MEMS Package Test Electrodes for High Spring Constant Deflection
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Solution Overview
Problem
Conventional microelectromechanical systems (MEMS) face limitations in self-testing due to the need for high electrostatic forces to deflect a movable mass, which is restricted by the size of self-test electrodes and the voltage limitations of the controller, especially when using springs with high spring constants, leading to insufficient deflection in some cases.
Innovation Solution
The configuration of additional test electrodes positioned on opposite sides of the movable mass, electrically connected to external pins accessible to industry-standard testing equipment, allowing for higher voltages to be applied without voltage limitations from the controller, enabling greater electrostatic forces to be generated for effective deflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If self-test electrodes are used to generate electrostatic force for deflecting the movable mass, then the MEMS device can perform self-testing, but the voltage is limited by the controller which prevents sufficient deflection when using springs with high spring constants
Solution Approach 1:
The patent divides the testing function into two separate electrode systems: self-test electrodes connected to the controller for basic functionality verification, and additional test electrodes connected to external pins for applying higher voltages. This segmentation allows each system to operate within its appropriate voltage range, resolving the contradiction between self-testing capability and sufficient electrostatic force generation.
Solution Approach 2:
The additional test electrodes serve as an intermediary mechanism that bridges the gap between the controller's voltage limitations and the requirements for deflecting high spring constant springs. By providing an external voltage application path, the system can achieve the necessary electrostatic force without modifying the controller itself.
2Force
If additional test electrodes are added to the MEMS device, then higher voltages can be applied to achieve sufficient deflection of the movable mass, but the device complexity increases
Solution Approach 1:
The additional test electrodes are integrated into the existing MEMS device structure and share the same substrate and movable mass as the self-test electrodes. This multi-functionality approach allows the device to perform both self-testing and high-voltage testing without requiring completely separate systems, thereby minimizing the increase in device complexity.
3Ease of operation
If the movable mass is deflected using electrostatic force from test electrodes, then the position of the movable mass changes for testing purposes, but the deflection may be insufficient when springs have high spring constants
Solution Approach 1:
The patent changes the voltage parameter by providing an external voltage application path through additional test electrodes. This allows the voltage to exceed the controller's limitations, thereby generating sufficient electrostatic force to deflect movable masses with high spring constants that would otherwise remain stationary during self-testing.
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 configuration allows for effective self-testing of MEMS devices with springs of high spring constants, ensuring reliable deflection of the movable mass and accurate capacitance detection, reducing the need for specialized equipment and enhancing testing efficiency.
Implementation Method 1
The additional test electrodes are configured to generate a net electrostatic force to move the movable mass
Implementation Method 2
The controller is configured to detect a differential between a first capacitance existing between the movable mass and the first sense electrode and a second capacitance existing between the movable mass and the second sense electrode
Data Source
AI summary
A microelectromechanical system (MEMS) package is disclosed herein. The MEMS package includes a movable mass. The MEMS package further includes a first and second sense electrodes spaced apart from the movable mass. The first and second sense electrodes are configured to be electrically coupled with a controller. The MEMS package further includes a first test electrode and a second test electrode spaced apart from the movable mass. The first and the second test electrodes are configured to be electrically connected to first and second external electrical connectors, respectively. The first and second test electrodes are biased at a first voltage and a second voltage, respectively, when the first and second external electrical connectors are connected to external voltage sources.