Silver-bismuth-copper alloy electrode material for high-temperature crystal oscillator and crystal oscillator high-temperature-resistant coating method

Abstract

According to the silver-bismuth-copper alloy electrode material for the high-temperature crystal oscillator and the high-temperature-resistant coating method for the crystal oscillator, the problems that pure silver is prone to crystal grain growth and oxidation to form electrode material defects, and frequency drift is caused by electrode material defects of a traditional crystal oscillator in a high-temperature environment are solved; a multi-element alloy electrode material which takes silver as a basis and is added with bismuth, copper, indium, lanthanum and antimony and a matched preparation and coating process are provided, silver ensures excellent conductivity of an electrode, bismuth pinns a grain boundary, copper forms second-phase particles to jointly inhibit grain growth at high temperature, and the conductivity of the electrode is improved. Indium preferentially forms a compact oxide film, lanthanum purifies impurities and refines initial crystal grains, antimony optimizes wettability of a film layer to synergistically inhibit oxidation, and because crystal grain growth is inhibited, a fine and uniform microstructure of the electrode film layer can be maintained, uniform electron scattering and stable resistance are ensured, and electric field change of an excitation substrate caused by resistance fluctuation is avoided. The oxidation inhibition can prevent irregular change of electrode mass and volume and local difference of thermal expansion coefficient, and reduces frequency drift of the crystal oscillator.

Description

Technical Field

[0001] This application belongs to the field of crystal oscillators, and particularly relates to a silver-bismuth-copper alloy electrode material for high-temperature crystal oscillators and a high-temperature resistant coating method for crystal oscillators. Background Technology

[0002] Crystal oscillators are core components in information technology and wireless communication. They provide a reference frequency through the piezoelectric effect of quartz crystals and are known as the "heart" of electronic devices. With the expansion of application scenarios, oscillators need to operate stably for a long time in high-temperature environments. However, traditional electrode materials and coating processes have obvious defects: although pure silver electrodes have excellent conductivity, they are prone to grain growth, oxidation, and atomic migration at high temperatures, leading to changes in electrode quality, frequency drift, and even device failure; although gold electrodes have good stability, their cost is extremely high, making them uncompetitive in the market.

[0003] Meanwhile, existing coating processes suffer from problems such as poor film uniformity and insufficient adhesion: incomplete substrate cleaning can lead to film peeling, improper vacuum control can introduce impurities, and the lack of effective stress relief steps after coating makes the film prone to cracking at high temperatures. These problems collectively result in poor frequency stability and short lifespan of high-temperature crystal oscillators, failing to meet the application requirements of high-end fields. Summary of the Invention

[0004] This application provides a silver-bismuth-copper alloy electrode material for high-temperature crystal oscillators and a high-temperature resistant coating method for crystal oscillators. It can solve the problems of poor stability and high cost of traditional electrode materials at high temperatures, as well as the problems of insufficient film uniformity, weak adhesion and high-temperature performance degradation of existing coating processes.

[0005] In a first aspect, the present invention provides a silver-bismuth-copper alloy electrode material for a high-temperature crystal oscillator, the alloy material being composed of the following components by mass ratio: 96.80%≤Ag≤97.12%, 1.62%≤Bi≤2.14%, 0.96%≤Cu≤1.68%, 0.52%≤In≤0.90%, 0.20%≤La≤0.65%, and 0.12%≤Sb≤0.50%, the alloy material being used to prepare electrodes for a high-temperature crystal oscillator.

[0006] Optionally, the alloy material has the following composition by mass ratio: Ag 97.0%, Bi 1.9%, Cu 1.2%, In 0.7%, La 0.4%, and Sb 0.3%.

[0007] Optionally, the alloy material is prepared by vacuum induction melting, wherein the vacuum degree in the vacuum induction melting furnace during the melting process is ≤5×10⁻⁶. -3 Pa, after melting, uses furnace cooling to form alloy ingots from the molten alloy.

[0008] Optionally, the crystal substrate adapted to the alloy material is an AT-cut quartz crystal substrate, and the substrate has a size of 8×8×0.3mm.

