Drop-Resistant MEMS Actuator with Flexible Stoppers
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
MEMS electrostatic actuators used for autofocus and optical image stabilization in cameras are vulnerable to damage from drops and shocks, particularly due to the brittleness of silicon materials, which can lead to chipping and image quality degradation when exposed to severe mechanical stress along all six directions.
Innovation Solution
The implementation of a series of flexible stoppers and hard stoppers within the MEMS actuator structure and packaging to decelerate and completely stop the moving mass along in-plane axes (±x, ±y) and out-of-plane axes (±z), utilizing the MEMS package structure as stoppers to prevent damage and chipping, and incorporating a BGA substrate for additional shock absorption and signal routing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mechanical stoppers are used to stop the proof mass in MEMS sensors, then the motion along in-plane axes can be limited, but the proof mass may still damage the image sensor pixels when moving along the out-of-plane z-axis due to lack of stopping mechanism
Solution Approach 1:
The stopping mechanism is segmented into multiple components: flexible stoppers for in-plane axes (x, y) and the MEMS package structure for out-of-plane axis (z). This division allows each component to be optimized for its specific function without interfering with the image sensor pixels.
Solution Approach 2:
The MEMS package structure acts as an intermediary stopping mechanism that prevents the proof mass from directly contacting and damaging the image sensor pixels during out-of-plane motion. The package structure absorbs the impact energy before it reaches the sensitive pixels.
2Adaptability or versatility
If heavy loads such as image sensors are carried by MEMS actuators, then autofocus and optical image stabilization functions are achieved, but the actuators become vulnerable to chipping and damage during drops due to the brittleness of silicon material
Solution Approach 1:
Flexible stoppers are pre-positioned within the MEMS actuator structure to provide cushioning before the proof mass can undergo severe impact. These stoppers engage during normal operation and provide progressive deceleration, reducing the peak forces that cause silicon chipping during drop events.
Solution Approach 2:
The solution combines multiple materials with different properties: flexible stoppers for energy absorption, brittle silicon for precise actuation, and the MEMS package structure for final stopping. This composite approach allows each material to be used in its optimal application, balancing functionality with damage resistance.
3Ease of operation
If flexible stoppers are used to decelerate the proof mass, then the motion can be controlled progressively, but multiple stoppers spaced at different distances are required to stop the mass completely along all six directions
Solution Approach 1:
The MEMS package structure serves multiple functions: it provides the housing for the actuator, supports the image sensor, and acts as the final stopping mechanism for out-of-plane motion. This multi-functionality reduces the need for separate dedicated stopping components.
Solution Approach 2:
The stopping functions for all six directions are merged into a cohesive system where flexible stoppers handle in-plane deceleration and the package structure handles out-of-plane stopping. This integration reduces overall complexity compared to having separate stopping mechanisms for each axis.
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 effectively prevents structural damage and chipping of silicon components during mechanical shocks, ensuring the functionality and image quality of MEMS actuators by decelerating and stopping the moving mass along all six directions without causing damage, thereby enhancing the drop test resistance of MEMS devices.
Implementation Method 1
a series of flexible stoppers and hard stoppers in the actuator structure to prevent failures in the image sensor loaded MEMS actuator
Implementation Method 2
MEMS electrostatic actuators that are used for achieving AF and OIS by moving image sensors in cameras
Data Source
AI summary
A MEMS actuator assembly package features a number of drop test resistant mechanisms is disclosed. These mechanisms are used to decelerate and finally stops the heavy load of the image sensor attached to the MEMS actuators along all six directions of the in-plane and out-of-plane axes (±x, ±y, ±z). The MEMS actuator assembly package comprises first and second sets of flexible stoppers attached to the MEMS actuator along with a set of hard stoppers that engage in a sequential manner with the moving mass of the loaded actuator to decelerate it, bringing it to a complete stop when exposed to mechanical shock along the four directions of the in-plane axes (x and y). When the assembly package is exposed along the positive and negative direction of the z-axis, the moving mass is stopped by features built in the package.