Differential pressure sensor sensitive structure and packaging method

Abstract

The invention relates to the technical field of pressure sensors, and provides a differential pressure sensor sensitive structure and a packaging method, and the packaging method comprises the following steps: preparing a screen printing plate; printing glass slurry on the lower substrate layer wafer; printing glass slurry on the upper substrate layer wafer; the printed lower substrate layer wafer and the printed upper substrate layer wafer are placed in a drying oven to be subjected to glue discharging and pre-sintering; the lower substrate layer wafer and the pressure sensing film layer wafer are pre-fixed after being aligned; aligning the upper substrate layer wafer with the fixed lower substrate layer wafer and the pressure sensing film layer and then pre-fixing the upper substrate layer wafer and the fixed lower substrate layer wafer and the pressure sensing film layer; putting the three layers of pre-fixed wafer combinations into a variable-load muffle furnace, and applying a pre-load for sintering; cutting up the three layers of wafers to form a naked DIE of the MEMS header; and mounting an ASIC bare DIE, and interconnecting each electrode with the ASIC chip to complete electrical connection. The packaging precision, the structural stability, the electrical performance and the production efficiency of the differential pressure sensor sensitive structure are improved, and meanwhile the production cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of pressure sensors, and in particular to a sensitive structure and packaging method of a differential pressure sensor. Background Art

[0002] As a high-precision MEMS pressure sensor, quartz pressure sensor has the advantages of small size, low power consumption, high precision and small temperature drift coefficient.

[0003] The quartz capacitance differential pressure sensor is based on the differential capacitance principle. The quartz base film is used as the pressure sensing element. The two sides of the quartz base film sense the two-way pressure input from the outside world. When the two-way pressure changes, the pressure sensing film is strained, which causes the differential capacitance formed by the pressure sensing film and the upper and lower electrodes to change, thereby realizing pressure measurement. The quartz capacitance differential pressure meter head is integrated with the ASIC conditioning chip at the chip level, directly outputs digital signals, is compatible with high-speed digital circuits, and can effectively suppress common mode errors. In view of the urgent need for high-precision differential pressure sensors in the field of high-precision atmospheric data systems and industrial flow control, a quartz capacitance pressure sensor based on the differential capacitance principle is proposed. Compared with metal capacitors, ceramic capacitors and silicon capacitors, it has the advantages of small size and high integration. By designing the pressure sensitive structure of the differential capacitance structure, high-precision differential pressure measurement is realized. The differential capacitance gap is accurately controlled by the anchor point limit boss, thereby realizing accurate control of the nominal capacitance. It has the advantages of low power consumption and strong anti-interference ability, and has become the development trend of high-precision differential pressure sensors in the future. The quartz capacitance differential pressure sensor has a range of +-1kPa~+-50MPa, and a comprehensive accuracy of 0.075%FS at full temperature. It can measure gas and liquid pressure.

[0004] In the relevant technical field, the existing high-precision differential pressure sensor sensitive structures mostly use traditional precision machining and ultra-high precision assembly, involving many parts and components of different materials, with extremely high requirements on the processing progress of the parts. The assembly process is too complicated, especially the upper electrode, pressure-sensitive membrane and lower electrode. The processing accuracy requirements are high, and high-precision alignment assembly is required, which has low efficiency and thus affects production capacity. Summary of the invention

[0005] The present invention provides a differential pressure sensor sensitive structure and packaging method, which are used to solve the defects in the prior art that the assembly process of the existing high-precision differential pressure sensor sensitive structure is too complicated and inefficient, affecting the production capacity, thereby improving the packaging accuracy, structural stability, electrical performance and production efficiency of the differential pressure sensor sensitive structure, while reducing the production cost.

[0006] The present invention provides a method for packaging a sensitive structure of a differential pressure sensor, comprising the following steps: preparing a screen printing plate including a screen printing mark, a wafer-level alignment mark and a slurry unit; Processing a screen printing mark and a wafer-level alignment mark on the lower base layer wafer, aligning the screen printing plate with the lower base layer wafer, and printing glass paste on the lower base layer wafer; Processing a screen printing mark and a wafer-level alignment mark on the upper substrate layer wafer, aligning the screen printing plate with the upper substrate layer wafer, and printing glass paste on the upper substrate layer wafer; The printed lower substrate layer wafer and upper substrate layer wafer are placed in an oven to perform binder removal and pre-burning according to a set temperature curve; Aligning the lower substrate layer wafer and the pressure-sensitive film layer wafer and performing pre-fixation; The upper substrate layer wafer is aligned with the fixed lower substrate layer wafer and the pressure-sensitive film layer and then pre-fixed; The three-layer pre-fixed wafer assembly is placed in a variable load muffle furnace, a preload is applied, sintering is performed according to a set temperature curve and a heat preservation curve, and the furnace is cooled; The cooled three-layer wafer is cut to form a bare DIE for the MEMS header; Apply epoxy glue on the upper surface of the MEMS head, mount the ASIC bare DIE, and perform thermal curing; Through the gold wire bonding process, each electrode is interconnected with the ASIC chip to complete the electrical connection.

