A Lithographic High-Fundamental-Frequency Wafer with a Concave Cavity Structure and a Preparation Method for a Quartz Crystal Resonator

Abstract

The present invention relates to the field of quartz crystal resonators, and specifically discloses a lithographed high fundamental frequency wafer with a concave cavity structure and a preparation method of a quartz crystal resonator. The material of the lithographed high fundamental frequency wafer with a concave cavity structure is quartz, and its thickness is 8 μm - 30 μm. The lithographed high fundamental frequency wafer with a concave cavity structure is rectangularly arranged; in the present invention, a shielding device is designed in the weak magnetic field area during ion sputtering coating of the Wafer, so that the gold ions sputtered in this area are adsorbed on the shielding device and will not be sputtered onto the Wafer. Thus, during the movement of the Wafer, it is always in the strong magnetic field area and directly receives the gold ions in the sputtering area. The initial frequency deviation of the quartz crystal frequency wafer can be controlled within -9000 ppm to -3000 ppm, and the full range can be controlled within 6000 ppm. After the quartz wafer is etched, not only the surface flatness and frequency are greatly improved, but also the resonance resistance is reduced.

Description

Technical Field

[0001] The present invention relates to the field of quartz crystal resonators, and in particular to a lithographed high fundamental frequency wafer with a concave cavity structure and a method for preparing a quartz crystal resonator therefrom. Background Art

[0002] At present, the highest frequency that can be achieved for quartz crystal resonators produced by the grinding process in the market is 60 MHz fund (fundamental frequency), while the quartz crystal resonators produced on a large scale are at the 40 MHz fund (fundamental frequency) level. With the increasing requirements for communication bandwidth, people have to use higher frequencies to meet the bandwidth requirements. Therefore, there is a need for quartz crystal resonators with a resonant frequency reaching gigahertz, which will bring more bandwidth to future communication devices. With the development of 5G / 6G communication technologies, the market has higher and higher requirements for the operating frequency and signal output rate of quartz crystal resonators. The demand for high fundamental frequency quartz wafers has shown a blowout growth. Developing quartz crystal resonators with higher operating frequencies is the goal pursued by scientists in the electronics field, because the higher the frequency, the faster the communication speed.

[0003] The core key component of a quartz crystal resonator is a quartz crystal frequency wafer (referred to as a quartz wafer for short). The frequency of the quartz wafer is inversely proportional to its thickness, that is, the higher the frequency, the thinner the quartz crystal frequency wafer. Ultra-thin wafers are prone to being damaged by force during the later processing and use, resulting in a reduced qualification rate.

[0004] In order to improve the mechanical properties of high fundamental frequency quartz crystal resonators, usually, a relatively thick quartz wafer is cut, ground repeatedly, etched, etc. to produce a high fundamental frequency quartz crystal frequency wafer. This process can only achieve a maximum frequency of 60 MHz, far from meeting the market demand for higher frequencies. Moreover, after the quartz wafer is etched, it has the disadvantages of low surface flatness, large resonant resistance, and excessive parasitics.

[0005] Therefore, we propose a lithographed high fundamental frequency wafer with a concave cavity structure and a method for preparing a quartz crystal resonator therefrom to solve the above problems. Summary of the Invention

[0006] The purpose of the present invention is to provide a lithographed high fundamental frequency wafer with a concave cavity structure and a method for preparing a quartz crystal resonator therefrom to solve the problems raised in the above background art.

[0007] To achieve the above purpose, the present invention provides the following technical solutions:

[0008] A lithographed high fundamental frequency wafer with a concave cavity structure, the lithographed high fundamental frequency wafer with a concave cavity structure is made of quartz, and its thickness is 8 μm - 30 μm. The lithographed high fundamental frequency wafer with a concave cavity structure is rectangularly arranged.

[0009] The present invention also provides a quartz crystal resonator, which includes the concave cavity structure lithographed high fundamental frequency wafer, as well as a base, a mounting platform, a kovar ring and an upper cover. The kovar ring is fixedly connected to the top edge of the base. The mounting platform is fixedly connected to the inner side of the kovar ring. The concave cavity structure lithographed high fundamental frequency wafer is fixedly installed on the upper surface of the mounting platform. The upper cover is fixedly connected to the top of the kovar ring.

[0010] In a further embodiment, a concave cavity structure is provided in the middle of the upper surface of the concave cavity structure lithographed high fundamental frequency wafer. An electrode is provided in the middle of the concave cavity structure. Upper electrode leads and lower electrode leads are respectively provided on both sides of the electrode. An upper auxiliary electrode and a lower auxiliary electrode are provided at one end of the concave cavity structure lithographed high fundamental frequency wafer;

[0011] The upper auxiliary electrode, the lower auxiliary electrode, the upper electrode leads and the lower electrode leads all have a metal covering film with a thickness of 6 - 3 nm. The material of the metal covering film is gold and chromium;

[0012] The upper cover has a thickness of 0.06 - 0.08 mm. The composition of the upper cover includes the following components by mass percentage: 15 - 18% of cobalt, 26 - 30% of nickel, and 59 - 52% of iron;

[0013] The base has a thickness of 0.4 - 0.7 mm. The material of the base is 50 - 53% ceramic. The kovar ring accounts for 19 - 25% of the total mass. The composition of the kovar ring includes the following components by mass percentage: 4 - 6% of cobalt, 4 - 6% of nickel, and 11 - 13% of iron. The metal covering film accounts for 22 - 31% of the total mass.

[0014] In addition, the present invention also provides a preparation method for the quartz crystal resonator, including the following steps:

[0015] Step 1, grinding and polishing: The cut Wafer wafer is ground and polished to control its thickness within a certain range;

[0016] Step 2, Wafer coating: The ground and polished Wafer wafer in Step 1 is coated with a metal layer through ion sputtering technology to give an initial frequency to the quartz crystal frequency wafer on the Wafer wafer;

[0017] Step 3, making the concave cavity electrode;

[0018] Step 4, scribing and dispensing;

[0019] Step 5, fine frequency adjustment;

[0020] Step 6, sealing and soldering;

[0021] Step 7, aging test.

