Crystal oscillator mixed seal welding method based on partition stripping

Abstract

The embodiment of the invention discloses a crystal oscillator mixed seal welding method based on partition stripping. The method comprises the steps that a base and a kovar alloy cover plate with a nickel-plated gold layer are prepared; performing laser cleaning on the lower surface of the kovar alloy cover plate corresponding to the short straight edge sealing area, removing the nickel-gold plating layer in the area, and meanwhile, retaining the nickel-gold plating layer in the long straight edge sealing area on the kovar alloy cover plate; the kovar alloy cover plate subjected to laser cleaning correspondingly covers the base, and a long straight edge sealing area of the kovar alloy cover plate is subjected to sealing welding through parallel seam welding; and the short straight edge sealing area of the kovar alloy cover plate is subjected to sealing welding through laser welding. According to the method, through partition surface treatment, the high-airtightness seal welding reliability is ensured, meanwhile, the advantages of high-efficiency continuity of electric resistance welding and gas control of laser welding are achieved, and the method is particularly suitable for packaging and manufacturing of small-sized and high-stability patch crystal oscillators such as 3215 and the like.

Description

Technical Field

[0001] This invention relates to the field of crystal oscillator manufacturing technology, and in particular to a hybrid sealing method for crystal oscillators based on partitioned stripping plating. Background Technology

[0002] The reliability of surface mount crystal oscillators (SMOs) is highly dependent on the quality of their hermetic packaging. Currently, the industry mainstream uses parallel seam welding to encapsulate Kovar alloy covers, a method that is highly efficient and produces continuous welds. However, with further miniaturization of crystal oscillator sizes (such as the 3215 specification) and increasingly stringent requirements for internal atmosphere control, traditional single resistance welding faces challenges in terms of heat-affected zone (HAZ) and gas generation control. Laser welding, as a precise, non-contact welding method, can effectively reduce HAZ and process gases. However, when applied to Kovar alloys with a nickel-gold plating layer (used to ensure resistance welding performance and corrosion protection), the gold element can easily cause hot cracks in the weld, severely degrading the sealing performance. If the plating layer is removed or thinned to be compatible with laser welding, the conductivity and reliability of the resistance weld will deteriorate. This contradiction has become a key bottleneck in promoting a high-reliability, high-efficiency hybrid sealing process. Summary of the Invention

[0003] The technical problem to be solved by the embodiments of the present invention is to provide a crystal oscillator hybrid sealing and soldering method based on partitioned stripping plating, so as to improve the reliability and efficiency of crystal oscillator packaging.

[0004] To address the aforementioned technical problems, this invention proposes a hybrid sealing and soldering method for crystal oscillators based on partitioned plating. The crystal oscillator includes a base and a Kovar alloy cover plate with a nickel-gold plating layer. The method includes: Prepare the base and the Kovar alloy cover plate with a nickel-gold plating layer; Laser cleaning is performed on the lower surface of the Kovar alloy cover plate to remove the nickel-gold plating layer in the short straight edge sealing area, while retaining the nickel-gold plating layer in the long straight edge sealing area of ​​the Kovar alloy cover plate. The Kovar alloy cover plate, after laser cleaning, is placed on the base, and the long straight edge sealing area of ​​the Kovar alloy cover plate is sealed by parallel seam welding. Laser welding was used to seal the short, straight edge sealing area of ​​the Kovar alloy cover plate.

[0005] Furthermore, the laser cleaning uses a pulsed laser with a wavelength of 355nm or 532nm, a pulse energy of 0.1 mJ - 2.0mJ, an energy density of 2 J / cm² - 15 J / cm², and a spot diameter of 20μm - 50μm.

[0006] Furthermore, the process parameters for the parallel seam welding are as follows: roller electrode pressure is 5 N - 8 N, welding current is 15 A - 25 A, welding speed is 3 mm / s - 8 mm / s, and working vacuum degree is less than or equal to 5.0 × 10⁻² Pa.

[0007] Furthermore, the surface of the roller electrode is coated with a tungsten-copper composite material layer with a thermal conductivity greater than or equal to 200 W / (m·K), and the temperature range of the weld nugget zone during welding is 1100℃-1200℃.

