Polyamic Acid Photosensitive Resin for Flexible Circuit Boards
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Solution Overview
Problem
Existing photosensitive cover films for circuit boards face limitations due to insufficient flame resistance, soldering heat resistance, flexibility, and bending resistance, making them unsuitable for high-temperature applications and repeated folding requirements.
Innovation Solution
A novel polyamic acid with a specific repeat unit structure is synthesized, combined with a photosensitive resin composition, a crosslinking agent, and a photopolymerization initiator to create a dry film that offers excellent flexibility, low stiffness, and enhanced heat resistance, suitable for use as a protection film on circuit boards.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If polyamic acid is used as a photosensitive resin for circuit board protection film, then heat resistance and flexibility can be improved, but curing temperature becomes too high (350°C or more) for PCB process compatibility
Solution Approach 1:
The patent modifies the chemical structure of polyamic acid by introducing specific repeating units with flexible side chains and adjusted molecular weight ranges (5,000-200,000), which changes the thermal properties to enable curing at lower temperatures (200-250°C) while maintaining heat resistance. This parameter change allows the material to be compatible with PCB processing temperatures.
Solution Approach 2:
The patent creates a composite photosensitive resin composition by combining polyamic acid with photopolymerization initiators, crosslinking agents, and other additives. This composite approach allows the system to achieve both low-temperature curability and high heat resistance through synergistic interactions between components.
2Ease of manufacture
If soluble polyimide is used to lower curing temperature, then curing temperature decreases, but chemical resistance and electroless gold plating property deteriorate
Solution Approach 1:
The patent controls the degree of imidation and molecular weight of the polyamic acid to optimize both curing temperature and chemical resistance. By maintaining polyamic acid structure rather than fully imidated polyimide, and controlling molecular weight within specific ranges, the material achieves low-temperature curability while preserving excellent chemical resistance and plating properties.
3Reliability
If crosslinking density is increased to improve heat resistance and chemical resistance, then reliability improves, but stiffness increases and flexibility is lost
Solution Approach 1:
The patent introduces side chains with specific local structures (including flexible alkyl groups and ether linkages) that provide localized flexibility within the polymer matrix. These local flexible segments allow the material to maintain overall high crosslinking density for heat and chemical resistance while preserving macroscopic flexibility through the compliant side chains.
Solution Approach 2:
The patent uses a composite approach combining highly crosslinked polyamic acid matrix with flexible side chain components, creating a heterogeneous structure where rigid crosslinked regions provide heat and chemical resistance while flexible side chain regions maintain overall material flexibility and bendability.
4Ease of manufacture
If thermoplastic polyimide is used to lower curing temperature, then curing temperature decreases, but glass transition temperature becomes abnormal and heat resistance deteriorates
Solution Approach 1:
The patent carefully controls the imidation degree and molecular weight parameters of polyamic acid to achieve an optimal balance. By maintaining the polyamic acid structure with controlled imidation (rather than full imidation to polyimide), the material cures at lower temperatures while the controlled molecular weight and residual amide groups preserve high heat resistance and appropriate glass transition temperature.
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 solution provides a photosensitive material with improved flexibility, heat resistance, and plating resistance, enabling its application in high-temperature processes and repeated folding without delamination, while maintaining suitable mechanical properties.
Implementation Method 1
a photosensitive resin composition, a crosslinking agent, and a photopolymerization initiator to create a dry film
Data Source
AI summary
The present invention relates to novel polyamic acid; a photosensitive resin composition satisfying excellent flexibility and low stiffness and exhibiting excellent heat resistance and plating resistance; a dry film obtained from the photosensitive resin composition; and a circuit board including the dry film.