Capacitive Microphone Integrated PCB Cavity
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Solution Overview
Problem
The high costs associated with silicon microfabrication and packaging limit the cost-cutting measures for silicon microfabrication-based microphones, making it difficult to compete with conventional electret condenser microphones in terms of price and performance in high-volume consumer electronic products.
Innovation Solution
The use of PCB-fabrication technology to create a low-cost capacitive microphone with a surface micromachined diaphragm separated from a porous backplate on a PCB substrate, eliminating the need for wire bonds and allowing for a larger diaphragm, which improves sensitivity and reduces noise, while also incorporating interface electronics within the package to reduce costs and enhance reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If silicon microfabrication is used to manufacture microphones, then manufacturing precision and device performance are improved, but fabrication cost and packaging cost increase significantly
Solution Approach 1:
The patent combines the microphone diaphragm, cavity structure, and packaging housing into a single integrated PCB assembly. The PCB serves simultaneously as the structural housing, the cavity wall, and the mounting substrate for the diaphragm, eliminating the need for separate packaging steps and reducing overall manufacturing complexity despite using precision PCB fabrication processes
Solution Approach 2:
The PCB substrate performs multiple functions: it provides the acoustic cavity enclosure, forms the structural housing walls, serves as the mounting platform for the diaphragm, and provides electrical connection pathways. This multi-functionality reduces the number of separate components needed and simplifies the overall manufacturing process
2Reliability
If conventional ECM packaging is used with base, wall, and lid structure, then device protection is improved, but packaging size and cost increase
Solution Approach 1:
The traditional separate base, wall, and lid components are merged into a single PCB structure. The PCB itself forms the protective enclosure with integrated cavity walls and mounting surfaces, reducing the total component count and assembly complexity while maintaining protective functionality
Solution Approach 2:
The PCB serves as both the structural protective housing and the functional mounting platform for the microphone elements. This eliminates the need for separate packaging components and reduces overall package volume while maintaining device protection
3Reliability
If wire bonds are used to connect diaphragm to interface electronics, then electrical connection reliability is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The wire bonding step is completely extracted from the manufacturing process. Instead of using wire bonds to connect the diaphragm to interface electronics, the PCB provides direct electrical connection pathways through its conductive traces, eliminating the need for separate wire bonding operations and reducing assembly complexity
Solution Approach 2:
The PCB acts as an intermediary that provides both mechanical support and electrical connection between the diaphragm and interface electronics. The conductive traces on the PCB serve as the electrical pathway, replacing the need for wire bonds while maintaining reliable electrical connection
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach results in a lower-cost, high-sensitivity microphone with reduced noise floor and improved reliability, capable of withstanding higher operating temperatures and lead-free solder re-flow cycles, offering superior performance compared to traditional silicon microfabrication-based devices.
Implementation Method 1
capacitive microphone
Implementation Method 2
surface micromachined diaphragm 10 is separated from a porous backplate 11
Data Source
AI summary
A capacitive microphone and method of fabricating the same are provided. One or more holes can be formed in a first printed circuit board (PCB). A diaphragm can be surface micromachined onto an interior surface of the first PCB at a region having the one or more holes. Interface electronics can also be interconnected to the interior surface of the PCB. One or more spacer PCBs can be attached to a second PCB to the first PCB, such that appropriate interconnections between interconnect vias are made. The second PCB and first PCB with spacers in between can be attached so as to create a cavity in which the diaphragm and interface electronics are located.