Abstract:
A solder-flux composition is sprayed onto a substrate by rotating the solder-flux composition inside a spray cap, and before the solder-flux liquid exits the spray cap, perturbing the flow thereof with a fluid.

Description:
This application is a divisional of U.S. patent application Ser. No. 11/613,490 filed Dec. 20, 2006, issued as U.S. Pat. No. 8,215,536 on Jul. 10, 2012, which is hereby incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     Embodiments relate generally to integrated circuit devices. In particular, embodiments relate to processes of applying a solder flux to a substrate. 
     TECHNICAL BACKGROUND 
     Processors and other integrated circuit chips can generate significant heat. During miniaturization efforts, not only are circuits being crowded into smaller geometries, but also multiple chips are being crowded into smaller packages. Flip-chip configurations are affected by the miniaturization because mounting space is also shrinking. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to depict the manner in which the embodiments are obtained, a more particular description of embodiments briefly described above will be rendered by reference to exemplary embodiments that are illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments that are not necessarily drawn to scale and are not therefore to be considered to be limiting of its scope, the embodiments will be described and explained with additional specificity and detail through the use of the accompanying drawings in which: 
         FIG. 1  is a cross-section elevation of a spray nozzle during a process of coating according to an embodiment; 
         FIG. 2  is a cross-section elevation of a spray nozzle during a process of coating according to an embodiment; 
         FIGS. 3A ,  3 B, and  3 C are time-progressive depictions of a detail section  3  taken from  FIG. 2 ; 
         FIG. 4  is a cross-section elevation of a spray apparatus during a process of coating according to an embodiment; 
         FIG. 5  is a cross-section elevation of a spray apparatus  500  during a process of coating according to an embodiment; 
         FIG. 6A  is a cross-section elevation of a integrated circuit package during solder flux processing according to an embodiment; 
         FIG. 6B  is a cross-section elevation of the integrated circuit package depicted in  FIG. 6A  after further processing; 
         FIG. 6C  is a cross-section elevation of the integrated circuit package depicted in  FIG. 6B  after further processing; and 
         FIG. 7  is a flow chart  700  that describes process flow embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure relates to spray processing of films such as solder flux films on bond pads. 
     The following description includes terms, such as upper, lower, first, second, etc. that are used for descriptive purposes only and are not to be construed as limiting. The embodiments of an apparatus or article described herein can be manufactured, used, or shipped in a number of positions and orientations. The terms “die” and “chip” generally refer to the physical object that is the basic workpiece that is transformed by various process operations into the desired integrated circuit device. A die is usually singulated from a wafer, and wafers may be made of semiconducting, non-semiconducting, or combinations of semiconducting and non-semiconducting materials. A board is typically a resin-impregnated fiberglass structure that acts as a mounting substrate for the die. A heat spreader in this disclosure is a thin structure that is dual-die-and-dual-heat spreader processed. 
     Reference will now be made to the drawings wherein like structures will be provided with like reference designations. In order to show the structures of embodiments most clearly, the drawings included herein are diagrammatic representations of various embodiments. Thus, the actual appearance of the fabricated structures, for example in a photomicrograph, may appear different while still incorporating the structures of embodiments. Moreover, the drawings show only the structures useful to understand the embodiments. Additional structures known in the art have not been included to maintain the clarity of the drawings. 
       FIG. 1  is a cross-section elevation of a spray apparatus  100  during a process of coating according to an embodiment. The spray apparatus  100  includes a coaxial fluid-flow cap  110  that is configured about a longitudinal symmetry line  108 . A solder flux liquid inlet tube  112  is disposed within the coaxial fluid-flow cap  110 . A rotatable first fitting  114  allows the solder flux liquid inlet tube  112  to be rotatably coupled to the coaxial fluid-flow cap  110  according to an embodiment. A solder flux liquid supply conduit  116  is coupled to the rotatable first fitting  114  and to a rotatable second fitting  118 . The rotatable second fitting  118  is further coupled to a solder flux liquid source  120 . 
     In an embodiment, the coaxial fluid-flow cap  110  and the solder flux liquid inlet tube  112  rotate together, such that the first fitting  114  is not rotatable, but the second fitting is rotatable. In this embodiment, there is one moving coupling. 
