Flip-chip PCBA packaging structure of condenser microphone and process method thereof

Abstract

The application belongs to the technical field of condenser microphones, and discloses a flip-chip PCBA packaging structure of a condenser microphone and a process method thereof, which comprises a PCB circuit board, a flip-chip, a conductive connection layer and a bottom filling layer. The PCB circuit board has an assembly surface and a welding surface. The assembly surface is provided with an external function pad, and the welding surface is provided with a circuit board gate pad. The flip-chip pad and the circuit board pad are connected in a conductive manner through a face-to-face conductive connection principle. A gate connection path, a source connection path and a drain connection path are formed through a tin paste reflow soldering conductive connection layer or a conductive glue curing conductive connection layer. The traditional metal welding wire is cancelled, the packaging height is reduced, and the packaging process is simplified. The tin paste reflow soldering forming and the conductive glue curing forming principle are used to improve the packaging adaptability under different material and process conditions. The capillary filling, curing support and stress dispersion principle of the bottom filling layer are used to improve the mechanical strength and environmental reliability of the conductive connection layer.

Description

Technical Field

[0001] This invention belongs to the field of condenser microphone technology, and particularly relates to a flip-chip PCBA packaging structure and its manufacturing process for a condenser microphone. Background Technology

[0002] Condenser microphones are widely used in mobile phones, headphones, smart speakers, automotive electronics, medical devices, and voice recognition devices. Internally, they typically require an electrical connection between the microphone preamplifier chip and the PCB circuit board, enabling the weak electrical signal generated by the microphone sensor to be processed and output. As electronic products move towards thinner, smaller, and more automated production, microphone PCBA packaging structures need to further reduce overall height, simplify packaging processes, and improve connection reliability. Therefore, a flip-chip PCBA packaging structure and its manufacturing process for condenser microphones are needed, replacing traditional metal wire bonding connections through face-to-face conductive connections between chip pads and circuit board pads.

[0003] In existing condenser microphone PCBA packaging, the preamplifier chip is usually connected to the PCB circuit board via metal bonding wires. The bonding wires require reserved arc height and bonding wire space, which increases the overall thickness of the package and is not conducive to the design of ultra-thin microphone products. At the same time, the bonding wire process has high requirements for equipment precision, solder joint consistency and working environment, and is prone to defects such as cold solder joints, broken wires, collapsed wires and bonding wire misalignment, which affect the stability of mass production.

[0004] In addition, traditional wire bonding introduces additional parasitic inductance and resistance, which can easily affect the weak signal transmission quality of condenser microphone preamplifier chips. At the same time, the wires and solder joints are exposed in the package space and are prone to fatigue failure when subjected to vibration, drops, temperature cycling and moisture intrusion, resulting in insufficient long-term reliability of microphone PCBA. Summary of the Invention

[0005] This invention provides a flip-chip PCBA packaging structure and process method for a condenser microphone, which solves the technical problems of existing condenser microphone PCBA packaging, which require metal wire bonding between the chip and the circuit board, resulting in large package thickness, complex wire bonding process, high parasitic parameters of the wire bonding, insufficient solder joint consistency, and unstable reliability in mass production.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A flip-chip PCBA package structure for a condenser microphone includes a PCB circuit board, a flip-chip, a conductive interconnect layer, and an underfill layer.

[0007] The PCB circuit board has an assembly side and a soldering side. The assembly side is provided with external functional pads, and the soldering side is provided with a circuit board gate pad, a circuit board source pad, and a circuit board drain pad. The circuit board source pad and the circuit board drain pad are electrically connected to the external functional pads on the assembly side through metallized through-holes, respectively. The circuit board gate pad is electrically connected to the grounding copper frame on the PCB circuit board.

[0008] The flip-chip is a capacitive microphone preamplifier chip. The flip-chip has a chip bonding surface facing the bonding surface of the PCB circuit board. The chip bonding surface is provided with a chip gate pad, a chip source pad, and a chip drain pad. The chip gate pad, chip source pad, and chip drain pad are respectively positioned opposite to the circuit board gate pad, circuit board source pad, and circuit board drain pad.

