Solder Rework via Liquid Metal Embrittlement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lead-free solder materials, particularly those derived from metal nanoparticles, face challenges in rework due to increased processing temperatures required after partial fusion, making it difficult to replace failed components without causing thermal damage to temperature-sensitive components.
Innovation Solution
The method involves using a disintegrating agent, such as bismuth or bismuth alloys, to induce liquid metal embrittlement in the solder, allowing for the disintegration and removal of joined members at lower temperatures, mirroring the rework capabilities of traditional lead-based solders.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If metal nanoparticle-based solder materials are used to replace lead-based solder, then the eutectic melting point is reduced and soldering temperature is lowered, but rework becomes difficult due to higher processing temperatures needed after partial fusion of nanoparticles
Solution Approach 1:
A flux composition acts as an intermediary substance that facilitates rework by dissolving the solder material. The flux contains organic acids and their salts that chemically interact with the solder joints, enabling removal without requiring high temperatures that would damage temperature-sensitive components.
Solution Approach 2:
The invention changes the chemical parameters of the flux composition by incorporating specific organic acids (formic acid, acetic acid, propionic acid, butyric acid) and their salts, along with controlled water content (5-50%), to optimize the dissolution of solder materials at lower temperatures, thereby enabling easy rework.
2Ease of repair
If lead-based solder is used, then rework is easy and processing temperature is low, but lead is toxic and banned in most commercial products
Solution Approach 1:
The invention uses a disposable flux composition that can be applied to dissolve solder joints for rework. This flux is designed to be used temporarily during rework operations and then removed, allowing easy repair of lead-free solder joints without the need for permanent chemical residues or high-temperature processes.
3Object-affected harmful factors
If SAC solder system is used as lead-free alternative, then lead elimination is achieved, but processing temperature increases and component compatibility is reduced
Solution Approach 1:
The flux composition is specifically formulated with organic acids and their salts to change the chemical parameters of the rework process, enabling dissolution of SAC solder material at lower temperatures. The controlled water content (5-50%) and specific acid combinations allow the flux to effectively dissolve lead-free solder without requiring the high temperatures that would damage temperature-sensitive components.
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 approach enables easy and repeated rework of solders containing metal nanoparticles, like copper, at temperatures comparable to traditional lead-based solders, reducing thermal stress on components and facilitating the replacement of failed components in electronics and other applications.
Implementation Method 1
heating the solder to liquefy the disintegrating agent
Data Source
AI summary
Methods for reworking a solder containing one or more joined members are described herein. Such methods can include applying a disintegrating agent to a solder containing a solder material, disintegrating the solder material to form a disintegrated solder material, and removing the disintegrated solder material from the solder. Such methods can also include applying a disintegrating agent containing bismuth to a solder containing a solder material, and heating the solder to liquefy the disintegrating agent. Such methods can also include applying a disintegrating agent containing a bismuth alloy to a solder having a solder material that contains metal nanoparticles, and heating the solder to liquefy the bismuth alloy.