Circular capacitive MEMS microphone packaging structure and process

Abstract

The invention discloses a circular capacitive MEMS microphone packaging structure and process, and belongs to the technical field of semiconductor packaging. The structure comprises a PCB substrate adopting a circular design, and the substrate is provided with a through hole so as to form a front cavity with a self-contained cavity of an MEMS capacitive chip; the ASIC integrated chip and the MEMS capacitive chip are mounted on the substrate and are electrically connected with each other; the circular shell covers the periphery of the substrate, and a circular expansion back cavity surrounding the double chips is formed in the circular shell. The process comprises the steps of substrate dispensing and chip mounting, baking and curing, gold wire bridging, COB glue dispensing and coating, tin drawing, shell reflow soldering and curing and the like. According to the invention, through the cooperation of the circular substrate and the housing, the space of the back cavity is increased, and the SNR signal-to-noise ratio performance is effectively optimized; meanwhile, according to the packaging structure, the harsh requirement for the height of chip glue is lowered, the technological process is simplified, the operation cost is lowered, and product miniaturization and performance optimization are facilitated.

Description

Technical Field

[0001] This application belongs to the field of semiconductor packaging technology, and in particular relates to a circular capacitive MEMS microphone packaging structure and process. Background Technology

[0002] Conventional MEMS microphones typically use a rectangular PCB substrate and a rectangular housing for packaging. In the product structure design, the MEMS capacitive chip and the ASIC integrated chip are placed parallel to each other on the PCB substrate, fixed with surface mount adhesive, and electrically connected to each other and to the substrate solder joints using gold wires. Finally, the acoustic cavity is formed by tinning the perimeter of the substrate and fastening it with the rectangular housing.

[0003] However, this conventional packaging structure has the following drawbacks in practical applications: Acoustic performance limitations: Due to the limited utilization of internal space within the rectangular shell, the volume of the back chamber is difficult to further increase. In addition, the right-angled edges of the rectangular structure are prone to acoustic wave diffraction and standing wave interference, affecting the smoothness of the frequency response.

[0004] According to acoustic principles, the size of the back cavity directly affects the microphone's sensitivity and signal-to-noise ratio (SNR). A smaller back cavity space limits the achievement of high-performance acoustic indicators.

[0005] Inflexible structural layout: Rectangular substrates often suffer from low space utilization in miniaturized electronic devices. In compact designs, ensuring sufficient back cavity space often requires increasing the overall product size, which is detrimental to the development of thinner and lighter end products.

[0006] Production Costs and Process Challenges: Due to space constraints, the encapsulation process places extremely stringent requirements on the height and tolerances of the MEMS substrate. Even minute deviations in the height of the gold wire can lead to short circuits or poor acoustic performance consistency, increasing the complexity of the manufacturing process and operating costs. Summary of the Invention

[0007] The purpose of this application is to provide a circular capacitive MEMS microphone packaging structure and process, which adopts a PCB redesigned into a circle and matched with a circular shell, thereby increasing the back cavity space of the MEMS capacitive chip, optimizing the SNR signal-to-noise ratio, simplifying the manufacturing process, reducing the production cost, and making the product structure more compact, which is conducive to the miniaturization of the product.

[0008] To achieve the above-mentioned objectives, the technical solution adopted in this application is as follows: In a first aspect, embodiments of this application provide a circular capacitive MEMS microphone packaging structure, including: The PCB substrate adopts a circular structure design, and through holes are opened on the PCB substrate at the mounting positions of the MEMS capacitive chip so as to form a front cavity with the built-in cavity of the MEMS capacitive chip. ASIC integrated chips are mounted on a PCB substrate; MEMS capacitive chips are mounted on a PCB substrate and covered with through holes, and are electrically connected to an ASIC integrated chip. A circular outer shell is placed around the perimeter of the PCB substrate and fixedly connected to the PCB substrate to form a circular extended back cavity that surrounds the MEMS capacitive chip and the ASIC integrated chip. The front cavity and the circular extended back cavity together constitute the acoustic cavity of the microphone.

[0009] In some embodiments, the surface of the ASIC integrated chip is covered with COB adhesive to protect the chip.

[0010] In some embodiments, the MEMS capacitive chip and the ASIC integrated chip are bridged by gold wires, and the ASIC integrated chip and the solder joints on the PCB substrate are bridged by gold wires.

[0011] In some embodiments, solder paste or conductive silver paste is used at the solder joints on the PCB substrate.

[0012] Secondly, embodiments of this application provide a packaging process for the circular capacitive MEMS microphone packaging structure as described above, including the following steps: (1) Apply adhesive to a circular PCB substrate, mount the ASIC integrated chip, and bake to cure it. (2) Apply adhesive to the corresponding position of the through hole on the PCB substrate (1), mount the MEMS capacitive chip and bake and cure it. (3) Use gold wire to bridge the MEMS capacitive chip and the ASIC integrated chip, and bridge the ASIC integrated chip and the solder joint of the PCB substrate to make them conductive. (4) Apply COB adhesive to the surface of the ASIC integrated chip to protect the chip; (5) Apply solder to the solder ring around the product; (6) Perform SMT mounting of the circular shell and reflow soldering to fix the circular shell to the PCB substrate, forming a circular extended back cavity.

