Elastic Bump Stops for MEMS Shock Protection
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Solution Overview
Problem
MEMS devices experience chipping at corners when encountering shocks due to high impact forces, leading to reduced lifetime and increased costs, with existing bump stops providing inadequate protection.
Innovation Solution
A MEMS device design incorporating at least one primary elastic bump stop and one secondary bump stop, where the primary bump stop is situated closer to the target structure and moves to reduce the impact distance upon shock, while the secondary bump stop is farther away and provides additional restoring force to prevent stiction and chipping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional bump stops are used to protect MEMS devices from shock, then impact protection is provided, but the bump stops are too stiff and fail to effectively reduce impact forces
Solution Approach 1:
The patent changes the physical parameters of the bump stop by introducing a through-hole that passes through the entire bump stop structure. This hole creates a compliant channel that allows the bump stop material to deform more easily under impact, effectively reducing its stiffness while maintaining its protective function. The parameter change transforms the bump stop from a rigid structure to a more compliant one that can better absorb impact forces.
2Strength
If larger bump stops are used to provide better protection, then impact resistance improves, but stiction increases and device complexity increases
Solution Approach 1:
By introducing the through-hole, the patent changes the structural parameters of the bump stop, allowing it to achieve better impact resistance with a smaller overall size. The hole creates a compliant structure that increases the effective contact area during impact while reducing the bump stop's footprint, thereby decreasing stiction forces without compromising protection.
Solution Approach 2:
The through-hole creates a flexible, compliant structure within the bump stop that allows it to deform and conform during impact events. This flexibility enables the bump stop to provide adequate protection with reduced size, thereby minimizing stiction while maintaining impact resistance.
3Strength
If larger bump stops are used to reduce impact force, then protection improves, but the device footprint and complexity increase
Solution Approach 1:
The through-hole modifies the structural parameters of the bump stop, enabling it to provide adequate impact protection with a smaller overall footprint. The compliant structure created by the hole allows the bump stop to be more efficient in its protection function, reducing the space required while maintaining or improving protective capabilities.
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 design effectively reduces the impact force on the MEMS device, allowing for smaller bump stops with less stiction and increased flexibility to prevent chipping and corner impacts, thereby extending the device's lifespan and reducing costs.
Implementation Method 1
at least one elastic bump stop coupled to the proof mass and situated at a first distance from the target structure... wherein the at least one elastic bump stop moves to reduce the first distance when a shock is applied
Data Source
AI summary
A MEMS device includes at least one proof mass, the at least one proof mass is capable of moving to contact at least one target structure. The MEMS device further includes at least one elastic bump stop coupled to the proof mass and situated at a first distance from the target structure. The MEMS device additionally includes at least one secondary bump stop situated at a second distance from the target structure, wherein the second distance is greater than the first distance, and further wherein the at least one elastic bump stop moves to reduce the first distance when a shock is applied.