[0009] The conductive connection layer is disposed between the flip-chip and the PCB circuit board. The conductive connection layer connects the chip gate pad to the circuit board gate pad, the chip source pad to the circuit board source pad, and the chip drain pad to the circuit board drain pad, thereby forming a gate connection path, a source connection path, and a drain connection path between the flip-chip and the PCB circuit board. The conductive connection layer includes one of a solder paste reflow conductive connection layer and a conductive adhesive cured conductive connection layer.

[0010] The bottom filler layer fills the gap between the flip-chip and the PCB circuit board, covers the outer side of the conductive connection layer, and contacts both the flip-chip and the PCB circuit board. No metal bonding wires are provided between the flip-chip and the PCB circuit board; the flip-chip is directly electrically connected to the PCB circuit board through the conductive connection layer.

[0011] Furthermore, the PCB circuit board is a double-sided circuit board. The component side is provided with external source pads and external drain pads, and the soldering side is provided with gate pads, source pads, and drain pads. The source pads are electrically connected to the external source pads through a first metallized via, and the drain pads are electrically connected to the external drain pads through a second metallized via.

[0012] Furthermore, the flip-chip integrates an RF anti-interference filter circuit, an amplifier circuit, a compensation circuit, and an electrostatic protection circuit; the chip gate pad is connected to the input terminal of the RF anti-interference filter circuit, the chip source pad is connected to the common ground terminal inside the flip-chip, and the chip drain pad is connected to the output terminal of the amplifier circuit.

[0013] Furthermore, the solder paste reflow soldering conductive connection layer is formed by reflow soldering solder paste applied to the gate pad, source pad, and drain pad of the circuit board; the conductive adhesive cured conductive connection layer is formed by curing conductive adhesive applied to the gate pad, source pad, and drain pad of the circuit board.

[0014] Furthermore, the bottom filler layer is an epoxy resin bottom filler layer, which is disposed between the flip-chip and the PCB circuit board soldering surface, and is covered with a solder paste reflow soldering conductive connection layer or a conductive adhesive cured conductive connection layer.

[0015] A process method for a flip-chip PCBA package structure of a condenser microphone includes circuit board cleaning, die bonding, die bonding machine identification, solder or adhesive dispensing, die bonding alignment, connection forming, adhesive filling, heat curing, testing, and shipping. Through visual identification and die bonding alignment, the chip gate pad, chip source pad, and chip drain pad are aligned with the circuit board gate pad, circuit board source pad, and circuit board drain pad, respectively. A solder paste reflow soldering conductive connection layer is formed through reflow soldering, or a conductive adhesive curing conductive connection layer is formed through curing. Finally, a bottom filler layer is used to cover and support the outer side of the conductive connection layer.

[0016] Through the above technical solution, the present invention transforms the traditional metal wire bonding connection into a face-to-face conductive connection between the chip pad and the circuit board pad. The conductive connection layer is formed by reflow soldering of solder paste or curing of conductive adhesive to form the gate connection path, source connection path and drain connection path. The bottom filler layer improves mechanical support and environmental protection capabilities, thereby achieving thinner, wire-free, automated production and improved connection reliability of the capacitive microphone PCBA package.

[0017] The beneficial effects of this invention are as follows: (1) Utilizing the principle of face-to-face conductive connection between chip pads and circuit board pads, the chip gate pad, chip source pad, and chip drain pad of the flip-chip are respectively set opposite to the circuit board gate pad, circuit board source pad, and circuit board drain pad on the soldering surface of the PCB circuit board. The gate connection path, source connection path, and drain connection path are formed by solder paste reflow soldering of the conductive connection layer or conductive glue curing of the conductive connection layer. This realizes the direct electrical connection between the flip-chip and the PCB circuit board, and solves the technical problems of existing metal wire bonding connections that require reserved wire bonding space, large package thickness, and complex wire bonding process.

