MEMS acoustic device packaging structure and MEMS sensor

Abstract

The invention discloses an MEMS acoustic device packaging structure and an MEMS sensor, and the structure comprises a first device and a second device, and is characterized in that the first device is packaged in a packaging body; a rewiring layer connected with the electrical interface is electroplated in the packaging body, a conductive block is electroplated on a part of the rewiring layer, and the top surface of the conductive block is flush with the packaging body and is exposed; the second device is electrically connected with the conductive block and is further stacked and connected with the first device; mounting a substrate ring on the packaging body to surround the second device; a sealing substrate ring is attached to the cover plate, a sound hole of the cover plate is aligned to the middle of a vibrating diaphragm of the second device, and before the rewiring layer is electroplated in the packaging body, the packaging material is vertically etched to the bottom face of the packaging body, and metal columns are electroplated to be completely filled. A wire bonding process is not needed, the stacking space is saved, the whole structure is high in integration degree, smaller in size, good in structural stability and more stable and reliable in line transmission.

Description

Technical Field

[0001] The present invention belongs to the technical field of sensors, and in particular relates to a MEMS acoustic device packaging structure and a MEMS sensor. Background Art

[0002] MEMS (Micro-Electro-Mechanical System) technology is the hottest sensor manufacturing technology today, and it is also an important driving force for the miniaturization, intelligence and low energy consumption of sensors. MEMS technology has greatly promoted the development of sensors. MEMS mainly uses microelectronics technology to shape the mechanical structure of sensors in a micro-nano volume. MEMS sensors are devices formed by packaging a second device and a dedicated integrated circuit chip (first device) together. The second device converts sound into signal changes such as capacitance and resistance, and the first device converts signal changes such as capacitance and resistance into electrical signals, thereby realizing the function of MEMS sensors-converting external signals into electrical signals. MEMS acoustic sensors mainly refer to silicon microphones, ultrasonic sensors, etc.

[0003] In the existing acoustic sensor, the second device is arranged flatly with the first device, and the electrode of the second device is above the substrate. The second device and the first device are electrically connected by connecting metal wires through a wire bonding process. This structural setting causes the sensor to be too large.

[0004] The Chinese patent publication number is CN221319324U, which discloses a MEMS packaging structure and a MEMS acoustic sensor including the same. The MEMS packaging structure includes: a third substrate; a first substrate, on which a sound inlet hole is opened; a second substrate, which is hollow and ring-shaped, and is sandwiched between the first substrate and the third substrate; wherein, in the device installation space, the second device is fixed on the first substrate, and its back cavity faces the sound inlet hole; the first device is fixed on the third substrate; an electrical signal guide column for signal transmission is formed longitudinally inside the second substrate, and the sensing signal of the second device is transmitted to the first device through the electrical signal guide column, eliminating the traditional wire bonding process and also realizing the interconnection of signals between chips and between substrates, which will greatly reduce the volume of the packaged device and meet the needs of higher circuit integration, but this technology requires the use of three substrates, and circuits need to be set in each substrate, and the second device still needs a wire bonding process to realize electrical connection with the circuit in the substrate, and the first device and its electrical structure are exposed, which affects the service life, and the process is complex and the integration is low. Summary of the invention

[0005] In order to solve the above problems in the prior art, the present invention provides a MEMS acoustic device packaging structure and a MEMS sensor.

[0006] To achieve the above object, the present invention provides a MEMS acoustic device packaging structure, including a first device and a second device, and further comprising: The first device is encapsulated in a package; A redistribution layer connected to the electrical interface is electroplated in the package body, and a conductive block is electroplated on a portion of the redistribution layer, wherein the top surface of the conductive block is flush with the package body and exposed; The second device is electrically interconnected with the conductive block, and further interconnected with the first device stack; A substrate ring is mounted on the package body to surround the second device; The cover plate is mounted on the sealing substrate ring, and the sound hole of the cover plate is aligned with the middle part of the diaphragm of the second device.

[0007] Furthermore, before electroplating the redistribution layer in the package, the encapsulation material is vertically etched to the bottom surface of the package, and the metal pillars are electroplated to completely fill the bottom surface.

[0008] Furthermore, the top of the metal column is electrically connected to another part of the redistribution layer, and the first device is electrically transferred from the electrical interface to the bottom of the metal column through the redistribution layer.

