A crystal chip mounting method with four-corner elastic support and a hermetic packaging method thereof

Abstract

This invention discloses a crystal oscillator chip mounting structure with four-corner elastic supports and its hermetically sealed packaging method, belonging to the field of electronic component packaging technology. The mounting structure includes a ceramic substrate with a recessed groove in the center and metallized welding pillars at the four corners of the groove. Four metal elastic support legs are respectively installed at the corners, each support leg including a vertical welding part, a horizontal support arm, and an arc-shaped stress buffer part connecting the two. The upper surface of the horizontal support arm has a patterned insulating layer and a reserved electrode connection window. The quartz crystal is supported at its four corners on the horizontal support arm, with its main body suspended in the groove to form an air gap. The hermetically sealed packaging method includes quartz crystal mounting, parallel seam welding sealing, laser annealing stress release, and leak detection sealing steps. This invention effectively isolates thermal and mechanical stress through the elastic support structure and releases residual packaging stress through laser annealing, significantly improving the frequency stability, vibration resistance, and long-term reliability of the crystal oscillator.

Description

Technical Field

[0001] This invention relates to the field of electronic component packaging technology, specifically to a method for mounting a crystal oscillator chip with four-corner elastic supports and its hermetically sealed packaging method. Background Technology

[0002] Crystal oscillators (quartz crystal resonators / oscillators) are indispensable frequency control components in electronic devices, and their mounting and packaging processes directly determine the product's performance and reliability. With the rapid development of fields such as 5G communication, satellite navigation, and automotive electronics, higher requirements are being placed on the frequency stability, vibration resistance, and long-term reliability of crystal oscillators.

[0003] Currently, the mainstream methods for installing quartz crystals in the industry mainly adopt the following two approaches:

[0004] 1. Conductive Adhesive Bonding Method: The bottom of the quartz crystal is directly bonded to a ceramic substrate or metal base using conductive silver paste or insulating adhesive. This process is simple, low-cost, and suitable for mass production. However, this method has the following drawbacks: ① The adhesive layer is prone to aging and creep during high-temperature curing and long-term use, leading to micro-displacement of the crystal position and consequently frequency drift; ② The large contact area between the crystal bottom surface and the substrate easily generates significant parasitic capacitance, affecting high-frequency characteristics; ③ The adhesive layer cannot effectively buffer external mechanical shocks and thermal stress, limiting reliability.

[0005] 2. Flip-chip or eutectic bonding: This method directly connects the quartz crystal to the substrate electrodes using solder. It offers high connection strength and good conductivity, making it suitable for high-frequency applications. However, the significant difference in thermal expansion coefficients between the quartz crystal and the substrate material (ceramics, Kovar alloys, etc.) (quartz approximately 0.5 × 10⁻⁶) presents a challenge. -6 / ℃, ceramics approximately 6-8×10 -6 During temperature cycling or reflow soldering, significant thermomechanical stress is generated at the solder joints. This stress is directly transferred to the wafer surface, potentially leading to decreased frequency accuracy or even wafer cracking or breakage. The thermal stress problem is particularly pronounced in lead-free reflow soldering (peak temperature 260°C).

[0006] 3. Existing Suspended Mounting Schemes: To reduce parasitic capacitance and thermal stress, some existing technologies attempt to suspend the quartz crystal. For example, by setting support pillars or brackets on the substrate, an air gap is formed between the chip body and the bottom surface of the substrate. However, existing suspended mounting schemes still have the following technical bottlenecks:

[0007] Excessive rigidity of the support structure: Traditional rigid support columns cannot effectively buffer the stress generated by temperature changes and mechanical impacts, and the stress will still be transmitted to the crystal through the support points.

[0008] The elastic support structure is complex: the few solutions that use springs or spring sheets have complex structures, are difficult to assemble, and have high costs, making it difficult to achieve mass production.

[0009] It is difficult to balance hermetic sealing and elastic support: Existing hermetic sealing processes (such as parallel seam welding and energy storage welding) generate enormous mechanical impact pressure and instantaneous thermal shock during the sealing process. For elastic support structures, the sealing stress can cause deformation or even failure of the elastic components; if the sealing strength is reduced to protect the elastic components, the hermeticity cannot be guaranteed.

