Optical Semiconductor Package Copper Diffusion Barrier
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Solution Overview
Problem
Conventional optical semiconductor device packages face issues with a decrease in reflectance due to copper diffusion and shortening of lifespan caused by photocatalytic action of titanium oxide in the resin enclosure, leading to silver blackening over time.
Innovation Solution
The optical semiconductor device package incorporates a circuit board with a first metal (e.g., copper), a second metal (palladium) as a barrier layer, and a third metal (silver) with specific standard electrode potentials, where palladium prevents copper diffusion and silver acts as a reflective layer, while the electrode potential difference facilitates sacrificial corrosion to protect against active oxygen.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If silver plating is provided on copper or copper alloy to improve reflectance, then luminous efficiency is improved, but copper diffusion occurs due to heat generation causing discoloring and reflectance decrease
Solution Approach 1:
An intermediary barrier layer comprising at least one of a nickel layer or a palladium layer is introduced between the copper base material and the silver plating layer. This barrier layer prevents copper atoms from diffusing into the silver layer while allowing the silver to maintain its high reflectance properties, thus resolving the contradiction between improving luminous efficiency and maintaining reflectance stability.
Solution Approach 2:
The patent creates a composite multi-layer structure consisting of copper base material, barrier layer (nickel or palladium), and silver plating layer. This composite structure combines the advantages of each material: copper provides electrical conductivity and cost-effectiveness, the barrier layer provides diffusion prevention, and silver provides high reflectance, thereby resolving the technical contradiction.
2Reliability
If nickel plating and palladium plating are applied as barrier layers to prevent copper diffusion, then reflectance stability is improved, but device complexity increases
Solution Approach 1:
The patent applies the local quality principle by making the barrier layer composition adaptable - it can be either nickel or palladium depending on specific requirements. This flexibility allows optimization for different applications without requiring a fixed complex multi-layer structure, thus improving reflectance stability while controlling device complexity.
3Use of energy by moving object
If titanium oxide is used as white pigment in resin enclosure for light reflection, then luminous efficiency is improved, but photocatalytic action generates active oxygen causing silver blackening
Solution Approach 1:
The patent converts the harmful photocatalytic action of titanium oxide into a beneficial protective mechanism. By introducing a sacrificial aluminum layer that is more susceptible to oxidation than silver, the system allows aluminum to preferentially react with active oxygen generated by titanium oxide photocatalysis, thereby protecting the silver plating from blackening while maintaining the luminous efficiency benefits of titanium oxide reflection.
Solution Approach 2:
The aluminum sacrificial layer acts as an intermediary between the titanium oxide photocatalyst and the silver plating. It mediates the harmful interaction by absorbing the oxidative stress from active oxygen, thus protecting the silver from blackening while allowing the titanium oxide to continue functioning as an effective reflector.
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
This configuration effectively inhibits reflectance decrease and extends the lifespan of the device by preventing copper diffusion and silver blackening, maintaining high emission luminance over long-term use.
Implementation Method 1
a second metal (palladium) as a barrier layer... palladium prevents copper diffusion
Implementation Method 2
a third metal (silver) with specific standard electrode potentials, where palladium prevents copper diffusion and silver acts as a reflective layer
Implementation Method 3
the electrode potential difference facilitates sacrificial corrosion to protect against active oxygen
Data Source
AI summary
An optical semiconductor device package includes a circuit board in which a first metal, a second metal, and a third metal are sequentially stacked in an optical semiconductor element mounting region. The first metal has a first standard electrode potential. The second metal is disposed on a portion of an upper surface of the first metal and has a second standard electrode potential that is greater than the first standard electrode potential. The third metal is disposed on the upper surface of the first metal and an upper surface of the second metal and has a third standard electrode potential that is greater than the first standard electrode potential and less than the second standard electrode potential.