[0009] Furthermore, the bottom end of the metal column is flush with the bottom surface of the package body and exposed, external pins are electroplated on the bottom surface of the metal column exposed outside the package body, and the bottom end of the metal column is electrically connected to some of the external pins.

[0010] Furthermore, the substrate of the second device is covered with electrodes, and the electrodes are covered with a diaphragm.

[0011] Furthermore, the distance between the diaphragm and the electrode is 1-5 μm.

[0012] Furthermore, the material of the substrate of the second device is selected from one or more of flexible materials, glass, and semiconductor materials.

[0013] Furthermore, the material of the diaphragm is selected from one or more of polysilicon, silicon nitride or metal.

[0014] Furthermore, a back cavity is etched through the middle of the substrate of the second device, and the back cavity is located directly below the diaphragm. A circuit is provided inside the substrate of the second device, and a solder pin is provided at the bottom of the substrate. The top of the circuit is electrically interconnected with the electrode, and the bottom of the circuit is electrically interconnected with the solder pin at the bottom of the substrate.

[0015] Furthermore, the second device soldering foot is soldered to the top surface of the conductive block exposed outside the package body through reflow soldering.

[0016] Furthermore, the diaphragm generates mechanical vibrations, causing changes in electrical values, which are sequentially transmitted through electrodes, circuits, solder pins, conductive blocks, and redistribution layers to the first device for signal processing.

[0017] Furthermore, the first device is an ASIC chip.

[0018] Furthermore, the second device is a MEMS chip.

[0019] Furthermore, the base plate ring and the cover plate are bonded together by adhesive.

[0020] A MEMS sensor comprises the above-mentioned MEMS acoustic device packaging structure.

[0021] The beneficial effects of the present invention are: 1. The first device is encapsulated in the package body, so that the ASIC chip is protected from corrosion by the external environment and the service life is extended. The back side of the first device is exposed outside the package body through the adhesive, thereby enhancing the heat dissipation performance.

[0022] 2. The electrical properties of the second device are led out from the front to the back, and the mounting flexibility is high. The second device is welded on the first device to achieve stacking of the two devices without the need for wire bonding process, saving stacking space. The entire structure has high integration, smaller size, good structural stability, and more stable and reliable line transmission. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A cross-sectional view of a MEMS acoustic device packaging structure and a MEMS sensor of the present invention; Figure 2-Figure 8 A manufacturing process flow chart of a MEMS acoustic device packaging structure and a second device of a MEMS sensor of the present invention; Figure 9-Figure 19 The present invention is a MEMS acoustic device packaging structure and a MEMS sensor manufacturing process flow chart.

[0024] In the figure: 1. first device; 2. redistribution layer; 3. conductive block; 4. package body; 5. metal column; 6. external pin; 7. second device; 8. solder foot; 9. substrate; 10. circuit; 11. back cavity; 12. diaphragm; 13. substrate ring; 14. cover plate; 15. sound hole. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings in the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention; the content of the present invention will be explained below in conjunction with specific implementation methods, examples of which are shown in the drawings, where the same or similar numbers throughout represent the same or similar components or components with the same or similar functions.

[0026] The terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments described herein can be implemented in an order other than that illustrated or described herein; the directional terms mentioned in the present invention, such as: up, down, left, right, front, back, inside, outside, front, back, side, etc., are only reference directions of the drawings. The following embodiments described with reference to the drawings and the directional terms used are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention. In addition, the various specific process and material examples provided by the present invention are all examples of other processes and / or the use of other materials that ordinary technicians in this field can recognize.

[0027] In order to better understand the purpose, structure and function of the present invention, the following is a further detailed description of a MEMS acoustic device packaging structure and a MEMS sensor proposed by the present invention in conjunction with the accompanying drawings. Figure 1 As shown, the structure includes a first device 1 and a second device 7, and further includes: A package body 4, in which the first device 1 is encapsulated, and the first device 1 is an ASIC chip; The redistribution layer 2 and the conductive block 3 are plated in the package body 4 and connected to the electrical interface of the first device 1. The conductive block 3 is plated on a part of the redistribution layer 2. The top surface of the conductive block 3 is flush with the top surface of the package body 4 and exposed. The structural dimensions of the MEMS chip and the ASIC chip are often quite different. The electrical interface of the ASIC chip is rearranged to adapt to the size of the MEMS chip by plating the redistribution layer 2 and the conductive block 3 in the package body 4 to ensure that the MEMS chip is stacked and mounted with the conductive block 3 of the ASIC chip through the bottom solder pins 8 of the substrate 9 to achieve electrical interconnection. The size of the entire sensor meets the miniaturization requirements, the structure is compact, and the layout is reasonable.