[0022] In a further embodiment, the polishing and grinding in the first step includes the following steps:

[0023] A1. Cut the ingot into 3-inch Wafer wafers with a cutting angle of 35°8′ - 35°29′ and a thickness controlled within 0.1 - 0.12 mm;

[0024] A2. Place the wafers cut in A1 into the grinding machine fixture for fixation;

[0025] A3. Put the standard block into the thickness gauge and complete the calibration;

[0026] A4. Input the target thickness into the test system;

[0027] A5. Pump the prepared grinding fluid into the grinding machine for grinding. The grinding fluid includes the following components by mass percentage: 20% - 30% deionized water, diamond particle abrasive with a diameter of 3 - 5 μm, accounting for 30% - 40%, thickener 8% - 15%, lubricant 5% - 8%, organic solvent 15% - 30%, dispersant 1% - 7%. During grinding, a pressure sensor is designed on the grinding equipment to quickly capture the force value during grinding, feedback it to the power mechanism, and transmit the force value to the monitoring equipment to achieve real-time control. The system software automatically calculates the grinding time to reduce the wafer thickness to 8 μm - 30 μm, and then performs polishing treatment;

[0028] A6. Slice;

[0029] A7. Detect the grinding size and flatness.

[0030] In a further embodiment, the ion sputtering in the second step includes the following steps:

[0031] I. Load the Wafer wafers polished and ground in the first step into the designed fixture and make positioning;

[0032] II. Feed the wafer positioned in Step I into the baking area of the coating equipment. After baking, feed it into the coating area. Before coating starts, input the sputtering target frequency, start pumping vacuum until it reaches 6.7×10-3 pa, and then perform ion sputtering coating. The coating materials are chromium target and gold target. The specific operation is that on both sides of the first cavity in the coating area, there is a chromium target respectively, and on both sides of the second cavity, there is a gold target respectively. Before coating starts, input the sputtering target frequency, start pumping vacuum. After the vacuum meets the requirements, start ion sputtering coating. After the chromium targets on both sides of the first cavity are powered on, usually, argon gas is discharged to generate gas ionization. Its positive ions are bombarded at a high speed on the cathode target under the action of the electromagnetic field, knocking out the atoms or molecules of the cathode target and flying towards the surface of the wafer to be coated to deposit a chromium film layer. After completion, the wafer is then fed into the second cavity, and in the same way, gold ions are sputtered and covered on the surface of the wafer to form a gold film layer. That is, after coating, the first layer on the surface of the wafer is covered with a chromium film, and the second layer is covered with a gold film, so that the wafer forms an initial frequency.

[0033] In a further embodiment, the production of the concave cavity electrode in Step III includes the following steps:

[0034] S1. Photoresist preparation: Place the polished wafer on the spin coater platform, inject the photoresist into a special syringe, and then inject it onto the surface of the wafer through the syringe. As the spin coater platform runs, the photoresist is evenly distributed on the surface of the wafer. The rotation speed of the spin coater platform is set at 2000 r / min, and the photoresist coating amount is 0.6 ml.

[0035] S2. Baking: Put the wafer with the photoresist coated in Step S1 into the baking equipment for baking. The baking temperature is 75 - 85 °C, and the duration is 80 - 100 s.

[0036] S3. Expose and develop the wafer coated with photoresist.

[0037] S4. Wet etching: Use hydrofluoric acid (HF) as the wet etching solution and add ammonium fluoride as a buffer. The ratio of hydrofluoric acid to ammonium fluoride is 60%:40%. The etching rate is 100 nm / min, and finally, a concave cavity is formed. The thickness of the concave cavity part is 3 - 20 μm. The reaction products are separated from the surface of the material to be etched and are pumped out of the cavity by the vacuum system.

[0038] S5. Remove the photoresist: Soak and remove the photoresist with acetone.

[0039] In a further embodiment, the die bonding in step four includes the following steps: The Wafer wafer after the cavity electrode is fabricated is loaded into a carrier fixture. Through a die splitting device, the Wafer wafer is split into single-piece quartz crystal frequency chips. Then, through a die bonding device, using conductive adhesive, the single-piece quartz crystal frequency chips are fixed in the base cavity, so that the quartz crystal frequency chips form a circuit with the carrier base, and are placed in a tunnel furnace with a maximum temperature of 300 °C for baking to cure the conductive adhesive.

[0040] In a further embodiment, the frequency fine-tuning in step five includes the following steps: The product after baking and curing in step four of die bonding is placed in a frequency fine-tuning fixture. Through ion etching technology, the gold layer on the surface of the quartz crystal frequency chip is bombarded and etched. This etching process is completed in a vacuum environment of 6.5×10-3 Pa, and the frequency accuracy reaches ±2 ppm.

[0041] In a further embodiment, the sealing and soldering in step six includes the following steps: The semi-finished product after frequency fine-tuning in step five is transferred to a special fixture for sealing and soldering, and the fixture containing the product is placed in a vacuum oven for baking. After baking, through an electrode wheel, roll soldering and discharging are performed on the four sides of the product to weld and seal the upper cover and the semi-finished product after frequency fine-tuning.

[0042] Compared with the prior art, the beneficial effects of the present invention are:

[0043] In the present invention, by setting a base, a mounting platform, a kovar ring, and an upper cover, the quartz chip is installed on the mounting platform and placed in a vacuum oven for baking through a special fixture for sealing and soldering. Then, through an electrode wheel, roll soldering and discharging are performed on the four sides of the product to weld and seal the upper cover and the semi-finished product after frequency fine-tuning, thereby ensuring that the quartz wafer is protected during use and avoiding its damage due to stress.

