1、 TSB-4947 August 2015Guidance for Adhesive Usage in Fiber Optic Components NOTICE TIA Engineering Standards and Publications are designed to serve the public interest through eliminating misunderstandings between manufacturers and purchasers, facilitating interchangeability and improvement of produc
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19、DVISED OF THE POSSIBILITY OF SUCH DAMAGES. THE FOREGOING NEGATION OF DAMAGES IS A FUNDAMENTAL ELEMENT OF THE USE OF THE CONTENTS HEREOF, AND THESE CONTENTS WOULD NOT BE PUBLISHED BY TIA WITHOUT SUCH LIMITATIONS. TIA-TSB-4947 i TSB-4947 Guidance for Adhesive Usage in Fiber Optic Components Contents F
20、OREWORD. IV 1 INTRODUCTION 1 2 SCOPE . 1 3 BACKGROUND 1 4 IMPACTS 2 5 ADHESIVE SYSTEMS OVERVIEW . 2 6 KEY PROPERTIES 3 7 LIMITED LIFE . 4 8 CLEANING/CLEANLINESS/CONTAMINATION 4 9 STOICHIOMETRY 5 9.1 Weighing . 5 9.2 Mixing . 6 10 CURING 7 10.1 Two-Part Adhesives . 7 10.2 Light Cureable Adhesives 8 1
21、0.3 Anaerobic & Cyanoacrylate Adhesives 9 10.4 Others . 10 11 FLUID STATE APPLICATION . 11 TIA-TSB-4947 ii 12 ENVIRONMENTAL TESTING . 11 13 ACCELERATED AGING 12 14 OPTICAL BONDING 12 15 INDUSTRY CHALLENGES 13 16 REFERENCES . 13 TIA-TSB-4947 iii This page left blank. TIA-TSB-4947 iv TSB-4947 Guidance
22、 for Adhesive Usage in Fiber Optic Components Foreword From TIA Project No. TIA-PN-4947, formulated under the cognizance of TIA TR42-13 Subcommittee on Passive Optical Devices and Fiber Optic Metrology This ITM is part of the series of test methods included within TIA/EIA TSB-YY. There are no annexe
23、s. Key words: Fiber Optics, Fiber Optic Component Reliability, Fiber Optic Connector Reliability, Fiber Optic Adhesive Reliability, Fiber Optic Epoxy Reliability, Fiber Optic Polymer Reliability Adhesive, Fiber Optic Adhesive, Fiber Optic Epoxy, Fiber Optic Polymer, Optical Adhesive Adhesive Guidanc
24、e, Adhesive Usage, Adhesive Guidance and Usage, Epoxy, Guidance, Epoxy Usage, Epoxy Guidance and Usage Polymer, Fiber Optic Polymer, Polymer Guidance, Polymer Usage, Polymer Guidance and Usage Polymeric, Fiber Optic Polymeric, Polymeric Guidance, Polymeric Usage, Polymeric Guidance and Usage TIA-TSB
25、-4947 v This page left blank. TIA-TSB-4947 1 1 Introduction This bulletin provides general information and guidance on adhesive usage for fiber optic components and devices. The primary intent of the document is to present the most commonly observed adhesive usage pitfalls and ways to avoid them. Be
26、st practices, issues, and industry challenges relevant to the telecommunications, military, and aerospace sectors are discussed. 2 Scope The bulletin is applicable to fiber optic component reliability. The document is written for fiber optic component manufacturers, as well as end-users, and was pre
27、pared by TIA Working Group TR-42.13.1, Adhesives Reliability under the cognizance of SC TR 42-13 Subcommittee on Passive Optical Devices and Fiber Optic Metrology. 3 Background Adhesives are widely used in the manufacture of fiber optic component assemblies including connectorized cables and pigtail
28、s, fiber optic branching devices (couplers and splitters), and active devices (sources and detectors). Some important functions that adhesives perform within assemblies are precision alignment, fastening, and optical transmission. Users are often unaware that they may have adversely altered adhesive
29、 final properties via their handling processes and procedures. Take the process of heat curing for example. A user may cure an assembly exactly per the manufacturers time and temperature specifications, but inadvertently overlook the fact that the adhesive never reached the required temperature beca
30、use of assembly and equipment thermal gradients. The performance of an under cured adhesive can differ greatly from one that is properly cured. Because of the critical functions that adhesives perform in fiber optic components, care needs to be taken in all aspects of adhesive usage as the example p
31、oints out. TIA-TSB-4947 2 4 Impacts Bond strength, mechanical stress, and material characteristics are a few properties that can be inadvertently altered by users via their handling processes and procedures. Because cured adhesives become an integral part of an assembly structure, altered adhesive p
32、roperties can result in undesirable or unanticipated conditions that may result in serious performance and reliability issues. Optical performance can be adversely affected when an improperly cured adhesive causes a fiber to move or shift its position. In polarization maintaining (PM) fiber applicat
33、ions, adhesive problems can create non-uniform stresses that result in a change of polarization directions. Lastly, system optical bit-error-rates can change due to variations in light levels when alignment adhesives are not stable over environmental conditions. 5 Adhesive Systems Overview Definitio
