PCB Inkjet Ink Composition for Adhesion on Untreated Copper
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Solution Overview
Problem
Existing radiation curable inkjet inks for printed circuit boards face challenges in achieving excellent adhesion on untreated copper substrates under severe soldering and ENIG plating conditions, particularly in flexible PCBs, where conventional pretreatments to enhance adhesion can thin the copper circuitry and complicate the manufacturing process.
Innovation Solution
A radiation curable inkjet ink formulation comprising a polymerizable compound and an adhesion promoter with a nitrogen-containing heteroaromatic ring, such as N-alkylated imidazole, is developed to improve adhesion on untreated copper, eliminating the need for additional surface treatments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional pretreatments (micro-etching) are applied to copper substrates to improve adhesion, then adhesion strength is improved, but copper circuitry thickness is reduced and manufacturing complexity increases
Solution Approach 1:
The inkjet ink itself contains adhesion promoters (nitrogen-containing heteroaromatic rings) that are applied in advance to the copper substrate during the printing process, eliminating the need for separate pretreatment steps like micro-etching. This preliminary incorporation of adhesion-promoting functionality into the ink formulation prevents copper removal while ensuring strong adhesion.
Solution Approach 2:
The invention changes the chemical composition parameters of the inkjet ink by incorporating specific adhesion promoters with nitrogen-containing heteroaromatic rings (such as triazoles, tetrazoles, imidazoles, pyridines, pyrimidines, pyridazines, or triazines). This chemical parameter change enables the ink to bond effectively to untreated copper surfaces without requiring physical pretreatments that would remove copper material.
2Strength
If primers or surface treatment solutions are applied to improve adhesion, then adhesion is improved, but process complexity and production cost increase
Solution Approach 1:
The invention merges the functions of the solder mask ink and the adhesion promoter into a single integrated inkjet ink formulation. The adhesion promoter is incorporated directly into the ink composition along with the polymerizable compound and other ink components, eliminating the need for separate primer application steps and reducing manufacturing process complexity.
Solution Approach 2:
The inkjet ink serves multiple functions simultaneously: it provides the solder mask functionality, contains adhesion promoters for bonding to copper, and eliminates the need for separate pretreatment or primer steps. This multi-functionality is achieved by incorporating nitrogen-containing heteroaromatic rings that provide adhesion promotion while the ink maintains its primary solder mask properties.
3Strength
If adhesion promoters with nitrogen-containing heteroaromatic rings are incorporated into the inkjet ink, then adhesion on untreated copper is improved, but ink formulation complexity increases
Solution Approach 1:
The invention modifies the chemical composition parameters of the inkjet ink by incorporating specific adhesion promoters containing nitrogen-containing heteroaromatic rings (triazoles, tetrazoles, imidazoles, pyridines, pyrimidines, pyridazines, or triazines). These chemical parameter changes enable the ink to bond to untreated copper while maintaining compatibility with the existing inkjet printing system and curing process.
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 inkjet ink achieves improved solder and ENIG resistance, ensuring strong adhesion on copper substrates without requiring pretreatments, thus simplifying the manufacturing process and reducing costs.
Implementation Method 1
radiation curable inkjet ink
Data Source
AI summary
A radiation curable composition comprising at least one polymerizable compound and an adhesion promoter, characterized in that the adhesion promoter includes: —a polymerizable group selected from the group consisting of an acrylate, a methacrylate, an acrylamide, a methacrylamide, a styrene, a maleimide, a vinyl ether and a vinyl ester; and—an adhesion promoting group containing at least one nitrogen containing five or six membered heteroaromatic ring.