Etch-Resistant Inkjet Inks for PCB Copper Adhesion
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Solution Overview
Problem
Existing etch-resistant inkjet inks for printed circuit board manufacturing fail to provide sufficient adhesion to copper surfaces throughout the manufacturing process, leading to increased costs and chemical waste due to the need for a developer step in the PCB manufacturing process.
Innovation Solution
A radiation curable inkjet ink is developed, comprising an adhesion promoter with free radical polymerizable groups, aliphatic tertiary amines, and carboxylic acid or its salt linked via a divalent linking group, which is UV curable and includes a combination of monofunctional, difunctional, and polyfunctional polymerizable compounds for improved adhesion and viscosity control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional etch-resistant inkjet inks are used, then the adhesion to copper surface is insufficient, but adding more adhesion promoters increases chemical waste and process complexity
Solution Approach 1:
The invention changes the chemical parameters of the adhesion promoter by specifying a particular molecular structure with free radical polymerizable groups, aliphatic tertiary amine, and carboxylic acid linked via divalent linking group. This specific chemical composition provides superior adhesion while being removable by alkaline stripping, thus reducing chemical waste from additional developer steps.
Solution Approach 2:
The inkjet ink formulation uses a composite adhesion promoter system combining polymerizable adhesion promoter (1-30 wt%), photoinitiator (1-10 wt%), and other ink components. This composite approach ensures both strong adhesion during etching and removability during stripping, eliminating the need for separate developer and stripping steps.
2Productivity
If the developer step is eliminated by using UV curable inkjet printing, then process efficiency improves, but adhesion reliability during intermediate wet steps becomes critical and difficult to maintain
Solution Approach 1:
The adhesion promoter is applied preliminarily through inkjet printing before etching, forming a protective layer on the copper surface. This preliminary action ensures adhesion is established before any wet processing steps, allowing the ink to remain adhered during etching, rinsing, and stripping operations without requiring intermediate drying.
Solution Approach 2:
The invention changes the chemical parameters of the adhesion promoter to include specific functional groups (free radical polymerizable groups, aliphatic tertiary amine, carboxylic acid) that provide both initial adhesion and alkaline removability. This chemical design allows the ink to maintain adhesion through wet steps while being removable by alkaline stripping bath.
3Reliability
If existing adhesion promoters are used, then some adhesion is achieved, but they fail to meet adhesion demands in all circumstances of PCB manufacturing
Solution Approach 1:
The adhesion promoter is designed with multi-functionality to perform multiple roles: (1) providing strong adhesion to copper surface, (2) resisting etching chemicals, (3) surviving rinsing and intermediate wet steps, and (4) being removable by alkaline stripping bath. This universal adhesion promoter replaces the need for different chemicals at different manufacturing stages.
Solution Approach 2:
The invention uses a composite adhesion promoter system with specific molecular structure containing free radical polymerizable groups, aliphatic tertiary amine, and carboxylic acid. This composite chemical structure provides adaptability to all manufacturing stages while maintaining reliable adhesion performance.
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 ensures reliable adhesion to copper surfaces during all stages of PCB manufacturing, reducing the need for the developer step and minimizing chemical waste, while maintaining high shelf life and industrial printing performance.
Implementation Method 1
a radiation curable inkjet ink, in particular a UV curable inkjet ink
Data Source
AI summary
A radiation curable inkjet ink including an adhesion promoter including (1) at least one a free radical polymerizable group selected from the group consisting of an acrylate, a methacrylate, an acryl amide and a methacryl amide; (2) at least one aliphatic tertiary amine; and (3) at least one carboxylic acid or salt thereof with the proviso that the carboxylic acid is linked to an aliphatic tertiary amine via a divalent linking group selected from the group consisting of an optionally substituted methylene group and an optionally substituted ethylene group.