     A fluid flow  106  is also used in  FIG. 1  within the regions of the coaxial fluid-flow cap  110  that is outside the solder flux liquid inlet tube  112 . The general direction of fluid flow  106  is toward the mouth  122  of the solder flux liquid inlet tube  112  as influenced by the shape of the coaxial fluid-flow cap  110 . 
     As the solder flux liquid inlet tube  112  rotates and solder flux liquid reaches the mouth  122 , the solder flux liquid shears into primary fragments  127 , and away from the solder flux liquid inlet tube  112  under the centrifugal force that the rotating motion of the solder flux liquid inlet tube  112  imposes upon it. Simultaneously, the fluid flow  106  perturbs the primary fragments  127  of the solder flux liquid and thereby causes the primary fragments  127  to further fragment into secondary fragments  128 . 
     The coaxial fluid-flow cap  110  includes a nozzle  130  through which the secondary fragments  128  must pass. As the secondary fragments  128  of the solder flux liquid exit the nozzle  130 , they experience a pressure change and become tertiary fragments  129 . 
     Control of the size of the various fragments  127 ,  128 , and  129  can be done by various methods in  FIG. 1 . The rate of flow of the solder flux liquid through the solder flux liquid inlet tube  112  is one factor, coupled with the rate of rotation of the solder flux liquid inlet tube  112  that will affect the size of the primary fragments  127 . The tip or opening size, the geometry of opening—circular or oval cross-section also affects the size of the fragments prior to influence by coaxial air. In an embodiment, the shape of the mouth  122  is circular. In an embodiment, the shape of the mouth  122  is rectangular such as a square. In an embodiment, the shape of the mouth  122  is eccentric such as an oval. In an embodiment, the shape of the mouth  122  is a combination of rectilinear and curvilinear, such as a star shape with rounded points. In an embodiment, the process wherein a high viscosity flux from 0 to 1000 cp is sheared by rotational motion using coaxial assist through a concentrically rotating cap to limit overspray and aid tighter flux coverage. 
     The viscosity of the solder flux liquid within the solder flux liquid inlet tube  112  will also act in concert with the rate of flow and the rate of rotation to affect the size of the primary fragments  127 . 
     The quality of the fluid in the fluid flow  106  will also affect the fragmentation of the primary fragments  127 . In an embodiment, the fluid in the fluid flow  106  is itself a liquid in an atomized state. In an embodiment, the fluid in the fluid flow  106  is a vapor that behaves like a saturated gas. In an embodiment, the fluid in the fluid flow  106  is a gas. The fluid flow  106  can be referred to as an “air assist,” but this term is intended to be an abbreviation of the various fluid flows  106  that have been described. Additionally, when the fluid flow  106  is a gas, it can be a gas that is unreactive to the system of the solder flux liquid. 
     The exact spacing  132  between the mouth  122  of the solder flux liquid inlet tube  112  and the nozzle  130  is also a factor that affects the size of the secondary fragments  128 . The fluid flow  106  has a principal effect upon the primary fragments  127  in this spacing  132 . In an embodiment for dimensional analysis, the mouth  122  has a diameter of unit y, and the opening of the nozzle  130  has a diameter in a range from about y to about 10 times y. In an embodiment, the mouth  122  has the diameter of y, and the spacing  132  between the mouth  122  and the nozzle  130  is in a range from about 0.1 times y, to about five times y. In an embodiment, the spacing  132  between the mouth  122  and the nozzle  130  is about 2 mm. 
     In an embodiment, the mouth  122  has a diameter of y, the opening of the nozzle  130  has a diameter of about five times y, and the spacing  132  between the mouth  122  and the nozzle  130  is about three times y. 
     In an embodiment, the angle  134  that is placed at the mouth  122  of the solder flux liquid inlet tube  112  creates a backpressure within the solder flux liquid, which acts in antagonism to the shear force that is being directed at the primary fragments  127 . Rotational directions are depicted at items  124  and  126 . The angle  134  therefore affects the formation of the primary fragments  127 . In an embodiment, the angle  134  is in a range from about 1° to about 90° deviation from the vertical. In an embodiment, the angle  134  is about 30° deviation from the vertical. In an embodiment, no angle is formed at the mouth  122  of the solder flux liquid inlet tube  112 . 
