Nickel-Plated Lead Frame for LED Package Corrosion Resistance
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Solution Overview
Problem
Traditional lead frames in LED packages face challenges with hermetic sealing and corrosion due to poor interfacial properties between the lead frame and housing, leading to premature device failure.
Innovation Solution
A lead frame and housing sub-assembly where the lead frame substrate is pre-plated with a nickel layer, ranging from 0.5 to 3 microns, enhancing the interface with the thermoplastic housing and protecting against corrosion, with subsequent plating of exposed areas with transition metals like silver or palladium-gold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a copper or iron substrate is molded with the plastic housing on the bare or un-plated substrate, then the manufacturing process is simplified, but the interface is susceptible to corrosion and/or migration of copper under dynamic conditions
Solution Approach 1:
The patent applies preliminary nickel plating to the lead frame substrate before the molding process. This pre-treatment protects the copper or iron substrate from corrosion and prevents copper migration during subsequent molding and assembly operations, while still allowing the molding process to proceed efficiently.
Solution Approach 2:
The nickel plating layer serves as an intermediary between the copper or iron substrate and the plastic housing. This intermediate layer prevents direct contact between the metal and plastic, blocking corrosion pathways and preventing copper migration, while still allowing the molding process to occur.
2Reliability
If the copper substrate is protected from oxidation before molding, then the interface corrosion resistance is improved, but it is very difficult and/or costly to prevent oxidation of the copper metal
Solution Approach 1:
The patent uses a thin, cost-effective nickel plating layer (0.5-5.0 microns) as a protective barrier against oxidation. This relatively thin and inexpensive nickel layer provides sufficient oxidation protection without requiring complex or costly oxidation prevention processes.
Solution Approach 2:
The nickel plating acts as an intermediary protective layer between the copper substrate and the oxidizing environment. This intermediate nickel layer is much more resistant to oxidation than copper, providing effective protection at low cost and simple implementation.
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 nickel pre-plating improves adhesion and prevents corrosion, resulting in a superior interface that enhances the longevity and reliability of the LED package by ensuring better contact and resistance to moisture and oxidation.
Implementation Method 1
pre-plated with a layer of nickel... protecting against corrosion... resistance to moisture and oxidation
Implementation Method 2
improves adhesion... superior interface that enhances the longevity and reliability
Data Source
AI summary
A lead frame and housing sub-assembly for use in a light emitting diode package, including: a lead frame, wherein the lead frame includes a substrate metal alloy having a top surface and a bottom surface, and wherein the top surface and the bottom surface of the substrate have been pre-plated with a layer of nickel; and a housing, wherein the housing includes a top surface and a bottom surface, and wherein at least a portion of the bottom surface of the housing contacts the top surface of the lead frame that has been pre-plated with the layer of nickel.