Flush-mount MEMS Sensor Package with Shim Cap for Aircraft Noise Measurement
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Solution Overview
Problem
Commercial aircraft microphones face challenges in high-pressure, temperature, and moisture conditions, requiring high performance and precision, but existing sensors are costly and constrained by measurement quality, size, and power requirements, limiting their effectiveness in reducing aircraft noise.
Innovation Solution
The development of sensor packages with microelectromechanical systems (MEMS) microphones and through-silicon vias (TSVs) for backside connections, decoupling electrical and mechanical connections, and using a shim cap with epoxy film for improved flushness and thermal performance, allowing for low-cost, high-resolution, and robust noise measurement solutions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If commercial sensors are used to meet high performance requirements, then measurement precision and reliability are improved, but cost and device complexity increase
Solution Approach 1:
The sensor package is divided into distinct functional layers: sensor element, epoxy film, and shim cap. This segmentation allows each component to be optimized independently while maintaining overall performance, reducing complexity through modular design
Solution Approach 2:
An epoxy film is introduced as an intermediary layer between the sensor and substrate, and a shim cap as an intermediary between the sensor and package surface. These intermediaries decouple electrical and mechanical connections, improving measurement precision while managing complexity
2Measurement precision
If sensor size is reduced to meet spatial resolution requirements, then measurement precision is improved, but manufacturing difficulty increases
Solution Approach 1:
The sensor, epoxy film, and shim cap are pre-assembled into a integrated package structure before final installation. This preliminary assembly ensures precise positioning and alignment, enabling small sensor sizes while maintaining ease of manufacture through standardized packaging
Solution Approach 2:
The sensor is nested within the package structure with the epoxy film and shim cap providing surrounding support and alignment features. This nesting approach allows compact design with high spatial resolution while simplifying manufacturing through hierarchical assembly
3Measurement precision
If flushness is improved by using epoxy film and shim cap, then measurement precision is improved, but manufacturing complexity increases
Solution Approach 1:
The epoxy film thickness and shim cap dimensions are carefully controlled to achieve the desired flushness parameter. By optimizing these geometric parameters, high measurement precision is achieved while the manufacturing process remains manageable through standardized tolerances
4Reliability
If thermal and mechanical performance is improved by decoupling connections, then reliability is improved, but device complexity increases
Solution Approach 1:
The epoxy film serves as a mechanical intermediary that decouples the sensor from the substrate, while wire bonds provide separate electrical connection. The shim cap acts as another intermediary that isolates the sensor from package surface stresses. This multi-layer intermediary approach improves reliability by separating thermal and mechanical pathways
Solution Approach 2:
Electrical connections (wire bonds) and mechanical support (epoxy film and shim cap) are segmented into separate functional elements. This segmentation allows independent optimization of thermal and mechanical performance while managing complexity through clear functional separation
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
The solution provides a cost-effective, high-performance sensor package with improved sensitivity, noise floor, and resonant frequency, enabling precise noise measurement and reducing the impact of harsh conditions, while allowing for more accurate and efficient noise reduction in aircraft.
Implementation Method 1
the applied pressure to the shim cap and sensor during attachment can allow the epoxy to flow around the sensor
Implementation Method 2
using an epoxy film, whereby a shim cap can sit on top of the epoxy film
Implementation Method 3
using a wire bond passing through the substrate and connecting to the sensor
Data Source
AI summary
Flush mount sensor packages and packaging methods for micromachined transducers, which can be used for fluid flow measurements, are provided. A sensor package can include a substrate, a sensor mounted on a front side of the substrate, a wire bond coupled to the sensor and passing through the substrate, and a shim cap positioned around the sensor. The wire bond does not protrude above the topside of the sensor, and the shim cap and the sensor can be substantially flush.