Physical Quantity Sensor Thin Film Stress Control
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Solution Overview
Problem
Conventional physical quantity sensors with thin film sections experience variability in maximum tensile stress and breakdown voltage due to the generation of stress at corner-shaped ends, leading to inconsistent sensor performance.
Innovation Solution
The design includes a first substrate with a recess and a second substrate with a hollow, where the recess and hollow sizes are configured such that the projected line from the recess's bottom surface surrounds the hollow's open end, ensuring maximum tensile stress is generated at a specific position rather than a corner, thereby stabilizing the breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the thin film section has a corner-shaped end structure, then the manufacturing is simpler, but the maximum tensile stress becomes variable and unreliable
Solution Approach 1:
The patent replaces the corner-shaped end structure with a curved end structure in the thin film section. This curvature eliminates the stress concentration and variability associated with sharp corners, ensuring that the maximum tensile stress occurs at a predictable location and has consistent magnitude. The curved geometry maintains manufacturing feasibility while significantly improving the reliability and reproducibility of stress characteristics.
2Ease of manufacture
If the recess and hollow sizes are not precisely controlled, then the manufacturing process is easier, but the breakdown voltage varies
Solution Approach 1:
The patent establishes specific quantitative relationships between the dimensions of the recess and hollow structures. By defining precise parameter ranges and ratios, the invention ensures that the maximum tensile stress occurs at the intended location on the thin film section. This parametric control methodology maintains manufacturing ease while guaranteeing consistent breakdown voltage characteristics across production batches.
3Force
If the maximum tensile stress is generated at a corner position, then the stress concentration is higher, but the stress location is unpredictable and varies
Solution Approach 1:
The curved end structure redistributes the stress field uniformly along the thin film section, eliminating unpredictable stress concentration at corner positions. This geometric modification ensures that the maximum tensile stress occurs at a well-defined, reproducible location while maintaining adequate stress magnitude for sensor operation. The curvature radius is specifically designed to optimize both stress magnitude and location predictability.
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 configuration restricts variation in maximum tensile stress and breakdown voltage, enhancing the reliability and consistency of physical quantity sensors like pressure, acceleration, and angular velocity sensors.
Implementation Method 1
the thin film section is configured so that a maximum tensile stress is generated at the specific position when the thin film section is displaced toward the hollow
Data Source
AI summary
In a physical quantity sensor, a first substrate has a recess depressed from a second surface to provide a thin film section adjacent to a first surface, and a second substrate has a first surface bonded to the first surface of the first substrate, and has a hollow depressed from the first surface and facing the recess. The recess and the hollow have such sizes that a projected line defined by projecting an end of a bottom surface in the recess to the first surface of the first substrate surrounds an open end of the hollow. When the thin film section is displaced toward the hollow, a maximum tensile stress is generated at a position on a rear surface of the thin film section intersecting an extended line along a normal direction to the first surface of the first substrate and passing through the open end of the hollow.