Foldable Magnesium Middle Frame Anti-Corrosion Layering
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Solution Overview
Problem
Foldable electronic devices using a full-magnesium alloy middle frame face galvanic corrosion issues in the rotating open region, leading to failure in salt spray environments, which conventional anti-corrosion designs fail to address, compromising the device's lightness and thinness.
Innovation Solution
A foldable structural member with a special anti-corrosion design featuring a metal body, a protective layer, an injection molding layer, and an anti-corrosion layer, which enhances sealing and bonding to prevent galvanic corrosion, allowing the use of magnesium alloy in the rotating open region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If a full-magnesium alloy middle frame is adopted to achieve lightness and thinness, then the device weight and thickness are reduced, but galvanic corrosion occurs in the rotating open region leading to failure in salt spray environments
Solution Approach 1:
The patent applies composite materials by combining magnesium alloy with protective coating layers (including anti-corrosion coating and sealing coating) to create a composite structure that maintains the lightweight advantage of magnesium alloy while adding corrosion protection. This resolves the contradiction between using lightweight magnesium alloy and achieving corrosion resistance in salt spray environments.
Solution Approach 2:
The patent introduces protective coating layers as intermediary substances between the magnesium alloy middle frame and the corrosive salt spray environment. These coating layers act as mediators that prevent direct contact between the magnesium alloy and corrosive agents, thereby protecting the lightweight structure from corrosion while maintaining its weight advantages.
2Reliability
If conventional magnesium alloy anti-corrosion design is applied, then some corrosion protection is achieved, but it fails to meet the requirement for foldable devices with rotating open regions
Solution Approach 1:
The patent applies local quality by providing enhanced protective coating specifically in the rotating open region where corrosion is most likely to occur. The sealing coating is applied to the rotating mechanism and adjacent areas to create localized protection tailored to the specific corrosion risks in foldable device regions, rather than applying uniform protection throughout.
Solution Approach 2:
The patent segments the protective system into multiple functional layers: a base anti-corrosion coating layer and an additional sealing coating layer. This segmentation allows each layer to perform specific functions - the base layer provides general corrosion protection while the sealing layer provides enhanced protection specifically at the rotating open region, making the system adaptable to the unique requirements of foldable devices.
3Reliability
If packaging the whole magnesium alloy middle frame with full adhesive is applied, then sealing is improved, but galvanic corrosion at the joint where magnesium alloy laps over steel rotating shaft cannot be solved
Solution Approach 1:
The patent introduces an anti-corrosion coating layer as an intermediary between the magnesium alloy middle frame and the steel rotating shaft. This coating acts as a mediator that prevents direct galvanic contact between the dissimilar metals while allowing the mechanical joint to function, thereby eliminating galvanic corrosion at the interface while maintaining sealing effectiveness.
Solution Approach 2:
The patent creates a composite protective system at the joint area by combining the magnesium alloy structure with protective coating layers that extend to the interface with the steel rotating shaft. This composite approach ensures that the entire joint region, including areas where magnesium alloy contacts steel, is protected from galvanic corrosion while maintaining the sealing effect.
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 design effectively reduces the risk of galvanic corrosion, ensuring the magnesium alloy middle frame's structural integrity and maintaining the device's lightness and thinness while passing salt spray tests.
Implementation Method 1
the anti-corrosion layer may significantly increase an interface bonding force between the first protective layer and the injection molding layer
Implementation Method 2
the injection molding layer in the first region and the second region may have a better sealing effect, that is, a risk of salt spray or water vapor infiltrating into the structural member is greatly reduced
Implementation Method 3
The first protective layer may protect the metal body, so as to prevent the metal body from being corroded
Data Source
AI summary
Embodiments of this application provide a foldable structural member, a manufacturing method thereof, and a foldable electronic device. The foldable structural member includes a first middle frame and a second middle frame, a first protective layer and an injection molding layer that are successively stacked in corresponding regions of the first middle frame and the second middle frame, and an anti-corrosion layer disposed between the injection molding layer and the first protective layer. The special anti-corrosion design provides feasibility for a magnesium alloy to be used as a metal body in a rotating open region of the foldable structural member, so that the structural member can be configured to provide a lighter and thinner foldable electronic device.