JPH0347800B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method of manufacturing an ultrasonic probe used in an ultrasonic flaw detection device, a medical ultrasonic diagnostic device, and the like.

Prior Art An example of the configuration of a conventional medical ultrasound probe using a back load, particularly an array type ultrasound probe, is shown in Fig. 6.
This will be explained below.

FIG. 6 shows a perspective view of a conventional array type ultrasonic probe, in which a plurality of piezoelectric vibrators 13 separated by grooves or the like are arranged, and the ultrasonic wave transmitting/receiving surface of the piezoelectric vibrators 13 is arranged. In order to efficiently propagate ultrasonic waves, one or more acoustic matching layers 14 are provided. By applying an electric signal to an electrode 16 provided on the piezoelectric vibrator 13, ultrasonic waves are emitted from the acoustic matching layer 14. The back load material 15 provided on the opposite side of the ultrasonic wave transmitting/receiving surface of the piezoelectric vibrator 13 has the role of damping the vibrator excited by the electric signal and obtaining a short pulse signal.

The main characteristics required for the material of this back loading material 15 are that it be uniform, have high hardness, have a large sound wave attenuation coefficient, and be able to obtain a predetermined acoustic impedance value. Uniformity at the positions of the 13 piezoelectric vibrators arranged, that is, variations in hardness, acoustic impedance values, etc., will cause a decrease in piezoelectric vibrator arrangement accuracy, disturbance of sound field characteristics, deterioration of ultrasound image characteristics such as sensitivity variations. This may cause

Conventionally, this back loading material 15 has been made by mixing metal powder, such as tungsten powder, in an Araldite-based thermosetting resin solution, and then adding a suitable sound scattering material and curing it, ferrite rubber, plastic, or the like. Urethane rubber filled with a sound scattering material such as a glass hollow body is used.
In the former case where metal powder is mixed and cured in an Araldite thermosetting resin solution, the acoustic impedance value can be changed by changing the mixing ratio of both materials or the size of the metal powder particles. Therefore, it is easy to realize an acoustic impedance value corresponding to the desired probe performance, and it is often used as a back loading material.

The installation of the back load material 12 on the piezoelectric vibrator 13 can be carried out by forming a mixed and hardened back load material in advance and bonding it to the piezoelectric vibrator 13;
There is a method of suddenly pouring the mixed state (fluid state) into the piezoelectric vibrator 13 and curing it in a state integrated with the piezoelectric vibrator 13.The latter method is suitable for piezoelectric vibration in a complicated shape, for example, a convex shape. This method is suitable for an ultrasonic probe having a structure in which probes are arranged in an array.

Problems to be Solved by the Invention However, when constructing a probe using a back-loading material made by mixing and hardening metal powder and a sound scattering material in a resin solution, if the back-loading material is uniform, that is, resin It is important that the metal powder is mixed uniformly in the solution. This is because, as mentioned above, the acoustic impedance value changes depending on the mixing ratio of the materials, and in general, the acoustic impedance value of the back load of the ultrasonic probe and the sensitivity of the transmitting and receiving signals of the probe are different. The relationship changes depending on the magnitude of the acoustic impedance value, and the sensitivity tends to decrease as the acoustic impedance increases. However, on the contrary, there is a tendency for damping characteristics to be improved, and therefore a uniform back loading material having an acoustic impedance value corresponding to the desired probe performance is required.

Particularly in the case of an array type ultrasonic probe, if the mixing of the backside loading material is non-uniform, it will cause variations in characteristics among the piezoelectric vibrators arranged. However, because the difference in specific gravity between the resin solution and the metal powder is extremely large, it is difficult to manufacture them uniformly, and this becomes even more difficult when it is desired to increase the particle size of the metal powder, making it difficult to create a probe with stable characteristics. It was difficult to manufacture.

Therefore, in order to solve the conventional problems as described above, the present invention provides a method for manufacturing a back-loaded material having a uniform mixture, and an ultrasonic probe with stable characteristics and quality constructed using the back-loaded material. The purpose is to provide a method for producing children.

