JPS58177639A - Production of ultrasonic probe - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] The present invention irradiates an object such as a human body with an ultrasonic pulse,
Regarding the manufacturing method of ultrasound probes used in ultrasound diagnostic equipment using the so-called pulse echo method, which displays reflected pulses from inside the specimen on a cathode ray tube. In conventional ultrasound probes, the piezoelectric material and the specimen A structure in which an acoustic matching layer is formed on a piezoelectric material is used to better match the acoustic impedance of the piezoelectric material and to widen the characteristics. 1 shows a general configuration of an ultrasound probe with a double matching layer. In FIG. 1, a piezoelectric ceramic,
Electrodes 2 are formed on opposing plates of a piezoelectric body 1 such as a piezoelectric crystal by plating, vapor deposition, etc. O4 is made of glass, resin, a mixture of resin and inorganic materials, etc., bonded or coated and hardened. The first acoustic matching layer 05 formed on the top is a second acoustic matching layer formed by depositing or coating a resin or a mixture of a resin and an inorganic material on the acoustic matching layer for 1 km and curing it. 6 is formed at a position opposite to the acoustic matching layer.

3 is the object 0 Pulse echo @ 1, short or strong jM 4- m
Transmitting and receiving Hals is important for resolution and JIILI direct china clay.For this reason, the performance of ultrasonic waves and probes is important, such as broadband with excellent pulse response, low loss, and low ripple. 0 For this reason, an appropriate configuration of the blue tatami matching 14.5 and the back cover layer 6 in Figure 1 is required. The acoustic matching layer 4゜5 of the lltzlm is used to match the acoustic impedance of the two layers in order to efficiently transmit and receive ultrasonic waves between the piezoelectric body 1 and the subject 3, and is a general Kxl*tatami matching layer. Layer 4 is piezoelectric material 1
A device with a smaller acoustic impedance than the second
The acoustic matching layer 5 has a smaller acoustic impedance than the acoustic matching layer 4, and a layer with a larger acoustic impedance than the subject 3 is used. A general method for configuring these acoustic matching layers is to use a piezoelectric material. A glass plate processed to a thickness of 1/4 wavelength of the wavelength corresponding to the resonant frequency is glued onto the piezoelectric body, and a plastic sheet similarly processed to a thickness of 1/4 wavelength is roughly placed on the glass plate. The method was to apply a resin to a glass plate that was adhered to a piezoelectric material or to harden it, and then adjust the thickness to a quarter wavelength by polishing. The thickness is determined by the wavelength λ-v/f* at the frequency fo used from the sound velocity of glass, resin, etc.
It was decided to calculate the wavelength and make it a quarter of that, but it was difficult to obtain an accurate quarter wavelength due to the influence of the adhesive layer and variations in sound speed due to the curing conditions of the resin. there were. Further, since a glass plate is not necessarily an ideal material for the matching layer, the sound input tIt probe having the combined layer made in this manner has a problem with regard to pulse response.

On the other hand, in order to avoid the influence of the adhesive layer and to form an ideal acoustic impedance matching layer, there is a method of coating and curing a mixture of resin and inorganic material on the piezoelectric material, but in this case, the layer is uneven due to precipitation of the inorganic material. Therefore, the speed of sound cannot be determined.For this reason, the conventional method has not been able to form an accurate 1/4 wavelength matching layer.

The purpose of the present invention is to eliminate these drawbacks of the prior art, form an acoustic matching layer with an appropriate acoustic impedance density and an appropriate thickness, and provide a method for manufacturing an ultrasonic probe with excellent pulse response. It is about providing. The method for manufacturing an ultrasound probe of the present invention is a method for manufacturing an ultrasound probe having an acoustic matching layer on a piezoelectric material.
-2 layers (N -1, 2, 3, ......) sound wm combination layer (on the piezoelectric body in case of N-1) M2N-1st layer sound 41111i combination layer , and this piezoelectric body and 2
Measure the resonance frequencies of the N-order mode and N+1-order mode of a composite vibrator consisting of N-1 acoustic matching layers, and check that the absolute value of the difference between these values and the value of the fundamental mode resonance frequency of the piezoelectric material alone is equal. a step of adjusting the thickness of the 2N-1 acoustic matching layer, and a step of adjusting the thickness of the 2N-1 acoustic matching layer so that the 2N-
A 2Nth acoustic matching layer is formed on the 1st acoustic matching layer, and the resonant frequency of the N+1st mode of the composite vibrator consisting of this piezoelectric material and 2N acoustic matching layers is measured, and this value and the piezoelectric The present invention is characterized in that it includes a step of adjusting the thickness of the second Nth acoustic matching layer in kIIrJ so that the values of the fundamental mode resonance frequencies of the individual bodies coincide.