[0010] Stress cannot be released after encapsulation: Existing processes are all one-time encapsulation. After the sealing and soldering is completed, the residual stress accumulated inside the support structure cannot be eliminated. It will be slowly released during subsequent use, resulting in long-term frequency drift.

[0011] 4. Packaging Stress Issues: Parallel seam welding is currently the mainstream process for hermetic packaging of crystal oscillators. It involves applying pressure and pulsed current through electrode rollers, causing the metal at the sealing ring between the cover plate and the substrate to melt instantaneously, forming a weld. However, during this process, the mechanical pressure of several Newtons and the instantaneous thermal shock directly act on the installed quartz crystal and its supporting structure. For suspended crystal oscillators, these stresses can easily lead to deformation of the supporting structure, crystal displacement, and even microcracks in the wafer.

[0012] In summary, designing a quartz crystal mounting structure that can provide stable support, effectively buffer external stress, withstand thermal shock during the packaging process, and release residual stress after packaging has become an urgent need for technological development in this field. Traditional rigid support columns, complex spring structures, and one-time packaging processes cannot simultaneously meet the triple requirements of "high elastic stress isolation," "high hermeticity packaging," and "residual stress release." Summary of the Invention

[0013] This invention provides a method for mounting a crystal oscillator chip with four-corner elastic supports and its hermetically sealed mounting method, aiming to solve the problems of frequency drift and crystal breakage caused by thermal stress and packaging stress in the prior art, as well as the contradiction between elastic support and hermetically sealed mounting in traditional suspended mounting structures.

[0014] To achieve the above objectives, the present invention provides the following technical solution: a crystal oscillator chip mounting structure with four-corner elastic supports, comprising: a ceramic substrate, wherein a recessed groove is provided in the center of the ceramic substrate, and metallized welding pillars are provided at the four corners of the groove; four metal elastic support feet are respectively provided at the four corners of the groove, each elastic support foot comprising: a vertical welding part, fixedly connected to the metallized welding pillar; a horizontal support arm, located in the groove and higher than the bottom surface of the groove, for supporting a quartz crystal; an arc-shaped stress buffer part, connecting the vertical welding part and the horizontal support arm; a patterned insulating layer is provided on the upper surface of the horizontal support arm, the insulating layer covering the entire area of ​​the horizontal support arm except for at least one electrode connection window, where the electrode connection window exposes metal; a quartz crystal, whose four corners are respectively supported on the upper surfaces of the four horizontal support arms, and the electrodes of the quartz crystal are electrically connected to the horizontal support arms through the electrode connection window; the main body of the quartz crystal is suspended in the groove, forming an air gap with the bottom surface of the groove.

[0015] Preferably, the electrodes of the quartz crystal are fixed to the electrode connection window by conductive adhesive, achieving mechanical fixation and electrical connection.

[0016] Preferably, the electrode of the quartz crystal is metallurgically bonded to the electrode connection window through a eutectic solder layer.

[0017] Preferably, the metallized welding post is electrically connected to an external pad disposed on the bottom surface of the ceramic substrate through a metallized through-hole penetrating the ceramic substrate.

[0018] Preferably, a hermetically sealed mounting method for a crystal oscillator chip with four-corner elastic supports, based on the aforementioned mounting structure, includes the following steps:

[0019] S1: Quartz crystal installation: Fix the four corners of the quartz crystal to the upper surface of the four horizontal support arms, so that the quartz crystal is suspended in the groove.

[0020] S2: Parallel seam welded capping. In a protective atmosphere, a metal cap is placed on a ceramic substrate, and the metal cap and the ceramic substrate are sealed together by parallel seam welding to form a sealed cavity for containing a quartz crystal. The sealed cavity is filled with a protective gas.