[0018] (2) Utilizing the principles of solder paste reflow soldering and conductive adhesive curing, when solder paste is used to reflow solder the conductive connection layer, the solder paste melts and wets the chip pads and circuit board pads to form a conductive connection through soldering, die bonding and reflow soldering. When conductive adhesive is used to cure the conductive connection layer, the conductive particles in the conductive adhesive contact the chip pads and circuit board pads to form a conductive connection through dispensing, die bonding and curing. This achieves the technical effect of selecting different connection methods according to different PCB materials, heat-sensitive packaging cavities and production conditions, and solves the technical problems of poor process adaptability and insufficient flexibility in mass production of the existing single wire bonding packaging method.

[0019] (3) By utilizing the capillary filling, curing support and stress dispersion principle of the bottom filler layer, a bottom filler layer is set in the gap between the flip-chip and the PCB circuit board. The bottom filler layer covers the solder paste reflow soldering conductive connection layer or the conductive adhesive curing conductive connection layer, and contacts the flip-chip and the PCB circuit board respectively. This achieves mechanical support, environmental isolation and stress buffering for the conductive connection layer, and solves the technical problems of existing wire bonding and exposed solder joints being prone to fatigue failure and insufficient connection reliability under vibration, drop, temperature cycling and moisture environment. Attached Figure Description

[0020] The accompanying drawings are provided to further understand the present invention and form part of the specification. They are used together with the embodiments of the present invention to explain the invention and do not constitute a limitation thereof.

[0021] Figure 1 This is a schematic diagram of the overall structure of the microphone PCBA proposed in this invention; Figure 2 This is a front layout diagram of the PCB proposed in this invention; Figure 3 This is a reverse layout diagram of the PCB proposed in this invention; Figure 4 This is a schematic diagram of the alignment between the chip and the PCB proposed in this invention; Figure 5 This is a flowchart of the flip-chip bonding packaging process proposed in this invention. Detailed Implementation

[0022] Example 1, see Figures 1-5 The present invention provides a flip-chip PCBA packaging structure and process method for a capacitive microphone. The flip-chip PCBA packaging structure includes a PCB circuit board, a flip-chip, a conductive connection layer and a bottom filler layer. The PCB circuit board has an assembly side and a soldering side. The assembly side is provided with external functional pads, and the soldering side is provided with a circuit board gate pad, a circuit board source pad, and a circuit board drain pad. The circuit board source pad and the circuit board drain pad are electrically connected to the external functional pads on the assembly side through metallized through-holes, and the circuit board gate pad is electrically connected to the grounding copper frame on the PCB circuit board. The flip-chip is a capacitive microphone preamplifier chip. The flip-chip has a chip bonding surface facing the PCB circuit board bonding surface. The chip bonding surface is provided with a chip gate pad, a chip source pad, and a chip drain pad. The chip gate pad, chip source pad, and chip drain pad are respectively positioned opposite to the circuit board gate pad, circuit board source pad, and circuit board drain pad. The conductive connection layer is disposed between the flip-chip and the PCB circuit board. The conductive connection layer connects the chip gate pad to the circuit board gate pad, the chip source pad to the circuit board source pad, and the chip drain pad to the circuit board drain pad, thereby forming a gate connection path, a source connection path, and a drain connection path between the flip-chip and the PCB circuit board. The conductive connection layer includes one of a solder paste reflow soldering conductive connection layer and a conductive adhesive cured conductive connection layer; the solder paste reflow soldering conductive connection layer is formed by reflow soldering solder paste applied to the gate pad, source pad, and drain pad of the circuit board; the conductive adhesive cured conductive connection layer is formed by curing conductive adhesive applied to the gate pad, source pad, and drain pad of the circuit board. The bottom filler layer fills the gap between the flip-chip and the PCB circuit board. The bottom filler layer covers the outside of the conductive connection layer and contacts the flip-chip and the PCB circuit board respectively, so that the flip-chip is fixed on the soldering surface of the PCB circuit board. No metal bonding wires are placed between the flip-chip and the PCB circuit board. The flip-chip is directly electrically connected to the PCB circuit board through a conductive connection layer, which transforms the electrical connection completed by two metal bonding wires in traditional packaging into a face-to-face conductive connection between the chip pad and the circuit board pad.

