MEMS Accelerometer Protrusion Design for Collision Prevention
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Solution Overview
Problem
Existing physical quantity sensors, such as those using silicon MEMS techniques, face manufacturing complexity due to the need for a stopper to prevent the conductive plate and proof mass from colliding, which complicates the manufacturing process and can lead to damage during high acceleration measurements.
Innovation Solution
A physical quantity sensor design featuring an oscillating member with protrusions on its side faces, which can collide with the substrate to prevent damage and simplify manufacturing by being formed from a single substrate, along with a counter electrode to maintain the same potential and reduce sticking, and a frame member with constant gap widths for efficient etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a stopper is added to prevent collision between the conductive plate and proof mass, then reliability is improved, but device complexity increases due to additional manufacturing steps
Solution Approach 1:
The stopper is merged with the proof mass as a single integrated structure. The protrusion is formed as part of the proof mass itself, eliminating the need for separate stopper components and reducing manufacturing steps while maintaining the collision prevention function.
Solution Approach 2:
The proof mass serves multiple functions: it acts as the oscillating mass for detection and simultaneously provides the stopper function through its protrusion. This multi-functionality reduces the total number of components needed in the device.
2Reliability
If a stopper protruding to the protective shield is used to prevent contact between conductive plate and proof mass, then reliability is improved, but ease of manufacture deteriorates due to complicated deposition and patterning processes
Solution Approach 1:
The stopper is merged with the proof mass as a single integrated structure. The protrusion is formed as part of the proof mass itself, eliminating the need for separate stopper components and reducing manufacturing steps while maintaining the collision prevention function.
3Ease of manufacture
If the oscillating member is designed without protective stoppers, then ease of manufacture is improved, but reliability deteriorates due to potential damage during high acceleration measurements
Solution Approach 1:
The stopper is merged with the proof mass as a single integrated structure. The protrusion is formed as part of the proof mass itself, eliminating the need for separate stopper components and reducing manufacturing steps while maintaining the collision prevention function.
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 enhances reliability by preventing oscillating member damage, simplifies manufacturing processes, and reduces contact area to prevent sticking, while maintaining high precision and efficiency in acceleration measurements.
Implementation Method 1
The physical quantity sensor disclosed in JP-A-2008-529001 detects the acceleration on the basis of a variation in capacitance between the conductive plate and the proof mass, which results from oscillation of the proof mass.
Data Source
AI summary
A physical quantity sensor includes a substrate, an oscillating member that is disposed over the substrate, support portions that support the oscillating member and that are disposed along a first axis, and detection electrodes that are disposed on the substrate so as to oppose the oscillating member. The oscillating member has a pair of side faces intersecting a second axis perpendicular to the first axis in a plane, and a protrusion is formed on at least one of the pair of side faces.