Lead-Free Low Softening Point Glass Composition for Electronic Sealing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing glass compositions for sealing electronic parts, such as IC ceramic packages and quartz vibrators, face challenges with high thermal expansion coefficients and insufficient airtightness due to the use of lead, bismuth, and antimony, which are regulated substances, and alternative compositions like tin oxide and vanadium oxide exhibit poor moisture resistance and thermal stability at low temperatures.
Innovation Solution
A low softening point glass composition is developed using oxides of vanadium, phosphorous, tellurium, and iron, with optional components like manganese, zinc, tungsten, molybdenum, and barium, achieving a thermal expansion coefficient of 120×10−7/°C or lower and a softening point of 380°C or lower, while avoiding lead, bismuth, and antimony, and utilizing filler powders like niobium oxide and tantalum oxide to enhance sealing and bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If lead-free glass compositions containing bismuth oxide are used, then softening point is reduced and sealing temperature can be lowered, but bismuth is now regulated as an administrated substance
Solution Approach 1:
The patent removes bismuth oxide and other regulated substances (lead, antimony) from the glass composition entirely, replacing them with non-regulated oxide components that achieve the same low softening point effect without environmental harm
Solution Approach 2:
The patent changes the chemical composition parameters by introducing specific oxide ratios (V2O5: 40-60%, TeO2: 10-30%, P2O5: 5-20%, Fe2O3: 2-10%) that collectively achieve a softening point of 380°C or lower while maintaining all other required properties
2Temperature
If glass compositions containing tin oxide are used to achieve low softening point, then softening point is reduced, but moisture resistance and water resistance deteriorate due to valence change of tin
Solution Approach 1:
The patent eliminates tin oxide from the composition to avoid the valence change problem that causes poor moisture resistance, while achieving the same low softening point through a different oxide combination
Solution Approach 2:
The patent creates a composite glass system combining multiple oxides (V2O5, TeO2, P2O5, Fe2O3) where each component contributes specific properties: V2O5 and TeO2 lower the softening point, P2O5 enhances chemical stability and moisture resistance, and Fe2O3 provides thermal stability
3Temperature
If glass compositions containing vanadium oxide are used, then softening point is reduced to 400°C or lower, but thermal expansion coefficient becomes quite large and airtightness is insufficient
Solution Approach 1:
The patent optimizes the vanadium oxide content to a specific range (40-60%) and combines it with tellurium oxide (10-30%) and phosphorous oxide (5-20%) to balance the thermal expansion coefficient, achieving both low softening point and controlled thermal expansion without excessive air bubbles
4Temperature
If lead containing glass compositions are used for low temperature sealing, then sealing temperature can be reduced to 420°C or lower, but lead is harmful and regulated
Solution Approach 1:
The patent completely removes lead oxide from the glass composition and replaces it with a combination of non-regulated oxides that achieve the same low-temperature sealing capability without environmental or safety concerns
Solution Approach 2:
The patent develops a composite glass system where vanadium oxide, tellurium oxide, phosphorous oxide, and iron oxide work synergistically to achieve softening point of 380°C or lower, enabling low-temperature sealing without lead
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 provides reliable low-temperature sealing and bonding with improved moisture resistance and thermal stability, meeting environmental and safety regulations, and is applicable to various electronic parts including IC ceramic packages, quartz vibrators, and image displays.
Implementation Method 1
a softening point of 380° C. or lower
Implementation Method 2
a thermal expansion coefficient of 120×10−7/° C. or lower over a temperature range of 25° C. to 250° C.
Data Source
AI summary
A low softening point glass composition, which is substantially free from lead, bismuth and antimony and comprises oxides of vanadium, phosphorous, tellurium and iron, a softening point of the composition being 380° C. or lower.