Hemispherical electrode base and sintering method thereof

Abstract

The invention discloses a hemispherical electrode base and a sintering method thereof, and the method comprises the following steps: a plurality of glass electrode assemblies are prepared, the plurality of glass electrode assemblies are in one-to-one correspondence with a plurality of electrode holes of the hemispherical electrode base, and each glass electrode assembly comprises an electrode needle and a glass column coaxially fixed on the electrode needle, the glass column is matched with an electrode hole in the semispherical electrode base, the glass electrode assembly is arranged in the corresponding electrode hole of the semispherical electrode base in a penetrating mode, the oxygen-free copper pipe is arranged in a center hole of the semispherical electrode base, brazing filler metal is arranged between the oxygen-free copper pipe and the hole wall of the center hole, and a semispherical electrode base pre-finished product is obtained; performing segmented sintering on the semi-spherical electrode base pre-finished product to obtain a semi-spherical electrode base; according to the method, glass insulation sealing sintering between the metal electrode and the metal base and brazing sintering between the oxygen-free copper pipe and the metal base can be completed through one-step sintering, the technological process is shortened, the cost is reduced, and meanwhile the yield is increased.

Description

Technical Field

[0001] The 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 hemispherical resonant gyroscope is a solid wave gyroscope based on the Coriolis effect. It has the advantages of high precision, long life and high reliability, and is an important direction for the future development of gyroscopes. The future application directions of the hemispherical resonant gyroscope include many fields such as aerospace and navigation. As a key part of the hemispherical resonant gyroscope, the high Q value of the resonator is an important indicator for judging the quality of the resonator, and it also affects the performance of the hemispherical resonant gyroscope. The hemispherical resonant gyroscope works in a vacuum environment, which is one of the core conditions for achieving its high precision and long life. The vacuum environment can significantly reduce the loss of air damping to the vibration energy of the resonator. In addition, the vacuum can suppress the interference of vibration modes. The collision of molecules in the air will introduce random noise, which will destroy the stability of the four-antinode vibration 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] Based on this, in order to achieve better airtightness, the preparation process of the electrode base is extremely important. However, due to the inconsistency between the sintering temperatures of glass sintering and metal brazing, if the glass sintering temperature is too high, it will seriously affect the metal brazing effect. Therefore, it is impossible to complete the sealing connection between the electrode needle and the oxygen-free copper tube and the base at the same time through one process. The traditional electrode base sintering process adopts a two-step sintering method. First, the glass powder, electrode and electrode base are sintered at high temperature (1000℃ atmosphere), and then the exhaust copper tube is vacuum brazed (850℃ atmosphere). In addition, the glass powder needs to be mixed with an organic adhesive first, preformed by a traditional press, and debonded by high-temperature sintering to obtain sintered glass particles. After the glass particles and the metal electrode needle are assembled together, they are assembled on the electrode base, and then high-temperature co-firing is performed to obtain a sintered electrode-base product. It can be seen that the traditional base preparation process is relatively cumbersome, and the multiple sintering steps can easily cause poor airtightness of the meter head, affecting the performance and service life of the hemispherical resonant 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, and 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: A sintering method for a hemispherical electrode base, comprising the following steps: Prepare a plurality of glass electrode assemblies, which correspond one by one to a plurality of electrode holes of the hemispherical electrode base. The glass electrode assembly includes an electrode pin and a glass column coaxially fixed on the electrode pin. The glass column matches the electrode hole on the hemispherical electrode base. Insert the glass electrode assembly into the corresponding electrode hole of the hemispherical electrode base, and place an oxygen-free copper tube in the central hole of the hemispherical electrode base. A brazing filler metal is arranged between the oxygen-free copper tube and the hole wall of the central hole to obtain a preform of the hemispherical electrode base. Perform segmented sintering on the preform of the hemispherical electrode base 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.

[0007] Optionally, the preparation process of the glass electrode assembly is as follows: Mix the raw materials for preparing the glass column, melt at 1400 - 1450 °C, keep warm for 1.5 - 2.5 h, cool and then ball mill into powder, and pass through a 250 - 350 mesh sieve to obtain composite glass powder. Pre-press the composite glass powder on the electrode pin to form a glass electrode assembly.

[0008] Optionally, the process of pre-pressing and forming is as follows: Mix the composite glass powder and water in a mass ratio of 10:1 to obtain a glass slurry. Place the electrode pin in a mold, inject 0.4 - 0.6 g of the glass slurry, pre-press and form for 5 - 10 s under a pressure of 100 Kg, demold, and dry to obtain the glass electrode assembly.