[0044] In the present invention, by designing a shielding device in the weak magnetic field area during the ion sputtering coating of the Wafer wafer, the gold ions sputtered in this area are adsorbed on the shielding device and will not be sputtered onto the Wafer wafer. Thus, during the movement of the Wafer wafer, it is always in the strong magnetic field area and directly receives the gold ions in the sputtering area. The initial frequency deviation of the quartz crystal frequency chip can be controlled within -9000 ppm to -3000 ppm, and the full range can be controlled within 6000 ppm. After the quartz wafer is etched, not only the surface flatness and frequency are greatly improved, but also the resonant resistance is reduced. Description of the Drawings

[0045] Figure 1 It is an exploded structural schematic diagram of the quartz crystal resonator of the present invention;

[0046] Figure 2 It is a schematic diagram of the shielding device designed in the weak magnetic field area of the present invention;

[0047] Figure 3 Schematic diagram of data before high-temperature aging for the 96Mhz gold-plated photolithography high fundamental frequency product of the present invention;

[0048] Figure 4 Schematic diagram of test data for the 96Mhz gold-plated photolithography high fundamental frequency product of the present invention after aging at 125°C ± 5°C for 1000 hours;

[0049] Figure 5 Schematic diagram of comparison data for the 96Mhz gold-plated photolithography high fundamental frequency product of the present invention after aging at 125°C ± 5°C for 1000 hours with the frequency change controlled within ±3ppm;

[0050] Figure 6 Schematic diagram of the first set of test data on the frequency deviation range after sputtering coating before adding the shielding device to the present invention;

[0051] Figure 7 Schematic diagram of the second set of test data on the frequency deviation range after sputtering coating before adding the shielding device to the present invention;

[0052] Figure 8 Schematic diagram of the initial frequency test results after 96Mhz photolithography high fundamental frequency coating without adding the shielding device to the present invention;

[0053] Figure 9 Schematic diagram of the initial frequency test results after 96Mhz photolithography high fundamental frequency coating after adding the shielding device to the present invention;

[0054] Figure 10 Schematic diagram of the first set of product film thickness test results without using the shielding device to the present invention;

[0055] Figure 11 Schematic diagram of the second set of product film thickness test results without using the shielding device to the present invention;

[0056] Figure 12 Schematic diagram of the first set of product film thickness test results after using the shielding device to the present invention;

[0057] Figure 13 Schematic diagram of the second set of product film thickness test results after using the shielding device to the present invention;

[0058] Figure 14 Schematic diagram of the Wafer chip formed after the cavity electrode manufacturing process for the present invention;

[0059] Figure 15 Schematic diagram of the discharge welding process during the seam welding of the present invention.

[0060] In the figure: 1. Base; 2. Kovar ring; 3. Mounting platform; 4. Conductive adhesive; 5. Lithographed high fundamental frequency wafer with concave cavity structure; 6. Concave cavity structure; 7. Electrode; 8. Lower electrode lead; 9. Upper electrode lead; 10. Lower auxiliary electrode; 11. Upper auxiliary electrode; 12. Upper cover. Detailed implementation mode

[0061] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the present invention.

[0062] Embodiment 1

[0063] In the embodiment of the present invention, a lithographed high fundamental frequency wafer with a concave cavity structure, the material of the lithographed high fundamental frequency wafer 5 with the concave cavity structure is quartz, and its thickness is 8 μm, and the lithographed high fundamental frequency wafer 5 with the concave cavity structure is arranged in a rectangular shape.

[0064] A quartz crystal resonator includes the lithographed high fundamental frequency wafer 5 with the concave cavity structure, as well as a base 1, a mounting platform 3, a kovar ring 2 and an upper cover 12. The kovar ring 2 is fixedly connected to the top edge of the base 1, the mounting platform 3 is fixedly connected to the inner side of the kovar ring 2, the lithographed high fundamental frequency wafer 5 with the concave cavity structure is fixedly installed on the upper surface of the mounting platform 3, and the upper cover 12 is fixedly connected to the top of the kovar ring 2.

[0065] Among them, a concave cavity structure is provided in the middle of the upper surface of the lithographed high fundamental frequency wafer 5 with the concave cavity structure, an electrode 7 is provided in the middle of the concave cavity structure 6, an upper electrode lead 9 and a lower electrode lead 8 are respectively provided on both sides of the electrode 7, and an upper auxiliary electrode 11 and a lower auxiliary electrode 10 are provided at one end of the lithographed high fundamental frequency wafer 5 with the concave cavity structure;

[0066] The thicknesses of the upper auxiliary electrode 11, the lower auxiliary electrode 10, the upper electrode lead 9 and the lower electrode lead 8 are all metal coating films with a thickness of 3 nm, and the material of the metal coating film is gold and chromium;

[0067] The thickness of the upper cover 12 is 0.06 mm, and the composition of the upper cover 12 includes the following components by mass percentage: 15% cobalt, 26% nickel, and 59% iron;

[0068] The thickness of the base 1 is 0.4 mm, the material of the base 1 is 50% ceramic, the kovar ring 2 accounts for 19% of the weight, the composition of the kovar ring 2 includes the following components by mass percentage: 4% cobalt, 4% nickel, 11% iron, and the metal coating film accounts for 22% of the weight.

[0069] Among them, the preparation method of the quartz crystal resonator includes the following steps:

[0070] Step 1, grinding and polishing: Grind and polish the cut Wafer to control its thickness within a certain range;

[0071] Step 2, coating the Wafer: Cover the ground and polished Wafer in Step 1 with a metal layer through ion sputtering technology to give an initial frequency to the quartz crystal frequency piece on the Wafer;

[0072] Step 3, making the cavity electrode;

[0073] Step 4, scribing and dispensing;

[0074] Step 5, fine frequency adjustment;

[0075] Step 6, sealing and soldering;

[0076] Step 7, aging test.

[0077] Furthermore, the grinding and polishing in Step 1 includes the following steps:

[0078] A1. Cut the crystal bar into 3-inch Wafers with a cutting angle of 35°8′ and a thickness controlled at 0.1 mm;

[0079] A2. Place the wafers cut in A1 into the grinding machine fixture for fixation;

[0080] A3. Put the standard block into the thickness gauge and complete the calibration;

[0081] A4. Input the target thickness into the test system;

[0082] A5. Pump the prepared grinding fluid into the grinding machine for grinding; the grinding fluid includes the following components by mass percentage: 20% deionized water, diamond particle abrasive with a diameter of 3 μm, accounting for 30%, thickener 15%, lubricant 5%, organic solvent 30%, dispersant 1%; a pressure sensor is designed on the grinding equipment during grinding, which can quickly capture the force value during grinding and feedback it to the power mechanism, and transmit the force value to the monitoring equipment to achieve the role of real-time control. The system software automatically calculates the grinding time to reduce the wafer thickness to 8 μm, and then perform the polishing process;

[0083] A6. Slicing;

[0084] A7. Detect the grinding size and flatness.

[0085] Furthermore, the ion sputtering in Step 2 includes the following steps:

[0086] I. Load the Wafer wafer that has been ground and polished in Step 1 into the designed fixture and make positioning.

