Solder Paste Storage Stability via Thiol Protective Film
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Solution Overview
Problem
Existing solder pastes experience reduced storage stability due to interactions between activators and alloy solder powders, leading to rapid hardening and solidification during storage.
Innovation Solution
Incorporating a long-chain thiol and/or an organic chelating agent into the soldering flux, specifically hexanethiol, octanethiol, decanethiol, or octadecanethiol, and 1,10-o-naphthisodiazine, to form a single molecule protective film on the alloy solder powder surfaces, enhancing storage stability without affecting solderability or printability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional activators (organic acids, small molecules of organic amines, or halide-containing compounds) are used in soldering flux, then solderability is improved, but storage stability is reduced due to interaction with alloy solder powder during storage
Solution Approach 1:
The patent introduces a long-chain thiol as an intermediary substance that forms a protective film on the solder powder surface. This film acts as a mediator between the activator and the solder powder, allowing the activator to maintain its solderability-enhancing function while preventing direct harmful interactions that cause hardening during storage. The long-chain thiol molecules adsorb onto the powder surface, creating a barrier layer.
Solution Approach 2:
The patent employs a thin protective film formed by long-chain thiol molecules on the surface of alloy solder powder particles. This flexible molecular film serves as a protective shell that prevents direct contact between the activator and the solder powder, thereby maintaining storage stability while preserving solderability through controlled interaction.
2Reliability
If activators are used to improve wettability and cleaning of metal surfaces, then solderability is enhanced, but the rate of hardening or solidification increases during storage
Solution Approach 1:
The long-chain thiol acts as a mediator that allows the activator to perform its wettability-enhancing function during soldering while preventing premature hardening during storage. The thiol forms a controllable barrier that can be penetrated during the soldering process but prevents interaction during storage.
Solution Approach 2:
The patent changes the physical and chemical parameters of the flux composition by introducing long-chain thiols with specific chain lengths (C12-C22). This parameter change modifies the interaction dynamics between activators and solder powder, enabling the system to maintain stability during storage while retaining reactivity during soldering.
3Ease of operation
If existing activator formulations are used to ensure excellent processability, then soldering performance is improved, but storage stability is significantly reduced
Solution Approach 1:
The patent creates a composite flux formulation that combines conventional activators with long-chain thiol additives. This composite material integrates the wettability-enhancing properties of activators with the protective film-forming capabilities of long-chain thiols, achieving both excellent processability and improved storage stability.
Solution Approach 2:
The long-chain thiol serves as an intermediary component in the composite formulation, mediating between the activator and solder powder to enable excellent processability during soldering while maintaining storage stability through protective film formation.
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 solder paste exhibits significantly improved storage stability with minimal viscosity change over time, maintaining excellent solderability and printability, as demonstrated by viscosity measurements and wettability tests.
Implementation Method 1
Incorporating a long-chain thiol and/or an organic chelating agent into the soldering flux, specifically hexanethiol, octanethiol, decanethiol, or octadecanethiol, and 1,10-o-naphthisodiazine, to form a single molecule protective film on the alloy solder powder surfaces
Data Source
AI summary
The present invention relates to a solder paste composition, a solder paste and a soldering flux. The soldering flux comprises a resin, a thixotropic agent, an activator, a solvent as well as a long-chain thiol and/or an organic chelating agent.