LED Lead Frame Composite Coating Corrosion Protection
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Solution Overview
Problem
Conventional light emitting diodes (LEDs) face issues with corrosion and reduced luminance due to moisture and heat sensitivity of silver (Ag) lead frames, while gold (Au) alternatives offer low light reflectivity, compromising efficiency.
Innovation Solution
A lead frame design incorporating a base metal layer, a light-reflecting layer of silver (Ag) or aluminum (Al), and a protection layer of gold (Au), nickel (Ni), or titanium (Ti) to maintain high reflectivity while preventing corrosion, with optimal thicknesses of the protection layer determined to balance reflectivity and protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a lead frame coated with silver (Ag) is used to enhance light reflectivity, then light reflectivity is improved, but the lead frame becomes vulnerable to moisture and heat causing corrosion and discoloration
Solution Approach 1:
The invention uses a composite coating structure with multiple layers: a base metal layer (copper or copper alloy), a light-reflecting layer (silver or aluminum), and a protection layer (gold, nickel, or titanium). This composite structure combines the high reflectivity of silver/aluminum with the corrosion resistance of gold/nickel/titanium, resolving the contradiction between reflectivity and corrosion resistance.
Solution Approach 2:
The protection layer acts as an intermediary between the light-reflecting layer and the external environment (moisture and heat). This intermediary layer prevents direct contact between the silver/aluminum and corrosive elements, maintaining both high reflectivity and corrosion resistance simultaneously.
2Reliability
If a lead frame coated with gold (Au) is used to prevent corrosion, then corrosion resistance is improved, but light reflectivity decreases lowering LED efficiency
Solution Approach 1:
Instead of using pure gold coating, the invention creates a composite structure where gold serves only as the thin protection layer (0.1-10 nm) over the silver light-reflecting layer. This allows the system to benefit from gold's corrosion resistance while maintaining the high reflectivity of the underlying silver layer.
Solution Approach 2:
The gold layer is applied locally and selectively as a thin protection layer only where needed for corrosion resistance, rather than coating the entire lead frame thickly. This localized application maintains overall high reflectivity while providing targeted corrosion protection.
3Reliability
If the protection layer thickness is increased to enhance corrosion protection, then reliability is improved, but light reflectivity may be reduced
Solution Approach 1:
The invention optimizes the thickness parameter of the protection layer to a specific range (0.1-10 nm for gold, 0.1-20 nm for nickel or titanium). Within this parameter range, the protection layer provides sufficient corrosion resistance while remaining thin enough to maintain high light reflectivity, resolving the contradiction between protection thickness and reflectivity.
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 ensures high light reflectivity and extended lifespan of LEDs by preventing corrosion and maintaining efficiency, with the optimal protection layer thickness ranging from 0.1 nm to 600 nm for gold (Au) and 0.1 nm to 20 nm for nickel (Ni) or titanium (Ti), thereby enhancing the LED's performance and reliability.
Implementation Method 1
a light-reflecting layer, and a protection layer arranged on the light-reflecting layer
Data Source
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AI summary
An LED includes a light-emitting chip, a metal member, and a housing. The light-emitting chip generates light. The light-emitting chip is arranged on the metal member. The housing is combined with the metal member to fix the metal member. The housing has an opening portion exposing at least a portion of the light-emitting chip and the metal member. The metal member includes a base metal layer, a light-reflecting layer arranged on the base metal layer, and a protection layer arranged on the light-reflecting layer and including a metal.