Low Dielectric Polyimide Composition for PCB Impedance Matching
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Solution Overview
Problem
Current printed circuit board (PCB) materials face challenges in achieving high-speed signal transfer due to inadequate impedance matching, which is hindered by polyimide films with high dielectric constants.
Innovation Solution
A low dielectric polyimide composition is developed, comprising aliphatic anhydrides, long chain diamines, and ester diamines, which are cyclized to form a polyimide with a dielectric constant less than 3.0 and low dielectric loss, integrated into copper clad laminates for improved impedance matching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional polyimide films are used in copper clad laminates, then the material provides adequate mechanical strength and heat resistance, but the high dielectric constant prevents effective impedance matching for high-frequency signals
Solution Approach 1:
The patent modifies the chemical composition parameters of polyimide by incorporating specific aromatic diamines with electron-withdrawing groups and controlling the molar ratios of monomers. This changes the dielectric constant from conventional values (3.5-4.5) to a reduced range (2.8-3.2), enabling impedance matching while preserving mechanical properties
Solution Approach 2:
The invention creates a composite polyimide system combining multiple diamine components (including meta-phenylenediamine and pyridine derivatives) with dianhydride monomers. This composite approach achieves synergistic effects where the combination of different molecular structures provides both low dielectric constant and high mechanical strength
2Object-affected harmful factors
If the polyimide composition is modified to reduce dielectric constant, then impedance matching improves, but mechanical strength and chemical resistance may be compromised
Solution Approach 1:
The patent introduces functional groups with specific local electronic properties (electron-withdrawing groups like pyridine rings) at strategic positions within the polyimide molecular structure. This local modification of electronic density reduces dielectric constant while the overall molecular backbone maintains mechanical integrity
Solution Approach 2:
The invention optimizes the molecular weight and polydispersity parameters of the polyimide through controlled polymerization. By adjusting these parameters along with compositional ratios, the material achieves simultaneous improvement in dielectric properties and maintenance of mechanical strength
3Productivity
If conventional polyimide formulations are used, then manufacturing process is simple and cost-effective, but high-frequency signal transfer performance is insufficient
Solution Approach 1:
The patent develops a polyimide formulation that simultaneously achieves multiple functions: low dielectric constant for signal integrity, high heat resistance for manufacturing stability, and good mechanical properties for structural integrity. This multi-functional material simplifies the need for additional specialized layers or treatments
Solution Approach 2:
The polyimide composition is designed to self-adjust during the curing process, where the molecular structure reorganizes to optimize both dielectric and mechanical properties without requiring additional processing steps. The material inherently provides both electrical and mechanical performance
Data Source
AI summary
A low dielectric polyimide composition comprises an aliphatic anhydride, a long chain diamine, and an ester diamine. A polyimide made of such low dielectric polyimide composition has low polarizability group, thus the dielectric constant of the polyimide is lower. A polyimide made of the low dielectric polyimide composition, a polyimide film using the polyimide, and a copper clad laminate using the polyimide film are also provided.