A quartz crystal
By employing gradient electrodes and a nickel-chromium alloy transition layer in the quartz crystal, the problems of high aging rate, poor mechanical strength, and high cost of mid-to-high frequency crystals have been solved, thereby improving frequency stability and cost-effectiveness.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- 浙江鸿星电子科技有限公司
- Filing Date
- 2025-04-16
- Publication Date
- 2026-06-09
AI Technical Summary
Existing quartz crystals suffer from high aging rate, poor mechanical strength, difficulty in packaging and matching, and high cost in the mid-to-high frequency range, making it difficult to meet the requirements of high frequency and low aging rate.
A gradient electrode structure is adopted, using nickel-chromium alloy as the transition layer electrode, combined with vacuum packaging technology to alleviate thermal expansion differences and packaging stress, and reduce interface stress concentration and contaminant penetration.
The annual aging rate of mid-to-high frequency crystals has been reduced to ±1ppm, frequency drift has been reduced, mechanical strength has been improved, and manufacturing costs have been reduced.
Smart Images
Figure CN224343151U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of quartz crystal technology, and in particular to a quartz crystal. Background Technology
[0002] In electronic devices and communication systems, the stability of clock signals is a core element ensuring the accurate operation of the system. The annual aging rate, as a key indicator of clock signal stability, indicates higher long-term stability with a lower value. This is crucial for applications requiring precise time synchronization, such as data transmission and digital signal processing. With the rapid development of 5G communication, the Internet of Things, and high-performance computing technologies, the industry's requirements for the frequency stability and accuracy of clock signals are continuously upgrading, and the standards for controlling the annual aging rate of quartz crystals are becoming increasingly stringent. For example, for quartz crystals with commonly used frequencies such as 40MHz, 48MHz, and 50MHz, the first-year aging rate requirement has been gradually optimized from ±5ppm to ±1ppm to meet the nanosecond-level time synchronization accuracy requirements of modern communication systems.
[0003] The frequency aging phenomenon of quartz crystal elements is essentially a physical process in which their resonant frequency shifts over time. The annual aging rate comprehensively reflects the characteristics of the crystal material, the processing technology, and the packaging quality. From a technical mechanism perspective, aging mainly stems from the stress relaxation effect (the release of residual stress within the crystal over time, leading to frequency drift) and the mass adsorption effect (the adsorption of gas or water molecules on the wafer surface alters the equivalent mass). To reduce the aging rate, crystal manufacturers construct high-cleanliness production lines, optimize high-temperature annealing processes to eliminate internal stress, employ vacuum packaging technology to isolate the oxidation environment, and strictly control the exposure time of electrode materials in air to prevent secondary contamination. Currently, crystals using silver electrodes can achieve excellent aging performance of ±1 ppm / year in the low-frequency range (e.g., 32.768 kHz), but typically only ±2 ppm / year in the mid-to-high frequency range (e.g., above 40 MHz).
[0004] The existing technology has the following limitations:
[0005] Bottleneck of aging rate in mid-to-high frequency crystals: Because mid-to-high frequency crystals require thinner quartz wafers (typically <0.05mm thick) to achieve high-frequency vibration, their mechanical strength is significantly reduced, making them more sensitive to environmental factors such as temperature fluctuations and mechanical vibrations. The difference between the thermal expansion coefficient of the thin wafer and the electrode material (such as silver) causes significant interfacial stress, leading to increased frequency drift.
[0006] Surface effects become more prominent: thin wafers have a larger surface area to volume ratio, and the influence of surface adsorption effects (such as the adsorption of water molecules and organic matter in the atmosphere) on the resonant frequency increases exponentially. Furthermore, surface defects (such as microcracks and edge roughness) are more likely to expand during long-term use, accelerating performance degradation.
[0007] Packaging matching challenge: High-stability materials (such as ceramics and metals) are required for the packaging of medium and high frequency crystals, but the difficulty of matching the coefficient of thermal expansion (CTE) between thin wafers and packaging materials increases, and the release of interface stress after long-term use causes frequency shift.
[0008] Cost constraints: Although gold electrodes can significantly improve the aging performance of mid-to-high frequency crystals (CTE is closer to quartz), the high price of gold has led to a surge in manufacturing costs, limiting its widespread use in the civilian sector.
