MEMS electric field sensor, packaging method and packaging equipment

Abstract

The invention provides an MEMS electric field sensor, a packaging method and packaging device.A packaging cover plate and a packaging tube shell are fixed to form a packaging structure to provide space for fixing an electric field sensitive chip, the upper end face of the packaging tube shell is covered with a Kovar welding ring, and the Kovar welding ring covers the packaging tube shell. After a local area of the bottom end surface of the packaging cover plate is sunken towards the top end surface of the packaging cover plate, a positioning bulge and a matching part are formed; after the packaging cover plate is welded and fixed on the top end surface of the packaging tube shell, the positioning bulge is arranged in the space, the side wall surface of the positioning bulge is adjacent to the inner side of the side wall of the packaging tube shell, and the outer wall surface of the packaging cover plate and the outer wall surface of the packaging tube shell are positioned on the same plane; before welding, the packaging cover plate, the packaging tube shell, the electric field sensitive chip and the packaging cavity are preprocessed, so that the interior of the packaging cavity, the packaging cover plate, the packaging tube shell and the material box meet welding conditions. According to the invention, the buckling position of the packaging cover plate can be accurately positioned, the air tightness is improved, and the unattractive seam welding position is avoided.

Description

Technical Field

[0001] The present invention relates to an electric field sensor, in particular to a MEMS electric field sensor, a packaging method and packaging equipment. Background Art

[0002] MEMS electric field sensors are widely used in aerospace, meteorology, electricity, industrial production and many other fields, and play an important role in security and scientific research.

[0003] The packaging process of MEMS electric field sensors is a key technology affecting the practical application of MEMS electric field sensors and has received much attention in recent years.

[0004] like Figure 1 As shown, the patent document with publication number CN119038487A discloses a vacuum packaging device, which includes a packaging cover plate 1, an electric field sensitive chip 2 and a packaging tube shell 3. The packaging cover plate 1 is fastened and fixed to the open end surface of the packaging tube shell 3 through a Kovar welding ring 6 to form a packaging structure for the electric field sensitive chip 2.

[0005] However, since the package cover does not have a positioning structure and the manual positioning accuracy between the package cover and the package tube shell is low, the position of the package cover plate is easily offset during welding, and cannot accurately cover the specified area of ​​the top end face of the package tube shell, making it impossible for the package cover plate to fully cover the top end face of the Kovar welding ring, which not only affects the airtightness, but also causes the seam welding position to be unsightly.

[0006] Therefore, how to accurately fasten the package cover plate to the top of the package tube shell and ensure that the package cover plate covers the top of the Kovar ring when the Kovar ring melts to increase airtightness and avoid unsightly seam welding positions is a technical problem that needs to be solved urgently. Summary of the Invention

[0007] In response to the shortcomings of the above problems, the present invention provides a MEMS electric field sensor, packaging method and packaging equipment that can accurately snap a packaging cover onto the top of a packaging tube shell. After the Kovar ring is melted, the packaging cover is ensured to cover the top of the Kovar ring, thereby increasing airtightness and avoiding unsightly seam welding positions.

[0008] To achieve the above objectives, in a first aspect, the present invention provides a MEMS electric field sensor comprising a package cover, a package shell, and an electric field sensitive chip. The package cover and the package shell, when fixed together, form a package structure for the electric field sensitive chip, providing space for fixing the electric field sensitive chip. The upper end surface of the package shell is covered with a Kovar solder ring. A local area of ​​the bottom end surface of the package cover is recessed toward the top end surface of the package cover to form a positioning protrusion and a mating portion surrounding the positioning protrusion.

[0009] When the package cover is welded and fixed to the top end surface of the package shell, the positioning protrusion is placed inside the space, the side wall of the positioning protrusion is adjacent to the inner side of the side wall of the package shell, and the outer wall of the package cover is in the same plane as the outer wall of the package shell;

[0010] Before welding, the packaging cover plate, the packaging shell, the electric field sensitive chip and the packaging cavity are pre-treated so that the interior of the packaging cavity, the packaging cover plate, the packaging shell and the material box meet welding conditions.

[0011] In one embodiment, the packaging cover plate, the packaging tube shell, the electric field sensitive chip and the packaging cavity are pre-treated so that the water and oxygen content inside the packaging cavity reaches a preset value, the vacuum degree is in a specified micro-negative pressure state, and the moisture and impurities on the packaging cover plate, the packaging tube shell and the material box in the packaging cavity are removed.

[0012] In one embodiment, the device further comprises a plurality of solder joints and a frame-shaped boss, wherein the frame-shaped boss is formed by extending upward from a local area of ​​the inner wall surface of the package tube shell, the frame-shaped boss and the inner wall surface of the package tube shell form a placement groove, a portion of each solder joint is placed inside the frame-shaped boss and the package tube shell, a top end surface of each solder joint is located in the area above the top end surface of the frame-shaped boss and is in the same plane as the top end surface of the electric field sensitive chip, and a bottom end surface of each solder joint is located below the package tube shell;

[0013] After the electric field sensitive chip is fixed in the placement groove, the electric field sensitive chip is connected to the designated soldering point through a lead wire.

