Resonator Bump Geometry for Thermal Stress-Stable Bonding
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Solution Overview
Problem
Existing resonator devices face issues with resonance characteristics deterioration due to thermal stress caused by the elastic modulus difference between the resonator element and the package, particularly when using metal bumps for bonding, which can lead to unstable bonding states and distorted resonance modes.
Innovation Solution
A resonator device design featuring a metal bump with a cylindrical shape and a cross-sectional area between 491 μm² and 4007 μm², optimized for bonding and electrical coupling, which reduces stress-induced distortion and stabilizes the bonding state, ensuring improved resonance characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a metal bump with high elastic modulus is used for bonding the resonator element to the base substrate, then bonding strength is improved, but resonance characteristics deteriorate due to thermal stress caused by linear expansion coefficient difference
Solution Approach 1:
The patent optimizes the cross-sectional area of the metal bump within a specific range (491 μm² to 4007 μm²) to balance bonding strength and stress reduction. This parameter change allows the metal bump to provide sufficient mechanical support while minimizing the thermal stress transmitted to the resonator element during temperature variations.
Solution Approach 2:
The patent employs a composite structure consisting of the metal bump, intermediate layer, and resonator element. This composite design allows each material to contribute its advantageous properties: the metal bump provides bonding strength, the intermediate layer buffers thermal stress, and the resonator element maintains its vibration characteristics.
2Reliability
If the cross-sectional area of the metal bump is increased to improve bonding strength, then bonding reliability is improved, but stress concentration and resonance distortion increase
Solution Approach 1:
The patent identifies and optimizes the cross-sectional area parameter of the metal bump within a specific range (491 μm² to 4007 μm²). This optimized range ensures that the bonding area is sufficient for reliable mechanical attachment while preventing excessive stress concentration that would distort the resonance mode of the resonator element.
3Reliability
If the cross-sectional area of the metal bump is decreased to reduce stress, then resonance characteristics are improved, but bonding strength is insufficient
Solution Approach 1:
The patent establishes a minimum cross-sectional area threshold (491 μm²) for the metal bump to ensure adequate bonding strength. This parameter optimization guarantees that the metal bump can withstand mechanical loads while maintaining acceptable stress levels that do not degrade resonance characteristics.
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 optimized metal bump design enhances bonding strength and temperature characteristics, providing stable resonance performance and reducing the influence of thermal stress, thus maintaining desired resonance characteristics.
Implementation Method 1
a metal bump disposed between the base substrate and the resonator element, the metal bump being configured to bond the base substrate and the resonator element
Implementation Method 2
an ultrasonic wave is applied while a pressure is applied using a metal bump having a convex top portion to the quartz crystal resonator element
Data Source
AI summary
A resonator device includes: a base substrate having a first surface and a second surface in a front-to-back relationship with the first surface; a resonator element located on a first surface side of the base substrate and including a resonator substrate and an electrode terminal disposed at a base-substrate-side surface of the resonator substrate; a mounting terminal disposed at the first surface; and a metal bump disposed between the base substrate and the resonator element, the metal bump being configured to bond the base substrate and the resonator element and electrically couple the mounting terminal and the electrode terminal. A cross-sectional area of the metal bump at a bonding portion with the resonator element is 491 μm2 or more and 4007 μm2 or less.