Quartz Resonating Beam Accelerometer Bonding
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Solution Overview
Problem
The sensitivity of accelerometers can be degraded due to creep of bonded joints and mismatch in the coefficient of thermal expansion between bonding materials and the attached pieces, as well as machining imperfections in the proof mass hinge, leading to reduced sensitivity and potential hinge failure.
Innovation Solution
A direct bond is formed between components of a resonating beam accelerometer using quartz material, applying predefined pressure and temperature for a specific duration to eliminate creep and thermal expansion mismatches, without the use of intermediate layers like solder or glue.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If solder or glue is used to bond resonators and damping plates to the proof mass, then the components can be joined together, but the sensitivity of the accelerometer degrades over time due to creep of the bonding material
Solution Approach 1:
The patent bonds resonators and damping plates directly to the proof mass using diffusion bonding, eliminating intermediate bonding materials. All components are made of the same single-crystal quartz material, ensuring homogeneous thermal expansion characteristics and eliminating creep-related sensitivity degradation over time.
Solution Approach 2:
The patent removes the intermediate bonding layer (solder or glue) from the assembly. By directly bonding the resonators and damping plates to the proof mass through diffusion bonding, the harmful intermediate material that causes creep is completely extracted from the system.
2Strength
If solder or glue is used to bond components, then the components can be joined, but the sensitivity degrades due to difference in coefficient of thermal expansion between the bonding material and the bonded pieces
Solution Approach 1:
All components (proof mass, resonators, damping plates) are fabricated from the same single-crystal quartz material, ensuring identical coefficients of thermal expansion. This eliminates thermal mismatch stresses and sensitivity drift that would occur with heterogeneous bonding materials.
3Ease of manufacture
If the proof mass hinge is machined by gluing or soldering thin blank between proof mass sections, then the hinge can be manufactured, but sensitivity is reduced and hinge failure may occur due to creep and CTE mismatch
Solution Approach 1:
The hinge is constructed by directly bonding thin quartz blanks between proof mass sections using diffusion bonding, eliminating solder or glue. The homogeneous quartz-material construction prevents creep and thermal mismatch, ensuring hinge durability and maintaining accelerometer sensitivity.
4Reliability
If direct bonding is used without intermediate layers, then creep and thermal expansion mismatches are eliminated, but the bonding process requires precise control of pressure and temperature
Solution Approach 1:
The diffusion bonding process utilizes controlled changes in temperature and pressure parameters to achieve direct bonding of quartz components. By heating to specific temperatures (e.g., 1000-1500°C) and applying controlled pressure, atomic diffusion occurs at the interfaces, creating strong direct bonds without intermediate materials.
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 method enhances the sensitivity and reliability of the accelerometer by creating a strong, creep-resistant bond between components made from the same material, ensuring consistent performance and preventing hinge failure.
Implementation Method 1
A direct bond is formed between the proof mass and the resonators by applying a predefined amount of pressure at a predefined temperature for a predefined amount of time
Implementation Method 2
resonating beam accelerometer (RBA)... measure acceleration as a function of the frequency difference between two sets of vibrating quartz beams
Data Source
AI summary
A method of making a resonating beam accelerometer (RBA). In an example process, a proof mass device and resonators are created from a quartz material. A direct bond is formed between the proof mass and the resonators by applying a predefined amount of pressure at a predefined temperature for a predefined amount of time. One or more damping plates are created from a quartz material. A direct bond is formed between the damping plates and the proof mass device. The proof mass device is created by applying a predefined amount of pressure at pressure at temperature to two bases, two proof mass portions, and a flexure. The proof mass bases are on opposite sides of the flexure. The proof mass portions are on opposite sides of the flexure. A gap is present between the proof mass bases and the proof mass portions.