JPS59141060A - Ultrasonic probe - Google Patents

Abstract

PURPOSE:To attain to improve the beam emitting shape and conversion efficiency of a probe, by performing the leading-out of the emitting side electrode of a piezoelectric element by a thin metal film formed by plating or vapor deposition. CONSTITUTION:Electrodes 41, 42 comprising gold or silver are formed on the entire front and back surfaces of a piezoelectric element 1 by baking or plating but the inner diameter of a holder 3 is set to a size larger than the diameter of the piezoelectric element 1 and a packing material 2 is interposed between both of them. The lower end surface of the holder 3 and the electrode 41 are set on the same surface and the end surface of the packing material 2 is also set on the same surface between both of them. In the next step, a thin metal film 7 with a thickness of several mum or less is formed on the front side of these surfaces while the adjustment of the thickness and conductivity is performed by a plating method. In this case, the holder 3 is made conductive to connect between the electrode 41 and a lead wire 51 by the path of electrode 41-metal film 7-holder 3-lead wire 51.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to an ultrasonic probe used for flaw detection, ultrasonic diagnosis, and the like.

Prior Art and Problems In a conventional ultrasonic probe, as shown in Fig. 1, a piezoelectric element 1 made of PZT or the like has a circular electrode 41.4 with silver baked on both sides.
2, and a part of the radiation side electrode 41 is bent to the back surface to form a folded electrode. This is to facilitate the connection of the lead wire 51 to the electrode 41, but for this purpose, a part of the back electrode 42 is cut out, and no electric field is applied to this cutout, so the whole is not driven uniformly. However, there are drawbacks such as deterioration of beam shape, efficiency, etc. This effect becomes particularly noticeable when the diameter of the piezoelectric element 1 becomes small, such as 10 fins or less. That is, the folded part of the electrode 41 shown in FIG. In the figure, 2 is a banking material that absorbs ultrasonic waves generated behind the piezoelectric element 1, 3 is a cylindrical holder, and 52 is a lead wire of the electrode 42. Although not shown, the holder 3 has a closed upper end. It has a short cylindrical body shape, and in the case of manual diagnosis, the short cylindrical body is embedded in the tip of a short bar-shaped case having a gripping part, and in the case of mechanical scanning type, it is embedded in the circumferential surface of the rotating cylinder at 120 degrees. It is used by being embedded in three pieces at intervals.

In FIG. 2, electrodes 41.
This is a conventional example in which a metal foil 6 for drawing out the radiation side electrode 41 is separately attached from the surface of the electrode 41 to the side surface of the holder 3, and the electrode drawing of the radiation side electrode 41 is carried out on the side surface of the holder 3.

In this way, the electrodes 41 and 42 can be arranged as disks of the same diameter and face each other in parallel planes, so that an electric field is applied to the entire piezoelectric element, and there are no problems with the beam shape, efficiency, etc. However, this metal foil 6 is made by thinly stretching a material such as gold, copper, or aluminum to a thickness of about 5 to 20 μm, and it is difficult to uniformly fix the metal foil 6 to the electrode 41 with an adhesive. Poor mass production. Therefore, the metal foil 6 is conventionally formed into a band shape extending in the diametrical direction as shown in FIG. When trying to attach an acoustic matching layer (not shown) on a board or the like using an adhesive such as epoxy, the adhesive layer needs to be thick enough to absorb the level difference, which has the disadvantage of degrading the acoustic matching. have

OBJECTS OF THE INVENTION The present invention aims to improve the method of drawing out electrodes so that the characteristics of the piezoelectric element are not deteriorated and the manufacturing thereof is easy.

Structure of the Invention The ultrasonic probe of the present invention comprises an ultrasonic radiation surface of a piezoelectric element, an adhesive layer on the side of the piezoelectric element and bonding between the end face of a holder having a conductive part and the piezoelectric element and the holder. A thin metal film is formed on each of the end faces by conductive treatment such as metal vapor deposition, sputtering, or plating, and the metal film is connected to the radiation-side electrode lead wire via the holder. This will be described in detail below with reference to the illustrated embodiments.

