Ribbed Connector Strips for Uniform LED Current Distribution
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Solution Overview
Problem
Overvoltage-protected light-emitting semiconductor devices face challenges in achieving uniform current distribution and constant light emission intensity due to the fragility of conventional connector strips and the high resistivity of current-spreading films like ITO, which can lead to breakage during fabrication.
Innovation Solution
The use of ribbed connector strips made from materials with lower resistivity than the current-spreading film, coupled via slits in a transparent overlay that also serves as a stress mitigator, ensures uniform current distribution and enhances the structural integrity of the connector strips.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If ITO film is used as current-spreading film, then optical transparency is improved, but electrical conductivity deteriorates
Solution Approach 1:
The patent combines ITO film with metal filamentary connectors to create a composite current distribution system. The ITO provides optical transparency while the metal filaments provide low-resistance current paths, achieving both transparency and conductivity requirements simultaneously.
Solution Approach 2:
The current-spreading function is segmented into two components: the ITO film for broad-area current distribution and metal filamentary connectors for point-to-point current conduction. This segmentation allows each component to optimize its specific function without compromise.
2Illumination intensity
If thin ITO film is fabricated, then optical transparency is improved, but sheet resistance increases
Solution Approach 1:
By combining thin ITO film with metal filamentary connectors, the system achieves low sheet resistance without increasing ITO thickness. The metal filaments compensate for the high resistance of the thin ITO layer.
Solution Approach 2:
The metal filamentary connectors act as intermediaries that bridge the bonding pad and the ITO film, providing additional current pathways that reduce the overall sheet resistance of the current-spreading structure.
3Device complexity
If connector strips are made fragile, then fabrication complexity is reduced, but manufacturing reliability deteriorates
Solution Approach 1:
The connector strips are designed as thin, flexible metal structures that can bend and conform during fabrication processes. This flexibility allows them to withstand fabrication stresses without breaking, improving manufacturing reliability.
Solution Approach 2:
The connector strips are designed with inherent flexibility and compliance to cushion against fabrication stresses before they can cause breakage. This prior cushioning prevents damage during the fabrication process.
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 achieves a more consistent and efficient light emission from the entire light-emitting surface while reducing the likelihood of connector strip breakage, thereby improving the overall performance and reliability of the overvoltage-protected LED.
Implementation Method 1
Overvoltage protectors that can be integrated with light-emitting semiconductor devices according to the invention include, but are not limited to, the Schottky barrier diode
Implementation Method 2
Overvoltage protectors that can be integrated with light-emitting semiconductor devices according to the invention include, but are not limited to, the Schottky barrier diode, pn-junction diode
Implementation Method 3
Overvoltage protectors that can be integrated with light-emitting semiconductor devices according to the invention include, but are not limited to, the Schottky barrier diode, pn-junction diode, varistor
Data Source
AI summary
An LED comprises a multilayered light-generating semiconductor region grown on one of a pair of opposite major surfaces of a semiconducting silicon substrate, a bonding pad overlying the light-generating semiconductor region and received in part in a cavity formed centrally therein, and a substrate electrode on the other major surface of the substrate. For protecting the LED from voltage spikes or like transients, an overvoltage protector such as a Schottky barrier diode is interposed between the bonding pad and the substrate. Further, for a uniform current distribution throughout the light-generating semiconductor region, a current-spreading film of electrically conducting, optically transparent material overlies the light-generating semiconductor region and itself covered by a transparent overlay of electrically insulating material. The bonding pad is electrically coupled to the current-spreading film via a plurality of connector strips extending radially from the pad over the transparent overlay. The connector strips have ribs depending therefrom and extending through radial slits in the transparent overlay into electrical contact with the current-spreading film.