Tungsten paste for ultrasonic fingerprint module and preparation method thereof

Abstract

The application discloses a kind of tungsten slurry for ultrasonic fingerprint module and preparation method thereof, belong to conductive paste technical field.The tungsten slurry for ultrasonic fingerprint module provided by the application includes the following components by mass percentage: saturated polyester 2-10%, curing agent 0.5-2%, saturated polyester modification auxiliary 0.01-0.5%, tungsten powder 80-90%, organic solvent 2-12%, dispersant 0.2-2%, coupling agent 0.5-1.2% and thixotropic agent 0.03-1.35%.The application adds saturated polyester, curing agent, saturated polyester modification auxiliary, conductive tungsten powder with particle size below 5 μm in conductive tungsten slurry, and simultaneously compound organic solvent and various auxiliary, and the obtained tungsten slurry has the advantages of curing temperature ≤100℃, high density, low thixotropy, low surface roughness, no delamination after lamination, no large size hole.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of conductive paste, and particularly relates to a tungsten paste for an ultrasonic fingerprint module and a preparation method thereof. BACKGROUND

[0002] The ultrasonic fingerprint recognition technology has become a key scheme for high-end intelligent terminal biological recognition due to the advantages of screen penetration, strong recognition ability for wet hands, high safety and the like. The core component of the ultrasonic fingerprint recognition technology is an ultrasonic fingerprint module. The ultrasonic fingerprint module transmits and receives ultrasonic signals penetrating through a screen, and constructs a fingerprint image according to the echo difference. In the system, an acoustic impedance matching layer located at the top of the sensor is crucial. The acoustic impedance matching layer effectively reduces the acoustic impedance difference between the sensor and the screen protective cover plate (such as glass), thereby maximizing the transmission and reception efficiency of the ultrasonic signals and ensuring the imaging quality.

[0003] At present, the materials commonly used for preparing the ultrasonic fingerprint module include conductive silver paste. However, the traditional conductive silver paste has the following disadvantages: 1) great cost pressure: the silver content in the silver paste accounts for more than 70%, resulting in high material cost, and the fluctuation of silver price (about 6000 yuan / kg in 2025) directly affects the overall cost of the module; 2) thermal stress risk: the traditional silver paste has relatively poor high-temperature resistance, and is prone to thermal stress between the piezoelectric layer and the substrate due to the mismatch of the thermal expansion coefficients, which may cause interface peeling or attenuation of the electro-acoustic performance in the long term; 3) serious high-frequency signal loss: as the frequency of the sensor increases, the skin effect of the silver paste in the high-frequency band (>1 GHz) will be intensified, resulting in a significant decrease in the signal transmission efficiency with the increase of the frequency, which restricts the further improvement of the performance of the module.

[0004] In view of the problems of the traditional conductive silver paste, researchers have proposed a scheme of preparing a conductive tungsten paste by filling a polymer composite material with high specific gravity tungsten powder. The tungsten powder is uniformly dispersed in an organic resin system, and a composite layer with high acoustic impedance and certain flexibility is formed after curing. However, in actual application, a very high tungsten powder filling amount is required for the existing tungsten paste to achieve high acoustic impedance, which easily leads to a dramatic increase in the viscosity of the paste, difficulty in dispersion, and easy aggregation and sedimentation in the coating or printing process, thereby causing the uniformity of the cured film layer to decrease, and regions with inconsistent acoustic performance to be generated, which directly affects the uniformity and accuracy of imaging. SUMMARY

[0005] To solve the above technical problems, the present application provides a tungsten paste for an ultrasonic fingerprint module and a preparation method thereof. The present application adds saturated polyester, curing agent, saturated polyester modification aid, conductive tungsten powder with a particle size of less than 5 μm, and simultaneously compounding organic solvents and various aids in the conductive tungsten paste, so that the obtained tungsten paste has a curing temperature of ≤100 ℃, high density, low thixotropy (≤2), low surface roughness (R zThe advantages of the application are that the thickness of the coating layer is uniform, the coating layer has no delamination (<2.5 μm) and no large-size holes (>1 μm) after lamination.

[0006] To achieve the above object, the application provides the following technical solutions.

[0007] The application provides a tungsten slurry for an ultrasonic fingerprint module, which contains the following components in percentage by mass: saturated polyester 2-10%, curing agent 0.5-2%, saturated polyester modification aid 0.01-0.5%, tungsten powder 80-90%, organic solvent 2-12%, dispersant 0.2-2%, coupling agent 0.5-1.2% and thixotropic agent 0.03-1.35%.

[0008] Further, the saturated polyester is selected from one or more of linear aromatic saturated polyester, linear aliphatic saturated polyester and linear aromatic-aliphatic saturated polyester.

[0009] Further, the saturated polyester modification aid is selected from one or more of diisocyanate, oxazoline, acid anhydride, organic tin and acetylacetone metal salt.

[0010] Further, the tungsten powder is selected from one or more of micron-level spherical tungsten powder, submicron-level spherical tungsten powder and nanometer-level polyhedral tungsten powder.

[0011] Further, the micron-level spherical tungsten powder has a D50 particle size of 0.7-1.5 μm and a D100 particle size of 2.5-3.8 μm; the submicron-level spherical tungsten powder has a D50 particle size of 0.4-0.7 μm and a D100 particle size of 0.9-1.5 μm; and the nanometer-level polyhedral tungsten powder has a maximum particle size of <0.6 μm.

[0012] Further, the curing agent is selected from one or more of oxazoline, isocyanate, diisocyanate and dicyanate prepolymer.

[0013] Further, the organic solvent is selected from one or more of mixed dibasic acid ester, dimethyl adipate, 3-methoxybutyl acetate, diethyl adipate and propylene glycol methyl ether acetate.

[0014] Further, the dispersant is selected from one or more of phosphate ester-based dispersant, quaternary ammonium salt, polyvinylpyrrolidone, sodium oleate and TDO dispersant.

[0015] Further, the coupling agent is selected from one or more of silane coupling agent, titanate coupling agent, aluminate coupling agent, bimetallic coupling agent, phosphate ester coupling agent and borate ester coupling agent.

