Nickel Tungsten Lead Plating for Solder Joint Crack Resistance
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Solution Overview
Problem
Existing lead plating solutions for electronic devices either increase fabrication costs and cycle times or fail to accommodate larger package sizes and reduced lead pitch dimensions, leading to poor board level reliability due to solder joint cracking.
Innovation Solution
A bilayer plated structure comprising a nickel tungsten first layer and a matte tin second layer on conductive leads, applied post-molding, which provides a diffusion barrier and enhances solderability, reducing cracking and improving reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pre-plating lead frames before packaging operations, then board level reliability is improved, but fabrication cost increases and cycle time lengthens
Solution Approach 1:
The patent applies preliminary action by performing the plating operation after molding but before final device assembly and testing. The lead frames are plated in-situ within the molded package structure, which allows the diffusion barrier to be applied before the device is fully assembled, ensuring reliability while avoiding the need to plate entire lead frame panels in advance, thus reducing fabrication cost and cycle time
Solution Approach 2:
The patent extracts the plating operation from the pre-packaging process and relocates it to post-molding. By taking out the plating step from the traditional pre-packaging sequence and performing it after molding, the process avoids the cost and time penalties of pre-plating entire lead frame panels while still achieving the reliability benefits of having a diffusion barrier before final assembly
2Reliability
If pre-plating lead frames before packaging operations, then board level reliability is improved, but fabrication cycle time is lengthened
Solution Approach 1:
The patent applies preliminary action by performing the plating operation after molding but before final device assembly and testing. The lead frames are plated in-situ within the molded package structure, which allows the diffusion barrier to be applied before the device is fully assembled, ensuring reliability while avoiding the need to plate entire lead frame panels in advance, thus reducing fabrication cost and cycle time
Solution Approach 2:
The patent merges the plating operation with the post-molding processing sequence. By combining the plating step with other post-molding operations rather than treating it as a separate pre-packaging step, the process achieves efficient utilization of manufacturing resources and reduces overall fabrication cycle time while maintaining the reliability benefits
3Ease of manufacture
If using traditional lead plating solutions, then manufacturing cost is reduced, but board level reliability deteriorates due to solder joint cracking
Solution Approach 1:
The patent applies composite materials by using a bilayer plated structure consisting of a nickel tungsten diffusion barrier layer and a tin solderable layer. This composite plating structure provides both the corrosion resistance and solderability needed for reliable solder joints, while the nickel tungsten barrier prevents copper diffusion that would otherwise cause reliability failures, all at a cost comparable to traditional single-layer plating
4Ease of manufacture
If using traditional lead plating solutions, then fabrication cost is reduced, but solder joint cracking occurs reducing reliability
Solution Approach 1:
The patent applies composite materials by using a bilayer plated structure consisting of a nickel tungsten diffusion barrier layer and a tin solderable layer. This composite plating structure provides both the corrosion resistance and solderability needed for reliable solder joints, while the nickel tungsten barrier prevents copper diffusion that would otherwise cause reliability failures, all at a cost comparable to traditional single-layer plating
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 plated structure achieves cost-effective board level reliability improvements by mitigating solder joint cracking, especially in larger packages with reduced lead pitch, while maintaining manufacturing efficiency.
Implementation Method 1
The conductive lead includes a first plated layer on a portion of the conductive lead, the first plated layer including nickel tungsten
Implementation Method 2
a second plated layer on the first plated layer, the second plated layer including tin, and the second plated layer exposed outside the package structure
Data Source
AI summary
An electronic device includes a package structure and a conductive lead with a first surface having a first plated layer including nickel tungsten and a second plated layer including tin on the first plated layer. A method includes forming a first plated layer on a first surface of a conductive lead exposed along a bottom side of a molded structure in a panel array, performing a second plating process that forms a second plated layer including tin on the first plated layer, and performing a package separation process that separates an electronic device from the panel array.