[0008] Furthermore, the parallel seam welding is performed in an atmospheric environment.

[0009] Furthermore, the laser welding uses a continuous or pulsed laser with a wavelength of 1064nm, a laser power of 80W-300W, a welding speed of 10 mm / s-30 mm / s, and a spot diameter of 50μm-200μm.

[0010] Furthermore, the laser welding is performed in a vacuum environment.

[0011] Furthermore, when using laser welding for sealing welding, a protective gas, namely argon, is blown into the weld pool area at a flow rate of 15 L / min - 25 L / min.

[0012] The beneficial effects of this invention are as follows: 1. This invention fundamentally solves the coating conflict: laser cleaning precisely and non-destructively removes local coatings, allowing laser welding to be performed on a clean alloy substrate, eliminating cracks; at the same time, it preserves the coating on the long side, ensuring the excellent conductivity and welding quality of parallel seam welding.

[0013] 2. This invention maximizes reliability: This invention combines the advantages of good consistency of long weld seams in parallel seam welding with the small heat-affected zone and less gas generation in laser welding, thus achieving the optimization of overall airtightness and internal atmosphere stability.

[0014] 3. The process of this invention is flexible and efficient: All steps of this invention are completed sequentially in a single vacuum environment, avoiding intermediate exposure and contamination, and are easy to automate, making them suitable for large-scale production.

[0015] 4. The invention has strong versatility: The invention is not only applicable to 3215-size crystal oscillators, but also provides innovative solutions for other microelectronic devices that require hybrid packaging technology. Attached Figure Description

[0016] Figure 1 This is a structural diagram of the Kovar alloy cover plate according to an embodiment of the present invention.

[0017] Figure 2This is an exploded view of the crystal oscillator from one angle according to an embodiment of the present invention.

[0018] Figure 3 This is an exploded view of the crystal oscillator from another angle according to an embodiment of the present invention.

[0019] Figure 4 This is a three-dimensional schematic diagram of the long straight edge of the roller sealing weld according to an embodiment of the present invention.

[0020] Figure 5 This is a top view schematic diagram of the long straight side of the roller sealing weld according to an embodiment of the present invention.

[0021] Figure 6 This is a three-dimensional structural diagram of a laser-welded short straight edge according to an embodiment of the present invention.

[0022] Figure 7 This is a top view schematic diagram of laser welding of a short straight edge according to an embodiment of the present invention.

[0023] Figure 8 This is a schematic diagram of a laser cleaning device according to an embodiment of the present invention.

[0024] Figure 9 yes Figure 8 Enlarged view of point D in the middle.

[0025] Figure 10 This is a schematic diagram of a welding device for parallel sealing of the long straight edge of a roller resistor according to an embodiment of the present invention.

[0026] Figure 11 This is a three-dimensional structural schematic diagram of a laser device for laser welding short straight edges according to an embodiment of the present invention.

[0027] Figure 12 This is a schematic diagram of the internal structure of a laser device for laser welding short straight edges according to an embodiment of the present invention.

[0028] Figure 13 This is a schematic flowchart of a crystal oscillator hybrid sealing method based on partitioned stripping according to an embodiment of the present invention.

[0029] Explanation of icon numbers 1. Kovar alloy cover plate; 2. Laser cleaning area; 3. Base; 4. Roller; 5. Long straight edge, sealing area; 6. Short straight edge, sealing area; 7. XY module; 8. Field lens; 9. Galvanometer; 10. Beam splitter and folding mirror; 11. Camera; 12. Laser head; 13. Cover plate carrier plate; 14. Y-axis module; 15. Cover plate carrier plate; 17. Motor; 18. X-axis module; 19. Module base plate; 20. Side support plate; 21. Vacuum chamber; 22. Vision component; 23. Laser component; 24. Light transmission window; 25. Unloading chamber; 26. Clamping fixture; 27. Unloading window; 28. XY axis module; 29. ​​Moving plate. Detailed Implementation

[0030] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0031] In this embodiment of the invention, directional indicators (such as up, down, left, right, front, back, etc.) are only used to explain the relative positional relationship and movement of each component in a specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0032] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features.

