Flexible Strip Aspect Ratio via Deep Reactive Ion Etching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Flexible pivots made of micromachinable materials like silicon have limited aspect ratio, leading to restricted maximum angular excursion, low shock resistance, and inadequate out-of-plane stiffness, making them sensitive to position and prone to anisochronism and breakage.
Innovation Solution
Increasing the aspect ratio of flexible strips by a multiplicative factor of two through advanced etching techniques, such as deep etch machining, to enhance angular travel, shock resistance, and out-of-plane stiffness, while maintaining thermal adjustability of Young's modulus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If conventional etching techniques are used to manufacture flexible strips, then manufacturing precision is maintained, but the aspect ratio is limited resulting in restricted angular excursion and low shock resistance
Solution Approach 1:
The patent applies deep reactive ion etching (DRIVE) to create flexible strips with significantly increased aspect ratios by etching deeply in the vertical dimension while maintaining controlled lateral dimensions. This dimensional approach allows achieving aspect ratios of 10:1 or higher, enabling greater angular excursion and improved shock resistance without sacrificing manufacturing precision through controlled etching parameters
Solution Approach 2:
The patent modifies etching parameters including using specific gas mixtures (CHF3, CF4), controlling etching depth, and adjusting plasma power to achieve the desired high aspect ratio geometry. By changing these process parameters, the flexible strips attain optimized dimensions for enhanced performance while maintaining manufacturing control
2Reliability
If the aspect ratio of flexible strips is increased to improve angular excursion and shock resistance, then out-of-plane stiffness is enhanced, but manufacturing complexity increases
Solution Approach 1:
The patent replaces conventional mechanical shaping methods with plasma-based deep reactive ion etching to achieve high aspect ratio structures. This substitution allows complex geometries to be created through controlled chemical processes rather than mechanical means, enhancing shock resistance while managing manufacturing complexity through process integration
3Reliability
If flexible pivot bearings are used to eliminate contact friction, then quality factor is increased, but parasitic motion of the instantaneous axis of rotation occurs making the resonator sensitive to position
Solution Approach 1:
The patent optimizes the geometric parameters of the flexible strips including width, thickness, and length to achieve the desired aspect ratio. By carefully controlling these parameters through precise etching, the flexible pivot maintains high quality factor while reducing parasitic motion and position sensitivity through optimized elastic properties
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 increased aspect ratio allows for greater angular excursion, improved shock resistance, and enhanced out-of-plane stiffness, reducing sensitivity to position and temperature variations, thus optimizing the performance of timepiece resonators and flexible pivots.
Implementation Method 1
etching said plate, to a lower etching depth than said required thickness, tapered from an upper side at each said upper window, and reverse-tapered from a lower side at each said lower window
Data Source
AI summary
A method for manufacturing a flexible strip, including forming a plate of the required thickness with one or more micromachinable substrate wafers; affixing, on either side of the plate, an upper mask with an upper window and a lower mask with a lower window, of identical geometry; etching the plate, at least to mid-thickness, from the upper side of each upper etching window, and from the side of each lower etching window; removing the upper mask and the lower mask, to delimit a flexible strip having a height equal to the thickness of the plate, and whose edges are as-etched. A flexible strip made of micromachinable material, including, between two parallel upper and lower surfaces, two peripheral, tapered and reverse-tapered edge surfaces, for a flexible pivot, a resonator, a movement or a watch.