[0028] Before electroplating the redistribution layer 2 in the package body 4, the encapsulation material is vertically etched to the bottom surface of the package body 4, and the metal column 5 is electroplated to completely fill the drilled hole. The top of the metal column 5 is electrically connected to another part of the redistribution layer 2. The electrical property of the first device 1 is transferred from the electrical interface to the bottom end of the metal column 5 through the redistribution layer 2. The bottom end of the metal column 5 is flush with the bottom surface of the package body 4 and is exposed. External pins 6 are electroplated on the bottom surface of the exposed metal column 5 of the package body 4. The bottom end of the metal column 5 is electrically connected to part of the external pins 6. The external pins 6 serve as a connection bridge between the external electrical property of the sensor working area and the internal electrical property of the ASIC chip in the package body 4.

[0029] The second device 7 is mounted on the exposed conductive block 3 of the package body 4 through the solder pin 8 at the bottom of the substrate 9, so that the second device 7 and the first device 1 are stacked up and electrically interconnected. The substrate 9 of the second device 7 is covered with electrodes, and the diaphragm 12 is covered on the electrodes. The material of the substrate 9 of the second device 7 is selected from one or more of flexible materials, glass, and semiconductor materials. The substrate 9 is located at the bottom layer of the second device 7, serving as the mechanical support of the entire structure, providing structural stability, and serving as the base for other components such as electrodes and back cavity 11; the material of the diaphragm 12 is selected from one or more of polysilicon, silicon nitride or metal. The thickness of the diaphragm 12 is extremely thin, ranging from nanometers to micrometers, and is sensitive to sound pressure. Its vibration displacement is proportional to the sound pressure, and it is the core sensitive element of the sensor.

[0030] A back cavity 11 is etched through the middle of the substrate 9 of the second device 7, and the back cavity 11 is located directly below the diaphragm 12. The structure of the back cavity 11 allows the diaphragm 12 to vibrate freely under the action of sound pressure, avoiding air damping, and can balance the pressure on both sides of the diaphragm 12. A circuit 10 is provided inside the substrate 9 of the second device 7. The top of the circuit 10 is interconnected with the electrode, and the bottom of the circuit 10 is electrically interconnected with the solder pin 8 at the bottom of the substrate 9. The solder pin 8 of the second device 7 is welded to the top surface of the conductive block 3 exposed outside the package 4 through reflow soldering.

[0031] By adding a circuit 10 and solder feet 8 after etching the substrate 9 during the manufacturing process of the second device 7, the electrical properties of the second device 7 are pulled from the electrode on the front side (where the diaphragm 12 is located) to the solder feet 8 on the back side, and the second device 7 has better mounting flexibility and a compact structure.

[0032] The diaphragm 12 generates mechanical vibration, causing the electrical value to change, and is transmitted to the first device 1 for signal processing through the electrode, circuit 10, solder foot 8, conductive block 3, and redistribution layer 2 in sequence. The second device 7 is a MEMS chip.

[0033] The substrate ring 13 is mounted on the package body 4 to surround the second device 7 .

[0034] The cover plate 14 is mounted on the substrate ring 13 to seal the substrate ring 13. The sound hole 15 on the cover plate 14 is aligned with the middle position of the diaphragm 12 of the second device 7. The substrate ring 13 and the cover plate 14 are bonded by adhesive.

[0035] In this structure, the substrate ring 13 and the cover plate 14 encapsulate and protect the MEMS chip. The cover plate 14 has a sound hole 15, which is vertically aligned with the middle of the MEMS chip diaphragm 12. When the sound wave (air vibration) acts on the diaphragm 12 through the sound hole 15, the diaphragm 12 will vibrate mechanically as the sound pressure changes. The back cavity 11 of the substrate 9 provides vibration space and acoustic damping to adjust the mechanical response of the diaphragm 12. The mechanical vibration of the diaphragm 12 causes the distance between the electrode and the substrate 9 to change, and the electrical value of the electrode changes. The change in the electrical value of the electrode is transmitted to the ASIC chip through the circuit 10, the solder pin 8, the conductive block 3, and the redistribution layer 2. The ASIC chip processes the change in electrical values ​​such as capacitance value and amplifies the signal. The ASIC chip is integrated inside the sensor and encapsulated in the package 4. The plastic encapsulation material is encapsulated to protect it from moisture, dust and mechanical stress. The ASIC chip electrically leads its electrical properties to the outside of the package 4 through the redistribution layer 2, the metal column 5 and the external pin 6.