[0009] Optionally, the alloy ingot is machined to form a raw material form suitable for a resistive evaporation source, wherein the raw material form is a filament with a diameter of 0.5-1.0 mm or a sheet with a thickness of 0.1-0.3 mm.

[0010] Secondly, the present invention provides a high-temperature resistant coating method for a crystal oscillator based on the silver-bismuth-copper alloy electrode material as described above, comprising the following steps: Silver-bismuth-copper alloy electrode material is processed into a raw material form suitable for resistive evaporation sources; The quartz crystal substrate is placed in an ultrasonic cleaner and cleaned with deionized water, then dehydrated with anhydrous ethanol, dried, and then placed in a special coating fixture. The fixture containing the substrate is placed into a continuously rotating vacuum crystal coating machine, and a vacuum is drawn to achieve a vacuum level of 2×10⁻⁶ in the coating chamber. -6 Below Pa, heat the substrate to 150-200℃, start the resistance evaporation source, control the film deposition rate to 0.5-1.5nm / s, and simultaneously drive the fixture to rotate until the total film thickness reaches 100-150nm; Annealing is performed by transferring the coated substrate to an annealing apparatus and heating it to 250-300℃ under vacuum or inert gas protection. After holding at that temperature for 30-60 minutes, the substrate is cooled to room temperature in the furnace.

[0011] Optionally, the deionized water washing time is 15 minutes, the anhydrous ethanol dehydration time is 10 minutes, and the drying method is to blow dry with nitrogen gas with a purity of ≥99.99%.

[0012] Optionally, the vacuum level of the coating chamber is controlled to be 1.5 × 10⁻⁶. -6 Pa, substrate heating temperature is 180℃, film deposition rate is stable at 1.0nm / s, fixture flipping angle range is 60°-120°, flipping speed is 5 times per minute, and deposition time is 120 seconds.

[0013] Optionally, the annealing process has a heating rate of 5°C / min, a holding time of 45 minutes, and a rate at which the substrate is cooled to room temperature in the furnace after annealing ≤10°C / min.

[0014] Optionally, the resistive evaporation source is a tungsten wire resistive evaporation source, wherein the diameter of the tungsten wire is 0.3-0.5 mm, and the tungsten wire is wound into a spiral shape with a spiral diameter of 3-5 mm.

[0015] As can be seen from the above technical solution, this application provides a silver-bismuth-copper alloy electrode material for high-temperature crystal oscillators and a high-temperature resistant coating method for crystal oscillators. The inventors of this application have discovered that pure silver is prone to grain growth and oxidation, resulting in electrode material defects. Traditional crystal oscillators suffer from frequency drift problems due to electrode material defects at high temperatures. In view of this, a multi-element alloy electrode material based on silver and supplemented with bismuth, copper, indium, lanthanum, and antimony, along with a matching preparation and coating process, is proposed. Silver ensures excellent electrode conductivity, bismuth pins grain boundaries, and copper forms second-phase particles to jointly suppress grain growth at high temperatures. Indium preferentially forms a dense oxide film, lanthanum purifies impurities and refines the initial grains, and antimony optimizes the wettability of the film layer to synergistically suppress oxidation. By suppressing grain growth, the fine and uniform microstructure of the electrode film layer can be maintained, ensuring uniform electron scattering and stable resistance, avoiding changes in the electric field of the excitation substrate due to resistance fluctuations. Suppressing oxidation can prevent irregular changes in electrode mass and volume and local differences in the coefficient of thermal expansion, thereby reducing the frequency drift of the crystal oscillator. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic flowchart of the high-temperature resistant coating method for crystal oscillators in the embodiments of this application.

[0018] Figure 2 This is one of the crystal oscillator structures in the embodiments of this application.

[0019] Figure 3 This is the second crystal oscillator structure in the embodiments of this application. Detailed Implementation

[0020] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without such specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods are omitted so as not to obscure the description of this application with unnecessary detail.

[0021] High-temperature crystal oscillators are specifically as follows: Figure 2 and Figure 3As shown, the crystal oscillator includes a base, a wafer, and a chip. The conductive circuitry inside the crystal oscillator enables the chip to form an electrical connection with the electrodes in the wafer and the base, thereby allowing the chip to process and control the resonant signal of the wafer.

