Radiation-Curable Inkjet Ink with Phenolic Resin for PCB Adhesion

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Solution Overview

Problem

Existing radiation curable inkjet inks used in PCB manufacturing face challenges with adhesion to substrates under severe conditions such as soldering and ENIG plating, and often suffer from stability issues due to the presence of adhesion promoters.

Innovation Solution

A radiation curable inkjet ink formulation incorporating a phenolic resin and thermal cross-linking agents, such as isocyanate and triazine compounds, which enhances adhesion and stability without the need for adhesion promoters.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If adhesion promoters (acid containing compounds) are added to improve adhesion, then adhesion to substrates improves, but ink stability deteriorates

Engineering Contradiction:

ImproveadhesionVSAvoidink stability

Core Design Contradiction:

StrengthVSStability of the object's composition

Solution Approach 1:

The patent removes adhesion promoters from the ink formulation entirely, replacing them with phenolic resins that provide adhesion through a different mechanism. This extraction of the problematic component (adhesion promoters) eliminates the stability issue while maintaining adhesion performance through the phenolic resin's inherent properties.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent uses composite material systems combining phenolic resins with specific monomers and oligomers to achieve both adhesion and stability. The phenolic resin acts as a backbone providing adhesion, while the polymerizable groups enable crosslinking to form a stable cured network, creating a composite material that satisfies both requirements.

Inventive Principle:

Principle #40Composite materials

2Reliability

If traditional adhesion promoters are used to survive severe soldering and ENIG plating conditions, then solder and ENIG resistance improves, but ink stability deteriorates

Engineering Contradiction:

Improvesolder and ENIG resistanceVSAvoidink stability

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent changes the chemical parameters of the adhesion mechanism by replacing acid-containing adhesion promoters with phenolic resins that have different chemical properties. The phenolic resins provide adhesion through phenolic hydroxyl groups and form stable crosslinked networks, achieving reliable solder and ENIG resistance without the stability problems of traditional adhesion promoters.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If radiation curable inkjet inks are used for digital PCB manufacturing, then productivity improves, but adhesion under severe conditions deteriorates

Engineering Contradiction:

Improvedigital manufacturing efficiencyVSAvoidadhesion under soldering and ENIG plating

Core Design Contradiction:

ProductivityVSStrength

Solution Approach 1:

The patent employs composite material formulations combining phenolic resins with polymerizable compounds containing epoxide, oxetane, or other reactive groups. This composite approach enables the ink to be applied via radiation curable inkjet printing (maintaining productivity) while the phenolic resin provides the necessary adhesion strength to survive severe soldering and ENIG plating conditions.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent introduces local quality by incorporating phenolic resins with specific functional groups at strategic positions in the molecular structure. This allows the ink to maintain good flow and printing characteristics (for productivity) while having localized adhesion-promoting phenolic groups that ensure strong bonding under severe conditions.

Inventive Principle:

Principle #3Local quality

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 demonstrates improved solder and ENIG resistance, maintaining adhesion and stability under harsh conditions, while avoiding the stability issues associated with traditional adhesion promoters.

Implementation Method 1

a) a phenolic resin, b) a polymerizable compound, c) a photoinitiator

Methodology Applied

Scientific EffectPhotopolymerisation: Photopolymerisation

Implementation Method 2

The radiation curable inkjet ink includes at least a phenolic resin as described below and a thermal cross-linking

Methodology Applied

Scientific EffectThermal cross-linking:

Data Source

PatentEP4032958B1Radiation curable inkjet inks

Publication Date: 2025.10.01 AGFA GEVAERT NV

AI summary

A radiation curable inkjet ink comprising a polymerizable compound, a phenolic resin and a thermal cross-linking agent, characterized in that the phenolic resin includes at least one structural moiety according to Formula I, wherein L represents a divalent linking group having no more than 10 carbon atoms; n represents 0 or 1; R1 and R2 independently from each other represent a group selected from the group consisting of a hydrogen, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, a substituted or unsubstituted alkaryl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted (hetero)aryl group and a substituted or unsubstituted alkoxy group.