[0014] In one embodiment, the device further includes an inner core disposed on the bottom end surface of the positioning protrusion, wherein the inner core includes an inner protrusion end extending downward and adjacent to the electric field sensitive chip;

[0015] Alternatively, the inner core includes an inner convex end extending downward and adjacent to the electric field sensitive chip, and an upper end portion extending upward and penetrating through the interior of the package cover plate and located above the package cover plate.

[0016] In a second aspect, the present invention further provides a packaging method for packaging the above-mentioned MEMS electric field sensor, comprising the following steps:

[0017] After placing a plurality of packaging tube shells with built-in packaging cover plates and fixed electric field sensitive chips in a material box, the material box is placed in the packaging cavity;

[0018] Ensure that the water and oxygen content inside the packaging cavity reaches a preset value and the vacuum degree is at a specified micro-negative pressure state;

[0019] removing moisture and impurities on the packaging cover plate, the packaging tube shell, and the material box in the packaging cavity;

[0020] When welding in the packaging cavity, the packaging cover plate is positioned and covers the top end surface of the packaging tube shell through the positioning protrusion, and the packaging cover plate is pressed. Parallel seam welding is performed between the packaging cover plate and the packaging tube shell. After the Kovar weld ring is melted, the packaging cover plate is fixed to the packaging tube shell. After testing with a fluorine oil helium mass spectrometer leak detector, the MEMS electric field sensors that meet the requirements are put into storage.

[0021] In one embodiment, ensuring that the water and oxygen content inside the packaging cavity reaches a preset value and the vacuum degree is in a specified slightly negative pressure state includes:

[0022] Injecting nitrogen into the packaging cavity and evacuating the interior of the packaging cavity;

[0023] After repeated multiple times, the water and oxygen content inside the packaging cavity reaches a preset value and the vacuum degree is in a specified micro-negative pressure state, wherein the preset value of the water and oxygen content is a water vapor dew point value less than -50°C, the oxygen content is less than 10ppm, and the specified micro-negative pressure state is less than 1 standard atmospheric pressure.

[0024] In one embodiment, removing moisture and impurities on the packaging cover plate, the packaging shell, and the material box in the packaging cavity includes:

[0025] The interior of the packaging cavity is preheated from the current temperature value to the set temperature value according to the preset temperature rise time threshold under a specified slightly negative pressure state, and the set temperature value is maintained for a preset time value.

[0026] In one embodiment, the step of warehousing the MEMS electric field sensors that meet the requirements includes:

[0027] Determining whether the fixed position of the package cover plate on the package shell meets the requirements after welding;

[0028] Determining whether there is a leak at the welding point between the packaging cover plate and the packaging tube shell;

[0029] Test whether the performance of the MEMS electric field sensor meets the packaging requirements.

[0030] In one embodiment, the step of placing a plurality of package shells with built-in package covers and fixed electric field sensitive chips in a material box includes:

[0031] The electric field sensitive chip that meets the preset conditions is superimposed on the bonding area formed on the inner end surface of the package tube shell. After the glue is baked and cured, the electric field sensitive chip is fixed to the central area of ​​the inner end surface of the package tube shell.

[0032] After the electric field sensitive chip is connected to a designated solder joint through a lead, the electrical connection performance between the electric field sensitive chip and the designated solder joint is tested.

[0033] In a third aspect, the present invention further provides a packaging device for implementing the above-mentioned packaging method, comprising at least: a wafer detection device, an ultrasonic cleaning device, an electric field sensitive chip fixing device, a wire bonding device, a pre-treatment device, and a parallel seam welding device, wherein:

[0034] The wafer detection device is used to determine whether the electric field sensitive chip meets the preset conditions according to the preset conditions;

[0035] The ultrasonic cleaning device is used to perform plasma cleaning on the packaging cover plate and the packaging shell;

[0036] The electric field sensitive chip fixing device is used to superimpose the electric field sensitive chip that meets preset conditions on the bonding area formed on the inner end surface of the package tube shell. After the glue is baked and cured, the electric field sensitive chip is fixed to the central area of ​​the inner end surface of the package tube shell.

[0037] The wire bonding device is used to connect the electric field sensitive chip to a designated solder joint via a wire, and to test the connection performance between the package and the designated solder joint;

[0038] The pretreatment device is used to perform a first pretreatment and a second pretreatment to ensure that the water and oxygen content inside the packaging cavity reaches a preset value, the vacuum degree is at a specified slightly negative pressure state, and remove moisture and impurities from the packaging cover plate, the packaging tube shell, and the material box;

[0039] The parallel seam welding device is used to seam weld the packaging cover plate and the packaging shell in the packaging cavity. After the Kovar welding ring is melted, the packaging cover plate is fixed on the packaging shell, and the MEMS electric field sensors that meet the requirements are stored.

