Capacitive Pressure Sensor Substrate Trench Segmentation
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Solution Overview
Problem
Electrostatic-capacitive pressure detection elements face challenges in maintaining a consistent distance between the diaphragm and electrodes due to deflection caused by external forces, such as thermal expansion and curing shrinkage of resin packages, leading to measurement accuracy variations.
Innovation Solution
Incorporating a trench on the substrate between the diaphragm portions and providing communication paths between spaces to match the deflected shape of the substrate and membrane, reducing the change in distance between the diaphragm and electrodes, and using cavities to relieve pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the substrate and diaphragm are made with a rectangular shape having a long direction dimension at least three times as long as the short direction dimension, then deflection in the short direction is reduced and the deflected shapes of both match, but when a large external force acts on the pressure detection element, the diaphragm may be deflected and deformed to the short direction, causing the distance between the diaphragm and electrodes to change
Solution Approach 1:
The substrate is divided into multiple regions by introducing trenches, creating a segmented structure. This segmentation allows different portions of the substrate to deflect independently under external force, preventing uniform deformation that would change the distance between the diaphragm and electrodes. The trenches act as stress relief zones that accommodate deformation without affecting the electrode-diaphragm spacing.
Solution Approach 2:
The substrate is designed with non-uniform properties through the introduction of trenches at specific locations. The regions between trenches have different mechanical properties compared to a uniform substrate, allowing localized deformation in specific areas while maintaining the overall distance consistency between the diaphragm and electrodes in the measurement regions.
2Measurement precision
If communication paths are provided between spaces and cavities to allow pressure escape, then measurement accuracy is enhanced by reducing pressure buildup, but the structural complexity of the substrate increases
Solution Approach 1:
The communication paths between spaces and cavities are integrated directly into the substrate structure during manufacturing, rather than being added as separate components. This merging of functions (structural support and pressure relief) into a single integrated substrate reduces overall device complexity while maintaining the pressure escape functionality needed for accurate measurements.
Solution Approach 2:
The substrate incorporates cavity structures that create a porous-like internal architecture, allowing pressure to escape through predefined pathways. This porous structure enables pressure relief functionality without requiring complex external pressure management systems, maintaining measurement accuracy while controlling structural complexity.
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 reduces the change in distance between the diaphragm and electrodes due to deflection, enhancing measurement accuracy and robustness against external forces by allowing pressure to escape, thus maintaining consistent measurement readings.
Implementation Method 1
electrostatic-capacitive pressure detection element
Data Source
AI summary
A pressure detection element includes a substrate, first and second electrodes on the substrate, a membrane including a first diaphragm portion and a second diaphragm portion and spaced from the substrate, and a spacer between the substrate and the membrane to define a first space in which the first electrode and the first diaphragm portion are spaced from and opposed to each other and a second space in which the second electrode and the second diaphragm portion are spaced from and opposed to each other. The substrate includes a trench in a portion positioned between the first diaphragm portion and the second diaphragm portion when viewed in a direction in which the substrate and the membrane are opposed.