[0009] The aforementioned technical bottlenecks indicate that existing quartz crystal technology faces multiple contradictions in terms of material properties, process control, and cost-effectiveness when meeting the requirements of high frequency and low aging rate, and innovative solutions are urgently needed to break through the existing technical framework. Utility Model Content
[0010] To address the problems existing in the prior art, this utility model provides a quartz crystal, comprising:
[0011] A base, wherein a base cavity is provided in the base, and the top of the base cavity is open and covered with a top cover;
[0012] A wafer is attached to the bottom of the base cavity, and gradient electrodes are deposited on the upper and lower surfaces of the wafer.
[0013] Preferably, the gradient electrode includes an electrode and a transition layer electrode, wherein the transition layer electrode is disposed between the electrode and the wafer.
[0014] Preferably, the electrode is made of metallic silver.
[0015] Preferably, the material used to prepare the transition layer electrode includes a chromium-containing material.
[0016] Preferably, the transition layer electrode is made of a nickel-chromium alloy.
[0017] Preferably, the nickel-chromium mass ratio of the nickel-chromium alloy is 80:20.
[0018] Preferably, the bottom of the base cavity is provided with an adhesive block, and one end of the wafer is electrically bonded to the adhesive block by conductive adhesive.
[0019] The above technical solution has the following advantages or beneficial effects:
[0020] 1. Gradient electrodes are used to buffer differences in thermal expansion, reduce interface stress concentration, and reduce frequency drift, thereby reducing the annual aging rate.
[0021] 2. Gradient electrodes can enhance the bonding strength between the electrode and the wafer, reducing the risk of interface peeling.
[0022] 3. Reduce the risk of microcracks and peeling at the electrode-wafer interface, and reduce the probability of surface contamination penetration. Attached Figure Description
[0023] Figure 1 This is a schematic diagram of the structure of a quartz crystal in a preferred embodiment of the present invention.
[0024] Figure 2 In a preferred embodiment of this utility model, the test data trend chart of test scheme one is shown.
[0025] Figure 3 In a preferred embodiment of this utility model, the test data trend chart of test scheme two is shown.
[0026] Figure 4 In a preferred embodiment of this utility model, the test data trend chart of test scheme three is shown.
[0027] Figure 5 In a preferred embodiment of this utility model, the test data trend chart of test scheme four is shown. Detailed Implementation
[0028] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The present invention is not limited to this embodiment; other embodiments that conform to the spirit of the present invention may also fall within its scope.
[0029] In a preferred embodiment of this utility model, based on the above-mentioned problems existing in the prior art, a quartz crystal for reducing the annual aging rate is provided, comprising:
[0030] Base a, base a has a base cavity, the top of the base cavity is open and covered with a top cover c;
[0031] Wafer d is attached to the bottom of the substrate cavity, and gradient electrodes are deposited on the upper and lower surfaces of wafer d.
[0032] In a preferred embodiment of the present invention, the gradient electrode includes an electrode d2 and a transition layer electrode d1, wherein the transition layer electrode d1 is disposed between the electrode d2 and the wafer d.
[0033] Preferably, the bottom of the base cavity is provided with an adhesive block e, and one end of the wafer d is electrically bonded to the adhesive block e through conductive adhesive b.
[0034] like Figure 1 As shown in the diagram, the quartz crystal structure includes a base a, conductive adhesive b, a top cover c, and a wafer d. A metal film is sputtered onto the wafer to form a gradient electrode (transition layer electrode d1 + electrode d2), which is bonded to the base cavity by conductive adhesive b. Finally, the wafer d is encapsulated by the top cover c, completing the connection between the wafer d inside and outside the base a.
[0035] Specifically, addressing the bottleneck of aging rate in existing high-frequency crystal technologies, high-frequency crystals require the use of thin wafers (thickness < 0.05 mm), while the CTE of traditional silver electrodes (19.5 × 10⁻⁻⁻⁶) is much higher. 6 / ℃) is much higher than that of the quartz wafer along the Z-axis (7.1×10⁻ 6 / ℃). When the temperature fluctuates, the difference in the degree of expansion between the electrode and the wafer causes interfacial stress. Long-term stress release leads to wafer deformation and exacerbates frequency drift.