[0087] II. Send the wafer positioned in Step I to the baking area of the coating equipment. After baking, send it to the coating area. Before coating starts, input the sputtering target frequency, start pumping vacuum to 6.7×10-3 pa, and then perform ion sputtering coating. The coating materials are chromium target and gold target. The specific operation is that there is a chromium target on each side of the first cavity in the coating area, and a gold target on each side of the second cavity. Before coating starts, input the sputtering target frequency, start pumping vacuum. After the vacuum meets the requirements, start ion sputtering coating. After the chromium targets on both sides of the first cavity are powered on, usually, gas ionization is generated by argon discharge. Its positive ions are bombarded at high speed on the cathode target under the action of the electromagnetic field, hitting out atoms or molecules of the cathode target and flying to the surface of the Wafer wafer to be coated to deposit a chromium film layer. After completion, the Wafer wafer is sent to the second cavity, and in the same way, gold ions are sputtered and covered on the surface of the Wafer wafer to form a gold film layer. That is, after coating, the first layer on the surface of the Wafer wafer covers the chromium film, and the second layer covers the gold film, so that the Wafer wafer forms an initial frequency.

[0088] It is also possible to design a shielding device in the area with a weaker magnetic field, so that the gold ions sputtered in this area are adsorbed on the shielding device and will not be sputtered onto the Wafer wafer. Thus, during the movement of the Wafer wafer, it is always in the area with a stronger magnetic field and directly receives the gold ions in the sputtering area. As a result, the initial frequency deviation of the quartz crystal frequency piece can only be controlled within -9000 ppm, and the full range can be controlled within 6000 ppm. The surface of the gold target is rough and not smooth enough, and it is in direct contact with the inner wall of the cavity. The gold target cannot achieve 100% contact and fit with the inner wall of the cavity. Now, wrap the contact surface of the gold target with tin foil for adsorption and then contact and fit it with the inner wall of the cavity, which can increase the contact area of the gold target and improve the effectiveness of gold target bombardment and sputtering; increase the adhesion of the product surface coating, improve the frequency stability, and reduce the aging frequency change amount. The thermal expansion coefficient of the quartz crystal frequency piece is 0.5×10-6 K, and the thermal expansion coefficient of gold is 14.2×10-6 K. If a layer of gold is directly sputtered on the surface of the Wafer wafer, the difference in thermal expansion coefficients between the two is relatively large. For the high fundamental frequency quartz crystal resonator made using this method, the annual aging rate change amount is about ±3 ppm. After research, analysis, and verification, first deposit a layer of chromium on the surface of the Wafer wafer (because the thermal expansion coefficient of chromium is 6.2×10-6 K, which is between the thermal expansion coefficients of the quartz crystal frequency piece and gold, playing a bridging role), and then deposit a layer of gold. The annual aging rate change amount of the high fundamental frequency quartz crystal resonator can reach ±1 ppm, improving the coating adhesion and frequency stability of the high fundamental frequency quartz crystal resonator and reducing the aging frequency change amount.

[0089] Among them, the production of the cavity electrode in step three includes the following steps:

[0090] S1. Photoresist preparation: Place the polished Wafer on the spin coater platform. Inject the photoresist into a special syringe, and then inject it onto the surface of the Wafer through the syringe. As the platform rotates, the photoresist is evenly distributed on the surface of the Wafer. The rotation speed of the platform is set at 2000 r / min, and the photoresist coating amount is 0.6 ml.

[0091] S2. Baking: Put the Wafer with the coated photoresist from step S1 into the baking equipment for baking. The baking temperature is 75°C, and the duration is 80 s.

[0092] S3. Expose and develop the Wafer with the coated photoresist.

[0093] S4. Wet etching: Use hydrofluoric acid (HF) as the wet etching solution and add ammonium fluoride as a buffer. The ratio of hydrofluoric acid to ammonium fluoride is 60%:40%. The etching rate is 100 nm / min, and finally a cavity is formed. The thickness of the cavity part is 3 μm. The reaction products are separated from the surface of the etched material and are pumped out of the cavity by the vacuum system.

[0094] S5. Remove the photoresist: Soak and remove the photoresist with acetone.

[0095] Among them, the chip dicing and dispensing in step four includes the following steps: Load the Wafer that has completed the production of the cavity electrode into the carrier fixture. Through the dicing equipment, the Wafer is diced into single-piece quartz crystal frequency chips. Then, through the dispensing equipment, use conductive adhesive 4 to fix the single-piece quartz crystal frequency chips in the base cavity, so that the quartz crystal frequency chips form a circuit with the carrier base 1, and put them into a tunnel furnace with a maximum temperature of 300°C for baking to cure the conductive adhesive.

[0096] Further, the frequency fine-tuning in step five includes the following steps: Put the product that has completed baking and curing after chip dicing and dispensing in step four into the frequency fine-tuning fixture. Through ion etching technology, bombard and etch the gold layer on the surface of the quartz crystal frequency chip. This etching process is completed in a vacuum environment of 6.5×10-3 Pa, and the frequency accuracy reaches ±2 ppm.

[0097] Further, the sealing welding in step six includes the following steps: Transfer the semi-finished product that has completed frequency fine-tuning in step five to the special sealing welding fixture, and put the fixture with the product into a vacuum oven for baking. After baking, perform roll welding and discharging on the four sides of the product through the electrode wheel to weld and seal the upper cover and the semi-finished product that has completed frequency fine-tuning.

[0098] Example 2

[0099] In an embodiment of the present invention, a lithographed high fundamental frequency wafer with a concave cavity structure, the material of the lithographed high fundamental frequency wafer 5 with a concave cavity structure is quartz, and its thickness is 19 μm, and the lithographed high fundamental frequency wafer 5 with a concave cavity structure is arranged in a rectangular shape.

[0100] A quartz crystal resonator includes the lithographed high fundamental frequency wafer 5 with a concave cavity structure, a base 1, a mounting platform 3, a kovar ring 2, and an upper cover 12. The kovar ring 2 is fixedly connected to the top edge of the base 1. The mounting platform 3 is fixedly connected to the inside of the kovar ring 2. The lithographed high fundamental frequency wafer 5 with a concave cavity structure is fixedly installed on the upper surface of the mounting platform 3. The upper cover 12 is fixedly connected to the top of the kovar ring 2.