[0036] The above-mentioned MEMS acoustic device packaging structure is obtained through the following process flow, and the process flow can be generally summarized into the following steps: production of the second device 7, packaging of the first device 1 (mounting and encapsulating the first device 1 and electrically leading out the first device 1), mounting of the first device 1 and the second device 7 (mounting and interconnection of the second device 7), mounting of the substrate ring 13, and packaging of the cover plate 14.

[0037] The second device 7 is a MEMS chip, and the manufacturing steps of the second device 7 are specifically as follows: S1: Provide a carrier, which may be a resin plate commonly used in the art, and place the original substrate 9 for making the second device 7 on the carrier (eg Figure 2 As shown); the substrate 9 can be one or more of flexible materials, glass, and semiconductor materials, usually silicon, which has good mechanical properties, thermal stability, and good compatibility with micromachining processes. The substrate 9 is located at the bottom layer of the second device 7, serving as the mechanical support for the entire structure, providing structural stability, and serving as the base for other components such as electrodes and back cavity 11.

[0038] S2: Cover the upper surface of substrate 9 with a layer of electrode (such as Figure 3 As shown in the figure, the electrodes of the MEMS acoustic sensor are divided into fixed electrodes and movable electrodes. The fixed electrode is located above or below the diaphragm 12, parallel to the diaphragm 12, and fixed on the substrate 9, while the movable electrode is directly integrated on the surface of the diaphragm 12. The diaphragm 12 itself can be used as an electrode. In this application, the electrode covers the upper surface of the substrate 9.

[0039] S3: Continue to cover the electrode with a layer of diaphragm 12 (such as Figure 4 As shown), in the present invention, the electrode is arranged below the diaphragm 12, and the electrode is a fixed electrode. The fixed electrode is designed as a porous structure to reduce air damping and allow sound waves to pass through. The distance between the diaphragm 12 and the electrode is about 1-5μm, forming a variable capacitor. The diaphragm 12 is directly exposed to the external sound field. The material of the diaphragm 12 is selected from polycrystalline silicon. The polycrystalline silicon film has excellent properties such as high mobility of single crystal silicon material, compatibility with amorphous silicon thin film growth process, easy to achieve large-area growth, low preparation cost, etc., and is widely used in technical fields such as microelectronic devices. In addition, polycrystalline silicon film structure is also commonly used in micro-electromechanical systems (MEMS), especially as the basic vibration structure of sensor devices; the material of the diaphragm 12 can also be one or more of silicon nitride or metal, etc. The thickness of the diaphragm 12 on the second device is extremely thin, ranging from nanometers to micrometers, and is sensitive to sound pressure. Its vibration displacement is proportional to the sound pressure, and it is the core sensitive element of the sensor.

[0040] S4: The substrate 9 is peeled off from the carrier, and is flipped upside down and re-mounted on the carrier. At this time, the diaphragm 12 is in contact with the carrier, and the bottom of the substrate 9 is facing upward (such as Figure 5 as shown).

[0041] S5: etching in the middle of the substrate 9 to expose the electrode, so that the cylindrical substrate 9 becomes a cylindrical ring structure with a hollow middle, that is, the back cavity 11 of the substrate 9. The back cavity 11 is located directly below the diaphragm 12. The back cavity 11 is generally cylindrical or rectangular. The present invention takes the cylindrical shape as an example. The depth of the back cavity 11 is determined by the acoustic sensitivity and frequency response requirements of the specific product. The back cavity 11 structure allows the diaphragm 12 to vibrate freely under the action of sound pressure, avoids air damping, and can balance the pressure on both sides of the diaphragm 12; and simultaneously etch the remaining cylindrical ring of the substrate 9, also exposing the electrode (such as Figure 6 As shown), since the substrate 9 can be one or more of flexible materials, glass, and semiconductor materials, usually silicon, during etching, a protective film is coated on the surface of the substrate 9 to be etched, and the position to be etched is not coated for protection. In this application, anisotropic etching is used perpendicular to the surface of the substrate 9, and the etching passes through the surface of the substrate 9 to the upper surface of the electrode, so that the electrode surface is exposed.