Means for Solving the Problems The technical means of the present invention to achieve the above object is that the back loading material of the ultrasonic probe is a thermosetting resin filled with at least metal powder, such as tungsten powder. Mixing and curing is performed by stirring the material, defoaming the air in the material after stirring, cooling and hardening, and heating and hardening after cooling, and the back-loading material is molded simultaneously or simultaneously with the molding. This is a method of manufacturing an ultrasonic probe that is provided on the opposite side of the ultrasonic wave transmission/reception side of the piezoelectric vibrator after molding.

Effect The present invention makes it possible to obtain a uniformly mixed and cured back-loaded material by performing cooling curing before heat-curing, that is, a back-loaded material having an acoustic impedance value that matches the desired transducer performance. It is possible to make the material stably and uniformly, and eliminates variations in characteristics and quality between piezoelectric vibrators in an array-type ultrasonic probe.

Examples Examples of the present invention will be described below with reference to the drawings.

FIG. 1 shows, step by step, a method for manufacturing a back loading material by mixing and curing a thermosetting resin and metal powder in an embodiment of the present invention. In Figure 1, 2023 thermosetting resin such as epoxy resin is used.
(manufactured by Yokohama Three Bond) as main agent 1, metal powder 2
As a result, tungsten powder and scattering materials 3 such as plastic hollow bodies and glass hollow bodies of approximately several tens of microns are mixed and stirred 5. At the time of stirring 5, an appropriate amount of curing agent 4 is mixed and stirring 5 is carried out in the same manner. The air mixed into the material by the stirring 5 is removed by the defoaming 6, but due to the inclusion of air bubbles in the defoaming 6, variations occur in the properties of the material as a back load material. Furthermore, the mechanical strength is also weakened, which poses a problem. After defoaming 6, the material is precured in cooling hardening 7 so that the mixed and stirred materials, ie, the tungsten powder and the scattering material 3, are hardened to some extent without precipitation or separation. After cooling hardening 7, it is completely hardened in heating hardening 8. By the way, the cooling hardening step 7 is an important step in which the mixed materials are pre-hardened in a uniform state so that they do not precipitate or separate.The mechanism for this is shown in FIG. This can be explained using a graph of actual measurements over time. Figure 2 shows the temporal changes in the internal temperature of the material when the material is cured at room temperature (room temperature curing) and when the material is cooled to about 7°C (cooling curing) after the degassing step of the manufacturing method. This is what is shown. The production weight according to the measurement data is 200 g of the main material, 550 g of tungsten powder (particle size + several μm), 6.6 g of the plastic hollow body as a scattering material, and 20 g of the hardening agent.
In FIG. 2, in the case of room temperature curing, the internal temperature of the material rises rapidly after mixing and stirring, which is thought to be due to reaction heat during curing. It is clear that the heat of reaction here varies depending on the weight to be produced. However, in the case of cooling hardening, the temperature does not rise sharply and gradually decreases. In fact, when we compare materials that have been cured at room temperature and those that have been precured by cooling, we find that in the case of cold hardening, tungsten powder and scattering material are evenly mixed, but in the case of room temperature hardening, tungsten powder is mixed evenly. The precipitated and scattered material separates to the top and is not mixed uniformly. This is thought to be because the viscosity of the main ingredient drops significantly due to the rapid temperature rise at the beginning of mixing and stirring, causing the tungsten powder with a high specific gravity to precipitate, and the scattering material with a low specific gravity to separate to the upper part. Therefore, it is important to cool the material and gradually harden it while increasing its viscosity, as in this example. As mentioned before, the reaction heat changes depending on the amount of fabrication, but during the cooling and hardening process, it is best to harden the mixed materials at 40°C or below. On the other hand, if the temperature is too low, it will not harden, so it is necessary to keep it at 10°C or higher. Figure 3 shows the viscosity change with respect to temperature of epoxy resin 2023 (manufactured by Yokohama Three Bond) used as the main resin in this example.As the temperature increases, the viscosity decreases considerably, causing adverse effects such as precipitation. . According to this embodiment, even if the particle size of the tungsten powder is ten or more μm, it can be uniformly produced. FIGS. 4 and 5 are perspective views showing one embodiment of a method for manufacturing an ultrasonic probe, showing a method for constructing a back surface load material and a piezoelectric vibrator having an acoustic matching layer according to the present invention. In FIG. 4, an acoustic matching layer 11 is provided on the ultrasonic radiation surface of the piezoelectric vibrator 10 to efficiently propagate ultrasonic waves.
On the surface of the piezoelectric vibrator 10 opposite to this ultrasonic radiation surface, a back load material 9 is hardened in advance and formed into the shape of the piezoelectric vibrator 10 by the method shown in the above embodiment.
is attached by adhesive. FIG. 5 shows a configuration in which an acoustic matching layer 11 is provided in the same manner as the embodiment shown in FIG. Inside the 12,
The back loading material (fluid state) after mixing, stirring and defoaming according to this example is poured, and then, based on the manufacturing method shown in Fig. 1, it is pre-cured by cooling, and further heated and cured to form a piezoelectric vibrator. 10 shows a method for configuring a back loading material on the piezoelectric vibrator 10. In this case, even if the shape of the piezoelectric vibrator 10 is complicated, a back loading material having uniform characteristics can be easily constructed.

