Leadframe-Based SMT Segmented Display Eliminating Hotspots
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Solution Overview
Problem
Current segmented display designs using Surface Mount Technology (SMT) with Printed Circuit Boards (PCBs) suffer from air gaps between the epoxy layer and LED packages, leading to hotspots and uneven color distribution due to the epoxy meniscus, resulting in suboptimal light diffusion and intensity performance.
Innovation Solution
Employing a leadframe as the substrate instead of a PCB, with leads extending outside the package body to facilitate SMT mounting, and using a single encapsulant to fill cavities and segments, ensuring the light source is in close proximity to the epoxy, thereby eliminating the air gap and promoting even light dispersion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a PCB substrate with air gap between epoxy layer and LED package is used, then manufacturing is easier, but light diffusion is reduced causing hotspots and uneven color distribution
Solution Approach 1:
The patent merges the LED package mounting surface with the epoxy layer by eliminating the air gap through underfill material. The epoxy is extended to flow beneath the LED package, creating direct optical contact between the light source and the diffusing epoxy medium, thereby improving light diffusion while maintaining manufacturing feasibility.
Solution Approach 2:
The patent introduces underfill material as an intermediary substance between the LED package and the PCB substrate. This underfill serves as a bridge that eliminates the air gap, enabling effective optical coupling and light diffusion from the LED package through the epoxy layer without compromising the structural integrity or ease of manufacture.
2Illumination intensity
If a leadframe substrate with epoxy in close proximity to LED package is used, then light diffusion is improved eliminating hotspots, but device complexity increases
Solution Approach 1:
The patent combines the leadframe substrate structure with the epoxy filling process, where the epoxy is designed to flow into and fill the space between the leadframe and the PCB, as well as surrounding the LED package. This merging of structural support and optical diffusion functions into a single integrated approach reduces overall device complexity while achieving superior light diffusion.
Solution Approach 2:
The epoxy material serves multiple functions simultaneously: it acts as the substrate adhesive bonding the leadframe to the PCB, provides structural support for the LED package, and functions as the optical diffusing medium to eliminate hotspots. This multi-functionality reduces the need for separate components, thereby simplifying the overall device structure despite the advanced design.
3Ease of manufacture
If air gap is maintained between epoxy and LED package, then manufacturing is simpler, but hotspots and discoloration occur reducing display quality
Solution Approach 1:
The underfill material acts as an intermediary that eliminates the harmful air gap while maintaining manufacturing simplicity. The epoxy is formulated to flow and fill the gap space during the manufacturing process, creating uniform optical contact without requiring complex precision assembly, thus achieving both ease of manufacture and high display quality.
Solution Approach 2:
The patent modifies the physical parameters of the epoxy material, specifically its viscosity and flow characteristics, to enable it to naturally fill the gap between the LED package and the substrate during manufacturing. This parameter change allows the epoxy to self-adjust and eliminate air gaps without requiring high-precision positioning or complex manufacturing processes, thereby maintaining both manufacturing simplicity and display quality.
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 eliminates hotspots and discoloration, ensuring uniform color and brightness across segments while maintaining or improving intensity performance by ensuring even light distribution and reducing the occurrence of hotspots.
Implementation Method 1
a single encapsulant/epoxy is used to fill the segment cavities as well as the main cavity that receives the leadframe
Implementation Method 2
creating sufficient diffusion properties for light dispersion. Specifically, the meniscus of the epoxy is removed to promote even color distribution
Data Source
AI summary
A multi-segment display is disclosed. The multi-segment display includes substantially no hotspots and is substantially free of color discoloration that accompanies hotspots. The multi-segment display is configured for surface mounting. The multi-segment display is provided with a leadframe that fits into a package body thereby placing the light sources mounted on the leadframe in closer proximity to the encapsulant that fills vias of each segment.