MEMS Sensor Lead Frame Recess for Signal-to-Noise Optimization
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Solution Overview
Problem
Conventional transducers face limitations in sensitivity due to signal interference from various sources such as the size of the sound inlet opening, air flow, impedance of the converter circuit, and microphone back volume, which affect the accuracy of converting diaphragm deflection into a voltage signal.
Innovation Solution
A micro-electro-mechanical system (MEMS) sensor structure incorporating a lead frame with a recess and a MEMS sensor coupled over the recess to form a chamber, along with an integrated circuit and encapsulation layer, is designed to enhance signal-to-noise ratio by optimizing the back volume without increasing the overall height, and includes a spacer structure to prevent encapsulation deposition in critical areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the back volume is increased to improve signal-to-noise ratio, then the sensitivity is improved, but the overall height of the device increases
Solution Approach 1:
The patent implements nesting by placing the MEMS sensor assembly within a recess cavity of the lead frame structure. The chamber is formed by the recess and the sensor assembly itself, effectively nesting the functional volume within the available space. This allows the back volume to be optimized for signal-to-noise ratio without proportionally increasing the overall device height, as the chamber is integrated into the lead frame's existing geometry rather than adding external volume.
Solution Approach 2:
The patent utilizes the vertical dimension by creating a recess cavity that extends downward from the lead frame surface. The chamber volume is optimized by controlling the depth of this recess rather than increasing the overall device footprint or height. This dimensional approach allows the back volume to be tuned for acoustic performance while maintaining a compact profile, as the volume is created by varying the recess depth rather than expanding the device envelope.
2Measurement precision
If the sound inlet opening size is optimized to improve sensitivity, then the signal quality is improved, but the device complexity increases
Solution Approach 1:
The patent merges the acoustic inlet structure with the lead frame housing. The sound inlet opening is formed as an integral part of the lead frame geometry rather than being a separate component. This integration allows the sound inlet to be optimized for acoustic performance while avoiding the complexity of additional assembly steps, fasteners, or separate structural elements that would otherwise be required.
Solution Approach 2:
The lead frame structure serves multiple functions simultaneously: it provides mechanical support for the MEMS sensor, defines the acoustic chamber volume, and forms the sound inlet opening. This multi-functionality eliminates the need for separate components for each function, thereby reducing device complexity while allowing optimization of the sound inlet for improved signal quality.
3Measurement precision
If the air flow through the capacitor gap is controlled to improve signal accuracy, then the measurement precision is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The patent employs the self-service principle by allowing the air flow through the capacitor gap to be naturally controlled by the operational characteristics of the device rather than requiring precise external control mechanisms. The capacitor gap geometry and the resulting air flow are determined by the inherent structural dimensions and operating voltage, which can be manufactured with standard precision tolerances. This eliminates the need for complex flow control systems or extremely tight manufacturing tolerances while still achieving acceptable signal accuracy.
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 MEMS sensor structure effectively increases the signal-to-noise ratio by optimizing the back volume and preventing encapsulation deposition, thereby improving the accuracy of converting sound waves or pressure changes into electrical signals.
Implementation Method 1
The MEMS sensor structure may be configured to convert an incident sound wave into an electrical signal
Data Source
AI summary
A sensor structure is disclosed. The sensor structure may include a lead frame for supporting a MEMS sensor, a recess in a surface of the lead frame, and a MEMS sensor coupled to the surface of the lead frame and arranged over the recess to form a chamber. Alternatively, the lead frame may have a perforation formed through it and the MEMS sensor may be coupled to the surface of the lead frame and arranged over an opening of the perforation.