Abstract:
A method and apparatus are disclosed for forming a resin-impregnated fiber web that is particularly suitable for use in reinforced plastic composites and printed circuit board applications. The method includes the steps of drawing machine direction yarns from multiple spools contained in creels arranged around a hollow cylinder; passing machine direction yarns from the creels through a circular reed; pulling machine direction yarns the length of the hollow cylinder&#39;s outer surface in a longitudinal direction; controlling the application of an uncured or partially cured thermoset or thermoplastic resin to the yarns as they travel the length of the hollow cylinder; winding cross-direction yarns around the periphery of the hollow cylinder (i.e., on top of the machine direction yarns) thereby forming a web; heating and cooling the resulting web; and finally collecting the web on a roll. In its apparatus aspects, the invention includes a hollow cylinder, a creel surrounding the hollow cylinder for supporting machine direction yam, a resin heater and pump for heating and pumping the resin to a resin manifold for applying resin to the yarns, a controller for controlling the speed of the machine direction yarns and the amount of resin applied to the yarns, a rotating disk supported by a support ring and powered by electromagnetic actuators, a yarn supply containing cross-direction yarns supported by the rotating disk, circular heaters for partially curing the resin saturated yarns located around the periphery of the cylinder, and a slitter for cutting the resin-impregnated fiber web into separate sections.

Description:
FIELD OF THE INVENTION 
     The invention relates to a method and apparatus for making a resin-impregnated fiber substrate suitable for use in a variety of fabrication processes and particularly suitable for use in reinforced plastic composites and printed circuit board applications. More particularly, the invention pertains to a method and an apparatus for forming a resin-impregnated web that minimizes surface imperfections and maintains a structurally favorable perpendicular arrangement of the yarns in the composite substrate. 
     BACKGROUND OF THE INVENTION 
     The current world market for resin-impregnated fiber substrates exceeds approximately 800 million yards per year. Resin-impregnated fiber substrates for composite structural applications account for 100 plus million yards (e.g., woven fiberglass, woven aramid sold under the trademark KEVLAR™, carbon, and other fabrics) while basic composites and electronic circuit boards account for 700 plus million yards (e.g., woven fiberglass fabrics). 
     A variety of conventional methods are commonly used to produce flat, bi-directional fiber substrates for use in other fabrication processes and structures such as reinforced plastic composites. In these conventional methods, a first set of yarns is positioned perpendicular to a second set of yarns after which the yarns are fixed in a resin to produce a substrate. The substrates are produced in the form of moldable resin-impregnated products. The moldable products can be cut into workpieces and used in the production of composite structures for the aerospace, automobile, and electronics industries. As referenced above, a common application is the use of the composite structures in the production of printed circuit boards typically used in the computer industry. 
     Conventional production methods for manufacturing resin-impregnated substrates often result in products that are less than suitable for particular applications. For example, advances in integrated circuit (IC) technology require a large number of integrated circuits to be placed on an individual printed circuit board. These integrated circuits have to be interconnected on the printed circuit board comprised of multiple layers (e.g., substrates with conductor traces such as copper). The surfaces of resin-impregnated substrates used in printed circuit boards often contain surface imperfections that adversely affect the conductivity of the circuit board. Minor flaws or “pimples” on the surface of the substrate are transferred to the conductive layer or layers (e.g., copper) subsequently applied to the base substrate during molding of the circuit board. Stated differently, the surface imperfections on the underlying substrate are transferred to the layers applied thereon, thus resulting in nonuniform conductive layers. Accordingly, conductive layers riddled with the surface imperfections exhibit reduced conductivity in the resulting circuits and hence degrades the overall performance of the printed circuit boards. 
     In order to compensate for the variations in the conductivity of the individual metal layers created by the imperfections, individual circuits having an increased cross-section are used on the printed circuit board. The increased size of the circuits limits the total number circuits that can be placed on the circuit board. Thus, the imperfections on the surface of the substrates forming the circuit board become a limiting factor in the production and performance of the printed circuit boards. 
     Substrates that are produced by weaving techniques further degrade the conductivity and hence limit the number of circuits on the circuit board. The weaving technique results in a weave pattern on the surface of the substrate. As conductive layers are molded on the underlying substrate, the weave pattern is transferred to the conductive layer, thus, further affecting the performance of the circuit board and further limiting the number of circuits that can be placed on the board. 
     One conventional method of producing resin-impregnated substrates includes the steps of weaving a fabric, applying a finish to the fabric, and then impregnating the finished fabric with a thermosetting or thermoplastic resin. The step of weaving a fabric to be impregnated includes beaming or warping yarns (i.e., winding warp yarns onto a beam in preparation for weaving or warp knitting) for the machine direction (i.e., direction in which the fabric is being produced in the machine) onto section beams, warp sizing the yarns while transferring the warp yarns from a section beam to a loom beam, placing the loom beam onto a loom, and finally applying the cross-direction (i.e., direction perpendicular to the direction in which the fabric is being produced by the machine) yarns to the machine direction yarns by either weaving the cross-direction yarns into the machine direction yarns or by warp-knitting. The terms “warp knitting” and “weft knitting” are used according to common industry standards wherein warp knitting denotes a type of knitting in which yarns generally run lengthwise in the fabric. Weft knitting is understood to describe a type of knitting whereby one continuous thread runs crosswise in the fabric. 
     The step of applying a finish to the fabric to be impregnated includes the preliminary step of cleaning the fabric to remove any chemicals previously applied to the yarns during the weaving or warp-knitting process. Next, the fabric is treated with additional chemicals to ensure compatibility between the woven yarns and the resin to be applied. 
