Wafer-Level Metal Pillars for LED Submount Elimination
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Solution Overview
Problem
Conventional light emitting devices require submounts for support and electrical connections, limiting wafer-scale processing and increasing complexity, and the singulation process is hindered by structural support, making it difficult to slice and mount individual dies accurately.
Innovation Solution
Forming thick metal pillars on light emitting dies while still on the wafer, embedding them in a molding compound to provide both structural support and electrical contact, eliminating the need for submounts and simplifying the singulation process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional submount structures are used to support light emitting devices, then structural support and electrical connections are provided, but device complexity increases and wafer-scale processing is limited
Solution Approach 1:
The patent combines the structural support function and electrical connection function into a single integrated metal pillar structure. The metal pillars serve dual purposes: providing mechanical support for the light emitting devices and establishing electrical connections between devices and the substrate, thereby eliminating the need for separate submount structures and reducing overall device complexity.
Solution Approach 2:
The metal pillars are designed to perform multiple functions simultaneously: they provide structural support, establish electrical connections, and enable wafer-scale processing. This multi-functional design allows the same structure to fulfill several roles that traditionally required separate components, simplifying the overall device architecture.
2Reliability
If submount structures provide structural support, then light emitting devices are supported, but singulation becomes difficult due to the need to cut through rigid support structures
Solution Approach 1:
The patent segments the support structure into discrete metal pillars rather than using a continuous rigid submount. This segmentation allows the slicing apparatus to navigate between pillars during singulation, making the cutting process easier and more precise while still maintaining adequate structural support through the distributed pillar arrangement.
3Productivity
If multiple processing operations are performed on dies while on the wafer, then productivity increases, but the processes are limited by the need for subsequent submount mounting
Solution Approach 1:
The patent implements preliminary actions by forming the metal pillars and establishing electrical connections while the devices are still on the wafer in an integrated structure. This allows subsequent processing operations to be performed on the wafer scale without concern for later submount mounting, thereby increasing productivity and process flexibility.
Data Source
Figure 1A~1C
Figure 2A
Figure 2B~2C
AI summary
Thick metal pillars are formed upon light emitting dies while the dies are still on their supporting wafer. A molding compound is applied to fill the space between the pillars on each die, and contact pads are formed atop the pillars. The metal pillars provide electrical contact between the contact pads and the electrical contacts of each light emitting die. The metal pillars maybe formed upon an upper metal layer of each die, and this upper metal layer maybe patterned to provide connections to individual elements within the die.