[0101] Among them, a concave cavity structure is provided in the middle of the upper surface of the lithographed high fundamental frequency wafer 5 with a concave cavity structure. An electrode 7 is provided in the middle of the concave cavity structure 6. Upper electrode leads 9 and lower electrode leads 8 are respectively provided on both sides of the electrode 7. An upper auxiliary electrode 11 and a lower auxiliary electrode 10 are provided at one end of the lithographed high fundamental frequency wafer 5 with a concave cavity structure;

[0102] The upper auxiliary electrode 11, the lower auxiliary electrode 10, the upper electrode leads 9, and the lower electrode leads 8 all have a metal coating film with a thickness of 5 nm. The material of the metal coating film is gold and chromium;

[0103] The thickness of the upper cover 12 is 0.07 mm. The composition of the upper cover 12 includes the following components by mass percentage: cobalt 16%, nickel 28%, and iron 56%;

[0104] The thickness of the base 1 is 0.5 mm. The material of the base 1 is 52% ceramic. The kovar ring 2 accounts for 22% of the total mass. The composition of the kovar ring 2 includes the following components by mass percentage: cobalt 5%, nickel 5%, and iron 12%. The metal coating film accounts for 27% of the total mass.

[0105] Among them, a preparation method of the quartz crystal resonator includes the following steps:

[0106] Step 1, grinding and polishing: The cut Wafer wafer is ground and polished to control its thickness within a certain range;

[0107] Step 2, Wafer wafer coating: The ground and polished Wafer wafer in Step 1 is coated with a metal layer through ion sputtering technology to give an initial frequency to the quartz crystal frequency wafer on the Wafer wafer;

[0108] Step 3, manufacturing the concave cavity electrode;

[0109] Step 4, scribing and dispensing;

[0110] Step Five: Fine Frequency Tuning;

[0111] Step Six: Hermetic Welding;

[0112] Step Seven: Aging Test.

[0113] Furthermore, the polishing and grinding in Step One includes the following steps:

[0114] A1. Cut the ingot into 3-inch Wafer wafers with a cutting angle of 35°19′ and a thickness controlled at 0.11 mm;

[0115] A2. Place the wafers cut in A1 into the grinding machine fixture for fixation;

[0116] A3. Put the standard block into the thickness gauge and complete the calibration;

[0117] A4. Input the target thickness into the test system;

[0118] A5. Pump the prepared grinding fluid into the grinding machine for grinding; the grinding fluid includes the following components by mass percentage: 25% deionized water, diamond particle abrasive with a diameter of 4 μm, accounting for 35%, thickener 12%, lubricant 6%, organic solvent 17%, dispersant 4%; during grinding, a pressure sensor is designed on the grinding equipment to quickly capture the force value during grinding, feedback it to the power mechanism, and transmit the force value to the monitoring equipment to achieve real-time control. The system software automatically calculates the grinding time to reduce the wafer thickness to 19 μm and then perform polishing treatment;

[0119] A6. Slicing;

[0120] A7. Detect the grinding size and flatness.

[0121] Furthermore, the ion sputtering in Step Two includes the following steps:

[0122] I. Load the Wafer wafers polished in Step One into the designed fixture and make positioning;

[0123] II. Feed the wafer positioned in Step I into the baking area of the coating equipment. After baking, transfer it to the coating area. Before coating starts, input the sputtering target frequency and start pumping vacuum until it reaches 6.7×10-3 Pa, then perform ion sputtering coating. The coating materials are chromium target and gold target. The specific operation is as follows: On both sides of the first cavity in the coating area, there is a chromium target, and on both sides of the second cavity, there is a gold target. Before coating starts, input the sputtering target frequency and start pumping vacuum. After the vacuum meets the requirements, start ion sputtering coating. After the chromium targets on both sides of the first cavity are energized, usually, argon gas discharge is used to generate gas ionization. Its positive ions are accelerated by the electromagnetic field to bombard the cathode target at high speed, knocking out atoms or molecules of the cathode target and flying towards the surface of the Wafer to be coated to deposit a chromium film layer. After completion, the Wafer is then transferred to the second cavity, and in the same way, gold ions are sputtered and covered on the surface of the Wafer to form a gold film layer. That is, after coating, the first layer on the surface of the Wafer is covered with a chromium film, and the second layer is covered with a gold film, so that the Wafer forms an initial frequency.

[0124] It is also possible to design a shielding device in the area with a weaker magnetic field, so that the gold ions sputtered in this area are adsorbed on the shielding device and will not be sputtered onto the Wafer, so that during the movement of the Wafer, it is always in the area with a stronger magnetic field and directly receives the gold ions in the sputtering area. As a result, the initial frequency deviation of the quartz crystal frequency chip can only be controlled within -6000 ppm, and the full range can be controlled within 6000 ppm. The surface of the gold target is rough and not smooth enough, and it is in direct contact with the inner wall of the cavity. The gold target cannot achieve 100% contact with the inner wall of the cavity. Now, the contact surface of the gold target is wrapped with tin foil for adsorption and then in contact with the inner wall of the cavity, which can increase the contact area of the gold target and improve the effectiveness of gold target bombardment and sputtering; increase the adhesion of the surface coating of the product, improve the frequency stability, and reduce the aging frequency change. The thermal expansion coefficient of the quartz crystal frequency chip is 0.5×10-6 K, and the thermal expansion coefficient of gold is 14.2×10-6 K. If a layer of gold is directly sputtered on the surface of the Wafer, the difference in thermal expansion coefficients between the two is relatively large. For the high fundamental frequency quartz crystal resonator made using this method, the annual aging rate change is about ±3 ppm. After research, analysis, and verification, first deposit a layer of chromium on the surface of the Wafer (because the thermal expansion coefficient of chromium is 6.2×10-6 K, which is between the thermal expansion coefficients of the quartz crystal frequency chip and gold and plays a bridging role), and then deposit a layer of gold. For the high fundamental frequency quartz crystal resonator, the annual aging rate change can reach ±1 ppm, improving the adhesion of the coating layer and the frequency stability of the high fundamental frequency quartz crystal resonator and reducing the aging frequency change.

