Quartz Resonator Joint Structure With Stress Relaxation Layer
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Solution Overview
Problem
Quartz crystal resonator devices experience plastic deformation due to thermal stress caused by differences in linear expansion coefficients between the quartz crystal resonator element and the package, leading to unnecessary resonation or frequency hysteresis and deteriorated resonation characteristics.
Innovation Solution
Incorporating a stress relaxation layer with a smaller elastic modulus, such as a resin material like epoxy or polyimide, between the base and the conductive layer, which overlaps with the joint portion and has an exposed portion, to reduce stress and prevent plastic deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a metal bump is used to fix the quartz crystal resonator element to the package, then strong adhesion is achieved, but plastic deformation occurs due to thermal stress
Solution Approach 1:
A stress relaxation layer made of resin material (epoxy or polyimide) is introduced between the metal bump and the quartz crystal resonator element. This intermediary layer has a lower elastic modulus than the metal bump, allowing it to absorb thermal stress and prevent plastic deformation of the resonator element while maintaining the adhesion function.
Solution Approach 2:
The fixing structure uses a composite material approach by combining the metal bump (for adhesion strength) with a resin-based stress relaxation layer (for stress absorption). This composite structure leverages the advantages of both materials: the metal bump provides strong bonding while the resin layer prevents plastic deformation through its lower elastic modulus and stress relaxation properties.
2Reliability
If the elastic modulus of the stress relaxation layer is small, then stress relaxation effect is enhanced, but adhesion strength may be reduced
Solution Approach 1:
The stress relaxation layer is positioned specifically at the critical interface between the metal bump and the quartz crystal resonator element, where thermal stress concentration occurs. By applying the stress relaxation function locally at this specific location rather than throughout the entire structure, the design achieves effective stress relaxation while maintaining overall adhesion strength through the metal bump's 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 stress relaxation layer effectively minimizes unnecessary resonation and frequency hysteresis, improving resonation characteristics by reducing thermal stress and maintaining adhesion between layers.
Implementation Method 1
a stress relaxation layer that is interposed between the base and the conductive layer and that at least partially overlaps with the joint portion in a plan view of the base. The stress relaxation layer includes an exposed portion exposed from the conductive layer.
Implementation Method 2
thermal stress caused by a difference in linear expansion coefficients between the quartz crystal resonator element and the package
Data Source
AI summary
A resonator device includes: a base having a first surface and a second surface that are in front-back relation; a resonator element that is located at a first surface with respect to the base and that includes a resonation substrate and an electrode disposed at a surface of the resonation substrate on a base side; a conductive layer that is disposed at the first surface and that includes a joint portion joined to the electrode; and a stress relaxation layer that is interposed between the base and the conductive layer and that at least partially overlaps with the joint portion in a plan view of the base. The stress relaxation layer includes an exposed portion exposed from the conductive layer.