Selecting the right epoxies and adhesives and using them properly is essential for ensuring long-term product reliability. In addition to the strong, reliable, and durable bonds they provide, protection of optical fibers, connectors, and components are just as critical in fiber optics. Fiber Optic Center (FOC) has a dedicated Epoxy Expert on their technical team due to the selection and application of the epoxy and adhesive materials being so critical.
Step one is determining the epoxy, adhesive or fiber coating that best fits the specific termination or application. Optical properties impact the performance of components including but not limited to refractive index, viscosity, Tg (°C), pot life, and operating temp/CTE. The FOC Termination Epoxy Matrix and UV Curable Optical Adhesive or Fiber Optic Coatings Matrix offer these properties in a comparison format for each material option. The use of an inappropriate material or incorrect application is a direct source of reliability and quality failures.
Step two, after selecting the right material, is packaging selection. Many applications are very small, not requiring large quantities of material, so avoiding waste is an important part of the equation. The determining factor of which epoxy packaging is right for you will be the amount of handling you intend to include in the epoxy application process. Materials are offered in 2-Part Packets (bi-packs) and Premixed & Frozen.
2-Part Packets (bi-packs) are the solution for minimal waste and proper mix ratio objectives. All FOC packaging maintains a strict mix ratio of at least +/- 1% and are highest quality to ensure avoiding failures during operation and consistency throughout their shelf life. Usage tips and step-by-step instructions for epoxy bi-packs are always provided. Premixed & Frozen adhesives are pre-weighed, de-aired and flash frozen to ensure performance. Loaded in syringes or cartridges, freezing guarantees maximum working time.
Proper technical consultation for material selection including curing needs between Room Temperature Cure, Extended Use Heat Cure, Quick Cure Field Termination, UV Cure and Specialty Needs. In the field, protection from environmental factors like moisture, dust, and contamination need to be considered.
The glass transition, Tg, is the temperature at which cured epoxies transition from a state of being rigid and glassy (maintaining desired bonding quality) to being rubbery and more flexible (degrading in bonding quality). A higher Tg allows for a higher operating temperature for the cured epoxy. The Tg is not a well-defined single temperature and of any given cured epoxy, as it is dependent on the curing procedure.
Not all epoxies are suitable for all applications, and our partnership with the industry’s highest quality manufacturers including, by not limited to ÅngströmBond®, Dymax, Epo-Tek, Hernon, Hysol and Covestro (formerly DSM) for coatings, help us provide you with the best advice for your needs.
Fiber Optic Center notes that ÅngströmBond®, Advanced Polymers for High-Tech Applications, a type of adhesive specifically designed for use in the fiber optics industry, has excellent chemical and temperature resistance, as well as good adhesion to a wide range of substrates, including metals, ceramics, and plastics. ÅngströmBond, a two-part, room-temperature-curing epoxy commonly used for bonding and potting optical components, such as fiber optic connectors, couplers, and isolators, has a low viscosity. This property of low viscosity allows it to be easily dispensed and provides good wetting of fiber surfaces, ensuring a strong bond.
With the goal to supply the best possible material for the customers’ application and minimize the typical adhesive related problems such as defective epoxy, incorrect mix ratio by packagers or users, expired or beyond working life issues, and incorrect cure schedules, ongoing education includes:
- storage (temp, light) best practices
- crystallization solutions and information
- how to minimize allergic reactions when handling epoxies
Epoxy, being a permanent adhesive, requires removal methods and strategies. When a break is necessary for a bond, a bond failure or adhesive fail is necessary. Choosing a removal method depends on the substrate and what it can withstand as well as the specific epoxy. Options included heating, temperature cycling/shocking, hot water soak and chemical bath.
In addition to epoxy and adhesive materials playing a critical role in reliable optical connections, the equipment such as dispensing, curing and mixing as well as the supplies like syringes, tips, pistons, barrels and plungers are equally important.
Curing Equipment
Epoxy Curing equipment selection is critical for ensuring fiber performance. Some oven-design variables to consider include top loading vs horizontal loading, fixed temperature vs ramped and UV-cure adhesives specific needs. The Fiber Optic Center technical Team provides consultation for curing equipment selection based on the specific type of epoxy being used and UV light to heat requirements.
This consultation includes developing and validating curing schedules from setting up a net new bonding process to adjusting a current production process. Most epoxy curing issues stem from improper mixing, poor cleaning procedures or issues with curing temperatures. A best practice is to periodically measure the temperature in ALL oven ports to ensure curing temperature consistency and stability.
