Lead-Free Glass Overglaze for Acid Resistance
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Solution Overview
Problem
Existing lead-free and cadmium-free glass compositions for electronic overglazes lack sufficient acid resistance and rapid crystallization, which is crucial for demanding applications like surge resistor overglazes, and interact excessively with underlying electrical components.
Innovation Solution
A lead-free and cadmium-free glass composition that partially crystallizes at low firing temperatures, forming predominantly bismuth titanates and/or zinc titanates, providing excellent acid resistance and minimizing reactivity with electronic components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If lead-free and cadmium-free glass compositions are used, then toxicity is reduced, but acid resistance is insufficient
Solution Approach 1:
The patent changes the chemical composition parameters by incorporating specific metal oxides (Bi2O3 at 30-70 wt%, TiO2 at 10-40 wt%, ZnO at 5-30 wt%) to achieve both low toxicity and high acid resistance. This compositional parameter optimization resolves the contradiction between eliminating toxic lead/cadmium and maintaining acid resistance.
Solution Approach 2:
The patent creates a composite glass composition combining multiple oxide components (bismuth oxide, titanium oxide, zinc oxide, and optional additives) to achieve synergistic effects. This composite approach provides both the non-toxicity of lead-free materials and the acid resistance previously only achievable with lead-containing formulations.
2Ease of manufacture
If conventional lead-free glass compositions are used, then manufacturing is simpler, but crystallization is slow and interaction with electrical components occurs
Solution Approach 1:
The patent optimizes firing temperature parameters (900-1100°C) and holds them for specific durations (5-30 minutes) to achieve rapid crystallization of the glass composition. This controlled thermal parameter regime enables fast crystallization without complicating the manufacturing process, resolving the contradiction between ease of manufacture and crystallization speed.
3Reliability
If high SiO2 content is used, then acid resistance improves, but reactivity with underlying components increases
Solution Approach 1:
The patent creates a composite glass system where Bi2O3-TiO2-ZnO phases work synergistically. The bismuth titanate and zinc titanate crystalline phases formed during firing provide acid resistance through their stable crystal structures, while the specific composition ratios (30-70% Bi2O3, 10-40% TiO2, 5-30% ZnO) control reactivity with underlying electronic components, resolving the contradiction between acid resistance and component compatibility.
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 exhibits superior acid resistance and chemical durability, with weight loss less than 20% when immersed in acidic solutions, surpassing prior art compositions and ensuring the protection of electronic devices without lead or cadmium.
Implementation Method 1
The glass composition according to the invention partially crystallizes and fuses at relatively low firing temperatures. The crystals formed during firing predominantly comprise bismuth titanates and/or zinc titanates.
Implementation Method 2
The glass composition according to the invention partially crystallizes and fuses at relatively low firing temperatures.
Data Source
AI summary
The present invention provides an electronic device having a lead-free and cadmium-free glass composition applied thereto and fired to form an acid resistant overglaze, and a method of overglazing an electronic device using the lead-free and cadmium-free glass composition. The lead-free and cadmium-free glass composition fuses at low firing temperatures and is particularly suitable for use in thick film pastes. The glass composition forms predominantly bismuth titanate and/or zinc titanate crystals upon firing. Preferably, glass compositions include by weight from about 11% to about 52% SiO2, from 3.4% to about 40% TiO2, up to about 75% Bi2O3, up to about 40% by weight ZnO, where the sum of Bi2O3 and ZnO comprises from about 15% to about 85% of the glass composition by weight.