Polyimide Precursor Dimer Diamine High Frequency PCB
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Solution Overview
Problem
Conventional polyimide films face challenges in achieving a balance between low dielectric constant and low dielectric loss tangent while maintaining sufficient strength, particularly at high frequencies, and in achieving satisfactory breaking elongation for applications requiring flexibility and insulation.
Innovation Solution
A polyimide precursor containing a dimer diamine-derived structural unit in a specific molecular ratio with a tetracarboxylic dianhydride-derived structural unit, which results in a polyimide with a weight average molecular weight of 15,000 to 130,000, offering a low dielectric constant and low dielectric loss tangent, along with high breaking elongation, suitable for high-frequency applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the blend proportion of dimer diamine is increased to improve dielectric characteristics, then the dielectric constant and dielectric loss tangent are reduced, but the polyimide becomes more soluble in solvent and the upper limit for the blend proportion is restricted
Solution Approach 1:
The patent changes the molecular weight parameter of the dimer diamine from conventional low molecular weight to high molecular weight (number average molecular weight of 1,000 to 10,000). This parameter change allows the polyimide to achieve low dielectric constant and low dielectric loss tangent while maintaining solvent insolubility, as the high molecular weight provides sufficient chain entanglement and intermolecular forces to prevent solvent dissolution even at high dimer diamine content (15-50 mol%).
Solution Approach 2:
The patent creates a composite polyimide structure by combining dimer diamine units with conventional diamine units in a controlled molar ratio. The high molecular weight dimer diamine acts as a structural component that simultaneously provides dielectric performance and mechanical stability, forming a composite material system that balances electrical properties with solvent resistance.
2Reliability
If the blend proportion of dimer diamine is increased to achieve low dielectric constant and low dielectric loss tangent, then the dielectric characteristics improve, but the strength of the resulting polyimide film is not entirely satisfactory and breaking elongation is problematic
Solution Approach 1:
The patent changes the molecular weight parameter of the dimer diamine to high molecular weight (number average molecular weight of 1,000 to 10,000), which directly impacts the mechanical properties of the polyimide film. The increased molecular weight provides longer polymer chains with more entanglement points, resulting in improved breaking elongation (50-90%) while maintaining the low dielectric properties achieved through high dimer diamine content.
Solution Approach 2:
The patent applies local quality by having different regions of the polyimide chain exhibit different properties: the high molecular weight dimer diamine segments provide mechanical strength and flexibility through extended chain structures, while the imide groups distributed throughout the structure provide the low dielectric characteristics. This local differentiation of functional properties within the same polymer structure resolves the contradiction between strength and dielectric performance.
Data Source
AI summary
Provided are a polyimide precursor which contains a diamine-derived structural unit and a tetracarboxylic dianhydride-derived structural unit, contains a dimer diamine-derived structural unit in an amount of at least 10 mol % but not more than 80 mol % relative to total units of the diamine-derived structural unit, has a weight average molecular weight of at least 15,000 but not more than 130,000, and is used for a base film of a flexible printed circuit board, as well as a resin composition containing the polyimide precursor, and a polyimide obtained using the resin composition.