[0009] Optionally, the process of segmented sintering is as follows: First, heat up to a first temperature and keep warm for 4 - 6 min, then heat up to a second temperature and keep warm for 4 - 12 min, then heat up to a third temperature and keep warm for 9 - 25 min, and then cool down to room temperature. The first temperature is 300 - 320 °C, the second temperature is 700 - 760 °C, and the third temperature is 850 - 900 °C.

[0010] 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.

[0011] Optionally, the process of cooling down to room temperature is as follows: Cool down to 600 - 620°C at a rate of 50 - 55°C / min, then cool down to 400 - 420°C at a rate of 10 - 12°C / min, and then cool naturally to 70 - 80°C.

[0012] Optionally, the pre - finished product of the hemispherical electrode base is sintered in segments by high - frequency induction under low - pressure Ar gas or vacuum conditions.

[0013] As a general inventive concept, the present invention also provides a hemispherical electrode base sintered by the above - mentioned sintering method.

[0014] Compared with the prior art, the advantages of the present invention are as follows: By designing glass powder that can be sintered by medium - temperature melting, it can be normally melted and sintered 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 sintering. Compared with the traditional two - step sintering, the process flow is shortened, the cost is reduced, and the yield rate is improved. Moreover, its viscosity after melting is appropriate, and it can flow into and fill between the electrode pin and the pore wall of the electrode hole of the electrode base but does not drip after medium - temperature melting, so that the electrode pin and the electrode base can be well sealed and connected after cooling. In addition, the thermal expansion coefficient of this glass powder matches that of common electrode base materials, and no cracks are generated at the interface fusion.

[0015] Practice shows that the medium - temperature glass powder has better thermal shock resistance. After 50 rounds of thermal shock cycle tests (-40~80°C), both the leak rate and short - circuit tests are normal. Therefore, this medium - temperature glass powder can adapt to the extreme application environment of the hemispherical resonator gyro to ensure the long - term use of the hemispherical resonator gyro head in a high - vacuum environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] To understand the present invention more easily, the present invention will be described in more detail by referring to the specific embodiments shown in the drawings. These drawings only depict the typical embodiments of the present invention and should not be considered as limiting the protection scope of the present invention.

[0017] Figure 1 It is a flowchart of the sintering method of the hemispherical electrode base according to the embodiment of the present invention.

[0018] Figure 2 It is a schematic three - dimensional structure diagram of the pre - finished product of the hemispherical electrode base according to the embodiment of the present invention.

[0019] Figure 3 It is an exploded structure diagram of the pre - finished product of the hemispherical electrode base according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] The embodiments of the present invention will be described below with reference to the accompanying drawings so that those skilled in the art can better understand the present invention and implement it. However, the listed embodiments are not intended to limit the present invention. Without conflict, the following embodiments and the technical features in the embodiments can be combined with each other, and the same components are denoted by the same reference numerals.

[0021] As Figure 1 shown, the present invention provides a sintering method for a hemispherical electrode base, comprising the following steps: As Figure 2 and Figure 3 shown, a plurality of glass electrode assemblies 2 are prepared. The plurality of glass electrode assemblies 2 correspond to a plurality of electrode holes 12 of the hemispherical electrode base 1 one by one. The glass electrode assembly 2 includes an electrode pin 21 and a glass column 22 coaxially fixed on the electrode pin 21. The glass column 22 matches the electrode hole 12 on the hemispherical electrode base 1. The glass electrode assembly 2 is inserted into the corresponding electrode hole 12 of the hemispherical electrode base 1, and an oxygen-free copper tube 3 is placed in the central hole 11 of the hemispherical electrode base 1. A brazing filler metal is provided between the oxygen-free copper tube 3 and the wall of the central hole 11 to obtain a preform of the hemispherical electrode base. The preform of the hemispherical electrode base is sintered 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.

[0022] The present invention designs a glass powder that can be melted and sintered at medium temperature and can be normally melted and sintered at the brazing temperature. Thus, the glass insulation seal 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 sintering. Compared with the traditional two-step sintering, the process flow is shortened, the cost is reduced, and the yield rate is improved. Moreover, its viscosity after melting is appropriate, and it can flow into and fill between the electrode pin and the wall of the electrode hole of the electrode base but does not drip after being melted at medium temperature. Thus, the electrode pin and the electrode base can be well sealed and connected after cooling. In addition, the thermal expansion coefficient of the glass powder matches that of the common electrode base material, and no cracks are generated at the interface fusion.

[0023] Practice shows that the medium-temperature glass powder has better thermal shock resistance. After 50 rounds of thermal shock cycle tests (-40~80°C), the leak rate and short-circuit tests are both normal. Thus, the medium-temperature glass powder can adapt to the extreme application environment of the hemispherical resonator gyro to ensure the long-term use of the hemispherical resonator gyroscope head in a high-vacuum environment.

