LED Mounting Substrate Planarization for Sulfurization Resistance
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Solution Overview
Problem
Conventional substrates for mounting LED elements, particularly those made of inorganic insulating materials, face issues with sulfurization resistance due to surface irregularities and grain boundary voids in thick conductor layers, leading to color changes during sulfurization tests, and existing solutions like increasing Au layer thickness or using small Ag powder particles are costly or result in substrate warpage.
Innovation Solution
A substrate with a planarized thick conductor layer surface, achieved through wet blast treatment with a ceramics powder abrasive, ensuring a surface roughness of at most 0.02 μm, followed by a Ni/Au plating process to enhance sulfurization resistance without exposing the Ni layer and prevent nickel sulfide formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional Ni/Au plating is applied with standard thicknesses, then production cost is controlled, but sulfurization resistance is insufficient and color change occurs during sulfurization tests
Solution Approach 1:
The patent applies preliminary planarization treatment to the thick conductor layer surface before plating. By performing surface planarization (reducing surface roughness Ra to 0.03 μm or less) prior to Ni/Au plating, the substrate achieves complete coverage by the plating layer, preventing sulfurization of exposed Ni regions without increasing plating thickness, thus resolving the contradiction between sulfurization resistance and production cost
2Reliability
If Au layer thickness is increased to prevent sulfurization, then sulfurization resistance is improved, but production cost increases significantly
Solution Approach 1:
The patent performs surface planarization treatment before plating to eliminate surface irregularities and exposed Ni regions. This preliminary action ensures that the subsequent Ni/Au plating layer achieves complete coverage, preventing sulfurization without requiring excessive Au thickness, thereby resolving the contradiction between sulfurization resistance and material quantity
3Reliability
If small Ag powder particles are used to improve sintering property and reduce grain boundaries, then sulfurization resistance is improved, but substrate warpage occurs
Solution Approach 1:
The patent introduces surface planarization treatment as an intermediary process between thick conductor layer formation and plating. This intermediary treatment addresses the root cause of sulfurization (surface irregularities and exposed Ni) without requiring changes to Ag powder particle size, thus preventing both sulfurization and substrate warpage
4Ease of manufacture
If thick conductor layer is formed by printing paste, then manufacturing is simplified, but surface irregularities and grain boundary voids remain causing sulfurization
Solution Approach 1:
The patent applies preliminary planarization treatment to the thick conductor layer surface before plating. This preliminary action removes surface irregularities and fills grain boundary voids, enabling complete coverage by the subsequent Ni/Au plating layer and preventing sulfurization while maintaining the simplicity of paste printing manufacturing
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
The process effectively improves sulfurization resistance by completely covering the thick conductor layer with a Ni/Au layer, preventing color changes in sulfurization tests and maintaining substrate planarity, thus enhancing the reliability of LED element mounting substrates.
Implementation Method 1
the thick conductor layer has its surface planarized by wet blast treatment
Implementation Method 2
terminal portions (electrodes) to be connected to the element are subjected to lamination plating (Ni/Au plating) of nickel (Ni) plating and gold (Au) plating
Data Source
AI summary
A process for producing a substrate for mounting element includes forming a thick conductor layer-provided substrate having a thick conductor layer made of a metal composed mainly of silver (Ag) or copper (Cu), on a surface of an inorganic insulating substrate made of an inorganic insulating material, applying wet blast treatment to the thick conductor layer to planarize the surface of the thick conductor layer to a surface roughness Ra of at most 0.02 μm, and forming a nickel (Ni)/gold (Au)-plated layer on the thick conductor layer having the surface planarized by the wet blast treatment.