[0033] Please refer to Figures 1-3 The crystal oscillator includes a base and a Kovar alloy cover plate with a nickel-gold plating. Please refer to... Figure 13 The crystal oscillator hybrid sealing method based on partitioned stripping in this embodiment of the invention includes steps S1 to S4.

[0034] S1: Prepare the base and the Kovar alloy cover plate with a nickel-gold plating.

[0035] S2: For the sealing area corresponding to the short straight edge on the lower surface of the Kovar alloy cover plate (i.e., the sealing area between the short straight edges on both sides and the base, i.e., the laser-cleaned area) Figure 1 and Figure 3 Laser cleaning is performed on the Kovar alloy cover plate (as shown) to remove the nickel-gold plating layer in this area on the lower surface. Simultaneously, the nickel-gold plating layer on the long straight-edge sealing area of ​​the Kovar alloy cover plate (i.e., the area corresponding to the seal between the long straight edges on the front and rear sides and the base) is retained. The long straight-edge sealing area is shown below. Figure 4 and Figure 5 The high energy density of the laser causes the nickel-gold plating layer (especially the gold layer) to vaporize and peel off instantly, while the underlying Kovar alloy substrate, due to its high reflectivity and high damage threshold, is well preserved, forming a clean metal stripe with a width of about 0.2 mm.

[0036] A schematic diagram of the laser cleaning equipment is shown below. Figure 8 and Figure 9As shown, the laser cleaning equipment includes an XY module 7, a field mirror 8, a galvanometer 9, a beam splitter refracting mirror 10, a camera 11, a laser head 12, and a cover plate carrier 13. The XY module 7 drives the cover plate carrier 13, which is equipped with multiple Kovar alloy cover plates 1, to move in the XY direction. The laser pseudo-coaxial system composed of the field mirror 8, galvanometer 9, beam splitter refracting mirror 10, camera 11, and laser head 12 removes the coating from the short straight edge area of ​​the Kovar alloy cover plate 1.

[0037] S3: Place the laser-cleaned Kovar alloy cover plate onto the base, and seal the long straight edge sealing area of ​​the Kovar alloy cover plate using parallel seam welding. Please refer to... Figure 4 and Figure 5 After aligning the Kovar alloy cover plate with the base around its four edges, the long straight edges are first welded using rollers, followed by laser welding of the short straight edges. After the rollers make rolling contact with the Kovar alloy cover plate, the high-density resistance heat generated at the contact point between the electrode and the cover plate rapidly forms a molten nucleus, with the temperature controlled at approximately 1150℃ by infrared monitoring feedback. The molten metal solidifies after the electrode passes over it, forming a continuous and dense long-edge weld. The weld width on the long straight edge is approximately 0.2 mm.

[0038] Welding equipment for parallel resistance welding of the long straight edge of a roller, such as... Figure 10 As shown, the welding equipment includes a Y-axis module 14, a cover plate carrier 15, rollers 4, a motor 17, an X-axis module 18, a module base plate 19, and a side support plate 20. The Y-axis module 14 drives the cover plate carrier 15 to move in the Y direction, and the motor 17 drives the rollers 4 to move up and down. When the rollers 4 roll on the Kovar alloy cover plate 1, the Y-axis module 14 drives the cover plate carrier 15 to move to achieve welding of the long straight edge area. When welding the next Kovar alloy cover plate 1, the X-axis module composed of the X-axis module 18, the module base plate 19, and the side support plate 20 drives the rolling module composed of the motor 17 and the rollers 4 to move in the X direction to the position of the next Kovar alloy cover plate 1.

[0039] S4: Please refer to Figure 6 and Figure 7 The short, straight edge sealing area of ​​the Kovar alloy cover plate is sealed using laser welding, specifically by scanning the short, straight edge sealing area of ​​the Kovar alloy cover plate with a laser. The width of the laser-welded short, straight edge sealing area is approximately 0.2 mm. The laser equipment used for laser welding the short, straight edge in this invention is as follows: Figure 11 and Figure 12As shown, the laser device includes a vacuum chamber 21, a vision component 22, a laser component 23, a light-transmitting window 24, a feeding chamber 25, a clamping fixture 26, a discharge window 27, an XY axis module 28, and a moving plate 29. The vacuum chamber 21 contains the XY axis module 28, and the moving plate 29 is fixed to the XY axis module 28. The moving plate 29 drives the clamping fixture 26 to move in the XY direction. The vision component 22 captures and positions the four edges of the Kovar alloy cover plate 1. The laser component 23, composed of a galvanometer and a field lens, performs welding on the short straight edge area of ​​the Kovar alloy cover plate 1 in a vacuum. After welding, the clamping fixture 26 feeds the material out of the feeding chamber 25, which has a discharge window 27. The clamping fixture 28 flows out from the discharge window 27.