[0125] Among them, the production of the concave cavity electrode in Step III includes the following steps:

[0126] S1. Photoresist Preparation: Place the polished Wafer on the spin coater platform. Inject the photoresist into a special syringe and then inject it onto the surface of the Wafer through the syringe. As the platform rotates, the photoresist is evenly distributed on the surface of the Wafer. The rotation speed of the platform is set at 2000 r / min, and the photoresist coating amount is 0.6 ml.

[0127] S2. Baking: Put the Wafer with the coated photoresist from step S1 into the baking equipment for baking. The baking temperature is 80 °C and the duration is 90 s.

[0128] S3. Expose and develop the Wafer with the coated photoresist.

[0129] S4. Wet etching: Use hydrofluoric acid (HF) as the wet etching solution and add ammonium fluoride as a buffer. The ratio of hydrofluoric acid to ammonium fluoride is 60%:40%. The etching rate is 100 nm / min, and finally a cavity is formed. The thickness of the cavity part is 12 μm. The reaction products are separated from the surface of the etched material and pumped out of the cavity by the vacuum system.

[0130] S5. Remove the photoresist: Soak and remove the photoresist with acetone.

[0131] Among them, the dicing and dispensing in step four includes the following steps: For the Wafer after the cavity electrode is made, load it into the carrier fixture. Through the dicing equipment, the Wafer is diced into single-piece quartz crystal frequency chips. Then, through the dispensing equipment, use conductive adhesive 4 to fix the single-piece quartz crystal frequency chips in the base cavity, so that the quartz crystal frequency chips form a circuit with the carrier base 1, and put it into a tunnel furnace with a maximum temperature of 300 °C for baking to cure the conductive adhesive.

[0132] Further, the frequency fine-tuning in step five includes the following steps: Put the product after baking and curing in the dicing and dispensing of step four into the frequency fine-tuning fixture. Through the ion etching technology, bombard and etch the gold layer on the surface of the quartz crystal frequency chip. This etching process is completed in a vacuum environment of 6.5×10-3 Pa, and the frequency accuracy reaches ±2 ppm.

[0133] Further, the sealing in step six includes the following steps: Transfer the semi-finished product after the frequency fine-tuning in step five to the special sealing fixture, and put the fixture with the product into the vacuum oven for baking. After baking, perform roll welding and discharging on the four sides of the product through the electrode wheel to weld and seal the upper cover and the semi-finished product after the frequency fine-tuning.

[0134] Example 3

[0135] In an embodiment of the present invention, a lithographed high fundamental frequency wafer with a concave cavity structure, the material of the lithographed high fundamental frequency wafer 5 with a concave cavity structure is quartz, and its thickness is 30 μm, and the lithographed high fundamental frequency wafer 5 with a concave cavity structure is rectangularly arranged.

[0136] A quartz crystal resonator includes the lithographed high fundamental frequency wafer 5 with a concave cavity structure, a base 1, a mounting platform 3, a kovar ring 2 and an upper cover 12. The kovar ring 2 is fixedly connected to the top edge of the base 1. The mounting platform 3 is fixedly connected to the inside of the kovar ring 2. The lithographed high fundamental frequency wafer 5 with a concave cavity structure is fixedly installed on the upper surface of the mounting platform 3. The upper cover 12 is fixedly connected to the top of the kovar ring 2.

[0137] Among them, a concave cavity structure is provided in the middle of the upper surface of the lithographed high fundamental frequency wafer 5 with a concave cavity structure. An electrode 7 is provided in the middle of the concave cavity structure 6. Upper electrode leads 9 and lower electrode leads 8 are respectively provided on both sides of the electrode 7. An upper auxiliary electrode 11 and a lower auxiliary electrode 10 are provided at one end of the lithographed high fundamental frequency wafer 5 with a concave cavity structure;

[0138] The upper auxiliary electrode 11, the lower auxiliary electrode 10, the upper electrode leads 9 and the lower electrode leads 8 all have a metal coating film with a thickness of 6 nm. The material of the metal coating film is gold and chromium;

[0139] The thickness of the upper cover 12 is 0.07 mm. The composition of the upper cover 12 includes the following components by mass percentage: cobalt 18%, nickel 30%, iron 52%;

[0140] The thickness of the base 1 is 0.7 mm. The material of the base 1 is 53% ceramic. The kovar ring 2 accounts for 25% of the total mass. The composition of the kovar ring 2 includes the following components by mass percentage: cobalt 6%, nickel 6%, iron 13%. The metal coating film accounts for 31% of the total mass.

[0141] Among them, a preparation method of the quartz crystal resonator includes the following steps:

[0142] Step 1, grinding and polishing: The cut Wafer wafer is ground and polished to control its thickness within a certain range;

[0143] Step 2, Wafer wafer coating: The ground and polished Wafer wafer in Step 1 is covered with a metal layer through ion sputtering technology to give an initial frequency to the quartz crystal frequency wafer on the Wafer wafer;

[0144] Step 3, manufacturing the concave cavity electrode;

[0145] Step 4, scribing and dispensing;

[0146] Step 5, fine frequency adjustment;

[0147] Step 6: Hermetic welding;

[0148] Step 7: Aging test.

[0149] Further, the polishing and grinding in the first step includes the following steps:

[0150] A1. Cut the ingot into 3-inch Wafer wafers with a cutting angle of 35°29′ and a thickness controlled at 0.12 mm;

[0151] A2. Place the wafers cut in A1 into the grinding machine fixture for fixation;

[0152] A3. Put the standard block into the thickness gauge and complete the calibration;

[0153] A4. Input the target thickness into the test system;

[0154] A5. Pump the prepared grinding fluid into the grinding machine for grinding; the grinding fluid includes the following components by mass percentage: 30% deionized water, diamond particle abrasive with a diameter of 5 μm, accounting for 40%, thickener 8%, lubricant 8%, organic solvent 15%, dispersant 7%; during grinding, a pressure sensor is designed on the grinding equipment to quickly capture the force value during grinding and feedback it to the power mechanism, and transmit the force value to the monitoring equipment to achieve real-time control. The system software automatically calculates the grinding time to reduce the wafer thickness to 30 μm, and then performs polishing treatment;

[0155] A6. Slicing;

[0156] A7. Detect the grinding size and flatness.

