Halogen-Free Solder Paste Composition for Wetting and Low Residue
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Solution Overview
Problem
Current solder pastes used in electronics manufacturing contain lead and halogen elements, making them difficult to recycle and causing environmental pollution, and they often result in poor welding performance issues like solder beading, bridging, and non-wetting, which affect the reliability of electronic products.
Innovation Solution
A lead-free and halogen-free solder paste is developed using a Sn-2.5Be-0.8Ag-0.5Cu alloy powder with a specific welding flux composition that includes itaconic acid, succinic acid, a surfactant, thixotropic agent, modified rosin, composite solvent, corrosion inhibitor, and an acrylic type activator, which enhances wettability and reduces residue and corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If lead-free and halogen-free solder paste is developed to reduce environmental pollution, then environmental friendliness is improved, but welding performance deteriorates due to issues like solder beading, bridging, and non-wetting
Solution Approach 1:
The patent modifies the chemical composition parameters of the activator by replacing traditional inorganic halide activators with organic carboxylic acid activators (itaconic acid, succinic acid, maleic acid) and their amine salts. This parameter change eliminates halogen elements while maintaining welding performance through the carboxyl group's ability to remove oxides and promote wetting.
Solution Approach 2:
The patent creates a composite activator system combining multiple carboxylic acids (itaconic acid, succinic acid, maleic acid) with amine salts and optional inorganic halides in controlled proportions. This composite approach compensates for the loss of halogen-based activation while achieving both lead-free and halogen-free goals with improved welding performance.
2Reliability
If inorganic halide activator is added to remove oxide and assist wetting, then welding performance is improved, but halogen element is introduced making the solder paste difficult to recycle and causing environmental pollution
Solution Approach 1:
The patent extracts and removes halogen elements from the activator composition by replacing inorganic halide activators with organic carboxylic acid-based activators. This extraction eliminates the harmful halogen component while preserving the essential oxide-removing and wetting-promoting functions through carboxyl group chemistry.
Solution Approach 2:
The patent employs organic carboxylic acids and amine salts that decompose completely during welding and volatilize without leaving harmful halogen residues. These activators are consumed during the welding process, providing their function temporarily and then disappearing without environmental persistence, unlike halogen-based activators.
3Reliability
If organic amine activator is used in lead-free solder paste, then lead-free requirement is met, but residue after welding has strong hygroscopicity causing surface insulation resistance to decrease
Solution Approach 1:
The patent modifies the activator composition by using carboxylic acids with specific carbon chain lengths and structures (itaconic acid, succinic acid, maleic acid) combined with amine salts in controlled ratios. This parameter optimization reduces the hygroscopicity of welding residues while maintaining the lead-free requirement and welding performance.
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 new solder paste improves welding performance, reduces residue and corrosion, and achieves high surface insulation resistance, addressing the environmental concerns and reliability issues of existing solder pastes.
Implementation Method 1
an acrylic type activator, which enhances wettability and reduces residue and corrosion
Implementation Method 2
20-40 parts of a composite solvent
Implementation Method 3
3-8 parts of a thixotropic agent
Implementation Method 4
1-3 parts of a surfactant
Implementation Method 5
3-8 parts of a corrosion inhibitor
Data Source
AI summary
The present application relates to the technical field of welding materials, and particularly to a lead-free and halogen-free solder paste, including a solder alloy powder and a welding flux with a mass ratio of 85-90:10-15, the solder alloy powder is Sn-2.5Be-0.8Ag-0.5Cu alloy powder, and the welding flux includes the following components: itaconic acid, succinic acid, a surfactant, a thixotropic agent, modified rosin, a composite solvent, a corrosion inhibitor, and an acrylic type activator. Its preparation method includes the following steps: mixing the modified rosin, the composite solvent and the corrosion inhibitor, heating under stirring, cooling, adding itaconic acid, succinic acid and the acrylic type activator under stirring, cooling, adding the thixotropic agent for emulsification dispersion, adding the surfactant under stirring, grinding to obtain a welding flux after cooling, and stirring the solder alloy powder and the welding flux under vacuum to obtain the solder paste.