Flexible Substrate Carrier Retaining Features for TFT Fabrication

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Conventional methods for fabricating thin-film transistor (TFT) devices on flexible substrates face challenges due to the incompatibility of metal foils with glass carriers over a broad temperature range, leading to excessive stress and dimensional instability, and require handling constraints that limit substrate thickness and processing flexibility.

Innovation Solution

A method involving conditioning a carrier with retaining features to securely support flexible substrates, allowing for deposition and processing of electronic devices, and releasing the processed substrate without matching Coefficient of Thermal Expansion (CTE) values, enabling the use of various metal or plastic substrates, including thin metal foils, over a wide temperature range.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If metal foils are used as flexible substrates with glass carriers, then substrate flexibility is improved, but dimensional stability deteriorates due to CTE mismatch causing excessive stress

Engineering Contradiction:

Improvesubstrate flexibilityVSAvoiddimensional stability

Core Design Contradiction:

Adaptability or versatilityVSStability of the object's composition

Solution Approach 1:

A release layer is introduced as an intermediary between the metal foil substrate and the glass carrier. This release layer has a coefficient of thermal expansion that matches the metal foil, serving as a mediator that prevents direct CTE mismatch stress between the metal substrate and glass carrier. The release layer absorbs thermal expansion differences, allowing the metal foil to be processed at high temperatures while maintaining dimensional stability, and enables easy release of the substrate after fabrication.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If conventional mounting methods (adhesives, tape, clamping) are used, then substrate support is achieved, but handling complexity increases and minimum substrate thickness is constrained

Engineering Contradiction:

Improvesubstrate supportVSAvoidhandling complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces mechanical mounting systems (adhesives, tape, clamping schemes) with a thermal-field-based release mechanism. The release layer is designed with specific thermal properties that allow it to adhere to the glass carrier at room temperature but release when heated during fabrication processing. This substitution eliminates the need for complex mechanical handling and mounting systems, reducing handling complexity while maintaining reliable substrate support throughout the fabrication process.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Manufacturing precision

If flexible substrates are mounted on carriers during fabrication, then flatness and support are improved, but processing flexibility deteriorates due to handling constraints

Engineering Contradiction:

ImproveflatnessVSAvoidprocessing flexibility

Core Design Contradiction:

Manufacturing precisionVSAdaptability or versatility

Solution Approach 1:

The patent employs periodic thermal action to control the substrate-carrier interaction. The release layer adheres to the glass carrier at room temperature during flatness-critical fabrication steps, providing the needed support and flatness. When heating is applied during processing, the release layer thermally expands and releases the substrate, allowing for processing flexibility. This periodic adherence and release cycle, controlled by temperature variations, enables both high manufacturing precision during fabrication and processing flexibility during subsequent steps.

Inventive Principle:

Principle #19Periodic action

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

This approach allows for the successful fabrication of electronic devices on flexible substrates with improved dimensional stability and adaptability to different substrate materials, overcoming the limitations of CTE mismatch and handling constraints in conventional methods.

Implementation Method 1

conditioning a carrier with retaining features to securely support flexible substrates

Methodology Applied

Scientific EffectSurface conditioning:

Implementation Method 2

deposition and processing of electronic devices

Methodology Applied

Scientific EffectDeposition: Deposition (physical)

Implementation Method 3

The fabrication process for the TFT may require temperatures in the range of 125-300 degrees C. or higher. One particular problem with metal substrates relates to expansion and contraction of materials under temperature extremes

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 4

releasing the processed substrate from the carrier

Methodology Applied

Scientific EffectRelease:

Data Source

PatentUS9060419B2Substrate formed on carrier having retaining features and resultant electronic device

Publication Date: 2015.06.16 CARESTREAM HEALTH INC

AI summary

A method for forming an electronic device on a flexible substrate conditions at least one surface of a carrier to form at least one retaining feature on the surface for retaining a flexible substrate. The flexible substrate is provided by deposition or lamination f one or more layers of substrate material onto the carrier. A portion of the substrate is processed to form the electronic device on the processed portion of the substrate. At least the processed portion of the substrate is released from the carrier to provide the flexible substrate having electronic device formed thereon. An electronic device is formed on a flexible substrate in accordance with the method.