[0157] Further, the ion sputtering in the second step includes the following steps:

[0158] I. Load the Wafer wafers polished and ground in the first step into the designed fixture and make positioning;

[0159] II. Feed the wafer positioned in Step I into the baking area of the coating equipment. After baking, feed it into the coating area. Before coating starts, input the sputtering target frequency, start vacuum pumping until it reaches 6.7×10-3 Pa, and then perform ion sputtering coating. The coating materials are chromium target and gold target. The specific operation is that there is a chromium target on each side of the first cavity in the coating area, and a gold target on each side of the second cavity. Before coating starts, input the sputtering target frequency, start vacuum pumping. After the vacuum meets the requirements, start ion sputtering coating. After the chromium targets on both sides of the first cavity are powered on, usually, argon gas discharge is used to generate gas ionization. Its positive ions are accelerated by the electromagnetic field to bombard the cathode target at high speed, knocking out atoms or molecules of the cathode target and flying towards the surface of the wafer to be coated to deposit a chromium film layer. After completion, the wafer is sent into the second cavity, and in the same way, gold ions are sputtered and covered on the surface of the wafer to form a gold film layer. That is, after coating, the first layer on the surface of the wafer is covered with a chromium film, and the second layer is covered with a gold film, so that the wafer forms an initial frequency.

[0160] It is also possible to design a shielding device in the area with a weak magnetic field, so that the gold ions sputtered in this area are adsorbed on the shielding device and will not be sputtered onto the wafer. Thus, during the movement of the wafer, it is always in the area with a strong magnetic field and directly receives the gold ions in the sputtering area. As a result, the initial frequency deviation of the quartz crystal frequency chip can only be controlled within -3000 ppm, and the full range can be controlled within 6000 ppm. The surface of the gold target is rough and not smooth enough, and it is in direct contact with the inner wall of the cavity. The gold target cannot achieve 100% contact and fit with the inner wall of the cavity. Now, the contact surface of the gold target is wrapped with tin foil for adsorption and then in contact and fit with the inner wall of the cavity, which can increase the contact area of the gold target and improve the effectiveness of gold target bombardment and sputtering; increase the adhesion of the product surface coating, improve the frequency stability, and reduce the aging frequency change. The thermal expansion coefficient of the quartz crystal frequency chip is 0.5×10-6 K, and the thermal expansion coefficient of gold is 14.2×10-6 K. If a layer of gold is directly sputtered on the surface of the wafer, the difference in thermal expansion coefficients between the two is relatively large. For the high fundamental frequency quartz crystal resonator made using this method, the annual aging rate change is about ±3 ppm. After research, analysis, and verification, first deposit a layer of chromium on the surface of the wafer (because the thermal expansion coefficient of chromium is 6.2×10-6 K, which is between the thermal expansion coefficients of the quartz crystal frequency chip and gold, playing a bridging role), and then deposit a gold layer. For the high fundamental frequency quartz crystal resonator, the annual aging rate change can reach ±1 ppm, improving the coating adhesion and frequency stability of the high fundamental frequency quartz crystal resonator and reducing the aging frequency change.

[0161] Among them, the production of the concave cavity electrode in Step III includes the following steps:

[0162] S1. Photoresist preparation: Place the polished Wafer on the spin coater platform. Inject the photoresist into a special syringe, and then inject it onto the surface of the Wafer through the syringe. As the platform rotates, the photoresist is evenly distributed on the surface of the Wafer. The rotation speed of the platform is set at 2000 r / min, and the photoresist coating amount is 0.6 ml.

[0163] S2. Baking: Place the Wafer with the coated photoresist from step S1 into the baking equipment for baking. The baking temperature is 85°C, and the duration is 100 s.

[0164] S3. Expose and develop the Wafer with the coated photoresist.

[0165] S4. Wet etching: Use hydrofluoric acid (HF) as the wet etching solution and add ammonium fluoride as a buffer. The ratio of hydrofluoric acid to ammonium fluoride is 60%:40%. The etching rate is 100 nm / min, and finally a cavity is formed. The thickness of the cavity part is 20 μm. The reaction products are separated from the surface of the etched material and pumped out of the cavity by the vacuum system.

[0166] S5. Remove the photoresist: Soak and remove the photoresist with acetone.

[0167] Among them, the die dicing and dispensing in step four includes the following steps: Place the Wafer with the cavity electrode fabricated on a carrier fixture. Through the die dicing equipment, the Wafer is diced into single-piece quartz crystal frequency chips. Then, through the dispensing equipment, use conductive adhesive 4 to fix the single-piece quartz crystal frequency chips in the base cavity, so that the quartz crystal frequency chips form a circuit with the carrier base 1, and place them in a tunnel furnace with a maximum temperature of 300°C for baking to cure the conductive adhesive.

[0168] Further, the frequency fine-tuning in step five includes the following steps: Place the product after baking and curing in the die dicing and dispensing in step four into the frequency fine-tuning fixture. Through the ion etching technology, bomb and etch the gold layer on the surface of the quartz crystal frequency chip. This etching process is completed in a vacuum environment of 6.5×10-3 Pa, and the frequency accuracy reaches ±2 ppm.

[0169] Further, the sealing welding in step six includes the following steps: Transfer the semi-finished product after frequency fine-tuning in step five to the special fixture for sealing welding, and place the fixture with the product into a vacuum oven for baking. After baking, perform roll welding and discharging on the four sides of the product through the electrode wheel to weld and seal the upper cover and the semi-finished product after frequency fine-tuning.

[0170] The verification data of Examples 1-3 are as Figures 3 - 5 shown.

[0171] During the simultaneous seam welding operation, heat is generated. Currently, the heat dissipation problem has not been well solved, resulting in no new breakthroughs in the number of workstations of the tooling fixture. During the seam welding process, the generated heat will affect the frequency of the quartz crystal resonator. After the original frequency was finely tuned, the output frequency of the quartz crystal resonator could be controlled within ±2 ppm. However, after the cover was added for seam welding and sealing operation, the output frequency of the quartz crystal resonator would increase to ±10 ppm. To solve this problem, in the prior art, most methods are to increase the length, width of the seam welding fixture and the distance between each positioning groove in the fixture to ensure heat dissipation during the seam welding process of the quartz crystal resonator, so that after seam welding, the frequency of the quartz crystal resonator can be controlled within ±8 ppm. However, this method also has defects: during seam welding, the travel of the seam welding wheel is relatively long, and the seam welding efficiency is low. However, heat conduction is directly related to the contact area and the conduction medium. In this application, the diameter of the seam welding electrode wheel was changed from 13 mm to 15 mm, 17 mm, 18 mm, 19 mm, and 20 mm for verification, and the results are as follows in the table:

[0172]

[0173] As can be seen from the above table, when the diameter of the seam welding wheel increases from 13 mm to 18 mm, the influence on the frequency after encapsulation is the smallest, that is, the frequency concentration is better.