[0007] According to a differential pressure sensor sensitive structure packaging method provided by the present invention, when preparing the silk screen printing stencil, it also includes: Determine the thickness of the photosensitive resin of the screen printing plate, the material of the screen frame, the type of the screen and the mesh count of the screen.

[0008] According to a differential pressure sensor sensitive structure packaging method provided by the present invention, before the lower base layer wafer or the lower base layer wafer is printed, it also includes: Prepare glass slurry, and set the viscosity, mesh size, sintering temperature and sintering time of the glass slurry.

[0009] According to a differential pressure sensor sensitive structure packaging method provided by the present invention, the screen printing plate and the lower substrate wafer are aligned through CCD; And / or, the screen printing plate and the upper substrate wafer are aligned via a CCD.

[0010] According to a differential pressure sensor sensitive structure packaging method provided by the present invention, the debinding and pre-burning include: Starting from room temperature, heat up to 150 degrees at a rate of 5 degrees / minute, keep warm for 15 to 30 minutes, and discharge the organic solvent; heat up to 200 degrees, keep warm for 30 minutes, and discharge the organic binder; heat up to 250 degrees, keep warm for 15 to 30 minutes, activate the thixotropic agent of the slurry; heat up to 300 degrees, keep warm for 15 to 30 minutes, and achieve crystallization of the glass slurry; heat up to 350 degrees, keep warm for 15 to 30 minutes, and achieve melting and sintering of the glass slurry to form a ceramic glass base layer, and then cool to room temperature with the furnace before taking out the wafer.

[0011] According to a differential pressure sensor sensitive structure packaging method provided by the present invention, when printing the glass paste on the lower base layer or the upper base layer, the printing width of the glass paste is 400um~500um, the printing thickness of the glass paste is 25um~30um, and the wafer after printing is left to stand for 3~5 minutes.

[0012] According to a differential pressure sensor sensitive structure packaging method provided by the present invention, the sintering comprises: Starting from room temperature, the heating rate is 5 degrees / minute, the temperature is raised to 520 degrees, the insulation time is 15 to 30 minutes, and the load pressure at the insulation point is 150kg to 250kg. After the insulation is completed, the three layers of wafers are cooled with the furnace. When the temperature drops to 250 to 260 degrees, the load is unloaded. When the temperature drops to 150 degrees, the furnace door is opened and quickly cooled to room temperature.

[0013] According to a differential pressure sensor sensitive structure packaging method provided by the present invention, the thermal curing comprises: Starting from room temperature, the heating rate is 5 degrees / minute, the curing temperature is 80 degrees ~ 120 degrees, the curing time is 15 minutes ~ 30 minutes, and then cooled in the furnace.

[0014] According to a method for packaging a sensitive structure of a differential pressure sensor provided by the present invention, the outer peripheral edge of the upper substrate layer facing the pressure-sensitive film is provided with a plurality of upper limit bosses, and the plurality of upper limit bosses are evenly arranged along the peripheral side of the pressure-sensitive film; And / or, a plurality of lower limit bosses are protruding from the outer peripheral edge of one side of the lower base layer facing the pressure-sensitive film, and the plurality of lower limit bosses are evenly arranged along the peripheral side of the pressure-sensitive film.

[0015] The present invention also provides a differential pressure sensor sensitive structure, which is packaged using the above-mentioned differential pressure sensor sensitive structure packaging method. The differential pressure sensor sensitive structure includes an ASIC chip, an upper base layer, a lower base layer and a pressure-sensitive film. The upper base layer and the lower base layer are arranged opposite to each other and at intervals. The ASIC chip is arranged on the side of the upper base layer away from the lower base layer. The pressure-sensitive film is arranged between the upper base layer and the lower base layer. The upper base layer, the pressure-sensitive film and the lower base layer are bonded and connected by glass paste.

[0016] The differential pressure sensor sensitive structure packaging method provided by the present invention ensures high-precision alignment between the lower substrate layer, the pressure-sensitive film layer and the upper substrate layer through the use of screen printing marks and wafer-level alignment marks. It can significantly improve the yield rate, reduce waste caused by misalignment, and ensure the consistency and reliability of the sensor. By printing glass slurry on the lower substrate layer and the upper substrate layer using screen printing technology, the thickness of the slurry can be evenly controlled, which helps to form a uniform glass substrate layer, thereby improving the performance stability of the product. Through the set temperature curve, the debinding and pre-burning can effectively remove the organic components in the slurry, prevent the generation of bubbles or cracks in the subsequent sintering process, and improve the quality of the finished product. The sintering process carried out in the variable load muffle furnace can ensure good combination between the three-layer structure and form a strong and reliable connection through precise control of the temperature curve and the holding time, plus appropriate preload. The electrodes are interconnected with the ASIC chip through the gold wire bonding technology, which ensures the reliability and efficiency of signal transmission and also enhances the durability of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 The invention provides a screen-printed wafer for packaging a sensitive structure of a differential pressure sensor.

[0019] Figure 2 yes Figure 1 Schematic diagram of the structure of the screen printing alignment mark.