[0023] With the above structure, the present invention mounts the condenser microphone preamplifier chip on the PCB circuit board in a flip-chip manner, so that the chip pads directly face the circuit board pads, and achieves electrical connection by reflow soldering the conductive connection layer with solder paste or curing the conductive connection layer with conductive adhesive. This reduces the wire bonding process, reduces the package height, reduces wire bonding parasitic parameters, and improves the miniaturization of the condenser microphone PCBA package and the consistency of mass production.

[0024] Example 2: This example is based on all the above examples, and the PCB circuit board specifically includes: The PCB circuit board is a double-sided circuit board. The component side of the PCB circuit board is provided with external pads for the source and external pads for the drain. The soldering side of the PCB circuit board is provided with gate pads, source pads and drain pads. The source pad of the circuit board is electrically connected to the external source pad of the circuit board through the first metallized through-hole, and the drain pad of the circuit board is electrically connected to the external drain pad of the circuit board through the second metallized through-hole. The circuit board gate pad is connected to the grounding copper frame on the PCB circuit board. The grounding copper frame extends along the edge of the PCB circuit board and forms a large grounding area, so that the circuit board gate pad has a low impedance grounding path. The circuit board gate pad, circuit board source pad, and circuit board drain pad are located in the chip mounting area on the soldering surface of the PCB circuit board. The circuit board gate pad, circuit board source pad, and circuit board drain pad are arranged along the length of the PCB circuit board and correspond to the chip gate pad, chip source pad, and chip drain pad of the flip-chip respectively. The PCB circuit board uses FR4 material, and the thickness of the PCB circuit board is set to 0.25mm to 0.45mm. An OSP anti-oxidation layer is set on the surface of the PCB circuit board, and the OSP anti-oxidation layer covers the gate pad, source pad, drain pad, external source pad, and external drain pad of the circuit board.

[0025] Example 3: This example is based on all the above examples, and the flip-chip specifically includes: The flip-chip is a fully integrated condenser microphone preamplifier chip, which integrates radio frequency anti-interference filtering circuit, amplifier circuit, compensation circuit and electrostatic protection circuit. The chip gate pad, chip source pad, and chip drain pad are disposed on the chip bonding surface of the flip-chip. The chip gate pad is connected to the input terminal of the radio frequency anti-interference filter circuit, the chip source pad is connected to the common ground terminal inside the flip-chip, and the chip drain pad is connected to the output terminal of the amplifier circuit. The chip gate pad, chip source pad, and chip drain pad are all circular pads. The chip gate pad, chip source pad, and chip drain pad are arranged along the length of the flip-chip. The center-to-center distance between the chip gate pad, chip source pad, and chip drain pad is the same as the center-to-center distance between the circuit board gate pad, circuit board source pad, and circuit board drain pad. The gate pad of the flip-chip is connected to the gate pad of the circuit board through a conductive connection layer to form a gate grounding path; the source pad of the chip is connected to the source pad of the circuit board through a conductive connection layer to form a source output path; and the drain pad of the chip is connected to the drain pad of the circuit board through a conductive connection layer to form a drain output path. The flip-chip integrates the signal processing circuitry required for the preamplifier of the capacitive microphone, eliminating the need for external amplification resistors, external filter capacitors, and external electrostatic protection devices on the PCB board.

[0026] Example 4: This example is based on all the above examples. The solder paste reflow soldering conductive connection layer specifically includes: The solder paste reflow soldering conductive connection layers are respectively located between the chip gate pad and the circuit board gate pad, between the chip source pad and the circuit board source pad, and between the chip drain pad and the circuit board drain pad. Apply solder paste to the gate pad, source pad, and drain pad of the PCB, respectively, with the applied solder paste located in the center area of ​​the corresponding PCB pad; move the flip-chip to the top of the PCB soldering surface, aligning the chip gate pad, chip source pad, and chip drain pad with the PCB gate pad, PCB source pad, and PCB drain pad, respectively. After the flip-chip is pressed and mounted, the solder paste is located between the chip pads and the circuit board pads that are set opposite to each other. The flip-chip and the PCB circuit board are then reflow soldered. The solder paste melts and wets the chip pads and the circuit board pads, and forms a solder paste reflow soldering conductive connection layer after cooling. The solder paste reflow soldering conductive connection layer simultaneously forms electrical and mechanical connections between the chip pads and the circuit board pads that are arranged opposite to each other, so that the flip-chip is fixed to the PCB circuit board by three face-to-face solder joints. The outer edge of the solder paste reflow soldering conductive connection layer is located within the corresponding circuit board pad area, and an insulating gap is maintained between adjacent solder paste reflow soldering conductive connection layers to prevent short circuits between the gate connection path, source connection path and drain connection path.