[0042] S6: After etching on the cylindrical ring of the substrate 9, the holes formed by etching are filled by electroplating process, and the electroplated metal forms a circuit 10. The bottom of the circuit 10 is connected to the electrode as a whole, and the electroplated solder feet 8 (such as Figure 7As shown in the figure, in the process flow of manufacturing the second device 7, the back cavity etching of the substrate 9 after covering the electrode and the diaphragm 12 is a normal process for manufacturing the second device 7. Since the diaphragm 12 is very thin, protective measures need to be taken to protect the diaphragm 12 in the process flow, such as covering the surface of the diaphragm 12 with a polymer protective layer to prevent contamination or mechanical damage. The present invention will not go into details. After peeling off the carrier board, the second device 7 is manufactured (as shown in the figure). Figure 8 As shown in the figure), the diaphragm 12 generates mechanical vibration due to the impact of sound waves, causing changes in capacitance or other electrical values, and the electrode transmits the changed electrical values ​​to the welding foot 8 through the circuit.

[0043] During the manufacturing process of the second device 7, a substrate 9 is etched and then an electroplated circuit 10 and a solder foot 8 are added to electrically pull the second device 7 from the electrode on its front side (where the diaphragm 12 is located) to the solder foot 8 on its back side. The second device 7 has better mounting flexibility and a compact structure.

[0044] The first device 1 is an ASIC chip, which is encapsulated in a package 4. The manufacturing steps of the first device 1 are as follows: S1: Provide a carrier board, which may be a resin board commonly used in the art, and place the first device 1 on the carrier board (such as Fig. 9 As shown in FIG. 1 ), the front side of the first device 1 has an electrical interface, and the back side of the first device 1 is mounted on a carrier board.

[0045] S2: Encapsulate the first device 1 on the carrier board with an encapsulation material, and grind the top surface of the encapsulation horizontally by mechanical grinding until the front electrical interface of the first device 1 is exposed (such as Fig.10 as shown).

[0046] S3: vertically etch the encapsulation material at the corresponding position on the top surface of the encapsulation to form a drill hole until the surface of the carrier is exposed (such as Fig.11 as shown).

[0047] S4: Electroplating metal pillars 5 to fill the drilled holes through electroplating process, the bottom of the metal pillars 5 are in contact with the carrier, and the redistribution layer 2 is horizontally plated along the top surface of the package, the redistribution layer 2 is electrically connected to the exposed first device 1, and a conductive block 3 (such as Fig.12 As shown), another part of the redistribution layer 2 is electrically connected to the top of the metal pillar 5, and the electrical properties of the first device 1 are transferred from the electrical interface to the bottom of the metal pillar 5 through the redistribution layer 2. The electrical properties of the first device 1 are electrically connected via the electrical interface, the redistribution layer 2 and the conductive block 3.

[0048] S5: Continue to use the encapsulation material to encapsulate the top surface of the encapsulation in S2, encapsulate each redistribution layer 2, the conductive block 3, and the metal column 5 in the encapsulation material, and horizontally grind the top surface of the new encapsulation by mechanical grinding until the top surface of the conductive block 3 is exposed (such as Fig.13As shown in the figure), the conductive blocks 3 serve as electrical connection terminals between the first device 1 and the second device 7, and the number and layout of the conductive blocks 3 are set according to the electrical connection relationship between the second device 7 and the first device 1 of the actual product.

[0049] S6: The package is peeled off from the carrier, turned upside down, and then re-mounted on the carrier. At this time, the exposed conductive block 3 is in contact with the carrier, and the bottom of the exposed metal column 5 is exposed. External pins 6 are electroplated at corresponding positions on the surface of the package. Part of the external pins 6 is electrically connected to the exposed metal column 5 (such as Fig.14 as shown).

[0050] S7: After the electroplating is completed, the package is peeled off from the carrier to obtain the package body 4 of the first device 1 (such as Fig.15 As shown), for the case where multiple first devices 1 are mounted on the carrier at one time and multiple first devices 1 are processed simultaneously in the process flow, a cutting process is required at the end, that is, the encapsulation material is cut at the cutting path position of the safety area of ​​the entire encapsulation, so as to separate the package body 4 of each first device 1 into product units. The present invention takes the case of processing the encapsulation of one first device 1 as an example.

