Cryogenic Chip-on-Chip Thermal Isolation for Photonic Dies
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Solution Overview
Problem
Existing cryogenic photonic and electronic chip assemblies face challenges in maintaining thermal isolation between temperature-sensitive components, as heat generated by electronic components can cause malfunction in cryogenic environments.
Innovation Solution
Incorporating a cavity and underfill material with lower thermal conductivity than the chip materials, along with blocking features, to create thermally isolated regions and reduce heat flux between photonic and electronic dies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If electronic die is bonded directly to photonic die, then mechanical stability and electrical connection are improved, but thermal isolation deteriorates due to heat generation from electronic components
Solution Approach 1:
A cavity is introduced as an intermediary structure between the electronic die and photonic die. This cavity acts as a thermal barrier that interrupts direct heat conduction paths while allowing the two dies to remain mechanically connected through bonding structures. The cavity reduces thermal coupling between the heat-generating electronic components and the temperature-sensitive photonic components.
Solution Approach 2:
An underfill material with specific thermal properties is used to fill portions of the cavity between the electronic die and photonic die. This underfill material creates a composite structure that provides both mechanical support and controlled thermal isolation, combining structural integrity with thermal management functionality.
2Object-affected harmful factors
If cavity is introduced for thermal isolation, then heat flux to photonic die is reduced, but mechanical stability deteriorates due to reduced bonding area
Solution Approach 1:
The cavity is designed with specific local characteristics including strategic positioning, controlled size, and selective placement to optimize thermal isolation in critical areas while preserving mechanical strength in load-bearing regions. The cavity is positioned to interrupt thermal paths from heat-generating regions to temperature-sensitive regions, while bonding structures are placed in locations that maintain structural integrity.
Solution Approach 2:
The underfill material fills portions of the cavity to provide both mechanical support and thermal management. This creates a composite structure where the combination of cavity space and underfill material achieves both thermal isolation and mechanical stability that neither feature could achieve alone.
3Strength
If underfill material is used to fill cavity, then mechanical support is improved, but thermal isolation deteriorates due to potential heat conduction through underfill
Solution Approach 1:
The underfill material is specifically selected and engineered to have low thermal conductivity, changing the thermal parameters of the assembly. By choosing materials with appropriate thermal properties, the underfill provides mechanical support while minimizing thermal conduction, thus maintaining thermal isolation between the electronic die and photonic die.
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
Enhances thermal isolation and mechanical stability, reducing heat flux to temperature-sensitive components, optimizing operation in cryogenic conditions.
Implementation Method 1
at least one of a cavity and an underfill material having a lower thermal conductivity than materials of the photonic die and the electronic die located between the photonic die and the electronic die
Data Source
AI summary
A hybrid electronic-photonic package includes a photonic die containing photonic components, an electronic die bonded to the photonic die, and at least one of a cavity and an underfill material having a lower thermal conductivity than materials of the photonic die and the electronic die located between the photonic die and the electronic die.