Back-Side Emitting VCSEL Stacked Assembly for Parasitic Inductance Reduction
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Solution Overview
Problem
Conventional optoelectronic assemblies with top-emitting VCSELs face limitations due to parasitic elements, cross-talk, and electromagnetic interference, which restrict high-speed operations and increase manufacturing complexity and costs, especially in applications like 3D imaging and LIDAR that require precise control of laser pulses.
Innovation Solution
The optoelectronic assembly features a stacked configuration with a back-side emitting VCSEL and a laser driver circuit on a printed circuit board, eliminating wire bonds and using conductive pillars or Direct Bond Interconnects for electrical connections, thereby minimizing parasitic inductance and allowing higher frequency control of the VCSELs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wire bonds are used to connect the VCSEL to the driver circuit, then electrical connection is established, but parasitic inductance and capacitance increase, limiting the frequency response
Solution Approach 1:
The patent removes wire bonds from the system entirely, replacing them with direct flip-chip bonding between the VCSEL and driver circuit. This extraction of the problematic wire bond interconnect eliminates the associated parasitic inductance and capacitance while maintaining electrical connectivity through direct metallurgical bonding.
Solution Approach 2:
The patent transitions from a planar layout with wire bonds extending in three-dimensional space to a stacked three-dimensional integration architecture. The VCSEL is flip-chip bonded directly onto the driver circuit substrate, creating vertical interconnections that eliminate the long wire bond loops and reduce parasitic elements through spatial reorganization.
2Ease of manufacture
If wire bonds are used for electrical connection, then the VCSEL can be connected to the driver circuit, but the wire bond length and loop height increase parasitic inductance, increasing rise and fall times
Solution Approach 1:
The patent extracts and eliminates wire bonds from the interconnection architecture, replacing them with direct flip-chip bonding. This removal of the wire bond medium directly reduces the electrical path length and loop height, thereby minimizing parasitic inductance and reducing laser pulse rise and fall times.
Solution Approach 2:
The patent replaces the mechanical wire bond system with a direct metallurgical bonding system through flip-chip technology. This substitution eliminates the flexible but parasitic wire bond mechanism in favor of a rigid, direct electrical connection that provides both mechanical stability and electrical performance.
3Reliability
If conventional top-emitting VCSEL configuration is used with wire bonds, then electrical connection is achieved, but cross-talk and electromagnetic interference increase
Solution Approach 1:
The patent adopts a three-dimensional stacked architecture where the VCSEL is flip-chip bonded directly to the driver circuit, positioning the optical emitter in vertical proximity to the driver electronics. This spatial reorganization reduces the lateral separation between signal paths and optical emissions, minimizing cross-talk and electromagnetic interference through improved geometric shielding and reduced loop area.
4Reliability
If top-emitting VCSEL is used with wire bonds, then electrical connection is established, but manufacturing complexity and costs increase
Solution Approach 1:
The patent removes wire bonds and associated bond pads from the top surface of the VCSEL, simplifying the manufacturing process. The flip-chip bonding approach eliminates the need for top-surface electrical connections, reducing the number of interconnection elements and simplifying assembly procedures while maintaining reliable electrical connectivity through the substrate mounting process.
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 configuration enhances the optical-electrical bandwidth, reduces rise and fall times, and improves thermal management, enabling faster and more precise control of laser pulses, suitable for high-power and high-frequency applications like 3D sensing and LIDAR, while simplifying manufacturing and reducing costs.
Implementation Method 1
An optical emitter (sometimes referred to as an electro-optic transducer, or laser) such as a Vertical Cavity Surface Emitting Laser (VCSEL) emits light when electrical current, sometimes referred to as 'drive current,' is passed through the device.
Implementation Method 2
The optoelectronic assembly features a stacked configuration with a back-side emitting VCSEL and a laser driver circuit on a printed circuit board, eliminating wire bonds and using conductive pillars or Direct Bond Interconnects for electrical connections
Data Source
AI summary
An optoelectronic assembly is disclosed. The disclosed assembly includes one or more lasers formed on a first substrate, and a programmable driver circuit formed on a second substrate configured as an integrated circuit. The first and second substrates are mounted on a third substrate in a stacked arrangement.