Pressure Measurement Structure with Strain-Amplifying Substrate
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Solution Overview
Problem
Existing pressure-sensitive buttons in electronic devices suffer from low sensitivity and accuracy due to insufficient deformation of piezo-resistors, which is exacerbated by factors like housing thickness and uneven force application, and are affected by temperature variations.
Innovation Solution
A pressure detection structure that amplifies strain in piezo-resistors through substrate deformation, using a Wheatstone bridge configuration with strategically positioned piezo-resistors to minimize temperature impacts by offsetting resistance value changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a piezo-resistor is used in a pressure detection structure, then pressure detection function is achieved, but sensitivity is low due to insufficient deformation
Solution Approach 1:
The piezo-resistor is divided into multiple segments arranged in a specific pattern on the substrate. This segmentation allows different regions to experience different stress distributions, enhancing the overall deformation response and sensitivity of the pressure detection structure.
Solution Approach 2:
The piezo-resistor transitions from a traditional single-point contact to a distributed multi-point contact structure on the substrate. This dimensional expansion from point to surface contact increases the effective deformation area and improves sensitivity while maintaining structural integrity.
2Strength
If housing thickness is increased, then structural strength is improved, but piezo-resistor deformation becomes less obvious
Solution Approach 1:
A flexible substrate is introduced as an intermediary layer between the housing and the piezo-resistor. This substrate acts as a mediator that transmits and concentrates the applied pressure to the piezo-resistor, enabling effective deformation even when the housing thickness is increased for structural strength.
Solution Approach 2:
The substrate is designed with non-uniform thickness or stiffness distribution, creating regions of high and low mechanical compliance. This local quality variation ensures that pressure is concentrated at specific locations where piezo-resistors are positioned, maximizing deformation in critical areas while maintaining overall housing strength.
3Measurement precision
If force is applied unevenly on the piezo-resistor area, then pressure detection function is achieved, but deformation degree is reduced
Solution Approach 1:
The piezo-resistor and substrate are designed with asymmetric geometric patterns that are specifically tailored to compensate for uneven force application. This asymmetric design creates predictable stress distribution patterns that enhance deformation in regions where force is applied, improving both detection capability and consistency.
4Adaptability or versatility
If temperature variations occur, then environmental adaptability is improved, but resistance value changes affect detection accuracy
Solution Approach 1:
The substrate material is selected or engineered to have specific thermal expansion characteristics that counteract the temperature-induced resistance changes in the piezo-resistor. By changing the thermal parameters of the substrate, the system maintains detection accuracy across varying temperatures while preserving environmental adaptability.
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
Enhances pressure detection sensitivity and accuracy by concentrating strain in specific piezo-resistors while reducing temperature effects, improving overall performance.
Implementation Method 1
A principle of using the piezo-resistor for pressure detection is: When the area in which the piezo-resistor is disposed on the electronic device is subject to pressure by an external force, the external force is transferred to the piezo-resistor through the housing of the electronic device, causing the piezo-resistor to deform. A resistance value of the piezo-resistor that deforms changes.
Implementation Method 2
when an external force is pressed on a second surface of the substrate, the substrate is deformed, so that a strain is amplified in the piezo-resistor
Implementation Method 3
using a Wheatstone bridge configuration with strategically positioned piezo-resistors to minimize temperature impacts by offsetting resistance value changes
Data Source
Figure 1A(a)~1A(c)
Figure 1B
Figure 1C
AI summary
This application discloses a pressure detection structure and an electronic device, and relates to the field of touch control technologies, to improve sensitivity and accuracy of pressure detection. The pressure detection structure includes: a substrate on which a first cavity is disposed, a first dielectric layer fastened to a first surface of the substrate, and N piezo-resistors connected at the first dielectric layer to form a Wheatstone bridge, where an opening of the first cavity is provided on the first surface of the substrate. Two ends, in a first direction, of a vertical projection of a first piezo-resistor in the N piezo-resistors on a contact surface between the N piezo-resistors and the first dielectric layer are on two sides, in the first direction, of a vertical projection of the first cavity on the contact surface. A long side of a second piezo-resistor in the N piezo-resistors is perpendicular to the first direction, and a vertical projection of the second piezo-resistor on the contact surface does not overlap with the vertical projection of the first cavity. When a second surface of the substrate is pressed by an external force, a stress is transferred to the first dielectric layer, causing the first piezo-resistor to deform.