Fiber-Held Photonic BGA Packaging for Solder Reflow
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Solution Overview
Problem
Conventional packaging techniques for photonic integrated circuits (PICs) are impractical when co-packaging with electrical circuitry, such as drivers and ASICs, especially when optical fibers are involved, as they can be damaged by high temperatures during solder reflow and pose challenges in close component spacing on printed circuit boards.
Innovation Solution
A packaging method that includes a substrate, a lid with a fiber holder, and an optical fiber mechanically coupled to the fiber holder, allowing the PIC to be co-packaged with electronic circuitry in a ball grid array package, where the fiber holder temporarily retains the optical fiber during solder reflow to prevent damage and interference with other components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If optical fiber is coupled to PIC for signal delivery, then optical signal transmission is enabled, but optical fiber can be damaged by high temperatures during solder reflow
Solution Approach 1:
The package is divided into separate functional components: a substrate for mounting the PIC and electronic circuitry, a lid with an opening for fiber access, and a retaining feature that secures the optical fiber. This segmentation allows the optical fiber to be isolated from the high-temperature solder reflow process while maintaining its functional connection to the PIC.
Solution Approach 2:
The lid acts as an intermediary structure that provides a protected pathway for the optical fiber. The retaining feature on the lid secures the fiber in place, creating a physical barrier that prevents the optical fiber from being exposed to harmful thermal conditions during soldering operations.
2Adaptability or versatility
If optical fiber is present during solder reflow, then PIC can be co-packaged with electronic circuitry, but optical fiber interferes with close component spacing on PCBs
Solution Approach 1:
The optical fiber is nested within the package structure by securing it to the lid's retaining feature. This nesting contains the fiber within the package footprint, allowing the PIC and electronic circuitry to be co-packaged in close proximity without the fiber interfering with component spacing on the PCB.
Solution Approach 2:
The optical fiber is routed through the vertical dimension by accessing the PIC through the lid opening rather than extending horizontally across the PCB. This dimensional change allows close component spacing on the PCB while maintaining optical fiber functionality.
3Ease of manufacture
If conventional packaging techniques are used for PICs, then simple packaging is achieved, but they are impractical when co-packaging with electrical circuitry and optical fibers
Solution Approach 1:
The lid serves multiple functions: it provides structural closure for the package, creates an opening for optical fiber access, and incorporates a retaining feature to secure the fiber. This multi-functionality enables conventional packaging techniques to be adapted for co-packaging PICs with electronic circuitry and optical fibers while maintaining manufacturing simplicity.
Data Source
AI summary
A photonic integrated circuit may be coupled to an optical fiber and packaged. The optical fiber may be supported by a fiber holder during a solder reflow process performed to mount the packaged photonic integrated circuit to a circuit board or other substrate. The optical fiber may be decoupled from the fiber holder, and the fiber holder removed, after completion of the solder reflow process.