[0024] Specifically, the preparation process of the glass electrode assembly is as follows: Mix the raw materials for preparing the glass column, melt them at 1400 - 1450 °C, hold for 1.5 - 2.5 h, ball mill them into powder after cooling, and pass through a 250 - 350 mesh sieve to obtain the composite glass powder. Pre-press the composite glass powder onto the electrode needle to form the glass electrode assembly.

[0025] Specifically, the process of pre-pressing and forming is as follows: Mix the composite glass powder and water in a mass ratio of 10:1 to obtain the glass powder. Place the electrode needle in the mold, inject 0.4 - 0.6 g of the glass powder, pre-press and form it under a pressure of 100 Kg for 5 - 10 s, demold, and dry to obtain the glass electrode assembly.

[0026] Specifically, the process of segmented sintering is as follows: First, heat up to the first temperature and hold for 4 - 6 min, then heat up to the second temperature and hold for 4 - 12 min, then heat up to the third temperature and hold for 9 - 25 min, and then cool down to room temperature. The first temperature is 300 - 320 °C, the second temperature is 700 - 760 °C, and the third temperature is 850 - 900 °C.

[0027] By designing the above-specified sintering curve, the heat preservation at each temperature segment corresponds to the drainage process (300 - 320 °C), the sintering exhaust process (700 - 760 °C), and the glass powder melting + brazing solder melting process (850 - 900 °C) respectively, meeting the heat preservation requirements for the normal exhaust, melting sintering, and metal brazing processes during the glass powder sintering cycle, ensuring that the solder and glass powder can be fully melted and can fully infiltrate the material surface, and improving the overall vacuum performance of the product.

[0028] 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.

[0029] Specifically, the process of cooling down to room temperature is as follows: Cool down at a rate of 50 - 55 °C / min to 600 - 620 °C, then cool down at a rate of 10 - 12 °C / min to 400 - 420 °C, and then cool naturally to 70 - 80 °C.

[0030] The cooling process is fast first and then slow, which can ensure the normal release of stress during the cooling process of the glass material and the metal material.

[0031] Specifically, the semi-spherical electrode base preform is segmented and sintered by high-frequency induction and under low-pressure Ar gas or vacuum conditions.

[0032] Adopt a sintering environment of controllable high-frequency induction heating + low-pressure Ar gas (or vacuum), which has a controllable heating rate for metals, and common metals can all be processed by this method. At the same time, in a low-pressure Ar gas (vacuum) environment, it can prevent product oxidation and quickly release the gases generated during the product sintering process.

[0033] Example 1 (Sintering process of 304 stainless steel substrate) 1) Prepare a glass powder product that meets the temperature and thermal expansion requirements. Weigh the following raw materials according to the mass percentage: quartz powder 25%, alumina powder 5%, boric acid 30%, sodium carbonate 20%, potassium carbonate 5%, calcium carbonate 7%, lithium carbonate 3%, zinc oxide 5%, totaling 100%. Mix the weighed raw materials, melt them at 1400 °C, keep them warm for 2 h, put the glass liquid into cold water for cooling, and then ball-mill and powder the cooled glass material, and pass it through a 300-mesh sieve to obtain glass powder with a suitable particle size for standby. 2) First, place the hemispherical electrode base 1 on a non-metallic mold, then place the pre-formed glass electrode assembly 2 into the corresponding electrode holes 12 of the hemispherical electrode base 1, and place the pre-made oxygen-free copper tube 1 and silver solder at the center hole 11.

[0034] 3) Place the sample to be sintered into a high-frequency induction atmosphere furnace, set a specific temperature curve. The heating rate from 0 to 300 °C is 300 °C / min, keep it warm at 300 °C for 5 min, the heating rate from 300 to 700 °C is 400 °C / min, keep it warm at 700 °C for 5 min, the heating rate from 700 to 850 °C is 50 °C / min, keep it warm at 850 °C for 10 min, the cooling rate from 850 to 600 °C is 50 °C / min, the cooling rate from 600 to 400 °C is 10 °C / min, and natural cooling from 400 to 80 °C. The heat preservation at each temperature section corresponds to the drainage process (at 300 °C), the sintering exhaust process (at 700 °C), and the glass powder melting and solder melting process (at 850 °C). The cooling process is fast first and then slow to ensure the normal release of stress during the cooling process of the glass material and the metal material. Finally, take out the sample when the sample temperature drops to 80 °C.

[0035] 4) Conduct sample performance testing: Conduct 50 rounds of thermal shock cycle testing (-40 - 80 °C), test the leak rate (<1×10 - 11 Pa·m 3 / s) with a helium mass spectrometer leak detector and conduct a short-circuit test with a multimeter to determine the results, as shown in Table 1.

