Applicable Business AreasSilicon Photonics / Optical Transceivers & Optical Modules, CPO Packaging (Semiconductors / Advanced Photonic Packaging)
Target ApplicationsAdhesive bonding for Fiber Coupling, fixation for FAU–PIC Assembly, fixation after optical path connection and optical component alignment
In optical circuit assembly for silicon photonics, optical modules, and CPO applications, the use of adhesives is being considered for Fiber Coupling and FAU–PIC Assembly. Since the optical coupling interface is a critical factor governing the overall reliability of the module, adhesives are required to simultaneously satisfy "rapid curing," "optical properties," and "assembly reliability." Conventional UV-cure optical adhesives excel in short curing times but may present challenges in terms of durability. Thermally cured adhesives and conventional UV/thermal dual-cure adhesives, on the other hand, tend to offer better reliability but can impose constraints on productivity.
The RA-Series (Under Development) from Resonac is a UV-cure optical adhesive that cures with short UV irradiation and is well suited for fixation after optical path connection and optical component alignment. It offers a well-balanced combination of high transmittance in the 1310 nm band, a refractive index suited for optical coupling applications, high shear strength, and assembly reliability, enabling both assured optical coupling precision and takt time reduction.
Fig. 1. Development targets of the RA-Series
In advanced photonic packaging — particularly for silicon photonics, optical transceivers and optical modules, and CPO optical circuit assembly — it is essential to secure optical coupling precision by rapidly fixing components after fine alignment and suppressing positional or optical-axis displacement after curing.
In addition to high transmittance in the 1310 nm band and a refractive index suited for optical coupling, assembly reliability is also required, including adhesion strength, reflow resistance in subsequent processes, and resistance to long-term high-temperature /high-humidity environments. With conventional adhesives, prioritizing curing speed tends to result in insufficient durability, while prioritizing assembly reliability leads to increased curing time and process steps, reducing productivity.
The RA-Series adopts a curing design that combines short-time UV pre-fixation with final thermal cure, making it compatible with optical component assembly processes that use both UV pre-fixation and thermal final cure, while enabling assured assembly reliability. In Fiber Coupling and FAU–PIC Assembly, it contributes to takt time reduction in high-volume production processes while reducing optical loss and supporting stable long-term optical coupling.
Fig. 2. Sample supply form of the RA-Series
*The data shown are representative values that represent examples of the results of measurements, calculations, etc., and are not guaranteed values.
The RA-Series employs a two-stage cure process combining UV irradiation at 100 mW/cm², 20 seconds with thermal cure at 150 °C for 30 minutes. It enables rapid pre-fixation and allows takt time reduction in optical component assembly processes.
Fig. 3. Curing conditions of the RA-Series
| Item | RA-302C | Remarkes |
|---|---|---|
| Curing Process | UV＋Thermal | ― |
| Curing Conditions | 100 mW/cm², 20 s ＋ 150 °C, 30 m | LED：365 nm in air |
*The data shown are representative values that represent examples of the results of measurements, calculations, etc., and are not guaranteed values.
In transmittance characteristics measured on a cured film with a thickness of 50 μm, transmittance exceeding 99 % was demonstrated across a broad near-infrared range from 800 nm to 1550 nm. This suggests that reduction of optical loss in the 1310 nm band can be expected.
Fig. 4. Transmittance characteristics
*The data shown are representative values that represent examples of the results of measurements, calculations, etc., and are not guaranteed values.
In high-temperature/high-humidity testing at 85 °C/85% RH, no significant reduction in shear strength was observed after 1,000 hours, and transmittance at 850 nm and 1310 nm was maintained at a level equivalent to the initial values. These results suggest that assured assembly reliability can be expected.
Fig. 5. High-temperature/high-humidity durability: 85 °C/85 % RH
(a)Die shear Strength
(b)Transmittance
*The data shown are representative values that represent examples of the results of measurements, calculations, etc., and are not guaranteed values.
Update date: 14th July, 2026
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