[0036] This invention employs a gradient electrode, such as a nickel-chromium alloy (nickel 80-chromium 20, CTE=13.5×10⁻). 6 A gradient-matched layer (CTE) is used as a transition layer between the quartz wafer (Z-axis) and the silver electrode. This gradient-matched design buffers differences in thermal expansion and reduces interfacial stress concentration.
[0037] Furthermore, the surface of thin wafers is prone to microcracks due to mechanical vibration or thermal cycling. When the adhesion between the electrode and the wafer is insufficient, the cracks expand and accelerate the adsorption of contaminants, further altering the equivalent mass and causing frequency shift.
[0038] In this invention, the gradient electrode enhances the bonding strength between the electrode and the wafer, reducing the risk of interface delamination. It also reduces the risk of microcracks and delamination at the electrode-wafer interface, lowering the probability of surface contamination penetration. The chemical stability of the nickel-chromium alloy further prevents oxidation and contamination penetration.
[0039] Furthermore, the encapsulation material (such as ceramic, CTE≈15×10⁻) 6 The difference in CTE between the quartz crystal and the quartz wafer (at / ℃) leads to long-term interfacial stress release, exacerbating frequency drift.
[0040] In this invention, a gradient electrode, such as a nickel-chromium alloy, is used as the transition layer electrode, with a CTE (13.5 × 10⁻⁻⁴). 6 ( / ℃) is located between the wafer and the packaging material, reducing the thermal expansion gradient and mitigating the impact of packaging stress on the wafer.
[0041] Furthermore, the high surface area to volume ratio of thin wafers makes them extremely sensitive to surface contamination (such as water molecule adsorption). Contaminants alter the equivalent mass of the wafer, leading to frequency shifts.
[0042] In this invention, the highly adhesive transition layer reduces microcracks and surface roughness, thereby lowering the probability of pollutant adsorption. Simultaneously, the vacuum encapsulation process, combined with the chemical stability of the transition layer, further isolates environmental pollutants.
[0043] In a preferred embodiment of this invention, the electrode is made of metallic silver.
[0044] In a preferred embodiment of this invention, the transition layer electrode is made of a chromium-containing material.
[0045] In a preferred embodiment of this invention, the transition layer electrode is made of a nickel-chromium alloy.
[0046] Specifically, under the same environmental conditions and process level, the aging rate of medium and high frequency crystals is usually worse than that of low frequency crystals. This is related to their physical structure and material properties. The industry generally selects silver electrode materials for such low aging rate requirements of medium and high frequency products. This invention is designed from two aspects: the difference in thermal expansion coefficient between the electrode and the wafer, and the pre-aging process.
[0047] The coefficients of thermal expansion (@20℃~100℃) of commonly used electrode materials with good electrical conductivity are shown in Table 1:
[0048]
[0049] Table 1
[0050] Based on the adhesion of gold and silver to quartz in the table above, gold and silver have relatively poor adhesion, while chromium has relatively strong adhesion. In terms of matching the thermal expansion coefficient of the material with the quartz wafer, gold is superior to silver. Among expansion-inhibiting materials, nickel-chromium is the best. In terms of chemical stability, nickel is the worst and unsuitable. Gold electrodes have excellent performance but are expensive and difficult to popularize, so silver is chosen as the electrode material.
[0051] Therefore, in this invention, a nickel-chromium alloy is used as the electrode transition layer. Specifically, in the preferred embodiment: the nickel-chromium alloy buffer layer uses Ni80Cr20 alloy as the secondary transition layer, with a thermal expansion coefficient (CTE≈14.5×10⁻⁻¹). 6 / ℃) and quartz (CTE≈13.8×10⁻ 6 ( / ℃) Highly matched, function:
[0052] 1. Reduce the CTE mismatch of the electrode-wafer system from 55% for the silver electrode to 8%.
[0053] 2. During temperature cycling tests from -55℃ to 125℃, the frequency offset decreased by 72%.
[0054] 3. XRD analysis confirmed that this alloy can effectively suppress phase transitions in wafers during thermal cycling.
[0055] Furthermore, pre-aging processes play a crucial role in electronic device manufacturing. They simulate harsh conditions that electronic components might encounter in real-world use, such as high temperatures and reverse bias, effectively "aging" the components beforehand. This process effectively releases internal stress, reducing the likelihood of failure during actual use. By optimizing aging process parameters, not only can device performance and lifespan be improved, but it also ensures that electronic components maintain stable performance even in harsh environments, meeting users' demands for high-quality electronic products.
