One-Pack Epoxy Resin Composition for Low-Temperature Curing
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Solution Overview
Problem
Conventional epoxy resin compositions used in electronic components, particularly relays, face challenges in maintaining airtightness at high temperatures due to insufficient heat resistance and adhesion issues when using lead-free solders, especially when cured at low temperatures.
Innovation Solution
A one-pack type epoxy resin composition combining epoxy resin, dicyandiamide, and a non-latent imidazole compound, which accelerates curing and enhances adhesion between formed members and metal terminals, allowing for low-temperature curing and high heat resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If dicyandiamide is used solely as the latent curing agent for low-temperature curing, then curing temperature can be reduced to 120°C or lower, but the cured product has insufficient heat resistance and poor airtightness
Solution Approach 1:
The patent uses a composite curing agent system combining dicyandiamide (latent curing agent) with a non-latent imidazole compound (curing accelerator). This composite approach allows the epoxy resin to cure at low temperatures (120°C or lower) while the imidazole compound ensures complete reaction and provides sufficient heat resistance and airtightness that neither curing agent could achieve alone.
Solution Approach 2:
The patent changes the chemical composition parameters of the curing system by introducing a non-latent imidazole compound with specific structural features (aromatic ring, imidazole group, and electron-withdrawing substituent). This parameter change enables the system to achieve both low-temperature curing capability and high heat resistance by optimizing the reactivity and thermal stability of the curing agents.
2Temperature
If conventional epoxy resin compositions are used with lead-free solders, then soldering temperature increases by 20°C to 30°C, but the sealing agent has insufficient heat resistance leading to poor airtightness
Solution Approach 1:
The patent applies beforehand cushioning by using a curing agent system that pre-establishes sufficient heat resistance and crosslinking density before the high-temperature soldering process. The non-latent imidazole compound ensures complete curing and forms a robust network structure that can withstand the increased soldering temperatures of lead-free solders without compromising airtightness.
Solution Approach 2:
The composite curing agent system provides synergistic effects where dicyandiamide enables low-temperature curing while the non-latent imidazole compound ensures high heat resistance. This composite approach creates a sealing agent that is specifically optimized to withstand both the low curing temperature and the subsequent high soldering temperature of lead-free processes.
3Temperature
If dicyandiamide is used as the curing agent, then low-temperature curing is achieved, but unreacted substances remain and adhesion between formed member and metal terminal is insufficient
Solution Approach 1:
The non-latent imidazole compound acts as an intermediary that facilitates complete reaction of the epoxy resin with the curing agents. It mediates the curing process by providing additional reactive sites and accelerating the reaction, ensuring that no unreacted substances remain and that strong adhesion is achieved between the formed member and metal terminal even at low curing temperatures.
Solution Approach 2:
The patent changes the reaction kinetics parameters by introducing the non-latent imidazole compound, which has higher reactivity than dicyandiamide alone. This parameter change ensures complete conversion of epoxy groups to crosslinked structures, maximizing adhesion strength while maintaining low curing temperature capability.
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 effectively maintains airtightness and heat resistance even after reflow processes using lead-free solders, preventing solder flux and gas intrusion, thus ensuring reliable electronic component sealing.
Implementation Method 1
an epoxy resin composition containing an epoxy resin, dicyandiamide, an epoxy resin adduct compound, and a non-latent imidazole compound which has a curing accelerating effect at a low temperature
Implementation Method 2
improve adhesion between the formed member and the metal terminal so as to maintain airtightness in the relay
Data Source
Figure 1~2
AI summary
Disclosed is a one-pack type epoxy resin composition containing an epoxy resin, dicyandiamide, an epoxy resin adduct compound, and a non-latent imidazole compound. The one-pack type epoxy resin composition is capable of being cured at a low temperature, while having excellent heat resistance and sealing properties. Also disclosed is use of the one-pack type epoxy resin composition.