     The impregnating step involves saturating the finished fabric with resin. The amount of resin applied to the fabric is controlled or metered to obtain the desired weight of the fabric. Conventional methods for metering the amount of resin applied includes scrapers as disclosed in U.S. Pat. No. 3,068,133 to W. H. Cilker et al. 
     In addition, the impregnating step requires the fabric to be heat treated to remove any residual solvents from the fabric remaining from the previous chemical treatment. The heat treatment is also necessary to partially cure the resin coating the fabric. This first conventional method of producing a resin-impregnated fiber substrate requires a variety of preliminary and subsequent processing steps other than the basic steps of weaving, applying a finish, and impregnating. Thus, the first conventional method is logistically inefficient and time consuming. 
     A second conventional method for producing a flat, bi-directional substrate involves a process commonly referred to as “filament winding” whereby a first set of yarns is saturated with resin and then wound at a desired angle around a flat rotating mold or mandrel to form a first set of yarns. Next, the flat mold is rotated ninety degrees from its original position and then a second set of yarns is wound around the first set of yarns, thereby forming a web of a predetermined thickness and desired pattern (e.g., checker board). Nevertheless, this process requires the manufacturer to produce multiple batches of resin for each individual substrate section. Accordingly, the second conventional method is time-consuming considering the multiple steps required to produce a single substrate section (e.g., the steps of saturating, winding, and rotating). Furthermore, the substrate is limited to the size of rotating mold. 
     Specifically, during the first conventional method, bobbin yarns for the warp are wound onto section beams. While the yarns on the section beams are combined to make a loom beam, warp sizes are applied to the yarns for weaving. On the loom, the sized warp yarns from the loom beam are interlaced (i.e., woven) with the weft yarns at a maximum rate of 0.42 yards per minute for a weft yarn count of forty (40) yarns per inch. The woven greige (i.e., unfinished) fabric is then heat cleaned and a finish is applied to the heat cleaned fabric which is then dried. Next, the finished fabric is shipped to a prepregger where the fabric is subsequently impregnated with resin. Prior to and following each manufacturing step referenced above, the fabric is either stored in inventory or staged on the floor, thereby creating periods of work stoppage (i.e., down-time) and increasing the amount of floor space required to produce a woven resin-impregnated substrate. 
     The various conventional techniques for applying resins to yarns that are incorporated into the substrate include moving yarns through resin-filled vessels or basins. This technique is commonly referred to as a “resin bath”. Yet, another technique for applying resin includes the use of spray devices to deliver liquid resin to either the interior or exterior of the warp yarns. Nevertheless, it is difficult to control the amount of resin delivered to the yarns forming a part of the substrate. The amount of resin delivered to the yarns is critical to the formation of the substrate because the amount of resin on each yarn determines the volume fraction (i.e., weight) of resin applied to the yarns. Furthermore, the amount of resin is also critical to the uniformity and consistency of the substrate. 
     As referenced above, conventional techniques for metering resin include the use of scrapers or adjustable spray nozzles. Unfortunately, the resin tends to clog the openings in the spray nozzles and create a build-up on the scrapers, thus requiring downtime for maintenance and cleaning. Furthermore, the clogged spray nozzles and the buildup of resin on crude scraping devices adversely affects the ability of the operator to accurately control the amount of resin applied or removed from the resin-coated substrate. Therefore, a need exists for an apparatus that accurately measures and controls the amount of resin applied to yarns during the production of resin-impregnated substrates. 
     After resin is applied t o the warp or cross-direction yarns of non-woven fabrics in conventional methods (e.g., resin bath), the warp yarns are weighted with resin and, as a result, the uniform spacing provided by the combination of dual annular rings and comb devices is forfeited due to the effects of surface tension. The surface results in the bunching of the weft and/or machine direction yarns that are suspended or supported by the dual ring device. 
     For example, U.S. Pat. No. 2,797,728 to G. Slayter et el. discloses a method and apparatus for producing a reticulated fibrous product. Slayter utilizes a series of vertically arranged, co-axial annular rings for supporting machine direction yarns as they advance in an upward direction. Slayter includes a resin bath for applying resin to the machine direction yarns at a midway point between the annular rings. Nevertheless, the resin-coated, longitudinal yarns tend to bunch together at a midway point between the resin bath and the upper ring due to the distances separating the resin bath and upper ring. The surface tension effect or bunching occurs because the cohesive forces of the liquid resin coating the yarns overcomes the tensile stress applied to the yarns as the yarns are stretched between the annular rings and contact surfaces in the resin bath. 
     The bunching together of the yarns results in non-uniform spacing of the yarns in the resulting product (i.e., substrate). As described above, the spacing discrepancies translate into surface imperfections that adversely affect the conductive layers molded to the substrate forming the printed circuit board. In short, the reduced performance (i.e., reduced conductivity and increased resistivity) of the multi-layered printed circuit board degrades the overall performance of the system incorporating conventionally manufactured resin-impregnated fiber substrates forming a part of the board. 
     Further, yarns having, less than six hundred-fifty denier are easily damaged due to abrasion when drawn over stationary surfaces. For example, conventional methods for producing substrates typically require at least two contact surfaces over which yarns are pulled during the manufacturing process. These surfaces include combs for separating yarns, curvatures for directing yarns through resin baths, and rods for directing the yarns in a different direction. The damaged yarns degrade the quality of the web and result in substrates that are not suitable for use in certain applications such as printed circuit boards. 
