Flip-Chip LED Structure Eliminating Bonding Wire Breakage
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Solution Overview
Problem
Vertical LED apparatuses face issues such as breakage due to differences in expansion coefficients between bonding wires and sealants, uneven phosphor distribution, and limited chip density, which hinder enhanced luminous intensity per unit area for projection-type light sources.
Innovation Solution
The LED design incorporates a semiconductor stacked structure with a flip-chip bonding method, eliminating the need for bonding wires by directly connecting electrodes to a conductive substrate, and includes a protection layer and island structures to prevent phosphor unevenness and enhance heat dissipation, allowing for increased chip density and luminous intensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bonding wire is used to electrically connect LED chip to carrier board, then electrical connection is achieved, but breakage easily occurs due to difference in expansion coefficient between bonding wire and sealant
Solution Approach 1:
The patent removes the bonding wire from the LED structure, replacing it with a direct flip-chip bonding connection between the LED chip electrodes and the carrier board conductive layers. This extraction of the bonding wire eliminates the expansion coefficient mismatch problem that caused breakage, while maintaining electrical connection functionality through the direct solder bump connection.
Solution Approach 2:
Instead of using bonding wire to connect the LED chip to the carrier board, the patent inverts the connection approach by having the LED chip electrodes directly contact the carrier board conductive layers through solder bumps. This inversion eliminates the intermediate bonding wire component that was causing reliability issues due to thermal expansion differences.
2Reliability
If bonding wire and LED chip thickness are excessively large, then electrical connection is ensured, but uneven distribution of phosphor in the sealant occurs due to natural deposition
Solution Approach 1:
The patent removes the bonding wire component entirely, replacing it with a direct flip-chip bonding structure where the LED chip is mounted face-down on the carrier board. This extraction eliminates the excessive thickness issue that caused phosphor deposition problems, allowing for more uniform phosphor distribution in the sealant while maintaining reliable electrical connection through the solder bumps.
3Reliability
If LED chip is electrically connected to carrier board through bonding wire, then electrical connection is achieved, but density of LED chips cannot be further decreased
Solution Approach 1:
The patent eliminates the bonding wire from the connection structure, replacing it with a direct flip-chip bonding approach where solder bumps on the LED chip electrodes directly contact the carrier board conductive layers. This removal of the intermediate bonding wire component reduces the overall space required for connection, enabling higher chip density while maintaining reliable electrical connection.
Solution Approach 2:
The patent transitions from a wire-based connection (occupying three-dimensional space) to a planar flip-chip connection where electrodes contact the carrier board directly in the same plane. This dimensional change from vertical wire routing to planar contact reduces space requirements and enables higher chip density.
4Temperature
If conventional vertical LED apparatus structure is used, then heat dissipation is improved compared to face-up LED, but breakage occurs due to expansion coefficient difference between bonding wire and sealant
Solution Approach 1:
The patent removes the bonding wire from the vertical LED structure, replacing it with a direct flip-chip bonding connection. This extraction eliminates the expansion coefficient mismatch between bonding wire and sealant that caused breakage, while preserving the vertical mounting configuration that provides effective heat dissipation from the LED chip to the carrier board.
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 design improves device reliability by preventing breakage and uneven phosphor distribution, enabling higher chip density and enhanced luminous intensity without additional insulating layers, thus addressing the limitations of conventional vertical LED apparatuses.
Implementation Method 1
A light emitting diode (LED) is a semiconductor device constituted mainly by group III-V compound semiconductor materials. Since such semiconductor materials have a characteristic of converting electricity into light, when a current is applied to the semiconductor materials, electrons and holes therein would be combined and release excessive energy in a form of light
Data Source
AI summary
A light emitting diode includes a semiconductor stacked structure, a substrate, a first electrode, a second electrode and a third electrode. The semiconductor stacked structure includes a first semiconductor layer, a second semiconductor layer and a light emitting layer. The first semiconductor layer has a first surface and a second surface opposite to each other and has a first region and a second region. The second semiconductor layer is disposed on the second surface. The light emitting layer is disposed between the first semiconductor layer and the second semiconductor layer. The substrate has a first conductive layer and a second conductive layer thereon. The first electrode is disposed between the second semiconductor layer and the first conductive layer. The second electrode is disposed on the first surface. The third electrode is disposed between the second region and the second conductive layer, and electrically connected to the second electrode.