Vapor Deposition Mask Stress Relief via Segmented Alignment Marks
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Solution Overview
Problem
Vapor deposition masks manufactured using electroforming face challenges with stress concentration near alignment marks, leading to warping and difficulties in accurate alignment during the vapor deposition process, particularly when the metal film is thin and the diameter of the alignment mark is large.
Innovation Solution
The vapor deposition mask incorporates a metal film with a first opening part serving as an alignment mark, surrounded by a plurality of second and third opening parts with smaller diameters, arranged in an annular fashion to relieve stress and prevent warping, allowing for accurate alignment using an autofocus mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the diameter of the alignment mark (first opening part) is increased to improve alignment visibility, then alignment detection is improved, but stress concentration increases leading to warping
Solution Approach 1:
The alignment mark structure is segmented into a large first opening part for detection and multiple smaller second opening parts arranged annularly around it. This segmentation allows the large central opening to provide good alignment visibility while the surrounding smaller openings distribute and relieve stress, preventing warping of the mask.
2Length of moving object
If the metal film thickness is reduced to achieve thinner mask structure, then device miniaturization is improved, but stress concentration becomes more severe causing warping
Solution Approach 1:
By segmenting the opening structure into a large first opening and multiple smaller second openings arranged annularly, the stress distribution in the thin metal film is improved. The smaller surrounding openings act as stress relief points that prevent concentration of stress in the thin film, thereby reducing warping even when the overall mask structure is miniaturized.
Solution Approach 2:
The local structure around the first opening part is modified by adding second opening parts with different characteristics (smaller diameter, annular arrangement). This creates local quality variations that specifically address stress concentration in critical areas while maintaining the overall thin film structure for miniaturization.
3Manufacturing precision
If electroforming is used to manufacture the vapor deposition mask for high dimensional accuracy, then manufacturing precision is improved, but stress concentration near large diameter alignment marks causes warping
Solution Approach 1:
The electroformed mask structure is segmented to include a large first opening part for alignment and multiple smaller second opening parts arranged annularly. This segmentation resolves the stress concentration issue inherent in large single openings while maintaining the high dimensional accuracy achievable through electroforming, as the segmented structure allows precise control of each opening's geometry.
Solution Approach 2:
The local structure is optimized by creating different opening sizes and arrangements in different regions. The first opening part provides the necessary alignment features while the surrounding second opening parts provide local stress relief, allowing the electroformed mask to maintain both high manufacturing precision and structural stability.
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 arrangement of second and third opening parts effectively relieves stress around the alignment mark, preventing warpage and enabling precise alignment, even for larger diameter alignment marks, thus ensuring accurate vapor deposition on organic EL display devices.
Implementation Method 1
a plurality of second opening parts and a plurality of third opening parts are arranged in an annular fashion along an outline of the first opening part so as to relieve stress
Data Source
AI summary
A vapor deposition mask includes a frame and a metal film supported by the frame, wherein the metal film includes a mask region arranged with a plurality of pixel opening parts corresponding to a display region of a display device, and an alignment region arranged in a periphery of the mask region, the alignment region includes a first opening part and a plurality of second opening parts arranged in a periphery of the first opening part, and a maximum width of the second opening part is smaller than a maximum width of the first opening part.