[0027] Furthermore, the solder paste is SAC305 lead-free solder paste, the solder paste application amount is set to 0.1mg to 0.3mg, the reflow peak temperature is set to 245℃ to 250℃, and the reflow time is set to 30 seconds to 60 seconds.

[0028] Regarding parameter adjustments: Step 1: When the spacing between adjacent circuit board pads decreases, reduce the amount of solder paste applied and reduce the diameter of the solder paste application to ensure that the conductive connection layer of the solder paste reflow soldering does not cross the insulation area between adjacent circuit board pads. Step 2: When the alignment deviation between the flip-chip and the PCB increases, increase the size difference between the diameter of the PCB pad and the diameter of the chip pad, and maintain the insulation distance between adjacent PCB pads. Step 3: When the solder joint height after reflow soldering is lower than the chip support gap requirement, increase the amount of solder paste applied so that the solder paste reflow soldering conductive connection layer can stably support the flip-chip. Step 4: When cold solder joints occur after reflow soldering, increase the holding time of the peak reflow temperature and strengthen the cleaning treatment of the circuit board pads.

[0029] Example 5: This example is based on all the above examples. The conductive adhesive cured conductive connection layer specifically includes: The conductive adhesive cured conductive connection layer is located between the chip gate pad and the circuit board gate pad, between the chip source pad and the circuit board source pad, and between the chip drain pad and the circuit board drain pad. Apply conductive adhesive to the gate pad, source pad, and drain pad of the circuit board, respectively, with the applied conductive adhesive located in the center area of ​​the corresponding circuit board pad; move the flip-chip to the soldering surface of the PCB circuit board, so that the gate pad, source pad, and drain pad of the chip are respectively pressed with the corresponding conductive adhesive. The flip-chip and PCB circuit board after mounting are cured so that the conductive particles in the conductive adhesive come into contact with the chip pads and the circuit board pads respectively, and a conductive adhesive cured conductive connection layer is formed after curing. The conductive adhesive curing conductive connection layer forms an electrical connection between the chip pad and the circuit board pad, and forms a mechanical fixation through the cured adhesive structure, enabling the flip-chip to be connected to the PCB circuit board under low-temperature packaging conditions. The outer edge of the conductive adhesive-cured conductive connection layer is located within the corresponding circuit board pad area. An insulating gap is maintained between adjacent conductive adhesive-cured conductive connection layers to prevent the conductive adhesive from spreading and causing short circuits between the gate connection path, source connection path, and drain connection path.

[0030] Furthermore, the conductive adhesive is a silver-filled conductive adhesive, and the curing temperature of the conductive adhesive is set to 120°C to 150°C, and the curing time is set to 30 minutes to 60 minutes.

[0031] Regarding parameter adjustments: Step 1: When the amount of conductive adhesive applied is too large, reduce the dispensing pressure and dispensing time to ensure that the conductive adhesive curing conductive connection layer remains within the circuit board pad area. Step 2: When the contact resistance of the conductive bonding layer increases after the conductive adhesive cures, increase the flip-chip mounting pressure to ensure that the conductive particles make full contact with the chip pads and circuit board pads. Step 3: When the PCB circuit board material cannot withstand the high temperature of reflow soldering, use conductive adhesive to cure the conductive connection layer and reduce the curing temperature; Step 4: When the microphone encapsulation cavity is sensitive to thermal stress, flexible conductive adhesive is used to allow the conductive adhesive to cure and the conductive connection layer to absorb the thermal expansion difference between the flip-chip and the PCB circuit board.

