A quartz crystal

Abstract

The utility model provides a quartz crystal relates to quartz crystal technical field, including base, the base is opened in the base cavity that has the cover plate, wafer, the upper and lower surface of wafer all form the silver gold alloy electrode of gradient structure, and one end of wafer is bonded in the base cavity through conductive glue. Advantageous effect is that the silver gold alloy with good thermal expansion coefficient matching, excellent stability and medium price is used as electrode main material in the quartz crystal, which reduces the electrode cost under the performance premise of meeting the low aging rate of medium and high frequency products.

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 the field of quartz crystal components, frequency stability over time is a core indicator for evaluating device performance, while the aging effect remains a key technological bottleneck restricting the development of high-precision crystal products. Research indicates that the aging rate primarily stems from two physical effects: stress relaxation (residual stress release triggered by lattice restructuring) and mass adsorption (interaction between the electrode surface and ambient gas molecules). Although silver electrode materials are widely used in low-frequency crystals (<30MHz) due to their cost advantage, their aging rate has long remained stagnant at ±1ppm / year. Notably, when the operating frequency increases to the mid-to-high frequency range (>60MHz), the aging rate of silver electrodes increases significantly due to its coefficient of thermal expansion (CTE = 19.5 × 10⁻⁻¹). 6 / ℃) and quartz wafer (Z-axis CTE=7.1×10⁻ 6 Significant mismatch ( / ℃) leads to a sharp increase in interfacial stress and a deterioration in aging rate to over ±2ppm / year, severely limiting the long-term stability of high-frequency devices.

[0003] To overcome this limitation, the industry once turned to gold as a high-frequency electrode material, whose superior properties are reflected in:

[0004] Thermal compatibility: The coefficient of thermal expansion of gold is 14.2 × 10⁻⁻⁻⁶. 6 / ℃) more closely resembles the anisotropic properties of quartz crystals (X / Y axis 13.7×10⁻ 6 / ℃);

[0005] Chemical inertness: Its antioxidant capacity is significantly better than that of silver, and its mass adsorption effect is reduced by about 40%.

[0006] Interface stability: The bonding adhesion with quartz wafers is improved to 80% of that of nickel-chromium alloys.

[0007] Based on the aforementioned characteristics, gold electrodes can optimize the first-year aging rate of high-frequency crystals to ±1ppm. However, this approach has a fatal flaw: the international gold price has fluctuated dramatically in recent years (with an increase of over 35% from 2020 to 2023), leading to a surge in the production cost of high-frequency crystals, with the unit price of devices increasing by 2-3 times compared to the silver electrode approach. This sharp contradiction between material cost and performance indicators forces the industry into a dilemma—either bear the high cost to maintain high-frequency performance, or sacrifice stability for controllable costs, severely restricting the technological iteration of high-frequency application scenarios such as 5G communication and WIFI 7. Utility Model Content

[0008] To address the problems existing in the prior art, this utility model provides a quartz crystal, comprising:

[0009] A base, wherein a base cavity covered by a cover plate is provided;

[0010] The wafer has silver-gold alloy electrodes formed on both its upper and lower surfaces, and one end of the wafer is bonded to the cavity of the base by conductive adhesive.

[0011] Preferably, the mass ratio of silver to gold in the silver-gold alloy electrode is 75:25.

[0012] Preferably, the silver-gold alloy electrode is also doped with platinum, and the mass ratio of silver, gold and platinum is 75:25:(1~3).

[0013] Preferably, a transition layer electrode is provided between the silver-gold alloy electrode and the wafer.

[0014] Preferably, the transition layer electrode is a nickel-chromium-titanium alloy with a nickel:chromium mass ratio of 20:80.

[0015] Preferably, the silver-gold alloy electrode has a gradient structure, including a substrate contact layer and a surface layer, wherein the substrate contact layer is located between the surface layer and the wafer.

[0016] Preferably, the thickness ratio of the substrate contact layer to the surface layer is 2:1.