     The methods described above are time-consuming and costly when considering the number of steps required to produce the substrate and the amount of chemicals necessary to properly treat the fabric. The first method described above requires multiple steps to include beaming whereby yarns are drawn from individual packages of yarns in creels by a draw roll and then wound around a beam. The beaming operation is a preliminary step to the actual impregnating step. The intermediate steps between the beaming and impregnating steps include the steps of warp sizing the yarns and thereafter transferring the warp yarns to a loom beam. During the step of warp sizing, compounds are applied to the warp yarn to bind the fibers and stiffen the yarn in preparation for weaving. Further, the step of transferring includes moving the warp yarns from a flanged roll (i.e., section or beam) to a loom beam for the weaving or warp-knitting step. The number of mechanically diverse steps in the first conventional method increases the likelihood that the mechanical parts will either breakdown or render the manufacturing process inoperable due to mechanical fatigue. 
     The second conventional method described above requires a certain amount of down-time while the flat mold containing the first set of yarns is rotated ninety degrees to allow a second set of yarns to be wound about the first set of yarns. As described above, the known methods fail to provide a continuous high-speed process for continuously forming a resin-impregnated substrate whereby yarns are drawn from creels, separated and maintained at a spaced apart relationship, coated with a controlled amount of resin, and bound with a second set of perpendicular yarns. 
     Therefore, there is a need for a method and apparatus for forming a resin-impregnated fiber substrate capable of preserving the spaced-apart relationship between the machine and cross-direction yarns as they advance through the apparatus. 
     Therefore, there is also a need for an apparatus minimizing the number of contact points (i.e., stationary surfaces) over which yarns are drawn, to reduce the number of damaged yarns used to form the resulting substrate. 
     Therefore, a need also exists for a method and apparatus for continuously forming a resin-impregnated fiber substrate for composite structures wherein the amount of resin is controlled, the spaced-apart relationship is maintained, and the surface imperfections are minimized. 
     OBJECT AND SUMMARY OF THE INVENTION 
     Therefore, it is an object of the invention to provide a method for forming a resin-impregnated fiber substrate that is continuous in operation and capable of operating at high speeds (e.g., greater than eight) yards per minute per machine for a weft yarn count of forty per inch). It is another object of the invention to provide an apparatus for producing a continuous resin-impregnated fiber substrate that controls the amount of resin applied to the yarns, while maintaining the substantially parallel spaced-apart relationship between the yarns forming the substrate. It is a further object of the invention to reduce the number of surface imperfections on the resulting substrate to enhance the overall electrical properties of the composite structure (e.g., increased conductivity). The goal of the present invention is to develop a manufacturing process wherein a resin-impregnated fiber substrate is produced which can be molded into composites for structural and printed circuit boards having improved properties over composites manufactured with resin-impregnated woven fabrics. 
     Further, the present invention improves the economies of production by integrating and eliminated manufacturing processes into a single manufacturing process that converts bobbin yarns (i.e., beamed yarns) into a moldable resin-impregnated fiber substrate. 
     The product manufactured from the substrate produced by the present apparatus offers numerous advantages over conventional substrates manufactured from woven fabrics. In short, the present method imparts more uniform electrical properties and improved physical strength as compared to conventional substrates. In addition, the present apparatus and method enhances the dimensional stability and machineability of the resulting product. 
     Specifically, the claimed apparatus is designed to produce a fifty inch wide resin-impregnated composite substrate at a production speed of eight yards per minute per machine for a weft yarn count of forty yarns per inch. The apparatus is capable of using fifty denier yarn (e.g., glass yarn ECD 900 1/0) or greater for the machine or cross-direction yarn. The present apparatus offers enhanced flexibility because the warp and weft yarn count per inch can be varied independently of each other and can exceed sixty yarns per inch. 
     During the final stages of manufacture, the resin-impregnated fiber substrate produced by the present apparatus is taken up by rolls or cut into sheets of a specified length. Accordingly, the apparatus is capable of producing rolls of resin-impregnated fiber substrate greater than five hundred yards in length and fifty inches in width. 
     Furthermore, the claimed apparatus only requires thirty percent of the current floor space—including areas of raw materials, supplies, packing, shipping, etc.—required by conventional machines producing a resin-impregnated woven fabric from bobbins of yarn. 
     The overall capacity of the apparatus in producing a resin-impregnated composite substrate having a weft yarn count of forty yarns per inch is greater than three million yards per year operating for fifty weeks (assuming seven day work weeks) at eighty percent efficiency. 
     In a preferred embodiment, the use of ECG 75 1/0 fiberglass yarns in the present apparatus results in a resin-impregnated web having a yarn count of forty yarns per inch in the warp and weft directions, with forty-four percent by weight of FR-4 epoxy resin. The product would weigh approximately 11.2 ounces/square yard (e.g., 6.3 ounces of fiberglass and 4.9 ounces of resin) and have a thickness of approximately eight mils (i.e., 0.008 inches). 
     The substrate produced by the present invention embodies a structurally superior product as compared to conventional substrates. The apparatus is capable of producing a substrate having a warp and weft yarn count per inch of greater than sixty yarns per inch for each direction. The apparatus can use thermoset and thermoplastic resins and yarns as low as fifty denier (e.g., ECD 900 1/0). Thermoset resins suitable for use with the claimed invention include bismaleimide, cyanate ester, epoxy, melamine, polybutadiene, polyester, polyimide, phenolic, and vinyl ester. Further, the thermoplastic resins suitable for use in the present invention include acrylic, polyphenylsulfide, polytetrafluoroethylene, and polyvinyl chloride. 
