Conductive Lead Bilayer Plating for Solder Joint Reliability
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Solution Overview
Problem
Copper integrated circuit leads plated with tin can lead to material deterioration and board level reliability issues due to cracking and defects at solder joints, and thermal dissipation challenges in compact, high-integration electronic systems.
Innovation Solution
A bilayer plating process on conductive leads, where the first layer includes cobalt and the second layer includes tin, is applied to improve board level reliability and thermal dissipation by forming a diffusion barrier and enhancing the mechanical properties of the solder interface, while a plated copper layer with a nickel metal layer facilitates better thermal transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If tin plating is applied to copper leads to enhance shelf life, then material deterioration is mitigated, but board level reliability deteriorates due to cracking and defects at solder joints
Solution Approach 1:
The patent divides the single tin plating layer into a multi-layer structure with cobalt, nickel, and tin layers. This segmentation allows each layer to perform its specific function: cobalt for diffusion barrier, nickel for structural support, and tin for corrosion protection, thereby resolving the contradiction between shelf life and reliability
Solution Approach 2:
The patent uses composite plating structure combining multiple materials (cobalt, nickel, tin) on copper leads. This composite approach creates a diffusion barrier that prevents intermetallic compound formation while maintaining corrosion protection, thus improving board level reliability without sacrificing shelf life
2Productivity
If compact and highly integrated systems with smaller features and higher currents are designed, then integration density is improved, but thermal dissipation capability deteriorates
Solution Approach 1:
The patent applies different material properties to different regions of the lead structure. The cobalt layer provides localized diffusion barrier properties at the solder interface, while the copper core maintains high electrical and thermal conductivity, enabling compact design with improved thermal management
Solution Approach 2:
The patent changes the material composition parameters of the plating layers to optimize thermal performance. By selecting materials with specific thermal conductivity and melting point properties, the system achieves better thermal dissipation in compact high-integration designs
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 bilayer plating process reduces the formation of crack-susceptible intermetallic compounds, enhancing shelf life and reliability by minimizing defects and improving thermal dissipation, thus ensuring stable operation of electronic devices at high temperatures.
Implementation Method 1
The formation of inter-metallic compounds (IMCs) such as Cu3Sn and Cu6Sn5 is decelerated resulting in higher BLR performance since cobalt and copper have very low solubility in each other
Implementation Method 2
performing an electroless plating process that forms a plated copper layer on and contacting the metal layer on the side of the semiconductor die
Data Source
AI summary
An electronic device includes a semiconductor die, a package structure enclosing the semiconductor die, and a conductive lead having first and second surfaces. The first surface has a bilayer exposed along a bottom side of the package structure, and the second surface is exposed along another side of the package structure. The bilayer includes first and second plated layers, the first plated layer on and contacting the first surface of the conductive lead and the second plated layer on and contacting the first plated layer and exposed along the bottom side of the package structure, where the first plated layer includes cobalt, and the second plated layer includes tin.