[0056] Taking a 3.2*2.5-inch WIFI 6 product with a mid-to-high frequency of 40MHz as the research object, and aiming to achieve ±1ppm aging in the first year, this utility model conducts experiments by combining different electrode transition materials and pre-aging schemes.
[0057] Test verification method: Refer to GB-T 12273 standard
[0058] Specifically, the test data was collected on the 14th, 30th, 60th, 90th, ... 240th day using a 125℃ high-temperature charged device (100uW excitation).
[0059] Test Plan 1:
[0060] Table 2 shows the test conditions for Test Plan 1.
[0061]
[0062] The test results for Scheme 1 are shown in Table 3 and Figure 2 As shown.
[0063] Table 3. Test Results of Frequency Change under Test Scheme 1 at 125℃
[0064]
[0065] Test Plan Two:
[0066] Table 4 shows the test conditions for Test Plan 2.
[0067]
[0068] The test results for Scheme 2 are shown in Table 5 and Figure 3 As shown.
[0069] Table 5. Test Results of Frequency Change under Test Scheme 2 at 125℃
[0070]
[0071] Test Plan 3:
[0072] Table 6 shows the test conditions for Test Plan 3.
[0073]
[0074] The test results for Scheme 3 are shown in Table 7 and Figure 4 As shown.
[0075]
[0076] Table 7. Test Results of Frequency Change under Test Scheme 3 at 125℃
[0077] Test Plan Four:
[0078] Table 8 shows the test conditions for Test Plan 4.
[0079]
[0080] The test results for Scheme 4 are shown in Table 9 and Figure 5 As shown.
[0081] Table 9. Test Results of Frequency Change under Test Scheme 4 at 125℃
[0082]
[0083] From Tables 3, 5, 7, and 9, and Figures 2-5 The data trends show that:
[0084] Test Plan 1: Long-term (240 days) aging at 125℃ with a frequency close to -12ppm.
[0085] Test scheme two: long-term (240 days) @ 125℃ aging frequency close to -10ppm.
[0086] Test Plan 3: Long-term (240 days) aging at 125℃ with a frequency close to -9ppm.
[0087] Test Plan 4: Long-term (240 days) aging at 125℃ with a frequency close to -6ppm.
[0088] According to the GB-T 12273 standard, the frequency change of a quartz crystal at 125℃ for 9 days is considered equivalent to the frequency change of an aging crystal at 25℃ for 1 year.
[0089] Based on the test data from day 14, it was found that test schemes 2 and 4 had the smallest frequency variations. Among them, test scheme 4 had the best worst value, which met the ±1ppm requirement.
[0090] In other words, the annual aging of the product in test scheme four meets ±1ppm, and its long-term aging frequency change meets ±6ppm. This indicates that the gradient electrode structure used in this invention, with nickel-chromium alloy as the transition layer electrode and metallic silver as the electrode, has the excellent performance of reducing the annual aging rate to ±1ppm / year.
[0091] The above are merely preferred embodiments of the present utility model and are not intended to limit the implementation methods and protection scope of the present utility model. Those skilled in the art should realize that any equivalent substitutions and obvious changes made using the content of this specification and illustrations should be included within the protection scope of the present utility model.
Claims
1. A quartz crystal, characterized in that, include: A base, wherein a base cavity is provided in the base, and the top of the base cavity is open and covered with a top cover; A wafer is attached to the bottom of the base cavity, and gradient electrodes are deposited on the upper and lower surfaces of the wafer.
2. The quartz crystal according to claim 1, characterized in that, The gradient electrode includes an electrode and a transition layer electrode, wherein the transition layer electrode is disposed between the electrode and the wafer.
3. The quartz crystal according to claim 2, characterized in that, The electrode is made of metallic silver.
4. The quartz crystal according to claim 2, characterized in that, The transition layer electrode is made of chromium-containing materials.
5. The quartz crystal according to claim 4, characterized in that, The transition layer electrode is made of a nickel-chromium alloy.
6. The quartz crystal according to claim 1, characterized in that, The bottom of the base cavity is provided with an adhesive block, and one end of the wafer is electrically bonded to the adhesive block by conductive adhesive.