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LED (Light Emitting Diode) devices have advantages such as high efficiency, low power consumption, and high durability, and are widely used in large displays, traffic signals, and lighting. With the rapid development of LED application technology, the performance requirements for packaging materials are also increasing.
Thermosetting epoxy resins offered by Tetra, one of the top cycloaliphatic epoxy resin manufacturers, have good mechanical properties, low curing volume shrinkage, excellent adhesion to substrates, and strong controllability of the process, making them one of the important packaging systems for LEDs. Among them, cycloaliphatic epoxy resins, especially 3,4-Epoxycyclohexyl-3,4-epoxycyclohexane-carboxylate (TTA21), are preferentially and widely used in LED and optical device encapsulation adhesives due to their excellent processing properties, high Tg point, and good weather resistance.
It should be noted that the curing crosslinking strength of cycloaliphatic epoxy resins is very high, and it is easy for the cured material to crack due to excessive internal stress, thus limiting the product's performance (in the packaging process, moisture absorption and mechanical stress are the two main factors affecting the reliability of the product, with mechanical stress being due to curing stress and cooling stress caused by coefficient of thermal expansion (CTE) mismatch). Usually, in actual applications, they are paired with Bisphenol-A type epoxy resins (or hydrogenated Bisphenol-A type epoxy resins) to adjust system toughness. Below is a brief analysis of the basic characteristics comparison when resins are paired.
| Resin Type | Bisphenol A Epoxy Resin | Cycloaliphatic Epoxy Resin |
| Resin Structure |  |  |
| Performance Comparison | The cured product has good toughness and good reaction activity with amines | Low viscosity, no chloride ions, excellent electrical properties, high transparency of the cured product, high reactivity with cationic |
Viscosity-Temperature Curve of TTA21 and E51 Type Epoxy Resin
Temperature curve
E51: Bisphenol-A type epoxy resin (epoxy equivalent 184~194g/eq)
Structural formula:
As can be seen from the figure, the viscosity of both resins decreases with increasing temperature, with Bisphenol-A epoxy itself having a larger viscosity and corresponding larger change in viscosity, which is a factor to consider in formulation design.
Relationship Between TTA21 Mixing Ratio and Viscosity (25℃)
EP-4080: Hydrogenated Bisphenol-A epoxy resin (epoxy equivalent 205g/eq, viscosity 1800mPa·s)
Structural formula:
As can be seen from the figure, when an appropriate amount of TTA21 is added to E51 and EP-4080, the viscosities of both significantly decrease, showing that TTA21 can serve as a diluent for high-heat-resistant epoxy resins.
| Component | Proportion | Curing Conditions |
| Epoxy Resin | 100 | Initial Curing: 110°C, 2 hours |
| Ethylene Glycol | 1 | Post Curing: 180°C, 2 hours |
| MH-700/Epoxy Ratio | 0.6~0.9 | - |
| Catalyst | 0.5 |
It can be clearly seen that under the same conditions, cycloaliphatic epoxy resins exhibit better heat resistance, while Bisphenol-A type epoxy resins perform better in terms of water absorption and flexural strength.
Cycloaliphatic epoxy resins display good transparency and heat resistance, making them suitable for high-requirement LED epoxy encapsulation applications, aligning with market performance.
Cycloaliphatic epoxy resins demonstrate a significant effect in reducing viscosity in formulations and can be effectively paired with regular epoxies to enhance overall performance while effectively controlling viscosity, providing greater operational flexibility.
Considering the differences in water absorption and mechanical strength, the formulation should reasonably mix the ratios of various epoxy resins based on actual performance needs.
Discover the superior performance of specialty epoxy resins offered by Tetra, designed to meet the most demanding industrial and commercial applications.
