Patent Publication Number: US-2003230817-A1

Title: Mold for UV curable adhesive and method of use therefor

Description:
TECHNICAL FIELD OF THE INVENTION  
       [0001] The present invention is directed, in general, to molds for forming three-dimensional articles and, more specifically, to a mold for forming a UV-cured article, and a method of use therefor.  
       BACKGROUND OF THE INVENTION  
       [0002] Fiberoptic technology continues to grow in importance and abundance, especially in the telecommunications industry. For example, the telecommunications industry employs fiberoptic technology for many uses, including data transmission and signal switching. Such uses conventionally employ fiberoptic assemblies having a number of fibers and optical components coupled to one another, wherein an optical signal may propagate along the transmissive cores centrally located within the fibers and optical components. However, connecting the fibers and optical components to one another to manufacture the fiberoptic assemblies has proven to be a difficult problem.  
       [0003] Conventional fiberoptic systems employ an epoxy or other adhesive between the parallel faces of adjoining fibers or components. However, by placing the epoxy in the optical path of the assembly, the risk of attenuating or otherwise disturbing the optical signal is unavoidable. Additionally, as the efficiency of modern optical systems continues to improve, the power of the optical signals propagating therethrough also increases. Unfortunately, this increased power may degrade the epoxy at the junctions between components, which may ultimately lead to system failure.  
       [0004] Further, it comes as no surprise that the fibers and optical components continue to decrease in size, making the coupling more and more difficult. Thus, it is also becoming increasingly difficult to grasp and secure the fibers and optical components to be assembled, and it is also extremely difficult to visually inspect progress during the subsequent application of adhesive or other coupling means.  
       [0005] Accordingly, what is needed in the art is a device and method that overcomes the disadvantages of the prior art in the assembly of fibers and optical components to one another in a fiberoptic assembly.  
       SUMMARY OF THE INVENTION  
       [0006] To address the above-discussed deficiencies of the prior art, the present invention provides a mold and a method of using a mold for forming a UV-cured article, the mold including a UV-transparent body having formed therein a mold cavity and an inlet, the inlet extending from an exterior surface of the UV-transparent body to the mold cavity. The mold cavity is configured to contain a UV-curable material, and the inlet is configured to supply UV-curable material to the mold cavity.  
       [0007] The foregoing has outlined preferred and alternative features of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art should appreciate that they can readily use the disclosed conception and specific embodiment as a basis for designing or modifying other structures for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the invention.  
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0008] The invention is best understood from the following detailed description when read with the accompanying FIGUREs. It is emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion. Reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:  
     [0009]FIG. 1 illustrates an end view of one embodiment of a mold constructed according to the principles of the present invention;  
     [0010]FIG. 2 illustrates a section view of another embodiment of a mold constructed according to the principles of the present invention;  
     [0011]FIG. 3 illustrates an elevation view of a fiberoptic assembly manufactured using the mold shown in FIG. 2; and  
     [0012]FIG. 4 illustrates a flowchart depicting a method of manufacturing a three-dimensional article according to the principles of the present invention.  
    
    
     DETAILED DESCRIPTION  
     [0013] Referring initially to FIG. 1, illustrated is an end view of a mold  100  constructed according to the principles of the present invention. The mold  100  includes a UV-transparent body  110 . In referring to the body  110  as UV-transparent, it is intended that ultra-violet (UV) radiation may pass through the body  110  without substantial diminution in power. Such UV radiation may, therefore, provide sufficient power to cure any UV-curable material (not shown) contained within the UV-transparent body  110 . Accordingly, the UV-transparent body  110  may comprise an aliphatic and/or polymeric material. For instance, the UV-transparent body  110  may comprise siloxane, hydrocarbon, flourocarbon, acrylate, methacrylate, epoxy functionalized siloxane, or acrylate functionalized siloxane. In one embodiment, the UV-transparent body  110  may comprise material having a surface energy less than about 25 mJ/m 2 . However, the present invention is not limited to use of such materials. The UV-transparent body  110  may also be translucent or, alternatively, include portions that are translucent. It is intended that the term “translucent” includes varying degrees of opaqueness, including substantially transparent.  
