Physical Quantity Sensor Support Structure for Thermal Stress Management
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Solution Overview
Problem
Existing acceleration sensors face issues with stress caused by thermal expansion differences between support units and connection metal layers, leading to potential bonding strength deficiencies and temperature characteristic deterioration.
Innovation Solution
A physical quantity sensor design featuring a support structure with a first bond portion bonded to a base and a second bond portion bonded to wiring, including overhang portions and notch configurations, to absorb thermal stress and maintain bonding strength while reducing size and improving temperature stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the support unit is bonded only with connection metal layer on the lower surface, then the bonding structure is simple, but stress caused by thermal expansion difference easily occurs
Solution Approach 1:
The support unit is divided into multiple bond portions: a first bond portion on the upper surface bonded with insulation layer, and a second bond portion on the lower surface bonded with connection metal layer. This segmentation allows different regions to handle different bonding functions, reducing thermal stress while maintaining bonding strength.
Solution Approach 2:
Different surface treatments and bonding methods are applied to different regions of the support unit. The upper surface has a first bond portion for insulation layer bonding, while the lower surface has a second bond portion for metal layer bonding. This local differentiation optimizes each bonding interface for its specific requirements.
2Reliability
If the support unit is bonded with connection metal layer on the lower surface, then electrical connection is achieved, but bonding strength is insufficient due to silicon-metal bonding difficulties
Solution Approach 1:
The support unit employs a composite structure with a first bond portion for insulation bonding and a second bond portion for metal connection. This composite approach combines the advantages of different bonding methods, achieving both electrical connectivity and mechanical strength.
3Reliability
If the upper surface of the support unit is bonded to the support substrate with insulation layer interposed, then insulation is provided, but bonding stress from support substrate bonding is applied to the support unit
Solution Approach 1:
The bonding functions are segmented into two separate portions: the first bond portion on the upper surface handles insulation layer bonding, while the second bond portion on the lower surface handles connection metal layer bonding. This separation isolates the support unit from bonding stress by providing dedicated bonding zones.
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 temperature characteristic deterioration and maintains bonding strength, enhancing the sensor's reliability and precision in detecting acceleration.
Implementation Method 1
stress caused due to a difference in a coefficient of thermal expansion between the support unit and the connection metal layer easily occurs
Data Source
AI summary
A physical quantity sensor includes: a base; wiring disposed in the base; a support that includes a first bonded surface bonded to the base and a second bonded surface bonded to the wiring; a suspension beam connected to the support; and an electrode finger supported by the suspension beam. The support is located between the first bonded surface and the suspension beam and includes a first overhang separated from the base.