[0040] This invention employs laser cleaning technology to precisely remove the plating layer from the short, straight edge area to be laser-welded, while retaining the plating layer from the long, straight edge area to be resistance-welded. Subsequently, parallel seam welding is performed on the long, straight edge in an atmospheric environment, and laser welding is performed on the cleaned short, straight edge in a vacuum environment. This invention cleverly resolves the fundamental contradiction in surface plating requirements when using both resistance welding and laser welding processes on the same cover plate through partitioned surface treatment. It ensures high hermeticity and sealing reliability while combining the high efficiency and continuity of resistance welding with the gas control advantages of laser welding, making it particularly suitable for the packaging and manufacturing of miniaturized, high-stability surface-mount crystal oscillators such as the 3215.

[0041] In one embodiment, the laser cleaning uses a pulsed laser with a wavelength of 355nm or 532nm, a pulse energy of 0.1 mJ - 2.0mJ, an energy density of 2 J / cm² - 15 J / cm², and a spot diameter of 20μm - 50μm. The laser beam is controlled to scan along a short straight edge path by a galvanometer scanning system.

[0042] In one embodiment, the process parameters for the parallel seam welding are as follows: roller electrode pressure of 5 N-8 N, welding current of 15 A-25 A, welding speed of 3 mm / s-8 mm / s, and working vacuum degree of less than or equal to 5.0 × 10⁻² Pa. Preferably, the parallel seam welding is performed in an atmospheric environment.

[0043] In one embodiment, the surface of the roller electrode is coated with a tungsten-copper composite material layer with a thermal conductivity greater than or equal to 200 W / (m·K), and the temperature range of the weld nugget zone during welding is 1100℃-1200℃. During welding, the temperature of the weld nugget zone is maintained within this range by a closed-loop temperature control system.

[0044] In one implementation, the laser welding employs a continuous or pulsed laser (specifically, a YAG fiber laser in continuous or pulsed mode can be used), with a laser wavelength of 1064 nm, a laser power of 80 W-300 W, a welding speed of 10 mm / s-30 mm / s, and a spot diameter of 50 μm-200 μm. Preferably, the laser welding is performed in a vacuum environment. When performing sealed welding using laser welding, a protective gas, argon, is blown into the weld pool area at a flow rate of 15 L / min-25 L / min. Specifically, the protective gas can be blown into the weld pool area through a nozzle integrated on the welding torch.

[0045] Example 1:

[0046] After obtaining the Kovar alloy cover plate and the substrate, the Kovar alloy cover plate is subjected to laser cleaning (partial stripping). At the laser cleaning station, the vision system locates the short straight edge of the Kovar alloy cover plate.

[0047] A pulsed laser with a wavelength of 532nm was activated, with the pulse energy set to 0.8mJ and the spot diameter to 30μm. The beam was controlled by a galvanometer to scan the welding trajectory along the two short straight edges twice each.

[0048] The ceramic substrate with the chip mounted and encapsulated, and the Kovar alloy cover plate with a nickel layer of about 10 μm thickness and a gold layer of 0.2 μm thickness on the surface, are assembled and aligned in a clean environment.

[0049] The high energy density of the laser causes the coating (especially the gold layer) of the Kovar alloy cover plate to vaporize and peel off instantly, while the underlying Kovar alloy substrate is well preserved due to its high reflectivity and high damage threshold, forming a clean metal stripe with a width of about 0.2 mm.

[0050] Then perform parallel seam welding (long side sealing). The worktable is rotated to the resistance welding station. The roller electrode, coated with tungsten-copper composite material (thermal conductivity 220 W / (m·K)), is pressed against the long straight edge of the Kovar alloy cover plate under a pressure of 6.5 N.

