EPO-TEK® 323LP Extended Pot Life High Temperature Optical Epoxy, Heat Cure (2.5g Packet)

EPO-TEK® 323LP is a premium two-part heat-cure optical epoxy designed for demanding fiber optic, photonics, semiconductor, hybrid microelectronics, and electronic assembly applications. Developed as an extended working life alternative to EPO-TEK® 353ND, it provides exceptional thermal stability, optical transmission, and long-term reliability while offering an industry-leading 24-hour pot life.

Its low-viscosity formulation enables excellent wetting, capillary flow, and optical bonding performance, making it ideal for fiber optic packaging, ferrule bonding, active optical alignment, and precision photonic assemblies. With outstanding optical transmission across visible and near-infrared wavelengths, EPO-TEK 323LP is an excellent choice for applications requiring both high optical performance and extended processing time.

Supplied in a convenient 2.5-gram packet for accurate mixing and reduced material waste.

Features and Benefits

Ultra-Long 24-Hour Working Life

Provides significantly longer processing time than conventional optical epoxies, making it ideal for complex assemblies, extended alignment procedures, and batch manufacturing.

High Temperature Performance

Designed for demanding environments and capable of withstanding field conditions exceeding 200°C.

Excellent Optical Transmission

Provides outstanding transmission performance across visible and near-infrared wavelengths commonly used in fiber optic communication systems.

Visual Cure Verification

Changes to an amber color after curing, allowing easy confirmation of proper processing.

Designed for Fiber Optic Applications

Developed to meet Telcordia GR-1221 requirements for fiber optic component packaging and assembly.

Strong Mechanical Performance

Offers high shear strength, excellent durability, and long-term environmental stability.

Electrically Insulating

Suitable for electronic packaging, dielectric applications, and electrical insulation requirements.

Low Viscosity for Precision Bonding

Flows easily into ferrules, optical assemblies, and small cavities where controlled wetting is required.

Technical Specifications

• Product Type: Two-Part Heat Cure Optical Epoxy

• Package Size: 2.5 g Packet

• Consistency: Pourable Liquid

Color Before Cure

• Part A: Clear to Slight Yellow

• Part B: Yellow

Physical Properties

• Viscosity at 23°C: 3,500 to 5,000 cPs

• Glass Transition Temperature (Tg): ≥ 100°C

• Shore D Hardness: 88

• Storage Modulus: 444,110 psi

• Suggested Operating Temperature:

  • Up to 300°C Intermittent

Mechanical Properties

• Lap Shear Strength at 23°C: Greater Than 2,000 psi

• Die Shear Strength at 23°C: ≥ 20 kg (7,112 psi)

Coefficient of Thermal Expansion (CTE)

• Below Tg: 51 × 10⁻⁶ in/in/°C

• Above Tg: 185 × 10⁻⁶ in/in/°C

Thermal Weight Loss

• 0.31% at 200°C

• 0.46% at 250°C

• 0.85% at 300°C

Electrical Properties

• Volume Resistivity at 23°C: ≥ 3 × 10¹² Ohm-cm

• Dielectric Constant (1 kHz): 2.62

• Dissipation Factor (1 kHz): 0.003

Optical Properties

Spectral Transmission

• ≥ 90% at 640–800 nm

• ≥ 94% at 820–1620 nm

Refractive Index

• 1.5704 at 589 nm

Handling and Processing

• Working Life (Pot Life): Up to 24 Hours

• Recommended Cure Schedule: 150°C (302°F) for 1 Hour

Typical Applications

Fiber Optic and Photonics Applications

• Fiber ferrule bonding

• Fiber optic connector assembly

• Fiber optic component packaging

• Active optical alignment

• V-groove array assembly

• Optoelectronic package sealing

• Optical sensor packaging

• Light transmission applications from 800–1550 nm

Semiconductor Applications

• Wafer-to-wafer bonding

• Chip scale package (CSP) assembly

• MEMS fabrication

• Flip-chip underfill

Hybrid and Sensor Applications

• Near-hermetic sealing

• Ultra-high vacuum sensor packaging

• High-temperature sensor assemblies

• Down-hole fiber optic sensing systems

Electronics Assembly

• Capacitor fabrication

• PZT piezoelectric lamination

• Motor winding insulation

• Inductor coil impregnation

• Ferrite core bonding

• Magnet bonding

Why Choose EPO-TEK 323LP?

EPO-TEK 323LP combines excellent optical transmission, high-temperature performance, and exceptional reliability with an extended 24-hour working life. For applications requiring maximum assembly time, precision optical alignment, or large-scale production processing, it offers one of the longest pot lives available among high-performance optical epoxies.

Storage and Shelf Life

Store refrigerated according to the manufacturer's recommendations to maximize shelf life and maintain optimum performance.