Embodiment of the Invention FIG. 3 is a longitudinal sectional view showing an embodiment of the present invention, in which the same parts as in FIG. 1 etc. are given the same reference numerals. Electrodes 41 and 42 of gold, silver, etc. are formed on the front and back surfaces of the piezoelectric element 1 by baking, vapor deposition, plating, etc. The inner diameter of the holder 3 is set larger than the diameter of the piezoelectric element 1, and there is a space between them. A backing material 2 is interposed. The lower end surface of the holder 3 and the electrode 41 are set on the same surface, and the end surface of the backing material 2 between them is also set on the same surface. Then, a thin (several μm or less) metal film 7 is uniformly formed over the entire surface of these surfaces. The format of this metal film 7 is chemical plating, metal vapor deposition, sputtering, electroplating, etc., but unlike the first three, electroplating requires the base to be a conductor, so electroplating is performed after the first three to increase the thickness. Or conductivity adjustment. In this example, the holder 3 is made conductive and the electrode 41 - metal film 7 - holder 3
~Connect between the electrode 41 and the lead wire 51 through the path of the lead wire 51. To make the holder 3 conductive, the material itself must be a conductor such as metal, or the surface of a non-conductor such as resin, glass, or ceramic must be made conductive by baking, sputtering, vapor deposition, or applying a conductive paste. Bye. The lead wire 51 is soldered to the holder 3, and the lead wire 52 is soldered to the electrode 42. Note that the radiation-side electrode 41 can be omitted since the metal film 7 can also serve its function (the same applies to the following examples).

When the backing material 2 is made of a resin such as an epoxy resin mixed with metal powder such as tungsten, the banking material 2 may have conductivity. In this case, if the structure is as shown in FIG. 3, there is a possibility that the electrodes 41 and 42 or the electrode 42 and the holder 3 will be electrically connected. Therefore, in these cases, it is preferable to use a nonconductor such as an epoxy resin or an epoxy resin mixed with a metal oxide as the banking material 2. Alternatively, even if the banking material 2 is conductive, as in the second embodiment shown in FIG. 4, the electrode 41. 42 can be prevented from conducting. Furthermore, the electrode 42 and the lead 5 are connected through the banking 2.
In order to prevent conduction between the inner and outer surfaces of the holder 3, it is preferable to prevent conduction between the inner and outer surfaces of the holder 3. For example, holder 3
This is a method in which the outside and bottom surfaces are pre-conductively treated using resin.

FIG. 5 shows a third embodiment of the present invention, in which the holder 3 is made of a nonconductor. Therefore, the radiation side electrode 41 can be connected to the lead wire 51 by, for example, forming a metal film 7 on the side of the holder 3 as well. Furthermore, when soldering the back electrode 42 and the lead wire 52 in FIG. 3, since the back side is on the non-emission side and most of the generated ultrasonic waves are absorbed by the banking material 2, the effect on the piezoelectric element characteristics is small. However, in order to further reduce this as much as possible, in FIG. 5, the connection between the two is also made by a metal film 7' formed by a method such as sputtering or plating.

The metal film 7 is added by vacuum deposition or sputtering after fixing the piezoelectric element 1 and the case 3 with the banking material 2 or the adhesive 8, but in order to improve the adhesion, sputtering is preferable to normal vacuum deposition. Furthermore, the ion brating method, in which metal is ionized and implanted into the target, is suitable. As the metal material to be vapor-deposited, Ti, Cr, etc. are preferable for the first layer because they have excellent adhesion. In order to improve conductivity and reliability, it is preferable to further evaporate several layers of metal on this first layer, or to perform electroplating with Cu, Ni, or the like. However, as the metal layer 7 becomes thicker, the thickness of the piezoelectric element 1 becomes thicker isometrically, and the resonant frequency may decrease, so it is better to set the resonant frequency of the voltage-dividing element a little higher in advance.

An example of a method for adding the metal layer 7 will be shown below.

In order to improve adhesion, it is important to thoroughly clean the surface to be deposited or sputtered. For this purpose, cleaning using chemicals is first performed in an ultrasonic cleaning layer.

Examples are: ■ Washing for 1 minute in trichlene, ■ Washing for 1 minute in pure water, ■ Washing for 1 minute in IPA, ■ Washing for 1 minute in acetone, and after drying, in a vacuum chamber. Furthermore, it is preferable to clean the deposition surface using glow discharge.

Next, a metal film is added by sputtering and ion blasting. 10 as an example of sputtering
0 people Ti is added first, and 500 people Ni is added later. In order to further improve conductivity, Cu electroplating was applied.
μm is applied.

500 Cr as one row of ion blasting
After that, 1 μm of Ni is added. Sufficient conductivity is ensured in this state, but to improve reliability, Ni electroplating is applied to a thickness of 2 to 3 μm.

