Physical Quantity Sensor Protrusion Design for Bonding Prevention
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Solution Overview
Problem
Existing physical quantity sensors face issues with bonding between the movable body and substrate, leading to potential damage and short circuits, particularly due to protrusion portions being integral with the oscillating body and in contact with the substrate.
Innovation Solution
A physical quantity sensor design featuring a protrusion portion with a conductive layer of the same potential as the electrode and an insulating layer on the substrate side, positioned to overlap with the movable body, which prevents bonding and reduces damage by electrically connecting the movable body and electrode during anodic bonding, and includes a silicon oxide film for excellent insulating properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a protrusion portion is provided on the oscillating body to suppress excessive displacement, then the oscillating body can be constrained, but bonding between the oscillating body and substrate occurs and the protrusion portion is easily damaged
Solution Approach 1:
The protrusion portion is divided into two separate components: a protrusion formed on the substrate and a separate conductive member positioned above it. This segmentation prevents the oscillating body from directly contacting the substrate while maintaining the displacement constraint function, thereby eliminating bonding issues and damage risks.
Solution Approach 2:
A conductive member is introduced as an intermediary between the oscillating body and the protrusion on the substrate. This intermediary maintains the electrical connection needed for sensing while preventing direct contact between the oscillating body and substrate, thus avoiding bonding and damage problems.
2Strength
If anodic bonding is performed to bond substrates, then strong bonding is achieved, but the movable body bonds to the substrate causing short circuits
Solution Approach 1:
The conductive member is maintained at the same potential as the electrode during anodic bonding. This equipotential condition prevents charge accumulation and electrical breakdown, allowing strong substrate bonding while maintaining electrical insulation between the movable body and substrate.
Solution Approach 2:
The conductive member acts as an intermediary that manages electrical potential during bonding. By controlling its potential to match the electrode, it prevents unwanted electrical connections while allowing mechanical bonding to proceed.
3Ease of manufacture
If the protrusion portion is configured integrally with the oscillating body, then manufacturing is simplified, but the protrusion portion is easily damaged upon contact with the substrate
Solution Approach 1:
The protrusion portion is segmented into a substrate-mounted protrusion and a separate conductive member. This allows the conductive member to be made from tough, damage-resistant materials while the protrusion is firmly anchored to the substrate, combining manufacturing ease with damage resistance.
Solution Approach 2:
The system uses composite construction with the protrusion formed from substrate material and the conductive member made from separate conductive material. This composite approach allows optimization of each component for its specific function while improving overall durability.
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 design effectively prevents bonding and damage to the movable body, reduces the risk of short circuits, and simplifies the manufacturing process by allowing for the collective formation of the conductive layer and electrode, enhancing the reliability of the sensor.
Implementation Method 1
it is possible to prevent or alleviate bonding to the substrate of the movable body, by electrically connecting the movable body and the electrode, when performing anodic bonding of the substrate and another substrate
Implementation Method 2
since the insulating layer of the protrusion portion is provided at a tip end side of the protrusion portion with respect to the conductive layer, it is possible to prevent a short circuit between the movable body and the electrode
Data Source
AI summary
A physical quantity sensor includes a base substrate; a movable unit which is provided so as to be displaced with respect to the base substrate by facing the base substrate; a first fixed electrode and a second fixed electrode which are disposed on the base substrate by facing the movable unit; and a plurality of protrusion portions which are disposed at a position overlapped with the movable unit in a planar view, on the movable unit side of the base substrate, in which the protrusion portion includes a conductive layer with the same potential as that of the first fixed electrode and the second fixed electrode, and an insulating layer which is provided on a side opposite to the base substrate with respect to the conductive layer.