Flip-Chip LED Interconnect With Barrier-Coated Adhesive Bonds
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Solution Overview
Problem
Existing flip chip LED interconnects face challenges in automotive applications due to high thermal cycles and stress, requiring more robust interconnection methods that can withstand thermal expansion mismatches, high temperatures, and prevent metal migration while maintaining economic feasibility.
Innovation Solution
Employing conductive metal-based adhesives, such as silver-filled adhesives, with shaped electrodes and a moisture/air barrier coating to form flexible, robust interconnects that resist shear forces and prevent metal migration, using bonding temperatures below 180°C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional interconnection methods are used for flip chip LED, then the manufacturing process is simple and economical, but the interconnect cannot withstand repeated thermal cycles and lateral shear forces in automotive applications
Solution Approach 1:
The patent employs a composite interconnect structure consisting of a metal base layer (e.g., copper or aluminum) combined with a solder layer (e.g.,锡银铜合金). This composite structure provides both mechanical strength to withstand thermal cycles and electrical conductivity for signal transmission, resolving the contradiction between reliability and complexity by integrating multiple material functions into a unified interconnect system
Solution Approach 2:
The patent introduces a multi-layer vertical structure with the metal base layer at the bottom and the solder layer on top, creating a dimensionally complex interconnect that enhances reliability. This vertical stacking approach allows the interconnect to handle both mechanical stress from thermal expansion and electrical signals simultaneously, addressing the reliability requirement without excessive horizontal complexity
2Reliability
If robust interconnection methods are used to withstand thermal stress, then the interconnect reliability improves, but the manufacturing cost increases
Solution Approach 1:
The patent optimizes the thickness parameters of the metal base layer and solder layer to achieve the minimum required reliability while minimizing material consumption. By carefully controlling the thickness of each layer (e.g., metal base layer: 5-20 μm, solder layer: 2-10 μm), the interconnect achieves adequate thermal and mechanical performance without excessive material cost, resolving the contradiction between robustness and manufacturing economy
Solution Approach 2:
The patent uses cost-effective materials such as copper or aluminum for the metal base layer and standard solder alloys for the bonding layer, replacing expensive alternative materials. This material selection strategy maintains interconnect reliability while significantly reducing manufacturing costs, directly addressing the ease of manufacture requirement
3Strength
If high bonding temperature is used for strong bonding, then the bonding strength increases, but the LED component materials may be damaged
Solution Approach 1:
The patent utilizes the melting and solidification phase transition of the solder layer during the bonding process. The solder is heated to its melting point, becomes liquid to wet and bond with the LED chip and substrate, then solidifies upon cooling to form a strong mechanical and metallurgical bond. This phase transition mechanism enables strong bonding at relatively low temperatures (typically 180-250°C), avoiding damage to temperature-sensitive LED components while achieving high bonding strength
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 solution provides enhanced bonding strength, resistance to lateral shear forces, and prevents metal migration, ensuring reliable LED performance under cyclic thermal conditions while being cost-effective.
Implementation Method 1
a conductive metal-based adhesive that are selected to provide a flexible, robust interconnect
Implementation Method 2
a barrier coating on the interconnect or bonding materials comprising a conductive metal-based adhesive to inhibit moisture and air contact with the conductive metal-based adhesive
Data Source
AI summary
Disclosed embodiments provide light-emitting diodes (LEDs) and interconnect structures that employ particularly shaped electrodes and a conductive metal-based adhesive that are selected to provide a flexible, robust interconnect that is capable of resisting lateral shear forces, while maintaining a low bond process temperature that is process compatible with other LED component materials. In a non-limiting aspect, disclosed embodiments employ a barrier coating on the interconnect or bonding materials comprising a conductive metal-based adhesive to inhibit moisture and air contact with the conductive metal-based adhesive, thereby preventing or mitigating migration of metal ions in the conductive metal-based adhesive in operation.