[0022] In a first aspect, the present invention provides a silver-bismuth-copper alloy electrode material for a high-temperature crystal oscillator, the alloy material being composed of the following components by mass ratio: 96.80%≤Ag≤97.12%, 1.62%≤Bi≤2.14%, 0.96%≤Cu≤1.68%, 0.52%≤In≤0.90%, 0.20%≤La≤0.65%, and 0.12%≤Sb≤0.50%, the alloy material being used to prepare electrodes for a high-temperature crystal oscillator.

[0023] This application provides a silver-bismuth-copper alloy electrode material for high-temperature crystal oscillators and a high-temperature resistant coating method for crystal oscillators. The inventors have discovered that pure silver is prone to grain growth and oxidation, leading to electrode material defects. Traditional crystal oscillators experience frequency drift at high temperatures due to these defects. Therefore, this application proposes a multi-element alloy electrode material based on silver, with added bismuth, copper, indium, lanthanum, and antimony, along with a corresponding preparation and coating process. Silver ensures excellent electrode conductivity, bismuth pins grain boundaries, and copper forms second-phase particles to jointly suppress grain growth at high temperatures. Indium preferentially forms a dense oxide film, lanthanum purifies impurities and refines the initial grains, and antimony optimizes the film. The wettability of the layer synergistically inhibits oxidation. The vacuum induction melting process isolates gaseous impurities in a vacuum environment and achieves uniform composition through induction heating. Furnace cooling avoids internal stress and non-equilibrium structure in the alloy ingot. Subsequent processing into filaments or sheets is suitable for the uniform heating and vaporization requirements of the resistive evaporation source. Finally, a stable electrode film is formed after coating and annealing. By inhibiting grain growth, the fine and uniform microstructure of the electrode film can be maintained, ensuring uniform electron scattering and stable resistance. This avoids changes in the electric field of the excitation substrate due to resistance fluctuations. Inhibiting oxidation can prevent irregular changes in electrode mass and volume and local differences in thermal expansion coefficient, ultimately reducing the frequency drift of the crystal oscillator.

[0024] In this embodiment, the high-temperature crystal oscillator provides a reference frequency through the piezoelectric effect of the quartz crystal. The stability of the electrodes at high temperatures determines the frequency accuracy of the oscillator. Traditional pure silver electrodes have drawbacks: although pure silver has excellent conductivity, it is prone to grain growth, oxidation, and atomic migration at high temperatures, leading to changes in electrode quality, frequency drift, and even device failure. While gold electrodes are stable, their high cost makes them difficult to mass-produce. The alloy material of this invention is based on silver and incorporates bismuth, copper, indium, lanthanum, and other elements. In this way, bismuth can inhibit excessive growth of silver grains at high temperatures, copper can enhance the mechanical strength of the alloy, and indium, lanthanum, and antimony can optimize the alloy's film-forming properties and resistance to environmental corrosion.

[0025] It should be noted that the proportions of each component can be determined through multiple experiments to ensure that the electrode maintains low impedance while resisting performance degradation caused by thermal shock during high-temperature operation. This application is not limited to this; the alloy can also have its elemental proportions finely adjusted to suit different operating conditions based on the temperature requirements of specific applications.

[0026] Optionally, the alloy material has the following composition by mass ratio: Ag 97.0%, Bi 1.9%, Cu 1.2%, In 0.7%, La 0.4%, and Sb 0.3%.

[0027] Compared to other ratios, the alloy with this ratio, when used to make electrodes, showed significantly lower frequency changes after prolonged high-temperature testing.

[0028] Optionally, the alloy material is prepared by vacuum induction melting, wherein the vacuum degree in the vacuum induction melting furnace during the melting process is ≤5×10⁻⁶. -3 Pa, after melting, uses furnace cooling to form alloy ingots from the molten alloy.

[0029] In this embodiment, the vacuum induction melting process can solve the problem that metals easily react with oxygen and nitrogen in the air to form impurity phases during atmospheric pressure melting. After the furnace cooling melting is completed, the alloy melt is slowly cooled down with the furnace body to avoid rapid cooling causing internal stress or the formation of unstable metastable structures inside the alloy, thus ensuring the structural uniformity and mechanical properties of the alloy ingot.