[0051] The first device 1 is encapsulated in the package body 4, so that the ASIC chip is protected from corrosion by the external environment and its service life is prolonged. The back side of the first device 1 is exposed outside the package body 4 through adhesive to enhance the heat dissipation performance.

[0052] The mounting steps of the first device 1 and the second device 7 are specifically as follows: S1: Re-place the package body 4 on the carrier board through the external pins 6, and stack the two devices by aligning the solder pins 8 of the second device 7 with the conductive blocks 3 exposed outside the package body 4 (such as Fig.16 As shown in the figure, the solder pin 8 of the second device 7 is soldered to the conductive block 3 exposed outside the package 4 through reflow soldering, and the two devices are electrically connected. The diaphragm 12 of the second device 7 is impacted by the sound wave to generate mechanical vibration, causing the capacitance or other electrical values ​​to change. The electrode transmits the changed electrical value to the solder pin 8 through the circuit 10, and the solder pin 8 is transmitted to the first device 1 through the conductive block 3 and the redistribution layer 2 for processing, such as signal amplification, filtering and analog-to-digital conversion (ADC). According to the specific product structure and its function, the electrical connection relationship between the first device 1 and the second device 7 is arranged, and the circuit 10 and solder pin 8 of the second device 7, as well as the number and position of the conductive block 3 and the redistribution layer 2 of the first device 1 are arranged accordingly. For example, if the clock or synchronization signal performance is increased, the ASIC needs synchronous sampling (such as a digital microphone), and may provide a clock signal to the MEMS to coordinate the work. The electrical connection relationship between the first device 1 and the second device 7 needs to be increased to realize this function. The accompanying drawings are all cross-sectional views, which only show the electrical connection relationship presented in the cross-sectional view. Other necessary electrical connection relationships between the ASIC chip and the MEMS chip are also within the protection scope of the present invention.

[0053] The present invention processes the first device 1 and the second device 7 separately and then mounts and stacks them together. The first device 1 and the second device 7 can be pre-fabricated separately and do not affect each other. The whole processing technology is more efficient. The present invention takes the second device 7 being processed first and the first device 1 being processed later as an example. The two devices are stacked by welding the welding feet 8 of the second device 7 to the conductive block 3 of the package body 4 of the first device 1 without using a wire bonding process, thus saving stacking space. The whole structure has a high degree of integration, a smaller size, good structural stability, and more stable and reliable line transmission.

[0054] The structural dimensions of MEMS chips and ASIC chips are often quite different. The electrical interface of the ASIC chip is rearranged to adapt to the size of the MEMS chip by electroplating the redistribution layer 2 and the conductive block 3 in the package 4, ensuring that the MEMS chip is stacked and mounted with the conductive block 3 of the ASIC chip through the bottom solder pins 8 of the substrate 9 to achieve electrical interconnection. The size of the entire sensor meets the miniaturization requirements, the structure is compact, and the layout is reasonable.

[0055] The steps of mounting the substrate ring 13 and packaging the cover plate 14 are specifically as follows: S1: The substrate ring 13 is mounted on the package body 4 to surround the second device 7 (eg Fig.17 As shown in the figure, the side of the substrate ring 13 is flush with the side of the package body 4 of the second device 7. The substrate ring 13 is arranged along the surface shape of the package body 4. The substrate ring 13 is a printed circuit board (PCB board). The reason for using the PCB board is that on the one hand, it has a low cost and a relatively mature process. On the other hand, it is convenient to directly connect the PCB board to the package body 4, and the connection and mounting can be achieved by adhesive glue. The height of the substrate ring 13 is higher than the height of the second device 7, and the second device 7 can be surrounded in the substrate ring 13.

[0056] S2: Mount the cover plate 14 on the substrate ring 13, and the side of the cover plate 14 is also flush with the side of the substrate ring 13 (such as Fig.18 As shown in the figure, the cover plate 14 and the substrate ring 13 can be connected and mounted by adhesive or the like, the substrate ring 13 is sealed, a sound hole 15 is left on the cover plate 14, the sound hole 15 is aligned with the middle position of the diaphragm 12 of the second device 7, the diaphragm 12 is aligned with the middle position of the back cavity 11 of the second device 7, the three are arranged vertically up and down, the diaphragm 12 is connected to the external environment through the sound hole 15, after peeling off the carrier, a MEMS acoustic device packaging structure product (such as Fig.19 as shown).

