Polyimide Film Thermal Expansion Control

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Solution Overview

Problem

In batch type processes for electronic device manufacturing, polyimide films face issues with dimensional changes due to differing coefficients of thermal expansion between the film and the support, leading to warpage and increased haze, especially when stored for long periods or formed under varying conditions.

Innovation Solution

A polyamic acid solution with a high content of fluorine-containing diamines, such as 2,2′-bis(trifluoromethyl)benzidine, and alicyclic diamines, like trans-1,4-cyclohexanediamine, is used, which upon imidization, forms a polyimide film with low thermal expansion and low residual stress, maintaining transparency and reducing haze.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a polyimide film is formed on a support in a batch type process, then the film substrate can be utilized for electronic device manufacturing, but warpage occurs due to residual stress from differing coefficients of thermal expansion between the film and support

Engineering Contradiction:

Improvedimensional stabilityVSAvoidwarpage

Core Design Contradiction:

ReliabilityVSShape

Solution Approach 1:

The patent modifies the chemical composition parameters of the polyimide film by incorporating specific structural units (Formula 1 and Formula 2) to adjust the coefficient of thermal expansion, enabling better matching with the support substrate and reducing thermal stress-induced warpage

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite polyimide structure by combining different structural units (aromatic diamine with tetracarboxylic dianhydride units) to achieve optimized thermal expansion properties that balance compatibility with both the support and electronic elements

Inventive Principle:

Principle #40Composite materials

2Ease of manufacture

If a polyamic acid solution is stored for a long period before application, then preparation time is flexible, but the solution undergoes salt formation and depolymerization leading to increased haze in the polyimide film

Engineering Contradiction:

Improvesolution storage flexibilityVSAvoidfilm transparency

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent modifies the solution composition parameters by incorporating specific diamine and dianhydride units that enhance solution stability, preventing salt formation and depolymerization during storage while maintaining film transparency after imidization

Inventive Principle:

Principle #35Parameter changes

3Adaptability or versatility

If the coefficient of thermal expansion of the polyimide film is high, then the film is more flexible, but residual stress at the interface with the support increases causing warpage

Engineering Contradiction:

Improvefilm flexibilityVSAvoidresidual stress

Core Design Contradiction:

Adaptability or versatilityVSStress or pressure

Solution Approach 1:

The patent precisely adjusts the coefficient of thermal expansion parameter by controlling the ratio and type of structural units in the polyimide, achieving an optimal balance between film flexibility and residual stress minimization for stable lamination on supports

Inventive Principle:

Principle #35Parameter changes

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 polyimide film exhibits low thermal expansion, minimal residual stress, and high transparency, suitable for use on glass substrates, enhancing the stability and performance of electronic devices in batch type processes.

Implementation Method 1

Polyimides are generally obtained by cyclodehydration of polyamic acids

Methodology Applied

Scientific EffectCyclodehydration:

Implementation Method 2

heating the polyamic acid solution for imidization

Methodology Applied

Scientific EffectImidization:

Implementation Method 3

a laminate in which a support and a polyimide film are adhesively laminated

Methodology Applied

Scientific EffectAdhesive lamination: Adhesive

Data Source

PatentUS11274182B2Poly(amic acid), poly(amic acid) solution, polyimide, polyimide film, layered product, flexible device, and production method for polyimide film

Publication Date: 2022.03.15 KANEKA CORP

AI summary

A polyamic acid that has a fluorine atom content of 25 wt % or less and an amount of a fluorine-containing diamine in the polyamic acid is 70 mol % or more with respect to 100 mol % of a sum of diamine components. The total number of moles of tetracarboxylic acid component in the polyamic acid is 0.960 times or more and less than 1.000 time total number of moles of diamine component. The polyamic acid preferably has the structural unit represented by formula (1) and the structural unit represented by formula (2). The polyamic acid may contain trans-1,4-cyclohexanediamine as the diamine component.