Micromechanical Z-Acceleration Sensor Perforation Layout for TGO Compensation
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Solution Overview
Problem
Existing micromechanical z-acceleration sensors face issues with temperature gradient offset (TGO) compensation, which leads to increased damping and reduced signal-to-noise performance due to the iterative replacement of large holes with smaller slits, causing higher frictional forces and Brownian noise.
Innovation Solution
The introduction of a perforation pattern with alternating first and second perforations, where first perforations have a 1:1 aspect ratio and second perforations are slits, arranged alternately in a repeating pattern, to enhance TGO compensation while minimizing damping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If large holes are replaced by smaller slits to compensate for TGO, then TGO compensation is improved, but damping increases and signal-to-noise performance deteriorates
Solution Approach 1:
The perforation pattern is segmented into different types of openings: first perforations with large holes and second perforations with smaller slits. This segmentation allows selective TGO compensation in specific regions while preserving low damping in other regions, resolving the contradiction between compensation effectiveness and signal-to-noise performance.
Solution Approach 2:
Different regions of the rocker are assigned different perforation characteristics. The first partial region contains large holes for minimal damping, while the second partial region contains smaller slits for TGO compensation. This local differentiation enables simultaneous optimization of both damping and compensation performance.
2Force
If smaller slits are used instead of large holes, then radiometric force is increased, but frictional forces increase leading to higher damping
Solution Approach 1:
The perforations are divided into two categories with different aspect ratios. First perforations with aspect ratio ≥1:1 (larger holes) minimize frictional forces, while second perforations with aspect ratio <1:1 (smaller slits) generate higher radiometric force. This segmentation allows the system to achieve sufficient radiometric force without excessive damping.
Solution Approach 2:
The perforation pattern introduces asymmetry in the rocker structure by combining different opening geometries. The asymmetric distribution of first and second perforations creates localized pressure differences that enhance radiometric force while the overall pattern maintains acceptable damping characteristics.
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 approach effectively compensates for TGO without significantly increasing damping, thereby improving the signal-to-noise ratio by reducing the need for slit replacements and minimizing frictional forces.
Implementation Method 1
The higher the temperature of the gas, the greater is also the kinetic energy of the gas particles so that they transfer an increased momentum upon collision with the MEMS surface
Implementation Method 2
An overpressure thus arises on the warmer MEMS upper side and a negative pressure is generated on the MEMS underside
Implementation Method 3
Due to the temperature gradient in the MEMS structure, a thermal creep movement of the gas occurs in each perforation hole
Implementation Method 4
which along the perforation hole channel leads to a frictional/shearing force on the MEMS structure
Implementation Method 5
This gas flow causes a pressure difference between the two ends of the perforation hole channel, which acts on the MEMS upper side/underside... Consequently, this force component of the radiometric force acts along the edge or corner of a perforation hole
Data Source
AI summary
A micromechanical z-acceleration sensor. The sensor has a substrate with a main extension plane, and a micromechanical rocker which is arranged parallel to the extension plane above the substrate and can be tilted in a first direction z perpendicular to the extension plane, wherein the rocker in a first partial region: has first perforations, which extend through the rocker in the first direction z, with a first cross-section parallel to the main extension plane with a first aspect ratio of at least 1:1; and has second perforations, which extend through the rocker in the first direction z, with a second cross-section with a second aspect ratio of a longer side to a shorter side, wherein the first aspect ratio is smaller than the second aspect ratio. A first perforation and a second perforation are arranged alternately next to one another in a repeating pattern.