     [0014] In the illustrative embodiment shown, the UV-transparent body  110  includes a mold cavity  120  (shown in FIG. 1 by hidden lines) configured to contain a UV-curable material. In one embodiment, the mold cavity  120  may substantially conform to a shape of an element employed in fiberoptic systems, such as a gradient index lens (GRIN), a mounting sleeve (ferrule) and/or an end or length of a fiber, as described below with reference to FIG. 2.  
     [0015] In one embodiment, the mold cavity  120  may have a mold release material  130  deposited or otherwise formed on at least a portion of a surface thereof. The mold release material may include siloxanes, polytetrafluoraethylene, hydrocarbons and/or fluorinated hydrocarbons. An example of mold release material is Frekote® 4368, manufactured by Loctite®, located in Rocky Hill, Conn. In one embodiment, the mold release material  130  may substantially cover the surface of the mold cavity  120 .  
     [0016] The UV-transparent body  110  may also include an inlet  140  (shown in FIG. 1 by hidden lines) extending from an exterior surface  150  of the UV-transparent body  110  to the mold cavity  120 . The inlet  140  is configured to supply UV-curable material to the mold cavity  120 .  
     [0017] In the illustrative embodiment shown in FIG. 1, the mold  100  is removably coupled to a substrate  160 . The substrate  160  may be a built-up substrate, such as that conventionally used in semiconductor device fabrication. In one embodiment, the substrate  160  may be a wafer, such as that conventionally used in semiconductor and MEMS manufacturing. However, one having skill in the art understands that the substrate  160  may be any structure or device adapted to cooperate or engage with the mold  100  to contain UV-curable material in the mold cavity  120 .  
     [0018] The mold  100  may be removably coupled to the substrate  160  by various means, including, but not limited to, by adhesive tape  170  or by a mechanical clip  175  of course, other means for removably coupling the mold  100  to the substrate  160  are within the scope of the present invention. In one embodiment, the mold  100  may be permanently couplable to the substrate  160 , rather than removably couplable. The mold  100  may also be positioned and held in place by conventional pick-and-place apparatus. In such pick-and-place embodiments, as well as other embodiments, the structure interfacing with the mold  100 , such as that schematically represented by member  180 , may also be UV-transparent.  
     [0019] Turning to FIG. 2, illustrated is a section view of a mold  200  constructed according to the principles of the present invention. The mold  200  may comprise a UV-transparent body that includes one or more portions, wherein at least one portion includes UV-transparent material, as discussed above with regard to FIG. 1. In the illustrative embodiment shown in FIG. 2, however, the mold  200  includes a first portion  210  and a second portion  220 . The second portion  220  may be removably couplable to the first portion  210 , such as by adhesive or mechanical clamps or fasteners. An exemplary clamp  230  is shown.  
     [0020] As shown in FIG. 2, the first portion  210  may have a first cavity  240  formed therein, and the second portion  220  may have a second cavity  250  formed therein. The coupling of the second portion  220  to the first portion  210  defines a mold cavity adapted to contain UV-curable material. In one embodiment, the first and second portions  210 ,  220  may have multiple cavities  240 ,  250  formed therein, such that the coupling of the two portions  210 ,  220  defines multiple mold cavities.  
     [0021] The mold  200  also includes an inlet  260  that extends from an exterior surface  265  of one of the UV-transparent body portions  210 ,  220  to the mold cavity defined by the cavities  240 ,  250 . The inlet  260  may be used to supply UV-curable material to the mold cavity defined by the cavities  240 ,  250 . The UV-curable material may have a viscosity ranging between about 100 cps and about 200,000 cps at room temperature, depending on the end use requirements (e.g., high viscosity to reduce resin from flowing into the fiber ferrule/GRIN gap). In an advantageous embodiment, the UV-curable material may have a viscosity ranging between about 60,000 cps and 80,000 cps at room temperature. In one embodiment, the inlet  260  may be used to inject UV-curable adhesive into the mold cavity.  
     [0022] As shown in the illustrative embodiment of FIG. 2, the mold  200  may be used to bond fiberoptic components to one another. For instance, a mold cavity defined by the cavities  240  and  250  may be adapted to form an injection mold of an annulus of UV-curable adhesive around an end joint between an optical fiber  270  and a gradient index lens (GRIN)  280 . Another mold cavity defined by the cavities  240  and  250  may be adapted to form an injection mold of an annulus of UV-curable adhesive around a butt joint between the GRIN  280  and a mounting sleeve  290 . The resulting fiberoptic assembly is shown in FIG. 3, wherein an adhesive annulus  310  surrounds the joint between the fiber  270  and the GRIN  280 , and another adhesive annulus  320  surrounds the joint between the GRIN  280  and the mounting sleeve  290 . In this manner, fiberoptic components may be joined without requiring or permitting adhesive in between the components. Of course, one of ordinary skill in the art understands that these exemplary uses of the mold  200  are not limiting examples, and that the mold  200  may be used in myriad other applications within and beyond the arena of fiberoptic assembly.  