[0032] Example 6: This example is based on all the above examples, and the bottom filling layer specifically includes: The bottom filler layer is an epoxy resin bottom filler layer, which is placed between the flip-chip and the PCB circuit board soldering surface and covered with a solder paste reflow soldering conductive connection layer or a conductive adhesive cured conductive connection layer. The bottom filler layer enters the gap between the flip-chip and the PCB circuit board through capillary action, and fills the surrounding areas between the chip gate pad and the circuit board gate pad, between the chip source pad and the circuit board source pad, and between the chip drain pad and the circuit board drain pad. After the bottom filler layer is cured, it comes into contact with the chip bonding surface of the flip-chip, the bonding surface of the PCB circuit board, and the outer surface of the conductive connection layer to form a support and protection structure. The bottom filler layer blocks external moisture, dust and flux residue from the outside of the conductive connection layer and disperses the thermal and mechanical stress between the flip-chip and the PCB circuit board. Furthermore, the bottom filling layer is made of epoxy resin-based filler, with the viscosity of the epoxy resin-based filler set to 5000cps to 15000cps, the dispensing amount set to 0.5mg to 2.0mg, the curing temperature set to 120℃ to 150℃, and the curing time set to 30 minutes to 60 minutes.

[0033] With the above structure, the bottom filler layer can improve the bonding strength between the flip-chip and the PCB circuit board, and reduce the probability of fatigue cracking of the conductive connection layer caused by drop, vibration and temperature cycling.

[0034] Example 7: This example is based on all the above examples. The process method for the flip-chip PCBA package structure includes: Step 1, Circuit Board Cleaning: Clean the PCB circuit board to remove oil, dust and oxides from its surface, resulting in a cleaned PCB circuit board. Step 2, Place the PCB board on the die bonder; Place the cleaned PCB board on the die bonder platform with the soldering side of the PCB board facing upwards, and fix the PCB board by vacuum adsorption. Step 3, die bonder identification; using a CCD vision system to identify the gate pads, source pads, and drain pads on the PCB board soldering surface, and obtain the center coordinates of the board pads. Step 4: Apply solder or adhesive. When using solder paste to reflow solder the conductive connection layer, apply solder paste to the gate pad, source pad, and drain pad of the circuit board using a soldering device. When using conductive adhesive to cure the conductive connection layer, apply conductive adhesive to the gate pad, source pad, and drain pad of the circuit board using an adhesive dispensing device. Step 5, die bonding alignment; the flip-chip is picked up by the automatic die bonder, and the chip gate pad, chip source pad and chip drain pad are identified by the vision alignment system. The chip gate pad, chip source pad and chip drain pad are aligned with the circuit board gate pad, circuit board source pad and circuit board drain pad respectively. Step 6, Connection and Forming; When using solder paste reflow soldering conductive connection layer, the flip-chip and PCB circuit board after mounting are reflow soldered to form solder paste reflow soldering conductive connection layer; When using conductive adhesive to cure conductive connection layer, the flip-chip and PCB circuit board after mounting are cured to form conductive adhesive cured conductive connection layer. Step 7, dispensing and filling: Apply epoxy resin-based filler to the edge of the flip chip to allow the epoxy resin-based filler to enter the gap between the flip chip and the PCB circuit board. Step 8, heat curing; heat and cure the flip-chip and PCB after dispensing to form the bottom filler layer; Step 9, Testing; Perform electrical performance testing and visual inspection on the flip-chip PCBA package structure after the bottom filler layer is formed, and obtain the test results; Step 10, Shipping: Pack and ship the flip-chip PCBA packages that have passed the test.

[0035] Example 8: This example is based on all the above examples, and the test specifically includes: Conduct continuity tests on the gate connection path, source connection path, and drain connection path respectively, and obtain the gate continuity test results, source continuity test results, and drain continuity test results. Audio performance tests were performed on the flip-chip PCBA package structure to obtain gain test results, noise test results, and total harmonic distortion test results. Electrostatic discharge (ESD) withstand tests were performed on the flip-chip PCBA package structure, and the ESD withstand test results were obtained. Visual inspection of the flip-chip PCBA package structure was performed to obtain chip offset detection results, conductive interconnect layer forming detection results, and bottom fill integrity detection results. When the gate conduction test results, source conduction test results, drain conduction test results, gain test results, noise test results, total harmonic distortion test results, electrostatic discharge tolerance test results, chip offset detection results, conductive interconnect layer forming detection results, and bottom fill integrity detection results all meet the corresponding detection thresholds, the flip-chip PCBA package structure is judged to be a qualified product. If any test result fails to meet the corresponding test threshold, the flip-chip PCBA package structure is determined to be a defective product and is removed from the shipment batch.

