Flux Composition for Lead-Free Soldering
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional fluxes used in soldering electronic components suffer from sticky residue, contamination, inadequate solder wettability under high-temperature conditions, and dewetting issues, particularly when used in lead-free soldering processes, leading to defects like cracking and insulation deterioration.
Innovation Solution
A flux composition incorporating polybutadiene (meth)acrylate compounds and hydrogenated dimer acids, along with rosin resin, within specific concentration ranges, which enhances solder wettability and thermal cycling resistance, preventing dewetting and cracking, even under high-temperature preheating in an air atmosphere.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional resin fluxes including synthetic resin or rosin resin are used, then solderability is improved by removing metal oxides and preventing reoxidation, but flux residue remains sticky and develops cracks under thermal cycling, causing contamination and insulation deterioration
Solution Approach 1:
The patent changes the chemical composition parameters of the flux by incorporating specific resin components (polybutadiene with 1,2-vinyl bonds, acrylic resin, or vinyl resin) in controlled amounts (0.1-5% by mass), along with carboxylic acid activators and halogenated solvents. This parameter optimization prevents flux residue cracking while maintaining solderability, resolving the contradiction between reliability and harmful residue effects.
Solution Approach 2:
The patent creates a composite flux formulation combining multiple resin types (polybutadiene, acrylic, or vinyl resin) with carboxylic acid activators and halogenated solvents. This composite approach synergistically improves solderability while the specific resin composition prevents flux residue cracking and contamination, addressing both sides of the contradiction.
2Object-generated harmful factors
If fluxes with low glass transition temperature acrylic resin or hydrogenated polybutadiene are used, then flux residue cracking is suppressed, but solder wettability becomes insufficient under high-temperature preheating conditions of 160°C or more
Solution Approach 1:
The patent optimizes the glass transition temperature parameter of the resin component to be -50°C to 0°C, and controls the resin content at 0.1-5% by mass. This parameter adjustment ensures the flux residue remains flexible at high temperatures to prevent cracking, while the carboxylic acid activator and halogenated solvent maintain effective solder wettability during high-temperature preheating, resolving the contradiction between crack suppression and wettability.
3Ease of manufacture
If conventional fluxes are used under lead-free soldering high-temperature preheating conditions, then soldering process is simplified, but dewetting occurs and solder wettability is insufficient
Solution Approach 1:
The patent adjusts the chemical composition parameters including carboxylic acid activator content (0.1-5% by mass), halogenated solvent content (10-80% by mass), and resin type selection. This formulation enables the flux to maintain effective solder wettability under high-temperature preheating conditions (160°C or more) in air atmosphere, allowing simplified lead-free soldering processes without dewetting issues.
Solution Approach 2:
The patent's flux formulation with halogenated solvents and carboxylic acid activators creates a protective chemical environment that prevents oxidation and dewetting during high-temperature preheating in air atmosphere, effectively creating a chemically inert-like environment that maintains solder wettability while allowing process simplification.
4Device complexity
If reflow heating is performed in air atmosphere, then process complexity is reduced, but solder wettability cannot be sufficiently exhibited and only nitrogen atmosphere reflow works
Solution Approach 1:
The patent modifies the flux chemical composition parameters including the addition of carboxylic acid activators (0.1-5% by mass) and halogenated solvents (10-80% by mass), along with specific resin selection. This formulation enables solder wettability to be sufficiently exhibited during reflow heating in air atmosphere, eliminating the need for nitrogen atmosphere control and reducing process complexity while maintaining reliability.
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 ensures reliable solderability and prevents cracking in flux residue, maintaining good solder wettability and insulation properties, even under severe thermal cycles, making it suitable for high-temperature applications like automotive electronics.
Implementation Method 1
a film portion referred to as flux residue resulting from the resin component in the flux remains on the electronic circuit mounted substrate after the soldering. This flux residue can contain fissures (cracks) caused by temperature changes during the thermal cycle
Implementation Method 2
blended in a solder composition and the like in order to improve solderability by removing metal oxides on a surface conductive portion of the printed circuit substrate
Implementation Method 3
preventing the solder alloy from reoxidizing during soldering
Implementation Method 4
reducing the surface tension of the solder
Implementation Method 5
performing reflow for main heating
Data Source
AI summary
Provided is a flux that includes at least one polybutadiene (meth)acrylate compound selected from the group consisting of polybutadiene (meth)acrylate compounds represented by the following formula 1 and polybutadiene (meth)acrylate compounds represented by the following formula 2, and a hydrogenated dimer acid. R'=-H, or -CH3 R'=-H, or -CH3