GaN LED Back Hole Structure Thermal Management
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Solution Overview
Problem
Conventional gallium nitride based LEDs with flip-chip structures face high thermal resistance due to poor heat conductivity, limiting their use in high-power general-purpose illumination applications.
Innovation Solution
The method involves replacing the silicon oxide insulation layer with copper, which has higher heat conductivity, allowing direct heat conduction from the active region to the heat sink, eliminating poor heat conductors in the path and reducing thermal resistance to near zero.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silicon oxide insulation layer is used in the heat conducting path, then electrical insulation is provided, but thermal resistance increases due to poor heat conductivity
Solution Approach 1:
The heat dissipation path is segmented into multiple parallel channels: one through the silicon substrate and another through the copper back hole. This segmentation allows the electrical insulation function to be maintained in the silicon oxide layer while providing an alternative high-conductivity thermal path through copper, thus resolving the contradiction between electrical insulation and thermal conduction.
Solution Approach 2:
Copper acts as an intermediary material in the back hole, bridging the heat transfer between the active region and the heat sink. The copper provides a high-conductivity thermal pathway that bypasses the poor thermal conduction of silicon oxide, while the silicon oxide layer maintains electrical insulation. This intermediary approach resolves the contradiction by introducing a material that excels in the required thermal function without compromising electrical insulation.
2Ease of manufacture
If conventional flip-chip bonding technique is used with silicon oxide insulation, then manufacturing process is simplified, but heat dissipation performance is insufficient for high power LEDs
Solution Approach 1:
The patent employs a composite structure combining silicon substrate, silicon oxide insulation layer, and copper back hole. This composite material approach leverages the electrical insulation properties of silicon oxide while utilizing copper's superior thermal conductivity for heat dissipation. The composite structure enables the LED to achieve high power heat dissipation capability without complicating the manufacturing process, as it builds upon the conventional flip-chip bonding technique.
3Temperature
If copper is introduced to replace silicon oxide in the heat conducting path, then thermal conductivity is improved, but manufacturing complexity increases
Solution Approach 1:
The copper back hole is formed preliminarily in the silicon substrate before the flip-chip bonding process. By preparing the copper heat dissipation structure in advance during substrate processing, the patent avoids adding complex steps to the already simplified conventional flip-chip bonding manufacturing process. This preliminary action allows the copper to be integrated seamlessly, improving thermal conductivity without significantly increasing manufacturing complexity.
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 approach enables LEDs to operate at higher currents and maintain continuous performance, enhancing reliability and facilitating the development of power LEDs for illumination by optimizing heat dissipation.
Implementation Method 1
the silicon is replaced by the copper, whose heat conductivity is almost 3 times of that of the silicon, thus enabling the heat produced in the active region of the LED die to be directly conducted to the heat sink through the metal
Data Source
AI summary
This invention relates to a method for manufacturing a GaN based LED of a back hole structure, and the method comprises: epitaxially growing an N type GaN layer, a multi-quantum wells emitting active region and a P type GaN layer in turn on an insulation substrate made of sapphire or other materials; etching the N type GaN layer by photoetching, and forming a P type ohmic contact electrode and an N type ohmic contact electrode; scribing the chip to divide the dies on the epitaxial chip into individual die; forming a SiO2 insulation isolation layer on both sides of the silicon chip, forming a metal electrode on a face side, and forming a back hole pattern on a back side; forming a back hole; forming a bump pattern for plating on the face side of the silicon chip by thick resist photoetching; forming a layer of alloy with low melting point on the back side of the silicon chip, thus forming a base; on the back side of the base, directly attaching the base to a heat sink of a housing; bonding the die with the face side of the base through the metal bumps, leading an N electrode of the LED from the metal electrode formed on the face surface of the silicon chip, and leading a P electrode of the LED from the back side of the heat sink of the housing.