Pressure Sensor Bonding Using Brittle Intermediary Base
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional pressure measuring devices face issues with bonding reliability between strain detection elements and metal diaphragms due to large differences in thermal expansion coefficients, leading to stress and potential breakage, especially in high-pressure and high-temperature environments.
Innovation Solution
A pressure detection device is designed with a metal housing and a diaphragm, where a brittle base with a high melting point is bonded to the strain detection element using a low-melting brittle material, reducing thermal expansion differences and minimizing stress during the bonding process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a diaphragm is made of stainless steel having high proof stress and high corrosion resistance, then strength and corrosion resistance are improved, but large stress is generated in the bonding layer due to large difference in thermal expansion coefficients, resulting in breakage of the strain detection element and bonding layer
Solution Approach 1:
A base made of a first brittle material (such as glass or ceramic) is introduced as an intermediary between the metal diaphragm and the strain detection element. This base serves as a thermal expansion buffer that reduces the stress transmitted to the strain detection element during cooling after bonding, while still allowing the diaphragm to be made of high-strength stainless steel.
Solution Approach 2:
The bonding structure uses a composite configuration consisting of the metal diaphragm, a brittle material base (glass or ceramic), and a low-melting brittle material bonding layer. This composite structure combines the advantages of each material: the strength of stainless steel, the thermal expansion compatibility of brittle materials, and the low-temperature bonding capability.
2Reliability
If the diaphragm is made of an Fe-Ni-Co-based alloy having a coefficient of thermal expansion close to coefficients of thermal expansion of silicon and glass, then bonding reliability is improved, but the alloy has comparatively low proof stress and is corroded in high temperature environment
Solution Approach 1:
The base made of a first brittle material acts as an intermediary that decouples the thermal expansion compatibility requirement from the diaphragm material selection. This allows the diaphragm to be made of high-strength stainless steel while the base provides the thermal expansion buffering function.
Solution Approach 2:
Different parts of the bonding structure have different material properties optimized for their specific functions: the diaphragm provides mechanical strength and corrosion resistance, the base provides thermal expansion compatibility, and the bonding layer provides low-temperature bonding. Each component is locally optimized for its specific role.
3Temperature
If a low-melting glass layer is used to bond the strain detection element to the diaphragm, then bonding at lower temperatures is achieved, but stress generated in the cooling step still causes breakage when the diaphragm has large thermal expansion coefficient
Solution Approach 1:
The base made of a first brittle material serves as a stress-buffering intermediary between the low-melting glass bonding layer and the metal diaphragm. This base absorbs and redistributes the thermal stress generated during cooling, preventing stress concentration at the bonding interface and reducing the risk of breakage.
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 enhances bonding reliability and reduces stress, ensuring accurate pressure detection even in high-temperature environments by using a low-melting brittle material that maintains physical properties and suppresses deterioration of the strain detection element.
Implementation Method 1
coefficients of thermal expansion of stainless steel and the strain detection element are largely different, and therefore large stress may be generated in the bonding layer in the cooling step in bonding
Implementation Method 2
a second brittle material having a melting point lower than a melting point of the base
Data Source
Figure 1
Figure 2~3
Figure 4~6
AI summary
Provided is a pressure measuring device that can stably bond a strain detection element even to a diaphragm made of metal having a large coefficient of thermal expansion. In order to achieve the above object, the pressure measuring device of the present invention includes: a metal housing including a pressure introduction unit and a diaphragm deformed by a pressure introduced via the pressure introduction unit; and a strain detection element for detecting strain generated in the diaphragm, wherein a base made of a first brittle material is provided on the metal housing, and the strain detection element is bonded to the base via a second brittle material having a melting point lower than a melting point of the base.