[0013] In some embodiments, step (6) is followed by: (7) Marking on the surface of the circular outer shell; (8) Cut and sort the finished PCB products to form individual products; (9) Test individual products.

[0014] Compared with the prior art, the beneficial effects of the embodiments of this application are: This application provides a circular capacitive MEMS microphone packaging structure and process. The design is carried out on the PCB substrate, changing the PCB structure to a circular shape and matching it with a circular shell. This increases the back cavity space of the MEMS capacitive chip, which facilitates performance improvement and increases the SNR signal-to-noise ratio. The packaging reduces the stringent requirements on the height of the chip glue, lowers product operating costs, simplifies the packaging process, and optimizes product performance. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the PCB structure of the present invention.

[0017] Figure 2 A schematic diagram of the outer shell structure of the process packaged according to the present invention.

[0018] Figure 3 A schematic diagram of the product structure packaged using the process of this invention.

[0019] Figure 4 This is a cross-sectional schematic diagram of the product packaged using the process of this invention.

[0020] Illustration: 1. PCB substrate; 2. ASIC integrated chip; 3. MEMS capacitive chip; 4. Housing; 5. Surface mount adhesive; 51. Adhesive connection point; 6. Gold wire; 7. COB adhesive; 8. Back cavity; 9. Front cavity. Detailed Implementation

[0021] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0022] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0023] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0024] To illustrate the technical solution described in this application, specific embodiments are provided below.

[0025] Please see Figures 1 to 4 As shown, this application embodiment provides a circular capacitive MEMS microphone packaging structure, including: The PCB substrate 1 adopts a circular structure design, and through holes are provided on the PCB substrate 1 at the mounting positions of the MEMS capacitive chip 3 to form the front cavity 9 with the built-in cavity of the MEMS capacitive chip 3. By changing the traditional rectangular PCB substrate 1 to a circular shape, space utilization can be improved. At the same time, the geometric symmetry of the circle helps the sound waves to be distributed more evenly when entering the front cavity 9, reducing acoustic resonance. The circular design of the front cavity 9 not only serves as the sound source entrance, but also utilizes geometric symmetry to make the sound pressure distribution more even, avoiding acoustic impedance fluctuations caused by the rectangular corners.

[0026] ASIC integrated chip 2 is mounted on PCB substrate 1; MEMS capacitive chip 3 is mounted on PCB substrate 1 and covered with through holes, and is electrically connected to ASIC integrated chip 2. A circular housing 4 is fitted around the perimeter of the PCB substrate 1 and fixedly connected to it, forming a circular extended cavity 8 that surrounds the MEMS capacitive chip 3 and the ASIC integrated chip 2. The combination of the circular housing 4 and the circular substrate 1 provides a larger internal volume than a rectangular package within the same projected area, thus significantly increasing the space of the cavity 8. According to acoustic principles, the increased volume of the cavity 8 effectively reduces air damping, thereby significantly optimizing the signal-to-noise ratio (SNR) and improving microphone sensitivity.

[0027] The front cavity 9 and the circular extended back cavity 8 together constitute the acoustic cavity of the microphone.

[0028] In some embodiments, the surface of the ASIC integrated chip 2 is covered with COB adhesive 7 to protect the chip. The COB adhesive 7 not only provides a physical barrier for the sensitive ASIC integrated chip 2, preventing damage to the chip from moisture, dust and mechanical impact, but also effectively prevents the gold wires from being broken by external forces during subsequent processes or use, significantly enhancing the reliability and lifespan of the product.

[0029] In some embodiments, the MEMS capacitive chip 3 and the ASIC integrated chip 2 are bridged by gold wire 6, and the solder joints of the ASIC integrated chip 2 and the PCB substrate 1 are bridged by gold wire 6. The gold wire interconnects the MEMS capacitive chip 3, the ASIC integrated chip 2, and the PCB substrate 1, ensuring stable signal transmission. Due to the increased space of the circular extended back cavity 8, this design reduces the stringent limitations on the arc height of the gold wire. Specifically, the average distance between the dome or sidewall of the circular housing 4 and the chip edge increases, effectively increasing the safety margin of the gold wire 6 and reducing the risk of short circuits caused by touching the housing, thereby improving production yield.

[0030] In some embodiments, solder paste or conductive silver paste is used at the solder joints on the PCB substrate 1.

[0031] This application embodiment also provides a packaging process for the circular capacitive MEMS microphone packaging structure as described above, including the following steps: (1) Apply adhesive (e.g., patch adhesive 5) to a circular PCB substrate 1, mount the ASIC integrated chip 2, and bake and cure it. (2) Apply adhesive (e.g., patch fixing adhesive 5, adhesive connection position 51) to the corresponding position of the through hole of PCB substrate 1, mount MEMS capacitive chip 3 and bake to cure; thanks to the fault tolerance space of the circular back cavity design, this process reduces the stringent requirements on the height and tolerance of MEMS base adhesive, simplifies the debugging process of dispensing equipment, and directly reduces the operating cost.