     [0023] Turning to FIG. 4, illustrated is a flowchart depicting a method  400  of manufacturing a three-dimensional article according to the principles of the present invention. The method  400  begins with a step  410 , wherein a UV-transparent body is provided. As discussed above in reference to FIGS. 1 and 2, the UV-transparent body has formed therein a mold cavity for containing a UV-curable material and an inlet for supplying a UV-curable material to the mold cavity. The UV-transparent body may comprise multiple portions, and may contain multiple cavities.  
     [0024] The method  400  may continue at a step  450 , wherein a UV-curable material is deposited in the mold cavity or cavities located in the mold. In one embodiment, the UV-curable material may be an adhesive. An example of UV-curable material is Optocast 3410 epoxy manufactured by Electronic Materials, Inc., having a principal place of business in Breckenridge, Colo.  
     [0025] The method  400  may conclude at a step  460 , wherein the UV-curable material is exposed to UV radiation through the UV-transparent body. In one embodiment, such exposure may include exposing the UV-curable material to about 270 J/cm 2  of UV light of course, such exposure may be performed at other energy levels, including from about 90 J/cm 2  up to about 270 J/cm 2 .  
     [0026] The step  460  may also include irradiating the UV-curable material with a pulsating signal. Such a pulsating signal may have a UV radiation level ranging between about 1000 mw/cm 2  and infinity. In one embodiment, the pulsating signal may have a UV radiation signal ranging between about 2000 mW/cm 2  and about 20,000 mW/cm 2 . In an advantageous embodiment, the pulsating signal may have a UV radiation level ranging between about 3000 mW/cm 2  and about 6000 mW/cm 2 . It should be noted that such a pulsating signal may have a frequency between about 0.03 Hz and about 20 Hz. Those skilled in the art understand the motivation for pulsating the signal. For example, it is known that the signal may be pulsated to dissipate heat energy, as well as minimize residual stresses in the adhesive bond that may originate from differences in the coefficient of thermal expansion between the substrates.  
     [0027] The method  400  may include various other steps in addition to those described above. For instance, the method  400  may include a step  420 , wherein a mold release material is deposited or otherwise formed on all or a portion of a surface of the mold cavity formed in the UV-transparent mold. Step  420  may be particularly advantageous in embodiments employing an especially complex or intricate mold cavity. However, in some embodiments, the UV-transparent mold provided in the step  410  may be provided with mold release material already covering all or a portion of a surface of the mold cavity. In such embodiments, the step  420  may not be executed.  
     [0028] The method  400  may also include a step  430 , wherein one or more components may be assembled in the mold cavity or cavities prior to filling the cavities with the UV-curable material. For instance, as discussed above with regard to FIGS. 2 and 3, several components of a fiberoptic assembly may be assembled into the mold in the step  430 . The fiberoptic components may, for example, be a GRIN lens, a fiberoptic fiber, a fiber mounting sleeve or ferrule, or other similar components.  
     [0029] In one embodiment, the method  400  may also include a step  440 , wherein the UV-transparent body provided in the step  410  comprises multiple portions. In such an embodiment, the step  440  may include coupling the multiple portions of the UV-transparent body to one another, thereby defining one or more mold cavities located therein. Such coupling may be accomplished via mechanical fasteners, adhesives, or other conventional means, and may be removable or permanent.  
     [0030] The method  400  may also include a step  470 , wherein the UV-transparent body provided in the step  410  is removed from around the cured UV-curable material deposited in the step  450 . Alternatively, the step  470  may include removing the cured UV-curable material deposited in the step  450  from within the UV-transparent body provided in the step  410 . However, the step  470  is an optional step, such that the method  400  may not include separating the cured UV-curable material from the UV-transparent body.  
     [0031] Although the present invention has been described in detail, those skilled in the art should understand that they can make various changes, substitutions and alterations herein without departing from the spirit and scope of the invention in its broadest form.