[0174] Meanwhile, in Examples 1 - 3, the seam welding mechanism on the encapsulation machine was designed, a pre-pressing mechanism and a wave discharge mechanism were set, and the discharge welding timing during the seam welding process was optimized to make the seam welding discharge method achieve a wave discharge mode, with the wave peaks and valleys continuously switching, and the heat generated during the seam welding process can be quickly dissipated, as Figure 15 shown. The seam welding discharge design parameters are as follows in the table:

[0175]

[0176] Effect verification of adding a shielding device:

[0177] 1. Test data of the frequency deviation range after sputtering coating before adding the shielding device:

[0178] After 96Mhz lithography high fundamental frequency sputtering coating, the initial frequency deviation range was -14721.67 ppm to -7922.08 ppm, and the actual full range was -6799.59 ppm, as Figure 6 and Figure 8 shown.

[0179] 2. Test data of the frequency deviation range after sputtering coating after adding the shielding device:

[0180] After sputtering coating with a high base frequency of 96 MHz by lithography, the initial frequency deviation ranges from -8054.45 ppm to -3934.70 ppm, and the actual full range is -4199.75 ppm, as Figure 7 and Figure 9 shown.

[0181] 3. Before adding the shielding device, for products at different positions within the Wafer after sputtering coating, the surface film thickness deviation can only be controlled within ±3%, and the film thickness deviation data and graphs are as Figure 10 and Figure 11 shown.

[0182] 4. After adding the shielding device, for products at different positions within the Wafer after sputtering coating, the surface film thickness deviation can only be controlled within ±1.5%, and the film thickness deviation data and graphs are as Figure 12 and Figure 13 shown.

[0183] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention. Any reference signs in the claims should not be regarded as limiting the claims involved.

[0184] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. Preparation method of a quartz crystal resonator, characterized in that, it comprises the following steps: Step 1, grinding and polishing: The cut Wafer is ground and polished to control its thickness within a certain range; Step 2, coating the Wafer: The ground and polished Wafer in Step 1 is covered with a metal layer through ion sputtering technology to give an initial frequency to the quartz crystal frequency sheet on the Wafer; Step 3, manufacturing the cavity electrode; Step 4, dicing and dispensing; Step 5, fine frequency adjustment; Step 6, sealing and soldering; Step 7, aging test; The grinding and polishing in Step 1 comprises the following steps: A1. Cut the crystal bar into 3-inch Wafers with a cutting angle of 35°8′ - 35°29′ and a thickness controlled within 0.1 - 0.12 mm; A2. Place the Wafer cut in A1 into the grinding jig for fixation; A3. Place the standard block into the thickness gauge and complete the calibration; A4. Input the target thickness into the test system; A5. Pump the prepared grinding fluid into the grinding machine for grinding; A6. Slicing; A7. Detect the grinding size and flatness; The ion sputtering in Step 2 comprises the following steps: I. Load the Wafer completed with grinding and polishing in Step 1 into the designed jig and make good positioning; II. Feed the wafer positioned in Step I into the baking area of the coating equipment. After baking is completed, feed it into the coating area. Before starting the coating, input the sputtering target frequency and start pumping vacuum to 6.7×10 -3 Pa and then perform ion sputtering coating. The coating materials are chromium target and gold target; The manufacturing of the cavity electrode in Step 3 comprises the following steps: S1. Photoresist preparation: Place the ground Wafer on the spin coating platform, inject the photoresist into the special syringe, and then inject it onto the surface of the Wafer through the syringe. As the spin coating platform runs, the photoresist is evenly distributed on the surface of the Wafer. The rotation speed of the spin coating platform is set at 2000 r / min, and the photoresist coating amount is 0.6 ml; S2. Baking: Place the Wafer coated with photoresist in Step S1 into the baking equipment for baking. The baking temperature is 75 - 85°C, and the duration is 80 - 100 s; S3. Expose and develop the Wafer coated with photoresist; S4. Wet etching: Use hydrofluoric acid (HF) as the wet etching solution and add ammonium fluoride as a buffer. The ratio of hydrofluoric acid to ammonium fluoride is 60%:40%; the etching rate is 100 nm / min, and finally a cavity is formed. The thickness of the cavity part is 3 - 20 μm. The reaction products are separated from the surface of the etched material and are pumped out of the cavity by the vacuum system; S5. Remove the photoresist: Soak and remove the photoresist with acetone.

2. The preparation method of the quartz crystal resonator according to claim 1, characterized in that, the dicing and dispensing in Step 4 comprises the following steps: Load the Wafer completed with the manufacturing of the cavity electrode into the carrier jig, split the Wafer into single-piece quartz crystal frequency sheets through the dicing equipment, and then use the conductive adhesive (4) through the dispensing equipment to fix the single-piece quartz crystal frequency sheets in the base cavity, so that the quartz crystal frequency sheets form a circuit with the carrier base (1), and place them in a tunnel furnace with a maximum temperature of 300°C for baking to cure the conductive adhesive.

3. The manufacturing method of the quartz crystal resonator according to claim 2, characterized in that, The fine frequency adjustment in the fifth step includes the following steps: putting the product that has completed baking and curing after dicing and dispensing in the fourth step into a fine frequency adjustment fixture, and bombarding and etching the gold layer on the surface of the quartz crystal frequency chip through ion etching technology. This etching process is completed in a vacuum environment of 6.5×10 -3 Pa, and the frequency accuracy reaches ±2 ppm.

4. The manufacturing method of the quartz crystal resonator according to claim 3, characterized in that, the sealing welding in step six includes the following steps: transferring the semi-finished product with fine frequency adjustment completed in step five into a special jig for sealing welding, putting the jig containing the product into a vacuum oven for baking, and after the baking is completed, performing roll welding and discharging on the four sides of the product through an electrode wheel to weld and seal the upper cover and the semi-finished product with fine frequency adjustment completed.

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