Flip Chip Bonding Recess Conductive Layer Thermal Management
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Solution Overview
Problem
Conventional flip chip bonding processes for hybrid photonic integrated circuits are complex, leading to alignment issues and hindered heat dissipation due to oxide layers with limited visibility and thermal conductivity.
Innovation Solution
A hybrid photonic integrated circuit design featuring a main PIC with a recess containing a conductive layer extending from the bottom, allowing for easier alignment and connection of a secondary device, along with a redistribution layer for improved thermal conductivity and simplified assembly and testing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional flip chip bonding process is used with recess and mating connectors, then electrical connection is achieved, but device complexity and alignment difficulty increase
Solution Approach 1:
The patent extracts the electrical connection function from the complex mating connector system and implements it through a simple conductive layer extending from the recess bottom. This eliminates the need for complex first and second electrical connectors while maintaining reliable electrical connection between the main PIC and secondary chip.
Solution Approach 2:
Instead of bringing connectors together from opposite sides (conventional approach), the patent inverts the approach by having the conductive layer extend outward from the recess bottom to meet the pad on the secondary chip. This simplifies the connection geometry and eliminates alignment difficulties associated with mating connectors within the recess.
2Strength
If oxide layers are present in the PIC, then structural integrity is maintained, but thermal conductivity deteriorates
Solution Approach 1:
The patent applies local quality by removing oxide layers specifically from the recess bottom area where thermal contact is needed, while maintaining oxide layers in other structural areas of the PIC. This localized modification improves thermal conductivity at the critical heat dissipation interface without compromising overall structural integrity.
Solution Approach 2:
The patent performs preliminary removal of oxide layers from the recess bottom before mounting the secondary chip. This preliminary action ensures optimal thermal contact is established in advance, preventing heat dissipation issues that would arise from oxide layer interference during operation.
3Manufacturing precision
If recess structure is used for mounting, then alignment is achieved, but manufacturing complexity increases
Solution Approach 1:
The patent segments the alignment function from the mounting structure by incorporating alignment features (such as protrusions or notches) that are separate from the main recess geometry. This segmentation allows the recess to provide mechanical support while dedicated alignment features guide precise positioning, simplifying the overall manufacturing process.
Solution Approach 2:
The patent incorporates alignment features during the recess formation process itself, rather than adding them separately. This preliminary integration of alignment functionality into the recess structure reduces manufacturing steps and simplifies assembly while maintaining precise alignment capabilities.
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
Simplifies the electrical connection process, enhances thermal conductivity by removing oxide layers, and facilitates easier testing and assembly of the hybrid photonic integrated circuit.
Implementation Method 1
heat dissipation from the gain medium is hampered by oxide layers in the PIC, which do not provide high thermal conductivity
Implementation Method 2
a conductive layer extending from the first electrode along the bottom of the recess out from underneath the secondary device and electrically connected to the electrical connector
Data Source
AI summary
Conventional hybrid photonic integrated circuits (PIC) combine one type of semiconductor platform for the main PIC, and a different type of semiconductor platform for a secondary chip. Conventional mounting processes include forming a recess in the main PIC, and mating electrical connectors from the secondary chip and the main PIC within the recess. Mating the first and second electrical connectors in the recess increases the complexity of forming the main PIC, and hampers heat dissipation from secondary chip through oxide layers in the main PIC. Providing a conductive, e.g. redistribution, layer from the first electrode along the bottom and sides of the recess eliminates the complexity in forming the main PIC, and enables the first electrical connector to be mounted directly onto a more thermally conductive substrate material.