[0030] During operation, the various metal raw materials are first loaded into the furnace, and a vacuum is drawn to the set state. Induction heating is then activated to melt the raw materials and the mixture is held at that temperature for a period of time to ensure uniform mixing. Heating is then stopped, and the molten metal is allowed to cool to room temperature with the furnace to form an alloy ingot. It should be noted that too low a vacuum will result in residual gas, affecting the purity of the alloy; too high a vacuum will increase the processing cost.

[0031] Optionally, the crystal substrate adapted to the alloy material is an AT-cut quartz crystal substrate, and the substrate has a size of 8×8×0.3mm.

[0032] In this embodiment, the AT-cut quartz crystal substrate is a substrate formed by cutting a quartz crystal at a specific angle, such as a fixed angle with the Z-axis. Quartz crystals are anisotropic, and substrates with different cutting angles have significant differences in temperature stability and frequency characteristics. The AT-cut substrate has excellent frequency stability over a wide temperature range because its frequency-temperature characteristic curve is a flat cubic curve. The thermal expansion coefficient of the alloy material in this application is similar to that of the AT-cut substrate. When the oscillator operates at high temperature, the expansion degree of the electrode and the substrate is consistent, which can reduce the stress difference between the two and avoid frequency drift caused by substrate deformation.

[0033] Optionally, the alloy ingot is machined to form a raw material form suitable for a resistive evaporation source, wherein the raw material form is a filament with a diameter of 0.5-1.0 mm or a sheet with a thickness of 0.1-0.3 mm.

[0034] In this embodiment, machining is a process that changes the shape of the alloy ingot through physical means such as cutting, stretching, and rolling, processing the block alloy ingot into a shape that meets the requirements of the coating equipment. The resistance evaporation source vaporizes the evaporation material by heating with current. During use, the alloy ingot is first pre-cut to remove the surface oxide layer, then stretched into filaments or rolled into sheets, and finally cut to a length or size suitable for the evaporation source.

[0035] For example, filamentous materials can be wound around a spiral tungsten wire, and sheet-like materials can be placed in the crucible of the evaporation source.

[0036] Secondly, the present invention provides a high-temperature resistant coating method for a crystal oscillator based on the silver-bismuth-copper alloy electrode material described above, such as... Figure 1 As shown, it includes the following steps: 101: Take silver-bismuth-copper alloy electrode material and process it into a raw material form suitable for resistive evaporation source; 102: Place the quartz crystal substrate in an ultrasonic cleaner and clean it with deionized water, then dehydrate it with anhydrous ethanol, dry it, and then put it into a special coating fixture. 103: Place the fixture containing the substrate into a continuously rotating vacuum crystal coating machine, and evacuate the coating chamber to a vacuum level of 2×10⁻⁶. -6 Below Pa, heat the substrate to 150-200℃, start the resistance evaporation source, control the film deposition rate to 0.5-1.5nm / s, and simultaneously drive the fixture to rotate until the total film thickness reaches 100-150nm; 104: Perform annealing treatment. Transfer the coated substrate to the annealing equipment and heat it to 250-300℃ under vacuum or inert gas protection. Hold it at that temperature for 30-60 minutes and then cool it to room temperature in the furnace.

[0037] In this embodiment, during substrate pretreatment, an ultrasonic cleaner utilizes the cavitation effect of ultrasound to efficiently remove impurities such as oil and dust from the substrate surface. These impurities severely affect the adhesion between the film layer and the substrate, leading to film detachment. The volatility of ethanol removes moisture from the substrate surface. After drying, the substrate is placed in a dedicated coating fixture, which can fix the substrate and allow it to be flipped. In the vacuum coating step, the vacuum crystal coating machine integrates functions such as vacuuming, heating, evaporation, and substrate driving. Vacuuming to a specific degree ensures that vaporized metal atoms can move linearly to the substrate surface, reducing collisions with gas molecules and improving film density. Heating the substrate increases the adsorption force of metal atoms on the substrate surface, enhancing film adhesion. Driving the fixture to flip allows simultaneous coating on both sides of the substrate, ensuring uniform film thickness. Annealing is a key optimization step after coating. Heating under vacuum or inert gas protection can eliminate residual stress inside the film and optimize the grain structure. The film formed during the coating process may have problems such as uneven grain size and large internal stress. Annealing can promote grain rearrangement, inhibit secondary crystallization, and improve the high-temperature stability of the film. Furnace cooling avoids the generation of new internal stress due to rapid cooling.

