Silver-Bonded Quartz Crystal Packaging for Frequency Drift Control
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Solution Overview
Problem
Quartz crystal oscillators experience reliability degradation due to bonding layers in high temperature, high shock, and high vibration applications, leading to resonance frequency drift over time, which is challenging to address effectively.
Innovation Solution
A method of packaging a quartz crystal using a sintered silver paste bonding layer in a substantially oxygen-free atmosphere, combined with an additional flexible bonding layer, to achieve a positive and negative drift in resonance frequency, respectively, resulting in a net minimal or zero drift over time, and enhanced bond strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional bonding layers are used to attach the quartz crystal, then the bonding strength is sufficient, but the resonance frequency drifts over time in high temperature and harsh environments
Solution Approach 1:
The patent changes the material composition parameters of the bonding layer by incorporating silver particles (at least 85 wt%) and sintering the layer at specific temperatures (200-350°C) to achieve a dense structure. This parameter change transforms the bonding layer from a conventional organic-based material to a silver-dominated composite, which exhibits superior thermal stability and minimal frequency drift in harsh environments.
Solution Approach 2:
The patent creates a composite bonding layer by combining silver particles with organic vehicle materials, then sintering them to form a hybrid structure. The sintered silver paste bonding layer combines the high thermal conductivity and stability of metal silver with the bonding characteristics of the organic matrix, achieving both strong adhesion and frequency stability in high-temperature applications.
2Strength
If the sintering temperature is increased to improve bond strength, then the bonding reliability improves, but the quartz crystal may be damaged or its frequency characteristics degraded
Solution Approach 1:
The patent optimizes the sintering temperature parameter to a specific range (200-350°C) that is sufficient to densify the silver particles and create strong bonds without exceeding the thermal tolerance of the quartz crystal. This controlled parameter change achieves maximum bond strength while preserving crystal integrity.
Solution Approach 2:
The patent performs preliminary curing of the silver paste at lower temperatures (e.g., 100-200°C) before the final sintering step. This preliminary action partially sets the bonding layer, reducing the risk of crystal damage during subsequent high-temperature sintering while still achieving strong final bonds.
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 significantly reduces resonance frequency drift and ensures high reliability and stability of quartz crystal oscillators in harsh environments, maintaining frequency accuracy and mechanical integrity.
Implementation Method 1
sintering the one or more silver paste layers in a substantially oxygen-free atmosphere and at a sintering temperature sufficient to cause sintering of the silver particles
Data Source
AI summary
The disclosed technology generally relates to packaging a quartz crystal, and more particularly to bonding a quartz crystal using sintering silver paste. In one aspect, a method of packaging a quartz crystal comprises attaching a quartz crystal to a package substrate using one or more silver paste layers comprising silver particles. The method additionally comprises sintering the silver paste in a substantially oxygen-free atmosphere and at a sintering temperature sufficient to cause sintering of the silver particles. The sintering is such that the quartz crystal exhibits a positive drift in resonance frequency of the quartz crystal over time. The method further comprises hermetically sealing the quartz crystal in the package substrate.