     As a result of the improved method of applying resin to the yarns as they travel the longitudinal distance of the apparatus, the yarns are more completely covered and impregnated with resin as compared to conventional application methods. Accordingly, the improved method of applying resin enhances the structural stability of the composite formed therefrom. Structural stability of the resulting structure is further enhanced by the present method because the yarns forming the substrate are continuous and not interlaced. Dimensional stability may be further enhanced by requiring that the warp yarn count per inch and weft yarn count per inch be equal. In addition, composite structures formed with the present substrate are more stable because the current apparatus and method require a lower stress difference between the warp and weft direction than conventional apparatus and methods. 
     The present method of producing a resin-impregnated web for printed circuit boards and similar applications further benefits the composite structures formed from the resulting substrate. For example, the filaments of the yarn bundles are more homogeneously dispersed throughout the resulting composite structure, thereby enhancing the structural integrity of the substrate. Further, the composite structures made from the present method retain the perpendicular alignment of the machine and cross-direction yarns present in the web. 
     Composite structures made with the resulting web (e.g., electric circuit boards) retain more uniform electrical properties than those structures made with other woven and non-woven substrates because the present composite structure includes reduced surface defects and lacks a weave pattern. The present method also eliminates the migration of cations to the glass surface of the glass yarns because the present method eliminates the step of heat cleaning. 
     Composite structures made with the product have improved physical strength (e.g., tensile, compression, and flexure) as compared to composites made with other woven and non-woven substrates. The improved physical strength of the composite structure of the current method is partially due to the absence of interlaced yarns (i.e., the yarns are not bent). Further, the current method does not require that the yarns undergo a heat cleaning process to remove chemical additives, thereby reducing further deterioration (i.e., abrasion or surface damage) of the yarns. Moreover, lower resin to fiber volume fractions are obtainable due to the parallelism of the machine direction and cross-direction yarns, thereby reducing the amount of resin necessary to produce a composite suitable for a variety of structural applications. 
     The method for producing the resin-impregnated web includes the following steps: drawing machine direction yarns from a yarn supply contained in creels arranged around the hollow cylinder; passing the machine direction yarns from the creels through a circular collar or reed; advancing the machine direction yarns the length of the hollow cylinder&#39;s outer surface in a longitudinal direction; controlling the application of an uncured or partially cured thermoset or thermoplastic resin to the yarns as they travel upwards along the length of the hollow cylinder; winding cross-direction yarns around the periphery of the hollow cylinder and on top of the machine direction yarns, thereby forming a web; heating and cooling the resulting web; and finally collecting the web on a roll. 
     The cooling section of the cylinder lowers the temperature of the resin-coated yarns and prevents the resin-coated yarns from adhering to the surface of the cylinder. As a result of the cooling process, resin viscosity increases and the yarns are held in spatial relationship to each other. Once the yarns become stationary relative to one another, the circumference of the resin-impregnated web can then be slit or cut in the machine direction and removed from the hollow cylinder by carrier rolls. Synchronized draw rolls pull the individual widths of the resin-impregnated web from the cylinder. The resin-impregnated web can then be wound in rolls and later cut into sheets of desired dimensions. The sheets of the resin-impregnated web are then stacked and cured under pressure to produce a strong and stable composite. 
     The apparatus comprises a hollow cylinder for supporting a first series of yarns (i.e., machine direction yarns), a resin heater and pump for heating and pumping the resin to a circular hot melt resin die for applying resin to the yarns, a controller for controlling the amount of resin applied to the yarns, a rotating disk and roller assembly supported by a support disk and powered by an electro-magnet or series of electromagnets, a yarn supply containing cross-direction yarns supported by the rotating disk, circular heaters for promoting the curing of the resin-saturated yarns located around an upper portion of the cylinder, and cutting edges for cutting the resin-impregnated web into separate sections. 
     The present invention is unique in that the method claimed eliminates a number of steps involved in the conventional preparation of resin-impregnated fiber substrates. For example, the steps of weaving and finishing mentioned above in the first conventional method are eliminated. The present invention is economical and efficient, yet produces a flat bi-directional resin-impregnated substrate which maximizes the strength and stability of the molded composite. 
     In sum, the advantages of the present invention mentioned above eliminate the multiple steps discussed in the conventional methods (i.e., the weaving, finishing, and impregnating operations and/or the filament winding operations) and therefore increase efficiency of the entire process. 
     The foregoing and other objects and advantages of the invention and the manner in which the same are accomplished will become clearer based on the following detailed description taken in conjunction with the accompanying drawings in which: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevational view of the apparatus which incorporates the present invention; 
     FIG. 2 is a top plan view taken along lines  2 — 2  of FIG. 1 showing a circular frame for supporting a supply of yarn on individual creels; 
     FIG. 3 is a partial cross-section view showing the relationship of a collar for directing yarn ends along a hollow cylinder, a disk for winding transverse yarns around the longitudinal yarns, and a resin manifold for depositing liquid resin into recessed channels; 
     FIG. 4 is a partial top plan view taken along lines  4 — 4  showing the longitudinal yarns passing through dents on the interior surface of the collar and into the recessed channels along the outer surface of the cylinder at spaced intervals; 
     FIG. 5 is an exploded partial top plan view taken along lines  5 — 5  showing the relationship of the manifold containing liquid resin, a plurality of openings in communication with recessed channels on outer surface of the cylinder, and a supply of yarn supported by a disk adjacent the cylinder; 
     FIG. 6 is a partial top plan view taken along lines  6 — 6  showing heaters located at an upper portion of the cylinder heating the composite web and a water jacket secured to an interior portion of the cylinder; 
     FIG. 7 is an elevated side view taken along lines  7 — 7  showing a flared second end portion of cylinder, the water jacket, off-set carrier rolls, and section of the resulting composite resin-impregnated web. 
