MEMS Out-of-Plane Stopper Structure for Impact Energy Dissipation
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Solution Overview
Problem
Existing microelectromechanical devices face limitations in the effectiveness of out-of-plane stopper structures due to the thickness of the adhesion layer, leading to suboptimal oscillation width and insufficient energy dissipation, which can result in damage to the mobile mass during high-speed impacts.
Innovation Solution
The device incorporates a microelectromechanical structure with a sensing mass oscillating perpendicular to the plane, featuring an out-of-plane stopper structure with elastic connections that absorb impact energy through rotation or translation, and a voltage-balancing structure to prevent charge transfer, allowing precise control of the gap width and energy dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the adhesion layer thickness is reduced to achieve desired gap width, then the gap width between mobile mass and stopper structures improves, but the mechanical strength and energy dissipation capacity deteriorate
Solution Approach 1:
The stopper structure is divided into multiple segments: a rigid cap portion for defining the gap width, and a flexible anchor portion for energy dissipation. This segmentation allows the cap to be thin (improving gap precision) while the anchor provides mechanical strength through its flexible design that can deform and absorb impact energy.
Solution Approach 2:
The stopper structure combines materials with different mechanical properties - the cap is made from a rigid material (such as glass-frit or ceramic) to maintain precise gap dimensions, while the anchor is made from a flexible material (such as metal or polymer) to provide energy dissipation capacity. This composite approach resolves the contradiction between precision and strength.
2Strength
If the cap stiffness is increased to maintain structural integrity, then the mechanical strength improves, but the energy dissipation capacity deteriorates
Solution Approach 1:
The stopper is segmented into a rigid cap and flexible anchor, allowing the cap to maintain structural integrity while the anchor dissipates energy through elastic deformation. The cap's rigidity ensures mechanical strength, while the anchor's flexibility enables energy dissipation during impact events.
Solution Approach 2:
The flexible anchor acts as a pre-designed cushioning element that absorbs impact energy before it can damage the mobile mass or the rigid cap. This beforehand cushioning mechanism allows the cap to remain stiff for structural integrity while the anchor provides the necessary energy dissipation pathway.
3Strength
If the adhesion layer thickness is increased to improve bonding strength, then the mechanical strength improves, but the gap width control deteriorates
Solution Approach 1:
The stopper structure separates the bonding function (handled by the anchor with flexible adhesion layer) from the gap-defining function (handled by the rigid cap). This allows the adhesion layer to be thick enough for strong bonding while the cap maintains precise gap width control through its rigid structure and precise positioning features.
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 enhances mechanical strength and reduces the risk of microcracks by optimizing the stopper structure's energy absorption, ensuring effective oscillation and signal quality while preventing damage to the sensing mass.
Implementation Method 1
A cap 10 is joined to the supporting structure 5 by an adhesion layer 11, normally a glass-frit layer.
Implementation Method 2
elastic connections 8 configured to enable oscillations of the mobile mass 7 in a sensing direction Z perpendicular to the substrate 2
Implementation Method 3
mobile mass 7, which oscillates in a sensing direction perpendicular to the plane of the structural layers and is capacitively coupled to fixed electrodes formed on the substrate
Data Source
Figure 1~4
Figure 5~6
Figure 7~8
AI summary
A microelectromechanical device includes a substrate (21), a first structural layer (23), and a second structural layer (25) of semiconductor material. A sensing mass (32; 132) extends in the first structural layer (23) and is coupled to the substrate (21) by first elastic connections (35) that oscillate in a sensing direction (Z) perpendicular to the substrate (21), with a maximum elongation with respect to a resting position. An out-of-plane stopper structure (38) includes an anchorage (39) fixed to the substrate (21) and a mechanical end-of-travel structure (40), which extends in the second structural layer (25), faces the sensing mass (32), and is separated therefrom by a gap (41) having a width (W) smaller than the maximum elongation. The mechanical end-of-travel structure (40) is coupled to the anchorage (39) by second elastic connections (42) that enable shifts of the mechanical end-of-travel structure (40) with respect to the sensing direction (Z) in response to an impact of the sensing mass (32).