Reflow Sn Plated Material Crystallographic Orientation Control
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Solution Overview
Problem
Existing Sn plated materials face challenges with whisker production, increased insertion and extraction force, and deteriorated solderability under harsh environments, particularly in high-temperature conditions, which affect the performance of connectors and similar conductive parts.
Innovation Solution
A reflow Sn plated material is developed with a Cu or Cu base alloy substrate and a reflow Sn layer, where the orientation index of the (101) plane is controlled between 2.0 and 5.0, and a Ni layer is formed between the Sn layer and the substrate to inhibit whisker production and reduce insertion and extraction force, while maintaining solderability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the Sn plated layer is made thin to decrease insertion and extraction force, then the insertion and extraction force decreases, but solderability deteriorates after heating
Solution Approach 1:
The invention changes the crystallographic orientation parameter of the Sn plated layer, specifically controlling the (101) plane orientation index to be 2.0 or less. This parameter change allows the Sn layer to maintain both low insertion/extraction force and good solderability after heating, resolving the contradiction between force reduction and solderability preservation
Solution Approach 2:
The invention applies different crystallographic orientations to different regions of the Sn plated layer. By controlling the (101) plane orientation specifically, the surface properties are optimized for low friction while maintaining the bulk properties necessary for solderability, creating local quality differentiation that resolves the contradiction
2Reliability
If the Sn plated layer is reflowed to inhibit whisker production, then whisker resistance improves, but insertion and extraction force increases
Solution Approach 1:
The invention changes the reflow processing parameters to achieve a specific crystallographic orientation outcome. By controlling the reflow conditions to produce a (101) plane orientation index of 2.0 or less, the invention simultaneously achieves whisker resistance and low insertion/extraction force, resolving the contradiction between these two properties
Solution Approach 2:
The invention creates a composite microstructure within the Sn plated layer through controlled reflow, where the crystallographic orientation is optimized to provide both whisker resistance and low friction properties. This composite approach at the microstructural level resolves the contradiction between protective and low-force properties
3Temperature
If copper substrate is exposed to high temperature, then copper diffuses to the Sn plated layer and the Sn plated layer oxidizes, but contact resistance decreases
Solution Approach 1:
The invention performs preliminary action by controlling the crystallographic orientation of the Sn plated layer before exposure to high temperature environments. By pre-establishing the (101) plane orientation, the material becomes inherently more resistant to copper diffusion and oxidation when subsequently exposed to high temperatures, preventing the deterioration of contact resistance
Solution Approach 2:
The invention changes the crystallographic parameter of the Sn plated layer to improve its thermal stability. The controlled (101) plane orientation creates a more stable microstructure that resists copper diffusion and oxidation at high temperatures, thereby maintaining contact resistance and improving heat resistance simultaneously
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 whisker production, decreases insertion and extraction force, and maintains desirable solderability and heat resistance, improving the performance of conductive parts like connectors under harsh conditions.
Implementation Method 1
an orientation index of a (101) plane on the surface of the reflow Sn layer is from 2.0 or more to 5.0 or less
Implementation Method 2
a Ni layer is formed between the Sn layer and the substrate to inhibit whisker production and reduce insertion and extraction force, while maintaining solderability
Implementation Method 3
a reflow Sn layer formed on the surface of the substrate
Data Source
AI summary
A reflow Sn plated material, comprising: a substrate consisting of Cu or a Cu base alloy, and a reflow Sn layer formed on the surface of the substrate, wherein an orientation index of a (101) plane on the surface of the reflow Sn layer is from 2.0 or more to 5.0 or less.