     FIG. 8 is a top plan view taken along lines  8 — 8  shown in FIG. 7 showing a cutter and the flared second end portion of the cylinder. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     An overall view of the apparatus  10  for producing structurally improved resin-impregnated fiber webs for use in composites according to the present invention is set forth in FIG.  1 . The apparatus includes an elongate hollow cylinder  11  having opposing end portions  12 ,  13 . The hollow cylinder may be coated with a tetrafluoroethylene fluorocarbon polymer sold under the trademark TEFLON™, or other agents for preventing the adhesion of resin. The apparatus  10  includes a means for supplying yarn to the cylinder  11  illustrated as a plurality of creels  14  supported by an upper surface of a circular frame  15  in FIG.  2 . The circular frame  15  defines an inside diameter larger than the outer diameter of the cylinder  11  such that the frame is positioned adjacent to the first end portion  12  of the hollow cylinder  11 . Thus, the plurality of creels  14  are disposed about the periphery of the hollow cylinder  11  as shown in FIGS. 1 and 2. In a further embodiment of the present invention, yarns for the machine direction may be delivered from beams of yarns. A variety of yarns may be used in the present invention to include yarns comprised of aramid, carbon, fiberglass, metal, nylon, polyester or quartz. 
     Referring to FIG. 1, the apparatus  10  further includes a means between the creels  14  and hollow cylinder  11  for guiding the yarn ends from the creels to the surface of the first end portion  12  of the cylinder  11  comprised of a collar or reed  23  positioned co-axial to the cylinder. A plurality of guides  22  and tension devices  21  for guiding the yarn ends  16  from the creels  14  to the collar  23  while maintaining sufficient tension and spacing are located between the creels and collar. The collar  23  includes an inner and outer circumferential surface and an upper  26  and lower rim  27 . 
     As shown in more detail in FIG. 3, the lower rim  27  of the collar  23  defines a bushing  25  that directs the yarn ends  16  from the creels  14  to a plurality of dents  24  defined by the inner circumferential surface of the collar upwardly in a vertical direction. As depicted in FIG. 4, the plurality of dents  24  is spaced apart substantially in parallel relationship to one another about the inner surface of the collar  23 . The dents  24  guide the yarn ends  16  from the bushing  25  to the outer surface of the first end portion  12  of the cylinder  11  while maintaining the parallel spaced relationship of the yarn ends  16  with respect to one another. In this fashion, the yarn ends  16  are directed upwardly by the bushing  25  before being separated and spaced substantially in parallel relationship to one another by the plurality of dents  24 . In this preferred embodiment, the collar  23  is positioned such that the dents  24  extend parallel to the surface of the hollow cylinder  11 . It should be understood that the collar  23  is not limited in diameter or the number of dents per inch. 
     As illustrated in FIG. 4, the apparatus  10  further includes a means for guiding the yarn ends  16  longitudinally (i.e., in the machine direction) along the outer surface of the cylinder  11  illustrated as a plurality of recessed channels  31  spaced substantially in parallel relationship to one another located about the surface of the cylinder  11 . The recessed channels  31  extend longitudinally along the surface of the cylinder and continuously align the yarn ends  16  in parallel spaced relationship as the yarn ends advance upwardly from the first end portion  12  of the cylinder to the second end portion  13  of the cylinder. 
     The apparatus  10  also includes a means for applying uncured or partially cured liquid resin to the machine direction yarns as the yarns move along the recessed channels  31  of vessel  32  for retaining uncured liquid or solid resin, a resin heater  33  for heating the liquid resin or melting the solid resin in the heater, a manifold  34  for delivering the heated resin from the vessel  32  to the interior of the cylinder  11 , and a pump  35  for pumping the heated liquid resin from the vessel  32  to the manifold  34 . It will be understood that the term uncured resin refers to resin that is not in a solid form to include partially cured resin. As shown in more detail in FIGS. 3 and 5, the manifold  34  includes of a plurality of openings  36  located between the inner and outer surface of the manifold. In this configuration, the vessel  32 , resin heater  33 , manifold  34 , and pump  35  are located within the interior of the hollow cylinder  11 . Although the manifold  34  of the present invention is positioned within the interior of the hollow cylinder, the vessel  32 , resin heater  33 , and pump  34  may be placed external to the hollow cylinder to facilitate accessibility to the same during repair or cleaning. 
     The plurality of recessed channels  31  along the outer surface of the cylinder  11  further comprise a plurality of openings  37  defining a passageway between the inner and outer surface of the cylinder  11  (see FIG.  5 ). The plurality of openings  37  in the recessed channels  31  are adjacent to and in communication with the plurality of openings  36  in the manifold, thereby allowing liquid resin to be delivered from the manifold  34  through the openings  37  and to the machine direction yarns as they advance upwardly along the outer surface of the hollow cylinder  11  in the recessed channels  31 . The resin is applied to the yarns in their parallel spaced relationship on the cylinder  11 . 
     The apparatus  10  as shown in FIG. 3 further includes a means for winding cross-direction yarns around the hollow cylinder  11  comprised of a disk  41  for supporting a yarn supply  42  positioned on the upper surface of a stationary support ring  43 . In a preferred embodiment, the yarn winding means includes an electromagnetic actuator or actuators  44  for rotating the disk  41  around the outer circumference of the cylinder  11  while the disk rests upon a plurality of rollers or spools  45  having flanged ends and mounted along the outer edges of the support ring  43 . In this configuration, the outer edges  46  of the rotating disk are supported by the flanged ends of the rollers  45 . Accordingly, the rollers  45  promote the rotation of the rotating disk  41  at relatively high speeds while restricting the lateral movement of the disk as it rotates about the circumference of the hollow cylinder  11 . Further, the flanged ends of the rollers  45  maintain the rotating disk in a stationary position coplanar with the support ring  43 . 
