Lead-Free Conductive Composition for Low-Temperature Firing
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Solution Overview
Problem
Current conductive compositions face challenges in achieving sufficient conductivity and adhesiveness when fired at low temperatures, particularly 750° C. or less, while avoiding the use of lead-containing glass frits and minimizing damage to resistors and internal elements in electronic components.
Innovation Solution
A conductive composition comprising copper powder, cuprous oxide, a lead-free glass frit with borosilicate zinc-based and vanadium zinc-based glass frits, and a carboxylic acid-based additive, which facilitates sintering and improves adhesiveness and conductivity, allowing for firing at temperatures as low as 750° C. or less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If lead-free glass frit is used instead of lead glass frit, then environmental compliance is improved, but adhesiveness and conductivity at low firing temperatures deteriorate
Solution Approach 1:
The patent changes the chemical composition parameters of the glass frit by incorporating specific metal oxides (Bi2O3, ZnO, B2O3, SiO2) in optimized ratios. This compositional parameter change enables the lead-free glass frit to achieve appropriate softening temperature and wettability, resolving the contradiction between environmental compliance and functional performance at low firing temperatures.
Solution Approach 2:
The patent creates a composite glass frit system combining multiple oxide components (bismuth oxide, zinc oxide, boron oxide, silicon oxide) to achieve properties that individual components cannot provide alone. This composite approach enables simultaneous achievement of low softening temperature, good wettability, and environmental compliance without lead.
2Object-affected harmful factors
If firing temperature is reduced to 750°C or less, then damage to resistors and internal elements is reduced, but conductivity and adhesiveness of the conductor deteriorate
Solution Approach 1:
The patent modifies the glass frit composition parameters to achieve appropriate softening temperature (700-900°C) and wettability characteristics. This parameter optimization enables effective sintering and conductor formation at low firing temperatures (750°C or less), maintaining conductivity and adhesiveness while minimizing thermal damage to other components.
Solution Approach 2:
The glass frit acts as an intermediary material that facilitates adhesion between the conductor and substrate at low temperatures. By optimizing its composition to achieve appropriate softening temperature and wettability, the glass frit mediates the bonding process, enabling reliable conductor formation without requiring high temperatures that would damage resistors and internal elements.
3Quantity of substance
If copper is used instead of noble metals, then cost is reduced, but oxidation resistance and conductivity during firing deteriorate
Solution Approach 1:
The patent specifies firing in a nitrogen atmosphere or other inert gas environment to prevent copper oxidation during the heating process. This creates a protective inert environment that maintains copper's conductivity and prevents oxide formation, resolving the contradiction between cost reduction and oxidation resistance.
Solution Approach 2:
The glass frit composition acts as a protective intermediary that helps prevent copper oxidation during firing. The specific oxide composition creates a protective environment during the firing process, maintaining copper's metallic state and conductivity while enabling low-temperature processing.
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 composition achieves excellent conductivity and adhesiveness to substrates, enabling the formation of conductors with electric characteristics similar to conventional ones, while being lead-free and reducing defect rates, even at reduced firing temperatures.
Implementation Method 1
The glass frit has the effect of causing the conductive component to adhere together or causing a substrate and the conductive component to adhere to each other
Implementation Method 2
firing the conductive paste applied onto the substrate
Implementation Method 3
copper is oxidized, and an oxide formed during the process may reduce conductivity
Implementation Method 4
ruthenium oxide reacts with nitrogen, and a desired resistance cannot necessarily be obtained
Data Source
AI summary
A conductive composition has excellent adhesiveness to a substrate and conductivity. For example, a conductive composition contains copper powder, cuprous oxide, a lead-free glass frit, and a carboxylic acid-based additive. The cuprous oxide is contained in an amount of at least 5.5 parts by mass and up to 25 parts by mass relative to 100 parts by mass of the copper powder. The lead-free glass frit contains a borosilicate zinc-based glass frit and a vanadium zinc-based glass frit. The borosilicate zinc-based glass frit contains boron oxide, silicon oxide, zinc oxide, and optional other components, among which boron oxide, silicon oxide, and zinc oxide serve as top-three oxide components in terms of content. The vanadium zinc-based glass frit contains vanadium oxide, zinc oxide, and optional other components, among which vanadium oxide and zinc oxide serve as top-two oxide components in terms of content.