Flux Composition for Fine-Particle Solder Paste Without Solder Balls
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Solution Overview
Problem
Solder pastes with small solder alloy powder particles experience increased viscosity over time, leading to deteriorated solderability and the generation of solder balls.
Innovation Solution
A solder paste composition featuring a flux with acid-modified rosin, a halogenated aliphatic compound, and a specific dicarboxylic acid, which maintains viscosity stability and prevents solder ball formation even with 99% of solder alloy particles having a particle size of 8 μm or less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the particle size of solder alloy powder is reduced to improve solderability, then the filling ability improves, but the viscosity of solder paste increases with time
Solution Approach 1:
The patent changes the chemical composition parameters of the flux by introducing a specific dicarboxylic acid (Formula 1) with controlled chain length (1-7 carbon atoms) and functional groups. This chemical parameter change modifies the flux's interaction with fine solder particles, preventing excessive viscosity increase over time while maintaining good solderability. The acid value and molecular structure parameters are specifically controlled to achieve the desired balance.
Solution Approach 2:
The patent creates a composite flux system combining dicarboxylic acid (Formula 1) with other conventional flux components including rosin derivatives, activators, and solvents. This composite formulation synergistically addresses the viscosity stability issue while preserving solderability, as each component contributes specific functions that collectively solve the contradiction between fine particle performance and temporal stability.
2Manufacturing precision
If the particle size of solder alloy powder is reduced to improve solderability, then the filling ability improves, but solder balls are likely to be generated
Solution Approach 1:
The patent modifies the chemical parameters of the flux by incorporating dicarboxylic acid (Formula 1) with specific molecular characteristics (1-7 carbon atoms in alkylene chain). This parameter change alters the wetting and bonding characteristics during reflow, preventing solder ball formation while maintaining excellent solderability with fine particles. The acid value and molecular weight parameters are controlled to optimize this effect.
3Volume of moving object
If the particle size of solder alloy powder is reduced to improve filling ability, then the ability to fill fine spaces improves, but viscosity increases with time
Solution Approach 1:
The patent changes the chemical composition parameters of the flux by introducing dicarboxylic acid (Formula 1) with controlled chain length and functional groups. This parameter modification reduces the time-dependent viscosity increase that normally occurs with fine solder particles, thereby maintaining good filling ability over extended periods while preserving the volume reduction characteristics of fine particles.
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 composition ensures excellent viscosity stability and prevents solder ball generation, enhancing solderability and performance in reflow processes.
Implementation Method 1
a flux used for soldering has the effect of chemically removing metal oxides present on a solder, and the metal surface of an object to be joined
Implementation Method 2
the activator contains a halogenated aliphatic compound
Implementation Method 3
the flux contains an acid-modified rosin, a solvent, an activator, and a thixotropic agent
Implementation Method 4
when the substrate is heated in a heating furnace called a reflow furnace, a solder is melted, and soldering is completed
Data Source
AI summary
A solder paste is adopted, the solder paste containing: a solder alloy powder in which a content of solder alloy particles having a particle size of 8 μm or less is 99% by mass or more with respect to a total mass of the solder alloy powder; and a flux. This flux contains an acid-modified rosin, a solvent, an activator, and a thixotropic agent, in which the activator contains a halogenated aliphatic compound, and a dicarboxylic acid represented by General Formula (2).[in the formula, R represents an alkylene group having 1 to 7 carbon atoms, or a single bond, provided that a methylene group constituting the alkylene group may be substituted with an oxygen atom]