[0040] In one embodiment, a preset condition determination device is further included, including:

[0041] A three-axis industrial microscope is used to check the offset and tilt angle of the electric field sensitive chip on the bonding area to ensure that the electric field sensitive chip meets the patch requirements;

[0042] A push-pull force testing machine is used to check whether the fixing performance of the electric field sensitive chip and the connection performance of the lead meet the requirements;

[0043] A frequency sweeping device a, used to test whether the electrical performance between the electric field sensitive chip, the lead and the designated solder joint meets the requirements;

[0044] A visual recognition device, used to determine whether the fixed position of the package cover plate on the package shell meets the requirements after welding;

[0045] A fluorine oil helium mass spectrometer leak detector, used to determine whether there is a leak at the welding point between the packaging cover plate and the packaging tube shell;

[0046] The frequency scanning device b is used to determine whether the performance of the MEMS electric field sensor meets the packaging requirements.

[0047] Compared with the prior art, the present invention has one of the following advantages:

[0048] By adding a positioning protrusion on the bottom end surface of the package cover plate, and making the width of the positioning protrusion close to the width of the open end surface of the package tube shell, it is easy to locate the buckling position of the package cover plate, so that the position of the package cover plate placed on the package tube shell will not be offset. The outer wall surface of the package cover plate and the outer wall surface of the package tube shell are in the same plane. After the Kovar solder ring is melted, it is ensured that the package cover plate covers the top of the Kovar solder ring, thereby ensuring the airtightness of the MEMS electric field sensor after packaging;

[0049] By pre-treating the package cover, package shell, electric field sensitive chip and package cavity, moisture and impurities on the package cover, package shell and electric field sensitive chip can be removed, and the water and oxygen content inside the package cavity can be ensured to reach a preset value and the vacuum degree to be in a specified micro-negative pressure state. After the Kovar solder ring is melted, the package cover is fixed to the package shell, which can ensure the airtightness of the electric field sensor after packaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 It is a cross-sectional view of an existing vacuum packaging device;

[0051] Figure 2 is a cross-sectional view of a first example of a MEMS electric field sensor in the present invention;

[0052] Figure 3 is a cross-sectional view of a second example of the MEMS electric field sensor of the present invention;

[0053] Figure 4 is a flow chart of the packaging method of the present invention;

[0054] Figure 5 This is a schematic diagram of the packaging device in the present invention.

[0055] The main reference numerals are as follows:

[0056] 1-Packaging cover; 100-Positioning protrusion; 101-Mating portion; 2-Electric field sensitive chip; 3-Packaging shell;

[0057] 300-frame-shaped boss; 301-bonding area; 4-lead; 5-solder point; 6-Kovar solder ring; 7-inner core; 8-getter. DETAILED DESCRIPTION

[0058] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0059] In the description of the present invention, it should be understood that the terms "upper", "lower", "top surface", "bottom surface", "inside", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. It should be noted that when a component is considered to be "connected" to another component, it can be directly connected to the other component or there may be a centrally arranged component at the same time. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0060] Example 1

[0061] like Figure 2 As shown, this embodiment provides a MEMS electric field sensor, including a packaging cover plate 1, a packaging tube shell 3 and an electric field sensitive chip 2. The packaging cover plate 1 and the packaging tube shell 3 are fixed to form a packaging structure of the electric field sensitive chip 2 and provide space for fixing the electric field sensitive chip 2. The electric field sensitive chip 2 is fixed inside the packaging tube shell 3.

[0062] The package cover 1 is made of metal material, and the package shell 3 is made of non-metal material, which can be ceramic material, plastic material or other non-metal material.

[0063] Specifically, in the package cover plate 1 , a local area of ​​the bottom end surface thereof is recessed toward the top end surface of the package cover plate 1 , thereby forming a positioning protrusion 100 and a matching portion 101 surrounding the positioning protrusion 100 .

[0064] Furthermore, the thickness of the positioning protrusion 100 is 0.25 mm, and the thickness of the matching portion 101 is 0.1 mm.

[0065] Furthermore, the bottom end surface of the positioning protrusion 100 is a horizontal structure, and an inner core 7 is provided on the bottom end surface of the positioning protrusion 100 , wherein the inner core 7 includes an inner protruding end extending downward and adjacent to the electric field sensitive chip 2 .

[0066] Furthermore, the axis of the inner core 7 and the axis of the positioning protrusion 100 are located on the same longitudinal axis.

[0067] Specifically, the upper end surface of the package case 3 is covered with a Kovar ring 6. After the package cover 1 is snapped onto the top end surface of the package case 3, the positioning protrusion 100 is positioned in the space, with the sidewall of the positioning protrusion 100 adjacent to the inner sidewall of the package case 3, and the bottom end surface of the mating portion 101 superimposed on the top end surface of the Kovar ring 6. When the Kovar ring 6 reaches its melting point and melts, the package cover 1 is snapped onto and fixed to the open end surface of the package case 3, with the outer wall of the package cover 1 and the outer wall of the package case 3 being flush with each other.

[0068] The central area of ​​the inner end surface of the package tube shell 3 is covered with an adhesive area 301. The electric field sensitive chip 2 is superimposed on the adhesive area 301. The electric field sensitive chip 2 is horizontally fixed to the central area of ​​the inner end surface of the package tube shell 3 by the cured adhesive.