34、ns For the purposes of this Standard, the following definitions apply. Multipart Epoxies: thermosetting epoxide polymer that cures (polymerizes and crosslinks) when mixed with a catalyzing agent or hardener. Urethane Adhesives: can be one component that cures when exposed to moisture in the air or t
35、wo components in which a catalyst is added. Silicone Adhesives: can be one component that cures when exposed to moisture in the air or two components in which a catalyst is added. Light Curable Adhesives: one component prepolymer that crosslinks on exposure to UV light and/or visible light. Cyanoacr
36、ylate Adhesives: one component adhesive that polymerizes in the presence of moisture. Anaerobic Adhesives: one component adhesive that polymerizes when air (oxygen) is excluded from being in contact with the adhesive. TIA-TSB-4947 3 Structural Acrylics: an acrylate based adhesive which is applied to
37、 one substrate with an activator applied to the other. When joined, the adhesive cures. 6 Key Properties There are many adhesive properties. The properties listed below, however, are most commonly altered by users via their handling processes and procedures. Coefficient of Thermal Expansion (CTE) is
38、 defined as the “change of length of a material for a unit of change in temperature.” As materials are heated, they expand at a given rate. This rate can vary from one adhesive to another but is usually around 50-100 ppm (parts per million) for every C provided there is no filler in the adhesive. Fi
39、llers can drastically change the CTE. The CTE is different above and below the materials Glass Transition Temperature. Glass Transition Temperature (Tg) is a midpoint of the range where a material changes from a glassy to a rubbery solid. Over this range, the materials CTE also changes. The CTE chan
40、ge varies with each product. The physical characteristics will typically change at this transition temperature. Some products have very small changes, and, in others, the change can be quite large. An epoxy will often be hard (glassy) below the Tg and soft and flexible (rubbery) above the Tg. When h
41、igh pressure or external forces are involved in the bonded application, there is a concern regarding temperature cycling through a materials Tg. In fiber optic connectors, it is possible that above the Tg, the adhesive can soften enough to cause the fibers to be pushed back into the connector. In th
42、ese cases, where high force is involved, a Tg above the maximum cycle temperature is usually required. If no extraordinary external forces are involved, the Tg may not be as critical and in fact a softer, more resilient adhesive may be advantageous. Hardness is a measure of the resistance of materia
43、l to deformation usually tested by indentation. The most popular test method involves the use of a Shore durometer tester. The Shore D scale is used for rigid material (Shore A is used for flexible materials such as silicones). A Shore D hardness above 70 to 75 is required for fiber optic communicat
44、ions applications where the material needs to be polished. Below 70, materials will smear during polishing and will be difficult to cleanly remove from the surface. Very rigid material can become brittle and may take more effort to remove. These brittle materials may also fracture during polishing.
45、Viscosity is a measure of the resistance to flow. The unit of measurement for viscosity is centipoise (cps), and it is based on water = 1 cps at 23C (room TIA-TSB-4947 4 temperature) and 1 atmosphere (at sea level). The higher viscosity a material is, the thicker it appears. Viscosity is an importan
46、t parameter in terminations. A material that is too low in viscosity may drip or wick whereas a high-viscosity material may be too hard to apply. A specific adhesive property related to viscosity is Gel Time. It is the time required for an adhesive to go from a liquid to a gel state. It is important
47、 not to apply adhesive after it gels. A gelled material will not produce a good bond. Bond strength This is usually determined by a lap shear test and is expressed in pounds/inch2. For adhesion to glass, a double lap shear configuration is preferred. 7 Limited Life Shelf Life - As most adhesives are
48、 perishable, manufacturers will give the material a limited shelf life. This is usually based on storage at room temperature. Higher storage temperatures will cause most adhesives to degrade more rapidly. Most products should be stored in a cool, dry area, with some manufacturers recommending refrig
49、eration to maintain the highest quality. (Note: If refrigeration is used, always allow adhesive to come to room temperature before opening the adhesive package to prevent moisture condensation from occurring.) The shelf life given to the adhesive is the manufacturers warranty on the product. Pot life and Working life - The term “Pot Life” is used to describe the time necessary for a material to double in viscosity. This may or may not correspond to the actual working time of the adhesive. Working time is based upon how quickly the adhesive increases in viscosity and can