[0016] Further, the thixotropic agent is selected from one or more of fumed silica, organic bentonite and polyamide wax.

[0017] The application provides a preparation method of the tungsten slurry for the ultrasonic fingerprint module.

[0018] (1) mixing and dissolving saturated polyester and an organic solvent to obtain a first mixture;

[0019] (2) adding a saturated polyester modification aid, a coupling agent, a dispersant and a thixotropic agent to the first mixture, and performing first stirring and first grinding to obtain a second mixture;

[0020] (3) adding tungsten powder and a curing agent to the second mixture, and performing second stirring, second grinding, filtering and vacuum dispersion to obtain the tungsten slurry for the ultrasonic fingerprint module.

[0021] The application further provides an application of the tungsten slurry for the ultrasonic fingerprint module in preparing the ultrasonic fingerprint module.

[0022] Compared with the prior art, the application has the following advantages and technical effects:

[0023] The saturated polyester in the application is a straight-chain saturated polyester with a large molecular weight, which is beneficial to balance the strength and heat resistance of the slurry; meanwhile, the main chain carbon atoms of the straight-chain saturated polyester are saturated, the chemical bond stability is high, and the straight-chain saturated polyester has good chemical solvent resistance; the interaction between the straight-chain molecules is weak, the molecular chain is easy to slide, and the straight-chain saturated polyester can endow the material with good flexibility and leveling property.

[0024] The addition of the saturated polyester modifier enables the saturated polyester to have a large molecular weight after chain extension, realizes the ultrahigh bearing capacity of the tungsten powder, avoids the slurry stratification problem caused by the huge density of the tungsten powder, realizes the extremely strong leveling property, and makes the tungsten slurry realize the great breakthrough of the thixotropic index <1.5, which creates the prerequisite for the surface roughness R z <1.5 after printing and film forming.

[0025] The addition of the dispersant enables the tungsten powder to have extremely high interfacial stability activity, can be uniformly dispersed in the resin solution, effectively solves the tungsten powder particle sedimentation effect, effectively repels the adsorption of moisture on the interface of the substrate, improves the delamination problem that easily occurs after the coating product is stacked for multiple times, reduces the interfacial energy between the piezoelectric coating and the tungsten slurry and between the tungsten slurries, makes the tungsten slurry layers form good wetting effect, effectively reduces the problem that the surface roughness becomes large due to the stacking, and provides a good channel for ultrasonic transmission.

[0026] The addition of the coupling agent improves the adhesion between the slurry and the piezoelectric coating, greatly reduces the interfacial effect, greatly reduces the ultrasonic signal attenuation, and makes the ultrasonic image effect more clear.

[0027] Thixotropic agents form steric hindrance by adsorbing onto the surface of solid particles, which can prevent the agglomeration of nano-tungsten powder particles and the sedimentation of micron-sized tungsten powder particles, thereby maintaining the stability of the suspension system.

[0028] The addition of curing agent significantly improves the curing degree of the slurry, greatly reduces the porosity of the slurry, and significantly increases the density of the tungsten slurry, thereby greatly improving the transmission efficiency of ultrasonic signals.

[0029] This invention uses tungsten powder to prepare a slurry for ultrasonic fingerprint modules, which has the following advantages:

[0030] (1) Optimization of high-frequency signal transmission

[0031] High acoustic impedance: density of tungsten (19.3 g / cm³) 3 The concentration of 10.5 g / cm³ is much higher than that of silver (10.5 g / cm³). 3 Therefore, composite materials made from tungsten paste have very high acoustic impedance (up to 35 M ayls or more), which can significantly reduce interface reflection and improve ultrasonic penetration.

[0032] Anti-skin effect: Tungsten has a higher atomic number (74) than silver (47), resulting in a lower electron scattering probability. In the high-frequency range (1MHz-10MHz), signal attenuation is reduced by 15%~20% compared to silver paste.

[0033] High acoustic transmission speed: density of tungsten (19.3 g / cm³) 3 Tungsten's density is 1.8 times that of silver, and its elastic modulus (approximately 411 GPa) is significantly higher than that of silver (approximately 83 GPa). The synergistic effect of high density and high elastic modulus results in a significantly higher sound velocity in tungsten compared to silver. The sound velocity in tungsten (5334 m / s) is significantly higher than that in silver (3607 m / s), which reduces the propagation time of ultrasound waves in the transmission medium, lowers signal delay, and improves the real-time performance of fingerprint recognition. For example, at a frequency of 10 MHz, the wavelength of tungsten (λ=v / f=5334 / 107=0.5334 mm) is longer than that of silver (0.3607 mm), which helps reduce the scattering and attenuation of high-frequency signals.

[0034] (2) Excellent thermal management performance

[0035] High thermal conductivity: Tungsten has a thermal conductivity of 173 W / m·K, which is lower than that of silver (429 W / m·K). However, by optimizing the particle size and sintering density of tungsten powder, a thermal resistance of <0.12℃·cm / W can be achieved, which meets the heat dissipation requirements of the module.

[0036] Thermal expansion coefficient matching: the high temperature resistance (melting point 3422℃) and high sound speed of tungsten make it more stable in vehicle fingerprint recognition or industrial access control system, while silver may cause performance degradation due to mismatch of thermal expansion coefficient. In addition, the thermal expansion coefficient (CTE, 4.5ppm / ℃) of tungsten is close to that of piezoelectric materials (such as PZT, 5ppm / ℃), which can effectively avoid interface failure caused by thermal stress.

[0037] (3) Process compatibility and cost advantage

[0038] Surface roughness: because the density of tungsten is much higher than that of silver, the specific surface area of tungsten powder with the same particle size will be significantly lower than that of silver powder. In the process of preparing slurry, low specific surface area provides a natural advantage for realizing low surface roughness after slurry printing and drying;

[0039] Low cost: the price of tungsten (about 300 yuan / kg) is only about 1 / 20 of that of silver, and the cost of tungsten slurry material can be reduced by 60%~70%, significantly improving the performance price ratio of the module. DETAILED DESCRIPTION

[0040] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0041] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application will be further described in detail below with specific embodiments.

