Plasma-Resistant Mask Coating for OLED Encapsulation
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Solution Overview
Problem
The manufacture of OLED display devices faces challenges such as mask cracking, bending, or breakage due to temperature extremes and material reactions with plasmas, leading to contamination of substrates during encapsulation processes.
Innovation Solution
A mask assembly made of metallic materials with a low coefficient of thermal expansion, such as nickel-iron alloys, and a metal coating on exposed surfaces to prevent thermal movement and react with plasma gases, reducing particle generation and extending the mask's lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If masks are used to shield portions of the substrate during encapsulation processes, then the OLED material is protected from moisture, but the masks are subject to temperature extremes causing thermal expansion and contraction that leads to cracks, bending or breakage
Solution Approach 1:
The patent applies parameter changes by selecting materials with specific thermal properties. The mask frame uses Invar alloy (36% nickel, 64% iron) which has a near-zero coefficient of thermal expansion, while the mask screen uses molybdenum which also has low thermal expansion. This material parameter selection resolves the contradiction by making the mask dimensions stable despite temperature extremes during the encapsulation process.
2Reliability
If masks are used to shield portions of the substrate during encapsulation processes, then the OLED material is protected from moisture, but plasma reactions with the mask material create particles that cause contamination of the substrate
Solution Approach 1:
The patent applies the intermediary principle by introducing a protective coating layer between the plasma environment and the mask material. The mask frame is coated with nickel and the mask screen is coated with silicon nitride or silicon oxide. These coating layers act as intermediaries that are resistant to plasma reactions, preventing particle generation from the mask material while allowing the mask to perform its shielding function.
3Ease of manufacture
If standard metallic masks are used in deposition processes, then the masks can be manufactured with simple structures, but they crack, bend or break due to thermal expansion and contraction from temperature extremes
Solution Approach 1:
The patent applies composite materials by combining different materials with complementary properties. The mask assembly consists of an Invar alloy frame (for dimensional stability), a molybdenum screen (for low thermal expansion and plasma resistance), and protective coatings (nickel on frame, silicon nitride or oxide on screen). This composite structure maintains manufacturing feasibility while dramatically improving structural integrity under thermal stress.
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 provides a stable mask assembly that maintains accuracy and reduces particle contamination, effectively doubling or tripling the mask's lifetime, thereby increasing yield and reducing costs.
Implementation Method 1
The temperature extremes cause thermal expansion and contraction of the mask, which may lead to cracks, bending or breakage of the mask
Implementation Method 2
some of these processes utilize plasmas that may react with the material of the mask in a manner that creates particles
Data Source
AI summary
A mask assembly (100) includes a mask frame (102) and a mask screen (104), both of the mask frame (102) and the mask screen (104) made of a metallic material, and a metal coating (125) disposed on exposed surfaces of one or both of the mask frame (102) and the mask screen (104).