Preparation method of ultrasonic sensor matching layer

Abstract

The invention relates to a preparation method of a matching layer of an ultrasonic sensor, which is characterized in that when the matching layer of the ultrasonic sensor is manufactured, the matching layer is directly formed on the surface of a piezoelectric wafer, the thickness of the matching layer can be conveniently changed, and the application effect of the matching layers with different thicknesses can be tested, so that the optimal sound matching performance can be obtained. The matching layer mixture is formed by adding a filler into epoxy resin glue, the filler is metal powder, and the ratio of the epoxy resin to the metal powder is 1: 0.5.

Description

Technical Field

[0001] The invention relates to the technical field of ultrasonic sensor material manufacturing, and in particular to a method for preparing a matching layer of an ultrasonic sensor. Background Art

[0002] In ultrasonic sensor applications, the piezoelectric chip is used as the first medium and the load is used as the second medium. The load is usually water or air during the application process. The acoustic impedance of the piezoelectric chip and the load is quite different. At this time, the reflection coefficient is large and the projection coefficient is small. Most of the sound waves are reflected and only a small part of the sound waves are projected. The significant difference in impedance will not only reduce the interface projection coefficient, but also make the piezoelectric element resonate with a high Q value, narrow frequency band and long pulse, which will seriously affect the transmitting and receiving sensitivity of the probe.

[0003] In order to overcome this shortcoming, a medium layer is inserted between the piezoelectric chip and the load to gradually change the acoustic impedance, improve the acoustic wave projection rate and widen the frequency band. This medium layer is called a matching layer. In the application, it is necessary to select a suitable acoustic impedance material as the matching layer. Theoretically, the thickness of the matching layer is 1 / 4 wavelength, and there will be a certain deviation that needs to be adjusted in actual application. Therefore, it is urgent to design a preparation scheme to obtain the best acoustic matching performance ultrasonic sensor. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a method for preparing a matching layer of an ultrasonic sensor. When manufacturing the matching layer of the ultrasonic sensor, the matching layer is directly formed on the surface of a piezoelectric wafer, comprising the following steps:

[0005] Step S1: clean the negative electrode surface of the piezoelectric wafer pasted with the matching layer;

[0006] Step S2: welding a welding point on the edge of the negative electrode surface of the piezoelectric wafer, wherein the welding point is higher than the theoretical thickness of the matching layer;

[0007] Step S3: stick double-sided tape on the flat plate of the experimental table, and stick the piezoelectric chip on the double-sided tape to fix it;

[0008] Step S4: preparing a matching layer mixture using epoxy resin and filler, stirring evenly and then degassing by vacuum;

[0009] Step S5: drip the prepared mixture onto the piezoelectric chip to cover the solder joints. The matching layer mixture is relatively viscous and will not flow down due to tension.

[0010] Step S6: Place the plate in a 60°C constant temperature oven for heating, keep warm for 4 hours and then close it. Take it out after 12 hours. At this time, the matching layer on the piezoelectric chip has been solidified.

[0011] Step S7: placing a flat metal plate into a high-temperature oven for heating, and placing the wax on the metal plate to be heated and melted;

[0012] Step S8: Take out the metal plate, stick the piezoelectric chip on the metal plate with the matching layer facing upward, and after cooling, the wax solidifies and the piezoelectric chip is fixed;

[0013] Step S9: fix the metal plate on a surface grinder, grind the matching layer to various thicknesses, and then heat the metal plate to remove the piezoelectric wafer to test performance;

[0014] Step S10: Verification, repeating steps S6 to S9, testing the performance changes under conditions of matching layers with different thicknesses, so as to find the matching layer with the best effect.

[0015] In one embodiment of the present invention, the theoretical thickness of the matching layer in step S2 is λ / 4, where λ is the wavelength.

[0016] In one embodiment of the present invention, the matching layer mixture in step S4 is prepared by adding filler to epoxy resin glue, wherein the filler is metal powder, and the ratio of epoxy resin to metal powder is 1:0.5.

[0017] In one embodiment of the present invention, when used simultaneously, epoxy resin and metal powder are prepared by weight, stirred sufficiently, and then placed in a vacuum environment to remove air bubbles.

[0018] In one embodiment of the present invention, the negative electrode surface of the piezoelectric chip is connected with a welding point, and the other end of the piezoelectric chip is adhered to the metal plate through wax after cooling.

[0019] The above technical solution of the present invention has the following advantages over the prior art: the method for preparing the ultrasonic sensor matching layer of the present invention directly forms the matching layer on the surface of the piezoelectric chip when manufacturing the ultrasonic sensor matching layer, and can conveniently change the thickness of the matching layer, and test the application effects of matching layers of different thicknesses to obtain the best acoustic matching performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to make the contents of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments of the present invention in conjunction with the accompanying drawings.

[0021] Figure 1 It is a schematic diagram of the structure of the matching layer and the piezoelectric wafer obtained after grinding in the present invention;

[0022] Figure 2 It is a diagram showing the relationship between the thickness of the multiple sets of matching layers and the conductivity values ​​in the present invention.

