Physical Quantity Sensor Recess Design for Stress Relaxation
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Solution Overview
Problem
Existing acceleration sensors face challenges in maintaining strong bonding between the sensor main body and the package due to stress relaxation issues, often resulting in reduced bonding strength caused by large spot faces and inadequate bonding areas.
Innovation Solution
A physical quantity sensor design featuring recess portions on the substrate to absorb and relax stress, allowing for improved bonding strength between the sensor elements and the support substrate, while maintaining mechanical integrity and accurate measurement capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If a large spot face is formed on the sensor main body to relax stress, then stress relaxation is improved, but the bonding area between the sensor main body and the package is reduced, resulting in lower bonding strength
Solution Approach 1:
The invention transitions from a two-dimensional spot face on the surface to a three-dimensional recess portion that extends into the substrate. This dimensional change allows stress relaxation to occur through the depth of the recess while preserving the surface bonding area, effectively resolving the contradiction between stress relaxation and bonding strength.
Solution Approach 2:
The recess portions are strategically positioned to overlap with the fixed portions of sensor elements in plan view, creating localized stress relief zones exactly where needed. This localized approach ensures stress relaxation is applied precisely to the sensor elements without sacrificing overall bonding area.
2Stress or pressure
If multiple recess portions are formed to relax stress effectively, then stress relaxation is improved, but the substrate area available for bonding is reduced
Solution Approach 1:
The invention divides the stress relief function into multiple separate recess portions, each positioned to overlap with specific sensor element fixed portions. This segmentation allows targeted stress relaxation at each sensor element location while maintaining adequate bonding area in the regions between the recesses.
Solution Approach 2:
The recess portions are designed with controlled dimensions and spacing to provide sufficient stress relaxation without excessively reducing the bonding area. The partial action approach ensures that stress relief is applied where most needed (under sensor elements) while preserving adequate bonding surface.
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 sensor design effectively absorbs and relaxes stress, preventing its transmission to the sensor elements, ensuring accurate measurement of physical quantities and enhancing the bonding strength between the substrate and support substrate, thus improving the reliability of the sensor system.
Implementation Method 1
it is possible to absorb and relax stress caused by thermal distortion of the support substrate and the like by the first recess portion and the second recess portion
Data Source
AI summary
A physical quantity sensor includes a substrate, a first sensor element that is positioned on one main surface of the substrate and includes a first fixed portion fixed to the substrate, a second sensor element that is positioned on the one main surface of the substrate and includes a second fixed portion fixed to the substrate, a first recess portion that is open to the other main surface of the substrate and is disposed so as to overlap the first fixed portion in plan view of the substrate, and a second recess portion that is open to the other main surface of the substrate and is disposed so as to overlap the second fixed portion in plan view of the substrate, and in which the first recess portion and the second recess portion are disposed so as to be separated from each other.