     The tertiary fragments  129  are depicted as six streams that are being driven away from the nozzle  130  and toward a substrate  136  that includes a bond pad  138 . The tertiary fragments  129  of the solder flux liquid impinge on the bond pad  138  by X-Y placement control of the solder coaxial fluid-flow cap  110 . Two keep-out zones (KOZs)  140  and  142  represent locations on the substrate  136  that are not to be significantly contacted with the tertiary fragments  129  of the solder flux liquid. 
     As the tertiary fragments  129  of the solder flux liquid impinge on the bond pad  138 , there is inherent splashing that depends upon the size of the tertiary fragments  129 , the velocity, the wetting affinity for the bond pad  138 , and the viscosity of the tertiary fragments  129 , among others. 
       FIG. 2  is a cross-section elevation of a spray apparatus  200  during a process of coating according to an embodiment. The spray apparatus  200  includes a coaxial fluid-flow cap  210  that is configured about a longitudinal symmetry line  208 . A solder flux liquid inlet tube  212  is disposed within the coaxial fluid-flow cap  210 . A rotatable first fitting  214  allows the solder flux liquid inlet tube  212  to be rotatably coupled to the coaxial fluid-flow cap  210  according to an embodiment. A solder flux liquid supply conduit  216  is coupled to the rotatable first fitting  214  and to a rotatable second fitting  218 . The rotatable second fitting  218  is further coupled to a solder flux liquid source  220 . 
     In an embodiment, the coaxial fluid-flow cap  210  and the solder flux liquid inlet tube  212  rotate together, such that the first fitting  214  is not rotatable, but the second fitting  218  is rotatable. In this embodiment, there is one moving coupling. 
     A fluid flow  206  is also used in  FIG. 2  within the regions of the coaxial fluid-flow cap  210  that is outside the solder flux liquid inlet tube  212 . The general direction of fluid flow  206  is toward the mouth  222  of the solder flux liquid inlet tube  212 . The initial direction of the fluid flow  206  is a helical flow stream that originates in a bushing reservoir  244 , and that passes into the fluid-flow cap  210  at a fluid-injection port that is a cap-tangent orifice  246 . The general direction of the fluid flow  206  is also influenced by the shape of the coaxial fluid-flow cap  210 . 
     As the solder flux liquid inlet tube  212  rotates and solder flux liquid reaches the mouth  222 , the solder flux liquid shears into primary fragments  227 , and away from the solder flux liquid inlet tube  212  under the centrifugal force that the rotating motion of the solder flux liquid inlet tube  212  imposes upon it. Simultaneously, the fluid flow  206  as an “air assist,” perturbs the primary fragments  227  of the solder flux liquid and thereby causes the primary fragments  227  to further fragment into secondary fragments  228 . 
     In an embodiment, the coaxial fluid-flow cap  210  includes a nozzle similar to the nozzle  130  depicted in  FIG. 1 . Control of the size of the various fragments  227 ,  228 , and  229  can be done by the various methods that are described with respect to the apparatus depicted in  FIG. 1 . 
     The exact spacing  232  between the mouth  222  of the solder flux liquid inlet tube  212  and the nozzle  230  is also a factor that affects the size of the secondary fragments  228 . The tertiary fragments  229  are depicted as six streams that are being driven away from the nozzle  230  and toward a substrate  236  that includes a bond pad  238 . The tertiary fragments  229  of the solder flux liquid impinge on the bond pad  238  by X-Y placement control of the solder coaxial fluid-flow cap  210 . Two keep-out zones (KOZs)  240  and  242  represent locations on the substrate  236  that are not to be significantly contacted with the tertiary fragments  229  of the solder flux liquid. Rotational directions are depicted at items  224  and  226 . 
     As the tertiary fragments  229  of the solder flux liquid impinge on the bond pad  238 , there is inherent splashing that depends upon the size of the tertiary fragments  229 , the velocity, the wetting affinity for the bond pad  238 , and the viscosity of the tertiary fragments  229 , among others. 
       FIGS. 3A ,  3 B, and  3 C are time-progressive depictions of a detail section  3  taken from  FIG. 2 . The depiction in  FIGS. 3A ,  3 B, and  3 C are simplified by assuming a streamlined flow of an air-assist fluid. The flow regime can be more complex, such as a turbulent flow of the air-assist fluid, that perturbs the primary fragments. 
