Resonator Conductive Portion Charge Dissipation

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Solution Overview

Problem

Conventional resonators using MEMS technology face variations in resonant frequency due to manufacturing variations and electric charges accumulated in the insulating film on the holding portion, which can cause a Coulomb force and frequency variations.

Innovation Solution

A resonator design with a vibrating portion having a piezoelectric film and electrodes, a holding portion with an insulating film, and a conductive portion that contacts the insulating film and is electrically connected to the electrodes or grounded, to suppress the influence of electric charges on the resonant frequency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a holding portion with an insulating film is used in the resonator, then the insulating film provides electrical isolation and protection, but electric charges accumulate in the insulating film causing Coulomb force and resonant frequency variation

Engineering Contradiction:
Improveelectrical isolationVSAvoidresonant frequency stability
Core Design Contradiction:
ReliabilityVSManufacturing precision

Solution Approach 1:

A conductive portion is introduced as an intermediary element between the insulating film and the external environment. This conductive portion makes contact with the insulating film surface and provides a charge dissipation path, allowing accumulated electric charges to be released without compromising the insulating film's electrical isolation function. The conductive portion acts as a mediator that resolves the conflict between maintaining insulation and preventing charge accumulation.

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The harmful effect of charge accumulation is extracted and removed from the system by providing a dedicated charge release path through the conductive portion. Instead of allowing charges to build up in the insulating film, the conductive portion extracts these charges and dissipates them to ground or reference potential, thereby eliminating the source of Coulomb force and frequency instability.

Inventive Principle:
Principle #2Taking out (Extraction)

2Manufacturing precision

If ion beam irradiation is used for frequency adjustment, then the resonant frequency can be precisely tuned, but the insulating film on the holding portion becomes charged causing frequency variation

Engineering Contradiction:
Improvefrequency tuning precisionVSAvoidfrequency stability
Core Design Contradiction:
Manufacturing precisionVSReliability

Solution Approach 1:

The conductive portion serves as an intermediary charge management system that operates independently of the frequency tuning process. During ion beam irradiation for frequency adjustment, the conductive portion continuously provides a charge dissipation path, preventing charge accumulation even as the ion beam interacts with the insulating film. This allows precise frequency tuning to be performed without compromising frequency stability.

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The conductive portion is pre-formed on the insulating film before frequency adjustment operations. This preliminary charge dissipation pathway is already in place to handle any charge accumulation that may occur during subsequent ion beam irradiation or other manufacturing processes, preventing frequency instability before it can occur.

Inventive Principle:
Principle #10Preliminary action

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 conductive portion effectively releases electric charges accumulated in the insulating film, stabilizing the resonant frequency and ensuring more stable operation of the resonator.

Implementation Method 1

a vibrating portion (120) that has a piezoelectric film (F3), and lower and upper electrodes (E1, E2) provided to face each other with the piezoelectric film (F3) interposed therebetween, and vibrates in a predetermined vibration mode

Methodology Applied
Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

a conductive portion (236) that makes contact with the insulating film (235) of the holding portion (140) in at least a region of the holding portion (140), which faces the maximum displacement region of the vibrating portion (120)

Methodology Applied
Scientific EffectElectrical conduction: Conduction (electrical)

Implementation Method 3

irradiation of the holding portion with the ion beam causes the insulating film on the holding portion to be charged in some cases. As a result, a Coulomb force is generated between the holding portion and the vibrating portion, and the resonant frequency varies

Methodology Applied
Scientific EffectCoulomb force: Coulomb's Law

Data Source

PatentUS11329624B2Resonator and resonance device
Publication Date: 2022.05.10 MURATA MFG CO LTD
  • US11329624B2 patent drawing
  • US11329624B2 patent drawing
  • US11329624B2 patent drawing

AI summary

A resonator that includes a vibrating portion that has a piezoelectric film, and a lower and upper electrodes that face each other with the piezoelectric film interposed therebetween. Moreover, a holding portion is provided at least around a maximum displacement region of the vibrating portion and has an insulating film. A holding arm connects the vibrating portion and the holding portion, and include a conductive portion that is in contact with the insulating film of the holding portion in at least a region that faces the maximum displacement region of the vibrating portion. In addition, the conductive portion is electrically connected to the lower electrode or the upper electrode or is grounded.