[0017] Preferably, the substrate contact layer is made of a silver-gold-platinum alloy, and the surface layer is made of pure silver.

[0018] The above technical solution has the following advantages or beneficial effects:

[0019] In quartz crystals, a silver-gold alloy with a good matching coefficient of thermal expansion, excellent stability, and moderate price is used as the main electrode material. This reduces electrode costs while meeting the performance requirements of low annual aging rate for medium and high frequency products. Attached Figure Description

[0020] Figure 1 A schematic diagram of the structure of a quartz crystal is shown in a preferred embodiment of this utility model.

[0021] Figure 2 In a preferred embodiment of this utility model, the experimental data trend chart of Scheme 1 is shown.

[0022] Figure 3 In a preferred embodiment of this utility model, the experimental data trend graph of Scheme 2 is shown.

[0023] Figure 4 In a preferred embodiment of this utility model, the experimental data trend chart of Scheme 3 is shown. Detailed Implementation

[0024] 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.

[0025] In a preferred embodiment of this utility model, based on the above-mentioned problems existing in the prior art, a quartz crystal is provided, comprising:

[0026] Base a, wherein a base cavity covered by a cover plate c is provided in base a;

[0027] A wafer d, wherein a gradient structure of silver-gold alloy electrode d2 is formed on both the upper and lower surfaces of the wafer d, and one end of the wafer d is bonded to the cavity of the base by conductive adhesive b.

[0028] In a preferred embodiment of this invention, the mass ratio of silver to gold in the silver-gold alloy electrode d2 is 75:25.

[0029] In a preferred embodiment of this invention, a transition layer electrode d1 is provided between the silver-gold alloy electrode d2 and the wafer d.

[0030] Specifically, as mentioned in the background technology, the rise in gold prices has brought enormous cost pressure. The coefficient of thermal expansion (@20℃~100℃) of commonly used electrode materials with good conductivity is shown in the table below:

[0031] Table 1. Coefficient of Expansion of Electrode Materials

[0032]

[0033] Based on the matching of the thermal expansion coefficients of the materials with quartz wafers in the table above: among the three main materials, gold is the best, followed by silver-gold, with silver being the worst; among the expansion-inhibiting materials, nickel-chromium is the best, followed by nickel, with chromium being the worst. In terms of chemical stability: among the three main materials, gold is the best, followed by silver-gold, with silver being the worst; among the expansion-inhibiting materials, chromium is the best, followed by nickel-chromium, with nickel being the worst. Regarding adhesion to quartz: gold, silver-gold, and silver are all relatively poor among the three main materials, while chromium has relatively strong adhesion and high chemical properties.

[0034] Therefore, in a preferred embodiment of this utility model, a silver-gold alloy with a good matching coefficient of thermal expansion, excellent stability, and moderate price is used as the main electrode material.

[0035] Furthermore, a nickel-chromium alloy with excellent adhesion was selected as the transition layer electrode.

[0036] As a preferred option, we selected a nickel-chromium-titanium alloy with a good coefficient of thermal expansion as the suppressor material for the transition layer.

[0037] like Figure 1 As shown, 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 electrodes d1 / d2, which are then bonded to the base cavity by the conductive adhesive. Finally, the wafer d is encapsulated by the top cover c, completing the connection between the wafer d inside and outside the base a.

[0038] Pre-aging processes play a crucial role in electronic device manufacturing. They simulate harsh conditions 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 the stable performance of electronic components under harsh environments can also be ensured, meeting users' demands for high-quality electronic products.

[0039] Multiple design schemes were tested and verified, while other processes remained unchanged, as shown in Table 2.

[0040] Table 2 Scheme Design Table

[0041]

[0042] Test verification method: Refer to GB-T 12273 standard

[0043] Specifically, the test data was collected on the 14th, 30th, 60th and 90th days using a 125℃ high-temperature charged device (100uW excitation).

