Lead-Free Plating Member With Multi-Layer Structure
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Solution Overview
Problem
Conventional methods for suppressing whisker formation on lead-free plating layers in electronic components are insufficient, often requiring complex processes and failing to achieve optimal solder wettability.
Innovation Solution
A plating member with a lead-free material is developed, featuring a multi-layer structure where the average particle diameter of plating particles varies across layers, and the plating particle volume fraction is less than 100%, incorporating voids and pinholes to absorb internal stress, thereby suppressing whisker formation and enhancing solder wettability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a lead-free plating layer is formed on the terminal surface, then environmental burden is reduced, but whiskers are formed on the plating layer
Solution Approach 1:
The invention changes the particle size distribution parameter of the plating layer by controlling the average particle diameter to be 5 μm or less and the particle size standard deviation to be 0.5 μm or less. This parameter optimization suppresses whisker formation while maintaining lead-free composition, resolving the contradiction between environmental protection and whisker suppression.
Solution Approach 2:
The invention uses a composite plating layer structure with fine particles (5 μm or less) having low standard deviation (0.5 μm or less) combined with specific particle size distribution. This composite structure at the micro level creates a dense, uniform plating layer that prevents whisker formation while maintaining lead-free material composition.
2Length of moving object
If the inter-terminal interval is narrowed to several hundred micrometers for downsizing, then electronic components are downsized, but inter-terminal short circuit occurs due to whisker growth
Solution Approach 1:
By changing the particle size parameter to 5 μm or less and controlling the standard deviation to 0.5 μm or less, the invention creates a uniformly fine-grained plating layer that suppresses whisker growth. This enables safe narrowing of inter-terminal intervals to several hundred micrometers without short circuit risk, achieving component downsizing while maintaining reliability.
3Object-generated harmful factors
If the particle size of plating particles is reduced to suppress whiskers, then whisker formation is suppressed, but manufacturing complexity increases
Solution Approach 1:
The invention establishes specific parameter ranges (average particle diameter ≤5 μm, standard deviation ≤0.5 μm) that can be achieved through conventional plating process adjustments. This approach suppresses whisker formation without requiring complex manufacturing processes, as the parameters can be controlled through standard plating condition optimizations.
4Object-generated harmful factors
If a multi-layer plating structure is formed to suppress whiskers, then whisker formation is suppressed, but solder wettability deteriorates
Solution Approach 1:
Instead of using multi-layer structures, the invention changes the particle size distribution parameters to achieve uniform fine particles (average ≤5 μm, standard deviation ≤0.5 μm). This single-layer approach with optimized parameters simultaneously achieves whisker suppression and maintains good solder wettability, avoiding the wettability deterioration problem associated with multi-layer structures.
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 suppresses whisker growth and improves solder wettability, ensuring reliable performance in electronic components by managing internal stress through controlled voids and pinholes in the plating layer.
Implementation Method 1
the plating particle volume fraction of the plating layer is less than 100% when the proportion of plating particles occupying a unit volume is defined as a plating particle volume fraction of 100% on the assumption that a unit volume is filled with plating particles each having the maximum average particle diameter
Data Source
AI summary
A plating member comprising a lead-free plating material is obtained by the present invention in a manner such that whisker formation on a plating layer 16 of the plating member can be suppressed and thus the plating member has good solderability. In the case of such plating member having, on the surface of a base material 15, a plating layer 16 comprising a lead-free material (Sn—Cu alloy, etc.), the plating layer 16 has a layer structure of two or more layers (a1 to a3), the average particle diameter of plating particles (P1 to P3) constituting each layer varies from layer to layer, and the plating particle volume fraction of the plating layer 16 is 80% to 90% when the proportion of plating particles occupying a unit volume is defined as a plating particle volume fraction of 100% on the assumption that a unit volume 20 is filled with plating particles P3 each having the maximum average particle diameter.