Dual-Cure PCB Inkjet Composition for Adhesion and Thermal Resistance
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Solution Overview
Problem
Existing inkjet inks for printed circuit boards (PCBs) face challenges in achieving good adhesion on various substrates, resistance to ENIG plating, and thermal stress, leading to potential cracks and poor stability during soldering and thermal cycling.
Innovation Solution
A curable inkjet composition comprising a combination of polymerizable compounds with vinyl groups, thermal cross-linking agents, and photoinitiators, utilizing dual-cure principles to form an interpenetrating polymer network, enhancing adhesion, ENIG plating resistance, and thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If adhesion promoters are added to improve adhesion on various substrates, then adhesion is improved, but ink stability deteriorates
Solution Approach 1:
The patent uses silane-modified polymerizable compounds as intermediary substances that provide both adhesion promotion and cross-linking functionality. These compounds act as mediators between the ink formulation and substrates, achieving adhesion without requiring separate adhesion promoter additives that would compromise ink stability.
Solution Approach 2:
The invention employs composite ink formulations combining multiple polymerizable compounds including silane-modified compounds, acrylic monomers, and oligomers. This composite approach creates a synergistic system where each component contributes to both adhesion and stability, eliminating the need to choose between adhesion promoters and stable formulation.
2Reliability
If the solder mask is designed to withstand severe conditions during soldering and ENIG plating, then resistance to these processes is improved, but the ink formulation becomes more complex
Solution Approach 1:
The patent designs polymerizable compounds with multiple functional groups that simultaneously provide adhesion, cross-linking, and resistance to ENIG plating and soldering. The silane-modified compounds and phenolic resin components perform multiple functions within a single formulation, reducing overall complexity despite the demanding performance requirements.
Solution Approach 2:
The invention optimizes specific parameters of the polymerizable compounds, such as the molecular weight, functional group density, and silane content, to achieve the required resistance properties. By carefully controlling these parameters within specific ranges, the formulation achieves high reliability without excessive complexity.
3Temperature
If the solder mask is made highly resistant to thermal stress, then heat resistance is improved, but the risk of cracking during thermal cycling increases
Solution Approach 1:
The patent utilizes the phase transition behavior of silane compounds during curing. The silane groups undergo hydrolysis and condensation reactions that create a flexible cross-linked network. This dynamic network structure can accommodate thermal expansion and contraction stresses, providing both heat resistance and crack resistance through controlled phase transitions during the curing process.
Solution Approach 2:
The invention creates local variations in cross-linking density within the cured ink film. The silane-modified compounds form localized cross-linked regions that provide thermal stability, while the polymerizable compound matrix provides flexibility. This local differentiation of properties allows the material to resist both high temperatures and thermal stress-induced cracking.
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 provides superior mechanical properties, improved adhesion, and enhanced resistance to thermal and chemical stress, ensuring reliable performance in PCB manufacturing processes.
Implementation Method 1
a photopolymerizable monomer with a cyclic skeleton
Implementation Method 2
a thermal cross-linking agent
Data Source
AI summary
A curable inkjet composition for a printed circuit board, comprising more than one polymerizable compound and one or more a thermal cross-linking agent; characterized in that at least one polymerizable compound is a methacrylate.