Electroless Gold Plating via Nickel Underlayer for Pinhole Prevention
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Solution Overview
Problem
Electroless substitution gold plating on metallic base materials often results in micro recesses, leading to pinholes in the gold plate layer, which compromises corrosion resistance and conductivity, and the use of cyanide-based gold plating baths poses environmental hazards.
Innovation Solution
Forming an underlying alloy layer of Ni-Pd-P, Ni-Pt-P, or Co-Pd-P on the base material using electroless plating, followed by electroless reduction gold plating with a cyanide-free bath to achieve a gold plate layer with improved adhesion and reduced environmental impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If electroless substitution gold plating is performed on metallic base material, then gold plate layer is formed, but micro recesses occur at the surface leading to pinholes in the gold layer
Solution Approach 1:
The patent applies preliminary action by performing electroless nickel plating before electroless gold plating. The nickel layer is formed in advance to prevent micro recesses and pinholes during subsequent gold plating, ensuring surface quality and reliability of the final gold coating.
Solution Approach 2:
The patent uses an intermediary approach by introducing a nickel underlayer between the base material and the gold plate layer. This intermediate layer acts as a mediator that prevents direct dissolution of the base material and ensures uniform gold deposition, eliminating pinholes while maintaining corrosion resistance and conductivity.
2Manufacturing precision
If cyanide-based gold plating bath is used to form gold plate layer, then good plating quality is achieved, but high toxicity waste liquid is generated posing environmental hazards
Solution Approach 1:
The patent applies parameter changes by substituting the cyanide-based plating bath with a non-cyanide-based plating bath. This chemical parameter change eliminates toxic waste generation while maintaining effective gold plating quality, resolving the contradiction between plating quality and environmental protection.
Solution Approach 2:
The patent converts the harmful cyanide-based process into a beneficial non-cyanide process. By eliminating cyanide from the plating bath, the method transforms an environmentally harmful process into an eco-friendly one, achieving both good plating quality and reduced environmental impact.
3Object-affected harmful factors
If electroless reduction gold plating is performed directly on base material using cyanide-free bath, then environmental load is reduced, but gold plate layer has low coverage and poor interfacial adhesion
Solution Approach 1:
The patent applies preliminary action by forming an electroless nickel underlayer before performing electroless reduction gold plating. This preliminary nickel layer provides a suitable surface that enhances gold coverage and interfacial adhesion, solving the deficiency of direct cyanide-free gold plating while maintaining environmental benefits.
Solution Approach 2:
The patent uses an intermediary nickel layer between the base material and the gold plate. This intermediate nickel layer mediates the bonding between the base material and gold, ensuring excellent coverage and adhesion properties while allowing the use of environmentally friendly non-cyanide plating baths.
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 effectively prevents pinholes and enhances interfacial adhesion and corrosion resistance of the gold plate layer while reducing environmental loads by using a cyanide-free plating process, allowing for efficient formation of a gold plate film suitable for electrical contact materials and fuel cell separators.
Implementation Method 1
forming an underlying alloy layer constituted of a Ni-Pd-P alloy, a Ni-Pt-P alloy or a Co-Pd-P alloy on a base material
Implementation Method 2
forming a gold plate layer on the underlying alloy layer by means of electroless reduction plating
Data Source
Figure 1(A)~1(E)
Figure 2
AI summary
There is provided a method of electroless gold plating, wherein the method includes a step of forming an underlying alloy layer on a base material and a step of forming a gold plate layer directly on the underlying alloy layer by means of electroless reduction plating using a cyanide-free gold plating bath, wherein the method is characterized in that the underlying alloy layer is formed of an M1-M2-M3 alloy (where M1 is at least one element selected from Ni, Fe, Co, Cu, Zn and Sn, M2 is at least one element selected from Pd, Re, Pt, Rh, Ag and Ru, and M3 is at least one element selected from P and B).