Display Circuit Substrate Pads for Oxidation-Resistant LED Bonding
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Solution Overview
Problem
Copper pads on circuit substrates used to drive light emitting elements are prone to oxidation, leading to low intermetallic bonding yield and potential damage to the display device when a tungsten alloy is used as a protection layer, necessitating high energy bonding processes that can further damage the substrate.
Innovation Solution
A protection layer is applied to copper pads on circuit substrates, which can be removed before bonding to improve yield, and additional pads with protection layers are used to accommodate light emitting diodes, allowing for replacement if damaged.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a tungsten alloy protection layer is disposed on the copper pad, then the copper pad is protected from oxidation, but the intermetallic bonding yield between the copper pad and the light emitting element becomes low
Solution Approach 1:
The protection layer is divided into two distinct segments: a first protection layer (tungsten alloy) for oxidation protection, and a second protection layer (tin-based alloy) for bonding facilitation. This segmentation allows each layer to perform its specific function optimally without compromising the other.
Solution Approach 2:
The second protection layer acts as an intermediary between the copper pad and the light emitting element during bonding. It facilitates the bonding process by providing a bonding-friendly surface, while the first protection layer remains as a stable oxidation barrier underneath.
2Manufacturing precision
If energy of the bonding process is increased to improve bonding yield, then the bonding yield improves, but damage to the display device and circuit substrate increases
Solution Approach 1:
The invention changes the material parameter of the protection layer from a single tungsten alloy to a composite structure with a tin-based second protection layer. This material parameter change enables bonding at lower energy levels while maintaining high bonding yield, thus avoiding damage to the display device and circuit substrate.
3Use of energy by stationary object
If the copper pad is exposed without protection, then bonding process energy can be reduced, but the copper pad oxidizes and bonding yield becomes low
Solution Approach 1:
The second protection layer is preliminarily disposed on the copper pad before the bonding process. This preliminary action provides a bonding-friendly surface that enables low-energy bonding, while the first protection layer preliminarily protects the copper pad from oxidation throughout the manufacturing process.
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 protection layers prevent oxidation and enhance bonding yield, enabling efficient assembly and replacement of light emitting diodes without damaging the circuit substrate.
Implementation Method 1
The copper pads are prone to oxidation. In some conventional technologies, a tungsten alloy is disposed on the copper pad as a protection layer.
Data Source
AI summary
A circuit substrate including multiple display units is provided. Each of the display units includes at least one first sub-unit and at least one second sub-unit. Each of the first sub-units includes at least one first pad, and each of the second sub-units includes at least one second pad. A first protection layer is disposed on the first pad. The first protection layer and a second protection layer are disposed on the second pad. The first protection layer is disposed between the second pad and the second protection layer. There is a space suitable for accommodating a light emitting diode above the first pad and the second pad respectively. A display device is also provided.