Mask Frame Assembly Thermal Expansion Control
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Solution Overview
Problem
Existing mask frame assemblies for depositing thin films in flexible display devices face thermal transformation issues, leading to undesired deposition on substrates and the inability to form fine deposition patterns due to thermal expansion, causing shadow defects.
Innovation Solution
A mask frame assembly with a specific design that includes a mask frame, patterned mask sheets, and support sticks with controlled tensile forces and transformation indices, ensuring minimal thermal expansion within a range of -1000 to +1000, thereby maintaining precise deposition patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of depositions increases, then productivity is improved, but the mask frame assembly undergoes thermal transformation causing deposition material to be deposited on undesired areas
Solution Approach 1:
The patent applies parameter changes by selecting materials with specific thermal expansion coefficients and adjusting the geometric parameters of the mask frame (width, length, thickness) to compensate for thermal transformation. The mask frame is designed with dimensions and material properties that minimize dimensional changes within the acceptable range of ±5μm even after multiple depositions, thereby maintaining deposition pattern precision while enabling increased productivity.
2Duration of action of stationary object
If the mask frame assembly is thermally transformed, then the deposition process can continue, but a fine deposition pattern cannot be formed in the substrate
Solution Approach 1:
The patent directly addresses thermal expansion by selecting materials with low thermal expansion coefficients and designing the mask frame geometry to compensate for expected thermal transformation. The mask frame dimensions and material properties are carefully chosen to ensure that thermal expansion remains within ±5μm, allowing the deposition process to continue while maintaining fine deposition pattern formation on the substrate.
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 solution effectively minimizes thermal expansion of the mask frame assembly, allowing for precise deposition patterns on substrates even after repeated use, reducing shadow defects and ensuring accurate thin film formation.
Implementation Method 1
when the number of depositions increases, a mask assembly may be thermally transformed
Implementation Method 2
tensile force of respective first or second support stick is given by thickness (T)×width (W)×elastic coefficient (E)×tensile rate (δ/L0)
Data Source
AI summary
A mask frame assembly includes: a mask frame; at least one mask sheet arranged on the mask frame; a plurality of first support sticks extending in a first direction; and a plurality of second support sticks extending in a second direction, wherein a mask frame transformation index is within a range from about −1000 to about +1000 based on mask frame transformation index=Σ (tensile force of first support sticks/tensile rate of first support sticks)−Σ (tensile force of second support sticks/tensile rate of second support sticks), where tensile force of respective first or second support stick is given by thickness (T)×width (W)×elastic coefficient (E)×tensile rate (δ/L0), δ is a transformed amount (Lf−L0) corresponding to tension, L0 is an initial length of respective first or second support stick, and Lf is a final length of respective first or second support stick.