[0057] The working principle of MEMS (micro-electromechanical system) acoustic sensors (such as MEMS microphones) is based on the conversion of mechanical vibrations and electrical signals. The core is to convert sound waves (sound signals) into electrical signals through micromechanical structures. The core of the MEMS acoustic sensor is a micron-scale diaphragm 12, which is suspended above the back cavity 11. There are electrodes between the diaphragm 12 and the substrate 9, and the electrodes form a capacitor structure. The substrate ring 13 and the cover plate 14 encapsulate and protect the MEMS chip. The cover plate 14 has a sound hole 15, and the sound hole 15 is vertically aligned with the middle of the MEMS chip diaphragm 12. When the sound wave (air vibration) acts on the diaphragm 12 through the sound hole 15, the diaphragm 12 will vibrate mechanically with the change of sound pressure. The back cavity 11 of the substrate 9 provides vibration space and acoustic damping to adjust the mechanical response of the diaphragm 12. The mechanical vibration of the diaphragm 12 causes the distance between the electrode and the substrate 9 to change, and the electrical value of the electrode changes. For example, the capacitance value C is determined by the formula C=εA / d (where ε is the dielectric constant, A is the electrode area, and d is the capacitance value C). The electrode plate refers to the electrode and the substrate 9. The change of the electrical value of the electrode is transmitted to the ASIC chip through the circuit 10, the solder pin 8, the conductive block 3, and the redistribution layer 2. The present invention sets these structures and can also reduce or increase the corresponding components. As long as the electrical connection relationship between the ASIC chip and the MEMS chip can be achieved, it also belongs to the protection scope of the present invention. The sensor integrated application-specific integrated circuit (ASIC) is responsible for processing the change of electrical values ​​such as capacitance value. The ASIC chip is integrated inside the sensor to reduce noise interference and improve sensitivity. The ASIC chip provides a bias voltage (DC voltage) for the capacitor to convert the capacitance change into the charge change. The charge amplifier converts weak charges into voltage signals and converts analog voltage signals into digital signal outputs. The ASIC chip does not need to interact directly with the environment and is encapsulated in the package body 4. The plastic encapsulation material protects it from moisture, dust and mechanical stress. No additional protective structure is required after encapsulation. The overall integration of the sensor is higher. The ASIC chip is electrically connected to the outside of the package body 4 through the redistribution layer 2, the metal column 5 and the external pin 6. The external pin 6 serves as a bridge connecting the external electrical connection of the sensor working area with the internal electrical connection of the ASIC chip in the package body 4. Of course, other structures for realizing internal electrical connection of the package body 4 are also within the protection scope of the present invention.

[0058] A MEMS sensor comprises the above-mentioned MEMS acoustic device packaging structure.

[0059] The beneficial effects of the present invention are: 1. During the manufacturing process of the second device 7, a circuit 10 and a solder foot 8 are plated after etching the substrate 9, and the electrical properties of the second device 7 are pulled from the electrode on the front side (where the diaphragm 12 is located) to the solder foot 8 on the back side, so that the second device 7 has better mounting flexibility.

[0060] 2. The first device 1 is encapsulated in the package body 4 to protect the ASIC chip from corrosion by the external environment and extend its service life. The back side of the first device 1 is exposed outside the package body 4 through adhesive to enhance heat dissipation performance.

[0061] 3. The first device 1 and the second device 7 are processed separately and then mounted and stacked together. The first device 1 and the second device 7 can be pre-fabricated separately without affecting each other, and the whole processing technology is more efficient.

[0062] 4. By welding the welding foot 8 of the second device 7 to the conductive block 3 of the package 4 of the first device 1, the two devices are stacked without using a wire bonding process, saving stacking space, and the entire structure has a high degree of integration, a smaller size, good structural stability, and more stable and reliable line transmission.

[0063] In all the encapsulation steps of the present invention, the encapsulation material used is a plastic encapsulation material, and the specific material can be epoxy resin, cyanate, polyimide, etc., which has low cost and good curing performance. The packaging process plays an important role in the field of semiconductor manufacturing, mainly in terms of protection, connection, support, reliability and promotion of technological progress. The encapsulation method is the commonly used molding and injection molding method in this field.

