Curable Composition for Flexible Wiring Boards
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Solution Overview
Problem
Current curable compositions used in screen printing for flexible wiring boards suffer from bleeding and inadequate electrical insulation reliability, particularly when the pitch of wiring is narrowed, and existing solutions do not effectively prevent bleeding while maintaining low warpage and long-term insulation performance.
Innovation Solution
A curable composition comprising polyurethane with specific functional groups, γ-butyrolactone, diethylene glycol diethyl ether, and inorganic or organic fine particles, along with a compound having multiple epoxy groups, is used, which inhibits bleeding during screen printing and ensures low warpage and excellent electrical insulation when cured.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If inorganic filler is used to improve screen printability, then bleeding during screen printing is prevented, but electrical insulation properties deteriorate due to impurities and reaggregation products
Solution Approach 1:
The patent changes the chemical composition parameters of the resist ink by using polyurethane with specific functional groups (carboxyl, isocyanate, or cyclic acid anhydride groups) combined with carbonate bonds, replacing inorganic fillers. This parameter change maintains screen printability while eliminating the electrical insulation problems caused by inorganic filler impurities and reaggregation products.
Solution Approach 2:
The patent creates a composite material system combining polyurethane with specific functional groups and carbonate bonds in a unified molecular structure. This composite approach integrates the benefits of both polyurethane (curing reaction capability) and carbonate bonds (structural stability) while avoiding the drawbacks of separate inorganic filler additions.
2Productivity
If pitch of wiring is narrowed to meet semi-additive process requirements, then productivity is improved, but bleeding during screen printing becomes more severe
Solution Approach 1:
The patent modifies the chemical parameters of the resist ink composition by incorporating polyurethane with specific functional groups and carbonate bonds, which changes the material's flow and adhesion characteristics. This parameter change enables the resist ink to maintain proper screen printability even when wiring pitch is narrowed to 20 μm or less, supporting semi-additive process requirements.
3Ease of manufacture
If conventional curable composition is used, then curing reaction can proceed, but warpage of flexible wiring board increases and electrical insulation reliability decreases
Solution Approach 1:
The patent develops a composite curable composition combining polyurethane with specific functional groups (carboxyl, isocyanate, or cyclic acid anhydride) and carbonate bonds. This composite material structure provides both curing reaction capability and superior warpage resistance, eliminating the need to choose between manufacturability and precision.
Solution Approach 2:
The patent changes the chemical composition parameters of the curable composition by using polyurethane with specific functional groups and carbonate bonds. This parameter change improves the balance between curing reaction capability and dimensional stability, reducing warpage while maintaining electrical insulation reliability.
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 effectively prevents bleeding during screen printing, reduces warpage, and provides long-term electrical insulation reliability, making it suitable for use as a resist ink and protective film on flexible wiring boards.
Implementation Method 1
a component (a): polyurethane having a functional group capable of curing reaction
Implementation Method 2
a component (e): a compound having two or more epoxy groups in one molecule
Data Source
AI summary
It is an object of the present invention to provide a curable composition which provides a cured product excellent in low warpage properties and long-term electrical insulation reliability and causes little bleeding during screen printing. The present invention is a curable composition comprising the following components (a) to (e): a component (a): polyurethane having a functional group capable of curing reaction and a carbonate bond, a component (b): γ-butyrolactone, a component (c): diethylene glycol diethyl ether, a component (d): inorganic fine particles and/or organic fine particles, and a component (e): a compound having two or more epoxy groups in one molecule.