[0021] S3: Laser annealing stress release. After parallel seam welding is completed, a pulsed laser is vertically incident from the bottom of the ceramic substrate. The laser passes through the ceramic substrate and irradiates four arc-shaped stress buffer parts, causing micro-area thermal expansion of the arc-shaped stress buffer parts and releasing the residual stress generated by the parallel seam welding process.

[0022] S4: Leak detection and final sealing. The package is leak-tested by helium mass spectrometry. If it passes the test, the tiny gaps at the seal are repaired by laser welding to complete the final hermetically sealed packaging.

[0023] Preferably, in the laser annealing step, the laser wavelength is in the near-infrared band, the pulse width is 1ms-10ms, and the power density is controlled within the range that causes the arc-shaped stress buffer part to thermally expand but does not exceed the recrystallization temperature of its material.

[0024] Preferably, the protective atmosphere is nitrogen or an inert gas.

[0025] Preferably, a crystal oscillator package has the above mounting structure and is manufactured using the hermetically sealed packaging method described above.

[0026] The beneficial effects of this invention are as follows:

[0027] 1. Strong stress isolation and buffering capabilities: By setting up an arc-shaped stress buffer section, the elastic support foot can effectively absorb the stress in the Z-axis direction caused by temperature changes, mechanical impacts or packaging processes, avoiding the direct transmission of stress to the quartz crystal, and significantly reducing the risk of frequency drift and wafer breakage.

[0028] 2. Suspended structure reduces parasitic effects: The quartz crystal body is suspended in the groove, forming an air gap with the bottom surface of the substrate, which effectively reduces parasitic capacitance and improves high-frequency characteristics, making it suitable for high-frequency crystal oscillator packaging.

[0029] 3. Good compatibility with packaging processes: The parallel seam welding sealing process ensures the airtightness requirements; combined with the laser annealing step, residual stress is released without damaging the packaging structure, solving the problem that packaging stress cannot be eliminated in traditional processes.

[0030] 4. Reliable electrical connection and compact structure: The graphic insulating layer and electrode connection window design on the horizontal support arm ensures reliable electrical connection and avoids short circuit risk; the metallized solder pillars and through-hole structure enable signal output, and the overall structure is compact and suitable for SMD packaging.

[0031] 5. Wide process window and strong adaptability: The laser annealing parameters can be flexibly adjusted according to the substrate material and the support foot material, and it is suitable for a variety of ceramic substrates such as aluminum nitride and alumina, with good process repeatability and industrialization prospects.

[0032] 6. Enhanced long-term stability and reliability: Through the active release of residual stress and stress isolation of the elastic structure, the crystal oscillator can maintain frequency stability even after long-term use, temperature cycling and mechanical vibration, meeting the high reliability requirements of military, aerospace, automotive electronics and other applications. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention 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 only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram of the overall installation structure of the present invention;

[0035] Figure 2 This is a process flow diagram of the hermetically sealed packaging method of the present invention.

[0036] In the figure: 1. Ceramic substrate; 2. Groove; 3. Metallized welding pillar; 4. External pad; 5. Vertical welding part; 6. Horizontal support arm; 7. Arc-shaped stress buffer part; 8. Patterned insulating layer; 9. Electrode connection window; 10. Quartz crystal; 11. Metal cover plate; 12. Metallized via. Detailed Implementation

[0037] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] Example 1

[0039] like Figure 1 , Figure 2 As shown, this embodiment provides a mounting structure and hermetically sealed packaging process for high-frequency crystal oscillators, applicable to consumer electronics and industrial-grade crystal oscillator products.

[0040] 1. Preparation of ceramic substrate 1: Aluminum nitride ceramic substrate 1 is selected, with overall dimensions of 5.0mm × 3.2mm × 0.8mm. A recessed groove 2 is formed in the center of the substrate by laser processing or mold pressing, with dimensions of 4.0mm × 2.2mm × 0.3mm.

[0041] Metallized welding pillars 3 are pre-embedded at the four corners of the groove 2 using a high-temperature co-fired ceramic process. Each metallized welding pillar 3 measures 0.8mm × 0.8mm × 0.3mm, with its top flush with the bottom surface of the groove 2. It is made of tungsten metal and plated with nickel-gold to facilitate welding. The four metallized welding pillars 3 correspond to the two electrodes of the quartz crystal 10.

