Chip-Scale LED Package Layout to Block Solder Diffusion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Chip-scale package type light emitting diodes face challenges in preventing solder diffusion, which can contaminate the ohmic reflection layer and lead to device failure, due to their complex structure and the need for effective heat dissipation.
Innovation Solution
The design incorporates a substrate with a first and second conductivity type semiconductor layer, an active layer, an ohmic reflection layer, and insulation layers with strategically positioned openings to prevent solder diffusion, including a mesa structure with indent portions and bump pads to increase the solder's diffusion path and enhance current spreading.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a flip-chip shape electrode structure is used for heat dissipation, then heat dissipation characteristics are improved, but solder diffusion into the light emitting diode occurs causing contamination of the ohmic reflection layer
Solution Approach 1:
The electrode structure is divided into multiple segments: the first electrode, second electrode, third electrode, and fourth electrode arranged in a specific pattern. This segmentation creates isolated bonding regions that prevent solder from diffusing across the entire device while maintaining effective heat dissipation paths through each segment.
Solution Approach 2:
Different regions of the device are given different properties: the bonding pad regions have enhanced solder diffusion resistance through the specific electrode arrangement, while the mesa regions maintain optimal heat dissipation characteristics. The insulation layers are selectively positioned to provide local protection where needed.
2Reliability
If complex structures are added to prevent solder diffusion, then reliability is improved, but device complexity increases
Solution Approach 1:
The first and second insulation layers serve multiple functions simultaneously: they provide electrical insulation between different electrode regions, prevent solder diffusion paths, and maintain the structural integrity of the bonding pads. This multi-functionality reduces the need for additional dedicated components.
Solution Approach 2:
The insulation functions and electrode functions are merged into an integrated structure where the insulation layers are positioned between specific electrodes rather than as separate protective components. The bonding pad structure itself is designed to provide both electrical connection and solder diffusion resistance.
Data Source
AI summary
A chip-scale package type light emitting diode is provided. In the light emitting diode according to one embodiment, an opening exposing a pad metal layer is separated from an opening of a lower insulation layer which exposes an ohmic reflection layer formed on a mesa. Therefore, it is possible to prevent solder, particularly Sn, from diffusing and contaminating the ohmic reflection layer.