Soldering Paste Flux Storage Stability and Curing
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Solution Overview
Problem
Soldering pastes with highly reactive resins or curing agents have poor storage stability due to increased viscosity during storage, and existing low-temperature solders lack mechanical strength, especially under varying environmental conditions with temperature fluctuations and vibrations.
Innovation Solution
A soldering paste flux comprising a bifunctional epoxy prepolymer, a polyfunctional epoxy monomer or oligomer, a carboxylic acid with a melting point of 80-170°C, and a cyanate ester, which together provide excellent storage stability, rapid curing at low temperatures, and high durability of the cured resin layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a highly reactive resin or curing agent is used to shorten curing time, then productivity is improved, but storage stability deteriorates due to increased viscosity during storage
Solution Approach 1:
The curing system is segmented into two distinct components: a thermosetting prepolymer (Component A) that provides stability during storage, and a curing agent (Component E) that initiates rapid curing when mixed. This segmentation allows the reactive components to be separated during storage, preventing premature reaction, while enabling fast curing when combined during the soldering process.
Solution Approach 2:
The thermosetting prepolymer undergoes preliminary preparation by pre-reacting or pre-polymerizing to form a stable intermediate product that can be stored without further reaction. This preliminary action creates a reservoir of reactive groups that will only complete the curing process when the curing agent is introduced, thus achieving both storage stability and rapid curing capability.
2Use of energy by moving object
If SnBi-type low-temperature solder is used to reduce environmental burden, then energy consumption is reduced, but mechanical strength deteriorates
Solution Approach 1:
The invention creates a composite material system combining SnBi-type low-temperature solder with a thermosetting resin matrix. The solder provides low melting point and electrical conductivity, while the cured resin provides mechanical strength and structural support. This composite approach allows the joint to achieve both low processing temperature and high mechanical strength.
Solution Approach 2:
Different regions of the joint are assigned different functions: the solder layer provides electrical connection and low-temperature bonding, while the surrounding cured resin film provides mechanical reinforcement. This local differentiation of material properties allows each component to optimize its specific function without compromising overall joint strength.
3Strength
If a soldering paste is held for a given time in the temperature region where resin curing progresses, then joint strength is improved, but productivity deteriorates due to extended heating retention time
Solution Approach 1:
The curing system is designed to change its reaction parameters optimally at the soldering temperature range. The curing agent and prepolymer are selected to have maximum reactivity at typical soldering temperatures (180-250°C), enabling complete curing to occur rapidly during the brief heating cycle, thus achieving strong joints without extended retention time.
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 soldering paste exhibits excellent storage stability, rapid curing, and high durability, with a cured resin layer that maintains strength and flexibility, suitable for electronic components under diverse environmental conditions.
Implementation Method 1
a polyfunctional epoxy monomer or oligomer having three or more functional groups in a molecule
Implementation Method 2
a carboxylic acid having a melting point of 80 to 170°C
Implementation Method 3
a cyanate ester having two or more cyanato groups in a molecule
Data Source
AI summary
The present invention relates to a soldering paste flux, and the soldering paste flux includes (A) a thermosetting prepolymer, (B) a polyfunctional epoxy monomer or oligomer having three or more functional groups in a molecule, (C) a carboxylic acid having a melting point of 80 to 170°C, and (D) a cyanate ester having two or more cyanato groups in a molecule.