JPS6133513B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a polymer electroacoustic transducer that is electrically reliable, has excellent water resistance, and durability.

(Prior art) Since it was discovered that piezoelectricity can be used for electromechanical transduction, electroacoustic transducers such as ultrasonic transducers using it have been specifically researched. I started to do that.

Many considerations are necessary to construct a polymer piezoelectric film into a practical ultrasonic transducer, but in particular, attention must be paid to the following points.

The first problem is how to form a stable electrode, the second problem is how to make stable electrical connections from this electrode to other systems, and the third problem is: The question is how to improve so-called stability and reliability, such as water resistance, durability, and stability against external electrical noise.

(Problems to be solved by the invention) Conventionally, electroacoustic transducers using polymer piezoelectric films,
In particular, there are some known examples regarding the structure of ultrasonic transducers, but these cannot be said to fully satisfy the above-mentioned reliability and stability.

For example, an ultrasonic transducer used in an ultrasonic diagnostic apparatus is used while being immersed in water for a long period of time, and in this case, extremely strong water resistance is required. Furthermore, depending on the conditions of use, a transducer for ultrasonic flaw detection is subjected to large mechanical shocks and friction. An ultrasonic transducer using a polymer piezoelectric film that can be used under such conditions has not been available in the past.

The present invention relates to an electroacoustic transducer such as the above-mentioned ultrasonic transducer having a joint between a metal body and a polymer, and which is extremely electrically reliable, has excellent water resistance, and durability. I will provide a.

(Means for Solving the Problems) That is, the present invention provides an electroacoustic transducer using a polymer piezoelectric film, characterized in that the polymer electroacoustic transducer has an additional layer soldered to a metal case. It provides:

The present invention will be explained below with reference to the drawings.

FIG. 1 is a schematic diagram showing the basic structure of an ultrasonic transducer as a specific example of the electroacoustic transducer according to the present invention. In Figure 1, 1 is a polymeric piezoelectric film, 2 is a back side electrode, 3 is a front side electrode made of a metal film, 4 is a surface additional layer made of a polymeric material, 5 is a conductive metal case, and 6 is solder. It is. In order to prevent the electrodes of the polymer piezoelectric membrane from being corroded,
It is necessary to strengthen the water resistance of the ultrasonic transducer so that components that chemically react with the electrode, such as water, do not enter the electrode section. According to the present invention, a conductive metal case 5 made of a metal body and a surface-added film 4 made of a polymeric material are soldered together via a front side electrode 3 formed on the surface of the surface-added film 4.
By joining the metal body and polymer body of the transducer, it is possible to make the transducer completely waterproof. The front electrode 3 is made of, for example, Cu, Cr, Ni, Au, etc., and can be made by chemical plating, vapor deposition, or other conventional methods, and can be preferably bonded to the conductive metal case 5. be. The surface additional film 4 is preferably made of highly heat-resistant aromatic polyamide, aromatic polyimide, etc. from the viewpoint of adhesion with the electrode and soldering with the metal case 5 after adhesion. However, any polymer film can be used as long as it does not melt or undergo significant deformation at the soldering temperature.

(Example and operation) An ultrasonic transducer having the structure shown in FIG. 2 was produced. Here, 11 is a piezoelectric film made of poled polyvinylidene fluoride, 12 is a back electrode made of a copper plate formed into a concave surface, and 13 is a piezoelectric film made of polyvinylidene fluoride.
A front side electrode made of a copper film adhered to a thickness of 1 μm by electrolytic plating on the upper surface of the surface-added film 14 made of aromatic polyamide with a thickness of 25 μm, 15 covers the metal case made of brass, and 17 covers the metal case 15. It is a plastic case, and 18 is a Bakelite support substrate.

The conductive metal case 15 and the front side electrode/surface additional film shown at 13 and 14 were bonded together with solder 16. Except for the parts bonded with solder 16, the other parts shown in FIG. 2 were bonded with epoxy adhesive.

The ultrasonic transducer thus produced was left in water for 5 months, and the insertion loss of the transducer and changes over time in the pulse drive waveform were measured, but no major changes were observed.

On the other hand, for comparison, a transducer with a surface-added film on which Al was vapor-deposited as an electrode that cannot be soldered was bonded to a metal case with an epoxy adhesive via the Al electrode surface was left underwater in the same manner as above. It was confirmed that the Al electrode had deteriorated one month after immersion.

As described above, the polymer electroacoustic transducer according to the present invention, which is characterized in that the additional layer and the metal case are connected by soldering, has high electrical reliability, and in particular has significantly improved water resistance and durability. are doing.

Note that the present invention can also be effectively applied to an ultrasonic transducer having a large number of transducer elements, for example, a multi-element transducer such as a phased array, a linear array, or an annular array. Of course.

Further, the metal case described here does not necessarily have to be a "box" body, and a metal frame as shown at 25 in FIG. It may be provided in a ring shape.

Furthermore, as schematically shown in FIG. 4, when soldering the back and front side electrodes 32, 33 to the piezoelectric film 31, a ring-shaped metal frame 35 similar to that shown in FIG. can be produced,
This embodiment is often used as a hydrophone operated underwater or as various other electroacoustic transducers.

(Effects of the Invention) According to the configuration of the electroacoustic transducer according to the present invention as described above, the surface additional film 4 is firmly soldered to the conductive metal case 5 via the front side electrode 3 provided on the upper surface thereof. and the surface added film 4 and the electrode 3
It is mechanically stable due to its strong adhesion to
Therefore, as long as the surface-added film 4 has excellent water resistance, it can be used as a transducer with extremely high water resistance, and the reliability of transducers using polymer piezoelectric films, which had been a concern in the past, can be improved. be enhanced.

[Brief explanation of the drawing]

FIG. 1 is a diagram schematically showing an ultrasonic transducer having a structure according to the present invention, FIG. 2 is a longitudinal sectional view showing an embodiment of the ultrasonic transducer according to the present invention, and FIG. 2 is a schematic diagram showing an ultrasonic transducer in which the metal case is shaped like a ring, and FIG. 4 shows another embodiment of the present invention, in which the vibrator portion of the electroacoustic transducer is enlarged. FIG. 1: Polymer piezoelectric film, 3: Front side electrode, 4: Surface additional film, 5: Metal case, 8: Conductive wire.

Claims (1)

[Claims] 1. An electroacoustic transducer using a polymer piezoelectric film, characterized in that it has an additional layer soldered to a metal case.