[0069] Furthermore, a local area of ​​the inner end surface of the package tube shell 3 extends upward to form a frame-shaped boss 300 , which surrounds the outside of the adhesive and forms a placement area for the electric field sensitive chip 2 between the inner end surface of the package tube shell 3 .

[0070] Furthermore, multiple through-holes are arranged at intervals on the inner end surface of the package tube case 3. Each through-hole extends upward through the interior of the frame-shaped boss 300. The multiple through-holes surround the outside of the bonding area 301, forming a through-hole area. The solder joints 5 sequentially extend through the interior of the through-holes, so that the top end surface of each solder joint 5 is located above the frame-shaped boss 300 and within the space, while the bottom end surface of each solder joint 5 is located below the package tube case 3, capable of connecting to an external circuit board.

[0071] When the top end surfaces of the solder joints 5 are located within the space, the top end surfaces of each solder joint 5 are flush with the top end surface of the electric field sensitive chip 2. The top end surfaces of each designated solder joint 5 are electrically connected to the electric field sensitive chip 2 via leads 4, allowing the electric field sensitive chip 2 to be connected to an external circuit board via leads 4, thereby receiving relevant signals input from the external circuit board or inputting relevant signals to the external circuit board.

[0072] Example 2

[0073] like Figure 3As shown, this embodiment provides a MEMS electric field sensor, the structure of which differs from the MEMS electric field sensor described in the above embodiment 1 in that:

[0074] The inner core 7 includes an inner convex end extending vertically downward and adjacent to the electric field sensitive chip 2 , and an upper end extending vertically upward, penetrating the interior of the package cover plate 1 , and located above the package cover plate 1 .

[0075] In the above-mentioned first and second embodiments, the package cover is made of Kovar alloy material, the package shell is made of 90% alumina composite ceramic material, the Kovar welding ring is 4J29 alloy, and the inner core 7 is made of conductive material.

[0076] In the above-mentioned first and second embodiments, when packaging the MEMS electric field sensor, before welding, a plurality of material boxes with built-in packaging cover plates and packaging tube shells with electric field sensitive chips fixed thereon are placed in the packaging cavity;

[0077] Adjust the water and oxygen content and vacuum degree inside the packaging cavity to the preset value and the specified micro-negative pressure state respectively;

[0078] Remove moisture and impurities from the packaging cover, packaging tube shell and material box in the packaging cavity;

[0079] When welding in the package cavity, the package cover is pressed and parallel seam welding is performed between the package cover and the package shell. After the Kovar weld ring is melted, the package cover is fixed on the package shell.

[0080] In the above-mentioned first and second embodiments, by adding a positioning protrusion on the bottom end surface of the packaging cover plate, and making the width of the positioning protrusion close to the width of the open end surface of the packaging tube shell, it is convenient to locate the snap-fit ​​position of the packaging cover plate, so that the position of the packaging cover plate placed on the packaging tube shell will not be offset, the outer wall surface of the packaging cover plate and the outer wall surface of the packaging tube shell are in the same plane, and after the Kovar solder ring is melted, it is ensured that the packaging cover plate covers the top of the Kovar solder ring, thereby ensuring the airtightness of the MEMS electric field sensor after packaging.

[0081] Example 3

[0082] like Figure 4 As shown, this embodiment provides a packaging method for packaging the MEMS electric field sensor in the above-mentioned embodiment 1 and embodiment 2, comprising the following steps:

[0083] S1, placing a plurality of material boxes with built-in packaging cover plates and packaging tube shells fixed with electric field sensitive chips in a packaging cavity;

[0084] S2. Ensure that the water and oxygen content inside the packaging cavity reaches a preset value and the vacuum degree is at a specified micro-negative pressure state;

[0085] S3, removing moisture and impurities on the packaging cover plate, packaging tube shell and material box in the packaging cavity;

[0086] S4. When welding in the packaging cavity, the packaging cover plate is positioned and covers the top end surface of the packaging tube shell through the positioning protrusion, and the packaging cover plate is pressed. Parallel seam welding is performed between the packaging cover plate and the packaging tube shell. After the Kovar welding ring is melted, the packaging cover plate is fixed on the packaging tube shell.

[0087] Specifically, step S1 includes:

[0088] S101. Use wafer inspection equipment to inspect the electric field sensitive chips to screen out the electric field sensitive chips that do not meet the requirements.

[0089] For example, the wafer inspection equipment inspects the structure of the electric field-sensitive chip according to preset conditions. If there are defects in the comb structure of the electric field-sensitive chip (for example, the spacing between two adjacent comb teeth in the comb structure does not meet the requirements), the current electric field-sensitive chip is determined to be defective and marked to form a mapping diagram. If the current electric field-sensitive chip is determined to be defective, the robotic arm can remove the electric field-sensitive chip that does not meet the preset conditions.

[0090] Since the electric field sensitive chip is very small, the wafer detection equipment can accurately and quickly screen out the electric field sensitive chips that do not meet the requirements, so as to improve the yield rate of the electric field sensor after packaging.

