LED Package Photosensitive Polyimide Insulation Current Spreading
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Solution Overview
Problem
Conventional light emitting device packages experience poor current spreading due to uneven carrier injection, leading to inefficiencies and manufacturing challenges, particularly with the use of SiO2 as a first insulation layer.
Innovation Solution
The use of photosensitive polyimide as a first insulation layer, combined with a reflective silver (Ag) second electrode, improves current spreading and manufacturing efficiency by preventing Ag migration and impurities, while serving as a current blocking layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If SiO2 is used as a first insulation layer, then electrical insulation is provided, but current spreading deteriorates and manufacturing complexity increases
Solution Approach 1:
The patent uses a composite insulation structure consisting of a photosensitive polyimide layer combined with a silicon oxide layer. The photosensitive polyimide provides current blocking functionality and serves as an etch stop layer, while the silicon oxide layer provides electrical insulation. This composite structure resolves the contradiction by combining materials with complementary properties to achieve both good current spreading and reliable electrical insulation.
Solution Approach 2:
The patent changes the material parameter of the first insulation layer from SiO2 to photosensitive polyimide, which fundamentally alters the current blocking characteristics. Photosensitive polyimide allows for precise control of carrier injection by blocking holes effectively while maintaining good current spreading, thus improving manufacturing precision regarding current distribution.
2Reliability
If SiO2 is used as a first insulation layer, then electrical insulation is provided, but device complexity and processing time increase
Solution Approach 1:
The photosensitive polyimide layer performs multiple functions simultaneously: it acts as a current blocking layer to control carrier injection, serves as an etch stop layer during manufacturing processes, and provides part of the electrical insulation. This multi-functionality reduces the need for separate layers, thereby simplifying the overall device structure and reducing processing steps while maintaining reliable electrical insulation.
Solution Approach 2:
The patent merges the functions of current blocking, etch stopping, and electrical insulation into a combined insulation layer structure. By integrating these functions into fewer layers (photosensitive polyimide + silicon oxide), the manufacturing process becomes less complex and processing time is reduced compared to using multiple separate functional layers.
3Power
If silver (Ag) is used in the second electrode for reflection, then light output efficiency improves, but Ag migration and impurity contamination occur
Solution Approach 1:
The patent introduces an intermediary barrier layer between the silver (Ag) second electrode and the light emitting structure. This barrier layer prevents direct contact between Ag and the semiconductor materials, thereby stopping Ag migration and impurity contamination while still allowing the Ag layer to perform its light reflection function effectively. The intermediary layer resolves the contradiction by decoupling the reflective function from the contamination risk.
4Power
If carriers are injected into the active layer, then light emission occurs, but uneven injection deteriorates current spreading
Solution Approach 1:
The patent applies local quality by creating a current blocking layer with spatially selective properties. The photosensitive polyimide layer is positioned specifically at regions where current spreading needs to be controlled, allowing holes to be blocked in certain areas while maintaining injection in other areas. This localized control of carrier injection improves current spreading uniformity across the active layer while still enabling effective light emission.
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 enhances current density and spreading, improves light output power, and simplifies the manufacturing process, reducing defective rates and processing time.
Implementation Method 1
the first insulation layer is provided, thereby protecting the light emitting structure from Ag migration and impurities
Implementation Method 2
in case that a second electrode includes a reflection layer consisting of silver (Ag)
Implementation Method 3
A light emitting diode (LED) is a kind of semiconductor device that converts electricity into infrared rays or light using the properties of a compound semiconductor
Data Source
Figure 1~2
Figure 3~4
Figure 5a~5c
AI summary
A light emitting diode package, according to an embodiment, comprises: a substrate; a light emitting structure that is disposed below the substrate and includes a first conductive type semiconductor layer, an active layer, and a second conductive type semiconductor layer; a first bonding pad connected with the first conductive type semiconductor layer while being embedded in a through-hole formed through the active layer and the second conductive type semiconductor layer, the first conductive type semiconductor layer being exposed through the through-hol; a second bonding pad that is disposed below the second conductive type semiconductor layer while being spaced apart from the first bonding pad and is connected with the second conductive type semiconductor layer; a first insulation layer disposed on the lateral portion of the light emitting structure and on the lower inner edge of the light emitting structure in the through-hole; and a second insulation layer disposed between the first insulation layer and the first bonding pad in the through-hole.