Quartz Resonator Bonding Structure With Stress-Buffer Layers
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Solution Overview
Problem
Existing quartz crystal resonator devices face issues with plastic deformation of metal bumps due to thermal stress, leading to unnecessary vibration, frequency hysteresis, and deteriorated vibration characteristics.
Innovation Solution
The resonator device incorporates a base with a conductive layer and a resonator element with an electrode, using metal bumps to electrically couple them. Additionally, low elastic modulus layers are interposed between the base and the conductive layer, and between the resonator substrate and the electrode, to absorb and alleviate thermal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a metal bump with high elastic modulus is used to bond the quartz crystal resonator element to the package, then bonding strength is improved, but the metal bump is likely to be plastically deformed by thermal stress
Solution Approach 1:
A low elastic modulus layer is introduced as an intermediary between the metal bump and the quartz crystal resonator element. This intermediate layer has lower elastic modulus than the metal bump, allowing it to absorb thermal stress and prevent plastic deformation of the metal bump, thereby maintaining vibration characteristics while preserving bonding strength.
Solution Approach 2:
The elastic modulus parameter is changed by introducing a material with lower elastic modulus between the metal bump and the resonator element. This parameter change allows the structure to better accommodate thermal expansion differences, reducing stress concentration and preventing plastic deformation.
2Strength
If the metal bump is plastically deformed by thermal stress, then bonding strength is maintained, but unnecessary vibration or frequency hysteresis is generated in the resonator element
Solution Approach 1:
The low elastic modulus layer serves as a stress-absorbing intermediary that prevents the transmission of thermal stress to the metal bump and resonator element, eliminating the source of unnecessary vibration and frequency hysteresis while maintaining the bonding function.
Solution Approach 2:
The low elastic modulus layer is positioned in advance between the metal bump and the resonator element to cushion against thermal stress before it can cause plastic deformation. This preventive cushioning approach stops the generation of harmful vibrations before they occur.
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 configuration effectively prevents the plastic deformation of metal bumps, thereby maintaining the frequency characteristics and vibration quality of the resonator device, enhancing its reliability.
Implementation Method 1
the metal bump is likely to be plastically deformed by thermal stress caused by a difference in linear expansion coefficient between the quartz crystal resonator element and the package
Implementation Method 2
at least one of a first low elastic modulus layer that is interposed between the base and the conductive layer, that overlaps the metal bump in a plan view of the base, and that has an elastic modulus smaller than that of the metal bump
Implementation Method 3
a metal bump that is disposed between the base and the resonator element, and that electrically couples the conductive layer and the electrode while bonding the base and the resonator element
Implementation Method 4
a quartz crystal resonator element is fixed to a package via a metal bump
Data Source
AI summary
A resonator device includes: a base; a resonator element that includes a resonator substrate and an electrode; a conductive layer that is disposed on the base; a metal bump that is disposed between the conductive layer and the resonator element, and that electrically couples the conductive layer and the electrode while bonding the conductive layer and the resonator element; and at least one of a first low elastic modulus layer that is interposed between the base and the conductive layer, that overlaps the metal bump in a plan view of the base, and that has an elastic modulus smaller than that of the metal bump, and a second low elastic modulus layer that is interposed between the resonator substrate and the electrode, that overlaps the metal bump in the plan view of the base, and that has an elastic modulus smaller than that of the metal bump.