Backlight Unit Wiring Stack for Stronger LED Bonding
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Solution Overview
Problem
The existing display devices face issues with weakened bonding strength between semiconductor light emitting devices and metal wiring on substrates, particularly due to uneven solder distribution and thickness of metal wiring, leading to potential disconnection during the surface mount technology process.
Innovation Solution
A backlight unit design featuring a substrate with alternating pairs of metal layers of different conductivities, where a conductive bonding layer fills defined holes to securely connect semiconductor light emitting devices to the second metal wiring layer, preventing diffusion and ensuring strong electrical connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a metal wiring layer without Cu is used for SMT process, then the bonding strength between substrate and LED chip is improved, but the solder material is not evenly spread on the metal surface
Solution Approach 1:
The patent employs a composite metal wiring layer structure consisting of multiple metal layers with different compositions and functions. The first metal layer (Cu-free) provides strong bonding with LED chips, while the second metal layer (Cu-containing) ensures uniform solder spread. This composite structure resolves the contradiction by combining the advantages of different materials to achieve both strong bonding and uniform solder distribution.
Solution Approach 2:
The metal wiring layer is segmented into multiple distinct layers, each performing a specific function. The first metal layer is dedicated to bonding with the LED chip, while the second metal layer is dedicated to soldering. This segmentation allows each layer to be optimized for its specific purpose, resolving the conflict between bonding strength and solder uniformity.
2Strength
If the metal wiring layer thickness is increased to improve bonding strength, then the bonding strength between substrate and LED chip is improved, but the overall device thickness increases
Solution Approach 1:
Instead of using a single thick metal layer, the patent uses a composite structure of multiple thinner layers. The first metal layer (200-700 nm) provides bonding strength, while the second metal layer (10-200 nm) provides solderability. This composite approach achieves the required bonding strength without increasing the overall thickness, as each layer is thin but collectively they provide both functionality and strength.
Solution Approach 2:
The solution transitions from a single-dimensional (one thick layer) to a multi-dimensional (multiple thin layers stacked) structure. By stacking multiple thin layers with different functions, the patent achieves both bonding strength and thin profile, resolving the contradiction between strength and thickness.
3Ease of manufacture
If a single metal layer is used in the second metal wiring layer, then the manufacturing process is simplified, but the conductivity and bonding performance are insufficient
Solution Approach 1:
The second metal wiring layer uses a composite structure of multiple metal layers with different conductivities. The first metal layer provides a base level of conductivity and bonding, while the second metal layer with higher conductivity enhances the overall electrical performance. This composite structure improves reliability without significantly complicating the manufacturing process, as the layers can be deposited using standard sequential deposition techniques.
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 solution enhances the bonding strength between the semiconductor light emitting devices and the substrate, reduces the risk of metal wiring disconnection, and simplifies the manufacturing process by eliminating the need for thin film transistors, thereby lowering manufacturing costs and improving efficiency.
Implementation Method 1
the first metal layer blocks diffusion of the second metal layer
Implementation Method 2
a conductive bonding layer disposed on the second metal wiring layer so as to fill the hole; and a semiconductor light emitting device electrically connected to the second metal wiring layer by the conductive bonding layer
Data Source
AI summary
A display device according to embodiments of the present invention comprises: a substrate; a plurality of first metal wiring layers formed on the substrate; a first insulating layer stacked on the substrate to cover the first metal wiring; a second metal wiring layer stacked on at least a portion of the first insulating layer so as to be spaced apart therefrom; and a second insulating layer stacked on the second metal wiring. The second metal wiring layer comprises: at least one first metal layer having a first conductivity; and at least one second metal layer having a higher conductivity than the first metal layer, wherein the first metal layer may block diffusion of the second metal layer.