Zener Diode Placement on LED Chip Bottom Surface
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Solution Overview
Problem
The integration of a Zener diode as an electrostatic discharge (ESD) protective device in LED packages leads to optical interference due to light-absorbing materials and mechanical interference from wire bonding, resulting in decreased light emission efficiency and increased package size, which is costly.
Innovation Solution
A semiconductor light-emitting device design where a Zener diode with the same or smaller thickness as solder bumps is mounted between them, and an encapsulating layer with reflective powder covers the solder bumps and Zener diode, ensuring no increase in package size and minimizing interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Zener diode is mounted on a lead frame in parallel with the LED chip, then electrostatic discharge protection is provided, but optical efficiency decreases due to light absorption by the Zener diode material
Solution Approach 1:
The Zener diode is relocated from the traditional lead frame mounting position to the bottom surface of the LED chip, changing the spatial dimension of protection. This allows the Zener diode to be positioned underneath the light-emitting region, preventing it from intercepting emitted light while maintaining ESD protection functionality through electrical connection to the chip electrodes
Solution Approach 2:
The Zener diode is extracted from the light path area and placed on the bottom surface of the LED chip, separating the protection function from the light emission function spatially. This extraction eliminates the optical interference caused by the Zener diode material absorbing light while preserving the protective function
2Illumination intensity
If additional space is provided for mounting the Zener diode, then optical efficiency is maintained, but package size increases
Solution Approach 1:
The bottom surface of the LED chip, which traditionally serves only as a mounting surface for the chip itself, is made multi-functional by also serving as the mounting location for the Zener diode. This allows the same space to fulfill both structural support and ESD protection functions, eliminating the need for additional package space
Solution Approach 2:
The mounting functions of the LED chip and Zener diode are merged onto the same bottom surface area. The Zener diode shares the chip's mounting space rather than requiring separate dedicated space, combining the structural and protective functions in a compact configuration that maintains optical efficiency without increasing package dimensions
3Reliability
If wire bonding is used for electrical connectivity of the Zener diode, then ESD protection is achieved, but coating process efficiency decreases due to mechanical interference from wires
Solution Approach 1:
The mechanical wire bonding system is replaced with a direct electrical connection system where the Zener diode is electrically connected to the LED chip electrodes through conductive structures integrated on the chip bottom surface. This substitution eliminates physical wires that would interfere with phosphor coating processes, achieving ESD protection through electrical connectivity without mechanical interference
Solution Approach 2:
Conductive structures on the chip bottom surface serve as intermediaries between the Zener diode and the LED chip electrodes, providing electrical connectivity without requiring external wire bonds. These intermediary conductive paths enable ESD protection while maintaining an unobstructed environment for phosphor coating operations
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 effectively removes optical and mechanical interference while maintaining the light emission efficiency and preventing package size expansion, thus addressing the issues of light absorption and mechanical obstruction.
Implementation Method 1
an encapsulating layer with reflective powder covers the solder bumps and Zener diode
Data Source
AI summary
There is provided a semiconductor light-emitting device which includes a light-emitting diode (LED) chip having a first plane on which first and second electrodes are disposed and a second plane disposed opposite to the first plane, first and second solder bumps disposed in bonding areas of the first and second electrodes, respectively, and a protective device electrically connected to the first and second electrodes and mounted on the first plane of the LED chip. The protective device has the substantially same thickness as each of the first and second solder bumps.