Metal Case Pad Corrosion Prevention via Welded Sheet
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Solution Overview
Problem
Existing electronic devices with metal cases face issues of galvanic corrosion and fretting corrosion when metal pads are directly connected to electronic circuit boards, leading to degraded antenna performance and potential device malfunctions, and existing solutions either increase machining costs, thickness, or compromise mass productivity and repairability.
Innovation Solution
A metal case structure featuring a metal pad with a metal sheet bonded by ultrasonic welding or electric resistance welding, where the metal sheet is made of corrosion-resistant materials and temporarily fixed with double-sided tape to prevent corrosion and maintain device thickness and productivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal pad of the metal case is directly connected to an electronic circuit board using a C-clip, then electrical connection is achieved, but galvanic corrosion and fretting corrosion occur leading to degraded antenna performance
Solution Approach 1:
The patent introduces a polymer insulating layer positioned between the metal pad of the metal case and the C-clip of the electronic circuit board. This intermediary polymer layer prevents direct contact between dissimilar metals, thereby eliminating galvanic corrosion while maintaining electrical connection through the conductive C-clip. The polymer also prevents fretting corrosion by reducing direct metal-to-metal friction during assembly and usage.
2Object-affected harmful factors
If a screw or bolt is used to connect the electronic circuit board to the metal case, then galvanic corrosion and fretting corrosion are prevented, but machining cost increases and minimum thickness requirements limit case thinning
Solution Approach 1:
Instead of using screws or bolts that require machining screw holes and have minimum thickness requirements, the patent uses a polymer insulating layer as an intermediary that can be applied as a thin coating. This polymer layer prevents corrosion without requiring additional machining operations, thereby reducing manufacturing cost and allowing the metal case to be made thinner.
Solution Approach 2:
The patent replaces the mechanical fastening system (screws or bolts) with a polymer insulating layer that provides both electrical insulation and corrosion protection. This substitution eliminates the need for machining screw holes and removes minimum thickness constraints associated with mechanical fasteners, enabling thinner metal case designs.
3Object-affected harmful factors
If conductive tape is attached to the metal pad, then corrosion is prevented, but reliability of adhesive is low and mass productivity decreases due to small pad size
Solution Approach 1:
The patent changes the application method and physical form of the protective layer from discrete conductive tape pieces to a continuous polymer insulating layer. This polymer layer can be applied as a coating, film, or molded structure that conforms to the metal pad surface, providing reliable adhesion through surface treatment or chemical bonding rather than relying on adhesive tapes with limited bond strength.
4Object-affected harmful factors
If conductive tape with thickness of 0.15 mm or more is provided between metal case and C-clip, then corrosion is prevented, but device thickness increases
Solution Approach 1:
The patent employs a polymer insulating layer that can be applied as a thin film or coating on the metal pad surface. This thin film approach provides corrosion protection without adding significant thickness to the device assembly, unlike discrete conductive tapes that require minimum thickness of 0.15 mm or more.
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
Prevents galvanic and fretting corrosion, maintains device thickness, and enhances mass productivity and repairability by using a corrosion-resistant metal sheet bonded to the metal pad, ensuring stable electrical connections and reduced assembly complexity.
Implementation Method 1
a metal sheet 10 bonded to a metal pad 3 of the metal case 1
Implementation Method 2
a metal sheet 10 bonded to a metal pad 3 of the metal case 1
Implementation Method 3
a metal sheet 10 bonded to a metal pad 3 of the metal case 1
Data Source
AI summary
The present invention relates to an electronic device having a metal case, the electronic device comprising: a metal case having at least one electronic circuit or antenna formed therein; a metal pad arranged at the metal case and electrically connected to the at least one electronic circuit or antenna; a metal sheet attached to one surface of the metal pad; and an electronic circuit board electrically connected to the at least one electronic circuit or antenna of the metal case through a metal instrument for connection which detachably contacts the metal sheet.