Palladium Coating Crystal Orientation for Corrosion Resistance
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Solution Overview
Problem
Copper and copper alloys used in signal transfer units are prone to corrosion, leading to defects in gold plating films and reduced corrosion resistance, which compromises the reliability of electrical connections with external apparatuses, increasing manufacturing costs due to the need for thicker gold plating.
Innovation Solution
A coating with a palladium layer having a crystal plane orientation rate of 65% or more, optionally containing phosphorus, and a gold layer or metal underlayer is applied to the conductor, providing superior corrosion resistance and connection reliability while reducing manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a multi-layered nickel plating and gold plating film structure is used for anti-rust and anti-corrosion purposes, then corrosion resistance is improved, but manufacturing cost increases due to the need for thicker gold plating
Solution Approach 1:
The invention changes the crystallographic parameters of the nickel plating layer by controlling its crystal orientation (making the (111) plane the dominant orientation). This parameter change in the nickel layer's crystal structure fundamentally alters its chemical stability, providing corrosion resistance without requiring thick gold plating, thus reducing manufacturing cost while maintaining reliability
Solution Approach 2:
The invention replaces the expensive gold plating with a controlled-thickness nickel plating layer that has enhanced corrosion resistance through crystal orientation control. The nickel layer, being cheaper and sufficiently protective when properly oriented, substitutes for the expensive gold layer, reducing material cost while maintaining the required protective function
2Ease of manufacture
If a thinner or no gold plating film is used, then manufacturing cost is reduced, but corrosion resistance deteriorates and contact resistance increases
Solution Approach 1:
The invention changes the protective parameters of the nickel layer by controlling its crystal orientation to make the (111) plane dominant. This parameter change enhances the nickel layer's inherent corrosion resistance, allowing it to provide adequate protection even at reduced thicknesses, thereby enabling cost reduction without sacrificing reliability
Solution Approach 2:
The nickel plating layer, through its controlled crystal orientation, provides its own corrosion protection without requiring the additional protective function of a thick gold layer. The oriented nickel structure itself becomes sufficiently resistant to corrosion, making the expensive gold plating unnecessary for achieving the required protection level
3Ease of manufacture
If electroless displacement gold plating is used on a nickel plating film, then gold plating can be formed, but the nickel plating film is easily corroded leading to defects in the gold plating films
Solution Approach 1:
The invention performs preliminary action by controlling the crystal orientation of the nickel plating layer before applying the gold plating. By pre-establishing the corrosion-resistant (111) oriented nickel structure, the substrate is prepared in advance to resist corrosion during and after gold plating formation, preventing the development of defects in the gold layer that would otherwise occur with conventionally oriented nickel
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 palladium layer with high crystal plane orientation and optional phosphorus and gold or metal underlayer enhances corrosion resistance, abrasion resistance, and connection reliability, maintaining low contact resistance and manufacturing costs.
Implementation Method 1
a palladium layer having a crystal plane whose orientation rate is 65% or more
Implementation Method 2
the palladium layer in the coating contains phosphorus in a concentration ranging from 0.5% by mass to 2.5% by mass. This can allow the coating to have enhanced abrasion resistance by making the crystal of the palladium layer finer and denser
Implementation Method 3
an electroless nickel film as an underlayer is formed on the base material of a connection terminal and an electroless displacement gold plating film and an electroless reductional gold plating film are formed in this order on the underlayer
Implementation Method 4
The coating layers in Patent Document 1 are made using electrons produced in the corrosion reaction of a nickel plating film, the electrons reducing gold ions in the plating solution through electroless displacement gold plating
Implementation Method 5
electrons produced in the corrosion reaction of a nickel plating film
Data Source
AI summary
A coating for a conductor, the coating having a layered structure of a palladium layer. The palladium layer has a crystal plane whose orientation rate is 65% or more, which means 65% or more of the crystal planes of the palladium layer are aligned to this crystal plane. Preferably the crystal plane whose orientation rate is 65% or more in the coating is the (111) plane or (200) plane.