Micromechanical Pressure Sensor Bubble-Free Filling
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Solution Overview
Problem
Existing micromechanical pressure sensor devices face challenges in effectively decoupling mechanical stress and preventing parasitic inductions, such as those from temperature and packaging deformations, which affect the accuracy of pressure detection, and existing methods like lateral free trenching and gel filling can introduce bubbles, reducing performance.
Innovation Solution
A micromechanical pressure sensor device design featuring a separate channel in the periphery with a larger diameter than access openings and stress relief trenches, allowing for bubble-free filling with a passivation medium, and a mold housing that encloses substrates with specific openings for filling and protection, along with mechanical decoupling using strip conductors and webs for enhanced stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lateral free trenching or free etching of the diaphragm is used for mechanical decoupling, then mechanical stress decoupling is improved, but the filling process becomes complex and bubbles may be trapped
Solution Approach 1:
The patent divides the filling approach by introducing a separate dedicated channel structure distinct from the sensor access openings. This segmentation allows the filling process to be independent from the sensor measurement path, enabling bubble-free filling while maintaining mechanical decoupling through the trench structure.
Solution Approach 2:
The patent introduces a dedicated filling channel as an intermediary structure that mediates between the external environment and the sensor cavity. This separate pathway allows the passivation medium to be introduced without interfering with the sensor operation or trapping bubbles in the measurement path.
2Measurement precision
If piezoresistive semiconductor resistors are used for pressure detection, then pressure sensing capability is improved, but mechanical parasitic inductions from temperature and packaging deformations worsen measurement accuracy
Solution Approach 1:
The patent extracts the diaphragm from the mechanical stress path by creating free trenches that decouple it from the package housing and mounting board. This extraction removes the source of parasitic stress inductions while preserving the pressure sensing function through the piezoresistive resistors.
Solution Approach 2:
The patent segments the mechanical structure by introducing free trenches that separate the diaphragm area from the package housing and mounting board. This segmentation isolates the sensitive pressure sensing region from external mechanical influences while maintaining the electrical connection through the piezoresistive resistors.
3Reliability
If the sensor surface is filled with gel for media resistance, then media resistance is improved, but bubbles trapped in the gel worsen sensor performance
Solution Approach 1:
The patent performs preliminary action by providing a dedicated filling channel that enables controlled introduction of the passivation medium. This preliminary structural preparation allows for bubble-free filling before the sensor is sealed, preventing performance degradation from the outset.
Solution Approach 2:
The patent uses the dedicated filling channel as an intermediary pathway that separates the filling operation from the sensor measurement path. This intermediary structure allows the gel to be introduced without trapping bubbles in the sensor cavity, maintaining both media resistance and measurement precision.
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 design achieves effective media resistance and robust pressure detection by simplifying the filling process, preventing bubble formation, and providing mechanical decoupling, thus enhancing the accuracy and reliability of the pressure sensor device.
Implementation Method 1
A piezoresistive pressure measuring method, in which piezoresistive semiconductor resistors are provided in or on a diaphragm of a micromechanical pressure sensor device
Implementation Method 2
The pressure detection takes place via a deflection of a diaphragm-like first electrode in relation to a second fixed electrode with the aid of a capacitive measuring method
Data Source
AI summary
A micromechanical pressure sensor device is equipped with a sensor substrate including a front side and a rear side. The device includes a pressure sensor unit suspended in the sensor substrate, a first cavity above the pressure sensor unit, which is exposed toward the front side via one or multiple access openings, one or multiple stress relief trenches, which laterally enclose the pressure sensor unit and form a fluidic connection from the rear side to the first cavity, and a circuit substrate, on which the rear side of the sensor substrate is bonded. A second cavity, which is in fluidic connection with the stress relief trenches, is formed below the pressure sensor unit in the circuit substrate. At least one channel is provided in a periphery of the pressure sensor unit, which is in fluidic connection with the second cavity and is exposed to the outside.