule heat is generated and the metal is heated. The induction heating bonding process utilizes this induction heating phenomenon. In the induction heating bonding process, the heating temperature is used to locally heat only the part where the molten layer is formed (especially the low melting point metal). Therefore, the thermal effect on the piezoelectric body 13 and other resin materials can be reduced. Also, in FIG. 10, it is not essential to form a film with low melting point metal M to fill the recessed space. Foil, sputtering, or plating methods may or may not be used.

[0035] First, as shown in Fig. 10(A), a metal powder (or a metal bulk) of a low-melting point metal M is placed on the deposited metal layer 23 (or the deposited metal layer 24 on the surface of the acoustic matching layer 14) on the surface of the piezoelectric body 13. Then, the acoustic matching layer 14 is placed so that the deposited metal layer 24 is superimposed on the deposited metal layer 23 on which the low-melting point metal M is placed (as shown in Fig. 10(B)).

[0036] The workpiece is placed in the induction heating coil C, which is positioned according to the low melting point metal M to be used, and pressure is applied (as shown in FIG. 10(C)). In the pressurized state, current is passed through the induction heating coil C to heat and melt the low melting point metal (as shown in FIG. 10(C)). The molten low melting point metal M spreads throughout (as shown in FIG. 10(D)). Diffusion bonding occurs between the metal of the evaporated metal layers 23, 24 and the low melting point metal M, and the piezoelectric body 13 and the acoustic matching layer 14 are integrated via the molten layer 33'. The thickness of the thin film bonding layer 33 formed by cooling the molten layer 33' is preferably 0.1 μm to 5 μm, and more preferably 1 μm to 3 μm.

[0037] Here, a mock-up of the acoustic laminate 1 was manufactured using the film-forming and bonding process shown in Fig. 8. First, a non-lead solder (e.g., 58% Bi-42% Sn) made of a low melting point metal was formed on a substrate (e.g., a Cu plate) (ultrasonic vibration + heating). Heating was performed using a hot plate, and the temperature of the film-forming surface of the Cu plate was adjusted to 160°C, and the temperature was kept at atmospheric pressure and room temperature. Next, the film-forming surface of the piezoelectric body 13 (e.g., 58% Bi-42% Sn) and the film-forming surface of the acoustic matching layer 14 were butted against each other and heated while applying pressure.

[0038] The pressure load was set to approximately 30 kPa, and the temperature of the butted surfaces of the coating was adjusted to 160°C. Grinding was performed with sandpaper or by hand (grain size #60 to #1200), and the cross section was cut out and its condition was checked. It was confirmed that the oxide film on the coating surface had disappeared due to the ultrasonic vibration. Therefore, it is believed that the oxide films have remelted and become one.

[0039] The lower part of Fig. 11 is a graph showing the bonding state at position Q in the cross section of the upper part. As shown in the lower part of Fig. 11, especially in region T, the Cu plate and the 58%Bi-42%Sn elements intersect, suggesting metal integration.

[0040] 12 is a diagram showing the measurement results of the film thickness of the formed molten layer 33' (thin film bonding layer 33). The maximum thickness of the thin film bonding layer 33 made of 58%Bi-42%Sn can be made to be about 1 μm. This makes it possible to make the bonding layer 33 thinner.

[0041] The acoustic laminate 1 and the ultrasonic probe 100 including the same realize stable conduction while bonding the piezoelectric body 13 and the acoustic matching layer 14 with a thin film. Furthermore, the manufacturing method of the acoustic laminate 1 and the manufacturing method of the ultrasonic probe 100 make it possible to reproducibly manufacture the acoustic laminate 1 and the ultrasonic probe 100 that can be bonded with a thin film and realize stable conduction.

[0042] According to at least one of the embodiments described above, it is possible to realize stable conduction while bonding the piezoelectric body and the acoustic matching layer with a thin film.

[0043] Although some embodiments have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, modifications, combinations of embodiments, and combinations of embodiments with one or more modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0044] 1...Acoustic laminate 11...Backing 12...FPC 13...Piezoelectric body 14...Acoustic matching layer 21~24...Vapour-deposited metal layer 33...Thin film bonding layer 33´…Melting layer 100...Ultrasonic probe

Claims

1. An acoustic laminate having a backing, an FPC (Flexible Printed Circuit), and a piezoelectric body and an acoustic matching layer, each of which is coated with a metal layer on at least the laminate surface, the acoustic matching layer and the piezoelectric body are bonded together by a thin film bonding layer formed using a low-melting point metal; Acoustic laminate.

2. The low melting point metal is 58% Bi-42% Sn.

10. The acoustical laminate of claim 1.

3. An acoustic laminate as described in claim 1, wherein the backing is provided between the FPC and the piezoelectric element.

4. An acoustic laminate as described in claim 1, in which the metal layer is coated on the surfaces of the piezoelectric element that are not laminated with the acoustic matching layer, and the piezoelectric element is joined to other components by a thin film bonding layer formed using a low-melting point metal.

5. The acoustic stack according to any one of claims 1 to 4, An ultrasound probe comprising:

6. 5. A method for manufacturing the acoustical stack of any one of claims 1 to 4, comprising the steps of: the low-melting-point metal is melted in a room-temperature atmospheric environment, a gas atmosphere, or a vacuum atmosphere to bond the acoustic matching layer and the piezoelectric body together, thereby producing the acoustic laminate; Method for manufacturing acoustic laminates.

7. the low-melting-point metal is melted at a melting temperature of 200° C. or less to bond the acoustic matching layer and the piezoelectric body; A method for producing the acoustical laminate of claim 6.

8. forming the metal layer by vapor deposition on the laminated surface of the piezoelectric body and the acoustic matching layer; the low-melting-point metal is deposited so as to fill the recessed spaces on the surfaces of the acoustic matching layer and the piezoelectric body; A method for producing the acoustical laminate of claim 6.

9. A film is formed so as to fill the recess space by stretching the metal powder or metal bulk of the low-melting point metal arranged on the surface of the acoustic matching layer and the surface of the piezoelectric body using a heating plate that is vibrated by ultrasonic waves. A method for making the acoustical laminate of claim 8.

10. forming the metal layer by vapor deposition on the laminated surface of the piezoelectric body and the acoustic matching layer; when the low-melting-point metal is melted to bond the acoustic matching layer and the piezoelectric body, vibration is applied to the metal layer by ultrasonic waves. A method for producing the acoustical laminate of claim 6.

11. 6. A method for manufacturing the ultrasonic probe of claim 5, comprising the steps of: placing the acoustic stack within a probe housing to produce the ultrasonic probe. A method for manufacturing an ultrasonic probe.

Images