Wafer Level MEMS Force Die with Spacer for Overload Protection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current force sensors, joysticks, and touch-controls rely on aging technologies such as mechanical buttons and resistive ink, which are not highly sensitive, compact, or cost-effective for OEM applications.
Innovation Solution
The development of composite wafer level MEMS force dies featuring a spacer coupled to a sensor with flexible sensing elements, such as beams or diaphragms, that change electrical characteristics in response to applied force, allowing for precise force measurement through variable electrical properties like resistance or capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mechanical buttons and resistive ink are used, then device complexity is reduced, but measurement precision and sensitivity deteriorate
Solution Approach 1:
The patent replaces mechanical buttons and resistive ink with a MEMS-based force sensor that uses a flexible diaphragm and piezoresistive elements. The mechanical force is converted to electrical signal through the piezoresistive effect, achieving higher measurement precision while maintaining compactness. The sensor structure includes a flexible diaphragm that deflects under force, with piezoresistive elements that change resistance based on the deflection, providing precise force measurement.
Solution Approach 2:
The patent utilizes the piezoresistive effect where the resistance of sensor elements changes in response to applied force. The flexible diaphragm deflects under force, and this mechanical deformation is converted to an electrical signal through the change in resistance of the piezoresistive elements. This parameter change enables precise force measurement while maintaining a compact structure.
2Measurement precision
If flexible sensing elements are made highly sensitive, then measurement precision improves, but reliability deteriorates due to potential damage from excessive force
Solution Approach 1:
The patent incorporates a gap between the flexible diaphragm and the spacer that allows the diaphragm to deflect under normal operating forces. This gap acts as a cushioning mechanism that prevents excessive deflection and potential damage to the sensor elements. The gap is designed to accommodate the maximum expected force while protecting the sensitive piezoresistive elements from overload.
Solution Approach 2:
The spacer acts as an intermediary structure between the flexible diaphragm and the sensor elements. The spacer provides mechanical support and defines the gap that allows controlled deflection. This intermediary structure protects the sensitive sensing elements from direct exposure to excessive forces while maintaining the flexibility needed for precise measurement.
3Productivity
If wafer level fabrication is used, then productivity improves, but manufacturing precision requirements increase
Solution Approach 1:
The patent integrates multiple sensor elements and structures onto a single wafer using wafer-level fabrication techniques. The flexible diaphragm, piezoresistive elements, and spacer are all fabricated in a unified process on the wafer, enabling mass production. This merging of components onto a single wafer improves productivity while the standardized wafer fabrication process ensures consistent manufacturing precision.
Solution Approach 2:
The wafer-level fabrication process uses standardized parameters and techniques that ensure consistent manufacturing precision across multiple sensors. The piezoresistive elements are formed using controlled deposition and etching processes that maintain precise dimensional control. This standardized approach to wafer fabrication enables mass production while maintaining high manufacturing precision.
4Volume of moving object
If compact sensor design is implemented, then device volume is reduced, but ease of manufacture deteriorates
Solution Approach 1:
The patent designs the sensor with a nested structure where the piezoresistive elements are integrated into the flexible diaphragm, which is itself part of the compact MEMS structure. The spacer is positioned adjacent to the diaphragm, creating a space-efficient arrangement. This nesting of components achieves a compact sensor design that is still manufacturable using standard wafer-level fabrication techniques.
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 solution provides high sensitivity, compactness, and cost-effectiveness in force measurement, with the flexible sensing elements deflecting to stress sensor elements, generating an output signal proportional to the applied force while offering overload protection through strategically designed gaps.
Implementation Method 1
the sensor elements can have at least one variable electrical characteristic (e.g., resistance, capacitance, charge, etc.) based on an amount or magnitude of applied force
Implementation Method 2
the sensors elements can be piezoresistive, piezoelectric or capacitive elements
Implementation Method 3
the sensor elements can have at least one variable electrical characteristic (e.g., resistance, capacitance, charge, etc.)
Data Source
AI summary
A composite wafer level MEMS force dies including a spacer coupled to a sensor is described herein. The sensor includes at least one flexible sensing element, such as a beam or diaphragm, which have one or more sensor elements formed thereon. Bonding pads connected to the sensor elements are placed on the outer periphery of the sensor. The spacer, which protects the flexible sensing element and the wire bonding pads, is bonded to the sensor. For the beam version, the bond is implemented at the outer edges of the die. For the diaphragm version, the bond is implemented in the center of the die. An interior gap between the spacer and the sensor allows the flexible sensing element to deflect. The gap can also be used to limit the amount of deflection of the flexible sensing element in order to provide overload protection.