The principle of the present invention will be explained below. Generally, when a layer of a material with lower acoustic impedance than the piezoelectric material is provided on the piezoelectric material, the piezoelectric material and this layer form a composite vibrator, and the resonant frequency close to the resonance frequency of the fundamental mode of the piezoelectric material alone is generated. Two modes are available. Figure 2 shows this situation, and shows the relationship between the thickness of the layer provided on the piezoelectric body (hereinafter referred to as the first acoustic matching layer) and the resonance frequencies of the fundamental mode and secondary mode of the composite vibrator. The calculated thickness of the first tuning layer is 1/4 wavelength at the resonant frequency of the piezoelectric material, and the frequency is normalized by the resonant frequency of the piezoelectric material. Here, as a piezoelectric material, the acoustic impedance is v! i degree 3SX10' to 4I/male friend,
When a piezoelectric ceramic with an electromechanical coupling coefficient of 50.0 x is used as the first acoustic matching layer, the acoustic impedance density is 6.6 x
The zero calculation method assuming a material of 10'Kp/l/.filtration was performed using a Mason equivalent circuit for the piezoelectric ceramic part.

From Figure 2, when the thickness of the first acoustic matching layer is a quarter wavelength of the wavelength corresponding to the resonant frequency of the piezoelectric material, the resonant frequencies of the fundamental mode and the secondary mode, and the fundamental resonant frequency of the piezoelectric ceramic alone. The absolute value of the difference between them will be equal to 0.Using this fact, conversely, in order to form the first matching layer with the thickness of the quarter wavelength, the resonant frequency must be adjusted when adjusting the thickness of the first matching layer. The resonant frequencies of the fundamental mode and the secondary mode may be adjusted so that their absolute values are equal to each other in terms of the difference from the fundamental mode resonant frequency of the piezoelectric ceramic alone. If a layer of material with a rougher acoustic impedance density than the first tuning layer is provided on the first tuning layer whose thickness is adjusted to a quarter wavelength, a composite layer with three adjacent resonant modes will be created. Becomes a vibrator. 3rd @
shows this situation, and the thickness of the layer provided on the 1f'11m1 composite layer (hereinafter referred to as the second acoustic matching layer) and the resonance of the fundamental mode, secondary mode, and tertiary mode of the composite vibrator. The relationship between the frequencies is calculated as 0 where the piezoelectric material,
The material of the first acoustic matching layer is the same as the calculation in Figure 2. The material of the second acoustic matching layer is the acoustic impedance density of 2.4
10＠] cf/yl・Assuming the material of cod, the first tuning layer has a thickness of 1/4 wavelength. From Figure 3, the second
When the thickness of the phonetic matching layer becomes a quarter wavelength of the wavelength corresponding to the resonant frequency of the piezoelectric material, the resonant frequency of the secondary mode coincides with the fundamental resonant frequency of the piezoelectric ceramic alone.

From this, the second note! #To increase the thickness of the matching skin to a thickness of 1/4 wavelength, it is sufficient to measure the resonance frequency of the secondary mode and adjust this value so that it matches the fundamental mode resonance frequency of the piezoelectric material alone. To form one more acoustic matching layer by applying this method, first provide two acoustic matching layers each having a thickness of 1/4 wavelength, then provide a third acoustic matching layer, and reduce the thickness to 1/4. To adjust the wavelength, the resonant frequencies of the secondary mode and the tertiary mode may be measured and adjusted so that the absolute values of the differences between these caps and the values of the fundamental mode resonant frequencies of the piezoelectric body alone are equal. Also, to provide a II4 tone matching layer on the surface and reduce the thickness to 1/4 wavelength cg*m,
The resonant frequency of the tertiary mode may be measured and adjusted so that this value matches the fundamental mode resonant frequency of the piezoelectric body alone. The acoustic matching layers of Zaraani Hen G, 86... can be adjusted in the same way, and if these are generalized, 2N
-2N- layers (N-1, l 3-......) on the acoustic matching layer (on the piezoelectric body when N-1)
When forming one acoustic matching layer, measure the Nth and N+1st resonance frequencies of a composite vibrator consisting of 2N-1 acoustic matching layers and a piezoelectric material, and calculate these values and the fundamental resonance frequency of the piezoelectric material alone. 2N-1fii so that the absolute value of the difference between
In order to adjust the thickness of the 1 acoustic matching layer and further form a 2N layer of sound IN1 on top of the 2N-1 acoustic matching layer, a composite vibration consisting of the 2N acoustic matching layer and the piezoelectric material is used. The thickness of the 2Nth acoustic mating layer may be adjusted so that the N+1-order resonance frequency of the child and the fundamental -1 frequency of the piezoelectric phase are equal.

