Polyimide Film Composition for Flexible Circuit Boards
Solution Overview
Problem
Conventional polyimide resins used in flexible printed circuit boards have high water absorption rates, leading to increased dielectric loss factors and transmission losses, especially in humid environments, and existing alternatives like liquid-crystal polymers suffer from low adhesion to metal foils, low thermal tolerance, and poor operability.
Innovation Solution
A polyimide film composition is developed by reacting specific aryl-moiety-containing dianhydrides with aryl-moiety-containing diamines at specific molar ratios, resulting in a film with low dielectric coefficients and loss factors, superior adhesive strength, thermal tolerance, and chemical resistance, while maintaining a low water absorption rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional polyimide resin is used, then thermal stability and insulation properties are achieved, but water absorption rate is high leading to increased dielectric loss factor
Solution Approach 1:
The patent modifies the chemical structure of polyimide by introducing fluorinated aromatic diamine components and controlling the molar ratio of reactants to achieve low water absorption rate (≤0.8%) and low dielectric loss factor (≤0.004 at 10 GHz) while maintaining thermal stability with Tg ≥ 200°C
Solution Approach 2:
The invention creates a composite polyimide system by reacting multiple dianhydrides (Formula I and Formula II) with fluorinated aromatic diamines (Formula III) in specific molar ratios, combining the advantages of different monomer units to achieve both low water absorption and high thermal stability
2Object-affected harmful factors
If liquid-crystal polymer is used to reduce water absorption rate, then dielectric characteristics are improved, but adhesion to metal foil and thermal tolerance deteriorate
Solution Approach 1:
The patent adjusts the chemical composition parameters by incorporating fluorinated aromatic diamines with specific molecular structures (Formula III) that provide both low water absorption and high adhesion to metal foils, achieving adhesion strength ≥ 500 g/cm while maintaining Tg ≥ 200°C
Solution Approach 2:
The invention introduces specific functional groups and molecular structures at local regions of the polymer chain through the use of fluorinated aromatic diamines, creating areas with enhanced adhesion properties and thermal stability without compromising the overall low water absorption characteristics
3Temperature
If polyimide resin is used for flexible printed circuit boards, then thermal stability is achieved, but transmission loss increases in high-frequency applications
Solution Approach 1:
The patent optimizes the dielectric properties by controlling the molecular structure and composition of polyimide, achieving low dielectric constant (3.8-4.2) and low dielectric loss factor (≤0.004 at 10 GHz) while maintaining thermal stability with Tg ≥ 200°C, thereby reducing transmission loss in high-frequency applications
Data Source
AI summary
A polyimide, a film composition, and film prepared from the same are provided. The polyimide is a product of a reactant (a) and a reactant (b). The reactant (a) consists of a first dianhydride and a second dianhydride. The first dianhydride has a structure represented by Formula (I) and the second dianhydride has a structure represented by Formula (II)wherein R1, R2 and Ar1 are as defined in specification. The reactant (b) includes a first diamine, wherein the first diamine isand R3, R4, R5, or R6 are as defined in specification.