Flux Viscosity Stabilization via Methacrylate Polymer
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Solution Overview
Problem
The existing solder pastes experience viscosity variations during printing and application due to the destruction of the network structure in the flux caused by thixotropic agents, leading to inconsistent sedimentation suppression and printing quality issues.
Innovation Solution
Incorporating a methacrylate polymer, such as polyalkyl methacrylate, into the flux to enhance viscosity and control thixotropic index, while using hardened castor oil as a thixotropic agent to prevent sedimentation without hindering the effectiveness of sedimentation suppression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a thixotropic agent (hardened castor oil or amide type lubricant) is added to enhance elasticity and suppress sedimentation, then sedimentation suppression is improved, but viscosity varies significantly during stirring and printing
Solution Approach 1:
The patent changes the chemical composition parameters of the flux by incorporating specific polymers (polyalkylene glycol with molecular weight 10,000-100,000 at 1-10 parts by weight, and/or polyacrylic acid at 1-10 parts by weight) to modify the viscosity characteristics. This parameter change allows the solder paste to maintain stable viscosity during stirring while still achieving effective sedimentation suppression through the thixotropic agent.
Solution Approach 2:
The patent creates a composite flux system by combining multiple components: traditional thixotropic agents (hardened castor oil or amide type lubricant) with specific polymers (polyalkylene glycol and/or polyacrylic acid). This composite approach allows the different materials to work synergistically - the thixotropic agent provides sedimentation suppression while the added polymers stabilize the viscosity during processing operations.
2Stability of the object's composition
If the network structure in flux is formed to suppress sedimentation, then sedimentation suppression is improved, but the network structure is destroyed during stirring causing viscosity to drop
Solution Approach 1:
The patent modifies the rheological parameters of the flux by adding specific polymers that interact with the network structure formed by the thixotropic agent. The polyalkylene glycol and polyacrylic acid change the physical parameters of the flux to create a more stable network structure that resists destruction during stirring, thereby maintaining viscosity consistency and printing efficiency.
Solution Approach 2:
The added polymers (polyalkylene glycol and polyacrylic acid) act as intermediary substances that mediate between the network structure and the stirring process. These intermediaries protect the network structure from complete destruction during stirring, allowing the sedimentation suppression function to be maintained while enabling sufficient fluidity for printing operations.
3Shape
If thixotropic agent is added to maintain shape during application, then shape maintenance is improved, but chemical reaction between flux and solder powder accelerates causing artificial elasticity increase
Solution Approach 1:
The patent changes the chemical composition parameters by introducing specific polymers that modulate the chemical reactivity between flux and solder powder. The polyalkylene glycol and polyacrylic acid alter the reaction kinetics, preventing excessive acceleration of chemical reactions during stirring while maintaining the shape maintenance capability provided by the thixotropic agent.
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 addition of methacrylate polymer stabilizes viscosity and printing efficiency, allowing for controlled spread and residue formation, thereby enhancing the adhesive force and maintaining the effectiveness of sedimentation suppression, resulting in improved printing and soldering reliability.
Implementation Method 1
Any viscosity improver called as thixotropic agent is added to the flux used in the solder paste and it is designed to suppress sedimentation of the solder powder in the flux
Implementation Method 2
Incorporating a methacrylate polymer, such as polyalkyl methacrylate, into the flux to enhance viscosity and control thixotropic index
Implementation Method 3
The flux used for soldering generally has an efficacy such that metallic oxides on the solder and a metallic surface of the subject to be soldered are chemically removed
Implementation Method 4
The soldering is performed so that the board is heated in a heating furnace called as 'reflow furnace' to fuse the solder
Data Source
Figure 1~2
Figure 3~4
Figure 5A~5B
AI summary
To provide flux for producing solder paste, viscosity of which is prevented from varying. In the flux which is mixed with solder powder to produce the solder paste, an amount of methacrylate polymer which reduces a thixotropic index of the solder paste and enhances viscosity thereof is contained. As the methacrylate polymer, polyalkyl methacrylate having an alkyl group is preferable and it is preferable that an addition amount of polyalkyl methacrylate is 0.5-5.0 mass% thereof. Further, as the thixotropic agent, hardened castor oil is preferably added.