Hemispherical electrode base and sintering method thereof

Abstract

The present invention discloses a hemispherical electrode base and a sintering method thereof, comprising the following steps: preparing a plurality of glass electrode assemblies, wherein the plurality of glass electrode assemblies correspond one to one to a plurality of electrode holes of the hemispherical electrode base, the glass electrode assemblies comprising an electrode needle and a glass column coaxially fixed on the electrode needle, the glass column matching the electrode hole on the hemispherical electrode base, inserting the glass electrode assemblies into the corresponding electrode holes of the hemispherical electrode base, placing an oxygen-free copper tube in the central hole of the hemispherical electrode base, arranging brazing material between the oxygen-free copper tube and the wall of the central hole to obtain a hemispherical electrode base pre-finished product, and sintering the hemispherical electrode base pre-finished product in sections to obtain the hemispherical electrode base; the present invention can complete the glass insulation sealing sintering between the metal electrode and the metal base, as well as the brazing sintering between the oxygen-free copper tube and the metal base in one step, thereby shortening the process flow, reducing costs and improving the yield rate.

Description

Technical Field

[0001] The present invention relates to the technical field of inertial navigation, and in particular to a hemispherical electrode base and a sintering method thereof. Background Art

[0002] The HRG is a solid-state wave gyroscope based on the Coriolis effect. It boasts high precision, long life, and high reliability, making it a key area of ​​future gyroscope development. Future applications for HRGs include aerospace, navigation, and many other fields. As a key component of a HRG, a high Q value is a crucial metric for evaluating the quality of the resonator and also impacts its performance. Operating the HRG in a vacuum environment is crucial for achieving its high precision and long life. This vacuum significantly reduces the loss of energy from the resonator's vibration due to air damping. Furthermore, a vacuum suppresses vibrational modal interference. Molecular collisions in the air introduce random noise, destabilizing the four antinodes of the resonator.

[0003] Therefore, in order to ensure the long-term use of the hemispherical resonant gyroscope (including MEMS gyroscope) head in a high vacuum environment, the head is generally sealed in a cavity composed of an excitation cover and a base. The head signal is led out by an electrode needle through the base. The electrode needle and the base are connected by a glass sintering seal, and an oxygen-free copper tube is brazed. After the cavity is vacuum-exhausted through the oxygen-free copper tube, the oxygen-free copper tube is clamped off and the tube mouth is sealed.

[0004] Therefore, the preparation process of the electrode base is crucial for achieving excellent airtightness. However, due to the inconsistency between the sintering temperatures of glass sintering and metal brazing, excessively high glass sintering temperatures will severely impair the metal brazing effect. Therefore, it is impossible to simultaneously seal the electrode needle and oxygen-free copper tube to the base in a single process. The traditional electrode base sintering process uses a two-step sintering process: first, the glass powder, electrode, and electrode base are sintered at high temperature (1000°C atmosphere), followed by vacuum brazing of the exhaust copper tube (850°C atmosphere). Furthermore, the glass powder must first be mixed with an organic adhesive and preformed using a traditional press. High-temperature sintering removes the binder to produce sintered glass particles. These glass particles are then assembled with the metal electrode needles and attached to the electrode base. High-temperature co-firing is then performed to obtain the sintered electrode-base product. As can be seen, the traditional base preparation process is relatively cumbersome, and the multiple sintering steps can easily lead to poor airtightness of the meter head, affecting the performance and service life of the hemispherical resonator gyroscope. Summary of the Invention

[0005] In response to the problems in the background technology, the present invention proposes a hemispherical electrode base and a sintering method thereof, which can complete the glass insulation sealing sintering between the metal electrode and the metal base, as well as the brazing sintering between the oxygen-free copper tube and the metal base in one step, shortening the process flow, reducing costs and improving the yield rate.

[0006] The present invention adopts the following technical solutions:

[0007] A sintering method for a hemispherical electrode base comprises the following steps:

[0008] Prepare multiple glass electrode assemblies, each of which corresponds to a plurality of electrode holes on the hemispherical electrode base. The glass electrode assemblies include an electrode needle and a glass column coaxially fixed to the electrode needle, and the glass column matches the electrode hole on the hemispherical electrode base.

[0009] The glass electrode assembly is inserted into the corresponding electrode hole of the hemispherical electrode base, and the oxygen-free copper tube is placed in the central hole of the hemispherical electrode base. Brazing material is set between the oxygen-free copper tube and the wall of the central hole to obtain a pre-finished hemispherical electrode base.