[0036] The above testing steps enable a comprehensive assessment of conductive connection reliability, audio performance, electrostatic protection capability, chip mounting accuracy, and underfill reliability, ensuring the stability of mass production of flip-chip PCBA packaging structures.

Claims

1. A flip-chip PCBA package structure for a condenser microphone, characterized in that: This includes the PCB circuit board, flip-chip, conductive interconnect layer, and underfill layer; The PCB circuit board has an assembly side and a soldering side. The assembly side is provided with external functional pads, and the soldering side is provided with a circuit board gate pad, a circuit board source pad, and a circuit board drain pad. The circuit board source pad and the circuit board drain pad are electrically connected to the external functional pads on the assembly side through metallized through-holes, and the circuit board gate pad is electrically connected to the grounding copper frame on the PCB circuit board. The flip-chip is a capacitive microphone preamplifier chip. The flip-chip has a chip bonding surface facing the PCB circuit board bonding surface. The chip bonding surface is provided with a chip gate pad, a chip source pad, and a chip drain pad. The chip gate pad, chip source pad, and chip drain pad are respectively positioned opposite to the circuit board gate pad, circuit board source pad, and circuit board drain pad. The conductive connection layer is disposed between the flip-chip and the PCB circuit board. The conductive connection layer connects the chip gate pad to the circuit board gate pad, the chip source pad to the circuit board source pad, and the chip drain pad to the circuit board drain pad, thereby forming a gate connection path, a source connection path, and a drain connection path between the flip-chip and the PCB circuit board. The conductive connection layer includes one of a solder paste reflow conductive connection layer and a conductive adhesive cured conductive connection layer; The bottom filler layer fills the gap between the flip-chip and the PCB circuit board, and the bottom filler layer covers the outside of the conductive connection layer and contacts the flip-chip and the PCB circuit board respectively. No metal bonding wires are provided between the flip-chip and the PCB circuit board. The flip-chip is directly electrically connected to the PCB circuit board through a conductive connection layer.

2. The flip-chip PCBA packaging structure for a capacitor microphone according to claim 1, characterized in that: The PCB circuit board is a double-sided circuit board. The component side is provided with external source pads and external drain pads, and the soldering side is provided with gate pads, source pads, and drain pads. The source pads are electrically connected to the external source pads through a first metallized via, and the drain pads are electrically connected to the external drain pads through a second metallized via. The gate pads are connected to a grounding copper frame on the PCB circuit board, and the grounding copper frame extends along the edge of the PCB circuit board to form a grounding area.

3. The flip-chip PCBA packaging structure for a capacitor microphone according to claim 1, characterized in that: The flip-chip integrates an RF anti-interference filter circuit, an amplifier circuit, a compensation circuit, and an electrostatic protection circuit. The chip gate pad is connected to the input terminal of the RF anti-interference filter circuit, the chip source pad is connected to the common ground terminal inside the flip-chip, and the chip drain pad is connected to the output terminal of the amplifier circuit. The chip gate pad, chip source pad, and chip drain pad are all circular pads and are arranged along the length of the flip-chip.

4. The flip-chip PCBA packaging structure for a capacitor microphone according to claim 1, characterized in that: The solder paste reflow soldering conductive connection layer is located between the chip gate pad and the circuit board gate pad, the chip source pad and the circuit board source pad, and the chip drain pad and the circuit board drain pad, respectively. The solder paste reflow soldering conductive connection layer is formed by reflow soldering solder paste applied to the circuit board gate pad, circuit board source pad and circuit board drain pad, and simultaneously forms electrical and mechanical connections between the chip pad and the circuit board pad that are arranged opposite to each other.

