Polyimide Resin Composition for Flexible Wiring Boards
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Solution Overview
Problem
Current methods for manufacturing printed wiring boards face challenges in achieving high-density continuity between conductive layers due to limitations in processing techniques, such as laser drilling and chemical etching, which are costly and inefficient, and result in insufficient etching rates and adhesion issues with polyimide materials.
Innovation Solution
A resin composition containing a polyimide with acidic functional groups and a compound that reacts with these groups, optimized for high alkali solubility, heat resistance, and embeddability, allowing for efficient via hole formation and thin plating, while maintaining insulation reliability and bendability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If chemical etching is used to form via holes and through holes, then continuous production by roll-to-roll method is enabled, but strong reducing agents such as hydrazine are needed which inhibit popularization
Solution Approach 1:
The patent changes the chemical parameters of the etching system by using aqueous sodium hydroxide instead of strong reducing agents like hydrazine. This parameter change maintains the ability to etch polyimide while eliminating the safety and environmental issues associated with hazardous chemicals, enabling both continuous production and safe manufacturing
Solution Approach 2:
The patent employs readily available and inexpensive aqueous sodium hydroxide as the etching agent, replacing expensive and hazardous chemicals. This approach uses a simple, easily disposed-of etchant that can be applied in continuous roll-to-roll processes without requiring complex handling or disposal systems
2Temperature
If polyimide is used as interlayer insulating film, then heat resistance is achieved, but solubility in aqueous sodium hydroxide is low resulting in insufficient etching rate
Solution Approach 1:
The patent creates a composite material system by incorporating alkali-soluble functional groups (such as carboxyl groups) into the polyimide structure. This composite approach combines the heat resistance of polyimide with the alkali solubility needed for high etching rates in aqueous sodium hydroxide, achieving both thermal stability and manufacturing efficiency
Solution Approach 2:
The patent modifies the chemical structure of polyimide by introducing alkali-soluble functional groups, changing its solubility parameters without compromising thermal properties. This structural modification enables the material to maintain heat resistance while becoming highly soluble in aqueous sodium hydroxide for rapid etching
3Productivity
If adhesive composition using polyimide having alkali soluble functional groups and oxazoline compound is used to improve solubility in alkali solution, then etching rate is improved, but crosslinking reaction proceeds at low temperatures causing decrease in alkali solubility
Solution Approach 1:
The patent applies preliminary protective measures by carefully controlling the crosslinking process to preserve alkali solubility. The crosslinking is designed to occur in a manner that does not eliminate the alkali-soluble functional groups, allowing the material to maintain both improved etching rate and sufficient alkali solubility for via hole formation
Solution Approach 2:
The patent optimizes the crosslinking parameters and functional group ratios to achieve a balance where crosslinking provides structural integrity while preserving enough alkali-soluble groups for etching. By adjusting the density and distribution of alkali-soluble functional groups, the material achieves both rapid etching and maintained solubility
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 resin composition enables improved alkali processability, embeddability, heat resistance, and adhesion to conductive layers, facilitating high-density interconnects and thin plating, while ensuring insulation reliability and bendability in multilayer printed and flexible wiring boards.
Implementation Method 1
containing (A) a polyimide having acidic functional groups and (B) a compound having functional groups that react with the acidic functional groups
Implementation Method 2
by heating in removing a solvent from the resin composition layer
Implementation Method 3
after a heat history of 180° C. for 60 minutes
Implementation Method 4
a solution rate of the resin composition in 3 mass % aqueous sodium hydroxide at 45° C.
Data Source
AI summary
A resin composition containing (A) a polyimide having acidic functional groups and (B) a compound having functional groups that react with the acidic functional groups, where (a) a solution rate in 3 mass % aqueous sodium hydroxide at 45° C. is 0.95 or more after a heat history of 90° C. for 10 minutes with the solution rate before the heat history assumed to be 1, (b) the solution rate in 3 mass % aqueous sodium hydroxide at 45° C. ranges from 0.001 μm/sec to 0.02 μm/sec after the heat history of 180° C. for 60 minutes, (c) a bleed-out amount is 50 mg/m2 or less in storing at 40° C. for 2 weeks after the heat history of 180° C. for 60 minutes, and (d) a thermogravimetric decrease at 260° C. is 2.0% or less in measuring on a temperature rising condition of 10° C./min from 40° C. by thermogravimetric analysis (TG). When a multilayer flexible wiring board is manufactured using the resin composition, it is possible to obtain the resin layer excellent in alkali processability, embeddability in press, heat resistance, bendability, insulation reliability, and adhesion to the conductive layer.