LED Pad Electrode Grooves for Solder Diffusion Control
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Solution Overview
Problem
Light emitting diodes (LEDs) face issues with solder diffusion into semiconductor layers, causing electrical failure, and light absorption by solder, which deteriorates luminous efficacy, complicating the manufacturing process and reducing device reliability.
Innovation Solution
A light emitting device design featuring pad electrodes with grooves on their surfaces to contain solder, preventing it from flowing along side surfaces and improving adhesion, while also minimizing light absorption by ensuring sufficient space between solder and electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solder is used to bond pad electrodes to connection pads, then electrical connection is achieved, but solder diffuses into semiconductor layers causing electrical failure
Solution Approach 1:
The pad electrode surface is segmented by forming grooves that divide the surface into multiple regions. This segmentation contains the solder within specific zones defined by the grooves, preventing it from flowing onto and diffusing into the semiconductor layers while maintaining effective electrical connection between the pad electrode and connection pad.
Solution Approach 2:
The groove structure creates local quality differences on the pad electrode surface. The grooved regions provide specific containment zones for solder, while other regions maintain different properties. This localized structural modification enables selective control over solder placement without affecting the overall electrical connection function.
2Reliability
If solder is used to bond pad electrodes to connection pads, then electrical connection is achieved, but solder absorbs light from side surfaces of semiconductor layers deteriorating luminous efficacy
Solution Approach 1:
The groove structure segments the pad electrode surface to create defined containment zones. This segmentation strategically positions solder away from the light emission path of the semiconductor layers' side surfaces, reducing light absorption by solder while preserving the electrical connection function.
3Object-affected harmful factors
If anti-diffusion layer is formed on side surface of LED chip to prevent solder diffusion, then solder diffusion is prevented, but manufacturing process becomes complicated
Solution Approach 1:
Instead of adding an anti-diffusion layer on the semiconductor chip side to prevent solder diffusion, the invention inverts the approach by creating grooves on the pad electrode surface. This inverted strategy contains solder at the source before it can reach the semiconductor layers, achieving the same protective function while simplifying the manufacturing process.
4Strength
If solder amount is increased to improve adhesion of pad electrodes, then adhesion is improved, but solder flows along side surfaces of LED chip increasing diffusion risk
Solution Approach 1:
The groove structure segments the pad electrode surface into containment zones. This segmentation allows increased solder quantity to be accommodated within the grooved regions, improving adhesion strength while the groove walls physically constrain solder flow and prevent it from reaching the side surfaces of the LED chip.
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 effectively prevents solder diffusion into the LED structure, enhancing the reliability and luminous efficacy of the light emitting device by maintaining the solder within the grooves and reducing light absorption.
Implementation Method 1
At least part of the solder may be disposed in the groove. In this structure, since the groove is filled with a portion of the solder, it is possible to prevent the solder from flowing along a side surface of a light emitting structure
Implementation Method 2
solder interposed between the first pad electrode and the first connection pad and between the second pad electrode and the second connection pad
Data Source
AI summary
A high-efficiency light-emitting device of the present invention includes: a nitride-based semiconductor laminate layer comprising a first conductive-type semiconductor layer, an active layer, and a second conductive-type semiconductor layer; a substrate comprising a first electrode and a second electrode each connected to the first conductive-type semiconductor layer and the second conductive-type semiconductor layer, a first pad electrode and a second pad electrode each connected with the first electrode and the second electrode, and a first connection pad and a second connection pad each connected with the first pad electrode and the second pad electrode; and a solder positioned between the pad electrodes and the connection pads.