Ultrasonic transducer matching layer material and preparation method therefor

Abstract

The present invention relates to the technical field of ultrasonic transducer materials, and in particular to an ultrasonic transducer matching layer material and a preparation method therefor. The technical solution is adopted: the ultrasonic transducer matching layer material comprises the following components in parts by weight: 15-34 parts of a phenolic resin, 50-92 parts of aluminum oxide, 3-17 parts of graphite, 1-16 parts of a carbon fiber, 1.5-5 parts of a curing agent, and 0.5-5 parts of a lubricant. The raw material powder is mixed and subjected to hot press molding to prepare an ultrasonic transducer matching layer material. The present invention has the following beneficial effects: aluminum oxide is adopted, specifically, acicular aluminum oxide is mixed with a phenolic resin to prepare a material having high acoustic impedance rate and low acoustic attenuation, so that the material cost and the processing difficulty are reduced; graphite serves as a good heat-conducting conductor, so that the heat conductivity of the material can be improved; calcium stearate or zinc stearate is used as a lubricant, so that the overall forming effect of the matching layer material can be effectively improved, and the product percent of pass is increased; and the carbon fiber can effectively improve the overall stability of the matching layer material and improve the acoustic performance and percent of pass of the product.

Description

Ultrasonic transducer matching layer material and preparation method thereof Technical Field

[0001] The present invention relates to the technical field of ultrasonic transducer materials, and in particular to an ultrasonic transducer matching layer material and a preparation method thereof. Background Art

[0002] When an ultrasonic transducer is in use, the acoustic characteristic impedance of human soft tissue is approximately 1.5×106 Pa·s / m, while the acoustic characteristic impedance of a piezoelectric ceramic can be as high as 38×106 Pa·s / m. This significant difference between the two makes it difficult to detect an ultrasonic echo. If the piezoelectric ceramic chip directly contacts the human body, the piezoelectric ceramic will radiate ultrasonic waves into the soft tissue. Due to the significant impedance difference between the two, the reflection coefficient is large and the transmission coefficient is small. As a result, most of the sound waves are reflected, and only a small portion is transmitted. This makes it impossible to obtain ultrasonic echoes, affecting the final imaging. To overcome this shortcoming, a dielectric layer, known as a matching layer, is inserted between the piezoelectric ceramic chip and the human body. This gradually changes the acoustic characteristic impedance between the piezoelectric ceramic chip and the human body, optimizing the imaging effect. Therefore, the quality of the matching layer greatly affects the overall performance of the ultrasonic transducer. Currently, most matching layers in ultrasonic transducers use single-layer, double-layer or triple-layer matching layers, and a few use matching layers with more than three layers. Among the matching layers, the matching layer connected to the piezoelectric ceramic chip is the first matching layer. Since the acoustic characteristic impedance of the piezoelectric ceramic chip is large, the first matching layer connected to the piezoelectric ceramic chip requires a higher acoustic characteristic impedance, and the material used to prepare the matching layer requires a higher acoustic impedance ratio.

[0003] Currently, the most commonly used first matching layer is made of epoxy resin and tungsten powder. Evenly distributing tungsten powder in the epoxy resin creates a material with a high acoustic impedance coefficient, resulting in a first matching layer with a high acoustic characteristic impedance. However, the high price of tungsten powder leads to a high overall cost. Furthermore, this matching layer suffers from a high attenuation rate. This excessively attenuates high-frequency sound waves, which have poor penetration, reducing the sensitivity of the ultrasonic transducer and affecting imaging. Furthermore, due to the high density of tungsten powder, it tends to sink to the bottom of the epoxy resin during processing, resulting in uneven dispersion and causing severe warping and high defect rates after molding. Furthermore, due to the uneven dispersion of tungsten powder in the epoxy resin, even with a high thermal conductivity of 173 W / m*K, it is difficult to form a thermal path in this system. Actual measured thermal conductivity is only around 2.6 W / m*K, demonstrating a poor thermal path formation. The poor thermal conductivity of the matching layer can lead to excessive heat accumulation in the probe after prolonged operation, damaging components and reducing the probe's lifespan. Summary of the Invention

[0004] The purpose of the present invention is to provide an ultrasonic transducer matching layer material and a preparation method thereof, specifically to provide an ultrasonic transducer matching layer material and a preparation method thereof with low material cost, high acoustic impedance, good thermal conductivity and stable acoustic performance.