     In yet another embodiment, ball bearings may be displaced between the lower surface of the disk  41  and the upper surface of the stationary support ring  43  to promote rotation of the disk about the hollow cylinder  11 . In other embodiments of the present invention, the rotating disk  41  may also be propelled by belts or electric motors (not shown). 
     In this preferred embodiment, the outer edge portions  46  of the disk  41  include ferrous metals. The electromagnetic force generated by the electromagnetic actuator acts upon the ferrous metals contained in the outer edge portions  46  of the disk  41  and, thereby, propel the disk around the hollow cylinder  11 . In yet another embodiment, the disk  41  may include a raised rim on its outer periphery for supporting packages or creels of yarn at an angle or perpendicular to the hollow cylinder  11 . 
     As depicted in FIG. 3, electromagnetic actuators  44  are positioned on an outer edge portion  51  of the support ring  43 . The yarn aligning means further includes a tension device  47  for maintaining sufficient tension as the transverse yarn travels from the yarn supply  42  to a comb  52 . The comb  52  guides the cross-direction yarns onto the machine direction yarns advancing along the hollow cylinder  11  in an overlying relationship while maintaining the yarns in their substantially spaced apart parallel relationship. 
     The apparatus  10  further includes a means for controlling the delivery rate of machine direction yarn from the yarn creels  14  to the cylinder  11  comprised of a programmable controller or microprocessor  53 . The desired structure of the resulting composite web is defined by the parameters stored in the microprocessor by the operator. The microprocessor is in communication with draw rolls  61  that draw the machine direction yarns from the yarn creels  14  and along the surface of the cylinder  11 . The draw rolls  61  located adjacent two sides of the cylinder pull the machine direction yarns at equal rates as determined by the signal from the microprocessor. In addition, the apparatus includes a means for metering or controlling the amount of resin delivered from the resin vessel  32  to the machine direction yarns on the cylinder  11  comprised of a controller  54 . 
     The resin controller specifically controls the amount of resin coating to be applied to the machine direction yarns, thereby determining the resin to fiber volume fraction of the resulting web. The microprocessor  53  and controller  54  are in communication with a means for detecting the delivery rate of transverse yarns from the yarn supply  42  comprised of a sensor  55  located adjacent the electromagnetic actuator  44 . As shown in FIG. 3, in a preferred embodiment the sensor  55  is an electro-optic device capable of detecting an indicator mark  56  located on the upper portion of the rotating disk  41  as the mark repeatedly presents itself to the sensor. In operation, the sensor  55  identifies the rate at which the indicator mark  56  presents itself to the sensor and then delivers a signal to the microprocessor  53  and controller  54 . The microprocessor, in turn sends a signal to the draw rolls  61  that control the speed at which the machine direction yarns are advanced along the exterior of the hollow cylinder  11 . 
     In this configuration, the microprocessor  53  is responsive to the signal delivered by the sensor  55  which identifies the rate at which cross-direction yarns are wound around the machine direction yarns on the cylinder  11  such that the resin controller  54  adjusts the amount of resin delivered from the manifold  34  into the plurality of openings  37  located in the recessed channels  31  and onto the machine direction yarns. 
     As shown in FIG. 1, the overall configuration of the apparatus  10  is such that the hollow cylinder  11 , the yarn creels  14 , the circular collar or reed  23 , and the rotating disk  41  containing yarn supply  42  are coaxially-disposed to one another. In this configuration, the machine direction yarn ends  16  travel continuously from the creels  14  to the outer surface of the cylinder  11  through the collar  23  while cross-direction yarns from the circular disk  41  are wound transversely to and in an overlying relationship with the machine direction yarns advancing upwardly along the outer surface of the cylinder  11 . 
     The apparatus  10  further includes a means for partially curing the resin-impregnated web comprised of circular heaters  62  located adjacent the second end portion  13  of the hollow cylinder  11 . The partial curing of the web partially sets the machine direction and cross-direction yarns in a spatial relationship, thereby imparting characteristics beneficial to products made from the resulting web such as printed circuit boards (e.g., improved conductivity due to reduced imperfections on the surface of the substrate). 
     The apparatus  10  further comprises means for preventing adhesion between the outer surface of the second end portion  13  of the cylinder  11  and the partially cured longitudinal and transverse yarns comprised of a hollow water jacket  63 . In a preferred embodiment, the water jacket  63  is secured to an interior portion of the hollow cylinder  11  as shown in FIG.  1 . As depicted in FIGS. 1 and 7, a pump  64  circulates cooling water into a chamber  65  formed by the water jacket  63  to cool the outer surface of the second end portion  13  of the hollow cylinder  11 , thereby preventing the partially cured web from adhering to the outer surface of the hollow cylinder  11 . Any conventional refrigerant that results in the formation of condensation may be circulated in the chamber  65  to prevent the resin-coated yarn  16  from adhering to the hollow cylinder  11 . 
     The apparatus  10  further includes a means for separating sections of the substrate formed by the partially cured web comprised of a plurality of cutting edges  66  located adjacent the upper end of the second end portion  13  of the cylinder  11  as shown in FIG.  8 . The cutting edges  66  separate the resin-impregnated web, as the web continuously advances along the cylinder, thereby allowing the separate sections of the web to be drawn by draw rolls  61  through off-set carrier rolls  68  and onto take-up rolls  67  for later use. 