[0091] S102: Clean the package cover plate and the package shell using an ultrasonic cleaning device.

[0092] Furthermore, the packaging cover plate and the packaging tube shell are placed in an ultrasonic cleaning device injected with plasma. Under high temperature and high pressure conditions, the packaging cover plate and the packaging tube shell are cleaned by plasma to remove organic matter on the surface of the packaging cover plate and the packaging tube shell, thereby preventing impurities on the packaging cover plate and the packaging tube shell from affecting the comb-tooth structure in the electric field sensitive chip.

[0093] Furthermore, the impurities on the package cover and the package shell include moisture, dust, particles and organic matter.

[0094] Exemplarily, the cleaning power of the package cover and the package tube shell is 100W-500W, the cleaning time is 2min-10min, the cleaning temperature is 100℃-500℃, the cleaning pressure value is 100-500bar, and the gas in the cleaning process is an argon-oxygen mixed ratio gas, which can reduce the angle of the ceramic water droplet angle.

[0095] S103 , using a glue dispensing structure to dispense glue at a designated position on the inner end surface of the package shell, so as to form a bonding area for the electric field sensitive chip on the package shell.

[0096] The bonding area is located in the central area of ​​the inner end surface of the package shell, and each glue point is preferably a circular glue point with a diameter of 0.1 mm. This regulation can avoid defects caused by glue drawing, glue throwing, and glue overflow, as well as rework leading to reduced efficiency.

[0097] S104: The current electric field sensitive chip that meets the requirements is adsorbed by the wafer inspection equipment and placed on the bonding area.

[0098] Among them, after the electric field sensitive chip is placed on the bonding area, the tilt is within 15um.

[0099] S105. Check the offset and tilt angle of the electric field sensitive chip on the bonding area to ensure that the electric field sensitive chip meets the patch requirements.

[0100] The patch requires that the electric field sensitive chip be located horizontally in the central area of ​​the inner end surface of the package shell.

[0101] S106 , placing the package tube shell with the electric field sensitive chip placed therein into a baking device, and after the glue is baked and solidified, fixing the electric field sensitive chip in the central area inside the package tube shell.

[0102] During baking, the baking temperature and baking time are adjusted according to the heating parameters corresponding to the glue.

[0103] S107. Check the fixing performance of the electric field sensitive chip in the package shell after curing.

[0104] Furthermore, the fixing performance of the electric field sensitive chips in the package can be checked one by one, or the fixing performance of each electric field sensitive chip in each package can be checked simultaneously according to the parameters of the push-pull force testing machine.

[0105] Preferably, a 50 kg pusher is used to perform a thrust test on the fixed electric field sensitive chip to determine whether the fixing performance of the electric field sensitive chip in the package shell meets the national military standard requirements, thereby enhancing reliability.

[0106] S108 , placing the package shell into a wire bonding machine, so that the first end of the lead is connected to the designated welding point, and the second end of the lead is connected to the electric field sensitive chip.

[0107] S109. Test whether the electrical performance between the electric field sensitive chip, leads and designated solder joints meets the requirements.

[0108] Specifically, a sweep frequency test is performed on the electric field sensitive chip, leads, and designated solder joints using a sweep frequency test device a. The resulting sweep frequency curve and test data are used to determine whether the electrical connection performance between the electric field sensitive chip, leads, and designated solder joints meets the requirements, thereby improving the yield rate. If the electrical connection performance between the electric field sensitive chip, leads, and designated solder joints is determined to not meet the requirements, the chip is rejected.

[0109] Specifically, in step S2, it includes:

[0110] S201, injecting nitrogen into the packaging cavity and evacuating the interior of the packaging cavity;

[0111] S202 , after repeating the above steps multiple times, the water and oxygen content inside the packaging cavity reaches a preset value and the vacuum degree is in a specified slightly negative pressure state.

[0112] Among them, the preset value of water oxygen content is that the water vapor dew point value is less than -50°C, the oxygen content is less than 10ppm, and the specified micro-negative pressure state is less than 1 standard atmospheric pressure.

[0113] Preferably, the preset values ​​of the water and oxygen content are a water vapor dew point value of -60°C and an oxygen content of 5 ppm.

[0114] Preferably, the parameters of the external vacuum equipment are set to be less than 50 Pa, and the interior of the closed cavity is vacuumed so that the micro-negative pressure state inside the closed cavity is 0.1-0.5 kPa.

[0115] Furthermore, a nitrogen generator is used to continuously or intermittently inject 99.999% pure nitrogen into the pre-baked packaging cavity. Compared to the existing method of using multiple gas cylinders to inject nitrogen into the packaging cavity, since there is no need to replace gas cylinders, the phenomenon of increased water and oxygen content in the packaging cavity caused by changing gas cylinders can be avoided.

[0116] Specifically, in step S3, the interior of the packaging cavity is preheated from the current temperature value to the set temperature value according to the preset heating time threshold under a specified micro-negative pressure state, and the set temperature value is maintained to the preset time value, wherein the preset heating time threshold is 30 to 45 minutes, the set temperature value is at least 200°C, and the preset time value is at least 120 minutes.