[0010] Sintering the hemispherical electrode base pre-finished product in sections to obtain the hemispherical electrode base;

[0011] The raw materials for preparing the glass column include, by mass percentage, 25wt%-35wt% of quartz powder, 0wt%-5wt% of alumina powder, 25wt%-35wt% of boric acid, 8wt%-22wt% of sodium carbonate, 3wt%-8wt% of potassium carbonate, 5wt%-10wt% of calcium carbonate, 0wt%-10wt% of lithium carbonate, and 1wt%-7wt% of zinc oxide.

[0012] Optionally, the preparation process of the glass electrode assembly is:

[0013] The raw materials for preparing the glass column are mixed, melted at 1400-1450℃, kept warm for 1.5-2.5h, ball-milled into powder after cooling, and passed through a 250-350 mesh sieve to obtain composite glass powder. The composite glass powder is pre-pressed onto the electrode needle to form a glass electrode assembly.

[0014] Optionally, the pre-pressing process is:

[0015] The composite glass powder and water are mixed at a mass ratio of 10:1 to obtain glass slurry. The electrode needle is placed in a mold and 0.4-0.6g of glass slurry is injected. The mold is pre-pressed at a pressure of 100Kg for 5-10s, demolded, and dried to obtain a glass electrode assembly.

[0016] Optionally, the process of staged sintering is:

[0017] First heat to the first temperature and keep warm for 4-6 minutes, then heat to the second temperature and keep warm for 4-12 minutes, then heat to the third temperature and keep warm for 9-25 minutes, and then cool to room temperature. The first temperature is 300-320℃, the second temperature is 700-760℃, and the third temperature is 850-900℃.

[0018] Optionally, the heating rate from room temperature to the first temperature is 300-320°C / min, the heating rate from the first temperature to the second temperature is 400-420°C / min, and the heating rate from the second temperature to the third temperature is 50-60°C / min.

[0019] Optionally, the process of cooling to room temperature is as follows:

[0020] Cool down to 600-620℃ at 50-55℃ / min, then cool down to 400-420℃ at 10-12℃ / min, and then cool naturally to 70-80℃.

[0021] Optionally, the hemispherical electrode base prefabricated product is sintered in sections using a high-frequency induction method and under low-pressure Ar gas or vacuum conditions.

[0022] As a general inventive concept, the present invention also provides a hemispherical electrode base sintered by the above-mentioned sintering method.

[0023] Compared with the prior art, the advantages of the present invention are:

[0024] The present invention is designed to melt and sinter glass powder at medium temperature, which can be melted and sintered normally at the brazing temperature, so that the glass insulation sealing sintering between the metal electrode and the metal base and the brazing sintering between the oxygen-free copper tube and the metal base can be completed in one step. Compared with the traditional two-step sintering, the process flow is shortened, the cost is reduced and the yield rate is improved. In addition, the viscosity after melting is suitable. After melting at medium temperature, it can flow into and fill between the electrode needle and the electrode base electrode hole wall without dripping, so that the electrode needle and the electrode base can be well sealed after cooling. In addition, the thermal expansion coefficient of the glass powder matches that of the common electrode base material, and the interface fusion is free of cracks.

[0025] Practice has shown that the medium-temperature glass powder has good resistance to thermal shock. After 50 rounds of thermal shock cycle tests (-40~80℃), the leakage rate and short-circuit tests are normal. Therefore, the medium-temperature glass powder can adapt to the extreme application environment of the hemispherical resonant gyroscope, ensuring the long-term use of the hemispherical resonant gyroscope head in a high vacuum environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to make the present invention more easily understood, the present invention will be described in more detail with reference to the specific embodiments shown in the accompanying drawings. These drawings only depict typical embodiments of the present invention and should not be considered as limiting the scope of protection of the present invention.

[0027] Figure 1 The figure is a flow chart of a sintering method for a hemispherical electrode base according to an embodiment of the present invention.

[0028] Figure 2Schematic diagram of the three-dimensional structure of a hemispherical electrode base prefabricated product according to an embodiment of the present invention.

[0029] Figure 3 Schematic diagram of the exploded structure of the hemispherical electrode base prefabricated product according to an embodiment of the present invention. DETAILED DESCRIPTION

[0030] The following describes the embodiments of the present invention with reference to the accompanying drawings so that those skilled in the art can better understand the present invention and implement it. However, the enumerated embodiments are not intended to limit the present invention. Unless there is a conflict, the following embodiments and the technical features in the embodiments can be combined with each other, wherein the same components are represented by the same figure marks.