[0038] Optionally, the deionized water washing time is 15 minutes, the anhydrous ethanol dehydration time is 10 minutes, and the drying method is to blow dry with nitrogen gas with a purity of ≥99.99%.

[0039] Optionally, the vacuum level of the coating chamber is controlled to be 1.5 × 10⁻⁶. -6 Pa, substrate heating temperature is 180℃, film deposition rate is stable at 1.0nm / s, fixture flipping angle range is 60°-120°, flipping speed is 5 times per minute, and deposition time is 120 seconds.

[0040] It should be noted that these parameters need to be fine-tuned according to the specific coating equipment model and alloy material characteristics, and are not fixed. This application is not limited to this; for substrates of different sizes, the flipping speed and deposition time can be adjusted appropriately to ensure uniform thickness.

[0041] Optionally, the annealing process has a heating rate of 5°C / min, a holding time of 45 minutes, and a rate at which the substrate is cooled to room temperature in the furnace after annealing ≤10°C / min.

[0042] Optionally, the resistive evaporation source is a tungsten wire resistive evaporation source, wherein the diameter of the tungsten wire is 0.3-0.5 mm, and the tungsten wire is wound into a spiral shape with a spiral diameter of 3-5 mm.

[0043] In addition to tungsten wire, other high-melting-point metal wires such as molybdenum wire and tantalum wire can also be used as the heating element of the resistance evaporation source, and this application is not limited to this.

[0044] Below is a specific scenario example. 1. Material preparation Prepare electrode materials according to the following mass ratio: 97.0% silver, 1.9% bismuth, 1.2% copper, 0.7% indium, 0.4% lanthanum, and 0.3% antimony. Melt the above high-purity metal raw materials in a vacuum induction melting furnace to prepare alloy ingots.

[0045] 2. Substrate preprocessing AT-cut quartz crystal substrates with dimensions of 8×8×0.3mm were selected. The substrates were cleaned with deionized water in an ultrasonic cleaner for 15 minutes, then dehydrated with anhydrous ethanol for 10 minutes, dried with nitrogen, and then placed in a special coating fixture.

[0046] 3. Vacuum coating Coating is performed using a vacuum crystal coating machine: 1. Evacuate the coating chamber to 1.5 × 10⁻⁶ Pa; 2. Heat the crystal substrate to 180℃; 3. A resistance heating evaporation source is used, and the evaporation current is controlled to stabilize the deposition rate at 1.0 nm / s; 4. Activate the clamp rotation system to rotate the clamp within the range of 60°-120° at a speed of 5 times per minute; 5. The deposition time is 120 seconds, resulting in an electrode film with a thickness of approximately 120 nm.

[0047] 4. Annealing treatment The coated crystal substrate is annealed under vacuum conditions: the temperature is increased to 280°C at a rate of 5°C / min, held for 45 minutes, and then cooled to room temperature in the furnace.

[0048] 5. Performance Testing The performance of the fabricated crystal oscillator was tested: • Frequency stability: ±4.5×10⁻⁶ (-40℃ to +85℃) • Electrode film thickness uniformity: deviation ±2.5% • High-temperature life test: 1000 hours at 125℃, frequency drift less than ±0.5ppm. A crystal oscillator was fabricated using traditional pure silver electrodes and a conventional coating process, with other conditions identical to the scenario example. Test results: • Frequency stability: ±8.5×10⁻⁶ (-40℃ to +85℃) • Electrode film thickness uniformity: deviation ±8.5% • High-temperature life test: 1000 hours at 125℃, frequency drift reached ±3.2ppm.

