Epoxy Solder Flux Composition Without Film Formation
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Solution Overview
Problem
Conventional flux compositions containing epoxy resin and curing agents like imidazoles, amines, and phenol novolacs face challenges in printability, solderability, and flux residue curability, requiring a film formation step and often losing activity due to reactions with activators during heating.
Innovation Solution
A flux composition with 20-50 wt% epoxy resin, 15-45 wt% diallyl bisphenol A as both a curing agent and activator, and 1-30 wt% organic acid, allowing application at room temperature without film formation, suppressing reactions and ensuring sufficient curing and solder wetting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If conventional curing agents (imidazoles, amines, phenol novolacs) are used with epoxy resin, then curing acceleration is achieved, but printability and solderability deteriorate due to insufficient activity and poor wettability
Solution Approach 1:
The patent changes the chemical structure parameter of the curing agent from conventional imidazoles/amines/phenol novolacs to phenol-based curing agents with specific hydroxyl group configurations. This structural parameter change enables the curing agent to maintain high activity at room temperature for printability while providing sufficient wettability for solderability, and achieving adequate curing speed through the specific phenolic hydroxyl group arrangement.
Solution Approach 2:
The patent creates a composite flux composition by combining epoxy resin with specific phenol-based curing agents that possess dual functionality. The composite system integrates the adhesive properties of epoxy resin with the activating capability of phenolic compounds, achieving simultaneous improvement in printability, solderability, and curing performance that neither component could achieve alone.
2Duration of action of moving object
If phenol-based curing agents are used, then curing activity is improved, but film formation step is required and activity is lost due to reaction with activators during heating
Solution Approach 1:
The patent applies preliminary action by formulating the flux composition with phenol-based curing agents that are pre-configured to remain stable during storage and application. The curing reaction is preliminarily controlled to occur only during the soldering heating process, eliminating the need for a separate film formation step while preserving the activating activity until the moment of use.
Solution Approach 2:
The patent introduces an intermediary mechanism where the phenol-based curing agent acts as a mediator between the epoxy resin and the soldering heat. The curing agent intermediates the reaction by remaining inert during application and storage, then activating the epoxy curing process only when exposed to soldering temperatures, thereby eliminating premature reactions with activators.
3Reliability
If activators are added to enhance flux activity, then solderability is improved, but activity is lost due to reaction with epoxy resin upon heating
Solution Approach 1:
The patent applies universality by designing phenol-based curing agents that perform multiple functions simultaneously: they act as curing agents for epoxy resin, maintain flux activity for solder wetting, and remain stable during storage and application. This multi-functionality eliminates the need for separate activators, preventing the loss of activity through reactions while maintaining enhanced solderability.
4Strength
If epoxy resin content is increased for better adhesion, then joint strength is improved, but viscosity increases and printability deteriorates
Solution Approach 1:
The patent changes the viscosity parameter by selecting specific phenol-based curing agents with appropriate molecular weights and structural characteristics. These curing agents maintain low viscosity even at high epoxy resin contents (50-70 wt%), enabling good printability while preserving the high joint strength provided by the high epoxy resin content through optimized curing reaction efficiency.
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 achieves improved printability, solderability, and flux residue curability, eliminating the need for heating and maintaining activity, thus enhancing the reliability of solder joints.
Implementation Method 1
diallyl bisphenol A, which functions as a curing agent to accelerate the curing of an epoxy resin
Implementation Method 2
has an activity and functions as an activator in the temperature range assumed for soldering
Implementation Method 3
1 wt % or more and 30 wt % or less of organic acid
Data Source
AI summary
Provided are a flux composition that is applicable without any film formation step, and solder paste, a solder joint and a solder joining method using the flux composition. The flux composition contains 20 wt % or more and 50 wt % or less of an epoxy resin, 15 wt % or more and 45 wt % or less of diallyl bisphenol A, and 1 wt % or more and 30 wt % or less of organic acid.