[0042] Metallized vias 12 are pre-fabricated inside the ceramic substrate 1, and four metallized solder pillars 3 are electrically connected to the external pads 4 on the bottom surface of the metallized solder pillars 3 respectively. The external pads 4 are 1.0mm × 0.6mm in size, and are laid out according to the standard SMD package 4 pad layout. The surface of the pads is gold-plated with a thickness of 0.5μm.

[0043] 2. The elastic support foot is made of Invar alloy (Fe-Ni alloy) with a thickness of 0.1 mm and a coefficient of thermal expansion of 1.2 × 10⁻⁶. -6 At / ℃, a plate matching the ceramic substrate 1 is formed into four independent metal elastic support feet in a single process using a precision chemical etching technique. The structural design of each support foot is as follows:

[0044] Vertical welding part 5: height 0.3mm, width 0.6mm, used for laser welding with metallized welding column 3;

[0045] Horizontal support arm 6: 1.0 mm in length and 0.6 mm in width, with its upper surface used to support the quartz crystal 10;

[0046] Arc-shaped stress buffer 7: Connecting the vertical welded part 5 and the horizontal support arm 6, it can adopt an S-shaped structure. This arc-shaped structure can undergo elastic deformation under stress, absorbing mechanical and thermal stress in the Z-axis direction.

[0047] A patterned insulating layer 8 of silicon dioxide, with a thickness of 0.5 μm, is formed on the upper surface of the horizontal support arm 6 using plasma-enhanced chemical vapor deposition. Electrode connection windows 9, each 0.2 mm × 0.2 mm in size, are then formed on the insulating layer using photolithography and wet etching processes, corresponding to the electrodes of the quartz crystal 10. The metal support arm body is exposed at the windows for subsequent electrical connections.

[0048] 3. Installation of Support Feet: Place the four elastic support feet at the four corners of the groove 2, ensuring the vertical welded part 5 is tightly against the metallized welded column 3. Use a fiber laser to spot weld the connection between the vertical welded part 5 and the metallized welded column 3. The process parameters are: laser power: 25W, pulse width: 3ms, spot diameter: 0.3mm, welding method: single-point pulse welding, with two spots welded on each column. During welding, the laser only acts on the local area of ​​the weld point, the heat-affected zone diameter is less than 0.5mm, and heat is not conducted to the arc-shaped stress buffer part 7, ensuring the elastic performance of the support feet is not affected. Post-weld inspection shows the weld is firm, with no incomplete welds or spatter.

[0049] 4. During the installation of the quartz crystal 10, a quartz crystal 10 with dimensions of 2.5mm × 1.8mm × 0.15mm was selected. Its two coated electrodes were located diagonally on the lower surface of the crystal. The electrodes were made of gold and had a thickness of 0.3μm. At the electrode connection windows 9 of the four horizontal support arms 6, epoxy conductive silver paste was applied using a precision dispensing machine at a dispensing amount of 0.01mg and a dispensing diameter of approximately 0.15mm. The quartz crystal 10 was then placed on the upper surface of the four horizontal support arms 6 with its four corners aligned, ensuring the electrodes of the quartz crystal 10 were directly facing the electrode connection windows 9. A pressure of 0.05N was applied using a pick-and-place machine to ensure full contact between the quartz crystal 10 and the conductive paste. The substrate with the quartz crystal 10 installed was placed in a hot air oven and cured at 150℃ for 90 minutes to allow the conductive paste to fully cure. After curing, the shear strength of the conductive paste was ≥15MPa, and the volume resistivity was ≤1×10⁻⁶. -4 Ω·cm. After installation, the main body of the quartz crystal 10 is suspended in the groove 2, and the air gap height between the lower surface of the quartz crystal 10 and the bottom surface of the groove 2 is 0.1mm ± 0.02mm. Microscopic examination shows that the four corners of the quartz crystal 10 are flat and fit snugly against the upper surface of the support arm, without tilting or shifting.