All of the metal films 7 formed in the above steps adhered firmly and had good adhesion to the resin. Additionally, a silicone or epoxy surface coating is applied to protect the electrode surface. This protective film can also serve as an acoustic matching layer, and it is desirable to do so. Further, since the surface of the deposited metal film 7 has few irregularities, it is also possible to bond a thin plate of glass or the like as an acoustic matching layer.

FIG. 6 shows a fourth embodiment of the present invention, in which the holder 3 is made of glass;
It is formed in an annular shape from a nonconductor such as ceramic or resin, and relay portions 91.92 of the electrodes 41.42 are formed on the surface thereof by baking or the like. The relay part 91 is a conductor having a U-shaped cross section, and contacts the metal film 7 at the bottom surface. Further, the upper surface of the relay section 91 is soldered to the lead wire 51. The relay part 92 is a conductor formed only on the upper surface of the holder 3, and a gold wire or aluminum wire 53 of about 25 μm is connected between it and the electrode 42.
Connect using ultrasonic waves, bonding (or arc connection). This method is effective for piezoelectric elements with a small diameter (for example, 511 mm or less) where the influence of soldering cannot be ignored. In order to increase the reliability of bonding,
) It is preferable to provide the lines 53 at several locations. In the example shown in FIG. 6, since the banking material 2 solidifies and becomes a support, a long holder 3 (which also functions as a case) as shown in FIG. 4 is not particularly required. 8 is the non-conductive banking agent or adhesive described above.

FIG. 7 is a fifth embodiment of the present invention applied to a linear array or sector array type probe.

In this type of ultrasonic probe, each piezoelectric element 1 is divided into smaller pieces, so the back electrode 42 side is connected to the relay part 92 by bonding with a wire 53, and the electrode 41 on the radiation side is connected to the relay part 92 by a metal film 7. Manufacturing is facilitated by connecting it to the relay section 91. The present invention is particularly effective in the case of this split vibrator.

In addition, in the above embodiments from FIG. 1 to FIG. 7, the piezoelectric element 1
may be not only a flat type but also a concave concentrated type.

Effects of the Invention As described above, according to the present invention, the radiation side electrode of the piezoelectric element is drawn out using a thin metal film formed by plating, vapor deposition, etc., which facilitates production and reduces the influence on the piezoelectric element characteristics. It has the advantage of being able to be made smaller and improving the radiation beam shape and conversion efficiency of ultrasound probes, especially those that use small piezoelectric elements.

[Brief explanation of the drawing]

FIGS. 1 and 2 are block diagrams showing different examples of conventional ultrasonic probes, and FIGS. 3 to 7 are block diagrams showing different embodiments of the present invention. In the figure, 1 is a piezoelectric element, 2 is a sawing material, 3 is a holder,
41 is a radiation side electrode, 42 is a back electrode, 51.52 is a lead wire, 7.7' is a metal film, 8 is an adhesive layer, and 91.92 is a relay part. Applicant Fujitsu Limited Patent Attorney Minoru Aoyagi Figure 1 Figure 3 Figure 1 Figure 2 Figure 5 1 Ward 4 51 Page 7

Claims (5)

[Claims] (1) Metal vapor deposition and sputtering on the ultrasonic emission surface of the piezoelectric element, the end face of the holder that has a conductive part on the side of the piezoelectric element, and the end face of the adhesive layer that adheres between the piezoelectric element and the holder. Alternatively, an ultrasonic probe characterized in that a thin metal film is formed by conducting conductive treatment such as plating, and the metal film is connected to a radiation-side electrode lead wire via the holder. (2) The ultrasonic probe according to claim 1, wherein the ultrasonic radiation surface of the piezoelectric element, the end surface of the holder, and the end surface of the adhesive layer are set to be substantially the same plane. (3) The ultrasonic probe according to claims 1 and 2, wherein the adhesive layer is a part of the banking material. (4) The ultrasonic probe according to claims 1 to 3, wherein the metal film is connected to the radiation-side electrode lead wire at a location other than the ultrasound radiation surface. (5) Claims 1 to 4, characterized in that the holder has a relay part for the back electrode of the piezoelectric element in a part thereof, and a lead wire for the back electrode is connected to the relay part. The ultrasonic probe according to any of the above. The ultrasonic probe according to claim 5, wherein the inverted relay part and the back electrode are connected by one or more thin wires connected by an ultrasonic ponder or arc welding. .