Optical Semiconductor Plating Stack for Reflectance and Sulfidation Resistance
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Solution Overview
Problem
Optical semiconductor devices using silver or silver alloys for reflectance suffer from sulfidation, leading to reduced reflectance and adhesion issues with resin materials, which affects their reliability and luminous flux.
Innovation Solution
A metallic structure comprising a nickel or nickel alloy plated layer, a gold or gold alloy plated layer, and a thin silver or silver alloy plated layer, with the silver layer having a thickness of 0.001 μm to 0.01 μm, enhancing reflectance and adhesion while suppressing sulfidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If silver or silver alloy plated layer is used to achieve high reflectance, then reflectance is improved, but sulfidation occurs leading to reduced reliability and adhesion
Solution Approach 1:
The patent divides the protective coating into multiple functional layers: a nickel or nickel alloy plated layer (0.5-5 μm) as the base layer providing sulfidation resistance, and a thin silver or silver alloy plated layer (0.001-0.01 μm) as the top layer providing high reflectance. This segmentation allows each layer to perform its specific function without compromising the other, resolving the contradiction between reflectance and sulfidation resistance.
Solution Approach 2:
The patent employs a composite plated structure combining nickel/nickel alloy and silver/silver alloy layers. The nickel layer serves as a protective barrier against sulfidation, while the silver layer provides the desired optical reflectance properties. This composite material approach enables simultaneous achievement of high reflectance and sulfidation resistance.
2Illumination intensity
If silver layer thickness is increased to improve reflectance, then reflectance is improved, but adhesion to resin materials deteriorates
Solution Approach 1:
The patent optimizes the thickness parameter of the silver plated layer to a specific range (0.001-0.01 μm). This parameter change ensures that the silver layer is thin enough to maintain good adhesion to resin materials while still providing sufficient reflectance. The nickel layer beneath provides the primary structural support and bonding interface with the resin, decoupling the adhesion function from the reflectance function.
3Reliability
If gold plating is used to improve sulfidation resistance, then reliability is improved, but reflectance is reduced compared to silver
Solution Approach 1:
The patent segments the protective function from the optical function. The nickel layer provides sulfidation resistance (reliability), while the thin silver layer provides high reflectance. This segmentation allows achieving both high reflectance and sulfidation resistance, overcoming the limitation of gold plating which provides sulfidation resistance but lower reflectance.
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 provides high reflectance and improved adhesion to resin materials, maintaining luminous flux and preventing sulfidation discoloration, thus enhancing the reliability and performance of optical semiconductor devices.
Implementation Method 1
forming a nickel or nickel alloy plated layer on the base body, optionally forming a rhodium, palladium, rhodium alloy, or palladium alloy plated layer on the nickel or nickel alloy plated layer, forming a gold or gold alloy plated layer on the nickel or nickel alloy plate layer or optionally on the rhodium, palladium, rhodium alloy or palladium alloy plated layer if it is present, and forming a silver or silver alloy plated layer on the gold or gold alloy plated layer
Implementation Method 2
a lead frame or a substrate, on which a silver or silver alloy plating having high reflectance with respect to light emitted from the light emitting element is provided
Data Source
AI summary
A metallic structure for an optical semiconductor device, including a base body having disposed thereon at least in part metallic layers in the following order; a nickel or nickel alloy plated layer, a gold or gold alloy plated layer, and a silver or silver alloy plated layer, wherein the silver or silver alloy plated layer has a thickness in a range of 0.001 μm or more and 0.01 μm or less.