[0020] Figure 3 yes Figure 1 Schematic diagram of the structure of the wafer-level alignment mark.

[0021] Figure 4 yes Figure 1 Schematic diagram of the structure of the medium unit slurry ring.

[0022] Figure 5 Schematic diagram of screen printing of the lower substrate layer.

[0023] Figure 6 Schematic diagram of screen printing of the upper substrate layer.

[0024] Figure 7 It is a schematic diagram of wafer-level alignment and pre-fixation of the lower substrate layer and the pressure-sensitive film.

[0025] Figure 8 It is a schematic diagram of the alignment and pre-fixation of the upper base layer and the combined sheet.

[0026] Fig. 9 It is a schematic diagram of the sintering of three-layer structure wafer-level glass paste.

[0027] Fig.10 It is a schematic diagram of chip mounting and gold wire bonding after wafer dicing.

[0028] Fig.11 It is an assembly cross-sectional view of the sensitive structure of the differential pressure sensor provided by the present invention.

[0029] Reference numerals: 10. Sensitive structure of differential pressure sensor; 100. ASIC conditioning chip; 200, upper substrate layer; 210, feeding ring; 220, upper limit boss; 230, upper air guide hole; 240, upper electrode; 250, gold wire bonding window; 260, upper electrode pad; 300, first chamber; 310, upper capacitor Ct; 400, pressure-sensitive film; 410, first isolation groove; 420, second isolation groove; 430, first electrode pad; 440, second electrode pad; 450, coating side edge; 460, first electrode; 470, second electrode; 480, gold wire bonding window; 500, second chamber; 510, lower capacitor Cb; 600, lower base layer; 610, blanking ring; 620, lower limit boss; 630, lower air guide hole; 640, lower electrode; 650, lower electrode pad; 700, applying a glass slurry layer; 800, lower glass slurry layer; 900, Bonding Gold Wire; 20. Quartz wafer; 30. Screen printing benchmarking; 40. Unit slurry ring; 50. Wafer level alignment mark; 60. UV glue; 70. Epoxy glue. DETAILED DESCRIPTION

[0030] The following embodiments of the present invention are described in further detail in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0031] In the description of the embodiments of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limitations on the embodiments of the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0032] In the description of the embodiments of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific circumstances.

[0033] In the embodiments of the present invention, unless otherwise clearly specified and limited, the first feature being "above" or "below" the second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature being "above", "above" and "above" the second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. The first feature being "below", "below" and "below" the second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0034] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiments of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0035] Combine the following Figures 1 to 11, the packaging method of the differential pressure sensor sensitive structure 10 and the differential pressure sensor sensitive structure 10 provided in the embodiment of the present invention are described in detail through specific embodiments and their application scenarios.

[0036] The packaging method of the differential pressure sensor sensitive structure 10 provided by the present invention is described below. Figures 1 to 10 The packaging method of the differential pressure sensor sensitive structure 10 includes: preparing a screen printing plate including a screen printing mark, a wafer-level alignment mark 50 and a slurry unit; processing the screen printing mark and the wafer-level alignment mark 50 on the lower substrate layer 600 wafer, aligning the screen printing plate with the lower substrate layer 600 wafer, and printing glass slurry on the lower substrate layer 600 wafer; processing the screen printing mark and the wafer-level alignment mark 50 on the upper substrate layer 200 wafer, aligning the screen printing plate with the upper substrate layer 200 wafer, and printing glass slurry on the upper substrate layer 200 wafer; placing the printed lower substrate layer 600 wafer and the upper substrate layer 200 wafer in an oven, and performing the drying process according to a set temperature curve. Debonding and pre-burning are performed; the lower substrate layer 600 wafer is aligned with the pressure-sensitive film 400 layer wafer and then pre-fixed; the upper substrate layer 200 wafer is aligned with the fixed lower substrate layer 600 wafer and the pressure-sensitive film 400 layer and then pre-fixed; the three-layer pre-fixed wafer combination is placed in a variable load muffle furnace, a preload is applied, sintering is performed according to the set temperature curve and insulation curve, and cooling is performed with the furnace; the cooled three-layer wafer is cut to form a MEMS header bare DIE; epoxy glue 70 is applied on the upper surface of the MEMS header, the ASIC bare DIE is mounted, and thermal curing is performed; each electrode is interconnected with the ASIC chip through a gold wire bonding process to complete the electrical connection.

[0037] The present application ensures high-precision alignment between the lower substrate layer 600, the pressure-sensitive film 400 layer and the upper substrate layer 200 by using screen printing marks and wafer-level alignment marks 50. It can significantly improve the yield rate, reduce waste caused by misalignment, and ensure the consistency and reliability of the sensor. By printing glass slurry on the lower substrate layer 600 and the upper substrate layer 200 using screen printing technology, the thickness of the slurry can be uniformly controlled, which helps to form a uniform glass substrate layer, thereby improving the performance stability of the product. By performing debinding and pre-firing through a set temperature curve, the organic components in the slurry can be effectively removed, bubbles or cracks can be prevented from being generated during the subsequent sintering process, and the quality of the finished product can be improved. The sintering process carried out in a variable load muffle furnace can ensure good bonding between the three-layer structure and form a strong and reliable connection through precise control of the temperature curve and the holding time, plus appropriate preload. The electrodes are interconnected with the ASIC chip through gold wire bonding technology, which ensures the reliability and efficiency of signal transmission and also enhances the durability of the product.

