Layered Plating Stack for Low Contact Resistance in Corrosive Gases
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Solution Overview
Problem
Strike layers in plated materials do not effectively enhance contact resistance in corrosive environments, particularly when exposed to gases like H2S, Cl2, and NO2, and their influence on corrosion performance is not evident.
Innovation Solution
Incorporating a strike layer made of noble metals, such as palladium, between underlying and intermediate plating layers to improve contact resistance and withstand corrosion testing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional silver strike layer is used, then adhesion between plating layers is improved, but contact resistance increases significantly after exposure to corrosive environments
Solution Approach 1:
A thin strike layer of noble metal (such as palladium, rhodium, or ruthenium) is introduced as an intermediary between the corrosive environment and the underlying silver strike layer. This noble metal strike layer serves as a mediator that provides both adhesion to the silver layer and resistance to corrosion, preventing the silver from reacting with corrosive gases while maintaining electrical contact resistance below 25 mohms after exposure to environments containing H2S, Cl2, NO2, and SO2.
2Reliability
If a noble metal strike layer is used instead of silver, then contact resistance is maintained in corrosive environments, but manufacturing cost increases
Solution Approach 1:
The noble metal is applied only as a thin strike layer (typically 0.01-0.5 micrometers) specifically at the contact interface where corrosion resistance is critical, rather than throughout the entire plating structure. This localized application provides the necessary corrosion protection and maintains contact resistance while minimizing the amount of expensive noble metal used, making the manufacturing process more cost-effective compared to using noble metal throughout the entire plating stack.
3Strength
If the strike layer is made thinner, then adhesion quality improves, but corrosion protection capability decreases
Solution Approach 1:
The plating structure employs a composite layered architecture consisting of multiple functional layers: a thin noble metal strike layer (0.01-0.5 μm) providing corrosion resistance and adhesion, followed by a thicker silver strike layer or intermediate layer providing electrical conductivity and bulk material properties. This composite structure allows each layer to perform its specialized function optimally - the thin noble metal layer maintains strong adhesion while providing sufficient corrosion barrier, and the thicker underlying layers provide structural support and conductivity.
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 layered plating stack with a palladium strike layer maintains low contact resistance levels even after exposure to corrosive environments, outperforming silver strike layers in maintaining contact resistance under load and wiping conditions.
Implementation Method 1
exposure to a gaseous environment which includes one or more of H2S, Cl2, NO2 and SO2
Implementation Method 2
The noble metal of the strike layer is a different metal than the metal of the intermediate plating layer
Data Source
AI summary
A layered plating stack which includes an underlying plating layer formed on a substrate; an intermediate plating layer; an outer plating layer; and at least one strike layer of noble metal. The noble metal of the strike layer is a different metal than the metal of the intermediate plating layer. The layered plating stack with the strike layer maintains contact resistance of below 25 mohms when tested under a load of at least approximately 30 grams after 1 or more days of exposure to a gaseous environment which includes Cl2, NO2 and SO2. The layered plating stack with the strike layer also maintains a contact resistance of below 25 mohms when tested under a load of at least approximately 30 grams with a wipe of at least approximately 0.1 mm after exposure to a gaseous environment which includes one or more of H2S, Cl2, NO2 and SO2.