Curable PCB Solder-Mask Inkjet Composition Against Thermal Cracking

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Solution Overview

Problem

Existing inkjet inks for printed circuit board solder masks lack sufficient resistance to thermal stress, leading to issues such as cracking and reduced performance under thermal cycling.

Innovation Solution

A curable inkjet composition comprising photopolymerizable compounds, a polyester with fatty acid dimer units, and a photoinitiator, which can be UV and thermally cured, with specific viscosity and surface tension properties to enhance thermal stress resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional inkjet inks are used for solder mask printing, then the manufacturing process is simple, but the solder mask shows insufficient resistance to thermal stress and cracks appear

Engineering Contradiction:

Improvethermal stress resistanceVSAvoidinkjet composition complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent uses a composite inkjet composition containing polyester polyol with fatty acid dimer units (providing thermal stress resistance), photopolymerizable compounds (for UV curing), and optional thermal crosslinking agents. This multi-component composite system combines materials with complementary properties to achieve both thermal resistance and curability, resolving the contradiction between reliability and complexity.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent modifies the chemical composition parameters of the inkjet ink by incorporating specific polyester polyols with fatty acid dimer units and controlling the content of photopolymerizable compounds and crosslinking agents. These parameter changes enable the solder mask to withstand thermal stress while maintaining processability through UV curing.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the solder mask is made more resistant to thermal stress, then cracking is reduced, but the adhesion to copper traces and substrate may be compromised

Engineering Contradiction:

Improvecrack resistanceVSAvoidadhesion strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent creates local quality variations in the cured solder mask through the use of different functional components: polyester polyols provide thermal stress resistance in the bulk, while silane crosslinking agents and phosphonic acid compounds provide enhanced adhesion at the interface with copper traces and substrate. This localized functional distribution resolves the contradiction between crack resistance and adhesion strength.

Inventive Principle:

Principle #3Local quality

3Reliability

If a curable inkjet composition is used to improve thermal resistance, then the curing process becomes more complex, but the thermal stress resistance is significantly improved

Engineering Contradiction:

Improvethermal stress resistanceVSAvoidcuring process simplicity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent replaces traditional thermal curing or extended drying processes with UV photopolymerization curing. This substitution allows the ink to cure rapidly at room temperature or mild heating conditions, forming a crosslinked network that provides thermal stress resistance without requiring complex high-temperature curing equipment or extended processing times.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 improved resistance to thermal stress, reducing cracking and maintaining performance under thermal cycling conditions, while ensuring good adhesion and image quality.

Implementation Method 1

comprising photopolymerizable compounds and a photoinitiator

Methodology Applied

Scientific EffectPhotopolymerization: Photopolymerisation

Implementation Method 2

which can be UV and thermally cured

Methodology Applied

Scientific EffectThermal crosslinking:

Data Source

PatentEP4640772A1A curable inkjet composition for the manufacturing of printed circuit boards

Publication Date: 2025.10.29 AGFA GEVAERT NV

AI summary

A curable inkjet composition for a printed circuit board comprising one or more photopolymerizable compounds, a photoinitiator, and a polyester comprising dimerized fatty acids, wherein the amount of polyester is more than 2.5 wt% relative to the total weight of the inkjet ink composition.