MEMS Load Sensor with Overload Protection Ring
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Solution Overview
Problem
Existing MEMS devices fail to effectively recognize a range of human user actions and often suffer damage or cause injury due to excessive force, lacking adequate overload protection.
Innovation Solution
The development of MEMS load sensor devices with a deformable membrane, a mesa, and an overload protection portion, which include piezoresistive elements configured to produce a signal proportional to applied force, and are designed with a gap to prevent mechanical failure under excessive force, allowing for safe and accurate force measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional MEMS force sensors are used to measure applied load, then measurement capability is provided, but the device lacks overload protection and can be damaged by excessive force
Solution Approach 1:
The device is segmented into distinct functional portions: a deformable membrane for force sensing, a mesa structure for force transfer, and an overload protection portion with limited height. This segmentation allows each component to perform its specific function while contributing to overall reliability without excessive complexity.
Solution Approach 2:
The overload protection portion is designed with a height less than the mesa height, creating a predetermined mechanical limit that prevents the deformable membrane from deflecting beyond safe boundaries. This prior cushioning structure protects the device from damage before excessive force can cause harm.
2Measurement precision
If the deformable membrane is made more compliant to improve force sensing, then measurement precision improves, but the device becomes more susceptible to mechanical failure under excessive force
Solution Approach 1:
The solution moves the strength constraint from the two-dimensional membrane plane to the third dimension by introducing a vertical height difference between the mesa and overload protection portion. This dimensional approach allows the membrane to remain compliant for accurate sensing while the vertical structure provides mechanical strength and failure protection.
Solution Approach 2:
The overload protection portion acts as an intermediary mechanical element between the force application point and the deformable membrane. It mediates the force transmission by providing a hard stop that prevents excessive deflection, thereby protecting the membrane's mechanical integrity while allowing normal force sensing operation.
3Ease of manufacture
If the device structure is simplified to reduce manufacturing complexity, then ease of manufacture improves, but overload protection capability is reduced
Solution Approach 1:
The overload protection is achieved by changing a single geometric parameter - the height of the overload protection portion relative to the mesa. This parameter change provides robust overload protection while maintaining compatibility with standard MEMS manufacturing processes, thus balancing ease of manufacture with reliability.
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
These devices enable reliable and safe measurement of human user actions, preventing mechanical failure and injury by limiting deflection through the use of an air gap and overload protection, allowing for effective force-sensitive touch input in data processing systems.
Implementation Method 1
at least one load sensor element formed on the deformable membrane. The load sensor element can be configured to change at least one electrical characteristic based on an amount or magnitude of the applied force
Data Source
AI summary
A microelectromechanical (“MEMS”) load sensor device for measuring a force applied by a human user is described herein. In one aspect, the load sensor device has a contact surface in communication with a touch surface which communicates forces originating on the touch surface to a deformable membrane, on which load sensor elements are arranged, such that the load sensor device produces a signal proportional to forces imparted by a human user along the touch surface. In another aspect, the load sensor device has an overload protection ring to protect the load sensor device from excessive forces. In another aspect, the load sensor device has embedded logic circuitry to allow a microcontroller to individually address load sensor devices organized into an array. In another aspect, the load sensor device has electrical and mechanical connectors such as solder bumps designed to minimize cost of final component manufacturing.