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

Note that this embodiment uses a 2MI similar to the ultrasonic probe in Fig. 1.
This configuration has an acoustic matching layer of. A piezoelectric ceramic based on zircon and lead titanate was used as a piezoelectric body.
A disc-shaped material with a thickness of 1.0 dew was used. Silver electrodes with a thickness of 10 .mu.m were coated on both sides of the substrate and baked, and a voltage of 4 KV was applied for 1 hour in silicone oil at 100.degree. C. to perform polarization treatment. A mixture of epoxy resin and powdered glass was applied to one side of the piezoelectric ceramic and cured by heating.

After leaving this at room temperature for one day, the resonant frequency was measured and the resin layer was polished. A different type of epoxy resin having an acoustic impedance density lower than that of the resin layer was coated on this resin layer, which was adjusted to have 0, and then heated and cured. After leaving this at room temperature for a day, I polished it while adding fIII to the resonance frequency, and then added epoxy resin to the joint so that the resonance frequency of the secondary wave #: matched the fundamental resonance frequency of the piezoelectric material alone. The back surface negative 1hJIi& made of 1hJIi& was bonded to the acoustic matching layer and the opposite side.

Figure 84 shows the input admittance characteristics of HonjitsujiiN's ultrasonic probe when loading aquatic fish. The conventional IIA probe that adopted the 21-coil layer did not achieve the single-peak resonance characteristic shown in Figure 4. This was due to a problem with the configuration of the acoustic matching layer, and the manufacturing method of the present invention The zero-single resonance characteristic, which became possible for the first time through this method, has the advantage of being easy to match with the circuit, and by using a series resistor and coil, matching can be achieved over the entire band. O that can be done
Therefore, in-band ripples due to mismatching with the electrical circuit do not occur as with conventional probes with a z1g matching layer.
iGhE shows this, and the insertion loss of the probe of this example was determined by the reflected wave from an aluminum plate at a water depth of 20 cIIM. It can be seen that low ripple has been achieved. This is because the acoustic matching layer is appropriately configured by the manufacturing method of the present invention.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram of an ultrasonic probe. In FIG. 1, l... is a piezoelectric body, 2 is an electrode, 3 is a subject, 4 is a first acoustic matching layer, and 5 is a second acoustic matching layer. FIG. 2 is a diagram showing the relationship between the thickness of the first acoustic matching layer and the resonant frequency. In FIG. 2, 1 is a fundamental mode, 2 is a secondary mode, and FIG. 3 is a diagram showing the relationship between the thickness of the second acoustic matching layer and the resonant frequency. In FIG. 3, 1 is a fundamental mode, 2 is a secondary mode, 3 is a tertiary mode, and FIG. 4 is an input atomic characteristic diagram of an embodiment of the present invention. In Figure 4, 1 is conductance, 2 is susceptance 1 81 Figure 2 Figure 3 Standardization 2 Matching 4s Figure 4 1.0 2.0
30 laps j skin banquet [MH2]

Claims (1)

[Claims] Method for manufacturing an ultrasonic probe in which an acoustic matching layer is formed on a piezoelectric material
．． A K2N-IMith acoustic matching layer is formed on the acoustic matching layer (I &...) (on the piezoelectric body in the case of N-1), and the sound lIP! of this piezoelectric body and 2N-IJil is formed. Ii-
The resonant frequencies of the 8th mode and the N+1st mode of the composite vibrator composed of laminated layers are adjusted, and the absolute values of the differences between these koji and the fundamental mode resonant frequency values of the piezoelectric material alone are equalized. A step of adjusting the thickness of the 2N-1 acoustic matching layer, forming a 2NNk-th acoustic matching layer on the 2N-1 acoustic matching layer whose thickness has been adjusted, and forming the 2N-1 acoustic matching layer on the piezoelectric material and the 2N The resonance frequency of the N+1st mode of the composite vibrator made of the acoustic matching layer is adjusted, and the second N
Method 0 for manufacturing an ultrasonic probe characterized by having a step of adjusting the thickness of the M-th sound w plush layer