[0036] Table 1

[0037] Example 2 (Glass powder for kovar substrate) 1) Prepare glass powder products that meet the temperature and thermal expansion requirements, mix the following raw materials according to mass percentage: quartz powder 30%, alumina powder 5%, boric acid 28%, sodium carbonate 10%, potassium carbonate 5%, calcium carbonate 7%, lithium carbonate 10%, zinc oxide 5%, totaling 100%, mix the weighed raw materials, melt at 1450°C, keep warm for 2 hours, cool the glass liquid in cold water, ball-mill the cooled glass material, and pass it through a 300-mesh sieve to obtain glass powder of suitable particle size for later use; 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 at the center hole 11.

[0038] 3) Place the sample to be sintered in a high-frequency induction atmosphere furnace and set a specific temperature curve: 0-300℃ heating rate 300℃ / min, 300℃ insulation for 5min, 300-750℃ heating rate 400℃ / min, 750℃ insulation for 10min, 750-850℃ heating rate 50℃ / min, 850℃ insulation for 20min, 850-600℃ cooling rate 50℃ / min, 600-400℃ cooling rate 10℃ / min, 400-80℃ natural cooling. The insulation of each temperature section corresponds to the (300℃) drainage process, (750℃) sintering exhaust process, and (850℃) glass powder melting and solder melting process. 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 sample temperature drops to 80℃.

[0039] 4) Conduct sample performance testing: 50 rounds of thermal shock cycle test (-40-80℃) were carried out, and the leakage rate was tested by helium mass spectrometer leak detector (<1×10 - 11 Pa·m 3 / s) and a multimeter to perform a short-circuit test, as shown in Table 2.

[0040] Table 2

[0041] Through experimental verification of the comparison of two metal substrate processes, a specific glass powder formula and a customized temperature curve are used to simultaneously meet the glass sealing sintering and metal brazing processes. Compared with the two-step sintering method, it has obvious advantages and product yield.

[0042] The above-described embodiments are merely more preferred specific embodiments of the present invention. This specification uses the phrases "in one embodiment", "in another embodiment", "in yet another embodiment", or "in other embodiments", which may each refer to one or more of the same or different embodiments according to the present disclosure. Ordinary variations and substitutions made by those skilled in the art within the scope of the technical solution of the present invention should be included within the protection scope of the present invention.

Claims

1. A sintering method for a hemispherical electrode base, characterized in that, It includes the following steps: Prepare a plurality of glass electrode assemblies, which correspond to a plurality of electrode holes of the hemispherical electrode base one by one. The glass electrode assembly includes an electrode needle and a glass column coaxially fixed on the electrode needle. The glass column matches the electrode hole on the hemispherical electrode base. Insert the glass electrode assembly into the corresponding electrode hole of the hemispherical electrode base, and place an oxygen-free copper tube in the central hole of the hemispherical electrode base. A brazing filler metal is arranged between the oxygen-free copper tube and the hole wall of the central hole to obtain a preform of the hemispherical electrode base. Perform segmented sintering on the preform of the hemispherical electrode base 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.

2. The sintering method of the hemispherical electrode base according to claim 1, characterized in that The preparation process of the glass electrode assembly is as follows: Mix the raw materials for preparing the glass column, melt at 1400-1450°C, hold for 1.5-2.5h, cool and then ball mill into powder, and pass through a 250-350 mesh sieve to obtain composite glass powder. Pre-press the composite glass powder on the electrode needle to form a glass electrode assembly.

3. The sintering method of the hemispherical electrode base according to claim 2, characterized in that, The process of pre-pressing and forming is as follows: Mix the composite glass powder and water in a mass ratio of 10:1 to obtain a glass slurry. Place the electrode needle in a mold, inject 0.4-0.6g of the glass slurry, pre-press and form for 5-10s under a pressure of 100Kg, demold, and dry to obtain the glass electrode assembly.

4. The sintering method of the hemispherical electrode base according to any one of claims 1-3, characterized in that The process of segmented sintering is as follows: First, heat up to the first temperature and hold for 4-6min, then heat up to the second temperature and hold for 4-12min, then heat up to the third temperature and hold for 9-25min, and then cool down to room temperature. The first temperature is 300-320°C, the second temperature is 700-760°C, and the third temperature is 850-900°C.

5. The sintering method of the hemispherical electrode base according to claim 4, 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.

6. The sintering method of the hemispherical electrode base according to claim 4, characterized in that, The process of cooling down to room temperature is as follows: Cool down at 50-55°C / min to 600-620°C, then cool down at 10-12°C / min to 400-420°C, and then naturally cool to 70-80°C.

7. The sintering method of the hemispherical electrode base according to claim 4, characterized in that, Perform segmented sintering on the preform of the hemispherical electrode base by high-frequency induction and under low-pressure Ar gas or vacuum conditions.

8. A hemispherical electrode base sintered by the sintering method according to any one of claims 1-7.

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