Angled Heat Shield for Sapphire Sheet Dimensional Stability
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Solution Overview
Problem
Existing methods for producing sapphire sheets face challenges in achieving consistent dimensional stability, particularly in large and thick sheets, which affects their performance in applications such as ballistic and targeting windows.
Innovation Solution
The use of an edge-defined film growth (EFG) apparatus with a heat reflective shield angled with respect to the horizontal plane to control thermal gradients, allowing for precise temperature management and improved crystal growth, resulting in sapphire sheets with reduced Total Thickness Variation (TTV), maximum low spot thickness, and standard deviation from planar.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional methods are used to produce large and thick sapphire sheets, then the sheets can be manufactured, but dimensional stability deteriorates with increased size and thickness
Solution Approach 1:
The patent applies local quality by implementing a multi-zone temperature control system with distinct thermal gradients across different regions of the sapphire sheet during growth. The EFG process creates controlled variations in temperature distribution, with the die region maintaining higher temperatures for crystal growth while cooler regions provide dimensional stability, allowing large and thick sheets to be produced with consistent dimensions.
Solution Approach 2:
The patent utilizes parameter changes by systematically varying temperature parameters and thermal gradient conditions during the sapphire growth process. By adjusting the temperature differential between the die and surrounding regions, and controlling the cooling rates in different zones, the process achieves both large sheet production and dimensional stability through optimized thermal parameters.
2Stability of the object's composition
If EFG process is used with angled heat reflective shield, then dimensional stability improves, but device complexity increases
Solution Approach 1:
The patent employs an angled heat reflective shield as an intermediary element between the heat source and the sapphire crystal growth region. This shield mediates the thermal energy distribution by reflecting and redirecting heat rays at specific angles, creating the necessary thermal gradients for dimensional stability without requiring direct complex control mechanisms, thus achieving stability while managing apparatus complexity.
3Manufacturing precision
If thermal gradients are controlled precisely, then Total Thickness Variation reduces, but energy consumption increases
Solution Approach 1:
The patent implements self-service by designing a passive thermal management system where the angled heat reflective shield automatically directs thermal energy to create appropriate gradients without requiring active control mechanisms. The system uses the natural behavior of heat radiation and reflection to maintain thermal gradients, reducing energy consumption while achieving precise thickness control through geometric configuration rather than continuous energy input.
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 enhances the dimensional stability of sapphire sheets, reducing TTV and maximum low spot thickness, and increasing the usable surface area of the sheets, while minimizing scrap material, thereby improving their performance and reliability for demanding applications.
Implementation Method 1
The heat reflective shield can be configured to reflect a significant amount of thermal radiation
Implementation Method 2
crystallizing a sapphire sheet above a die
Implementation Method 3
cooling the sapphire sheet in a first region adjacent the die
Data Source
AI summary
The present disclosure is directed to an apparatus and method for growing a sapphire sheet via edge-defined film-fed growth (EFG) including an angled heat shield with respect to the a side surface of a die tip. The present disclosure is further directed to an sapphire sheets and batches of such sheets having features such as a particular maximum low spot thickness.