[0051] Welding is initiated with a current of 20A and the electrode rotating at a speed of 5 mm / s. The high-density resistance heat generated at the contact point between the electrode and the Kovar alloy cover plate rapidly forms a weld nugget, with the temperature controlled at approximately 1150℃ by infrared monitoring feedback. The molten metal solidifies after the electrode passes over it, forming a continuous and dense long-side weld.

[0052] Clamping and vacuuming are performed. The assembly is placed in a dedicated fixture and secured to the worktable of the vacuum dual-station welding system. The vacuum chamber is closed, and the vacuum system is activated to reduce the chamber pressure to 3.0 × 10⁻⁻⁻⁶. 5 Below Pa.

[0053] Next, laser welding (short-side sealing) is performed. The worktable is rotated to the laser welding station. A 1064nm fiber laser outputs 150W continuous laser light, which is focused by a field lens with a focal length of 200mm, resulting in a spot diameter of 100μm.

[0054] Driven by a galvanometer, the laser beam scans along a cleaned short straight edge trajectory at a speed of 20 mm / s. Simultaneously, argon gas is blown onto the molten pool at a flow rate of 20 L / min for localized protection.

[0055] The laser energy is efficiently absorbed by the clean alloy surface, forming a high-quality weld with appropriate penetration depth. It smoothly overlaps with the long-side resistance weld at the corner, completing the overall gas-tight ring.

[0056] Cooling and Removal. After welding, allow the parts to cool in place on the worktable for a short time, then break the hole and remove the finished product.

[0057] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A mixed sealing method based on partitioning and stripping of a crystal oscillator, the crystal oscillator comprising a base and a Kovar alloy cover plate with a nickel-gold plated layer, characterized in that, The method comprises: Preparation of the base and Kovar alloy cover plate with a nickel-gold plating layer; Laser cleaning of the corresponding short straight edge sealing area on the lower surface of the Kovar alloy cover plate, removing the nickel-gold plating layer in this area, while retaining the nickel-gold plating layer on the long straight edge sealing area of the Kovar alloy cover plate; Covering the Kovar alloy cover plate after laser cleaning on the base, and using parallel seam welding to seal and weld the long straight edge sealing area of the Kovar alloy cover plate; Using laser welding to seal and weld the short straight edge sealing area of the Kovar alloy cover plate.

2. The zone-based strip-bonding method for crystal oscillator hybrid sealing according to claim 1, characterized in that, The laser cleaning uses pulsed laser with a wavelength of 355nm or 532nm, a pulse energy of 0.1 mJ-2.0mJ, an energy density of 2 J / cm²-15 J / cm², and a spot diameter of 20μm-50μm.

3. The zone-based strip-bonding method for crystal oscillator hybrid sealing according to claim 1, wherein, The process parameters of the parallel seam welding are: roller electrode pressure 5N-8N, welding current 15A-25A, welding speed 3mm / s-8mm / s, and working vacuum less than or equal to 5.0×10⁻²Pa.

4. The zone-based strip-bonding method for crystal oscillator hybrid sealing according to claim 3, characterized in that, The roller electrode surface is coated with a tungsten-copper composite material layer with a thermal conductivity greater than or equal to 200 W / (m·K), and the fusion zone temperature during welding ranges from 1100℃ to 1200℃.

5. The zone-based strip-bonding method for crystal oscillator hybrid sealing according to claim 1, wherein, The parallel seam welding is carried out in an atmospheric environment.

6. The zone-based strip-bonding method for crystal oscillator hybrid sealing according to claim 1, wherein, The laser welding uses continuous or pulsed laser with a wavelength of 1064nm, a laser power of 80W-300W, a welding speed of 10mm / s-30mm / s, and a spot diameter of 50μm-200μm.

7. The zone-based strip-bonding method for hybrid sealing of crystal oscillators as claimed in claim 6, wherein, The laser welding is carried out in a vacuum environment.

8. The zone-based strip-bonding method for hybrid sealing of a crystal oscillator as claimed in claim 6, wherein, When using laser welding for sealing and welding, protective gas is blown into the welding pool area, and the protective gas is argon with a flow rate of 15L / min-25L / min.

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