[0042] The tungsten slurry for the ultrasonic fingerprint module provided by the embodiments of the present application comprises the following components in terms of mass percentage: saturated polyester 2%~10%, curing agent 0.5%~2%, saturated polyester modification aid 0.01%~0.5%, tungsten powder 80%~90%, organic solvent 2%~12%, dispersant 0.2%~2%, coupling agent 0.5%~1.2% and thixotropic agent 0.03%~1.35%; further preferably: saturated polyester 6%, curing agent 1%, saturated polyester modification aid 0.2%, tungsten powder 82%, organic solvent 8.8%, dispersant 0.2%, coupling agent 1% and thixotropic agent 0.8%.

[0043] In preferred embodiments, the saturated polyester is a linear saturated polyester; the linear saturated polyester is selected from one or more of linear aromatic saturated polyester, linear aliphatic saturated polyester and linear aromatic-aliphatic saturated polyester, further preferably linear aliphatic saturated polyester, and more preferably TOYOX 270 saturated polyester or TOYOX 7000A saturated polyester; the saturated polyester has a relative molecular weight of 10000-40000.

[0044] In preferred embodiments, the saturated polyester modifier is selected from one or more of diisocyanate, oxazoline, anhydride, organic tin and acetylacetone metal salt, further preferably dibutyltin dilaurate and / or acetylacetone metal salt; the acetylacetone metal salt is selected from one or more of acetylacetone zirconium, acetylacetone copper and acetylacetone cobalt, further preferably acetylacetone zirconium.

[0045] In preferred embodiments, the tungsten powder is selected from one or more of micron-sized spherical tungsten powder, sub-micron-sized spherical tungsten powder and nano-sized polyhedral tungsten powder; the tungsten powder is sourced from Xiamen Tungsten Industry (Jinlu); when the tungsten powder is micron-sized spherical tungsten powder, sub-micron-sized spherical tungsten powder and nano-sized polyhedral tungsten powder, the mass ratio of the micron-sized spherical tungsten powder, the sub-micron-sized spherical tungsten powder and the nano-sized polyhedral tungsten powder is (6.5-7):(2-2.7):(0.8-1); when the tungsten powder is micron-sized spherical tungsten powder and sub-micron-sized spherical tungsten powder, the mass ratio of the micron-sized spherical tungsten powder and the sub-micron-sized spherical tungsten powder is 7:3.

[0046] In preferred embodiments, the micron-sized spherical tungsten powder has a D50 particle size of 0.7-1.5 μm and a D100 particle size of 2.5-3.8 μm; the sub-micron-sized spherical tungsten powder has a D50 particle size of 0.4-0.7 μm and a D100 particle size of 0.9-1.5 μm; the nano-sized polyhedral tungsten powder has a maximum particle size of <0.6 μm.

[0047] In preferred embodiments, the curing agent is selected from one or more of oxazoline, isocyanate, diisocyanate and dicyanate prepolymer, further preferably isocyanate, and more preferably K60X isocyanate from Asahi Kasei.

[0048] In preferred embodiments, the organic solvent is selected from one or more of mixed dibasic ester (DBE), dimethyl adipate, 3-methoxybutyl acetate, diethyl adipate and propylene glycol methyl ether acetate, further preferably mixed dibasic ester (DBE) and diethyl adipate; the volume ratio of the mixed dibasic ester (DBE) and diethyl adipate is 2:3.

[0049] In preferred embodiments, the dispersing agent is selected from one or more of phosphate ester dispersing agent, quaternary ammonium salt, polyvinylpyrrolidone, sodium oleate and TDO dispersing agent, further preferably phosphate ester dispersing agent and / or TDO dispersing agent, more preferably phosphate ester dispersing agent; the phosphate ester dispersing agent is preferably BYK-110 of BYK; the TDO dispersing agent is preferably TDO dispersing agent of WACKER.

[0050] In preferred embodiments, the coupling agent is selected from one or more of silane coupling agent, titanate coupling agent, aluminate coupling agent, bimetal coupling agent, phosphate ester coupling agent and borate coupling agent, further preferably silane coupling agent, more preferably 6040 silane coupling agent of DOVER.

[0051] In preferred embodiments, the thixotropic agent is selected from one or more of fumed silica, organic bentonite and polyamide wax, further preferably fumed silica, more preferably H20 fumed silica of WACKER.

[0052] The present application provides a preparation method of the tungsten paste for the ultrasonic fingerprint module, comprising the following steps:

[0053] (1) mixing and dissolving saturated polyester and organic solvent to obtain a first mixture;

[0054] (2) adding saturated polyester modification aid, coupling agent, dispersing agent and thixotropic agent to the first mixture, and performing first stirring and first grinding to obtain a second mixture;

[0055] (3) adding tungsten powder and curing agent to the second mixture, and performing second stirring, second grinding, filtering and vacuum dispersion to obtain the tungsten paste for the ultrasonic fingerprint module.

[0056] In preferred embodiments, in step (1), the temperature of the mixing and dissolving is 90±5℃, and the time is 15h; the mixing and dissolving is accompanied by stirring, and the stirring speed is 200-500rpm; the equipment for the mixing and dissolving is a glass stirred tank.

[0057] In preferred embodiments, in steps (2) and (3), the first stirring and the second stirring are both performed on a double planetary stirrer at a speed of 50-100rpm / 1000-2000rpm.

[0058] In preferred embodiments, in steps (2) and (3), the first grinding and the second grinding are both performed by three-roll grinding.

[0059] In the preferred embodiment, in step (3), the mesh size of the filter screen used in the filtration is 800-2000 mesh; and the device used in the filtration is a filter press. High mesh size filtration helps to obtain uniform and small-size tungsten slurry particles, improves the fineness of the tungsten slurry, and can obtain tungsten slurry with a fineness of less than 1.0 μm (tested by using a doctor blade fineness gauge), and the particle size of the tungsten slurry after solidification is less than 5 μm.

[0060] In the preferred embodiment, in step (3), the vacuum degree of the vacuum dispersion is 1-5 kPa, the rotation speed is 200-1000 rpm, and the time is 10-30 min. Vacuum dispersion helps to remove air bubbles introduced in the production process of the tungsten slurry, and can reduce the porosity of the tungsten slurry with a pore diameter > 1 μm after solidification.