[0005] To achieve the above-mentioned purpose, the present invention adopts the following technical solution: an ultrasonic transducer matching layer material, comprising the following components in parts by weight: 15 to 34 parts of phenolic resin, 50 to 92 parts of aluminum oxide, 3 to 17 parts of graphite, 1 to 16 parts of carbon fiber, 1.5 to 5 parts of curing agent and 0.5 to 5 parts of lubricant.

[0006] Specifically, the phenolic resin is a thermoplastic novolac resin.

[0007] Specifically, the curing agent is hexamethylenetetramine.

[0008] Specifically, the lubricant is calcium stearate or zinc stearate.

[0009] A method for preparing a matching layer material for an ultrasonic transducer comprises the following steps:

[0010] S01. Weigh the following raw materials in parts by weight: 15-34 parts of phenolic resin, 50-92 parts of aluminum oxide, 3-17 parts of graphite, 1-16 parts of carbon fiber, 1.5-5 parts of curing agent, and 0.5-5 parts of lubricant.

[0011] S02. Crush the phenolic resin in the raw materials into powder, and then mix it evenly with other powdered raw materials.

[0012] S03, putting the evenly mixed powdered raw materials into an internal mixer for internal mixing.

[0013] S04. Cooling the powdered raw material after the internal mixing, and then placing it in a mold and performing hot pressing molding in a flat vulcanizer to obtain a sheet.

[0014] S05. Grind the sheet to a set thickness to obtain a matching layer for the ultrasonic transducer.

[0015] Specifically, the phenolic resin in step S01 is thermoplastic phenolic resin.

[0016] Specifically, in step S01, the curing agent is hexamethylenetetramine.

[0017] Specifically, in step S01 , the aluminum oxide is needle-shaped aluminum oxide powder with a particle size of 3 to 4 μm.

[0018] Specifically, the lubricant in step S01 is calcium stearate or zinc stearate.

[0019] Specifically, in step S04, when hot pressing is performed using a flat-plate vulcanizing machine, the flat-plate vulcanizing machine is set to automatic mode, which specifically includes the following steps:

[0020] S41, pre-pressing, time 6~10min, pressure 15~20MPa.

[0021] S42. Exhaust 5 to 15 times, each time for 10 seconds.

[0022] S43, pressurization, time 60~90min, pressure 20~25MPa.

[0023] S44. Cool down to 30~50 degrees Celsius.

[0024] The beneficial effects of the present invention are as follows: by using alumina, specifically needle-shaped alumina, mixed with phenolic resin, a material with higher acoustic impedance and lower acoustic attenuation is obtained, while reducing material cost and processing difficulty; combining graphite as a good thermal conductor can improve the thermal conductivity of the material; calcium stearate or zinc stearate as a lubricant can effectively improve the overall molding effect of the matching layer material and improve the product qualification rate; at the same time, carbon fiber can effectively improve the overall stability of the matching layer material, improve the acoustic performance and qualification rate of the product. DETAILED DESCRIPTION

[0025] Example 1, a matching layer material for an ultrasonic transducer, comprises the following components, in parts by weight: 20 parts phenolic resin, 55 parts aluminum oxide, 6 parts graphite, 10 parts carbon fiber, 2 parts curing agent, and 0.5 parts lubricant. The phenolic resin is thermoplastic novolac; the curing agent is hexamethylenetetramine; and the lubricant is calcium stearate or zinc stearate.