     It will be further understood that the invention comprises the method for continuously producing structurally improved resin-impregnated webs. The method comprises directing a plurality of yarn ends from a plurality of yarn creels to a hollow cylinder while maintaining the yarn ends in substantially spaced apart parallel relationship as the yarn ends are advanced in the machine direction. The method further comprises winding cross direction yarns transversely to and in close overlying relationship with the yarn ends travelling in the machine direction while applying resin to the machine direction and cross-direction yarns. Finally, the method comprises maintaining the substantially parallel spaced apart relationship while partially curing the applied resin to thereby produce a partially cured web from the resin, machine direction yarns, and cross-direction yarns. 
     In the preferred embodiments, the method comprises drawing yarns for the machine direction from the creels  14  that are placed at spaced apart intervals around exterior of the hollow cylinder  11 . The yarns are drawn by the draw rolls  61  positioned at an elevated height above the hollow cylinder  11 . Yam tension devices  21  and guides  22  previously described provide sufficient tension to the yarn as the yarns are guided to the collar  23  located adjacent the first end portion  12  of the cylinder  11 . 
     In the preferred embodiments, the step of maintaining the yarn ends in substantially spaced apart parallel relationship comprises moving the yarn ends from the tension devices  21  and guides  22  to the bushing  25  formed by the lower rim  27  of the collar  23 . The bushing  25  directs the horizontally oriented machine direction yarns from the yarn supply to the dents  24  on the interior surface of the collar  23  by directing the yarns upward in a vertical direction. The dents  24  on the collar separate and space the individual machine direction yarn ends  16  into a substantially spaced apart parallel relationship to one another as the yarn moves over the bushing  25  from the exterior to the interior of the collar. The dents  24  then direct the vertically oriented machine direction yarns from the interior of the collar  23  to the outer surface of the first end portion of the hollow cylinder  11 . 
     The tension provided by the tension devices  21  in conjunction with the dents  24  on the collar  23  maintain the substantially spaced apart parallel relationship of the machine direction yarns entering the interior of the collar as the yarn advances over the bushing  25 . In the preferred embodiment, the outside diameter of the hollow cylinder  11  is approximately equivalent to the inside diameter of the collar. 
     As shown in a preferred embodiment in FIG. 4, the dents  24  on the interior surface of the collar  23  are aligned with the recessed channels  31  positioned along the outer surface of the cylinder  1 . Accordingly, the bushing  25  and collar  23  direct the horizontally oriented yarns from the creels  14  upward in a vertical orientation while simultaneously aligning the vertically oriented yarns with the recessed channels  31  on the surface of the cylinder  11 . The machine direction yarns are then subsequently and continuously aligned in a spaced apart relationship on the hollow cylinder  11  by the recessed channels  31  as the yarn ends advance along the cylinder. 
     Next, the step of applying resin comprises heating the resin in the vessel  32 , pumping the liquid resin from the vessel to the manifold  34 , and thereafter delivering the heated liquid resin from the manifold into the recessed channels containing the machine direction yarns. The pump  35  pumps the heated, liquid resin from the vessel  32  to the manifold  34  and into the plurality of openings  36  which are in fluid communication with the plurality of openings  37  in the recessed channels  31 . Advantageously, the longitudinal yarns are more completely coated and impregnated with resin as compared to conventional methods (e.g., spraying an interior portion of the yarns) because the resin flows into the channels and around the surface of the machine direction yarns as the yarns travel in a substantially spaced apart parallel relationship to one another the length of the hollow cylinder  11 . As discussed later, the amount of resin delivered to the machine direction yarns is determined by the speed at which the cross-direction yarns are would around the cylinder. 
     The step of winding comprises winding cross-direction yarns transversely to and in close overlaying relationship with the machine direction yarns advancing along the cylinder in the recessed channels  31 . The step of winding further includes actuating the disk  41  containing the yarn supply  42  located adjacent the cylinder  11  by providing a current to the electromagnetic actuator  44 . In the preferred embodiment illustrated in FIGS. 1 and 3, rotation of the disk  41  is caused by electromagnetic forces acting on the outer edge portion  46  of the disk containing ferrous metals. The electromagnetic force is generated by positioning stationery electromagnets around the support ring powered by a power source (not shown). By controlling the supply of power, the operator is able to control the speed at which the disk  41  rotates. The disk  41  is supported by rollers  45  having flanged ends mounted to an upper surface of the stationary ring  43 . 
     The tension device  47  secured to the disk  41  ensures that the cross-direction yarns are guided to the comb  52  under sufficient tension. The comb  52  guides the cross-direction yarns onto the machine direction yarns at spaced intervals as the machine direction yarns advance upward along the outer surface of the cylinder  11 . 
     The step of directing the machine direction yarns from the creels  14  and to the surface of the cylinder  11  are controlled by the programmable controller  53 . The programmable controller includes a microprocessor in communication with the sensor  55  secured to a portion of the yarn winding means. The operator is able to control the structure of the resulting resin-impregnated fiber web by programming the rate at which the machine direction yarns are drawn along the surface of the cylinder and the amount of resin applied thereto. 
     To initiate operation of the apparatus, the operator activates a power source (not shown) which in turn generates a current that actuates the electromagnetic actuator  44 . The amount of power supplied to the electromagnetic actuator  44  determines that speed at which the disk  41  rotates. As the disk  41  rotates, the indicator mark  56  on the disk repeatedly presents itself to the sensor  55 . Next, the sensor  55  sends a signal to the microprocessor that calculates the speed at which the disk  41  is rotating. Upon determining the rate at which the disk is rotating, the microprocessor  53  sends a signal to the draw roll  61 , thereby rotating the roll and pulling the yarn from the yarn creels and along the cylinder at a rate to produce a web having the desired characteristics as input by the operator into the microprocessor. 