[0038] In a specific embodiment of the present application: The first step is to prepare a high-precision wafer-level screen printing plate. The structure of the screen printing plate is as follows Figure 1 As shown, the printed graphics include: two pairs of screen printing marks, one pair of wafer-level alignment marks 50, and 40 slurry units; screen printing marks (such as Figure 2 As shown), wafer-level alignment mark 50 (as shown Figure 3 as shown) and slurry units (as Figure 4 The shape, size and position dimensions of the screen are shown in Table 1. The thickness of the screen photosensitive adhesive is 35um~50um, the screen frame material is cast aluminum, the specification is: 320mm*320mm, the screen is made of stainless steel screen or nylon screen, the screen mesh is 150 mesh~250 mesh, the thickness of the photosensitive adhesive is 35um±1um; the viscosity of the high-temperature glass slurry is: 80Pa.s~100Pa.s, 250 mesh~300 mesh, the sintering temperature is: 500 degrees~550 degrees, and the sintering time is: 15 minutes~30 minutes.

[0039] Table 1 Package structure parameters (unit: um) The second step is screen printing of the lower base layer 600. The lower base layer 600 uses 3-inch to 8-inch z-cut quartz crystal with a thickness of 1000um to 2800um. The screen printing mark and wafer-level alignment mark 50 are processed in advance on the wafer through high-precision laser marking, wet etching or dry etching, and a high-precision screen printing process with CCD alignment is adopted. A transparent film film is covered on the light plate wafer of the same thickness, and a cross-shaped alignment mark is formed by screen printing. It is clamped with the electronic marks of two CCDs. After determining the position, the formal film is placed in the suction cup and sucked. The workbench is adjusted so that the cross mark on the wafer coincides with the electronic mark. The printing width of the glass slurry is 400um to 500um, and the glass slurry is placed in the printing thickness of 25um to 30um. After printing, the wafer is left to stand on the platform for 3 to 5 minutes to allow the glass slurry to flow level. Figure 5 shown.

[0040] The third step is screen printing of the upper substrate layer 200. The lower substrate layer 600 uses 3~8 inch z-cut quartz crystal with a thickness of 1000um~1500um. The wafer is marked with high-precision laser, wet etching or dry etching, and the screen printing mark and wafer-level alignment mark 50 are processed in advance. The high-precision screen printing process with CCD alignment is adopted; the light plate wafer of the same thickness is covered with a transparent film, and a cross-shaped alignment mark is formed by screen printing. It is clamped with two CCD electronic marks. After determining the position, the formal film is placed in the suction cup and sucked. The workbench is adjusted so that the cross mark on the wafer coincides with the electronic mark. The printing width of the glass slurry is 400um~500um, and the glass slurry is placed in the printing thickness of 25um~30um. After printing, the wafer is left to stand on the platform for 3~5 minutes to allow the glass slurry to flow level. Figure 6 shown.

[0041] The fourth step is debinding and pre-firing. Place the lower substrate layer 600 and the upper substrate layer 200 with glass paste after printing in a high-temperature oven, set the debinding and pre-firing temperature curve, start from room temperature, and heat up to 150 degrees at a heating rate of 5 degrees / minute, keep warm for 15 minutes to 30 minutes to discharge the organic solvent; heat up to 200 degrees, keep warm for 30 minutes, discharge the organic binder; heat up to 250 degrees, keep warm for 15 to 30 minutes, activate the paste thixotropic agent; heat up to 300 degrees, keep warm for 15 to 30 minutes, realize glass paste crystallization; heat up to 350 degrees, keep warm for 15 to 30 minutes, realize glass paste melting and sintering, form a ceramic glass substrate layer, and then cool to room temperature with the furnace before taking out the wafer.

[0042] The fifth step is the two-layer wafer-level alignment and pre-fixation. The wafer-level alignment equipment is used to place the lower base layer 600 into the upper suction cup of the alignment equipment and hold it in place. The two wafer-level alignment marks 50 of the lower substrate are marked with an electronic mark. The pressure-sensitive film 400 layer is placed into the lower suction cup of the alignment equipment and held in place. By adjusting the three-axis displacement of the lower suction cup, the alignment mark of the pressure-sensitive film 400 adsorbed on the lower suction cup is made to coincide with the marked electronic mark. At three locations on the edge of the pressure-sensitive film 400 wafer, three points of UV glue 60 are applied with a glue dispenser. The viscosity of the UV glue 60 is 50Pa.s~100Pa.s. The upper suction cup is then moved downward so that the upper and lower suction cups fit together. The UV glue 60 is squeezed out from the edge of the wafer. The UV glue 60 is irradiated by the three probes of the ultraviolet light machine. The curing time is 3 minutes~5 minutes. The two-layer wafer is pre-fixed by curing the UV glue 60. Figure 7 shown.