[0026] This embodiment also provides a method for preparing an ultrasonic transducer matching layer material, comprising the following steps:

[0027] S01. Weigh the following raw materials in parts by weight: 20 parts of phenolic resin, 55 parts of aluminum oxide, 6 parts of graphite, 10 parts of carbon fiber, 2 parts of curing agent, and 0.5 parts of lubricant.

[0028] S02. Crush the phenolic resin in the raw materials into powder, and then mix it evenly with other powdered raw materials.

[0029] S03. Put the uniformly mixed powdered raw materials into an internal mixer for internal mixing. During internal mixing, the internal mixer temperature is set to 110° C., the speed is 30 rpm, and the mixing time is 30 minutes.

[0030] S04. Cooling the powdered raw material after the internal mixing, and then placing it in a mold and performing hot pressing molding in a flat vulcanizer to obtain a sheet.

[0031] S05. Grind the sheet to a set thickness to obtain a matching layer for the ultrasonic transducer.

[0032] In step S01, the phenolic resin is thermoplastic phenolic resin; the curing agent is hexamethylenetetramine; the alumina is needle-shaped alumina powder with a particle size of 3 to 4 μm; the lubricant in step S01 is calcium stearate or zinc stearate; the graphite is 1250 mesh micropowder graphite with a particle size of approximately 10 μm; the single fiber diameter of the carbon fiber is 7 μm and the average length is 50 μm.

[0033] Specifically, in step S04, when hot pressing is performed using a flat-plate vulcanizing machine, the flat-plate vulcanizing machine is set to automatic mode, which specifically includes the following steps:

[0034] S41, pre-pressing, time 8min, pressure 17MPa.

[0035] S42, exhaust 10 times, each time for 10 seconds.

[0036] S43, pressurization, time 75min, pressure 20MPa.

[0037] S44. Cool down to 40 degrees Celsius.

[0038] Example 2, a matching layer material for an ultrasonic transducer, comprises the following components, in parts by weight: 20 parts phenolic resin, 75 parts aluminum oxide, 6 parts graphite, 10 parts carbon fiber, 2 parts curing agent, and 0.5 parts lubricant. The phenolic resin is thermoplastic novolac; the curing agent is hexamethylenetetramine; and the lubricant is calcium stearate or zinc stearate.

[0039] This embodiment also provides a method for preparing an ultrasonic transducer matching layer material, comprising the following steps:

[0040] S01. Weigh the following raw materials in parts by weight: 20 parts of phenolic resin, 75 parts of aluminum oxide, 6 parts of graphite, 10 parts of carbon fiber, 2 parts of curing agent, and 0.5 parts of lubricant.

[0041] S02. Crush the phenolic resin in the raw materials into powder, and then mix it evenly with other powdered raw materials.

[0042] S03. Put the uniformly mixed powdered raw materials into an internal mixer for internal mixing. During internal mixing, the internal mixer temperature is set to 110° C., the speed is 30 rpm, and the mixing time is 30 minutes.

[0043] S04. Cooling the powdered raw material after the internal mixing, and then placing it in a mold and performing hot pressing molding in a flat vulcanizer to obtain a sheet.

[0044] S05. Grind the sheet to a set thickness to obtain a matching layer for the ultrasonic transducer.

[0045] In step S01, the phenolic resin is thermoplastic phenolic resin; the curing agent is hexamethylenetetramine; the alumina is needle-shaped alumina powder with a particle size of 3 to 4 μm; the lubricant in step S01 is calcium stearate or zinc stearate; the graphite is 1250 mesh micropowder graphite with a particle size of approximately 10 μm; the single fiber diameter of the carbon fiber is 7 μm and the average length is 50 μm.

[0046] Specifically, in step S04, when hot pressing is performed using a flat-plate vulcanizing machine, the flat-plate vulcanizing machine is set to automatic mode, which specifically includes the following steps:

[0047] S41, pre-pressing, time 8min, pressure 17MPa.

