Sn/Ag Plating Structure for Whisker Suppression
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Solution Overview
Problem
Conventional metal materials for electronic components with Sn/Ag/Ni base plating face issues with insertability/extractability, whisker formation, and durability, particularly in terms of heat resistance and gas corrosion resistance, while existing solutions do not adequately address these challenges.
Innovation Solution
A metal material structure comprising a base material with a middle layer of Ag, Au, Pt, Pd, Ru, Rh, or Ir, and an outermost surface layer of Sn or In, optimized in thickness and composition to reduce whisker formation and improve durability, along with a specific underlayer to enhance lubrication and prevent diffusion of base material components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Sn or Sn alloy plating is applied to achieve low contact resistance and high solder wettability, then solderability is improved, but tin whiskers are generated causing short-circuits
Solution Approach 1:
An Ag or Ag alloy intermediate layer is introduced between the base material and the Sn/Sn alloy outer layer. This intermediate layer acts as a mediator that prevents direct contact between the Sn layer and base material, thereby suppressing tin whisker generation while maintaining the solderability provided by the Sn outer layer.
Solution Approach 2:
A composite plating structure consisting of multiple layers (base material + Ag intermediate layer + Sn/Sn alloy outer layer) is created. This composite structure combines the advantages of each material: the Sn layer provides solderability, the Ag layer suppresses whiskers, and together they form a durable multi-functional coating system.
2Reliability
If conventional Sn/Ag/Ni base plating is used to achieve good electrical properties, then contact resistance is reduced, but insertability and extractability deteriorate
Solution Approach 1:
The chemical composition parameters of the plating layers are optimized. Specifically, the Ag intermediate layer composition and thickness are controlled to provide appropriate friction characteristics, while the Sn outer layer maintains low contact resistance. This parameter optimization allows simultaneous achievement of good electrical properties and mechanical insertability.
3Reliability
If plating layers are applied to improve corrosion resistance, then durability is enhanced, but the structure becomes more complex
Solution Approach 1:
Different functional properties are assigned to different layers: the Ag intermediate layer provides corrosion resistance and whisker suppression, while the Sn/Sn alloy outer layer provides solderability and oxidation resistance. This local differentiation of quality allows each layer to perform its specific function efficiently without requiring excessive complexity in the overall structure.
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 proposed structure achieves low insertability/extractability, reduced whisker formation, and enhanced durability, including improved heat resistance and gas corrosion resistance, while maintaining solder wettability and contact properties.
Implementation Method 1
a middle layer of Ag, Au, Pt, Pd, Ru, Rh, or Ir... to prevent diffusion of base material components
Implementation Method 2
a specific underlayer to enhance lubrication
Data Source
AI summary
There are provided an electronic component metal material having low insertability/extractability, low whisker formability and high durability, and a method for manufacturing the electronic component metal material. The electronic component metal material 10 includes a base material 11, an A layer 14 constituting an outermost surface layer on the base material 11 and formed of Sn, In or an alloy thereof, and a B layer 13 constituting a middle layer provided between the base material 11 and the A layer 14 and formed of Ag, Au, Pt, Pd, Ru, Rh, Os, Ir or an alloy thereof, wherein the outermost surface layer (A layer) 14 has a thickness larger than 0.2 μm, and the middle layer (B layer) 13 has a thickness of 0.001 μm or larger.