[0050] 5. Parallel seam welding sealing: The ceramic substrate 1 with the quartz crystal 10 installed is placed in a glove box filled with high-purity nitrogen, with the oxygen content controlled below 50 ppm and the water vapor content controlled below 100 ppm. A Kovar alloy metal cover plate 11 is placed on the ceramic substrate 1. The metal cover plate 11 has dimensions of 5.0 mm × 3.2 mm × 0.2 mm and is nickel-plated. Parallel seam welding is used for sealing, with the following process parameters: welding current: 80 A, welding speed: 12 mm / s, electrode pressure: 2.5 N, electrode spacing: 2.0 mm, and number of welding passes: double seam welding, i.e., two passes on each side. During the sealing process, the electrode roller rolls along the edge of the metal cover plate 11, and the pulsed current causes the metal at the sealing ring between the metal cover plate 11 and the ceramic substrate 1 to melt instantaneously, forming a continuous weld. The entire sealing process lasts approximately 3 seconds. After sealing, the metal cover plate 11 and the ceramic substrate 1 form an airtight sealed cavity filled with a nitrogen protective atmosphere. Preliminary visual inspection revealed that the welds were continuous and uniform, without cracks or porosity.

[0051] 6. Laser annealing stress relief: Immediately after sealing, the package is placed on a laser annealing fixture. A semiconductor pulsed laser is used, with the laser beam incident vertically upwards from the bottom of the ceramic substrate 1. Laser parameters are selected based on the following: the material of the arc-shaped stress buffer 7 is Invar alloy, whose recrystallization temperature is approximately 450℃. The target temperature for laser heating is 300℃-350℃, achieving stress relief without altering the material's microstructure. The process parameters are: laser wavelength: 1064nm, pulse width: 5ms, single pulse energy: 0.4J, spot diameter: 0.8mm, energy density: 0.8 J / cm². 2Irradiation method: Each arc-shaped stress buffer 7 is irradiated with 3 pulses, with a pulse interval of 0.5s. Since aluminum nitride ceramic has a certain transmittance to 1064nm laser (approximately 20%-30%), after the laser energy passes through the 0.8mm thick ceramic substrate 1, the remaining energy is absorbed by the metal arc-shaped stress buffer 7, causing it to instantly heat up to approximately 320℃, resulting in micro-area thermal expansion. This thermal expansion process releases the residual stress accumulated inside the elastic support leg during parallel seam welding. During laser irradiation, the surface temperature of the arc-shaped stress buffer 7 is monitored in real time using an infrared thermometer to ensure that the temperature does not exceed 350℃. After irradiation, the arc-shaped stress buffer 7 cools and returns to its original state, but the internal residual stress has been significantly reduced.

[0052] 7. Leak detection and final sealing: Helium mass spectrometry leak detection of the package: Place the package in a vacuum chamber and evacuate to 1×10⁻⁶. -3 Helium gas was blown around the package at a pressure of 0.3 MPa, and the leak rate was measured. For packages that passed the leak test, a laser welding machine was used to repair the tiny gaps at the seal. Welding parameters: laser power: 15W, scanning speed: 5mm / s, spot diameter: 0.2mm, number of welding passes: single-pass welding. After welding, a second leak test was performed; the leak rate of all samples was ≤1×10⁻⁶. -9 Pa·m 3 / s, which meets the airtightness requirements in the testing methods for microelectronic devices.

[0053] 8. Performance testing: Performance tests were conducted on 100 crystal oscillators packaged using the method described in this embodiment, and the results were compared with those of crystal oscillators packaged using traditional conductive adhesive bonding. The test results are as follows:

[0054]

[0055] Test results show that the technical solution provided by this invention significantly improves the frequency stability, long-term reliability and electrical performance of crystal oscillators.

[0056] Example 2:

[0057] This embodiment is basically the same as Embodiment 1, except that the quartz crystal 10 is fixed by eutectic bonding instead of conductive adhesive bonding, which is suitable for military and aerospace grade crystal oscillator products with higher reliability requirements.

