Bonding Conductive Paste Composition for Bleed- and Void-Suppressed Printing
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Solution Overview
Problem
Conductive pastes containing ether-based solvents suffer from solvent bleeding and void generation, leading to printing defects and poor bondability, especially in large electronic chips.
Innovation Solution
A bonding conductive paste comprising electrically conductive particles, a hydroxy group-containing ether-based solvent, and a urea compound, with specific mass ratios and formulations to suppress solvent bleeding and void generation during sintering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conductive paste containing an ether-based solvent is used, then good wettability to substrate is achieved, but solvent bleeding occurs causing printing defects
Solution Approach 1:
A urea compound is introduced as an intermediary substance between the ether-based solvent and the substrate. The urea compound suppresses the direct interaction between the solvent and substrate that causes bleeding, while still allowing adequate wetting for proper adhesion. This mediator resolves the contradiction by controlling solvent behavior during the printing and drying process.
Solution Approach 2:
The patent modifies the chemical composition parameters of the conductive paste by adding the urea compound at specific concentrations (0.1-2 parts by mass relative to 100 parts by mass of electrically conductive particles). This parameter change alters the solvent's interaction properties with the substrate, suppressing bleeding while maintaining wettability.
2Reliability
If a conductive paste containing an ether-based solvent is used, then good wettability to substrate is achieved, but void generation occurs reducing bondability
Solution Approach 1:
The urea compound acts as an intermediary that controls solvent evaporation behavior. It prevents rapid solvent loss that would create voids, while still allowing the solvent to provide necessary wetting for strong bonding. This resolves the contradiction between maintaining wettability and preventing void formation that weakens bonds.
Solution Approach 2:
The urea compound provides beforehand cushioning by suppressing premature solvent evaporation during the drying process. This prevents the formation of voids before bonding occurs, ensuring that the solvent remains available to facilitate strong adhesion between the conductive paste and substrate.
3Area of stationary object
If a large chip having an area of 10 mm square or more is processed, then mounting capacity is increased, but solvent does not volatilize sufficiently causing void generation
Solution Approach 1:
The addition of the urea compound changes the evaporation kinetics parameters of the solvent system. It modifies the solvent's vapor pressure and evaporation rate characteristics, enabling sufficient volatilization even across large chip areas of 10 mm square or more, thereby preventing void generation in large-scale applications.
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 paste improves printing suitability and bondability by reducing solvent bleeding and void formation, resulting in high-strength conductive wires and joint structures for electronic elements.
Implementation Method 1
a bonding conductive paste containing electrically conductive particles, a hydroxy group-containing ether-based solvent, and a urea compound
Implementation Method 2
the conductive paste containing an ether-based solvent has good wettability to a substrate
Implementation Method 3
in a large chip having an area of 10 mm square or more, the solvent does not volatilize sufficiently, which may cause void generation
Data Source
Figure 1(a)~1(b)
Figure 2(a)~2(b)
AI summary
An object of the present disclosure is to provide a bonding conductive paste capable of suppressing solvent bleeding to improve printing suitability, and of suppressing void generation to improve bondability. The bonding conductive paste of the present disclosure contains electrically conductive particles, a dispersion medium containing a hydroxy group-containing ether-based solvent, and a urea compound. A content of the urea compound relative to 100 parts by mass of the entire dispersion medium containing the hydroxy group-containing ether-based solvent is from 1 to 20 parts by mass, or a content of the urea compound relative to 100 parts by mass of the electrically conductive particles is from 0.1 to 2 parts by mass.