[0061] The application also provides an application of the tungsten slurry for the ultrasonic fingerprint module in the preparation of the ultrasonic fingerprint module.

[0062] Unless otherwise specified, the raw materials in the embodiments of the application are obtained by commercial purchase.

[0063] In the following examples, Oriental Yarn refers to Japan Oriental Yarn Co., Ltd., Aladdin refers to Shanghai Aladdin Biochemical Technology Co., Ltd., Asahi Kasei refers to Asahi Kasei Corporation, Wacker refers to Wacker Chemie AG, Wincreate refers to Wincreate Industrial Group, Dow Corning refers to Dow Corning Corporation, and Xiamen Tungsten (Jinlu) refers to Xiamen Jinlu Special Alloy Co., Ltd.

[0064] The D50 particle size of the micron-level spherical tungsten powder used is 0.7-1.5 μm, and the D100 particle size is 2.5-3.8 μm; the D50 particle size of the sub-micron-level spherical tungsten powder used is 0.4-0.7 μm, and the D100 particle size is 0.9-1.5 μm; and the maximum particle size of the nano-level polyhedral tungsten powder used is < 0.6 μm.

[0065] Example 1

[0066] A tungsten slurry for an ultrasonic fingerprint module, which consists of the following components in terms of mass percentage: saturated polyester 6%, saturated polyester modification aid 0.2%, curing agent 1%, dispersing agent 0.2%, organic solvent 8.8%, coupling agent 1%, tungsten powder 82%, and thixotropic agent 0.8%;

[0067] The saturated polyester is 100% Toyobo 270 saturated polyester, the saturated polyester modifier is acetylacetone zirconium of Aladdin, the curing agent is K60X isocyanate of Asahi Kasei, the thixotropic agent is H20 fumed silica of Wacker, the dispersing agent is TDO of Wincrete, the coupling agent is 6040 silane coupling agent of Dow Corning, the organic solvent is a mixture of DBE and diethyl adipate (volume ratio 2:3), and the tungsten powder is micron-level spherical tungsten powder: sub-micron-level spherical tungsten powder: nano-level polyhedral tungsten powder = 7:2:1 of Xiamen Tungsten Industry (Jinlu).

[0068] The preparation method of the tungsten slurry for the ultrasonic fingerprint module includes the following steps:

[0069] (1) The saturated polyester and the organic solvent are heated and mixed in a glass stirred kettle at 90±5°C and 450 rpm for 15 hours until the resin solution is uniform and fine without large particles, to obtain a first mixture;

[0070] (2) The saturated polyester modifier, the coupling agent, the dispersing agent and the thixotropic agent are added to the first mixture, and then mixed uniformly on a double planetary mixer at 70 / 1200 rpm, and the mixed slurry is ground on a three-roll mill until the fineness of the slurry is less than 5 μm, to obtain a second mixture;

[0071] (3) The tungsten powder and the curing agent are added to the second mixture, and then mixed uniformly on a double planetary mixer at 90 / 1500 rpm, and then ground on a three-roll mill, and then filtered on a filter press with a mesh size of 800-2000, and then dispersed in vacuum at 2 kPa and 500 rpm for 30 minutes, to obtain the tungsten slurry for the ultrasonic fingerprint module.

[0072] The viscosity of the tungsten slurry for the ultrasonic fingerprint module obtained in Example 1 is tested, and the viscosity of the tungsten slurry at 1 rpm, 5 rpm and 10 rpm is 32000 cP, 24000 cP and 18000 cP respectively, and the thixotropy of the tungsten slurry is calculated to be 1.78 (32000 cP / 18000 cP) according to the viscosity; the fineness of the tungsten slurry is measured to be 0.92 μm using a doctor blade fineness gauge.

[0073] The tungsten slurry for the ultrasonic fingerprint module obtained in Example 1 is screen printed and dried at 90°C for 60 minutes, and the pencil hardness is measured to be ≥4H, the particle size is 4.28 μm, and the adhesion level on the flat glass is 5B; after printing 5 more layers, a coating with a total thickness of 20-35 μm is obtained, and the surface roughness R zThe pore size of the tungsten slurry coating is greater than 1 μm, and the porosity of the tungsten slurry coating is 1.89% after CP argon ion polishing. The tungsten slurry coating is not delaminated, and there is no pore greater than 3 μm. The acoustic velocity of the tungsten slurry coating is 3780 m / s at room temperature according to the longitudinal wave velocity measurement method in GB / T 23900-2009 "Nondestructive testing-Materials-Ultrasonic velocity measurement methods". The CTE of the tungsten slurry coating is 6.8 ppm / ℃ according to GB / T 34183-2017 "Thermal insulation products for building equipment and industrial installations-Determination of coefficient of thermal expansion".

[0074] Example 2

[0075] A tungsten slurry for an ultrasonic fingerprint module, consisting of the following components by mass percentage: saturated polyester 6%, saturated polyester modifier 0.2%, curing agent 1%, dispersing agent 0.2%, organic solvent 8.8%, coupling agent 1%, tungsten powder 82%, and thixotropic agent 0.8%;

[0076] The saturated polyester is 100% Toyobo 270 saturated polyester, the saturated polyester modifier is acetylacetone zirconium of Aladdin, the curing agent is K60X isocyanate of Asahi Kasei, the thixotropic agent is H20 fumed silica of Wacker, the dispersing agent is TDO of Wincrete, the coupling agent is 6040 silane coupling agent of Dow Corning, the organic solvent is a mixture of DBE and diethyl adipate (volume ratio 2:3), and the tungsten powder is micron-level spherical tungsten powder: sub-micron-level spherical tungsten powder: nano-level polyhedral tungsten powder = 6.5:2.7:0.8 of Xiamen Tungsten Industry (Jinlu).

[0077] The preparation method of the above-mentioned tungsten slurry for an ultrasonic fingerprint module is the same as that of Example 1.