     In  FIG. 3A , a primary fragment  227  has exited the solder flux liquid inlet tube  212  ( FIG. 2 ) and is falling away as illustrated by the first vector  348 . The first vector  348  represents the effect of the centrifugal force upon the primary fragment  227 , as well as the effect of gravity thereupon, if the process is being carried out in a G-field. A second vector  350  represents the flow regime of the fluid flow  206  as it causes a shearing force upon the primary fragment  227 . In  FIG. 3B , the second vector causes a perturbation upon the integrity of primary fragment  227 . The perturbation is represented by the primary fragment  227  beginning to separate into more than one smaller fragments. In  FIG. 3C , the second vector  350  has accomplished a further dividing of the primary fragment  227  into a plurality of secondary fragments  228 . Splashing of the secondary fragments  228  is less likely than that of the primary fragments  227 , where all other factors are considered equal or less significant. 
       FIG. 4  is a cross-section elevation of a spray apparatus  400  during a process of coating according to an embodiment. The spray apparatus  400  includes a coaxial fluid-flow cap  410  that is configured about a longitudinal symmetry line  408 . A solder flux liquid inlet tube  412  is disposed within the coaxial fluid-flow cap  410 . A rotatable first fitting  414  allows the solder flux liquid inlet tube  412  to be rotatably coupled to the coaxial fluid-flow cap  410  according to an embodiment. A solder flux liquid supply conduit  416  is coupled to the rotatable first fitting  414  and to a rotatable second fitting  418 . The rotatable second fitting  418  is further coupled to a solder flux liquid source  420 . Rotational directions are depicted at items  424  and  426 . 
     In an embodiment, the coaxial fluid-flow cap  410  and the solder flux liquid inlet tube  412  rotate together, such that the first fitting  414  is not rotatable but the second fitting  418  is rotatable. In this embodiment, there is one moving coupling. 
     A fluid flow  406  is also used in  FIG. 4  within the regions of the coaxial fluid-flow cap  410  that is outside the solder flux liquid inlet tube  412 . The general direction of fluid flow  406  is toward the mouth  422  of the solder flux liquid inlet tube  412 . The initial direction of the fluid flow  406  is a substantially downward vertical flow stream that originates in a bushing reservoir  452  and that passes into the fluid-flow cap  410  at a fluid-injection port that is a cap-coaxial orifice  446 . The general direction of the fluid flow  406  is also influenced by the shape of the coaxial fluid-flow cap  410 . 
     Where the process is conducted in a gravity environment and assuming the orientation of the  400  is a illustrated in  FIG. 4 , the secondary fragments  428  will have a downward vertical component in the first vector (see  FIG. 3A ). Nevertheless, the flow regime depicted in  FIG. 4  for the fluid flow  406  can be qualified as an “orthogonal perturbation” of the primary fragments. In any event, the quality of the primary fragments are affected by second perturbation of the flow regime from the fluid flow  406 . In some embodiments, the perturbation is a substantially orthogonal perturbation. In some embodiments, the perturbation is a nominally contrary to the first vector (see  248  in  FIG. 3A ). In an embodiment, the second perturbation is even collinear, but the second vector is different in quantity from the first vector. 
     In an embodiment, the coaxial fluid-flow cap  410  includes a nozzle similar to the nozzle  130  depicted in  FIG. 1 . Control of the size of the various fragments  427 ,  428 , and  429  can be done by the various methods that are described with respect to the apparatus depicted in  FIG. 1  and in  FIG. 2 . As flow of the solder flux liquid develops near the mouth  422 , upstream solder flux liquid changes from a plug- or slug flow regime  423 , to a transition regime  425 , and then to the first fragments  427 . 
     The exact spacing  432  between the mouth  422  of the solder flux liquid inlet tube  412  and the nozzle  430  is also a factor that affects the size of the secondary fragments  428 . The tertiary fragments  429  are depicted as six streams that are being driven away from the nozzle  430 , and toward a substrate  436  that includes a bond pad  438 . The tertiary fragments  429  of the solder flux liquid impinge on the bond pad  438  by X-Y placement control of the solder coaxial fluid-flow cap  410 . Two KOZs  440  and  442  represent locations on the substrate  436  that are not to be significantly contacted with the tertiary fragments  429  of the solder flux liquid. 