[0048] S42, exhaust 10 times, each time for 10 seconds.

[0049] S43, pressurization, time 75min, pressure 20MPa.

[0050] S44. Cool down to 40 degrees Celsius.

[0051] Example 3, a matching layer material for an ultrasonic transducer, comprises the following components, in parts by weight: 20 parts phenolic resin, 90 parts aluminum oxide, 6 parts graphite, 10 parts carbon fiber, 2 parts curing agent, and 0.5 parts lubricant. The phenolic resin is thermoplastic novolac; the curing agent is hexamethylenetetramine; and the lubricant is calcium stearate or zinc stearate.

[0052] This embodiment also provides a method for preparing an ultrasonic transducer matching layer material, comprising the following steps:

[0053] S01. Weigh the following raw materials in parts by weight: 20 parts of phenolic resin, 90 parts of aluminum oxide, 6 parts of graphite, 10 parts of carbon fiber, 2 parts of curing agent, and 0.5 parts of lubricant.

[0054] S02. Crush the phenolic resin in the raw materials into powder, and then mix it evenly with other powdered raw materials.

[0055] S03. Put the uniformly mixed powdered raw materials into an internal mixer for internal mixing. During internal mixing, the internal mixer temperature is set to 110° C., the speed is 30 rpm, and the mixing time is 30 minutes.

[0056] S04. Cooling the powdered raw material after the internal mixing, and then placing it in a mold and performing hot pressing molding in a flat vulcanizer to obtain a sheet.

[0057] S05. Grind the sheet to a set thickness to obtain a matching layer for the ultrasonic transducer.

[0058] In step S01, the phenolic resin is thermoplastic phenolic resin; the curing agent is hexamethylenetetramine; the alumina is needle-shaped alumina powder with a particle size of 3 to 4 μm; the lubricant in step S01 is calcium stearate or zinc stearate; the graphite is 1250 mesh micropowder graphite with a particle size of approximately 10 μm; the single fiber diameter of the carbon fiber is 7 μm and the average length is 50 μm.

[0059] Specifically, in step S04, when hot pressing is performed using a flat-plate vulcanizing machine, the flat-plate vulcanizing machine is set to automatic mode, which specifically includes the following steps:

[0060] S41, pre-pressing, time 8min, pressure 17MPa.

[0061] S42, exhaust 10 times, each time for 10 seconds.

[0062] S43, pressurization, time 75min, pressure 20MPa.

[0063] S44. Cool down to 40 degrees Celsius.

[0064] In this application, Examples 1-3 are used as Experimental Groups 1-3, respectively, and compared with a control group and a conventional matching layer material made from epoxy resin and tungsten powder. The raw materials used in the control group include, by weight, 33 parts phenolic resin, 90 parts aluminum oxide, 15 parts carbon fiber, 9 parts graphite, and 3 parts hexamethylenetetramine, and are prepared according to the preparation methods used in Examples 1-3. The epoxy resin and tungsten powder matching layer material is prepared by the following method: 100 parts epoxy resin E51, 140 parts tungsten powder, and 12.5 parts tetraethylenepentamine are stirred and mixed; the raw materials are then evacuated to a bubble-free state, poured onto a glass plate with a cast frame, and pressed onto another glass plate; the glass plate containing the raw materials is transferred to a fixed support and placed in an oven for curing and forming, thereby obtaining the conventional matching layer material made from epoxy resin and tungsten powder. Among them, the epoxy resin E51 is produced by Baling Petrochemical Company, with the trade name CYD-128, and is a bisphenol A type low-viscosity epoxy resin. The tungsten powder is produced by Bohuas Nano Technology (Ningbo) Co., Ltd., with the trade name Brofos-W-M500, and is a spherical tungsten powder with a particle size of 500 mesh.

