LED Electrode Plated Silver Alloy Contact Resistance
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Solution Overview
Problem
The luminous efficiency of light-emitting diode (LED) chips is hindered by high contact resistance between electrodes and epitaxial layers, as well as high resistance values in the electrodes themselves, which affects both internal and external quantum efficiency.
Innovation Solution
A semiconductor light-emitting device with an electrode comprising a plated silver alloy (Ag1-xYx) layer, where Y includes metals like gold or palladium, and an adhesive and seed layer, formed through electroplating, electroless plating, or sputtering, to improve electrical and thermal conductivity, and reduce contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional electrode structure is used, then the device complexity is low, but the contact resistance between electrode and epitaxial layer is too high
Solution Approach 1:
The electrode is designed as a composite structure comprising multiple layers: a first electrode layer (e.g., TiW or Ti) providing adhesion to the epitaxial layer, a second electrode layer (e.g., Al or AlSi) providing low electrical resistance, and a plated silver alloy layer (Ag1-xYx) providing excellent electrical conductivity and solderability. This composite structure resolves the contradiction by combining materials with different properties to simultaneously achieve low contact resistance and reasonable structural complexity.
Solution Approach 2:
The electrode is segmented into multiple functional layers, each performing a specific function: the first electrode layer adheres to the epitaxial layer, the second electrode layer provides low-resistance electrical connection, and the plated silver alloy layer provides final electrical contact and solderability. This segmentation allows each layer to be optimized independently, achieving low contact resistance without excessive overall complexity.
2Reliability
If the electrode resistance value is reduced, then the luminous efficiency is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The invention changes the material parameters of the electrode by introducing a plated silver alloy layer with specific composition (Ag1-xYx where x is 0.02-0.15) and controlled thickness (2-8 micrometers). This parameter change achieves low electrode resistance (improving luminous efficiency) while using standard electroplating processes that maintain reasonable manufacturing precision requirements.
Solution Approach 2:
The plated silver alloy layer acts as an intermediary between the underlying electrode layers and the external electrical connections (solder wires). This intermediary layer provides excellent electrical conductivity to minimize resistance losses while being formed by conventional electroplating techniques that do not require excessive manufacturing precision.
3Reliability
If the contact resistance between electrode and solder wire is reduced, then the luminous efficiency is improved, but the device complexity increases
Solution Approach 1:
The plated silver alloy layer (Ag1-xYx) serves as a composite material that combines the excellent electrical conductivity of silver with the solderability provided by the alloying elements (Au, Pd, or their alloys). This composite structure reduces contact resistance with solder wires while maintaining a relatively simple overall electrode design that does not excessively increase device complexity.
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 enhances the electrical conductivity and thermal dissipation of the LED chip, leading to improved bonding characteristics with solder wires and increased luminous efficiency by reducing contact resistance and optimizing electrode design.
Implementation Method 1
a plated silver alloy (Ag1-xYx) layer, wherein the Y of the Ag1-xYx layer includes metals forming a complete solid solution with Ag at arbitrary weight percentage, and the X of the Ag1-xYx layer is in a range from 0.02 to 0.15
Implementation Method 2
the adhesive layer is disposed between the light-emitting diode chip and the Ag1-xYx layer
Data Source
AI summary
A semiconductor light-emitting device including a light-emitting diode chip and an electrode disposed thereon is provided. The electrode at least includes a plated silver alloy (Ag1-xYx) layer, wherein the Y of the Ag1-xYx layer includes metals forming a complete solid solution with Ag at arbitrary weight percentage, and the X of the Ag1-xYx layer is in a range from about 0.02 to 0.15. The fabricating method thereof is also provided.