Solder Paste Flux Composition for Thixotropy Without Print Sagging
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Solution Overview
Problem
Amide-based thixotropic agents in soldering fluxes form unstable networks due to high-molecular polymer compatibility issues, leading to poor printability and excessive viscosity, while ester-based agents inadequately inhibit heating sagging.
Innovation Solution
A flux containing a thixotropic agent with a combination of cyclic and acyclic amide compounds, where the cyclic amide compounds crosslink acyclic amides to form a uniform network, improving thixotropy and inhibiting sagging without increasing acyclic amide content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the amount of high-molecular amide compound is increased to enhance thixotropy, then thixotropy is improved, but viscosity increases excessively resulting in poor printability
Solution Approach 1:
The invention changes the molecular weight parameter of the thixotropic agent system by introducing a low molecular weight cyclic amide compound (molecular weight 3,000 or less) in combination with an acyclic amide compound. This parameter change allows achieving sufficient thixotropy without the excessive viscosity increase that would result from using only high-molecular-weight compounds, thereby maintaining good printability
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 flux achieves enhanced printability, prevents bleeding and blurring, and effectively inhibits both printing and heating sagging in solder pastes, maintaining thixotropy without excessive precipitation.
Implementation Method 1
In the amide-based thixotropic agent, intramolecular and intermolecular hydrogen bonds are easily formed due to an amide bond
Implementation Method 2
The thixotropic agent constructs a network in the flux and imparts thixotropy. When the flux has thixotropy, its viscosity lowers when shear force is applied thereto
Implementation Method 3
the flux contains the thixotropic agent, so that sagging of a solder paste after printing, which is referred to as printing sagging, and sagging of a solder paste when molten by heating, which is referred to as heating sagging, are held by the network formed by the thixotropic agent, thereby inhibiting sagging of the flux
Data Source
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AI summary
Provided are: a flux which imparts thixotropy, and which exhibits excellent printability, printing sagging-inhibiting ability, and heating sagging-inhibiting ability; and a solder paste which uses said flux. This flux includes a thixotropic agent, a rosin, an organic acid, and a solvent. The thixotropic agent comprises: a cyclic amide compound obtained by polycondensing a dicarboxylic acid and/or a tricarboxylic acid, and a diamine and/or a triamine into a cyclic shape; and an acyclic amide compound which is obtained by polycondensing a monocarboxylic acid, a dicarboxylic acid and/or a tricarboxylic acid into an acyclic shape. In the cyclic amide compound, the carbon numbers of the dicarboxylic acid and the tricarboxylic acid are in the range of 3 to 10 inclusive, and the carbon numbers of the diamine and the triamine are in the range of 2-54 inclusive. The flux includes at least 0.1 wt% but not more than 8.0 wt% of the cyclic amide compound, and at least 0.5 wt% but not more than 8.0 wt% of the acyclic amide compound. The total amount of the cyclic amide compound and the acyclic amide compound is at least 1.5 wt% but not more than 10.0 wt%.