[0058] The eutectic solder layer is prepared by pre-plating a gold-tin alloy solder layer at the electrode connection window 9 of the horizontal support arm 6 using an electroplating process. The process steps are as follows:

[0059] First, electroplat a gold layer with a thickness of 2μm on the exposed metal window.

[0060] A tin layer is then electroplated, with a thickness of 3μm;

[0061] Heating to 300°C in a protective atmosphere allows gold and tin to interdiffusion to form an Au80Sn20 eutectic alloy.

[0062] The final solder layer thickness is approximately 5μm, and the surface is smooth;

[0063] Eutectic bonding is performed by aligning the four corners of the quartz crystal 10 on the four horizontal support arms 6, ensuring that the electrodes of the quartz crystal 10 are facing the solder layer. Bonding is then carried out in a vacuum eutectic furnace.

[0064] Furnace cavity vacuum degree: ≤5×10 -3 Pa;

[0065] Heating rate: 50℃ / min;

[0066] Bonding temperature: 310℃, higher than the Au80Sn20 eutectic point of 280℃;

[0067] Heat retention time: 30 seconds;

[0068] Cooling rate: 30℃ / min;

[0069] Bonding pressure: The weight of the quartz crystal itself, without additional pressure;

[0070] During eutectic bonding, the solder layer melts and forms a stable intermetallic compound with the gold layer of the quartz crystal-coated electrode, achieving metallurgical bonding. After bonding, the shear strength of the weld interface is ≥40MPa, far exceeding that of conductive adhesive.

[0071] The remaining steps—support foot installation, parallel seam welding for sealing, laser annealing for stress relief, leak detection, and final sealing—are the same as in Example 1.

[0072] The crystal oscillator packaged in Example 2 was tested and compared with that in Example 1:

[0073]

[0074] Example 2 is suitable for scenarios with extremely high requirements for reliability and high-frequency performance, such as satellite communication, missile guidance and other military and aerospace fields; Example 1 is suitable for consumer electronics and industrial control fields, and has a higher cost performance.

[0075] Example 3:

[0076] This embodiment optimizes the material of ceramic substrate 1 by using alumina ceramic instead of aluminum nitride ceramic, making it suitable for cost-sensitive applications. The material change is as follows:

[0077] Ceramic substrate 1: 95% alumina ceramic, 0.8 mm thick;

[0078] Flexible support feet: Kovar alloy, i.e., Fe-Ni-Co alloy, 0.1mm thick;

[0079] Metal cover plate 11: Kovar alloy, with a coefficient of thermal expansion matched to that of the substrate;

[0080] 2. During laser annealing parameter adjustment, the transmittance of alumina ceramic to 1064nm laser is lower than that of aluminum nitride. Therefore, it is necessary to adjust the laser parameters to ensure sufficient energy reaches the arc-shaped buffer section.

[0081] Laser wavelength: 1064nm;

[0082] Pulse width: 8ms;

[0083] Single pulse energy: 0.8J;

[0084] Spot diameter: 1.0 mm;

[0085] Energy density: 1.0 J / cm³ 2 ;

[0086] Number of irradiations: 5 pulses per buffer zone;

[0087] After adjustment, the laser energy transmitted through the ceramic substrate 1 is still sufficient to heat the arc-shaped buffer section to over 300°C, thereby achieving stress release.

[0088] Tests show that Example 3, which uses alumina ceramics, has performance indicators that are basically the same as those of Example 1, but the material cost is reduced by about 30%, making it suitable for mass consumer electronics applications.

[0089] To determine a reasonable range for the laser annealing parameters in the claims, this invention conducted a series of process window verification experiments:

[0090]

[0091] Experimental results show that the "pulse width of 1ms-10ms" specified in the claims is a completely feasible process window that can ensure stress release effect without damaging the material.