[0032] (3) The MEMS capacitive chip 3 and the ASIC integrated chip 2 are bridged using gold wire 6, and the solder joints of the ASIC integrated chip 2 and the PCB substrate 1 are bridged and connected; for example, solder paste or conductive silver paste is used at the solder joints. Using high-performance solder paste or conductive silver paste at the solder joint connection can ensure low impedance electrical connection and reduce signal loss during transmission; at the same time, conductive silver paste has a certain buffering performance, which can absorb the stress caused by thermal expansion and contraction and prevent the solder joint from cracking in thermal cycling.

[0033] (4) Apply adhesive (e.g., COB adhesive 7) to the surface of the ASIC integrated chip 2 to protect the chip; (5) Apply solder to the solder ring around the product; (6) After applying solder, the circular housing 4 is mounted by SMT and then cured by reflow soldering to fix the circular housing 4 to the PCB substrate 1, forming a circular extended back cavity 8. The circular housing 4 is fixed by applying solder and reflow soldering. Reflow soldering can ensure the acoustic sealing effect of the circular housing 4 and prevent sound leakage from causing a drop in the signal-to-noise ratio. Combined with SMT automatic placement, it is also more suitable for high-efficiency mass production.

[0034] In some embodiments, step (6) is followed by: (7) Marking on the surface of the circular outer shell 4; (8) Cut and sort the finished PCB products to form individual products; (9) Test individual products.

[0035] This solution abandons the traditional rectangular design and adopts a circular package, solving the problem of balancing miniaturization and high performance. This circular layout directly improves the utilization rate of the back cavity, resulting in a significant improvement in SNR performance. At the same time, due to the increased internal space margin, the process no longer needs to be rigidly focused on parameters such as glue height, effectively improving yield and reducing operational difficulty.

[0036] In summary, the circular capacitive MEMS microphone packaging structure and process provided in this application embodiment features an expanded back cavity 8 design on a PCB substrate 1, increasing the space available for product design and placement. The PCB substrate 1 adopts a circular design, coupled with a circular outer shell 4, forming a front cavity and an expanded back cavity 8, thereby increasing the back cavity space of the MEMS capacitive chip 3 and optimizing the SNR (signal-to-noise ratio). This design simplifies the packaging process, reduces stringent requirements on chip adhesive height, and lowers production costs. Simultaneously, the product structure is more compact, facilitating product miniaturization and optimizing product performance.

[0037] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A circular capacitive MEMS microphone packaging structure, characterized in that, include: PCB substrate (1), the PCB substrate (1) adopts a circular structure design, and through holes are provided on the PCB substrate (1) at the mounting position of MEMS capacitive chip (3) so as to form a front cavity (9) with the built-in cavity of the MEMS capacitive chip (3). An ASIC integrated chip (2) is mounted on the PCB substrate (1); MEMS capacitive chip (3) is mounted on the PCB substrate (1) and covers the through hole, and is electrically connected to the ASIC integrated chip (2); A circular outer shell (4) is placed around the periphery of the PCB substrate (1) and fixedly connected to the PCB substrate (1) to form a circular extended back cavity that surrounds the MEMS capacitive chip (3) and the ASIC integrated chip (2) inside. The front cavity (9) and the circular extended back cavity (8) together constitute the acoustic cavity of the microphone.

2. The circular capacitive MEMS microphone packaging structure according to claim 1, characterized in that: The surface of the ASIC integrated chip (2) is covered with COB adhesive (7) to protect the chip.

3. The circular capacitive MEMS microphone packaging structure according to claim 1, characterized in that: The MEMS capacitive chip (3) is bridged with the ASIC integrated chip (2) by gold wire (6), and the solder joints on the ASIC integrated chip (2) and the PCB substrate (1) are bridged by gold wire (6).

4. The circular capacitive MEMS microphone packaging structure according to claim 3, characterized in that: Solder joints on the PCB substrate (1) are connected using solder paste or conductive silver paste.

5. A packaging process for a circular capacitive MEMS microphone packaging structure as described in any one of claims 1 to 4, characterized in that, Includes the following steps: (1) Apply adhesive to a circular PCB substrate (1) to mount an ASIC integrated chip (2) and bake to cure it; (2) Apply adhesive to the corresponding position of the through hole on the PCB substrate (1), mount the MEMS capacitive chip (3) and bake to cure. (3) Use gold wire (6) to bridge the MEMS capacitive chip (3) and the ASIC integrated chip (2), and bridge the solder joints of the ASIC integrated chip (2) and the PCB substrate (1) to make them conductive. (4) Apply COB adhesive (7) to the surface of the ASIC integrated chip (2) to protect the chip; (5) Apply solder to the solder ring around the product; (6) Perform SMT mounting of the circular shell (4) and reflow soldering to fix the circular shell (4) to the PCB substrate (1) to form a circular extended back cavity (8).

6. The packaging process for a circular capacitive MEMS microphone according to claim 5, characterized in that: The process includes the following after step (6): (7) Marking on the surface of the circular outer shell (4); (8) Cut and sort the finished PCB products to form individual products; (9) Test individual products.

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