CSP LED Fabrication via Segmented Phosphor Encapsulation
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Solution Overview
Problem
Conventional methods for fabricating CSP LEDs result in restricted bonding areas of electrode pads due to phosphor encapsulation, leading to potential contamination and deterioration of electrical performance, and increased risk of external contamination during processing.
Innovation Solution
The method involves preparing flip-type LED chips without initial electrode pads on the lower surfaces, arraying them on a temporary support sheet, forming a wavelength converting member covering all surfaces, removing the sheet to expose and form electrode pads, and cutting the member to increase bonding areas and reduce phosphor contact, ensuring stable electrical connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the phosphor encapsulation covers the side surfaces and lower surfaces of the LED chip, then the LED chip is protected and the structure is simplified, but the bonding area of the electrode pads is restricted and electrical reliability deteriorates
Solution Approach 1:
The patent segments the encapsulation process into two distinct stages: first forming the phosphor layer on the upper surface, then adding a separate transparent resin encapsulation layer that specifically covers the side surfaces while leaving the lower surface electrode pads exposed. This segmentation allows the bonding area to be preserved while still providing protective encapsulation where needed.
Solution Approach 2:
The patent applies different materials and coverage to different regions of the LED chip. The phosphor-containing resin layer is applied locally to the upper surface for light conversion, while the transparent resin encapsulation layer is applied to the side surfaces for protection, deliberately leaving the lower surface electrode pads uncovered to maintain bonding area and electrical reliability.
2Ease of manufacture
If the phosphor encapsulation covers the electrode pads, then the manufacturing process is simplified, but the risk of phosphor contamination on electrode pads increases
Solution Approach 1:
The patent performs preliminary actions by first forming the phosphor layer on the upper surface, then adding the transparent resin encapsulation layer to cover the side surfaces before final assembly. This sequence ensures that electrode pads are never exposed to phosphor material, preventing contamination while maintaining manufacturing efficiency.
Solution Approach 2:
The patent extracts the phosphor material from the side surface region by using a two-layer encapsulation system where the phosphor-containing resin is confined to the upper surface and the transparent resin encapsulation layer covers the side surfaces without phosphor, thereby eliminating phosphor contamination risk on electrode pads.
3Ease of operation
If the upper surfaces are exposed before phosphor encapsulation, then the processing access is improved, but the risk of foreign material contamination increases
Solution Approach 1:
The patent applies preliminary protective action by forming the phosphor-containing resin layer on the upper surface early in the process, which immediately protects the exposed upper surface from foreign material contamination while still allowing subsequent side surface encapsulation to proceed efficiently.
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 approach enhances electrical reliability by increasing the contact areas of electrode pads and reducing contamination risks, resulting in improved structural stability and defect-free connections during mounting on substrates.
Implementation Method 1
forming a phosphor-containing resin layer covering the side and upper surfaces of the flip LED chips
Data Source
AI summary
Disclosed is a method for fabricating CSP LEDs. The method includes: preparing a plurality of flip-type LED chips, each of which includes a substrate and a semiconductor stack structure formed under the substrate and has a first conductive connection area and a second conductive connection area formed under the semiconductor stack structure; arraying the first conductive connection areas and the second conductive connection areas of the plurality of flip-type LED chips on a temporary support sheet; forming a wavelength converting member, which includes a side surface portion surrounding the side surfaces of the substrate and the semiconductor stack structure, an intermediate portion overlying the side surface portion to cover the upper surface of the substrate, and an upper surface portion overlying the intermediate portion, on the temporary support sheet; and removing the temporary support sheet and forming first electrode pads and second electrode pads in the first conductive connection areas and the second conductive connection areas of the flip-type LED chips, respectively. The first electrode pads and the second electrode pads protrude more downward than the lower surface of the wavelength converting member.