Anti-tarnish Coating for Copper Substrates via Immersion Plating
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Copper substrates in electronic devices face challenges with corrosion protection, particularly at interfaces between copper and precious metal coatings, due to porosity issues and susceptibility to sulfidation, leading to reduced durability and effectiveness in corrosive environments.
Innovation Solution
A method and composition involving immersion displacement plating with a combination of thiol or disulfide organic molecules and aromatic heterocycles to form a self-assembled hydrophobic film on copper or copper alloy substrates, enhancing corrosion resistance and solderability by interacting with both precious metal and copper surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a thin precious metal layer is used to reduce cost, then cost is reduced, but porosity increases and corrosion protection deteriorates
Solution Approach 1:
The patent applies composite materials by combining precious metal layers with organic protective coatings. The precious metal layer (silver or gold) provides electrical conductivity and basic corrosion resistance, while the organic coating layer containing nitrogen-containing compounds provides additional protection against corrosion and sulfidation. This composite structure allows thin precious metal layers to maintain adequate protection without requiring thick layers, thus reducing cost while preserving reliability.
Solution Approach 2:
The organic coating acts as an intermediary layer between the precious metal layer and the corrosive environment. This intermediate layer specifically targets and protects against sulfidation and corrosion at the copper-precious metal interface, enabling the use of thinner precious metal layers without compromising the protective function.
2Ease of manufacture
If immersion displacement plating is used to deposit precious metal, then deposition cost is reduced, but creep corrosion occurs at copper interfaces
Solution Approach 1:
The organic coating containing nitrogen-containing compounds serves as an intermediary protective layer at the copper-precious metal interface. This layer specifically addresses creep corrosion by forming a protective barrier that prevents copper salt migration and sulfidation at the interface, while being compatible with the immersion displacement plating process used to deposit the precious metal layer.
Solution Approach 2:
The organic coating is applied before the precious metal layer is fully exposed to corrosive environments. This preliminary protective action prevents creep corrosion and sulfidation from occurring in the first place, rather than merely treating symptoms after they appear. The coating is applied to the copper substrate before or during the precious metal deposition process, establishing protection in advance.
3Reliability
If silver coating is applied to protect copper, then corrosion protection is provided, but sulfidation susceptibility increases
Solution Approach 1:
The patent creates a composite protective system where silver coating is combined with nitrogen-containing organic compounds. The silver provides basic corrosion protection and electrical conductivity, while the nitrogen-containing organic compounds specifically address sulfidation susceptibility by forming protective layers that prevent sulfur attack. This composite approach allows silver coating to maintain its protective function while mitigating its vulnerability to sulfidation.
Solution Approach 2:
The nitrogen-containing organic coating acts as an intermediary layer between the silver coating and sulfur-containing environmental factors. This intermediate layer specifically blocks sulfidation pathways while allowing the silver coating to maintain its electrical and protective properties, thus addressing the specific vulnerability of silver to sulfidation without compromising its overall protective function.
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 inhibits copper creep corrosion, maintains solderability, and provides long-term stability against environmental pollutants, enhancing the durability of copper substrates in electronic devices.
Implementation Method 1
a first organic molecule in a concentration between 1 and 10 g/L selected from the group consisting of a thiol, a disulfide, and a combination thereof that interacts with and protects precious metal surfaces
Implementation Method 2
exposing the copper or copper alloy substrate comprising the precious metal surface layer to an aqueous composition... wherein said composition leaves a self-assembled hydrophobic film on the surface
Implementation Method 3
a second organic molecule in a concentration between 1 and 10 g/L comprising an aromatic heterocycle comprising nitrogen, and combinations thereof that interacts with and protects copper surfaces
Implementation Method 4
wherein said composition leaves a self-assembled hydrophobic film on the surface
Implementation Method 5
silver ions present in the plating composition come into contact with and are reduced by surface copper atoms
Implementation Method 6
immersion displacement plating, in which silver ions present in the plating composition come into contact with and are reduced by surface copper atoms
Data Source
Figure 1
Figure 2A~2B
Figure 2C~2D
AI summary
A method is disclosed for enhancing the corrosion resistance of a surface of a copper or copper alloy substrate. The method comprises depositing a metallic surface layer comprising a precious metal on a surface of the copper or copper alloy substrate by immersion displacement plating and exposing the electronic device to an aqueous composition comprising a first organic molecule comprising at least one functional group that interacts with and protects precious metal surfaces and a second organic molecule comprising at least one functional group that interacts with and protects copper surfaces.