[0031] like Figure 1 As shown, the present invention provides a sintering method for a hemispherical electrode base, comprising the following steps:

[0032] like Figure 2 and Figure 3 As shown, a plurality of glass electrode assemblies 2 are prepared, and the plurality of glass electrode assemblies 2 correspond one to one with the plurality of electrode holes 12 of the hemispherical electrode base 1. The glass electrode assembly 2 includes an electrode needle 21 and a glass column 22 coaxially fixed on the electrode needle 21. The glass column 22 matches the electrode hole 12 on the hemispherical electrode base 1.

[0033] The glass electrode assembly 2 is inserted into the corresponding electrode hole 12 of the hemispherical electrode base 1, and the oxygen-free copper tube 3 is placed in the central hole 11 of the hemispherical electrode base 1. Brazing material is provided between the oxygen-free copper tube 3 and the wall of the central hole 11 to obtain a pre-finished hemispherical electrode base.

[0034] Sintering the hemispherical electrode base pre-finished product in sections to obtain the hemispherical electrode base;

[0035] The raw materials for preparing the glass column include, by mass percentage, 25wt%-35wt% of quartz powder, 0wt%-5wt% of alumina powder, 25wt%-35wt% of boric acid, 8wt%-22wt% of sodium carbonate, 3wt%-8wt% of potassium carbonate, 5wt%-10wt% of calcium carbonate, 0wt%-10wt% of lithium carbonate, and 1wt%-7wt% of zinc oxide.

[0036] The present invention designs a glass powder that can be melted and sintered at medium temperatures. It can melt and sinter normally at the brazing temperature, thereby completing the glass insulation sealing sintering between the metal electrode and the metal base, as well as the brazing sintering between the oxygen-free copper tube and the metal base in a single step. Compared with the traditional two-step sintering, it shortens the process flow, reduces costs, and improves the yield rate. In addition, its viscosity after melting is suitable. After melting at medium temperatures, it can flow and fill between the electrode needle and the electrode base electrode hole wall without dripping, so that after cooling, the electrode needle and the electrode base can be well sealed. In addition, the thermal expansion coefficient of the glass powder matches that of common electrode base materials, and the interface fusion is crack-free.

[0037] Practice has shown that the medium-temperature glass powder has good resistance to thermal shock. After 50 rounds of thermal shock cycle tests (-40~80℃), the leakage rate and short-circuit tests are normal. Therefore, the medium-temperature glass powder can adapt to the extreme application environment of the hemispherical resonant gyroscope, ensuring the long-term use of the hemispherical resonant gyroscope head in a high vacuum environment.

[0038] Specifically, the preparation process of the glass electrode assembly is as follows:

[0039] The raw materials for preparing the glass column are mixed, melted at 1400-1450℃, kept warm for 1.5-2.5h, ball-milled into powder after cooling, and passed through a 250-350 mesh sieve to obtain composite glass powder. The composite glass powder is pre-pressed onto the electrode needle to form a glass electrode assembly.

[0040] Specifically, the process of pre-pressing is as follows:

[0041] The composite glass powder and water are mixed at a mass ratio of 10:1 to obtain glass powder. The electrode needle is placed in a mold and 0.4-0.6g of glass powder is injected. The mold is pre-pressed under a pressure of 100Kg for 5-10s, demolded, and dried to obtain a glass electrode assembly.

[0042] Specifically, the process of staged sintering is as follows:

[0043] First heat to the first temperature and keep warm for 4-6 minutes, then heat to the second temperature and keep warm for 4-12 minutes, then heat to the third temperature and keep warm for 9-25 minutes, and then cool to room temperature. The first temperature is 300-320℃, the second temperature is 700-760℃, and the third temperature is 850-900℃.

[0044] By designing the above-mentioned special sintering curve, the insulation of each temperature section corresponds to the drainage process (300-320℃), the sintering exhaust process (700-760℃), and the glass powder melting + brazing material melting process (850-900℃), which satisfies the normal exhaust of the glass powder sintering cycle, the melting sintering and the insulation treatment of the metal brazing process, ensuring that the solder and glass powder can be fully melted and fully infiltrated with the material surface, thereby improving the overall vacuum performance of the product.

[0045] Specifically, the heating rate from room temperature to the first temperature is 300-320°C / min, the heating rate from the first temperature to the second temperature is 400-420°C / min, and the heating rate from the second temperature to the third temperature is 50-60°C / min.

