Flux Resin Composition for High Tg Solder Joint Reliability
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Solution Overview
Problem
Existing flux resin compositions used in soldering for electronic components have low glass transition points (Tg) and poor storage stability, which can lead to unreliable performance under heat cycles and reduced productivity.
Innovation Solution
A flux resin composition comprising an epoxy resin with a high glass transition point, an imidazole compound with a melting point of 130°C or higher, a thixo agent, and an activator, which together provide improved storage stability and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a bisphenol A epoxy resin with long-chain dibasic acid is used as a thermosetting resin in flux, then the flux can eliminate the need for cleaning and reinforce soldering portions, but the cured product has low Tg and poor heat cycle resistance
Solution Approach 1:
The patent changes the chemical parameters of the epoxy resin from conventional bisphenol A type to high Tg types (phenoxy, alicyclic, biphenyl, naphthalene, or dicyclopentadiene epoxy resins), which fundamentally alters the glass transition temperature of the cured flux residue from below 85°C to 85°C or higher, thereby improving heat cycle resistance while maintaining the cleaning-free reinforcement function
Solution Approach 2:
The patent creates a composite flux resin system combining high Tg epoxy resin with specific activators (carboxylic acid, phenolic resin, or resin acid) and optional underfilling material components, forming a multi-functional composite that simultaneously provides flux action, high temperature resistance, and reinforcement properties
2Ease of manufacture
If the Tg of the reinforcement material is set below the heat cycle temperature range, then the material remains processable, but the reinforcement effect is reduced due to steep increase in coefficient of linear expansion at Tg
Solution Approach 1:
The patent raises the Tg parameter of the reinforcement material (flux residue) to 85°C or higher through selection of specific high Tg epoxy resins, ensuring that the material's glass transition point exceeds the maximum operating temperature of −40°C to 85°C, thereby maintaining both processability and strong reinforcement effect throughout the heat cycle range
3Strength
If long-chain dibasic acid is used as a reactive component in the epoxy resin, then the resin can cure and form reinforcement, but the flux has poor storage stability and causes problems in continuous productivity
Solution Approach 1:
The patent extracts and removes the problematic long-chain dibasic acid component from the flux formulation, replacing it with alternative curing mechanisms using activators such as carboxylic acids, phenolic resins, or resin acids that provide sufficient curing capability without compromising storage stability, thereby enabling continuous productivity
Solution Approach 2:
The patent replaces the unstable long-chain dibasic acid with short-lived, stable alternatives (activators added just before use or with controlled reactivity) that fulfill the curing function temporarily during the soldering process but do not cause storage stability issues, effectively using a disposable curing mechanism
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 proposed flux resin composition achieves a high glass transition temperature for the cured product, enhancing the reliability and heat cycle resistance of solder joints, while maintaining good storage stability and productivity.
Implementation Method 1
a flux resin composition includes an epoxy resin (A), an imidazole compound (B), a thixo agent (C), and an activator (D)... a cured product of the flux resin composition
Implementation Method 2
a thixo agent (C)... a flux resin composition includes an epoxy resin (A), an imidazole compound (B), a thixo agent (C), and an activator (D)
Implementation Method 3
an activator (D)... the epoxy resin (A), an imidazole compound (B), a thixo agent (C), and an activator (D)
Data Source
AI summary
A flux resin composition includes an epoxy resin, an imidazole compound, a thixo agent, and an activator. The epoxy resin includes at least one resin selected from the group consisting of naphthalene epoxy resins, biphenyl aralkyl epoxy resins, trisphenol methane epoxy resins, biphenyl epoxy resins, and dicyclopentadiene epoxy resins. The content of the at least one resin is equal to or greater than 20% by weight with respect to a total weight of the epoxy resin.