Multi-layer Ceramic Enclosure for Handheld Devices
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Solution Overview
Problem
Existing enclosures for portable computing devices lack a combination of aesthetic appeal, functionality, durability, and radio transparency, while also being vulnerable to mishaps and environmental factors.
Innovation Solution
A multi-layer ceramic enclosure is developed using ceramic laminates with differing coefficients of thermal expansion, where outer layers have compressive residual stress and inner layers have tensile residual stress, formed through processes like warm pressing and sintering, utilizing materials like alumina and zirconia for enhanced strength and RF transparency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a single-layer ceramic enclosure is used, then the manufacturing process is simple, but the enclosure lacks durability and resistance to external stresses
Solution Approach 1:
The patent applies composite materials by creating a multi-layer ceramic enclosure where each layer has different properties. The first outer layer provides scratch resistance, the second outer layer provides impact resistance, and the inner layer provides structural support. This composite structure resolves the contradiction by combining multiple materials with different strengths to achieve overall enhanced durability while maintaining a unified enclosure design.
Solution Approach 2:
The patent segments the enclosure into multiple functional layers, each optimized for specific protective functions. The first outer layer is optimized for scratch resistance, the second outer layer for impact resistance, and the inner layer for structural integrity. This segmentation allows each layer to specialize in resisting different types of external stresses, thereby achieving superior overall strength without requiring a single overly complex material.
2Reliability
If outer layers have higher CTE than inner layer, then thermal expansion is reduced, but residual stress distribution becomes unfavorable for durability
Solution Approach 1:
The patent applies parameter changes by carefully selecting and controlling the coefficient of thermal expansion (CTE) values for each layer. The outer layers are designed with lower CTE than the inner layer, which creates a specific residual stress distribution during cooling after firing. This parameter optimization ensures that compressive stresses are positioned on the outer surfaces where they provide beneficial protection against external stresses, thereby enhancing reliability while managing stress distribution.
Solution Approach 2:
The patent utilizes thermal expansion differences between layers to create desirable residual stress patterns. By designing outer layers with lower CTE than the inner layer, the structure develops compressive residual stresses on the outer surfaces during the cooling process. This thermal expansion principle directly addresses the contradiction by using controlled CTE mismatches to achieve favorable stress distribution that enhances enclosure reliability.
3Reliability
If conventional materials are used for the enclosure, then manufacturing is easier, but the enclosure lacks radio transparency for wireless communications
Solution Approach 1:
The patent applies composite materials by selecting specific ceramic compositions for each layer that provide both structural integrity and radio transparency. The use of ceramic materials with appropriate dielectric properties allows wireless signals to pass through while maintaining enclosure strength. This composite approach resolves the contradiction by combining materials that simultaneously satisfy both manufacturing requirements and radio transparency needs.
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 multi-layer ceramic enclosure provides a strong, aesthetically pleasing, and radio-transparent housing that is resistant to external stresses and environmental factors, enhancing the durability and functionality of portable electronic devices while maintaining seamless and water-resistant properties.
Implementation Method 1
The first and second outer layers have a CTE that is less than the inner layer, and wherein the first and second layers have a compressive residual stress profile and the inner layer has a tensile residual stress profile
Implementation Method 2
processed through processes like warm pressing and sintering
Data Source
AI summary
Techniques for fabricating a laminated ceramic housing that can be used for a handheld computing device that includes an enclosure having structural walls formed from a multi-layered ceramic material that can be radio-transparent. The multi-layered ceramic housing can be formed of a plurality of ceramic materials such as zirconia and alumina in any combination. The multi-layer ceramic substrate includes an inner layer and surface layers that sandwich the inner layer. The multi-layer ceramic substrate has an increased transverse strength due to the surface layers having a coefficient of thermal expansion (CTE) that is less than that of the inner layer.