[0043] The sixth step is wafer-level alignment and pre-fixation of the three-layer structure. Use wafer-level alignment equipment to place the assembly into the alignment equipment, suck it with the upper suction cup, mark the two wafer-level alignment marks 50 of the lower assembly with an electronic mark, place the upper substrate into the lower suction cup of the alignment equipment and suck it, and adjust the three-axis displacement of the lower suction cup so that the alignment mark of the pressure-sensitive film 400 adsorbed on the lower suction cup coincides with the alignment mark and electronic mark of the lower substrate. Use a glue dispenser to apply three points of UV glue 60 at three locations on the wafer edge of the upper substrate, where the viscosity of UV glue 60 is 50Pa.s~100Pa.s, and then move the upper suction cup downward so that the upper and lower suction cups fit together, and UV glue 60 is squeezed out from the edge of the wafer. The UV glue 60 is irradiated by the three probes of the ultraviolet light machine. The curing time is 3~5 minutes. The three-layer wafer is pre-fixed by curing the UV glue 60, as shown in the following figure. Figure 8 shown.

[0044] The seventh step is to perform atmospheric sintering on the wafer level of the three-layer structure; place the three-layer assembly into the graphite fixture on the work surface of the variable load muffle furnace, and apply a preload of 5 to 10 kg to the three-layer wafer to achieve pre-fixation of the three-layer wafer and the graphite fixture. Set the heating curve and insulation curve of the equipment, starting from room temperature, with a heating rate of 5 degrees / minute, heating to 520 degrees, and a insulation time of 15 to 30 minutes. The load pressure at the insulation point is 150kg to 250kg. After the insulation is completed, the three-layer wafer is cooled with the furnace. When the temperature drops to 250 to 260 degrees, the load is unloaded. When the temperature drops to 150 degrees, the furnace door is opened and quickly cooled to room temperature. During the sintering process, the UV glue 60 is automatically carbonized and decomposed. Fig. 9 shown.

[0045] The eighth step is wafer-level dicing of the three-layer structure. Use a picosecond laser scribing machine or a grinding wheel scribing machine to fix the three-layer wafer on the working suction cup, and calibrate the wafer position through the scribing alignment cross mark on the upper edge of the wafer, so that the laser scribing position and direction coincide with the position and direction to be diced of the three-layer wafer, with a coincidence degree of +-10um; the scribing step is 8100um in the x direction and 8100um in the y direction, and the chip edge collapse is controlled within 50um. After scribing, a MEMS (Micro-Electro-Mechanical Systems) header bare DIE (a single integrated circuit chip) is formed.

[0046] The ninth step is ASIC patch and gold wire bonding. Use a glue dispenser to apply epoxy glue 70 on the upper surface of the MEMS header, place the ASIC bare DIE on the upper surface of the header, put the product in a blast oven, start from room temperature, heat up at a rate of 5 degrees / minute, the curing temperature is 80 degrees ~ 120 degrees, the curing time is 15 ~ 30 minutes, and then cool with the furnace. The shear strength after bonding is not less than 5MPa. Place the header after patching on the gold wire bonding machine, and through the gold wire bonding process, connect the lower substrate motor and the pressure-sensitive film 400 electrodes to the preset pad positions of the upper substrate through gold wires, and then interconnect the three electrodes of the top layer of the upper substrate (the lower base layer 600 electrodes, the pressure-sensitive film 400 electrodes, and the upper base layer 200 electrodes) with the gold wires of the ASIC chip, and lead out the input and output signals of the ASIC chip through gold wire bonding. The diameter of the gold wire is 25um, and the tensile strength of the gold wire is 5 grams to 8 grams. Fig.10 shown.

[0047] An embodiment of the present invention further provides a differential pressure sensor sensitive structure 10, which is preferably manufactured using the packaging method of the present invention to simplify the process and reduce costs.

[0048] Reference Fig.10The differential pressure sensor sensitive structure 10 of the present embodiment includes an ASIC chip, an upper substrate layer 200, a lower substrate layer 600 and a pressure-sensitive film 400. The upper substrate layer 200 and the lower substrate layer 600 are arranged opposite to each other and spaced apart. The ASIC chip is arranged on the side of the upper substrate layer 200 away from the lower substrate layer 600. The pressure-sensitive film 400 is arranged between the upper substrate layer 200 and the lower substrate layer 600. The upper substrate layer 200, the pressure-sensitive film 400 and the lower substrate layer 600 are bonded and connected by glass paste.

[0049] The ASIC (Application-Specific Integrated Circuit) conditioning chip is located on the side of the upper substrate layer 200 away from the lower substrate layer 600, and is responsible for processing and outputting differential capacitance signals. It calculates the differential capacitance value by detecting the changes in the upper capacitance Ct310 and the lower capacitance Cb510, thereby realizing pressure measurement. The ASIC conditioning chip 100 can convert analog signals into digital signals, is compatible with high-speed digital circuits, and facilitates subsequent data processing and transmission.

