Solder Paste Flux Composition for Void and Separation Control
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Solution Overview
Problem
Existing solder pastes face issues with separation between flux and solder powder, environmental burden during cleaning, and void generation due to thixotropic agent burning and viscosity changes, which are not adequately addressed in prior art.
Innovation Solution
A flux composition with reduced thixotropic agent content and increased polyethylene glycol (PEG) content, maintaining a liquid state at high temperatures to prevent separation and voids, allowing easy cleaning with environmentally friendly liquids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the content of thixotropic agent is increased to reduce slump property and prevent solder ball generation, then printing performance is improved, but the thixotropic agent is burned during extended melting time and cleaning becomes difficult
Solution Approach 1:
The patent changes the chemical composition parameters of the flux by specifying precise content ranges of PEG (1-10 mass%), thixotropic agent (2-20 mass%), and other components. This parameter optimization allows the flux to maintain appropriate viscosity and printing performance while reducing thixotropic agent burning during extended melting processes
Solution Approach 2:
The patent creates a composite flux system combining multiple components (PEG, thixotropic agent, alcohol, water, carboxylic acid, halogen compound, amine compound) in specific proportions. This composite formulation balances the competing requirements of printing performance, reduced burning, and ease of cleaning
2Object-generated harmful factors
If the content of thixotropic agent is restricted to prevent burning, then cleaning is easier, but separation between solder powder and flux occurs due to decreased thixotropic property and viscosity
Solution Approach 1:
The patent optimizes the thixotropic agent content within a specific range (2-20 mass%) and balances it with PEG content (1-10 mass%) to maintain adequate viscosity and thixotropic properties. This prevents flux-solder powder separation during storage while limiting thixotropic agent burning during reflow
Solution Approach 2:
The patent introduces PEG as an intermediary substance that mediates between the flux and solder powder. PEG maintains appropriate viscosity and prevents separation while the controlled thixotropic agent content prevents burning, thus resolving the contradiction between preventing separation and reducing burning
3Stability of the object's composition
If PEG content is increased to prevent viscosity increase and improve storage stability, then printing performance is improved, but slump property decreases and solder ball generation increases
Solution Approach 1:
The patent precisely controls PEG content within 1-10 mass% to prevent excessive viscosity increase and maintain storage stability. Simultaneously, the thixotropic agent content is optimized at 2-20 mass% to maintain slump property and prevent solder ball generation, thus resolving the contradiction between storage stability and printing 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 flux composition effectively prevents separation between flux and solder powder and reduces void generation, facilitating easy cleaning with low-detergency, environmentally friendly cleaning liquids.
Implementation Method 1
increased polyethylene glycol (PEG) content, maintaining a liquid state at high temperatures to prevent separation and voids
Implementation Method 2
a content of the thixotropic agent excluding the polyethylene glycol is 5 mass % or less with respect to the total mass of the flux
Implementation Method 3
facilitating easy cleaning with low-detergency, environmentally friendly cleaning liquids
Data Source
AI summary
A solder paste includes a solder powder and a flux. The flux includes a rosin, an activator, a solvent, and a thixotropic agent containing a polyethylene glycol. A content of the polyethylene glycol is 10 mass % to 20 mass % with respect to a total mass of the flux, a content of the thixotropic agent excluding the polyethylene glycol is 5 mass % or less with respect to the total mass of the flux, and a content of the rosin is more than 15 mass % and 50 mass % or less with respect to the total mass of the flux.