[0078] The viscosity of the tungsten slurry for an ultrasonic fingerprint module obtained in Example 2 is tested, and the viscosity of the tungsten slurry at 1 rpm, 5 rpm, and 10 rpm is 41200 cP, 24200 cP, and 19700 cP, respectively. The thixotropy of the tungsten slurry is calculated to be 2.09 (41200 cP / 19700 cP) according to the viscosity. The fineness of the tungsten slurry is measured to be 0.82 μm using a doctor blade fineness gauge.

[0079] The tungsten slurry for an ultrasonic fingerprint module obtained in Example 2 is screen printed, and dried at 90℃ for 60 min. The pencil hardness of the tungsten slurry is greater than or equal to 4H, the particle size is 4.65 μm, and the adhesion level on the flat glass is 5B. After 5 layers of printing, a coating with a total thickness of 28-35 μm is obtained, and the surface roughness R zThe pore size of the tungsten slurry coating is 1.6 μm, and the porosity of the pores with a size greater than 1 μm is 1.5% after CP argon ion polishing. The tungsten slurry coating is not delaminated and does not have pores with a size greater than 3 μm. The acoustic velocity of the tungsten slurry coating at room temperature is 4130 m / s according to the longitudinal wave velocity measurement method in GB / T 23900-2009 "Nondestructive testing-Materials-Ultrasonic velocity measurement methods". The CTE of the tungsten slurry coating is 6.0 ppm / ℃ according to GB / T 34183-2017 "Thermal insulation products for building equipment and industrial installations-Determination of coefficient of thermal expansion".

[0080] Example 3

[0081] A tungsten slurry for an ultrasonic fingerprint module, consisting of the following components by mass percentage: saturated polyester 6%, saturated polyester modification aid 0.2%, curing agent 1%, dispersing agent 0.2%, organic solvent 8.8%, coupling agent 1%, tungsten powder 82%, and thixotropic agent 0.8%;

[0082] The saturated polyester is 100% Toyo Rayon 7000A saturated polyester, the saturated polyester modification aid is Araldite acetylacetone zirconium, the curing agent is Asahi Kasei K60X isocyanate, the thixotropic agent is Wacker H20 fumed silica, the dispersing agent is Wincrete TDO, the coupling agent is Dow Corning 6040 silane coupling agent, the organic solvent is a mixture of DBE and diethyl adipate (volume ratio 2:3), and the tungsten powder is micron-level spherical tungsten powder: sub-micron-level spherical tungsten powder: nanometer-level polyhedral tungsten powder = 6.5:2.7:0.8 from Xiamen Tungsten (Jinlu).

[0083] The preparation method of the above-mentioned tungsten slurry for an ultrasonic fingerprint module is the same as that of Example 1.

[0084] The tungsten slurry for an ultrasonic fingerprint module obtained in Example 3 is subjected to viscosity testing, and the viscosities of the tungsten slurry at rotational speeds of 1 rpm, 5 rpm, and 10 rpm are 31200 cP, 23200 cP, and 18700 cP, respectively. The thixotropy of the tungsten slurry is calculated to be 1.67 (31200 cP / 18700 cP) according to the viscosity. The fineness of the tungsten slurry is measured to be 0.58 μm using a doctor blade fineness gauge.

[0085] The tungsten slurry for an ultrasonic fingerprint module obtained in Example 3 is subjected to screen printing, and is dried at 90℃ for 60 min. The pencil hardness of the tungsten slurry is ≥4H, the particle size is 4.05 μm, and the adhesion level on flat plate glass is 5B grade. After 5 layers of printing are continuously stacked, a coating with a total thickness of 28-30 μm is obtained, and the surface roughness R zThe pore size of the tungsten slurry coating is greater than 1 μm, and the porosity of the tungsten slurry coating is 1.1% after CP argon ion polishing, and the tungsten slurry coating is not delaminated and there is no pore greater than 3 μm. According to the longitudinal wave velocity measurement method in GB / T 23900-2009 "Nondestructive testing-Materials-Ultrasonic velocity measurement methods", the acoustic velocity of the tungsten slurry coating at room temperature is 4260 m / s, and according to GB / T 34183-2017 "Thermal insulation products for building equipment and industrial devices-Determination of thermal expansion coefficient", the CTE of the tungsten slurry coating is 5.8 ppm / ℃ (the low temperature during testing is -40℃, and the high temperature is 100℃).

[0086] Example 4

[0087] A tungsten slurry for an ultrasonic fingerprint module, consisting of the following components by mass percentage: saturated polyester 6%, saturated polyester modifier 0.2%, curing agent 1%, dispersing agent 0.2%, organic solvent 8.8%, coupling agent 1%, tungsten powder 82%, and thixotropic agent 0.8%;

[0088] The saturated polyester is 100% Toyobo 7000A saturated polyester, the saturated polyester modifier is dibutyltin dilaurate, the curing agent is K60X isocyanate from Asahi Kasei, the thixotropic agent is H20 fumed silica from Wacker, the dispersing agent is TDO from Wincrete, the coupling agent is 6040 silane coupling agent from Dow Corning, the organic solvent is a mixture of DBE and diethyl adipate (volume ratio 2:3), and the tungsten powder is micron-level spherical tungsten powder: sub-micron-level spherical tungsten powder: nano-level polyhedral tungsten powder = 6.5:2.7:0.8 from Xiamen Tungsten Industry (Jinlu);

[0089] The preparation method of the above-mentioned tungsten slurry for an ultrasonic fingerprint module is the same as that of Example 1.

[0090] The tungsten slurry for an ultrasonic fingerprint module obtained in Example 4 is subjected to viscosity testing, and the viscosity of the tungsten slurry at 1 rpm, 5 rpm, and 10 rpm is 35100 cP, 23800 cP, and 19700 cP, respectively. According to the viscosity calculation, the thixotropy of the tungsten slurry is 1.78 (35100 cP / 19700 cP); the fineness of the tungsten slurry is 0.71 μm measured using a doctor blade fineness gauge.

