Spring-Mass MEMS Resonator Structure for Low ESR and High Q

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Solution Overview

Problem

Existing MEMS resonators face challenges in maximizing the equivalent series resistance (ESR) and quality factor (Q) for low frequency clock reference applications, which affects their stability and robustness against environmental factors.

Innovation Solution

A microelectromechanical resonator design featuring a spring-mass system with symmetric weight portions and a central spring portion oriented along the silicon crystal direction, optimized for reduced ESR and enhanced Q factor, allowing for improved stability and robustness.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional quartz tuning fork resonators are used, then low frequency clock reference functionality is achieved, but cost is high, chip size is large, and robustness against shock and vibrations is poor

Engineering Contradiction:

Improverobustness against shock and vibrationsVSAvoidchip size

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent copies the functional principle of quartz tuning fork resonators using MEMS technology, creating a silicon-based resonator that replicates the tuning fork geometry and vibration mode while achieving superior mechanical robustness and smaller footprint

Inventive Principle:

Principle #26Copying

Solution Approach 2:

The patent replaces the quartz crystal material with silicon-based MEMS structure, substituting a mechanically fragile quartz system with a more robust silicon microstructure that can withstand shock and vibrations while maintaining resonant functionality

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If ESR is maximized for low frequency clock reference applications, then frequency stability is improved, but quality factor Q decreases since ESR is inversely proportional to Q

Engineering Contradiction:

Improvefrequency stabilityVSAvoidquality factor Q

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent optimizes geometric parameters of the spring-mass system including spring thickness, mass dimensions, and spring length to achieve the desired balance between ESR and Q factor for low frequency operation

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent designs the spring-mass system with specific dynamic characteristics, using symmetric mass portions and carefully engineered spring structures to control the resonant mode and achieve low frequency operation with acceptable energy loss

Inventive Principle:

Principle #15Dynamics

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 proposed resonator design achieves low ESR and high Q factor, leading to enhanced frequency stability over a wide temperature range and improved robustness against shock and vibrations.

Implementation Method 1

the resonator operates in an in-plane flexural mode. However, in certain other embodiments, the resonator operates in an out-of-plane mode. Accordingly, in certain embodiments, the resonator supports either an in-plane flexural vibration mode of operation or an out-of-plane flexural vibration mode of operation

Methodology Applied

Scientific EffectFlexural vibration: Vibration

Data Source

PatentUS12323131B2Spring-mass microelectromechanical resonator

Publication Date: 2025.06.03 KYOCERA TECH OY

AI summary

A microelectromechanical (MEMS) resonator includes a spring-mass system having a first weight portion (M1), a second weight portion (M2), and a central spring portion (SP) in between the weight portions. The weight portions are connected (or mechanically attached) to the central spring portion and thus improving stability.