[0046] Specifically, the process of cooling to room temperature is as follows:

[0047] Cool down to 600-620℃ at 50-55℃ / min, then cool down to 400-420℃ at 10-12℃ / min, and then cool naturally to 70-80℃.

[0048] The cooling process starts fast and then slows down, which can ensure the normal release of stress in the glass and metal materials during the cooling process.

[0049] Specifically, the hemispherical electrode base prefabricated product is sintered in sections using a high-frequency induction method under low-pressure Ar gas or vacuum conditions.

[0050] The sintering environment adopts controllable high-frequency induction heating + low-pressure Ar gas (or vacuum), which has the function of controlling the heating speed of the metal. Common metals can be processed by this method. At the same time, the low-pressure Ar gas (vacuum) environment can prevent product oxidation and quickly release the gas generated during the sintering process.

[0051] Example 1 (304 stainless steel substrate sintering process)

[0052] 1) Prepare a glass powder product that meets the temperature and thermal expansion requirements by mixing the following raw materials in percentage by mass: 25% quartz powder, 5% alumina powder, 30% boric acid, 20% sodium carbonate, 5% potassium carbonate, 7% calcium carbonate, 3% lithium carbonate, and 5% zinc oxide, for a total of 100%. Mix the weighed raw materials, melt them at 1400°C, and hold the temperature for 2 hours. Cool the glass melt in cold water, ball-mill the cooled glass frit, and sieve it through a 300-mesh sieve to obtain glass powder of a suitable particle size for later use.

[0053] 2) First, place the hemispherical electrode base 1 on the non-metallic mold, then place the prefabricated glass electrode assembly 2 into the corresponding electrode hole 12 of the hemispherical electrode base 1, and place the prefabricated oxygen-free copper tube 1 and silver solder in the center hole 11.

[0054] 3) Place the sample to be sintered in a high-frequency induction atmosphere furnace and set a specific temperature curve: 0-300℃ heating rate of 300℃ / min, 300℃ holding for 5min, 300-700℃ heating rate of 400℃ / min, 700℃ holding for 5min, 700-850℃ heating rate of 50℃ / min, 850℃ holding for 10min, 850-600℃ cooling rate of 50℃ / min, 600-400℃ cooling rate of 10℃ / min, and natural cooling from 400-80℃. The insulation of each temperature section corresponds to the drainage process (300℃), the sintering exhaust process (700℃), and the glass powder melting and solder melting process (850℃). The cooling process is fast at first and then slow to ensure that the stress of the glass and metal materials is normally released during the cooling process. Finally, the sample can be taken out when the temperature drops to 80℃.

[0055] 4) Conduct sample performance testing:

[0056] 50 rounds of thermal shock cycle test (-40-80℃) were carried out, and the leakage rate was tested by helium mass spectrometer (<1×10 - 11 Pa·m 3 The results of the short-circuit test using a multimeter are shown in Table 1.

[0057] Table 1

[0058]

[0059] Example 2 (Kovar-based glass powder)

[0060] 1) Prepare a glass powder product that meets the temperature and thermal expansion requirements by mixing the following raw materials according to mass percentage: 30% quartz powder, 5% alumina powder, 28% boric acid, 10% sodium carbonate, 5% potassium carbonate, 7% calcium carbonate, 10% lithium carbonate, and 5% zinc oxide, totaling 100%. Mix the weighed raw materials, melt them at 1450°C, and hold the temperature for 2 hours. Cool the glass melt in cold water, ball-mill the cooled glass frit, and sieve it through a 300-mesh sieve to obtain glass powder of appropriate particle size for later use.

[0061] 2) First, place the hemispherical electrode base 1 on the non-metallic mold, then place the prefabricated glass electrode assembly 2 into the corresponding electrode hole 12 of the hemispherical electrode base 1, and place the prefabricated oxygen-free copper tube 1 and silver solder in the center hole 11.

[0062] 3) Place the sample to be sintered in a high-frequency induction atmosphere furnace and set a specific temperature curve: 0-300℃ heating rate of 300℃ / min, 300℃ holding for 5min, 300-750℃ heating rate of 400℃ / min, 750℃ holding for 10min, 750-850℃ heating rate of 50℃ / min, 850℃ holding for 20min, 850-600℃ cooling rate of 50℃ / min, 600-400℃ cooling rate of 10℃ / min, and natural cooling from 400-80℃. The holding time of each temperature section corresponds to the drainage process (300℃), the sintering exhaust process (750℃), and the glass powder melting and solder melting process (850℃). The cooling process is fast at first and then slow to ensure that the stress of the glass and metal materials is normally released during the cooling process. Finally, the sample can be taken out after the temperature drops to 80℃.

