Sealing material
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Solution Overview
Problem
Highly conductive metal pins in hermetic terminals cause large tensile stress on sealing materials during cooling, leading to cracks and potential refrigerant leakage due to significant thermal expansion differences between the metal and the sealing material.
Innovation Solution
A sealing material with a linear thermal expansion coefficient between 100×10−7/°C and 170×10−7/°C, composed of 70-100% alkali silicate glass powder, which reduces bonding temperature and increases expansion, minimizing tensile stress and enhancing compression stress compatibility with metal stems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a highly conductive metal pin is used to increase current capacity, then electrical conductivity is improved, but thermal expansion difference with sealing material increases causing tensile stress and cracks
Solution Approach 1:
The patent changes the thermal expansion parameter of the sealing material by adjusting glass composition (adding PbO, ZnO, B2O3) to match the thermal expansion coefficient of highly conductive metal pins, thereby reducing thermal stress during temperature cycles
Solution Approach 2:
The patent uses composite glass-ceramic materials combining multiple oxides (SiO2, PbO, ZnO, B2O3, Al2O3) to achieve both high thermal expansion coefficient matching metal pins and sufficient mechanical strength to resist cracking
2Stability of the object's composition
If glass composition is adjusted to increase thermal expansion coefficient, then thermal expansion matching is improved, but bonding temperature may increase
Solution Approach 1:
The patent adjusts glass composition parameters to achieve thermal expansion coefficient of 100-180×10^-7/°C while controlling bonding temperature between 700-900°C through balanced formulation of PbO, ZnO, and B2O3 content
Solution Approach 2:
The patent utilizes phase transition characteristics of glass-ceramic materials during heating to achieve both thermal expansion matching and appropriate bonding temperature through controlled crystallization and melting behavior
3Reliability
If sealing material is compressed by metal stem, then hermetic sealing is improved, but cracks may occur due to tensile stress from thermal shrinkage
Solution Approach 1:
The patent applies preliminary anti-action by pre-matching thermal expansion coefficients before assembly, preventing the generation of damaging tensile stresses during subsequent cooling and compression operations
Solution Approach 2:
The patent changes the mechanical and thermal parameters of the sealing material through composition adjustment to simultaneously achieve compressibility for hermetic sealing and resistance to thermal shrinkage stresses
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 sealing material effectively prevents cracks and ensures hermetic reliability by matching thermal expansion coefficients, thereby increasing the capacity and reliability of hermetic terminals.
Implementation Method 1
the sealing material is subjected to a large tensile stress by being pulled by the shrinking metal pin in the course of cooling to room temperature after a sealing step
Implementation Method 2
the green compact is increased in temperature from normal temperature, to thereby decompose and remove the binder and sinter the green compact
Implementation Method 3
the green compact is increased in temperature from normal temperature, to thereby decompose and remove the binder
Data Source
AI summary
A sealing material of the present invention is a sealing material for sealing a metal material, including 70 mass % to 100 mass % of glass powder including alkali silicate glass and 0 mass % to 30 mass % of ceramic powder, and having a linear thermal expansion coefficient in a temperature range of from 30° C. to 380° C. of more than 100×10−7/° C. and 170×10−7/° C. or less.