Quantum Control Board Solder Joint Geometry for Low-Temperature Fracture Prevention

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Solution Overview

Problem

In quantum computers operating at extremely low temperatures, surface-mounted electronic components can experience brittle fracture and interfacial cracking due to thermal expansion differences and allotropic transformations of solder materials, leading to reliability issues.

Innovation Solution

A control board structure is developed with a solder bonding portion that covers the outer corner and adjacent surfaces of electrodes and pads, using solder with tin as a main component, to prevent low-temperature brittle fracture and interfacial cracking.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If solder is used for bonding electronic components to the wiring board, then electrical connection and mechanical bonding are achieved, but interfacial cracking occurs at extremely low temperatures due to difference in linear expansion coefficients

Engineering Contradiction:

Improvebonding reliabilityVSAvoidinterfacial cracking

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies local quality by creating a solder bonding portion with specific geometric characteristics (rounded corners, extended surfaces) that differ from conventional solder joints. The solder bonding portion is configured to cover outer corner portions of electrodes and pad surfaces, creating localized stress distribution zones that prevent cracking while maintaining overall bonding integrity at extremely low temperatures.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes geometric parameters of the solder bonding portion, specifically defining rounded corner radii and extended surface coverage. These parameter modifications transform the solder joint from a conventional shape to one that distributes thermal expansion stresses more effectively, preventing interfacial cracking while maintaining electrical connection reliability.

Inventive Principle:

Principle #35Parameter changes

2Strength

If allotropic transformation of solder is allowed to occur at low temperatures, then bonding strength is maintained, but reliability deteriorates due to brittle fracture

Engineering Contradiction:

Improvebonding strengthVSAvoidbonding reliability

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent applies beforehand cushioning by pre-configuring the solder bonding portion geometry to accommodate and cushion the effects of allotropic transformation. The rounded corner design and extended surface coverage create a buffer zone that absorbs stress changes during temperature cycling, preventing brittle fracture while maintaining bonding strength through the geometric configuration rather than relying solely on material properties.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Ease of manufacture

If conventional soldering is used without special geometry control, then manufacturing is simple, but brittle fracture occurs at extremely low temperatures

Engineering Contradiction:

Improvesoldering process simplicityVSAvoidcomponent bonding reliability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent modifies soldering parameters by controlling the geometric shape of the solder bonding portion, specifically the rounded corner radii and surface extension dimensions. These parameter changes are implemented through standard soldering processes by controlling solder paste application and reflow conditions, achieving reliable low-temperature bonding without requiring complex manufacturing procedures.

Inventive Principle:

Principle #35Parameter changes

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

The proposed solution effectively prevents interfacial cracking and improves bonding reliability of surface-mounted electronic components in quantum computers operating at temperatures as low as 77K or lower.

Implementation Method 1

cracking may occur between the members due to a difference in linear expansion coefficient of each components

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

In the case where the electronic component and the wiring board are bonded to each other with solder containing tin (Sn) as a main component, allotropic transformation occurs when left at low temperatures

Methodology Applied

Scientific EffectAllotropic transformation: Phase Change

Data Source

PatentUS20250071905A1Control board and method for manufacturing same

Publication Date: 2025.02.27 HITACHI LTD

AI summary

A fracture due to crack growth occurring in a solder bonding portion of a wiring board of a control board in a quantum computer operating in a low-temperature environment can be prevented. There is provided a control board in which a chip electronic component having a plurality of electrodes formed thereon is connected to, by solder bonding portions, a wiring board having a wiring pattern and soldering pads formed on a front surface thereof. On the electrodes, after soldering, corner portions of the electrodes on the wiring board and entire lower surfaces thereof are covered with solder bonding portions, and corner portions of the pads on a side close to the electronic component and entire upper surfaces thereof are covered with the solder bonding portions.