       FIG. 5  is a cross-section elevation of a spray apparatus  500  during a process of coating according to an embodiment. The spray apparatus  500  includes a coaxial fluid-flow cap  510  that is configured about a longitudinal symmetry line  508 . The structures depicted in  FIG. 5  are substantially similar to the structures depicted in  FIG. 4 . Consequently, the reference numbers are mostly retained. Rotation of the coaxial fluid-flow cap  510  is depicted to be counterclockwise, while rotation of the solder flux liquid inlet tube  512  is depicted to be clockwise. This counter-rotation of the two structures  510  and  512  represents another processing factor that can affect the size of the secondary fragments  528 , and consequently, the tertiary fragments  529 . In other words, the counter-rotation represents independently rotatable structures between the coaxial fluid-flow cap  510  and the solder flux liquid inlet tube  512 . Independently rotatable can mean rotating in the same or opposite directions, but in either cases, not necessarily with the same angular velocity. 
       FIG. 6A  is a cross-section elevation of a integrated circuit package  600  during solder flux processing according to an embodiment. An integrated circuit (IC) die  610  is flip-chip disposed above a mounting substrate  612  and is to be electrically coupled to the mounting substrate  612  through a series of electrical bumps, one of which is indicated with the reference numeral  614 . 
     A solder flux composition  616  is depicted as having been deposited upon the mounting substrate  612 . The solder flux composition  616  has wetted a bond pad  618  that is disposed on the upper surface  620  of the mounting substrate  612 . Depositing of the solder flux composition  616  is done by X-Y grid spraying according to an embodiment. 
       FIG. 6B  is a cross-section elevation of the integrated circuit package depicted in  FIG. 6A  after further processing. The IC package  601  depicts reflow of the solder bump  614 , such that it is reflowing without the solder drawing too far from the bond pad  618  from a KOZ  622  toward a second KOZ  624 . The KOZs are regions that must remain clear of solder flux materials for further packaging needs and that also would create possible solder-wick opens (SWOs) if the solder is allowed to flow into these zones. The KOZ in this case is to be defined as the perimeter enclosing the entire bond-pad array. 
       FIG. 6C  is a cross-section elevation of the integrated circuit package depicted in  FIG. 6B  after further processing. The IC package  602  depicts a post flux-removal condition. In an embodiment, a liquid is used to wash any residual flux from the region of the reflowed solder bump  615 . 
       FIG. 6C  also depicts further processing of the IC package  602  such that the IC die  610  has been reflow mounted to the mounting substrate  612 . The IC die  610  therefore makes electrical communication to the mounting substrate  612  though the solder bumps  615   FIG. 7  is a flow chart  700  that describes process flow embodiments. 
     At  710 , the process includes contacting a solder flux composition to a mounting substrate under conditions of a first shear force upon the solder flux liquid and a second perturbation force by an air-assist liquid. In an embodiment, the process commences and terminates at  710 . 
     At  720 , the process includes heating the solder flux composition to the reflow temperature of the solder bump. In an embodiment, the method commences at  710  and terminates at  720 . In an embodiment, the process commences and terminates at  720 . 
     At  730 , the process includes washing the package to remove residual solder flux. In an embodiment, the method commences at  710  and terminates at  730 . 
     At  740 , the package is installed into a computing system. 
     Various solder fluxes can be used in the process embodiments. In various embodiments, the solder flux composition may be used as part of a soldering process for forming various integrated circuit devices. For the embodiments, a solder flux composition embodiment may remove oxide from a surface onto which soldering is to occur, thereby increasing the ability of the solder to adhere to the surface of the substrate. In some embodiments, the solder flux composition embodiment may prevent oxide growth on a surface to be soldered as well as decreasing air and/or contaminants at the surface of the substrate. 
     In an embodiment, a solder flux composition includes tartaric acid. A group of solder flux compositions include the tartaric acid, a resin, an amine, a solvent, and the solution, reaction, and mixture products thereof. The tartaric acid-containing solder flux composition can be obtained from Senju America, Inc. of Great Neck, N.Y. One selected solder flux composition from Senju is Senju 42™. 
