MEMS Die Cap Humidity Sensing for Drift Compensation
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Solution Overview
Problem
Existing MEMS devices incorporating inertial sensors like gyroscopes and accelerometers are vulnerable to humidity and liquid exposure, leading to mechanical deformations and signal drifts due to impermeable housing failures, which current humidity sensors of incompatible dimensions cannot address.
Innovation Solution
Integration of a capacitive humidity sensor on the MEMS die cap, correlated with signal processing circuitry to compensate for deformations and signal drifts by calibrating output signals based on humidity levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a resin packaging mass is used to protect the MEMS device, then mechanical protection and electrical insulation are provided, but impermeability to water droplets is not ensured
Solution Approach 1:
The patent applies a conformal coating layer (such as parylene, epoxy, or polyimide) over the MEMS device and humidity sensor. This thin film provides a hermetic seal that prevents water droplet penetration while conforming to the device geometry, resolving the contradiction between mechanical protection and humidity impermeability
Solution Approach 2:
The patent combines the resin packaging mass with a conformal coating layer to create a composite protection system. The resin provides mechanical support and electrical insulation, while the conformal coating layer provides hermetic sealing, together resolving the contradiction between protection capability and humidity resistance
2Measurement precision
If commercial humidity sensors are used to detect humidity, then humidity measurement is achieved, but their large dimensions are incompatible with MEMS device size
Solution Approach 1:
The patent integrates the humidity sensor directly onto the MEMS device substrate, merging two separate components into a single unified structure. This integration allows the humidity sensor to be miniaturized to match the MEMS device scale while maintaining measurement capability
Solution Approach 2:
The patent transitions from using discrete commercial humidity sensors (three-dimensional components) to integrating a planar humidity sensor structure directly on the MEMS substrate. This dimensional change enables miniaturization and compatibility with the small form factor of MEMS devices
3Measurement precision
If humidity sensors are exposed to external environment to measure ambient humidity, then humidity measurement is possible, but the sensor cannot detect deformation of the device
Solution Approach 1:
The patent designs the humidity sensor to serve dual functions: measuring ambient humidity levels and detecting mechanical deformation of the MEMS device. By making the sensor responsive to both chemical (humidity) and mechanical (deformation) stimuli, the sensor becomes a multi-functional element that resolves the contradiction between specialized humidity measurement and general deformation detection capability
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
Provides reliable humidity detection and deformation compensation, ensuring accurate sensor performance by integrating a compact humidity sensor that correlates capacitance changes with humidity levels for real-time signal correction.
Implementation Method 1
Integration of a capacitive humidity sensor on the MEMS die cap, correlated with signal processing circuitry to compensate for deformations and signal drifts by calibrating output signals based on humidity levels
Data Source
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AI summary
Packaged MEMS device (20) having a MEMS die (24) of semiconductor material formed by a sensor body (31) and a cap (32) mutually bonded. The sensor body (31) incorporates at least one MEMS component (XL, G) and the cap (32) carries a humidity sensor (30) having a first and a second group of electrodes, facing each other and capacitively coupled, configured to provide a humidity signal. A packaging mass (25), of electrically insulating material, surrounds the MEMS die (24) and the humidity sensor (30).