Polyamic Acid Resin for Circuit Boards
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Solution Overview
Problem
Conventional photosensitive resin compositions for circuit boards suffer from poor heat resistance, flame retardancy, bending properties, and flexibility, leading to issues like delamination and oxidation during soldering, and pose environmental and health hazards due to the use of bromine-containing compounds.
Innovation Solution
A novel polyamic acid with a specific repeating unit structure is synthesized, combined with a crosslinking agent, organic solvent, and photopolymerization initiator to form a photosensitive resin composition that allows low-temperature curing, providing excellent bending properties, heat resistance, and coating resistance, while being environmentally friendly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If bromine-containing aromatic compounds or antimony compounds are added to improve flame retardancy or heat resistance, then heat resistance and flame retardancy are improved, but harmful substances are generated that violate environmental and health regulations
Solution Approach 1:
The patent changes the chemical composition parameters by using polyimide-based resin instead of conventional epoxy-acrylate resin, and eliminates harmful bromine-containing flame retardants. The polyimide structure itself provides inherent heat resistance and flame retardancy through its chemical stability and high decomposition temperature, achieving the desired performance without harmful additives.
Solution Approach 2:
The patent creates a composite photosensitive resin composition by combining polyimide base resin with specific functional groups (carboxyl, hydroxyl, or amine groups) and crosslinking agents. This composite structure achieves both excellent heat resistance and flame retardancy while maintaining environmental safety, as the polyimide backbone provides inherent protection without requiring harmful additives.
2Ease of manufacture
If polyamic acid is used to increase formability, then formability is improved, but high temperature curing (350°C or higher) is required which causes copper circuit oxidation and deterioration
Solution Approach 1:
The patent modifies the chemical structure of polyamic acid by introducing functional groups (carboxyl, hydroxyl, or amine groups) that enable lower-temperature curing. These functional groups facilitate crosslinking and curing reactions at temperatures below 350°C, preventing copper oxidation while maintaining the formability benefits of polyimide-based materials.
Solution Approach 2:
The patent uses crosslinking agents as intermediaries that facilitate the curing process at lower temperatures. The crosslinking agents react with the functional groups in the polyamic acid to form crosslinked networks at temperatures compatible with copper circuit stability, thereby enabling low-temperature curing while maintaining formability.
3Temperature
If molecular weight of polyimide is increased to achieve appropriate properties, then heat resistance and durability are improved, but compatibility with other substances is reduced and developing property is compromised
Solution Approach 1:
The patent optimizes the molecular weight parameter of polyimide to a specific range (500-50,000 g/mol) that balances heat resistance with compatibility. This optimized molecular weight range maintains sufficient thermal stability while preserving adequate compatibility with crosslinking agents and other composition components, enabling proper developing properties.
Solution Approach 2:
The patent introduces specific functional groups (carboxyl, hydroxyl, or amine groups) at local positions in the polyimide structure. These local functional groups provide sites for crosslinking and interaction with other substances, improving compatibility and developing properties without compromising the overall heat resistance provided by the polyimide backbone structure.
4Ease of manufacture
If conventional photosensitive resin composition is used, then ease of application is maintained, but delamination and oxidation occur during soldering due to poor heat resistance
Solution Approach 1:
The patent creates a composite resin composition based on polyimide that combines excellent heat resistance with good processability. The composite structure includes polyimide base resin with functional groups and crosslinking agents, achieving both thermal stability for soldering resistance and adequate ease of application through proper formulation and processing aids.
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 resulting photosensitive material exhibits high adhesive strength, low thermal expansion, high hot moisture resistance, and excellent coating resistance, overcoming the limitations of conventional compositions and ensuring uniform physical properties in dry films and circuit boards.
Implementation Method 1
a photosensitive resin composition including a polyamic acid-containing polymer resin, a crosslinking agent, an organic solvent, and a photopolymerization initiator
Data Source
AI summary
The present invention relates to a novel polyamic acid introduced with an imidazolyl group in the polymer chain, a photosensitive resin composition including the polyamic acid and that is capable of providing a photosensitive material that satisfies the characteristics of an excellent bending property and low stiffness and also exhibits excellent heat resistance and coating resistance, a dry film obtained from the photosensitive resin composition, and a circuit board including the dry film.