Photoimageable Composition for Printed Circuit Boards
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Solution Overview
Problem
Existing photoimageable compositions for printed circuit boards face issues such as brittleness, short holding time, and scum generation during development, which affect their chemical resistance and yield in alkaline etching and gold plating processes.
Innovation Solution
A negative-acting photoimageable composition comprising a polymeric binder with a specific monomer structure, a photopolymerizable compound, and a photoinitiator, where the polymeric binder contains acid functional monomers and non-acid functional monomers like benzyl (meth)acrylate, enhancing chemical resistance and alkaline etching ability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multifunctional monomers or oligomers with higher hydrophobicity are added to improve chemical resistance, then chemical resistance is improved, but brittleness increases and holding time decreases
Solution Approach 1:
The invention changes the chemical composition parameters by incorporating specific acrylate monomers (formula 1) with controlled hydrophobicity and acid functionality. This adjusts the polymer properties to achieve chemical resistance without excessive brittleness, resolving the contradiction between chemical resistance and mechanical strength
Solution Approach 2:
The invention uses composite polymer structures combining acrylate monomers with carboxylic acid groups and other functional monomers. This composite approach creates a balanced material that provides both chemical resistance and adequate flexibility, avoiding the brittleness issue
2Reliability
If multifunctional monomers or oligomers with higher hydrophobicity are added to improve chemical resistance, then chemical resistance is improved, but holding time becomes much shorter
Solution Approach 1:
The invention optimizes the acid functionality parameter (70-250 KOH mg/g) and hydrophobicity balance to achieve the desired holding time. By carefully controlling these parameters, the photoimageable composition maintains chemical resistance while extending the holding time to 30 minutes or more
Solution Approach 2:
The invention introduces local acid functionality through carboxylic acid groups in the polymer structure. This localized chemical property enables controlled interaction with alkaline developers, providing both chemical resistance during processing and adequate holding time
3Reliability
If multifunctional monomers or oligomers with higher hydrophobicity are added to improve chemical resistance, then chemical resistance is improved, but scum generation increases after development
Solution Approach 1:
The invention adjusts the acid functionality and hydrophobicity balance parameters to prevent scum generation. The specific range of acid functionality (70-250 KOH mg/g) and the presence of carboxylic acid groups ensure proper developer interaction, eliminating scum formation while maintaining chemical resistance
Solution Approach 2:
The invention converts the potential harm of hydrophobicity (which causes scum generation) into a benefit by carefully balancing it with acid functionality. The carboxylic acid groups provide controlled hydrophilicity that prevents scum formation while the acrylate backbone maintains chemical resistance
4Ease of manufacture
If the photoimageable composition is to be used in alkaline etching and gold plating processes, then manufacturing capability is improved, but yield decreases due to brittleness and scum generation
Solution Approach 1:
The invention optimizes the polymer composition parameters (acid functionality, monomer ratios, molecular weight) to achieve the right balance between manufacturing performance and yield. This ensures the photoresist works well in alkaline processes while maintaining high production yield
Solution Approach 2:
The invention uses composite polymer structures that combine multiple functional components. This composite approach provides both the manufacturing capability needed for alkaline etching and gold plating and the mechanical properties required for high yield
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 improves chemical resistance, adhesion, and yield by providing excellent alkaline etching resistance and maintaining resolution during development in an alkaline aqueous solution, as evidenced by improved thin line adhesion and resistance in gold plating and electroless nickel immersion gold tests.
Implementation Method 1
a photopolymerisation initiator
Data Source
AI summary
The present invention provides a negative-acting photoimageable composition comprising: a photoimageable composition comprising, based on the total weight of the photoimageable composition: (A) from 30 to 80 wt% of a polymeric binder; (B) from 5 to 50 wt% of a photopolymerizable compound; and (C) from 1.5 to 20 wt% of a photoinitiator, which is characterized in that the polymeric binder of component (A) contains as a polymerized unit at least one monomer of the structure of formula (1): wherein, R1 is H or methyl; and R2, R3, R4, R5 and R6 independently represent H, a halogen, or a substituted or unsubstituted C1 to C10 alkyl. The photoimageable composition of the invention is suitable for the manufacture of printed circuit boards.