[0023] As shown in the figure, 1. piezoelectric chip, 2. solder joint, 3. matching layer, 4. metal plate, 5. wax. DETAILED DESCRIPTION

[0024] This embodiment provides a method for preparing a matching layer of an ultrasonic sensor, comprising the following steps:

[0025] Step S1: clean the negative electrode surface of the piezoelectric wafer 1 pasted with the matching layer 3;

[0026] Step S2: welding a welding point 2 on the edge of the negative electrode surface of the piezoelectric wafer 1, wherein the welding point 2 is higher than the theoretical thickness of the matching layer 3;

[0027] Step S3: stick double-sided tape on the flat plate of the experimental table, and stick the piezoelectric chip 1 on the double-sided tape to fix it;

[0028] Step S4: Use epoxy resin and filler to prepare a matching layer 3 mixture, stir evenly and then vacuum degas; the matching layer 3 mixture is to add filler to epoxy resin glue, wherein the filler is metal powder, and the ratio of epoxy resin to metal powder is 1:0.5. When using them together, prepare epoxy resin and metal powder by weight, stir them thoroughly and put them in a vacuum environment to remove bubbles.

[0029] Step S5: dripping the prepared mixture onto the piezoelectric chip 1 to cover the solder joint 2;

[0030] Step S6: putting the plate into a 60°C constant temperature oven for heating, keeping the temperature for 4 hours and then closing it. It can be taken out after 12 hours. At this time, the matching layer 3 on the piezoelectric chip 1 has been solidified;

[0031] Step S7: putting a flat metal plate 4 into a high-temperature oven for heating, and placing the wax 5 on the metal plate 4 to be melted by the heat;

[0032] Step S8: Take out the metal plate 4, stick the piezoelectric chip 1 on the metal plate 4, with the matching layer 3 facing upwards, and after cooling, the wax 5 solidifies, and the piezoelectric chip 1 is fixed accordingly;

[0033] Step S9: fix the metal plate 4 on a surface grinder, grind the matching layer 3 to various thicknesses, heat the metal plate 4 and remove the piezoelectric chip 1 to test its performance;

[0034] Step S10: Verification, repeating steps S6 to S9, testing the performance changes under conditions of different thicknesses of the matching layer 3, so as to find the matching layer 3 with the best effect.

[0035] In step S2 , the theoretical thickness of the matching layer 3 is λ / 4, where λ is the wavelength.

[0036] like Figure 1 As shown, a welding spot 2 is provided on the negative electrode surface of the piezoelectric chip 1, and the other end of the piezoelectric chip 1 is bonded to the metal plate 4 through wax 5 after cooling.

[0037] The preparation method described in this embodiment can quickly and easily obtain matching layers of different thicknesses when making an ultrasonic sensor matching layer, and perform operation tests on the same piezoelectric wafer. The test data information is more effective. By statistically analyzing these data, a curve of the ultrasonic sensor performance parameters changing with the matching layer thickness can be obtained, thereby analyzing what thickness should be selected for the matching layer in actual applications.

[0038] Specifically, Figure 2 The test results shown in the figure show that when the thickness of the matching layer is 0.95 mm, the conductivity at the concave part of the conductivity curve is approximately half of the highest conductivity value. At this time, the bandwidth is the largest and the effect is the best.

[0039] Obviously, the above embodiments are merely examples for clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the protection scope of the invention.

Claims

1. A method for preparing a matching layer for an ultrasonic sensor, wherein the matching layer (3) is directly formed on the surface of a piezoelectric wafer (1) when preparing the matching layer (3) for the ultrasonic sensor, and wherein: The steps include: Step S1: Cleaning the negative electrode surface of the piezoelectric wafer (1) where the matching layer (3) is attached; Step S2: welding a welding point (2) at the edge of the negative electrode surface of the piezoelectric chip (1), wherein the welding point (2) is higher than the theoretical thickness of the matching layer (3); Step S3: stick double-sided tape on the flat plate of the experimental table, and stick the piezoelectric chip (1) on the double-sided tape to fix it; Step S4: using epoxy resin and filler to prepare a matching layer (3) mixture, stirring evenly and then vacuum degassing; Step S5: dripping the prepared mixture onto the piezoelectric chip (1) to cover the solder joint (2); Step S6: placing the plate in a 60° C. constant temperature oven for heating, keeping the temperature for 4 hours and then closing the oven. The plate can be taken out after 12 hours. At this time, the matching layer (3) on the piezoelectric chip (1) has been solidified. Step S7: placing a flat metal plate (4) into a high-temperature oven for heating, and placing the wax (5) on the metal plate (4) to melt under the heat; Step S8: Take out the metal plate (4), stick the piezoelectric chip (1) on the metal plate (4), with the matching layer (3) facing upwards, and after cooling, the wax (5) solidifies, and the piezoelectric chip (1) is fixed accordingly; Step S9: fix the metal plate (4) on a surface grinder, grind the matching layer (3) to various thicknesses, heat the metal plate (4) and remove the piezoelectric chip (1) to test its performance; Step S10: Verification, repeating steps S6 to S9, testing the performance changes under conditions of different thicknesses of the matching layer (3), so as to find the matching layer (3) with the best effect.

2. The method for preparing the matching layer of an ultrasonic sensor according to claim 1, characterized in that: The theoretical thickness of the matching layer (3) in step S2 is λ / 4, where λ is the wavelength.

3. The method for preparing the matching layer of an ultrasonic sensor according to claim 1, characterized in that: The mixture of the matching layer (3) in step S4 is prepared by adding filler to epoxy resin glue, wherein the filler is metal powder, and the ratio of epoxy resin to metal powder is 1:0.

5.

4. The method for preparing the matching layer of an ultrasonic sensor according to claim 3, characterized in that: When using at the same time, mix the epoxy resin and metal powder by weight, stir them thoroughly, and then put them in a vacuum environment to remove bubbles.

5. The method for preparing the matching layer of an ultrasonic sensor according to claim 1, characterized in that: The negative electrode surface of the piezoelectric chip (1) is provided with a welding point (2), and the other end of the piezoelectric chip (1) is bonded to the metal plate (4) through wax (5) after cooling.

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