[0049] Specific embodiments have been used to illustrate the principles and implementation methods of this invention. The descriptions of the embodiments above are only for the purpose of helping to understand the methods and ideas of this invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this invention. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A silver-bismuth-copper alloy electrode material for high-temperature crystal oscillators, characterized in that, The alloy material is composed of the following components by mass ratio: 96.80%≤Ag≤97.12%, 1.62%≤Bi≤2.14%, 0.96%≤Cu≤1.68%, 0.52%≤In≤0.90%, 0.20%≤La≤0.65%, and 0.12%≤Sb≤0.50%. The alloy material is used to prepare electrodes for high-temperature crystal oscillators.

2. The silver-bismuth-copper alloy electrode material for high-temperature crystal oscillators according to claim 1, characterized in that, The alloy material has the following composition by mass ratio: Ag 97.0%, Bi 1.9%, Cu 1.2%, In 0.7%, La 0.4%, and Sb 0.3%.

3. The silver-bismuth-copper alloy electrode material for high-temperature crystal oscillators according to claim 1 or 2, characterized in that, The alloy material is prepared by vacuum induction melting process, wherein the vacuum degree in the vacuum induction melting furnace during the melting process is ≤5×10⁻⁶. -3 Pa, after melting, uses furnace cooling to form alloy ingots from the molten alloy.

4. The silver-bismuth-copper alloy electrode material for high-temperature crystal oscillators according to claim 1 or 2, characterized in that, The crystal substrate used to adapt the alloy material is an AT-cut quartz crystal substrate with dimensions of 8×8×0.3mm.

5. The silver-bismuth-copper alloy electrode material for a high-temperature crystal oscillator according to claim 1 or 2, characterized in that, The alloy ingot is machined to form a raw material form suitable for a resistive evaporation source. The raw material form is a filament with a diameter of 0.5-1.0 mm or a sheet with a thickness of 0.1-0.3 mm.

6. A method for high-temperature resistant coating of a crystal oscillator based on the silver-bismuth-copper alloy electrode material according to any one of claims 1-5, characterized in that, Includes the following steps: Silver-bismuth-copper alloy electrode material is processed into a raw material form suitable for resistive evaporation sources; The quartz crystal substrate is placed in an ultrasonic cleaner and cleaned with deionized water, then dehydrated with anhydrous ethanol, dried, and then placed in a special coating fixture. The fixture containing the substrate is placed into a continuously rotating vacuum crystal coating machine, and a vacuum is drawn to achieve a vacuum level of 2×10⁻⁶ in the coating chamber. -6 Below Pa, heat the substrate to 150-200℃, start the resistance evaporation source, control the film deposition rate to 0.5-1.5nm / s, and simultaneously drive the fixture to rotate until the total film thickness reaches 100-150nm; Annealing is performed by transferring the coated substrate to an annealing apparatus and heating it to 250-300℃ under vacuum or inert gas protection. After holding at that temperature for 30-60 minutes, the substrate is cooled to room temperature in the furnace.

7. The high-temperature resistant coating method for crystal oscillators according to claim 6, characterized in that, The deionized water cleaning time is 15 minutes, the anhydrous ethanol dehydration time is 10 minutes, and the drying method is to blow dry with nitrogen gas with a purity of ≥99.99%.

8. The high-temperature resistant coating method for crystal oscillators according to claim 6 or 7, characterized in that, The vacuum level of the coating chamber is controlled at 1.5 × 10⁻⁶. -6 Pa, substrate heating temperature is 180℃, film deposition rate is stable at 1.0nm / s, fixture flipping angle range is 60°-120°, flipping speed is 5 times per minute, and deposition time is 120 seconds.

9. The high-temperature resistant coating method for crystal oscillators according to claim 6 or 7, characterized in that, The annealing process has a heating rate of 5°C / min and a holding time of 45 minutes. After annealing, the substrate is cooled to room temperature at a rate of ≤10°C / min.

10. The high-temperature resistant coating method for crystal oscillators according to claim 6 or 7, characterized in that, The resistive evaporation source is a tungsten wire resistive evaporation source, the diameter of the tungsten wire is 0.3-0.5 mm, and the tungsten wire is wound into a spiral shape with a spiral diameter of 3-5 mm.

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