[0091] The tungsten slurry for an ultrasonic fingerprint module obtained in Example 4 is subjected to screen printing, and is dried at 90℃ for 60 min. The pencil hardness of the tungsten slurry is ≥4H, the particle size is 3.89 μm, and the adhesion level on flat glass is 5B grade. After 5 layers of printing, a coating with a total thickness of 26-32 μm is obtained, and the surface roughness R zThe porosity of the holes with a diameter >1 μm was 1.09% after CP argon ion polishing with a thickness of 2 μm, the tungsten slurry coating was slightly delaminated, and there were a small amount of holes with a diameter >3 μm; the acoustic velocity of the tungsten slurry coating at room temperature was 4250 m / s according to the longitudinal wave velocity measurement method in GB / T 23900-2009 "Nondestructive testing - Material ultrasonic velocity measurement method", and the CTE of the tungsten slurry coating was 5.8 ppm / ℃ according to GB / T 34183-2017 "Thermal insulation products for building equipment and industrial devices - Determination of thermal expansion coefficient".

[0092] Example 5

[0093] A tungsten slurry for an ultrasonic fingerprint module, consisting of the following components by mass percentage: saturated polyester 6%, saturated polyester modifier 0.2%, curing agent 1%, dispersing agent 0.2%, organic solvent 8.8%, coupling agent 1%, tungsten powder 82%, and thixotropic agent 0.8%;

[0094] The saturated polyester is 100% Toyo Rosh 270 saturated polyester, the saturated polyester modifier is acetylacetone zirconium of Aladdin, the curing agent is K60X isocyanate of Asahi Kasei, the thixotropic agent is H20 fumed silica of Wacker, the dispersing agent is TDO of Wincrete, the coupling agent is 6040 silane coupling agent of Dow Corning, the organic solvent is a mixture of DBE and diethyl adipate (volume ratio 2:3), and the tungsten powder is micron-level spherical tungsten powder: sub-micron-level spherical tungsten powder = 7:3 of Xiamen Tungsten Industry (Jinlu).

[0095] The preparation method of the above-mentioned tungsten slurry for an ultrasonic fingerprint module is the same as that of Example 1.

[0096] The tungsten slurry for an ultrasonic fingerprint module obtained in Example 5 was subjected to viscosity testing, and the viscosities of the tungsten slurry at rotational speeds of 1 rpm, 5 rpm, and 10 rpm were 46700 cP, 24500 cP, and 19600 cP, respectively. According to the viscosity calculation, the thixotropy of the tungsten slurry was 2.38 (46700 cP / 19600 cP). The fineness of the tungsten slurry was 0.92 μm as measured using a doctor blade fineness gauge.

[0097] The tungsten slurry for an ultrasonic fingerprint module obtained in Example 5 was subjected to screen printing, and was dried at 90℃ for 60 min. The pencil hardness of the tungsten slurry was ≥4H, the particle size was 4.71 μm, and the adhesion level on flat plate glass was 5B grade. After 5 layers of printing, a coating with a total thickness of 20-35 μm was obtained, and the surface roughness R zThe pore size of the tungsten slurry coating is 2.5 μm, the porosity of the pores with a size greater than 1 μm is 1.11% after CP argon ion polishing, the tungsten slurry coating is slightly delaminated, and there are no pores with a size greater than 3 μm; the acoustic velocity of the tungsten slurry coating at room temperature is 4280 m / s according to the longitudinal wave velocity measurement method in GB / T 23900-2009 "Nondestructive testing - Material ultrasonic velocity measurement method"; and the CTE of the tungsten slurry coating is 5.8 ppm / ℃ according to GB / T 34183-2017 "Thermal insulation products for building equipment and industrial devices - Determination of thermal expansion coefficient".

[0098] Example 6

[0099] A tungsten slurry for an ultrasonic fingerprint module, consisting of the following components by mass percentage: saturated polyester 6%, saturated polyester modifier 0.2%, curing agent 1%, dispersing agent 0.2%, organic solvent 8.8%, coupling agent 1%, tungsten powder 82%, and thixotropic agent 0.8%;

[0100] The saturated polyester is 100% Toyobo 270 saturated polyester, the saturated polyester modifier is acetylacetone zirconium from Aladdin, the curing agent is K60X isocyanate from Asahi Kasei, the thixotropic agent is H20 fumed silica from Wacker, the dispersing agent is BYK-110 from BYK, the coupling agent is 6040 silane coupling agent from Dow Corning, the organic solvent is a mixture of DBE and diethyl adipate (volume ratio 2:3), and the tungsten powder is micron-level spherical tungsten powder: sub-micron-level spherical tungsten powder: nano-level polyhedral tungsten powder = 6.5:2.7:0.8 from Xiamen Tungsten Industry (Jinlu);

[0101] The preparation method of the above-mentioned tungsten slurry for an ultrasonic fingerprint module is the same as that of Example 1.

[0102] The tungsten slurry for an ultrasonic fingerprint module obtained in Example 6 is subjected to viscosity testing, and the viscosities of the tungsten slurry at rotational speeds of 1 rpm, 5 rpm, and 10 rpm are 26800 cP, 23200 cP, and 18300 cP, respectively. According to the viscosity calculation, the thixotropy of the tungsten slurry is 1.46 (26800 cP / 18300 cP). The fineness of the tungsten slurry is 0.48 μm as measured using a doctor blade fineness gauge.

[0103] The tungsten slurry for an ultrasonic fingerprint module obtained in Example 6 is subjected to screen printing, and is dried at 90℃ for 60 min. The pencil hardness of the tungsten slurry is ≥4H, the particle size is 4.05 μm, and the adhesion level on flat plate glass is 5B grade. After 5 layers of printing, a coating with a total thickness of 29-31 μm is obtained, and the surface roughness R zThe pore size of the tungsten slurry prepared in Example 1 is 1.2 μm, and the porosity of the pores with a size greater than 1 μm is 0.51% after CP argon ion polishing. The tungsten slurry coating is not delaminated and there is no pore with a size greater than 3 μm. The acoustic velocity of the tungsten slurry coating at room temperature is 4940 m / s according to the longitudinal wave velocity measurement method in GB / T 23900-2009 "Nondestructive testing-Materials-Ultrasonic velocity measurement methods", and the CTE of the tungsten slurry coating is 5.2 ppm / °C according to GB / T 34183-2017 "Determination of thermal expansion coefficient of thermal insulation products for building equipment and industrial devices".