[0117] After step S3 is completed, the temperature of the packaging cavity is cooled to room temperature.

[0118] Furthermore, the time threshold required for the temperature of the packaging cavity to cool down to room temperature is 30 to 45 minutes.

[0119] Specifically, in step S4, it includes:

[0120] S401 , welding the package cover plate to the package shell to fix the package cover plate on the package shell.

[0121] Specifically, when the interior of the packaging cavity is in a specified slightly negative pressure state, the packaging cover plate is positioned and covers the top end surface of the packaging tube shell through the positioning protrusion, the packaging cover plate is pressed by a clamp, and the area between the packaging cover plate and the packaging tube shell is parallel seam welded by a parallel seam welder. After ensuring that the Kovar weld ring is melted, the packaging cover plate is fixed on the packaging tube shell.

[0122] S402, checking whether the fixing position of the package cover plate on the package shell meets the requirements after welding.

[0123] Specifically, the visual recognition device uses a positioning algorithm and PR recognition methods to check the fixed position of the package cover plate on the package tube case after welding, and determines whether the edge end surfaces of the package cover plate and the outer wall surfaces of the package tube case are in the same plane. If they are in the same plane, the package cover plate's position meets the requirements. If not, it indicates that the package cover plate's position does not meet the requirements and needs to be rejected, thereby improving the yield rate.

[0124] S403 , checking whether there are any leaks at the welding point between the package cover plate and the package shell.

[0125] Specifically, a fluorine oil helium mass spectrometer leak detector is used to determine whether there are leaks in the weld between the package cover and the package shell. If there are no leaks, it indicates that the weld between the package cover and the package shell meets the requirements. If there are leaks, it indicates that the weld between the package cover and the package shell does not meet the requirements and needs to be removed to improve the yield rate.

[0126] Furthermore, the welded MEMS electric field sensor is placed in a fluorine oil platform, and the boiling points of light and heavy fluorine oils are used to confirm whether there is a leak at the welding point.

[0127] S404. Test whether the performance of the MEMS electric field sensor meets the packaging requirements.

[0128] Specifically, the welded MEMS electric field sensor is connected to a frequency sweeping device (b). The frequency sweeping device (b) collects and analyzes the MEMS electric field sensor's output signal, generating a frequency sweeping calibration curve and test data. Based on these data, the performance of the MEMS electric field sensor is determined to be satisfactory. If the test data is within a preset threshold range, the MEMS electric field sensor meets the requirements. If the test data is not within the preset threshold range, the MEMS electric field sensor does not meet the requirements and needs to be eliminated, thereby improving the yield rate.

[0129] Optionally, the performance of the MEMS electric field sensor includes, but is not limited to, sensitivity, air pressure value, air tightness, etc. inside the MEMS electric field sensor.

[0130] In the above-mentioned packaging method, by adding the step of pre-treating the packaging cover, packaging tube shell, electric field sensitive chip and packaging cavity, moisture and impurities on the packaging cover, packaging tube shell and electric field sensitive chip can be removed, and the water and oxygen content inside the packaging cavity can be ensured to reach a preset value and the vacuum degree to be in a specified micro-negative pressure state. After the Kovar solder ring is melted, the packaging cover is fixed on the packaging tube shell, which can ensure the airtightness of the electric field sensor after packaging.

[0131] Example 4

[0132] like Figure 5 As shown, this embodiment provides a packaging device for the packaging method described in the above embodiment three, including: a wafer detection device, an ultrasonic cleaning device, a dispensing structure, a patch mechanism, a three-axis industrial microscope, an oven, a push-pull force testing machine, a wire bonding machine, a frequency scanning device a, a pretreatment device, a parallel seam welding machine, a visual recognition device, a fluorine oil helium mass spectrometer leak detector, a frequency scanning device b and a laser coding machine.

[0133] The wafer inspection equipment is used to implement the steps in S101 above, and is used to determine whether the electric field sensitive chip meets the preset conditions according to the preset conditions, and generate a mapping diagram when it is determined that there are defects in the comb structure.

[0134] The ultrasonic cleaning device is used to implement the step in S102 above, performing plasma cleaning on the package cover plate and the package shell to remove organic matter on the surface of the package cover plate and the package shell, and prevent impurities on the package cover plate and the package shell from affecting the comb structure in the electric field sensitive chip.

[0135] The glue dispensing structure is used to implement the step in S103 above, dispensing glue at a designated position on the inner end surface of the package shell, so as to form a bonding area for the electric field sensitive chip on the package shell.

[0136] The patch mechanism is used to implement the steps in the above S104, adsorb the current electric field sensitive chip, and place it on the bonding area.

[0137] The three-axis industrial microscope is used to implement the steps in S105 above to check the offset and tilt angle of the electric field sensitive chip on the bonding area to ensure that the electric field sensitive chip meets the patch requirements.

[0138] The oven is used to implement the step in S106 above to bake the package tube shell in which the electric field sensitive chip is placed. When the glue is cured after baking, the electric field sensitive chip is fixed in the central area inside the package tube shell.

