Superconducting Through-Electrode Structure for Reflow Stress Control

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Superconducting devices experience significant stress due to volume fluctuation and cracks caused by temperature changes during the reflow process, particularly when integrating through electrodes and junction electrodes with large volume differences.

Innovation Solution

The superconducting device incorporates a through electrode with a high melting point metal outer portion and a low melting point metal inner portion, separated by a high melting point metal cap and base films, which act as partition walls to minimize stress and volume fluctuation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a through electrode and junction electrode are integrated into a single structure, then device complexity is reduced, but stress and volume fluctuation increase significantly during temperature changes

Engineering Contradiction:

Improveelectrode structure complexityVSAvoidstress in through electrode and junction electrode

Core Design Contradiction:

Device complexityVSStress or pressure

Solution Approach 1:

The electrode structure is divided into separate through electrode and junction electrode components, allowing independent stress management for each component during temperature changes, thereby reducing overall stress while maintaining structural integrity

Inventive Principle:

Principle #1Segmentation

2Ease of manufacture

If through electrode and junction electrode are made from the same material, then manufacturing is simplified, but volume fluctuation and stress increase due to large volume differences

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidvolume stability during temperature change

Core Design Contradiction:

Ease of manufactureVSStability of the object's composition

Solution Approach 1:

Different materials are selected for the through electrode and junction electrode based on their specific functional requirements and stress characteristics, allowing each component to have optimal material properties for its location and function, thereby reducing volume fluctuation and stress

Inventive Principle:

Principle #3Local quality

3Strength

If high melting point metal is used for the through electrode, then structural integrity at high temperatures is improved, but stress during reflow process increases due to volume fluctuation

Engineering Contradiction:

Improvestructural integrity at high temperatureVSAvoidstress during reflow process

Core Design Contradiction:

StrengthVSStress or pressure

Solution Approach 1:

A composite electrode structure is employed where a high melting point metal provides structural integrity at high temperatures while a low melting point metal fills the through hole to accommodate volume fluctuations during reflow, combining the advantages of both materials to reduce stress

Inventive Principle:

Principle #40Composite materials

4Ease of manufacture

If low melting point metal is used for the junction electrode, then ease of joining is improved, but alloy formation that disrupts quantum mechanical states occurs

Engineering Contradiction:

Improveease of joiningVSAvoidquantum mechanical state stability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

A diffusion barrier layer is introduced as an intermediary between the low melting point metal and the through electrode, preventing alloy formation that would disrupt quantum mechanical states while still allowing the low melting point metal to provide ease of joining through its low melting temperature

Inventive Principle:

Principle #24Intermediary (Mediator)

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 effectively suppresses stress and volume fluctuation in the through electrode and junction electrode, maintaining structural integrity and preventing cracks, while avoiding alloy formation that could disrupt quantum mechanical states.

Implementation Method 1

a first metal that exhibits superconductivity at a temperature equal to or lower than a predetermined temperature... a second metal that exhibits superconductivity at a temperature equal to or lower than a predetermined temperature

Methodology Applied

Scientific EffectSuperconductivity: Superconductivity

Implementation Method 2

causing a strain mismatch between the at least one superconducting element and the dielectric layer when the superconducting device is operating in a cryogenic environment

Methodology Applied

Scientific EffectThermal expansion mismatch: Thermal Expansion

Data Source

PatentEP4318618B1Superconducting device, superconducting device manufacturing method, and laminated body

Publication Date: 2025.09.10 FUJITSU LTD

Figure 1
Figure 2
Figure 3A~3D

AI summary

A superconducting device includes: a substrate; a through hole provided in the substrate; a through electrode provided in the through hole, the through hole including a first portion and a second portion provided between the first portion and an inner wall surface of the through hole, in which the second portion is formed of a material including a first metal exhibiting superconductivity at a temperature lower than a criteria; a junction electrode electrically coupled to the through electrode, the junction electrode having at least a part provided outside the through hole and being formed of a material including a second metal exhibiting superconductivity at a temperature lower than a criteria; and a partition wall provided between the through electrode and the junction electrode and being formed of a material including the first metal, wherein a melting point of the first metal is higher than that of the second metal.