Circuit Board Corrosion Protection via Sealed Plating Film
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Solution Overview
Problem
Copper conductive circuit layers on circuit boards corrode when exposed to damp H2S gas and a galvanic cell effect occurs between gold and nickel layers, leading to nickel and copper corrosion and gold layer detachment.
Innovation Solution
A method involving a copper clad laminate with a polyimide substrate, etched or laser-cut copper layers, and a plating process forming nickel and gold layers, followed by a dry film pattern and adhesive application to create a sealed circuit board with a covering film that prevents exposure and corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the copper conductive circuit layer and nickel layer are exposed on the fractured surface, then the circuit board structure is simple and manufacturing is easy, but the copper and nickel layers corrode when exposed to damp H2S gas atmosphere
Solution Approach 1:
The patent applies composite materials by creating a multi-layer plating structure consisting of copper conductive circuit layer, nickel layer, and gold layer. This composite structure provides both manufacturing feasibility and corrosion resistance, as each layer serves a specific function: copper for conductivity, nickel for barrier protection, and gold for surface protection against H2S corrosion.
Solution Approach 2:
The gold layer acts as an inert protective barrier that prevents the underlying copper and nickel layers from contacting the corrosive H2S gas atmosphere. This creates a protected environment for the sensitive metal layers, eliminating the need for complex sealing while maintaining corrosion resistance.
2Device complexity
If the nickel layer and copper layer are used without additional protection, then the device complexity is low, but the galvanic cell effect causes corrosion and gold layer detachment
Solution Approach 1:
The gold layer serves as an inert protective atmosphere for the underlying nickel and copper layers, preventing galvanic cell formation by blocking contact between dissimilar metals and the corrosive environment. This simple three-layer structure effectively eliminates galvanic corrosion without adding complex protective mechanisms.
3Manufacturing precision
If the plating film surface is left fractured and exposed, then manufacturing precision requirements are reduced, but the exposed surface allows corrosion and layer detachment
Solution Approach 1:
The multi-layer composite plating film (copper-nickel-gold) provides inherent corrosion protection that works effectively even with fractured surfaces. The hierarchical structure ensures that the corrosive environment contacts only the gold layer, which is highly resistant to H2S, while the underlying layers remain protected regardless of surface topology.
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 solution effectively seals the copper and nickel layers, preventing corrosion and ensuring the gold layer remains intact, enhancing the durability and reliability of the circuit board in humid environments.
Implementation Method 1
Cu+O2→Cu2+O, Cu2+O+O2→CuO
Implementation Method 2
Cu2+O+H2S→Cu2S↓+H2O, CuO+H2S→CuS↓+H2O
Implementation Method 3
Galvanic cell effect can occur at the interface of gold and nickel, and an interface of nickel and copper, to cause the nickel layer and the copper conductive circuit layer to corrode
Data Source
AI summary
A circuit board film-plated against corrosion of conductive traces comprises a substrate, a conductive circuit layer attached to the substrate, a plating film attached to outer surface of the conductive circuit layer, and a covering film. Each plating film comprises a top outer surface and a side surface. The circuit board defines at least one through hole. Each through hole passes through substrate, conductive circuit layer, and the plating film. The covering film covers the conductive circuit layer, the side surfaces, and the through holes. The conductive circuit layer and the side surfaces of the plating films are sealed against the atmosphere and cannot be corroded. A method for making the circuit board is also provided.