Sensor Substrate Ridge Portions for Gap Control

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Solution Overview

Problem

Existing physical quantity detection sensors face challenges in accurately forming gaps between movable and support portions using quartz crystal substrates due to etching anisotropy, leading to potential breakage from excessive displacement or restricted detection ranges.

Innovation Solution

A substrate configuration with ridge portions formed as etching residues, where the gap between the movable and support sections is accurately controlled by adjusting the opening widths of etching masks during wet etching, ensuring a predetermined gap that restricts excessive displacement and enhances impact resistance and detection accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a predetermined gap is provided between the mass section and the support portion to restrict excessive displacement, then impact resistance is improved, but the gap formation precision deteriorates due to etching anisotropy

Engineering Contradiction:

Improveimpact resistanceVSAvoidgap formation precision

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent introduces ridge portions as intermediary structures formed by etching residues between the movable section and support portion. These ridge portions serve as mediators that define the gap distance, allowing the gap to be precisely controlled through their formation rather than direct etching, thus resolving the contradiction between gap precision and impact resistance

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the approach from directly controlling gap distance through etching parameters to controlling the ridge portion formation parameters. By adjusting etching conditions to form specific ridge portions, the gap distance is indirectly but more precisely controlled, overcoming the limitations of direct etching anisotropy

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If the gap between movable section and support portion is made smaller to improve detection accuracy, then measurement precision is improved, but the risk of breakage increases due to excessive stress

Engineering Contradiction:

Improvedetection accuracyVSAvoidbreakage resistance

Core Design Contradiction:

Measurement precisionVSStrength

Solution Approach 1:

The patent provides beforehand cushioning by forming ridge portions that create a controlled gap structure. This pre-established structural feature prevents excessive displacement before it can cause breakage, while still allowing sufficient movement for accurate detection, thus protecting against breakage without sacrificing detection accuracy

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Measurement precision

If quartz crystal substrate is used for high precision, then measurement precision is improved, but manufacturing complexity increases due to etching anisotropy

Engineering Contradiction:

Improvedetection accuracyVSAvoidmanufacturing process complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent converts the harmful effect of etching anisotropy into a beneficial feature by utilizing the anisotropic etching behavior to automatically form ridge portions with specific geometries. What was previously a manufacturing difficulty becomes a self-organizing feature that defines the gap structure, simplifying the overall manufacturing process while maintaining high precision

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 allows for precise formation of gaps that prevent excessive deformation and breakage of the sensor substrate, achieving high impact resistance and accurate detection of physical quantities like acceleration.

Implementation Method 1

a ridge portion formed as an etching residue having a top portion on the side facing the gap portion is provided on each of facing surfaces of the movable section and the support portion in the gap portion

Methodology Applied

Scientific EffectWet etching:

Implementation Method 2

it is known that a crystal has a diamond structure and when forming the outer shape of the substrate for a sensor by wet etching, because of an etching anisotropy due to a difference in etching rate in the respective crystal axis directions of the quartz crystal

Methodology Applied

Scientific EffectEtching anisotropy: Anisotropy

Data Source

PatentUS10526197B2Substrate for sensor, physical quantity detection sensor, acceleration sensor, electronic apparatus, vehicle, and method of manufacturing substrate for sensor

Publication Date: 2020.01.07 SEIKO EPSON CORP

AI summary

A cantilever section as a substrate for a sensor includes: a base section; a movable section connected to the base section; an arm portion as a support portion extending along the movable section from the base section when viewed in a planar view as viewed from a thickness direction of the movable section; and a gap portion formed to have a predetermined gap between the movable section and the arm portion when viewed in the planar view, in which a ridge portion formed as an etching residue having a top portion on the side facing the gap portion is provided on each of facing surfaces of the movable section and the arm portion in the gap portion, and the predetermined gap is a gap between a top portion of a first ridge portion which is the ridge portion formed at one of the movable section and the arm portion, and a top portion of a second ridge portion which is the ridge portion formed at the other of the movable section and the arm portion.