Surface Stress Sensor Support Structure for Thermal Offset Suppression
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Solution Overview
Problem
Piezoresistive cantilever-type surface stress sensors suffer from measurement precision deterioration due to substrate deformation caused by environmental temperature changes, which introduces offset stress that overwhelms the intended surface stress measurement.
Innovation Solution
A surface stress sensor design with a support base member having high rigidity, positioned between the membrane and the package substrate, to mitigate the impact of substrate deformation and maintain measurement precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the planar member is supported in mid-air to receive applied surface stress, then the sensor can detect surface stress, but substrate deformation applies excessive stress to the membrane causing offset and measurement precision deterioration
Solution Approach 1:
The patent introduces a support base member with protrusions or recesses as an intermediary between the membrane and substrate. This mediator absorbs and distributes substrate deformation stress, preventing it from being directly transmitted to the membrane, thus resolving the contradiction between maintaining membrane sensitivity and protecting from substrate-induced stress
2Stability of the object's composition
If the planar member is fixed to substrate via spacers, then the membrane is supported, but substrate deformation still transmits stress to the membrane causing offset
Solution Approach 1:
The patent applies local quality by creating specific protrusion or recess patterns at predetermined positions on the support base member. These localized structural features selectively absorb stress at critical points while maintaining overall membrane support stability, thus resolving the contradiction between support stability 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
The design effectively reduces stress applied to the membrane due to substrate deformation, thereby enhancing measurement precision and stability across varying temperature conditions.
Implementation Method 1
surface stress applied to a planar member is detected as uniaxial stress in four piezoresistive coupling portions
Data Source
Figure 1~2
Figure 3~5
Figure 6A~7
AI summary
Provided are a surface stress sensor that enables deterioration in measurement precision to be suppressed and a method for manufacturing the same. A surface stress sensor (1) includes: a membrane (22) configured to be bent by applied surface stress; a frame member (24) configured to surround the membrane (22) with gaps interposed therebetween when viewed from the thickness direction of the membrane (22); at least a pair of coupling portions (26) configured to be arranged at positions sandwiching the membrane (22) when viewed from the thickness direction of the membrane (22) and configured to couple the membrane (22) and the frame member (24); a flexible resistor (50) configured to be disposed on at least one of the coupling portions (26) and have a resistance value that changes according to bending induced in the coupling portion (26); and a support base member (10) configured to be connected to the frame member (24) and overlap the frame member (24) when viewed from the thickness direction of the membrane (22), in which a cavity portion (40) is disposed between the membrane (22) and the support base member (10).