[0104] It can be seen from the tungsten slurry for the ultrasonic fingerprint module prepared in Examples 1-6 that the delamination of the tungsten slurry can be avoided by selecting a suitable acetylacetone salt and tungsten powder ratio. The best ratio of tungsten powder is micron-level spherical tungsten powder: sub-micron-level spherical tungsten powder: nano-level polyhedral tungsten powder = 6.5:2.7:0.8. The factors affecting the surface roughness of the coating and the uniformity of the printing thickness (i.e., thixotropy) are complex. Through analysis and comparison of experimental data, it is found that the best dispersant is BYK-110 of BYK, the tungsten powder ratio is 6.5:2.7:0.8, and the best saturated polyester is pure Toyo Rosh 270 saturated polyester.

[0105] Example 7

[0106] A tungsten slurry for an ultrasonic fingerprint module, consisting of the following components by mass percentage: saturated polyester 6.8%, saturated polyester modification aid 0.2%, curing agent 1%, dispersant 0.2%, organic solvent 8%, coupling agent 1%, tungsten powder 82%, and thixotropic agent 0.8%;

[0107] The saturated polyester is 100% Toyo Rosh 270 saturated polyester, the saturated polyester modification aid is acetylacetone zirconium of Aladdin, the curing agent is K60X isocyanate of Asahi Kasei, the thixotropic agent is H20 fumed silica of Wacker, the dispersant is BYK-110 of BYK, the coupling agent is 6040 silane coupling agent of Dow Corning, the organic solvent is a mixture of DBE and diethyl adipate (volume ratio 2:3), and the tungsten powder is micron-level spherical tungsten powder: sub-micron-level spherical tungsten powder: nano-level polyhedral tungsten powder = 6.5:2.7:0.8 of Xiamen Tungsten Industry (Jinlu).

[0108] The preparation method of the above-mentioned tungsten slurry for an ultrasonic fingerprint module is the same as that of Example 1.

[0109] The tungsten paste obtained in Example 7 for the ultrasonic fingerprint module was subjected to viscosity test, and the viscosity of the tungsten paste was measured to be 24800 cP, 22700 cP and 17300 cP at 1 rpm, 5 rpm and 10 rpm, respectively. According to the viscosity, the thixotropy of the tungsten paste was calculated to be 1.43 (24800 cP / 17300 cP); the fineness of the tungsten paste was measured to be 0.47 μm using a doctor blade fineness gauge.

[0110] The tungsten paste obtained in Example 7 for the ultrasonic fingerprint module was subjected to screen printing, and was dried at 90℃ for 60 min. The pencil hardness of the tungsten paste was measured to be ≥4H, the particle size was 3.95 μm, and the adhesion grade on the flat glass was 5B grade. After 5 layers of printing were continuously stacked, a coating layer with a total thickness of 27-31 μm was obtained, and the surface roughness R z was measured to be 1.6 μm. After CP argon ion polishing, the porosity of the pores with a pore size >1 μm was measured to be 0.62%, the tungsten paste coating was not delaminated, and there was no pore with a pore size >3 μm. According to the longitudinal wave velocity measurement method in GB / T 23900-2009 "Nondestructive testing - Material ultrasonic velocity measurement method", the sound velocity of the tungsten paste coating at room temperature was measured to be 4320 m / s. According to GB / T 34183-2017 "Thermal insulation products for building equipment and industrial devices - Determination of coefficient of thermal expansion", the CTE of the tungsten paste coating was measured to be 5.6 ppm / ℃ (the low temperature during testing was -40℃, and the high temperature was 100℃).

[0111] Example 8

[0112] A tungsten paste for an ultrasonic fingerprint module, consisting of the following components in terms of mass percentage: saturated polyester 6%, saturated polyester modifier 0.2%, curing agent 1%, dispersing agent 0.2%, organic solvent 5.8%, coupling agent 1%, tungsten powder 85%, and thixotropic agent 0.8%;

[0113] The saturated polyester is 100% Toyo Rosh 270 saturated polyester, the saturated polyester modifier is acetylacetone zirconium of Aladdin, the curing agent is K60X isocyanate of Asahi Kasei, the thixotropic agent is H20 fumed silica of Wacker, the dispersing agent is BYK-110 of BYK, the coupling agent is 6040 silane coupling agent of Dow Corning, the organic solvent is a mixture of DBE and diethyl adipate (volume ratio 2:3), and the tungsten powder is micron-level spherical tungsten powder: sub-micron-level spherical tungsten powder: nano-level polyhedral tungsten powder = 6.5:2.7:0.8 of Xiamen Tungsten Industry (Jinlu).

[0114] The preparation method of the above-mentioned tungsten paste for the ultrasonic fingerprint module is the same as that of Example 1.

[0115] The tungsten paste obtained in Example 8 for the ultrasonic fingerprint module was subjected to viscosity test, and the viscosity of the tungsten paste was measured to be 35800 cP, 24700 cP and 20500 cP at 1 rpm, 5 rpm and 10 rpm, respectively. According to the viscosity, the thixotropy of the tungsten paste was calculated to be 1.75 (35800 cP / 20500 cP); the fineness of the tungsten paste was measured to be 0.78 μm using a doctor blade fineness gauge.

[0116] The tungsten paste obtained in Example 8 for the ultrasonic fingerprint module was subjected to screen printing, and was dried at 90℃ for 60 min. The pencil hardness of the tungsten paste was measured to be ≥4H, the particle size was 3.96 μm, and the adhesion grade on the flat glass was 5B grade. After 5 layers of printing were continuously stacked, a coating layer with a total thickness of 31-36 μm was obtained, and the surface roughness R z was measured to be 1.5 μm. After CP argon ion polishing, the porosity of the pores with a pore size >1 μm was measured to be 0.58%, the tungsten paste coating was not delaminated, and there was no pore with a size >3 μm. According to the longitudinal wave velocity measurement method in GB / T 23900-2009 "Nondestructive testing-Materials-ultrasonic velocity measurement method", the sound velocity of the tungsten paste coating at room temperature was measured to be 4860 m / s. According to GB / T 34183-2017 "Thermal insulation products for building equipment and industrial installations-Determination of coefficient of thermal expansion", the CTE of the tungsten paste coating was measured to be 5.3 ppm / ℃ (the low temperature during the test was -40℃, and the high temperature was 100℃).