     As referenced above, the programmable controller  53  is in communication with a resin controller  54  for controlling the amount of resin applied to the machine direction yarns. As shown in FIGS. 1 and 3, the signal from the sensor  55  informs the programmable controller  53  of the rotation rate of the disk  41 . In turn the programmable controller  53  sends a signal to the resin controller  54  indicating the amount of resin to be applied according to the predetermined resin to fiber volume fraction selected by the operator. The amount of resin required to produce a resin-impregnated web of the desired weight is then delivered from the resin vessel  32  to the machine direction yarns in the recessed channels  31  through the openings  36  in the resin manifold  34  that are in communication with the recessed channels. 
     In short, the revolutions per minute (rpm) of the rotating disk, the number of packages of yarn on the disk, and the speed of the yarns advancing in the machine direction are variables provided to the controller that, in turn, controls the number of yarns per inch provided by the yarn winding means to the hollow cylinder  11  in the cross-machine direction. 
     The curing step comprises heating the resin-impregnated web as the web advances along the hollow cylinder  11  to partially cure the resin. Heat is applied by the circular electrical heaters  62  located adjacent an upper portion of the cylinder. The water jacket  63  cools the exterior of the cylinder adjacent the resin coated machine direction and cross-direction yarns to prevent the resin-impregnated web from adhering to the outer surface of the cylinder. The step of cooling further comprises continuously circulating cool water within the water jacket  63 . The step of cooling thereby increases the viscosity of the resin to maintain the yarns in spatial relationship to each other. 
     While the yarns continue along the second end portion  13  of the cylinder  11 , they are sufficiently held in place by the partially cured resin. As depicted in the preferred embodiment shown in FIGS. 7 and 8, the outside diameter of the hollow cylinder  11  is flared, thus creating two flat surfaces at the second end portion of the cylinder. Upon reaching the second end portion  13  of the cylinder  11 , the circumference of the partially cured resin-impregnated web is slit by the cutting edges  66  oriented in the machine direction at the edges of the flared hollow cylinder, thus creating two continuous flat resin-impregnated webs. 
     Next, each continuous flat partially cured resin-impregnated fiber web is removed from the hollow cylinder by the draw rolls  61  after passing through the series of offset carrier rolls  68 . Thereafter, each individual width of the flat partially cured resin-impregnated fiber web is collected on its respective collecting roll  67 . Each draw roll  61  is synchronized with the opposite draw roll according to the signal delivered from the programmable controller. The resulting sections of resin-impregnated fiber web are later cut into sheets of desired dimensions. The sheets of the flat partially cured resin-impregnated fiber web are then stacked and cured under pressure and temperatures to produce, for example, a cured reinforced composite for structural or printed circuit applications. 
     Projected Results 
     In projecting results according to the present invention and method, epoxy compatible fiberglass yarns for the machine direction are drawn from nineteen creels  14  placed at eighteen degree intervals around a thirty-two inch outside diameter hollow cylinder  11 . Each of the nineteen creels is capable of holding one-hundred-and-sixty twenty pound packages of yarn per side. Therefore, the nineteen creels have the capacity to support six thousand eight hundred and forty packages of yarn for the machine direction. Placement of the nineteen creels at eighteen degree intervals around the thirty-two inch cylinder creates a sufficient opening to access the thirty-two inch outside diameter hollow cylinder. 
     Next, the machine direction yarn will travel from the packages on the creels  14  through yarn tension devices  21  and guides  22  to the circular collar  23  having a thirty-three inch inside diameter. The circular collar  23  includes four thousand and twenty-one dents  24  positioned about the periphery of the collar  23 . The collar separates and spaces the individual yarn ends into a substantially spaced apart parallel relationship to one another around the hollow cylinder. 
     In an exemplary projection, 4,021 yarns (corresponding to the same number of dents in the collar, i.e., one yarn per dent) yielded a resin-impregnated fiber web having forty yarns per inch in the machine direction. The machine direction yarns travel along the thirty-two inch outside diameter hollow cylinder from the thirty-three inch inside diameter circular collar having a one-half inch curvature bushing or rod. 
     The composite disk  41  having a thirty-six inch inside diameter, a fifty-eight inch outside diameter, and a thickness of three-quarters of an inch may be rotated up to 600 revolutions per minute (rpm) around the 32-inch hollow cylinder containing the resin impregnated yarns moving in the machine direction. The disk  41  is capable of supporting fifteen twenty pound packages of epoxy resin compatible fiberglass yarn. 
     The microprocessor  53  controlling the draw rolls  61  causes the yarns and machine direction to advance in a continuous motion of {fraction (15/40)} of an inch for each revolution of the disk, resulting in forty yarns per inch across in the machine direction. Upon reaching the upper end of the second end portion  13  of the cylinder, the circumference of the partially cured epoxy resin impregnated fiberglass web is slit by the cutting edges  66  in the machine direction at the edges of the flared hollow cylinder, thus creating two continuous flat resin impregnated fiberglass webs of 50.25 inches wide. Next, the web is drawn through a plurality of offset carrier rolls  68 , draw rolls  61  and collecting rolls  67 . The carrier rolls  68  are offset from each other by {fraction (15/80)} of an inch per 50.25-inch length to maintain a perpendicular relationship between the cross-direction yarns and machine direction yarns. 
     In the drawings and specification, there have been disclosed typical embodiments of the invention, and, although specific terms have been employed, they have been used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention being set forth in the following claims.