[0139] The push-pull force testing machine is used to implement the steps in S107 above to check the fixing performance of the electric field sensitive chip in the package shell after curing.

[0140] The wire bonding machine is used to implement the steps in S108 above, so that the first end of the lead is connected to the designated welding point, and the second end of the lead is connected to the electric field sensitive chip.

[0141] The frequency scanning device a is used to implement the steps in S109 above to test whether the electrical performance between the electric field sensitive chip, the lead and the designated solder joint meets the requirements.

[0142] The pretreatment device includes a nitrogen machine, a vacuum pump and a heating device, which are used to sequentially implement the steps in S2 and S3 above to pretreat the packaging cavity, the packaging cover, the packaging tube shell and the material box, ensuring that the water and oxygen content inside the packaging cavity reaches a preset value, the vacuum degree is in a specified micro-negative pressure state, and removes moisture and impurities on the packaging cover, the packaging tube shell and the material box.

[0143] The parallel seam welding machine is used to implement the steps in S401 above, performing parallel seam welding between the package cover plate and the package tube shell. After the Kovar weld ring is melted, the package cover plate is fixed on the package tube shell.

[0144] The visual recognition device is used to implement the step in S402 above, and check whether the fixed position of the package cover plate on the package shell meets the requirements after welding.

[0145] The fluorine oil helium mass spectrometer leak detector is used to implement the step in S403 above to check whether there are leaks at the welding point between the packaging cover plate and the packaging tube shell.

[0146] The frequency scanning device b is used to implement the steps in S404 above to test whether the performance of the MEMS electric field sensor meets the packaging requirements.

[0147] The laser coding machine is used to print product information on the MEMS electric field sensor that meets the performance requirements.

[0148] After the product information is printed, the finished product is put into storage.

[0149] In this embodiment, the dispensing structure, the patch mechanism, the three-axis industrial microscope, the oven and the push-pull force tester constitute the electric field sensitive chip fixing device, the wire bonding machine and the frequency scanning device a constitute the wire bonding device, and the pretreatment device, the parallel seam welding machine, the visual recognition device, the fluorine oil helium mass spectrometer leak detector and the frequency scanning device b constitute the parallel seam welding device.

[0150] The above description is merely a preferred embodiment of the present invention and is intended to be illustrative rather than restrictive of the present invention. Those skilled in the art will appreciate that many changes, modifications, and even equivalents may be made to the present invention within the spirit and scope of the claims, all of which fall within the scope of protection of the present invention.

Claims

1. A MEMS electric field sensor, comprising a package cover, a package shell, and an electric field sensitive chip. The package cover and the package shell are fixed together to form a package structure for the electric field sensitive chip, providing space for fixing the electric field sensitive chip. The upper end surface of the package shell is covered with a Kovar solder ring, characterized in that: A local area of ​​the bottom end surface of the packaging cover plate is recessed toward the top end surface of the packaging cover plate to form a positioning protrusion and a matching portion surrounding the positioning protrusion; When the package cover is welded and fixed to the top end surface of the package shell, the positioning protrusion is placed inside the space, the side wall of the positioning protrusion is adjacent to the inner side of the side wall of the package shell, and the outer wall of the package cover is in the same plane as the outer wall of the package shell; Before welding, the packaging cover plate, the packaging shell, the electric field sensitive chip and the packaging cavity are pre-treated so that the interior of the packaging cavity, the packaging cover plate, the packaging shell and the material box meet welding conditions.

2. The MEMS electric field sensor according to claim 1, wherein: The packaging cover plate, the packaging shell, the electric field sensitive chip and the packaging cavity are pretreated so that the water and oxygen content inside the packaging cavity reaches a preset value, the vacuum degree is in a specified micro-negative pressure state, and moisture and impurities on the packaging cover plate, the packaging shell and the material box in the packaging cavity are removed.

3. The MEMS electric field sensor according to claim 2, characterized in that: The package further comprises a plurality of solder joints and a frame-shaped boss, wherein the frame-shaped boss is formed by extending upward from a local area of ​​the inner wall surface of the package shell, the frame-shaped boss and the inner wall surface of the package shell form a placement groove, a portion of each solder joint is placed inside the frame-shaped boss and the package shell, a top end surface of each solder joint is located in the area above the top end surface of the frame-shaped boss and is in the same plane as the top end surface of the electric field sensitive chip, and a bottom end surface of each solder joint is located below the package shell; After the electric field sensitive chip is fixed in the placement groove, the electric field sensitive chip is connected to the designated soldering point through a lead wire.

4. The MEMS electric field sensor according to claim 3, characterized in that: It also includes an inner core disposed on the bottom end surface of the positioning protrusion, wherein the inner core includes an inner protrusion end extending downward and adjacent to the electric field sensitive chip; Alternatively, the inner core includes an inner convex end extending downward and adjacent to the electric field sensitive chip, and an upper end portion extending upward and penetrating through the interior of the package cover plate and located above the package cover plate.