[0117] Example 9

[0118] A tungsten paste for an ultrasonic fingerprint module, consisting of the following components in terms of mass percentage: saturated polyester 6%, saturated polyester modifier 0.2%, curing agent 1%, dispersing agent 0.2%, organic solvent 5.8%, coupling agent 1%, tungsten powder 85%, and thixotropic agent 0.8%;

[0119] The saturated polyester is 100% Toyo Rosh 270 saturated polyester, the saturated polyester modifier is acetylacetone zirconium of Aladdin, the curing agent is K60X isocyanate of Asahi Kasei, the thixotropic agent is H20 fumed silica of Wacker, the dispersing agent is BYK-110 of BYK, the coupling agent is 6040 silane coupling agent of Dow Corning, the organic solvent is a mixture of DBE and diethyl adipate (volume ratio 1:1), and the tungsten powder is micron-level spherical tungsten powder: sub-micron-level spherical tungsten powder: nano-level polyhedral tungsten powder = 6.5:2.7:0.8 of Xiamen Tungsten Industry (Jinlu).

[0120] The preparation method of the above-mentioned tungsten paste for the ultrasonic fingerprint module is the same as that of Example 1.

[0121] The tungsten slurry obtained in Example 9 for the ultrasonic fingerprint module was subjected to viscosity test, and the viscosity of the tungsten slurry at 1 rpm, 5 rpm and 10 rpm was 32800 cP, 23700 cP and 19800 cP, respectively. According to the viscosity, the thixotropy of the tungsten slurry was calculated to be 1.65 (32800 cP / 19800 cP); the fineness of the tungsten slurry was measured to be 0.78 μm using a doctor blade fineness gauge.

[0122] The tungsten slurry obtained in Example 9 for the ultrasonic fingerprint module was subjected to screen printing, and dried at 90℃ for 60 min. The pencil hardness of the tungsten slurry was measured to be ≥4H, the particle size was 4.21 μm, and the adhesion grade on the flat glass was 5B grade. After 5 layers of printing, a coating with a total thickness of 31-36 μm was obtained, and the surface roughness R z was measured to be 1.5 μm. After CP argon ion polishing, the porosity of the pores with a pore size >1 μm was measured to be 1.57%, the tungsten slurry coating was not delaminated, and there was no pore with a size >3 μm. According to the longitudinal wave velocity measurement method in GB / T 23900-2009 “Nondestructive testing-Materials-ultrasonic velocity measurement method”, the sound velocity of the tungsten slurry coating at room temperature was measured to be 4020 m / s. According to GB / T 34183-2017 “Determination of thermal expansion coefficient of thermal insulation products for building equipment and industrial devices”, the CTE of the tungsten slurry coating was measured to be 6.2 ppm / ℃ (the low temperature during the test was -40℃, and the high temperature was 100℃).

[0123] The above merely describes the preferred embodiments of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can easily think of changes or replacements within the technical scope disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A tungsten paste for an ultrasonic fingerprint module, characterized by, by mass percentage, comprising the following components: saturated polyester 2%~10%, curing agent 0.5%~2%, saturated polyester modification aid 0.01%~0.5%, tungsten powder 80%~90%, organic solvent 2%~12%, dispersant 0.2%~2%, coupling agent 0.5%~1.2% and thixotropic agent 0.03%~1.35%; the saturated polyester modification aid is dibutyltin dilaurate and / or acetylacetone metal salt.

2. The tungsten paste for an ultrasonic fingerprint module according to claim 1, wherein the saturated polyester is selected from one or more of linear aromatic saturated polyester, linear aliphatic saturated polyester and linear aromatic-aliphatic saturated polyester.

3. The tungsten paste for an ultrasonic fingerprint module according to claim 1, wherein the tungsten powder is selected from one or more of micron-sized spherical tungsten powder, sub-micron-sized spherical tungsten powder and nano-sized polyhedral tungsten powder.

4. The tungsten paste for an ultrasonic fingerprint module according to claim 3, wherein the micron-sized spherical tungsten powder has a D50 particle size of 0.7~1.5μm and a D100 particle size of 2.5~3.8μm; the sub-micron-sized spherical tungsten powder has a D50 particle size of 0.4~0.7μm and a D100 particle size of 0.9~1.5μm; the nano-sized polyhedral tungsten powder has a maximum particle size of <0.6μm.

5. The tungsten paste for an ultrasonic fingerprint module according to claim 1, wherein the curing agent is selected from one or more of oxazoline, diisocyanate and dicyanate pre-polymer.

6. The tungsten paste for an ultrasonic fingerprint module according to claim 1, wherein the organic solvent is selected from one or more of mixed dibasic acid ester, dimethyl adipate, 3-methoxybutyl acetate, diethyl adipate and propylene glycol methyl ether acetate.

7. The tungsten paste for an ultrasonic fingerprint module according to claim 1, wherein the dispersant is selected from one or more of phosphate ester-based dispersant, quaternary ammonium salt, polyvinylpyrrolidone, sodium oleate and TDO dispersant; and / or, the coupling agent is selected from one or more of silane coupling agent, titanate coupling agent, aluminate coupling agent, bimetallic coupling agent, phosphate ester coupling agent and borate coupling agent; and / or, the thixotropic agent is selected from one or more of fumed silica, organic bentonite and polyamide wax.

8. A method of preparing the tungsten paste for the ultrasonic fingerprint module according to any one of claims 1 to 7, characterized in that, comprising the following steps: (1) mixing and dissolving saturated polyester and organic solvent to obtain a first mixture; (2) adding saturated polyester modification aid, coupling agent, dispersant and thixotropic agent to the first mixture, and performing first stirring and first grinding to obtain a second mixture; (3) adding tungsten powder and curing agent to the second mixture, and performing second stirring, second grinding, filtering and vacuum dispersion to obtain the tungsten paste for ultrasonic fingerprint module.

9. Use of the tungsten paste for ultrasonic fingerprint module according to any one of claims 1~7 in the preparation of ultrasonic fingerprint module.