Dispensing Equipment
Historically, dispensing methods and their level of automation are determined based on order quantities, connector types, and workflow criteria. In our previous article, Epoxy Dispensing Explained, it is noted that the primary objective of a dispensing system is simply to inject a consistent and controllable amount of adhesive into the ferrule and connector.
When using an automatic dispensing machine, further costs can be saved and product consistency improved with either the pre-weighed packets or the premixed and frozen packages. A system can be devised which can reduce operator variability to ensure the same amount of adhesive is injected each time. The unit will also decrease the repetitive motion that can sometimes lead to Carpal Tunnel Syndrome. Premixed and frozen can be packaged in an automatic cartridge that fits your dispensing machine, thus adding to your savings. The Epoxy Dispensing Equipment Selection Process evaluates the manual option, recommended for low-viscosity epoxies, and the automated options, recommended for higher viscosity epoxies that include Pneumatic, Volumetric and Robotic Dispensers.
Best practices for preparing and dispensing epoxy are critical in the assembly process determining product long-term reliability. The Fiber Optic Center Technical Team provides consultation on the exact type of dispensing equipment best suited for specific applications and the viscosity of the epoxy being used.
Centrifuge and Mixing Equipment
The critical steps for epoxy centrifuge and mixing equipment are centrifugation, mixing, degassing, dispensing and curing. Proper centrifugation of epoxy is critical to remove air bubbles and ensure that the resin and hardener are well mixed. Because air bubbles MUST be removed prior to injection into connectors, the Fiber Optic Center Technical Team offers consultation on recommended speed and time to obtain a bubble-free, homogeneous mixture. Additional information is available in the article, Defeating Bubbles.
Mixing, which ensures consistency, of the resin and hardener at the recommended ratio and order is what achieves a complete chemical reaction. Appropriate ratios and proper Epoxy Mixing and Centrifuge equipment are key.
Syringes, Tips, Pistons and Barrels
In addition to the epoxy and adhesive materials and equipment are supplies that are equally important including syringes, tips, pistons and barrels.
Syringes provide precise and controlled dispensing of epoxies. This is critical In fiber optic applications, where finite amounts of adhesive are used and precision ensures the fibers are not damaged. They can be fitted with different types of tips and needles and customized to produce consistent and high-quality results.
Tips must be matched with the epoxy being used based on gauge size for proper dispensing. The Fiber Optic Center Technical Team provides consultation for choosing the right type of tips for the syringe, proper cleaning and techniques for attaching the tips to the syringe without air bubbles or leakage.
Pistons and barrels transfer the epoxy material from syringe to application site, impacting the consistency of the epoxy and ultimately the final product quality. The Fiber Optic Center Technical Team provides consultation for selection to ensure compatibility with the epoxy material being used for consistent and accurate dispensing.
Additionally, epoxy and adhesive materials used as coatings for optical fibers provide protection against mechanical stress, temperature changes, and improved reliability. Regarding pigments for UV curable coatings, FOC provides consultation for material selection, ratios of pigment to coating and best practices to avoid compromising coating integrity and best practices specifically for Covestro (formerly DSM) coating products.
Fiber Optic Center (FOC) has created an Epoxy Library of articles, blogs, tips, FAQs videos and technical papers as a resource for the latest information and best practices being developed daily.
With selection and application of the epoxy and adhesive materials being so critical, a complete property matrix has been created for the following:
Termination Epoxy Matrix
- Single Fiber, Single Mode And Multimode Terminations Product
- Multi-Fiber, MT And MT-RJ Terminations
- Plastic Fiber Terminations
- Field Termination, Quick Cure Product
UV Curable Optical Adhesive or Fiber Optic Coatings Matrix
We invite you to explore the Fiber Optic Center Technical Content Library for answers to your most pressing epoxy questions. Search a comprehensive database of resources, including technical papers, best practices, tips, FAQs, and more. Timeless top topics include:
- Helpful Epoxy Tips for the Cable Assembly Process
- Ideas to Adjust Your Epoxy Process: Recommendations to Reduce Waste (And Save Money) In Your Fiber Optic Cable Assembly Process
- Bond Line Thickness & More: Answers to Common Epoxy Questions
- Does Epoxy Cause Core Cracking? Tips to Identify and Prevent This Phenomenon
Our world is about helping YOU select the right epoxies and adhesives and have the latest knowledge for using them properly. Epoxy selection is essential for ensuring long-term product reliability and Fiber Optic Center is for reliability in a partner.
