CSP LED Packaging with Light-Blocking Glue
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Solution Overview
Problem
Current CSP LED packaging processes are inefficient for large-scale production due to complex processes and issues with light utilization, such as the formation of yellow circles and inconsistent light emission, which affect the reliability of electrical connections and overall light efficiency.
Innovation Solution
A method involving the use of a fixed film to position LED chips, applying light-blocking glue, grinding to expose top surfaces, and coating a fluorescent glue layer to ensure uniform light emission from a single surface, while using a combined cutter to separate individual LEDs, thereby blocking side light emission and enhancing light utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If spraying a reflecting layer on the bottom surface and side surfaces of packaging glue to form a single light-emitting surface, then light extraction efficiency is improved and angle of light emitted is controlled, but packaging process becomes complicated and not suitable for large-scale production
Solution Approach 1:
The patent extracts the light-blocking function from the packaging glue itself by using a separate light-blocking layer (metal layer or dielectric layer with reflective coating) applied to the bottom and side surfaces. This separation allows the packaging glue to focus on encapsulation while the dedicated light-blocking layer handles light direction control, simplifying the overall process for large-scale production.
Solution Approach 2:
The light-blocking layer is applied to the bottom and side surfaces of the packaging glue before final encapsulation. This preliminary action ensures that light is blocked in the desired directions from the outset, eliminating the need for complex post-processing steps and enabling efficient large-scale manufacturing.
2Quantity of substance
If using molding or printing to form fluorescent glue layer, then fluorescent glue can be applied to LED chip surface, but production efficiency is low due to complicated fluorescent glue forming processes
Solution Approach 1:
The patent uses a dispensing system with a movable dispensing head to apply fluorescent glue droplets to the LED chip array. This hydraulic/pneumatic dispensing method is much faster and more efficient than traditional molding or printing processes, enabling high-volume production while ensuring complete coverage of the chip surfaces.
Solution Approach 2:
The patent combines multiple operations into a single dispensing process: the dispensing head simultaneously applies fluorescent glue to multiple chips in an array configuration, and the system can integrate the dispensing with the mounting process. This merging of operations dramatically increases production efficiency compared to individual chip processing.
3Weight of moving object
If cutting chip groups into single CSPs after packaging fluorescent glue, then individual CSP LEDs can be obtained, but downward burrs are formed on the lower edge of fluorescent glue layer causing rugged phenomenon
Solution Approach 1:
The patent applies a protective layer over the fluorescent glue before cutting. This preliminary protective coating prevents the cutting blade from directly contacting and damaging the fluorescent glue layer, thereby preventing burr formation and maintaining a smooth surface on the lower edge of the glue layer after individual CSPs are separated.
Solution Approach 2:
The protective layer acts as an intermediary between the cutting blade and the fluorescent glue layer. It absorbs the mechanical stress of cutting and protects the fluorescent glue from direct contact with the blade, preventing the rugged phenomenon that would otherwise occur at the cut edges.
4Productivity
If placing multiple chips on film and packaging fluorescent glue simultaneously, then large-scale production can be achieved, but expansion of fluorescent glue layer during heating causes loose contact or void contact with substrate
Solution Approach 1:
The patent forms a step structure between the electrode and fluorescent glue before mounting on the substrate. This preliminary step formation creates a built-in compensation mechanism that accommodates the expansion of the fluorescent glue layer during subsequent heating processes, preventing loose contact or void formation and maintaining reliable electrical connections.
Solution Approach 2:
The step structure acts as a cushioning feature that anticipates and compensates for the expansion of the fluorescent glue layer during heating. By creating this extra space beforehand, the patent prevents the harmful effects of expansion (loose contact, void contact) while maintaining the benefits of large-scale simultaneous packaging.
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 method allows for efficient large-scale production of CSP LEDs with improved light emission consistency and reliability, preventing yellow circles and enhancing the total light efficiency by ensuring only top surface emission, thus addressing the limitations of existing CSP LED packaging.
Implementation Method 1
coating a fluorescent glue layer on the LED chips array with a smooth surface so that the top surfaces of the LED chips and that of the light-blocking glue being fully covered by the fluorescent glue layer
Data Source
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AI summary
A method of packaging CSP LED, comprising the following steps: placing LED chips on a carrier plate; coating light-blocking glue or fluorescent glue on the LED chips; at last cutting to form CSP LEDs with coating light-blocking glue or fluorescent glue outside the chip. Multiple LEDs, from one surface of which light could be emitted, could be fabricated simultaneously by using the packaging process in present invention. The process is simple and able to prevent yellow light from appearing at the bonding surface of the light-blocking glue and the chip. The present invention also provides a CPS LED with the chip covered by packaging glue and the electrode of the chip protruding exposed and protruding. The present invention also provides CPS LEC, from three surfaces of which light could be emitted, with light-blocking glue arranged on two side surfaces and fluorescent glue arranged one other surfaces. This kind of LED could be used in various fields such as backlight and light bar, from side surfaces of which light could be emitted.