PCB Component Rework Using Liquid Metal Embrittlement

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Solution Overview

Problem

Conventional rework methods for electronic components on printed wiring boards, especially ball grid arrays, face challenges due to the difficulty in accessing and desoldering small, closely spaced pads without heating the entire device to the melting point of solder, leading to complex and costly processes with potential reliability issues.

Innovation Solution

The use of embrittlement agents, such as low-melt solder pastes or preformed sheets containing metals like Gallium and its alloys, which cause liquid metal embrittlement, allowing for the mechanical removal of components without damaging the board or adjacent components by reducing the tensile ductility of solder joints.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of repair

If hot air gun or hot air station is used to heat devices to melt solder, then solder can be melted and components can be removed, but the entire device must be heated to the melting point of solder which damages adjacent components and reduces board reliability

Engineering Contradiction:

Improvecomponent removal capabilityVSAvoidthermal damage to adjacent components

Core Design Contradiction:

Ease of repairVSObject-affected harmful factors

Solution Approach 1:

The embrittlement agent is applied to the solder joints before the actual removal process. This preliminary action causes the solder to become brittle at lower temperatures, enabling component removal without heating to solder melting point, thus avoiding thermal damage to adjacent components

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention changes the mechanical properties of the solder by introducing an embrittlement agent that alters the solder's ductility. This parameter change allows the solder to transition from a ductile state (requiring high temperature for removal) to a brittle state (allowing cold or low-temperature removal), resolving the contradiction between ease of repair and prevention of thermal damage

Inventive Principle:

Principle #35Parameter changes

2Ease of repair

If conventional desoldering methods are used for ball grid arrays, then components can be removed, but the process becomes complex and costly due to the need for specialized tools and procedures

Engineering Contradiction:

Improvecomponent removal capabilityVSAvoidrework process complexity

Core Design Contradiction:

Ease of repairVSDevice complexity

Solution Approach 1:

The invention extracts the complexity from the removal process by using a simple embrittlement agent application that eliminates the need for specialized desoldering tools, hot air stations, and complex heating procedures. The embrittlement agent enables straightforward mechanical removal, significantly simplifying the overall rework process

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The invention replaces complex thermal-mechanical systems (hot air stations, controlled heating equipment) with a simpler chemical-mechanical approach. The embrittlement agent chemically modifies the solder properties, allowing mechanical removal without the need for complex thermal processing equipment and procedures

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Ease of operation

If the entire device is heated to the melting point of solder, then all solder joints can be melted for component removal, but adjacent components and the board are exposed to harmful high temperatures

Engineering Contradiction:

Improvecomponent removal capabilityVSAvoidboard reliability after rework

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The embrittlement agent is applied locally to the specific solder joints requiring removal rather than heating the entire device. This localized approach affects only the target solder joints, leaving adjacent components and board areas unaffected, thus maintaining board reliability while enabling easy component removal

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The invention converts the typically harmful effect of chemical agents (which might be seen as contaminants) into a beneficial embrittlement effect. The embrittlement agent, which chemically interacts with the solder, transforms the solder's mechanical properties to enable easy removal, turning a potential harmful chemical process into a useful tool for simplified rework

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 method enables efficient and reliable removal of electronic components at lower temperatures, reducing the risk of damaging adjacent components and improving board reliability by allowing for precise control over the rework process, thus simplifying the removal of large components on high-mass printed wiring boards.

Implementation Method 1

The plurality of metal particles include one or more metals that cause liquid metal embrittlement of a solder material

Methodology Applied

Scientific EffectLiquid metal embrittlement:

Data Source

PatentUS12016127B2Liquid metal infiltration rework of electronic assembly

Publication Date: 2024.06.18 INTERNATIONAL BUSINESS MACHINE CORPORATION

AI summary

Provided is a method for removing an electronic component from a printed wiring board. The method comprises applying an embrittlement agent to a lead of an electronic component that is soldered to the printed wiring board. The electronic component is removed from the printed wiring board by breaking the embrittled lead.