Solder Paste Flux Composition for Printability and Sagging Control
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Solution Overview
Problem
Amide-based thixotropic agents in soldering fluxes form unstable networks due to poor compatibility and high viscosity, leading to poor printability and inadequate inhibition of printing and 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 the acyclic amide compounds to form a uniform network, improving thixotropy and preventing precipitation, thereby enhancing printability and inhibiting sagging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an amide-based thixotropic agent is used to improve thixotropy and inhibit sagging, then printing sagging and heating sagging are inhibited, but printability deteriorates due to high viscosity and poor compatibility
Solution Approach 1:
The thixotropic agent is segmented into two distinct components: a cyclic amide compound (low molecular weight, 100-3000) and an acyclic amide compound (high molecular weight, 3000-100000). Each component performs a specific function - the cyclic compound provides thixotropy and sagging inhibition, while the acyclic compound provides viscosity control and compatibility, resolving the contradiction between sagging inhibition and printability
Solution Approach 2:
The invention changes the molecular weight parameter of the amide compounds used as thixotropic agents. By using low molecular weight cyclic amide compounds (100-3000) instead of high molecular weight amide polymers, the flux achieves sufficient thixotropy and sagging inhibition while maintaining low viscosity and good printability
2Reliability
If a high-molecular amide compound is used as thixotropic agent, then thixotropy is imparted, but viscosity increases extremely resulting in poor printability
Solution Approach 1:
The thixotropic function is segmented between two compounds with different molecular weights. The cyclic amide compound (low MW: 100-3000) provides thixotropy without causing extreme viscosity increase, while the acyclic amide compound (high MW: 3000-100000) provides viscosity control. This segmentation allows achieving thixotropy while maintaining printability
Solution Approach 2:
The invention uses a composite thixotropic system combining cyclic amide compound and acyclic amide compound. This composite approach allows the low MW cyclic compound to provide thixotropy while the high MW acyclic compound modulates viscosity, achieving both thixotropy and good printability simultaneously
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 with a cyclic and acyclic amide compound combination improves thixotropy, printability, and inhibits both printing and heating sagging in solder pastes, ensuring stable performance without increasing the acyclic amide compound content.
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
Data Source
AI summary
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 includes 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. 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 %.