[0063] 4) Conduct sample performance testing:

[0064] 50 rounds of thermal shock cycle test (-40-80℃) were carried out, and the leak rate was tested by helium mass spectrometer (<1×10 - 11 Pa·m 3 The results of the short-circuit test using a multimeter are shown in Table 2.

[0065] Table 2

[0066]

[0067] Through experimental verification, the comparison of two metal substrate processes uses a specific glass powder formula and customized temperature curve, which can simultaneously meet the needs of glass sealing sintering and metal brazing processes. Compared with the two-step sintering method, it has obvious advantages and product yield.

[0068] The embodiments described above are merely preferred embodiments of the present invention. The phrases "in one embodiment," "in another embodiment," "in yet another embodiment," or "in other embodiments" used in this specification may refer to one or more of the same or different embodiments of the present disclosure. Any common changes and substitutions made by those skilled in the art within the scope of the present invention are intended to be encompassed within the scope of protection of the present invention.

Claims

1. A sintering method for a hemispherical electrode base, characterized in that: The following steps are involved: Prepare multiple glass electrode assemblies, each of which corresponds to a plurality of electrode holes on the hemispherical electrode base. The glass electrode assemblies include an electrode needle and a glass column coaxially fixed to the electrode needle, and the glass column matches the electrode hole on the hemispherical electrode base. The glass electrode assembly is inserted into the corresponding electrode hole of the hemispherical electrode base, and the oxygen-free copper tube is placed in the central hole of the hemispherical electrode base. Brazing material is set between the oxygen-free copper tube and the wall of the central hole to obtain a pre-finished hemispherical electrode base. Sintering the hemispherical electrode base pre-finished product in sections to obtain the hemispherical electrode base; The raw materials for preparing the glass column include, by mass percentage, 25wt%-35wt% of quartz powder, 0wt%-5wt% of alumina powder, 25wt%-35wt% of boric acid, 8wt%-22wt% of sodium carbonate, 3wt%-8wt% of potassium carbonate, 5wt%-10wt% of calcium carbonate, 0wt%-10wt% of lithium carbonate, and 1wt%-7wt% of zinc oxide. The preparation process of the glass electrode assembly is as follows: The raw materials for preparing the glass column are mixed, melted at 1400-1450℃, kept warm for 1.5-2.5h, ball-milled into powder after cooling, and passed through a 250-350 mesh sieve to obtain composite glass powder. The composite glass powder is pre-pressed onto the electrode needle to form a glass electrode assembly.

2. The sintering method of the hemispherical electrode base according to claim 1, characterized in that: The process of pre-pressing is as follows: The composite glass powder and water are mixed at a mass ratio of 10:1 to obtain glass slurry. The electrode needle is placed in a mold and 0.4-0.6g of glass slurry is injected. The mold is pre-pressed at a pressure of 100Kg for 5-10s, demolded, and dried to obtain a glass electrode assembly.

3. The sintering method of the hemispherical electrode base according to claim 1 or 2, characterized in that: The process of staged sintering is: first heat to the first temperature and keep it for 4-6 minutes, then heat to the second temperature and keep it for 4-12 minutes, then heat to the third temperature and keep it for 9-25 minutes, and then cool to room temperature. The first temperature is 300-320℃, the second temperature is 700-760℃, and the third temperature is 850-900℃.

4. The sintering method of the hemispherical electrode base according to claim 3, characterized in that: The heating rate from room temperature to the first temperature is 300-320°C / min, the heating rate from the first temperature to the second temperature is 400-420°C / min, and the heating rate from the second temperature to the third temperature is 50-60°C / min.

5. The sintering method of the hemispherical electrode base according to claim 3, characterized in that: The process of cooling to room temperature is as follows: Cool down to 600-620℃ at 50-55℃ / min, then cool down to 400-420℃ at 10-12℃ / min, and then cool naturally to 70-80℃.

6. The sintering method of the hemispherical electrode base according to claim 3, characterized in that: The hemispherical electrode base pre-finished product is sintered in sections under low-pressure Ar gas or vacuum conditions using a high-frequency induction method.

7. A hemispherical electrode base obtained by sintering according to the sintering method according to any one of claims 1 to 6.

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