[0065] Because the raw materials in the control group lacked the lubricant calcium stearate and ultimately could not be formed, the matching layer materials from experimental groups 1-3 and the existing epoxy resin + tungsten powder were uniformly ground to a thickness of 0.225 mm. Their acoustic performance was then tested. Specifically, the echo method was used to measure sound velocity, and a densitometer was used to measure density. The acoustic characteristic impedance, acoustic attenuation coefficient, and thermal conductivity were also tested. The experimental results are shown in the table below.

[0066]

[0067] According to the experimental results, compared with the existing matching layer made of epoxy resin + tungsten powder, the matching layer made by this embodiment has the characteristics of high acoustic impedance, low acoustic attenuation and high thermal conductivity, has good acoustic performance, and has a low overall material cost.

[0068] Of course, the above are only preferred embodiments of the present invention and are not intended to limit the scope of use of the present invention. Therefore, any equivalent changes based on the principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. .A matching layer material for an ultrasonic transducer, characterized in that: The composition comprises the following components in parts by weight: 15-34 parts of phenolic resin, 50-92 parts of aluminum oxide, 3-17 parts of graphite, 1-16 parts of carbon fiber, 1.5-5 parts of curing agent and 0.5-5 parts of lubricant; wherein the aluminum oxide is needle-shaped aluminum oxide powder with a particle size of 3-4 μm, the graphite is micro-powder graphite with a mesh size of 1250 and a particle size of 10 μm, and the carbon fiber is carbon fiber powder with a single filament diameter of 7 μm and an average length of 50 μm. 2..The ultrasonic transducer matching layer material according to claim 1, characterized in that: The phenolic resin is a thermoplastic phenolic resin. 3..The ultrasonic transducer matching layer material according to claim 2, characterized in that: The curing agent is hexamethylenetetramine. 4..The ultrasonic transducer matching layer material according to claim 1, characterized in that: The lubricant is calcium stearate or zinc stearate.

5. A method for preparing a matching layer material for an ultrasonic transducer, characterized in that: The steps include: S01. Weigh the following raw materials in parts by weight: 15-34 parts of phenolic resin, 50-92 parts of aluminum oxide, 3-17 parts of graphite, 1-16 parts of carbon fiber, 1.5-5 parts of curing agent and 0.5-5 parts of lubricant; wherein the aluminum oxide is needle-shaped aluminum oxide powder with a particle size of 3-4 μm, the graphite is micro-powder graphite with a mesh size of 1250 and a particle size of 10 μm, and the carbon fiber is carbon fiber powder with a single filament diameter of 7 μm and an average length of 50 μm; S02, crushing the phenolic resin in the raw materials into powder, and then stirring and mixing it with other powdered raw materials; S03, putting the uniformly mixed powdered raw materials into an internal mixer for internal mixing; S04, cooling the powdered raw material after banburying, and then placing it in a mold and performing hot pressing molding in a flat vulcanizer to obtain a sheet; S05. Grind the sheet to a set thickness to obtain a matching layer for an ultrasonic transducer. 6..The method for preparing a matching layer material for an ultrasonic transducer according to claim 5, characterized in that: The phenolic resin in step S01 is a thermoplastic phenolic resin. 7..The method for preparing a matching layer material for an ultrasonic transducer according to claim 5, characterized in that: In the step S01, the curing agent is hexamethylenetetramine.

8. The method for preparing a matching layer material for an ultrasonic transducer according to claim 5, characterized in that: The lubricant in step S01 is calcium stearate or zinc stearate.

9. The method for preparing a matching layer material for an ultrasonic transducer according to claim 5, characterized in that: In the step S04, when the flat plate vulcanizer is used for hot pressing, the flat plate vulcanizer is set to automatic mode, which specifically includes the following steps: S41, pre-pressing, time 6~10min, pressure 15~20MPa; S42, exhaust 5 to 15 times, each exhaust for 10 seconds; S43, pressurization, time 60~90min, pressure 20~25MPa; S44, cool down to 30~50 degrees Celsius.

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