[0050] The upper substrate layer 200 is opposite to the lower substrate layer 600 and is spaced apart. A lower electrode 640 is provided on the upper substrate layer 200. The main function of the upper substrate layer 200 is to provide a supporting platform for mounting the ASIC conditioning chip 100 and forming the first chamber 300. An upper capacitor Ct310 is formed between the lower electrode 640 of the upper substrate layer 200 and the first electrode 460 of the pressure-sensitive film 400 for detecting pressure changes.

[0051] The lower substrate layer 600 is opposite to the upper substrate layer 200 and is spaced apart. An upper electrode 240 is disposed on the lower substrate layer 600. The main function of the lower substrate layer 600 is to provide another supporting platform for forming the second chamber 500. A lower capacitor Cb510 is formed between the upper electrode 240 of the lower substrate layer 600 and the second electrode 470 of the pressure-sensitive film 400 for detecting pressure changes.

[0052] The pressure-sensitive film 400 is disposed between the upper substrate layer 200 and the lower substrate layer 600 and is a core component that is sensitive to pressure. The pressure-sensitive film 400 is provided with a first electrode 460 and a second electrode 470, which respectively form an upper capacitor Ct310 and a lower capacitor Cb510 with the lower electrode 640 of the upper substrate layer 200 and the upper electrode 240 of the lower substrate layer 600. When the external pressure changes, the pressure-sensitive film 400 will deform, causing the capacitance values ​​of the upper capacitor Ct310 and the lower capacitor Cb510 to change, thereby achieving pressure measurement.

[0053] The upper substrate layer 200, the pressure-sensitive film 400 and the lower substrate layer 600 are bonded together to form an integral structure. The bonding connection ensures the stability and airtightness of the structure and prevents the external environment from affecting the internal chamber. The glass paste sealing that matches the thermal expansion coefficient of the quartz crystal improves the bonding strength, airtightness and electrical insulation of the components.

[0054] The first chamber 300 is located between the upper substrate 200 and the pressure-sensitive film 400. The upper capacitor Ct310 is formed between the lower electrode 640 of the upper substrate 200 and the first electrode 460 of the pressure-sensitive film 400. The pressure change in the first chamber 300 will cause the pressure-sensitive film 400 to deform, thereby changing the value of the upper capacitor Ct310.

[0055] The second chamber 500 is located between the pressure-sensitive film 400 and the lower base layer 600. A lower capacitor Cb510 is formed between the upper electrode 240 of the lower base layer 600 and the second electrode 470 of the pressure-sensitive film 400. Pressure changes in the second chamber 500 cause deformation of the pressure-sensitive film 400, thereby changing the value of the lower capacitor Cb510.

[0056] The isolation grooves opened on the pressure-sensitive film 400 form stress isolation beams, which can effectively isolate packaging stress and temperature stress, reduce the influence of these stresses on the deformation of the pressure-sensitive film 400, thereby suppressing mechanical common mode errors and improving the stability and accuracy of the sensor.

[0057] Compared with the flat membrane structure of the pressure-sensitive membrane 400, the pressure-sensitive membrane 400 with the isolation groove can change the external pressure deformation from tensile and compressive deformation to bending deformation. The bending deformation has a lower stiffness, so the sensitivity of the pressure-sensitive membrane 400 is significantly improved, and it can more accurately reflect the changes in external pressure.

[0058] Through the bending deformation with lower stiffness, the assembly stress and thermal stress can be converted into the deformation of the concave cavity folded beam, which ensures the zero bias stability of the vibration beam and improves the zero bias stability of the sensor under different temperatures and assembly conditions.

[0059] Reference Figure 5 and Figure 6 According to a differential pressure sensor sensitive structure 10 provided by the present invention, the pressure-sensitive membrane 400 is provided with a first isolation groove 410 and a second isolation groove 420 which are symmetrical along its midline plane, the first isolation groove 410 is arranged on the side of the pressure-sensitive membrane 400 facing the upper base layer 200, and is located in the first chamber 300; the second isolation groove 420 is arranged on the side of the pressure-sensitive membrane 400 facing the lower base layer 600, and is located in the second chamber 500.

[0060] It is understandable that the first isolation groove 410 and the second isolation groove 420 form a stress isolation beam on the pressure-sensitive film 400. The isolation beam can effectively isolate the packaging stress and temperature stress, and reduce the influence of these stresses on the deformation of the pressure-sensitive film 400. During the packaging process, packaging stress may be generated due to the different thermal expansion coefficients of different materials. The design of the isolation groove can disperse these stresses to avoid adverse effects on the pressure-sensitive film 400. When the temperature changes, different materials have different degrees of thermal expansion, which may generate temperature stress. The design of the isolation groove can effectively absorb and disperse these temperature stresses and reduce their influence on the pressure-sensitive film 400.

