Flip-Chip LED Package Layout for Higher Luminous Efficacy
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Solution Overview
Problem
Conventional light emitting diode (LED) packages suffer from reduced luminous efficacy due to low reflectivity of leads and obstruction of light by connecting wires, which affects the overall efficiency and performance of the LED.
Innovation Solution
The LED package design incorporates a flip-chip type LED chip with leads that are partially exposed and formed with grooves on their upper surfaces, minimizing their exposure and maximizing reflectivity, and eliminating the need for connecting wires by using larger lead sizes for improved bonding and reduced solder ball formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the first lead and the second lead are completely exposed to the lower surface of the cavity, then electrical connection is facilitated, but luminous efficacy deteriorates due to low reflectivity
Solution Approach 1:
The lead structure is designed with differentiated local properties: the upper surface features grooves for light reflection and diffusion, while the lower surface maintains exposure planes for electrical connection. This local quality differentiation allows the lead to simultaneously fulfill optical and electrical functions without compromising either.
Solution Approach 2:
The lead is segmented into distinct functional zones: grooved upper surfaces for light management and flat exposing planes for electrical connection. This segmentation allows each portion to optimize its specific function while contributing to overall package performance.
2Ease of operation
If connecting wires are used to electrically connect the light emitting diode chip to the leads, then electrical connection is achieved, but light emission is obstructed
Solution Approach 1:
The lead structure merges the electrical connection function and light reflection function into a single integrated component. The lead directly contacts the electrode pads while its grooved upper surface reflects and diffuses light, eliminating the need for separate connecting wires that would obstruct light emission.
Solution Approach 2:
The connecting wire, which causes light obstruction, is completely removed from the system. The lead itself is designed to perform both electrical connection and light reflection functions, extracting the harmful element while maintaining necessary functionality.
3Loss of energy
If the lead size is reduced to minimize exposure, then luminous efficacy improves, but bonding strength decreases and solder ball formation increases
Solution Approach 1:
The lead design implements local quality optimization with grooved upper surfaces for light reflection and adequately sized lower exposing planes for strong electrical bonding. This allows minimal necessary exposure for both optical and electrical functions while maintaining bonding strength and reducing solder ball formation.
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 design enhances luminous efficacy by minimizing lead exposure, improving bonding strength, and preventing light obstruction, resulting in increased efficiency and accuracy of light emission.
Implementation Method 1
A light emitting diode is an inorganic light source adapted to generate light through recombination of electrons and holes
Implementation Method 2
the first lead and the second lead have lower reflectivity than the housing, thereby causing deterioration in luminous efficacy
Data Source
AI summary
A light emitting diode package includes a light emitting diode chip provided at a lower side thereof with a first electrode pad and a second electrode pad, a first lead and a second lead spaced apart from each other and contacting the first electrode pad and the second electrode pad of the light emitting diode chip to be electrically connected thereto, respectively, and a housing formed to surround the first lead and the second lead and having a cavity open at a top portion thereof. The first lead and the second lead have a first lead exposing plane and a second lead exposing plane disposed on a lower surface of the cavity of the housing and partially exposing the first lead and the second lead, respectively.