Fiber Mounting Unit for Edge-Coupler Alignment in 3D Optical Packages
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Solution Overview
Problem
The transition to 3D structures in chip packages with photonic integrated circuits (PIC) and electrical integrated circuits (EIC) poses challenges in thermal management and precise alignment of optical fibers with edge couplers, leading to increased heat dissipation issues and misalignment sensitivity.
Innovation Solution
A fiber mounting unit (FMU) is used to align optical fibers with edge couplers in the PIC die, with features like trenches and V-shaped grooves for precise positioning, and is integrated with a heat spreader to manage thermal issues, allowing for both 2.5D and 3D configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If optical fibers are aligned with edge couplers in 3D stacked chip packages, then coupling efficiency is improved, but misalignment sensitivity increases due to vertical stacking geometry
Solution Approach 1:
A fiber mounting unit (FMU) is introduced as an intermediary component between the optical fiber and the photonic integrated circuit die. The FMU includes a cavity that receives and positions the optical fiber, and an extension structure that interfaces with the edge coupler, thereby mediating the alignment relationship and reducing direct misalignment sensitivity
Solution Approach 2:
The alignment problem is solved by transitioning from direct lateral alignment to vertical stacking alignment. The FMU extends vertically from the PIC die surface, allowing optical fibers to be positioned in the vertical dimension while maintaining horizontal alignment through the extension structure, thus changing the alignment dimensionality
2Volume of moving object
If vertical stacking of substrates is implemented to reduce form factor, then device density is improved, but thermal management difficulty increases
Solution Approach 1:
The fiber mounting unit is merged with the heat spreader structure, combining the optical alignment function and thermal management function into a single integrated component. The FMU extension structure serves both to align the optical fiber and to conduct heat away from the photonic integrated circuit die
Solution Approach 2:
The fiber mounting unit is designed to perform multiple functions simultaneously: it provides optical fiber positioning, maintains alignment with the edge coupler, and acts as a thermal conduction path through its integration with the heat spreader, thereby achieving multi-functionality in a compact structure
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 FMU ensures precise alignment and efficient heat dissipation, reducing misalignment sensitivity and improving coupling efficiency while facilitating thermal management in high-performance chip packages.
Implementation Method 1
integrated with a heat spreader to manage thermal issues
Data Source
AI summary
An optical engine (OE) and a fiber mounting unit (FMU) are mounted side-by-side on a package substrate in a chip package. The OE includes an electrical integrated circuit (EIC) die and a photonic integrated circuit (PIC) die in a vertical stack. A core of an optical fiber may be passed through the FMU and maintained by the FMU in alignment with an edge coupler within the PIC die. The optical fiber may be separately supported by a fixture that is co-mounted with the chip package on a printed circuit board (PCB). A heat spreader may be placed over the chip package. Vertical stacking in the OE reduces electrical loses between the EIC and the PIC. Use of an edge coupler rather than a grating coupler leaves room for the heat spreader. The FMU enables precision alignment of the optical fiber to the edge coupler.