     Where a surfactant is used, sometimes referred to as a flow modifier, the specific surfactant that is employed depends upon compatibility with the solder flux composition. In an embodiment, the surfactant is anionic such as long chain alkyl carboxylic acids, such as lauric acids, steric acids, and the like. In an embodiment, the surfactant is nonionic. Examples of nonionic surfactants are polyethylene oxides, poly propylene oxides, and the like. In an embodiment, the surfactant is cationic, such as alkyl ammonium salts, such as tert butyl ammonium chlorides, or hydroxides. In an embodiment, the flow modifier is provided in a range from about 0.1% to about 10% by weight of the total solder flux composition when it is prepared. 
     In some embodiments, an amine is used. In an embodiment, the amine is an alkyl substituted amine. In an embodiment, the amine is an ethanol amine. In an embodiment, the amine is an ethoxylated amine. In an embodiment, the amine is a propoxylated amine. 
     In an embodiment, a liquid primary aromatic diamine is used. One example liquid primary aromatic diamine is diethyldiaminotoluene (DETDA), which is marketed as ETHACURE® 100 from Ethyl Corporation of Richmond, Va. Another example liquid primary aromatic diamine is a dithiomethyldiaminotoluene such as Ethacure® 300. Another example liquid primary aromatic diamine is an alkylated methylenedianiline such as Lapox® K-450 manufactured by Royce International of Jericho, N.Y. 
     In an embodiment, a liquid hindered primary aliphatic amine is used. One example liquid hindered primary aliphatic amine is an isophorone diamine. Another example liquid hindered primary aliphatic amine is an alkylated methylenedianiline such as Ancamine® 2049 manufactured by Pacific Anchor Chemical Corporation of Allentown, Pa. 
     In an embodiment, a liquid secondary aromatic amine is used. One example liquid secondary aromatic amine embodiment is an N,N′-dialkylphenylene diamine such as Unilink® 4100 manufactured by DorfKetal of Stafford, Tex. Another example liquid secondary aromatic amine embodiment is an N,N′-dialkylmethylenedianilines: i.e. Unilink® 4200. 
     In various embodiments, a solder flux composition may comprise less than 40 weight % of the amine. 
     In an embodiment, a resin is used to provide tackiness of the solder flux composition to the bond pad and the solder bump up to and including the time of reflow. The solder flux composition may include the resin, which may be present in an amount from about 1% to about 20% by weight based on the organic components present. 
     In an embodiment, a cycloaliphatic epoxy resin is used. In an embodiment, a bisphenol A type epoxy resin is used. In an embodiment, a bisphenol-F type epoxy resin is used. In an embodiment, a novolac epoxy resin is used. In an embodiment, a biphenyl type epoxy resin is used. In an embodiment, a naphthalene type epoxy resin is used. In an embodiment, a dicyclopentadiene-phenol type epoxy resin is used. In an embodiment, a combination of any two of the resins is used. In an embodiment, a combination of any three of the resins is used. In an embodiment, a combination of any four of the resins is used. 
     This Detailed Description refers to the accompanying drawings that show, by way of illustration, specific aspects and embodiments in which the present disclosure may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosed embodiments. Other embodiments may be used and structural, logical, and electrical changes may be made without departing from the scope of the present disclosure. The various embodiments are not necessarily mutually exclusive, as some embodiments can be combined with one or more other embodiments to form new embodiments. 
     The term “horizontal” as used in this document is defined as a plane parallel to the conventional plane or surface of a wafer or substrate, regardless of the orientation of the wafer or substrate. The term “vertical” refers to a direction perpendicular to the horizontal as defined above. Prepositions, such as “on”, “side” (as in “sidewall”), “higher”, “lower”, “over”, and “under” are defined with respect to the conventional plane or surface being on the top surface of the wafer or substrate, regardless of the orientation of the wafer or substrate. The Detailed Description is, therefore, not to be taken in a limiting sense, and the scope of this disclosure is defined only by the appended claims, along with the full scope of equivalents to which such claims are entitled. 
     The Abstract is provided to comply with 37 C.F.R. §1.72(b) requiring an abstract that will allow the reader to quickly ascertain the nature and gist of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. 
     In the foregoing Detailed Description, various features are grouped together in a single embodiment for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed embodiments of the invention require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed embodiment. Thus the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separate embodiment. 
     It will be readily understood to those skilled in the art that various other changes in the details, material, and arrangements of the parts and method stages that have been described and illustrated to explain the nature of this invention may be made without departing from the principles and scope of the invention as expressed in the subjoined claims.