Inkjet Solder Resist Composition for Fine Circuit Structures
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Solution Overview
Problem
Existing solder mask technologies for circuit boards face limitations in achieving fine structures below 50 µm due to high viscosity issues, solvent usage, and complex development processes, which are resource-intensive and costly, while also lacking sufficient thermal stability and chemical resistance.
Innovation Solution
A solder mask composition comprising cationically and radically curable components, along with thermally curable groups, and photopolymerization initiators, forming an interpenetrating network without volatile solvents, allowing for low viscosity and rapid UV curing, reducing the need for thermal crosslinking and solvent use, and enhancing mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional higher-molecular-weight resins are used for inkjet printing, then thermal stability and chemical resistance are improved, but viscosity increases and structural accuracy deteriorates
Solution Approach 1:
The patent segments the curing process into two independent parts: UV curing for rapid initial structure fixation and thermal curing for final crosslinking. This allows the resin to be printed at low viscosity (with monomers) and then progressively cured, achieving both fine structural accuracy and thermal stability without the traditional trade-off.
Solution Approach 2:
The patent creates a composite curing system combining photopolymerization (UV) and step-growth polymerization (thermal) mechanisms. The composition includes both UV-curable monomers (acrylates, vinyl ethers) and thermally curable components (isocyanates, carboxylic acids), forming an interpenetrating network that delivers both low initial viscosity and high final performance.
2Ease of operation
If temperature is increased during printing to reduce viscosity, then flowability is improved, but component stability deteriorates
Solution Approach 1:
The patent changes the key parameter from temperature-based viscosity reduction to UV-initiated polymerization. The composition remains stable at room temperature during printing, then rapidly cures upon UV exposure, eliminating the need for temperature control during the printing process and preventing component degradation.
Solution Approach 2:
The patent replaces the thermal mechanism (heating to reduce viscosity) with a photchemical mechanism (UV-initiated polymerization). This substitution allows the resin to maintain low viscosity during printing through proper monomer selection while achieving rapid curing through light exposure, avoiding thermal degradation of components.
3Ease of operation
If volatile solvents are used to reduce viscosity, then printability is improved, but environmental impact and process complexity increase
Solution Approach 1:
The patent eliminates volatile solvents entirely, using instead non-volatile monomers that provide the necessary low viscosity for inkjet printing. The monomers themselves become the curable components through UV initiation, discarding the harmful solvent step and recovering material in the final cured network, simplifying the process by removing evaporation and ventilation requirements.
4Quantity of substance
If screen printing is used for application, then coverage is improved, but structural resolution deteriorates
Solution Approach 1:
The patent replaces the mechanical screen printing process with inkjet printing technology. The low-viscosity monomer composition is perfectly suited for inkjet droplet deposition, allowing direct digital writing of fine patterns without the physical mesh limitations of screen printing, achieving both adequate coverage and high structural resolution.
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
Enables the creation of fine structures with improved thermal stability, chemical resistance, and mechanical properties, such as brittleness resistance and adhesion, while minimizing solvent usage and process complexity, making it cost-effective and resource-efficient for inkjet printing.
Implementation Method 1
Crosslinking occurs via UV radiation, which triggers radical polymerization by suitable photoinitiators present in the solder resist
Data Source
AI summary
The invention relates to a solder resist for application by means of inkjet technology, wherein the composition of the solder resist has heat resistance for an inkjet system.To specify a solder resist that allows for the cost-effective and resource-efficient realization of even finer structures, in some cases < 50 µm, the composition should comprise at least the following components: - at least one monomer with at least one cationically curable group and/or at least one oligomer with at least one cationically curable group, - at least one monomer with at least one radically curable group and/or at least one oligomer with at least one radically curable group, - at least one monomer with at least one thermally curable group and/or at least one oligomer with at least one thermally curable group, - at least one radically initiating photopolymerization initiator and - at least one cationically initiating photopolymerization initiator.