5. The flip-chip PCBA packaging structure for a capacitor microphone according to claim 1, characterized in that: The conductive adhesive cured conductive connection layer is located between the chip gate pad and the circuit board gate pad, the chip source pad and the circuit board source pad, and the chip drain pad and the circuit board drain pad, respectively. The conductive adhesive cured conductive connection layer is formed by curing conductive adhesive applied to the circuit board gate pad, circuit board source pad and circuit board drain pad. The conductive particles in the conductive adhesive cured conductive connection layer contact the chip pad and the circuit board pad, respectively.

6. The flip-chip PCBA package structure for a capacitor microphone according to claim 1, characterized in that: The bottom filler layer is an epoxy resin bottom filler layer, which is placed between the flip-chip and the PCB circuit board soldering surface and covered with a solder paste reflow soldering conductive connection layer or a conductive adhesive cured conductive connection layer. After the bottom filler layer cures, it comes into contact with the chip soldering surface of the flip-chip, the soldering surface of the PCB circuit board, and the outer surface of the conductive connection layer, forming a support and protection structure.

7. A process method for a flip-chip soldered PCBA package structure of a condenser microphone, characterized in that, Includes the following steps: Step 1, Circuit Board Cleaning: Clean the PCB circuit board to remove oil, dust and oxides from its surface, resulting in a cleaned PCB circuit board. Step 2, Place the PCB board on the die bonder; Place the cleaned PCB board on the die bonder platform with the soldering side of the PCB board facing upwards, and fix the PCB board by vacuum adsorption. Step 3, die bonder identification; using a CCD vision system to identify the gate pads, source pads, and drain pads on the PCB board soldering surface, and obtain the center coordinates of the board pads. Step 4: Apply solder or adhesive. When using solder paste to reflow solder the conductive connection layer, apply solder paste to the gate pad, source pad, and drain pad of the circuit board using a soldering device. When using conductive adhesive to cure the conductive connection layer, apply conductive adhesive to the gate pad, source pad, and drain pad of the circuit board using an adhesive dispensing device. Step 5, die bonding alignment; the flip-chip is picked up by the automatic die bonder, and the chip gate pad, chip source pad and chip drain pad are identified by the vision alignment system. The chip gate pad, chip source pad and chip drain pad are aligned with the circuit board gate pad, circuit board source pad and circuit board drain pad respectively. Step 6, Connection and Forming; When using solder paste reflow soldering conductive connection layer, the flip-chip and PCB circuit board after mounting are reflow soldered to form solder paste reflow soldering conductive connection layer; When using conductive adhesive to cure the conductive connection layer, the flip-chip and PCB circuit board after mounting are cured to form a conductive adhesive-cured conductive connection layer. Step 7, dispensing and filling: Apply epoxy resin-based filler to the edge of the flip chip to allow the epoxy resin-based filler to enter the gap between the flip chip and the PCB circuit board. Step 8, heat curing; heat and cure the flip-chip and PCB after dispensing to form the bottom filler layer; Step 9, Testing; Perform electrical performance testing and visual inspection on the flip-chip PCBA package structure after the bottom filler layer is formed, and obtain the test results; Step 10, Shipping: Pack and ship the flip-chip PCBA packages that have passed the test.

8. The process method for a flip-chip soldered PCBA packaging structure of a capacitor microphone according to claim 7, characterized in that: The tests include continuity testing, audio performance testing, electrostatic discharge tolerance testing, and appearance inspection. The continuity test yields gate continuity test results, source continuity test results, and drain continuity test results. Audio performance testing yields gain test results, noise test results, and total harmonic distortion test results. The electrostatic tolerance test yields the electrostatic tolerance test results. Visual inspection yields results for chip offset detection, conductive interconnect layer molding detection, and bottom fill integrity detection. When the gate conduction test result, source conduction test result, drain conduction test result, gain test result, noise test result, total harmonic distortion test result, electrostatic discharge tolerance test result, chip offset detection result, conductive interconnect layer forming detection result, and bottom fill integrity detection result all meet the corresponding detection thresholds, the flip-chip PCBA package structure is judged to be a qualified product.

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