5. A packaging method for packaging the MEMS electric field sensor according to any one of claims 1 to 4, characterized in that: The following steps are involved: After placing a plurality of packaging tube shells with built-in packaging cover plates and fixed electric field sensitive chips in a material box, the material box is placed in the packaging cavity; Ensure that the water and oxygen content inside the packaging cavity reaches a preset value and the vacuum degree is at a specified micro-negative pressure state; removing moisture and impurities on the packaging cover plate, the packaging tube shell, and the material box in the packaging cavity; When welding in the packaging cavity, the packaging cover plate is positioned and covers the top end surface of the packaging tube shell through the positioning protrusion, and the packaging cover plate is pressed. Parallel seam welding is performed between the packaging cover plate and the packaging tube shell. After the Kovar weld ring is melted, the packaging cover plate is fixed to the packaging tube shell. After testing with a fluorine oil helium mass spectrometer leak detector, the MEMS electric field sensors that meet the requirements are put into storage.

6. The packaging method according to claim 5, characterized in that: Ensuring that the water and oxygen content inside the packaging cavity reaches a preset value and the vacuum degree is in a specified slightly negative pressure state includes: Injecting nitrogen into the pre-baked packaging cavity and evacuating the interior of the packaging cavity; After repeated multiple times, the water and oxygen content inside the packaging cavity reaches a preset value and the vacuum degree is in a specified micro-negative pressure state, wherein the preset value of the water and oxygen content is a water vapor dew point value less than -50°C, the oxygen content is less than 10ppm, and the specified micro-negative pressure state is less than 1 standard atmospheric pressure.

7. The packaging method according to claim 6, wherein: The step of removing moisture and impurities on the packaging cover plate, the packaging tube shell, and the material box in the packaging cavity includes: The interior of the packaging cavity is preheated from the current temperature value to the set temperature value according to the preset temperature rise time threshold under a specified slightly negative pressure state, and the set temperature value is maintained for a preset time value.

8. The packaging method according to claim 5, wherein: The step of warehousing the MEMS electric field sensors that meet the requirements includes: Determining whether the fixed position of the package cover plate on the package shell meets the requirements after welding; Determining whether there is a leak at the welding point between the packaging cover plate and the packaging tube shell; Test whether the performance of the MEMS electric field sensor meets the packaging requirements.

9. The packaging method according to any one of claims 5 to 8, characterized in that: The method of placing a plurality of package shells with built-in package covers and fixed electric field sensitive chips in a material box includes: The electric field sensitive chip that meets the preset conditions is superimposed on the bonding area formed on the inner end surface of the package tube shell. After the glue is baked and cured, the electric field sensitive chip is fixed to the central area of ​​the inner end surface of the package tube shell. After the electric field sensitive chip is connected to a designated solder joint through a lead, the electrical connection performance between the electric field sensitive chip and the designated solder joint is tested.

10. A packaging device, characterized in that: The packaging method according to any one of claims 5 to 9 comprises at least: a wafer detection device, an ultrasonic cleaning device, an electric field sensitive chip fixing device, a wire bonding device, a pre-treatment device, and a parallel seam welding device, wherein: The wafer detection device is used to determine whether the electric field sensitive chip meets the preset conditions according to the preset conditions; The ultrasonic cleaning device is used to perform plasma cleaning on the packaging cover plate and the packaging shell; The electric field sensitive chip fixing device is used to superimpose the electric field sensitive chip that meets preset conditions on the bonding area formed on the inner end surface of the package tube shell. After the glue is baked and cured, the electric field sensitive chip is fixed to the central area of ​​the inner end surface of the package tube shell. The wire bonding device is used to connect the electric field sensitive chip to a designated solder joint via a wire, and to test the connection performance between the package and the designated solder joint; The pretreatment device is used to perform a first pretreatment and a second pretreatment to ensure that the water and oxygen content inside the packaging cavity reaches a preset value, the vacuum degree is at a specified slightly negative pressure state, and remove moisture and impurities from the packaging cover plate, the packaging tube shell, and the material box; The parallel seam welding device is used to seam weld the packaging cover plate and the packaging shell in the packaging cavity. After the Kovar welding ring is melted, the packaging cover plate is fixed on the packaging shell, and the MEMS electric field sensors that meet the requirements are stored.

11. The packaging device according to claim 10, wherein: Also included is a preset condition determination device, including: A three-axis industrial microscope is used to check the offset and tilt angle of the electric field sensitive chip on the bonding area to ensure that the electric field sensitive chip meets the patch requirements; A push-pull force testing machine is used to check whether the fixing performance of the electric field sensitive chip and the connection performance of the lead meet the requirements; A frequency sweeping device a, used to test whether the electrical performance between the electric field sensitive chip, the lead and the designated solder joint meets the requirements; A visual recognition device, used to determine whether the fixed position of the package cover plate on the package shell meets the requirements after welding; A fluorine oil helium mass spectrometer leak detector, used to determine whether there is a leak at the welding point between the packaging cover plate and the packaging tube shell; The frequency scanning device b is used to determine whether the performance of the MEMS electric field sensor meets the packaging requirements.

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