In the back loading material according to this example, the case where the main resin is an epoxy resin has been described, but the present invention can also be applied to cases where the main resin is polystyrene, polyurethane, polyester, polyethylene, etc.

Further, as the back loading material according to the present invention, it is sufficient that the thermosetting resin as the main ingredient is filled with at least metal powder, and a scattering material may be added as necessary.

In addition to tungsten, the metal powder to be filled in the thermosetting resin, which is the main ingredient of the back loading material according to the present invention, includes lead, molybdenum, tantalum, ferrite,
Tungsten carbide and the like are also applicable.

In addition, although the embodiments have mainly been described with reference to the case where it is applied to an array type ultrasonic probe, the present invention can be applied to various types of ultrasonic probes such as a single type ultrasonic probe with one piezoelectric vibrator. The applicability is clear.

Effects of the Invention In summary, the present invention provides a piezoelectric vibrator that transmits and receives ultrasonic waves, when a back load material is provided via an electrode on the side opposite to the ultrasonic wave transmitting/receiving side. It is filled with at least powder, and is characterized by comprising a step of stirring the thermosetting resin and metal powder, a step of defoaming after stirring, a step of cooling and hardening, and a step of heating and hardening. It provides a method for manufacturing ultrasonic probes.
It is possible to obtain a uniformly mixed and cured back loading material, stably create an acoustic impedance value suitable for the desired probe performance, and improve the characteristics and quality of the ultrasonic probe. . Further, by using the back loading material according to the present invention, it is possible to easily configure a uniform and stable back loading material even in an ultrasonic probe having a complicated piezoelectric vibrator shape.

[Brief explanation of drawings]

Fig. 1 is a process diagram showing an example of the manufacturing method of the back-loading material, which is part of the method of manufacturing the ultrasonic probe of the present invention, and Fig. 2 shows the curing temperature and its temperature of the back-loading material according to the present invention. A graph showing changes over time, FIG. 3 is a graph showing the relationship between viscosity and temperature of the main agent used in the back loading material according to the present invention, and FIGS. 4 and 5 are
A sixth perspective view showing a method for manufacturing an ultrasonic probe constructed from a backside loading material according to an embodiment of the present invention.
The figure is a perspective view of a conventional array-type ultrasound probe. 1... Main agent, 2... Metal powder, 3... Scattering material, 4
... hardening agent, 5 ... stirring, 6 ... defoaming, 7 ... cooling hardening, 8 ... heating hardening, 9, 15 ... back loading material, 10 ... piezoelectric vibrator.

Claims (1)

[Claims] 1. When providing a back loading material via an electrode on the side opposite to the ultrasound transmitting/receiving side of a piezoelectric vibrator that transmits and receives ultrasonic waves, the back loading material is a thermosetting resin filled with at least metal powder. , a method for manufacturing an ultrasonic probe, comprising the steps of stirring the thermosetting resin and metal powder, defoaming after stirring, cooling and hardening, and heating and hardening. .