Noble Metal Coating on Metallic Wire via Composite Structure
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Solution Overview
Problem
Existing methods for forming noble metal coatings on metallic substrates, such as bonding wires, face challenges with oxidation resistance and high material costs, particularly with silver and gold coatings, which are complex and costly, and result in low mechanical strength and processing speed limitations.
Innovation Solution
A method involving pre-annealing, application of a noble metal solution, baking, cooling, and thermal post-treatment in a protective atmosphere to form a durable noble metal coating, preferably a silver coating, on a metallic substrate, using a silver solution with specific composition and application techniques to enhance oxidation resistance and reduce production costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a noble metal coating (silver or gold) is applied to a metallic substrate to prevent oxidation, then oxidation resistance is improved, but material costs increase and mechanical strength decreases
Solution Approach 1:
The patent applies a multi-layer composite coating structure consisting of a nickel underlayer and a silver or gold top layer. The nickel layer provides mechanical strength and adhesion to the substrate, while the noble metal layer provides oxidation resistance. This composite structure resolves the contradiction by combining materials with complementary properties rather than using a single material that must compromise between strength and oxidation resistance.
2Reliability
If traditional galvanic coating methods are used to form noble metal coatings, then oxidation resistance is achieved, but the process becomes complex and costly
Solution Approach 1:
The patent segments the coating process into distinct sequential steps: nickel underlayer deposition, drying, thermal treatment, and noble metal layer deposition. Each step is optimized independently with specific parameter ranges (temperatures, times, compositions), allowing the complex overall process to be managed through standardized, repeatable unit operations rather than a monolithic complex process.
Solution Approach 2:
The patent employs controlled parameter changes throughout the process, including specific temperature ranges for thermal treatment (400-600°C), controlled drying conditions, and precise composition control of the noble metal solution. These parameter optimizations reduce process variability and complexity while maintaining high oxidation resistance.
3Reliability
If bonding wires are made from gold or silver to ensure electrical conductivity, then conductivity is improved, but processing speed decreases due to low mechanical strength
Solution Approach 1:
The patent creates a composite wire structure with a copper or copper alloy core providing mechanical strength and ductility, overlaid with a thin noble metal layer (silver or gold) providing electrical conductivity and oxidation resistance. This allows the wire to achieve high processing speeds enabled by the strong copper core while maintaining the electrical and corrosion properties of the noble metal surface.
Solution Approach 2:
The patent uses a thin layer of expensive noble metal (only a few micrometers thick) applied over a copper core, rather than using bulk noble metal. This minimizes the amount of expensive material needed while still providing the necessary surface properties, making the overall product more cost-effective and suitable for high-speed processing.
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 method achieves a high resistance to oxide formation, improved mechanical properties, and cost-effective production of wire products with enhanced processing speeds, outperforming traditional galvanic methods by allowing continuous operation and reduced energy consumption.
Implementation Method 1
Pre-annealing of the area of the substrate to be coated
Implementation Method 2
application of a noble metal solution to the pre-annealed area of the substrate, wherein the noble metal solution can preferably be a silver solution, baking of the noble metal solution applied to the substrate
Implementation Method 3
thermal post-treatment in a protective atmosphere to form a durable noble metal coating
Data Source
Figure 1
AI summary
A method for forming a noble metal coating, preferably a silver coating, on at least one area of a metallic substrate, in particular a metallic wire or a stranded item, comprises the following steps: - preheating the area of the substrate to be coated, - applying a noble metal solution, preferably a silver solution, to the preheated area of the substrate, - baking the noble metal solution applied to the substrate, - cooling the substrate coated with the baked noble metal solution. The substrate coated with the baked noble metal solution is then heated again after it has cooled.