[0064] All post-encapsulation grinding processes of the present invention use a grinding machine commonly used in the technical field to perform surface treatment on the package surface, that is, horizontal mechanical grinding on the top surface of the package, and finally the grinding surface is horizontal and flat after grinding, and the outer surface of the entire packaging structure is flat and smooth.

[0065] All the steps of the electroplating process of the present invention are to first use a photoresist film to form electroplating protection on the surface through exposure and development photolithography technology, protect the places that do not need electroplating with a photoresist film, expose the areas that need electroplating, and then form a metal seed layer in the area to be electroplated by sputtering or copper deposition or other appropriate methods. The metal seed layer is copper or other metal materials. The metal seed layer is to ensure the bonding force between the metals and metals and between the metals and the encapsulation materials in the subsequent electroplating, and at the same time provide a surface for the electroplating to attach conductive ions to ensure the electroplating effect. The entire steps in the electroplating process and the materials used are also technical common sense in the field. The metals electroplated in all the electroplating processes of the present invention are all made of metallic copper.

[0066] It is to be understood that the present invention is described by some embodiments, and it is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of the present invention are within the scope of protection of the present invention.

Claims

1. A MEMS acoustic device packaging structure, comprising a first device and a second device, characterized in that: Also includes: The first device is encapsulated in a package; A redistribution layer connected to the electrical interface is electroplated in the package body, and a conductive block is electroplated on a portion of the redistribution layer, wherein the top surface of the conductive block is flush with the package body and exposed; The second device is electrically interconnected with the conductive block, and further interconnected with the first device stack; A substrate ring is mounted on the package body to surround the second device; The cover plate is mounted on the sealing substrate ring, and the sound hole of the cover plate is aligned with the middle part of the diaphragm of the second device.

2. The MEMS acoustic device packaging structure according to claim 1, characterized in that: Before the redistribution layer is electroplated in the package, the encapsulation material is vertically etched to the bottom surface of the package, and the metal pillars are electroplated to completely fill the bottom surface.

3. The MEMS acoustic device packaging structure according to claim 2, characterized in that: The top of the metal column is electrically connected to another part of the redistribution layer, and the first device electrical property is transmitted from the electrical interface to the bottom of the metal column through the redistribution layer.

4. The MEMS acoustic device packaging structure according to claim 3, characterized in that: The bottom end of the metal column is flush with the bottom surface of the package body and exposed, and external pins are electroplated on the bottom surface of the metal column exposed outside the package body, and the bottom end of the metal column is electrically connected to some of the external pins.

5. The MEMS acoustic device packaging structure according to claim 1, characterized in that: The substrate of the second device is covered with electrodes, and the electrodes are covered with a diaphragm.

6. The MEMS acoustic device packaging structure according to claim 5, characterized in that: The distance between the diaphragm and the electrode is 1-5 μm.

7. The MEMS acoustic device packaging structure according to claim 5, characterized in that: The material of the substrate of the second device is selected from one or more of flexible materials, glass, and semiconductor materials.

8. The MEMS acoustic device packaging structure according to claim 5, characterized in that: The material of the diaphragm is selected from one or more of polysilicon, silicon nitride or metal.

9. The MEMS acoustic device packaging structure according to claim 5, characterized in that: The middle of the substrate of the second device is etched through to form a back cavity, which is located directly below the diaphragm. A circuit is provided inside the substrate of the second device, and a solder pin is provided at the bottom of the substrate. The top of the circuit is electrically connected to the electrode, and the bottom of the circuit is electrically connected to the solder pin at the bottom of the substrate.

10. The MEMS acoustic device packaging structure according to claim 9, characterized in that: The second device soldering foot is soldered to the top surface of the conductive block exposed outside the package body through reflow soldering.

11. The MEMS acoustic device packaging structure according to claim 9, characterized in that: The diaphragm generates mechanical vibration, causing electrical value changes, which are sequentially transmitted through electrodes, circuits, solder pins, conductive blocks, and redistribution layers to the first device for signal processing.

12. The MEMS acoustic device packaging structure according to claim 1, characterized in that: The first device is an ASIC chip.

13. The MEMS acoustic device packaging structure according to claim 1, characterized in that: The second device is a MEMS chip.

14. The MEMS acoustic device packaging structure according to claim 1, characterized in that: The base plate ring and the cover plate are bonded together by adhesive.

15. A MEMS sensor, characterized in that: The MEMS acoustic device packaging structure comprises any one of claims 1 to 14.

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