[0044] The test data for Scheme (1) is shown in Table 3. Figure 2 As shown;

[0045] Table 3. Test Results of Frequency Change at 125℃ for Scheme (I)

[0046]

[0047] The test data for scheme (II) is shown in Table 4. Figure 3 As shown;

[0048] Table 4. Test Results of Frequency Change at 125℃ for Scheme (II)

[0049]

[0050] The test data for scheme (3) is shown in Table 5. Figure 4 As shown;

[0051] Table 5. Test Results of Frequency Change at 125℃ for Scheme (III)

[0052]

[0053] From Tables 3-5 and Figures 2-4 It can be seen that Scheme (II) and Scheme (III) are significantly better than Scheme (I).

[0054] 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.

[0055] Referring to the test data on day 14, we found that both scheme (II) and scheme (III) met ±1ppm, and the long-term (90 days) @125℃ aging frequency met ±2ppm; among them, scheme (III) was better, and its aging trend line gradually flattened after 60 days.

[0056] The data above shows that this utility model invention, namely the design of the combined silver-gold alloy electrode and gradient pre-aging scheme, can achieve the requirement of a low aging rate of ±1ppm for high-frequency quartz products.

[0057] In a preferred embodiment of this invention, the silver-gold alloy electrode is also doped with platinum, and the mass ratio of silver, gold, and platinum is 75:25:(1~3).

[0058] Specifically, in this embodiment, a trace amount of platinum (Pt, 1%~3%) is introduced into a silver-gold alloy (Ag:Au=75:25) to form a ternary alloy (Ag-Au-Pt). Platinum has better chemical stability than silver and gold, which can suppress electrode oxidation, while its coefficient of thermal expansion (8.8×10⁻⁻⁶) is also superior. 6 / ℃) is closer to the Z-axis of a quartz wafer (7.1×10⁻ 6 / ℃), further reducing the stress relaxation effect.

[0059] Platinum doping of the main electrode can reduce the mass adsorption effect at high temperatures, and the long-term aging rate is expected to be reduced to ±0.8 ppm / year.

[0060] In a preferred embodiment of this invention, the transition layer electrode is a nickel-chromium alloy with a nickel:chromium mass ratio of 20:80.

[0061] Enhanced adhesion of the transition layer reduces the risk of delamination and improves device reliability.

[0062] In a preferred embodiment of this invention, the silver-gold alloy electrode includes a substrate contact layer and a surface layer, wherein the substrate contact layer is located between the surface layer and the wafer.

[0063] In a preferred embodiment of this invention, the thickness ratio of the substrate contact layer to the surface layer is 2:1.

[0064] In a preferred embodiment of this invention, the substrate contact layer is made of a silver-gold-platinum alloy, and the surface layer is made of pure silver.

[0065] Specifically, the silver-gold main electrode layer was changed from a homogeneous 145nm layer to a gradient design (substrate contact layer: 100nm Ag-Au-Pt + surface layer: 45nm pure Ag). The gradient electrode design ensures conductivity while the pure gold surface layer improves oxidation resistance and reduces high-frequency signal loss.

[0066] 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 by, include: A base, wherein a base cavity covered by a cover plate is provided; The wafer has a gradient structure of silver-gold alloy electrodes formed on both its upper and lower surfaces, and one end of the wafer is bonded to the cavity of the base with conductive adhesive.

2. The quartz crystal of claim 1, wherein, A transition layer electrode is provided between the silver-gold alloy electrode and the wafer.

3. The quartz crystal of claim 1, wherein, The silver-gold alloy electrode has a gradient structure, including a substrate contact layer and a surface layer, with the substrate contact layer located between the surface layer and the wafer.

4. The quartz crystal according to claim 3, characterized in that, The thickness ratio of the substrate contact layer to the surface layer is 2:

1.

5. The quartz crystal according to claim 3, characterized in that, The surface layer is made of pure silver.

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