PbO-Free TeO2-MoO3 Glass for Low-Temp Sealing
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Solution Overview
Problem
Lead borate-based glasses used for sealing electronic components face environmental concerns and struggle to balance low softening points with weather resistance, requiring a PbO-free alternative that achieves low-temperature firing while maintaining heat resistance.
Innovation Solution
A glass composition comprising 30% to 80% TeO2, 5% to 30% MoO3, and specific ranges of MgO, CaO, SrO, BaO, ZnO, along with optional additives like Li2O, Na2O, K2O, TiO2, Al2O3, CuO, WO3, and P2O5, which stabilizes the glass and allows for low-temperature sealing without lead, combined with a refractory filler powder like Zr2WO4 for enhanced mechanical strength and thermal properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If lead borate-based glass containing large amount of PbO is used to achieve low softening point for low-temperature sealing, then sealing temperature can be reduced to 400°C or less, but environmental harm increases due to PbO content
Solution Approach 1:
The invention extracts and removes PbO from the glass composition entirely, replacing it with alternative oxide combinations (TeO2-MoO3-based system with MgO, CaO, SrO, BaO, ZnO) that achieve low softening point without environmental harm. This extraction of the harmful component while maintaining functional performance resolves the contradiction between low sealing temperature and environmental safety.
Solution Approach 2:
The invention changes the chemical composition parameters of the glass system from PbO-based to TeO2-MoO3-based with specific multi-oxide combinations. By adjusting the ratios of TeO2 (30-80%), MoO3 (5-30%), and other oxides (MgO, CaO, SrO, BaO, ZnO), the glass achieves comparable or better softening point characteristics without PbO, thus resolving the environmental harm issue while maintaining low-temperature sealing capability.
2Temperature
If softening point of glass is reduced for low-temperature sealing, then sealing temperature decreases, but weather resistance of glass deteriorates
Solution Approach 1:
The invention employs a composite glass system combining multiple oxide components (TeO2, MoO3, MgO, CaO, SrO, BaO, ZnO, and optional Li2O, Na2O, K2O, TiO2, Al2O3, CuO, WO3, P2O5) that work synergistically. This composite composition achieves low softening point through TeO2-MoO3 base with alkaline earth oxides, while the specific combination and ratios of these components maintain or improve weather resistance, resolving the contradiction between low softening point and weather resistance.
Solution Approach 2:
The invention optimizes the compositional parameters of the glass system, specifically setting TeO2 at 30-80%, MoO3 at 5-30%, and controlled amounts of MgO, CaO, SrO, BaO, ZnO (1-30% total), along with optional additives. These parameter adjustments create a glass composition that simultaneously achieves low softening point (for low-temperature sealing) and maintains weather resistance through the stabilizing effect of the multi-oxide system.
3Object-affected harmful factors
If PbO-free glass is developed as alternative to lead borate-based glass, then environmental harm is reduced, but achieving both low softening point and weather resistance becomes difficult
Solution Approach 1:
The invention develops a PbO-free composite glass system based on TeO2-MoO3 with multiple alkaline earth oxides (MgO, CaO, SrO, BaO, ZnO) and optional additives. This composite material achieves environmental safety by eliminating PbO while simultaneously achieving low softening point (through TeO2-MoO3 system) and weather resistance (through the stabilizing effect of multiple oxide components working together), thus resolving the difficulty of balancing both properties in PbO-free glass.
Solution Approach 2:
The invention changes the fundamental compositional parameters from PbO-based to TeO2-MoO3-based system with specific oxide ratios. By setting TeO2 at 30-80%, MoO3 at 5-30%, and controlled amounts of other oxides, the glass achieves environmental safety (PbO-free) while maintaining the desired balance between low softening point and weather resistance through the synergistic effect of the multi-oxide composition.
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 glass composition achieves low-temperature sealing with improved weather resistance and heat resistance, preventing devitrification and maintaining thermal stability, making it suitable for electronic component sealing without the use of harmful lead.
Implementation Method 1
as the softening point of glass becomes lower, there is a tendency that vitrification is difficult or phase separation occurs, with the result that homogeneous glass is difficult to obtain. However, in the present invention, by virtue of specifying that the content of TeO2 is 30% or more and the content of MoO3 is 5% or more, the glass is stabilized, and hence homogeneous glass can be obtained.
Implementation Method 2
as the softening point of glass becomes lower, there is a tendency that vitrification is difficult or phase separation occurs, with the result that homogeneous glass is difficult to obtain.
Data Source
AI summary
Provided are a glass composition capable of sealing through low-temperature firing without containing environmentally harmful lead, and a sealing material using the same. The glass composition includes, in terms of mol %, 1%, to 30% of MgO+CaO+SrO+BaO+ZnO, 30% to 80% of TeO2, and 5% to 30% of MoO3.