Silver-Palladium Conductor Paste for Low-Temperature Ceramic Substrates
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Solution Overview
Problem
Existing conductor pastes for ceramic substrates face challenges in achieving strong adhesion at low firing temperatures below 650°C, as sintering of conductive powders is insufficient, leading to weak bonds between the ceramic substrate and the conductor film.
Innovation Solution
A conductor paste comprising a conductive metal powder with an average particle diameter of not more than 1.2 μm, a Bi2O3—SiO2—B2O3 type glass powder, and an organic solvent, applied and fired at not more than 650°C, enhancing sintering and adhesive strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the firing temperature is reduced to not more than 650°C to reduce manufacturing cost and environmental impact, then energy consumption is reduced and lead/cadmium can be eliminated, but adhesive strength between the conductor film and ceramic substrate deteriorates due to insufficient sintering
Solution Approach 1:
The invention changes the chemical composition parameters of the glass powder to a specific Bi2O3-SiO2-B2O3 system with controlled ratios, which enables the glass to exhibit enhanced reactivity and bonding capability at lower firing temperatures (≤650°C), thereby maintaining strong adhesion without requiring high temperature sintering
Solution Approach 2:
The invention uses a composite glass powder system comprising Bi2O3, SiO2, and B2O3 in specific proportions, where each component contributes different properties: Bi2O3 provides low-temperature melting and wetting, SiO2 provides structural framework and adhesion, and B2O3 enhances glass network formation. This composite approach enables strong bonding at reduced firing temperatures
2Strength
If glass frits with low softening points are used to promote good adhesion at low firing temperatures, then adhesive strength is improved, but sintering becomes deficient and strong bonds cannot occur
Solution Approach 1:
The invention modifies the chemical composition parameters of the glass powder to a specific Bi2O3-SiO2-B2O3 system with controlled ratios, which enables the glass to exhibit enhanced reactivity and bonding capability at lower firing temperatures (≤650°C), thereby maintaining strong adhesion without requiring high temperature sintering
Solution Approach 2:
The invention uses a composite glass powder system comprising Bi2O3, SiO2, and B2O3 in specific proportions, where each component contributes different properties: Bi2O3 provides low-temperature melting and wetting, SiO2 provides structural framework and adhesion, and B2O3 enhances glass network formation. This composite approach enables strong bonding at reduced firing temperatures
3Strength
If the conductive metal powder particle diameter is reduced to enhance sintering at low temperature, then adhesive strength is improved, but manufacturing precision and control become more difficult
Solution Approach 1:
The invention optimizes the particle diameter parameter of conductive metal powder to not more than 1.2 μm, which provides sufficient surface area for bonding while remaining manufacturable. This parameter, when combined with the specific glass composition, enables effective low-temperature sintering without requiring extremely fine particles that would be difficult to control
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 solution provides excellent adhesive strength between the ceramic substrate and the conductor film, maintaining strength even after high-temperature aging and thermal cycles, while being lead-free and cadmium-free.
Implementation Method 1
sintering may be deficient and strong bonds may not occur, limiting adhesion
Implementation Method 2
the process of screen printing, drying and firing
Data Source
AI summary
A conductor paste for a ceramic substrate contains a) a conductive metal powder comprising a silver powder and a palladium powder; b) a glass powder; and c) an organic solvent, wherein the conductive metal powder has an average particle diameter of not more than 1.2 μm, and the glass powder is a Bi2O3—SiO2—B2O3 type glass powder, and the content of the glass powder is in a range of from 1 to 6 wt % based on the weight of the paste.