Solder Paste Flux Composition That Prevents Separation and Cracking
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Solution Overview
Problem
Existing fluxes used in soldering processes suffer from cracking due to temperature changes, separation of solder paste into solder powder and flux over time, and decreased soldering strength when underfill is used, particularly in ball grid arrays and chip components.
Innovation Solution
A flux composition containing a copolymer with alkene- and acrylic acid-derived repeating units, rosin, and specific solvents, with controlled mixing ratios and optional inclusion of activators and thixotropic agents, to prevent separation and cracking while maintaining soldering strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a thixotropic agent is added to the flux to prevent separation of solder paste components, then the stability of the solder paste composition is improved, but the soldering strength decreases
Solution Approach 1:
The patent changes the chemical composition parameters of the flux by specifying a copolymer with specific repeating units (a1) and (a2) where the content of repeating unit (a2) is 3% by mass or more. This compositional parameter change provides stability equivalent to thixotropic agents without the negative effect on soldering strength
Solution Approach 2:
The patent extracts and eliminates the thixotropic agent from the flux composition while maintaining the desired stability effect through the copolymer's specific structure. The copolymer with controlled repeating unit composition replaces the thixotropic agent's function without its harmful side effects
2Stability of the object's composition
If the flux contains a copolymer with specific repeating units to prevent separation, then the stability of solder paste composition is improved, but the complexity of the flux formulation increases
Solution Approach 1:
The patent segments the copolymer structure into two distinct repeating units (a1) and (a2) with specific functional roles. Repeating unit (a1) provides the base polymer structure while repeating unit (a2) at 3% or more content provides the stability function, creating a segmented functional architecture that achieves stability without excessive complexity
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 cracking of flux residues due to temperature changes, maintains soldering strength, and inhibits separation of solder paste components over time, enhancing reliability and performance in soldering processes.
Implementation Method 1
the resin component contains a copolymer (A) having an alkene-derived repeating unit (a1), and an acrylic acid-derived repeating unit (a2)
Implementation Method 2
the resin component contains a copolymer (A) having an alkene-derived repeating unit (a1), and an acrylic acid-derived repeating unit (a2) in which a hydrogen atom bonded to a carbon atom at an α-position may be substituted with a substituent, and contains a rosin (B)
Data Source
AI summary
The present invention employs a flux containing a resin component, an activator, and a solvent. The resin component contains a copolymer (A) having an alkene-derived repeating unit (a1), and an acrylic acid-derived repeating unit (a2) in which a hydrogen atom bonded to a carbon atom at an α-position may be substituted with a substituent, and contains a rosin (B). A mixing ratio of the copolymer (A) and the rosin (B) is 1 or more as a mass ratio represented by copolymer (A)/rosin (B).