Copper Joining Paste Composition for Low-Hydrogen Sinter Bonding
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Solution Overview
Problem
Conventional copper pastes for joining require high pressure or a reducing gas atmosphere containing hydrogen to achieve sufficient joining strength, which can lead to decreased mass production yield and long-term reliability, and pose safety concerns due to the need for explosion-proof facilities.
Innovation Solution
A copper paste formulation containing submicro and micro copper particles, dimethylglutaric acid as a polycarboxylic acid, and dihydroterpineol as a dispersion medium, allowing for sufficient joining strength without hydrogen in the gas atmosphere, enabling non-pressurization joining and use in non-explosion-proof apparatuses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional copper paste is heated under a reducing gas atmosphere containing hydrogen to achieve sufficient joining strength, then joining strength is improved, but safety concerns increase due to explosion risks and facility complexity
Solution Approach 1:
The patent replaces the hydrogen-based reducing gas atmosphere with an inert gas atmosphere (nitrogen or argon) for heating the copper paste during joining. This eliminates the explosion risk associated with hydrogen while maintaining the necessary heating conditions for achieving sufficient joining strength. The inert atmosphere prevents oxidation of copper particles during heating without requiring explosion-proof facilities.
2Strength
If high pressure is applied during thermocompression bonding to achieve sufficient joining strength, then joining strength is improved, but mass production yield and long-term reliability decrease
Solution Approach 1:
The patent modifies the chemical composition parameters of the copper paste by incorporating specific organic compounds (carboxylic acids with 1-10 carbon atoms and/or hydroxycarboxylic acids with 5-10 carbon atoms) alongside traditional dispersants. This compositional parameter change enables the copper paste to achieve sufficient joining strength under reduced pressure conditions, eliminating the need for high-pressure thermocompression bonding and thereby improving long-term reliability.
3Strength
If high pressure is applied during thermocompression bonding to achieve sufficient joining strength, then joining strength is improved, but production efficiency decreases due to process complexity
Solution Approach 1:
The patent changes the chemical composition parameters of the copper paste by incorporating specific organic compounds (carboxylic acids with 1-10 carbon atoms and/or hydroxycarboxylic acids with 5-10 carbon atoms) that enable effective joining under reduced pressure conditions. This parameter modification simplifies the joining process by eliminating high-pressure equipment requirements, thereby improving mass production yield and production efficiency.
4Ease of manufacture
If conventional copper paste is used without hydrogen atmosphere to simplify the process, then safety and facility complexity are improved, but joining strength becomes insufficient
Solution Approach 1:
The patent creates a composite copper paste formulation that combines copper particles with specific organic compounds (carboxylic acids with 1-10 carbon atoms and/or hydroxycarboxylic acids with 5-10 carbon atoms) and dispersants. This composite material structure enables the paste to achieve sufficient joining strength in simplified processes without requiring hydrogen atmosphere, thus resolving the contradiction between process simplicity and joining strength.
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 copper paste achieves strong interactions between copper particles even in nitrogen or low hydrogen atmospheres, ensuring high joining strength and stability, reducing production costs and safety concerns while simplifying the joining process.
Implementation Method 1
heating the laminate under a gas atmosphere having a hydrogen concentration of 4.5% or less to sinter the copper paste for joining of the laminate
Implementation Method 2
a copper paste formulation containing submicro and micro copper particles, dimethylglutaric acid as a polycarboxylic acid, and dihydroterpineol as a dispersion medium, allowing for sufficient joining strength without hydrogen in the gas atmosphere
Data Source
Figure 1(a)~1(b)
Figure 2(a)~2(c)
Figure 3(a)~3(c)
AI summary
A copper paste for joining contains copper particles, a polycarboxylic acid having a melting point of 120°C or lower, and a dispersion medium. A method for manufacturing a joined body includes a first step of preparing a laminate in which a first member, a copper paste for joining, and a second member are laminated in this order, and a second step of heating the laminate under a gas atmosphere having a hydrogen concentration of 45% or less to sinter the copper paste for joining. Ajoined body includes a first member, a second member, and a sintered body of a copper paste for joining that joins the first member and the second member.