[0061] The first isolation groove 410 and the second isolation groove 420 are symmetrically arranged along the midline plane of the pressure-sensitive film 400. This symmetrical design ensures that the deformation of the pressure-sensitive film 400 when under pressure is symmetrical, reducing the error caused by asymmetrical deformation. In addition, the symmetrical design helps to suppress mechanical common mode errors and improve the stability and accuracy of the sensor. At the same time, the symmetrical design makes the response of the pressure-sensitive film 400 in different directions more uniform, improving the reliability and consistency of the sensor.

[0062] Reference Figure 5 and Figure 6 According to a differential pressure sensor sensitive structure 10 provided by the present invention, the upper base layer 200 is provided with a plurality of upper limit bosses 220 protruding from the outer peripheral edge of one side of the pressure-sensitive membrane 400, and the plurality of upper limit bosses 220 are evenly arranged along the peripheral side of the pressure-sensitive membrane 400; the lower base layer 600 is provided with a plurality of lower limit bosses 620 protruding from the outer peripheral edge of one side of the pressure-sensitive membrane 400, and the plurality of lower limit bosses 620 are evenly arranged along the peripheral side of the pressure-sensitive membrane 400.

[0063] It is understandable that the upper limit boss 220 and the lower limit boss 620 can accurately control the bonding thickness between the upper substrate layer 200 and the pressure-sensitive film 400, and the lower substrate layer 600 and the pressure-sensitive film 400. Through the limiting effect of the limiting boss, it can be ensured that the glass paste is evenly distributed during the sintering process to form a consistent bonding thickness, thereby ensuring the consistency of the capacitance gap between the upper capacitor Ct310 and the lower capacitor Cb510. Accurately controlling the bonding thickness helps to improve the measurement accuracy of the capacitance value and ensure the high sensitivity and stability of the sensor.

[0064] Reference Fig.11 According to a differential pressure sensor sensitive structure 10 provided by the present invention, the upper base layer 200 is provided with an upper air guide hole 230 penetrating itself along the thickness direction, and the upper air guide hole 230 is connected to the first chamber 300; the lower base layer 600 is provided with a lower air guide hole 630 penetrating itself along the thickness direction, and the lower air guide hole 630 is connected to the second chamber.

[0065] It is understandable that the upper air holes 230 and the lower air holes 630 provide an air channel for the sensor, so that the differential pressure can be transmitted to the chambers on both sides of the pressure-sensitive membrane 400. This is the basic principle of the operation of the differential pressure sensor, that is, detecting pressure changes by measuring the pressure difference between the two chambers. When the differential pressure acts on the sensor, the upper air holes 230 allow the pressure to be transmitted to the first chamber 300, and the lower air holes 630 allow the pressure to be transmitted to the second chamber 500. In this way, a pressure difference will be generated on both sides of the pressure-sensitive membrane 400, causing the pressure-sensitive membrane 400 to deform. Through the air holes, the pressure changes can be quickly transmitted to the pressure-sensitive membrane 400, thereby improving the response speed of the sensor.

[0066] Reference Fig.11 According to a differential pressure sensor sensitive structure 10 provided by the present invention, a first electrode pad 430 is arranged on the side of the pressure-sensitive film 400 facing the upper base layer 200, and the first electrode pad 430 is electrically connected to the first electrode 460. A second electrode pad 440 is arranged on the side of the pressure-sensitive film 400 facing the lower base layer 600, and the second electrode pad 440 is electrically connected to the second electrode 470. The first electrode pad 430 and the second electrode pad 440 are electrically connected through the plated side edge 450.

[0067] It can be understood that in this embodiment, electrode pads are arranged on both sides of the pressure-sensitive film 400. The first electrode pad 430 and the second electrode pad 440 provide an electrical connection interface for the first electrode 460 and the second electrode 470, and are electrically connected through the coated side edges 450, thereby ensuring a reliable connection between the electrodes, improving the integrity and transmission quality of the signal, and ensuring the high precision and stability of the sensor.

[0068] Reference Fig.10 and Fig.11 According to a differential pressure sensor sensitive structure 10 provided by the present invention, the differential pressure sensor sensitive structure 10 also includes a bonding gold wire 900, and the ASIC conditioning chip 100 is electrically connected to the first electrode 460, the second electrode 470, the upper electrode 240 and the lower electrode 640 respectively through the bonding gold wire 900.