[0092] The three embodiments above illustrate the implementation of the present invention in different application scenarios: Embodiment 1: Conductive adhesive bonding solution, suitable for consumer electronics and industrial products, with high cost performance; Embodiment 2: Eutectic bonding solution, suitable for high-end fields such as military and aerospace, with extreme reliability; Embodiment 3: Alumina ceramic solution, suitable for cost-sensitive mass production applications. All three embodiments demonstrate that the technical solution of the present invention has: good process repeatability, a wide process window, significant performance improvement, and clear industrialization value.

[0093] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A crystal oscillator chip mounting structure with four-corner elastic supports, characterized in that, include: A ceramic substrate (1) is provided with a recessed groove (2) in the center of the ceramic substrate (1), and metallized welding pillars (3) are provided at the four corners of the groove (2). Four metal elastic support feet are respectively set at the four corners of the groove (2). Each elastic support foot includes: a vertical welding part (5) fixedly connected to the metallized welding column (3); a horizontal support arm (6) located in the groove (2) and higher than the bottom surface of the groove (2) for supporting the quartz crystal (10); an arc-shaped stress buffer part (7) connecting the vertical welding part (5) and the horizontal support arm (6); the upper surface of the horizontal support arm (6) is provided with a patterned insulating layer (8), the insulating layer covers the entire area of ​​the horizontal support arm (6) except for at least one electrode connection window (9), where the electrode connection window (9) exposes metal; Quartz crystal (10), with its four corners supported on the upper surfaces of the four horizontal support arms (6), and the electrodes of the quartz crystal (10) electrically connected to the horizontal support arms (6) through the electrode connection window (9); The main body of the quartz crystal (10) is suspended in the groove (2), forming an air gap between it and the bottom surface of the groove (2).

2. The crystal oscillator chip mounting structure according to claim 1, characterized in that, The electrodes of the quartz crystal (10) are fixed to the electrode connection window (9) by conductive adhesive, thereby achieving mechanical fixation and electrical connection.

3. The crystal oscillator chip mounting structure according to claim 1, characterized in that, The electrodes of the quartz crystal (10) are metallurgically bonded to the electrode connection window (9) through a eutectic solder layer.

4. The crystal oscillator chip mounting structure according to claim 1, characterized in that, The metallized welding column (3) is electrically connected to the external pad (4) disposed on the bottom surface of the ceramic substrate (1) through a metallized through hole penetrating the ceramic substrate (1).

5. A hermetically sealed mounting method for a crystal oscillator chip with four-corner elastic supports, based on the mounting structure described in any one of claims 1 to 4, characterized in that, Includes the following steps: S1: Quartz crystal installation: Fix the four corners of the quartz crystal (10) to the upper surface of the four horizontal support arms (6) so that the quartz crystal is suspended in the groove (2); S2: Parallel seam welded capping, in a protective atmosphere, a metal cap (11) is placed on a ceramic substrate (1), and the metal cap (11) and the ceramic substrate (1) are sealed together by parallel seam weld to form a sealed cavity for containing a quartz crystal (10), and the sealed cavity is filled with a protective gas. S3: Laser annealing stress release. After parallel seam welding is completed, a pulsed laser is vertically incident from the bottom of the ceramic substrate (1). The laser passes through the ceramic substrate (1) and irradiates four arc-shaped stress buffer parts (7), causing the arc-shaped stress buffer parts (7) to undergo micro-area thermal expansion, releasing the residual stress generated by the parallel seam welding process. S4: Leak detection and final sealing. The package is leak-tested by helium mass spectrometry. If it passes the test, the tiny gaps at the seal are repaired by laser welding to complete the final hermetically sealed packaging.

6. The hermetically sealed packaging method according to claim 5, characterized in that, In the laser annealing step, the laser wavelength is in the near-infrared band, the pulse width is 1ms-10ms, and the power density is controlled within the range that causes the arc-shaped stress buffer part (7) to thermally expand but does not exceed the recrystallization temperature of its material.

7. The hermetically sealed packaging method according to claim 5, characterized in that, The protective atmosphere is nitrogen or an inert gas.

8. A crystal oscillator package, characterized in that, It is manufactured using the mounting structure described in any one of claims 1 to 4 and the hermetically sealed mounting method described in any one of claims 5 to 7.

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