Copper Conductive Layer Coating Liquid Using Graft Copolymer Dispersant
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Solution Overview
Problem
Existing conductive layers formed on printed circuit boards using fine metal particles tend to have dense and sparse portions, leading to insufficient denseness and smoothness due to particle aggregation, which affects the electrical conductivity and adhesive strength.
Innovation Solution
A coating liquid containing copper or copper alloy fine metal particles and a polyethyleneimine-polyethylene oxide graft copolymer dispersant is applied and heated, ensuring uniform dispersion and sintering of particles to form a conductive layer with improved denseness and smoothness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fine metal particles are used to form conductive layer, then electrical conductivity is improved, but particle aggregation occurs leading to insufficient denseness and smoothness
Solution Approach 1:
The patent introduces a dispersant as an intermediary substance between fine metal particles to prevent particle aggregation. The dispersant adsorbs onto particle surfaces, creating repulsive forces that maintain uniform particle distribution during coating application, thereby achieving both good electrical conductivity and surface smoothness without direct particle-to-particle contact issues
Solution Approach 2:
The patent optimizes multiple parameters including particle size distribution, dispersant concentration, coating liquid viscosity, and drying conditions. By controlling particle size within specific ranges and adjusting dispersant-to-metal-ratio, the system achieves uniform particle packing that prevents aggregation while maintaining high conductivity and surface denseness
2Ease of manufacture
If fine metal particles are applied to base film, then conductive layer is formed, but particle migration occurs during drying leading to dense and sparse portions
Solution Approach 1:
The dispersant acts as a mediator that binds to fine metal particles and provides steric or electrostatic stabilization during the drying process. This prevents particles from migrating to areas of higher concentration, ensuring uniform distribution across the base film surface and eliminating dense-sparse portion variations
Solution Approach 2:
The patent applies preliminary stabilization treatment by incorporating dispersant into the coating liquid before application. This preliminary action ensures particles are pre-coated with protective dispersant layers, preventing migration during subsequent drying and heating steps, thereby achieving uniform conductive layer formation
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 method results in a conductive layer with enhanced denseness, smoothness, and electrical conductivity, while suppressing particle aggregation and migration, thereby improving the adhesive strength to the base film.
Implementation Method 1
the dispersant is a polyethyleneimine-polyethylene oxide graft copolymer
Implementation Method 2
a polyethyleneimine moiety in the graft copolymer has a weight-average molecular weight of 300 or more and 1,000 or less
Implementation Method 3
a heating step of, after the application, heating the coating liquid for forming a conductive layer
Implementation Method 4
heating the coating liquid for forming a conductive layer
Implementation Method 5
the sintered body includes a residue derived from a polyethyleneimine-polyethylene oxide graft copolymer
Data Source
AI summary
A coating liquid for forming a conductive layer according to the present invention is a coating liquid for forming a conductive layer, the coating liquid containing fine metal particles, a dispersant, and a dispersion medium. In the coating liquid for forming a conductive layer, the fine metal particles contain copper or a copper alloy as a main component, the dispersant is a polyethyleneimine-polyethylene oxide graft copolymer, a polyethyleneimine moiety in the graft copolymer has a weight-average molecular weight of 300 or more and 1,000 or less, a molar ratio of polyethylene oxide chains to nitrogen atoms in the polyethyleneimine moiety is 10 or more and 50 or less, and the graft copolymer has a weight-average molecular weight of 3,000 or more and 54,000 or less.