[0069] It can be understood that the bonding gold wire 900 is a bridge connecting the ASIC conditioning chip 100 and the various electrodes (first electrode 460, second electrode 470, upper electrode 240 and lower electrode 640) in the differential pressure sensor sensitive structure 10. The high conductivity and good mechanical properties of the gold wire ensure a stable and reliable electrical connection between the electrode and the ASIC chip. At the same time, the bonding gold wire 900 is also responsible for transmitting electrical signals in the differential pressure sensor sensitive structure 10. The signals include capacitance changes caused by pressure changes, temperature compensation signals, etc. Through the bonding gold wire 900, these signals can be efficiently transmitted to the ASIC conditioning chip 100 for processing and analysis.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for packaging a sensitive structure of a differential pressure sensor, characterized in that: The steps include: preparing a screen printing plate including a screen printing mark, a wafer-level alignment mark, and a slurry unit; Processing a screen printing mark and a wafer-level alignment mark on the lower base layer wafer, aligning the screen printing plate with the lower base layer wafer, and printing glass paste on the lower base layer wafer; Processing a screen printing mark and a wafer-level alignment mark on the upper substrate layer wafer, aligning the screen printing plate with the upper substrate layer wafer, and printing glass paste on the upper substrate layer wafer; The printed lower substrate layer wafer and upper substrate layer wafer are placed in an oven to perform binder removal and pre-burning according to a set temperature curve; Aligning the lower substrate layer wafer and the pressure-sensitive film layer wafer and performing pre-fixation; The upper substrate layer wafer is aligned with the fixed lower substrate layer wafer and the pressure-sensitive film layer and then pre-fixed; The three-layer pre-fixed wafer assembly is placed in a variable load muffle furnace, a preload is applied, sintering is performed according to a set temperature curve and a heat preservation curve, and the furnace is cooled; The cooled three-layer wafer is cut to form a bare DIE for the MEMS header; Apply epoxy glue on the upper surface of the MEMS head, mount the ASIC bare DIE, and perform thermal curing; Through the gold wire bonding process, each electrode is interconnected with the ASIC chip to complete the electrical connection.

2. The method for packaging the sensitive structure of a differential pressure sensor according to claim 1, characterized in that: When preparing the screen printing stencil, the method further comprises: Determine the thickness of the photosensitive resin of the screen printing plate, the material of the screen frame, the type of the screen and the mesh count of the screen.

3. The packaging method of the differential pressure sensor sensitive structure according to claim 1, characterized in that: The method further comprises: Prepare glass slurry, and set the viscosity, mesh size, sintering temperature and sintering time of the glass slurry.

4. The method for packaging the sensitive structure of a differential pressure sensor according to claim 1, characterized in that: The screen printing plate and the lower substrate wafer are aligned via a CCD; And / or, the screen printing plate and the upper substrate wafer are aligned via a CCD.

5. The method for packaging the sensitive structure of a differential pressure sensor according to claim 1, characterized in that: The debinding and pre-burning include: Starting from room temperature, heat up to 150 degrees at a rate of 5 degrees / minute, keep warm for 15 to 30 minutes, and discharge the organic solvent; heat up to 200 degrees, keep warm for 30 minutes, and discharge the organic binder; heat up to 250 degrees, keep warm for 15 to 30 minutes, activate the thixotropic agent of the slurry; heat up to 300 degrees, keep warm for 15 to 30 minutes, and achieve crystallization of the glass slurry; heat up to 350 degrees, keep warm for 15 to 30 minutes, and achieve melting and sintering of the glass slurry to form a ceramic glass base layer, and then cool to room temperature with the furnace before taking out the wafer.

6. The method for packaging the sensitive structure of a differential pressure sensor according to claim 1, characterized in that: When the glass paste is printed on the lower substrate layer or the upper substrate layer, the printing width of the glass paste is 400um-500um, the printing thickness of the glass paste is 25um-30um, and the wafer after printing is left to stand for 3-5 minutes.

7. The method for packaging the sensitive structure of a differential pressure sensor according to claim 1, characterized in that: The sintering comprises: Starting from room temperature, the heating rate is 5 degrees / minute, the temperature is raised to 520 degrees, the insulation time is 15 to 30 minutes, and the load pressure at the insulation point is 150kg to 250kg. After the insulation is completed, the three layers of wafers are cooled with the furnace. When the temperature drops to 250 to 260 degrees, the load is unloaded. When the temperature drops to 150 degrees, the furnace door is opened and quickly cooled to room temperature.

8. The method for packaging the sensitive structure of a differential pressure sensor according to claim 1, characterized in that: The thermal curing comprises: Starting from room temperature, the heating rate is 5 degrees / minute, the curing temperature is 80 degrees ~ 120 degrees, the curing time is 15 minutes ~ 30 minutes, and then cooled in the furnace.

9. The method for packaging the sensitive structure of a differential pressure sensor according to claim 1, characterized in that: The outer peripheral edge of the upper base layer on one side facing the pressure-sensitive film is protruded to form a plurality of upper limit bosses, and the plurality of upper limit bosses are evenly arranged along the peripheral side of the pressure-sensitive film; And / or, a plurality of lower limit bosses are protruding from the outer peripheral edge of one side of the lower base layer facing the pressure-sensitive film, and the plurality of lower limit bosses are evenly arranged along the peripheral side of the pressure-sensitive film.

10. A differential pressure sensor sensitive structure, packaged using the differential pressure sensor sensitive structure packaging method according to any one of claims 1 to 9, characterized in that: The differential pressure sensor sensitive structure includes an ASIC chip, an upper base layer, a lower base layer and a pressure-sensitive film. The upper base layer and the lower base layer are arranged opposite to each other and at intervals. The ASIC chip is arranged on the side of the upper base layer away from the lower base layer. The pressure-sensitive film is arranged between the upper base layer and the lower base layer. The upper base layer, the pressure-sensitive film and the lower base layer are bonded and connected by glass paste.

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