Light-Emitting Substrate Pad Structure for Oxidation-Resistant Bonding
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Solution Overview
Problem
The bonding process of Mini/Micro LEDs and circuit boards on light-emitting substrates faces challenges due to different temperature requirements, leading to oxidation of pad materials and poor electrical connections, which reduces product yield.
Innovation Solution
A light-emitting substrate design featuring first pads with a copper metal layer and second pads with a copper-nickel-titanium alloy, where the nickel and titanium content varies across the alloy's cross-sections to enhance oxidation resistance, and a molybdenum-niobium alloy for improved adhesion and conductivity, allowing for simultaneous bonding without oxidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper metal is used as wire material for Mini/Micro LED bonding, then conductivity is improved, but oxidation resistance deteriorates
Solution Approach 1:
The patent uses a composite metal layer structure consisting of copper layer, copper-nickel-titanium alloy layer, and nickel-titanium alloy layer. The copper layer provides high conductivity while the copper-nickel-titanium alloy layer and nickel-titanium alloy layer provide oxidation resistance, resolving the contradiction between conductivity and oxidation resistance.
Solution Approach 2:
Different layers of the metal structure have different compositions and properties: the copper layer near the LED contact point provides conductivity, while the outer copper-nickel-titanium alloy layer and nickel-titanium alloy layer provide oxidation resistance. Each layer performs its specific function locally.
2Manufacturing precision
If separate bonding processes are used for Mini/Micro LED and circuit board, then bonding quality is improved, but manufacturing complexity increases
Solution Approach 1:
The patent merges the LED bonding process and circuit board bonding process into a single simultaneous bonding step. The specially designed metal layer structure allows both bonding operations to occur at the same time under the same process conditions, eliminating the need for separate bonding processes while maintaining bonding quality.
Solution Approach 2:
The metal layer structure serves multiple functions: it provides electrical connection for LED bonding, provides oxidation resistance during the bonding process, and enables simultaneous circuit board bonding. This multi-functionality allows a single process to achieve multiple bonding objectives.
3Strength
If high temperature bonding is used for Mini/Micro LED, then bonding strength is improved, but oxidation of pad material increases
Solution Approach 1:
The copper-nickel-titanium alloy layer and nickel-titanium alloy layer act as intermediary protective layers between the copper layer and the oxidation environment. During high-temperature bonding, these intermediate layers prevent oxygen from reaching and oxidizing the copper pad material, allowing high-temperature bonding to proceed without oxidation damage.
Data Source
AI summary
Disclosed are a light-emitting substrate and a display device. In the light-emitting substrate, a first pad of a light-emitting area includes a first metal layer located above a base substrate and a second metal layer located on a side, facing away from the base substrate, of the first metal layer. A material of the second metal layer includes copper-nickel-titanium alloy, and a quantity of nickel atoms and/or titanium atoms contained per unit area in a cross section, farther from the base substrate, of the second metal layer is greater than a quantity of nickel atoms and/or titanium atoms contained per unit area in another cross section, closer to the base substrate, of the second metal layer.