Patent Publication Number: US-8970031-B2

Title: Semiconductor die terminal

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a national stage application under 35 U.S.C. §371 of International Application No. PCT/US2010/038600, titled SEMICONDUCTOR DIE TERMINAL, filed Jun. 15, 2010, which claims priority to United States Provisional Application No. 61/187,488, filed Jun. 16, 2009, both of which are hereby incorporated by reference in their entireties. 
    
    
     TECHNICAL FIELD 
     The present application is directed to leveraging the capabilities of additive printing processes to provide semiconductor die terminals that results in a high performance packaged IC devices after wafer dicing. 
     BACKGROUND OF THE INVENTION 
     Traditional semiconductors and IC devices are typically packaged in a variety of ways to provide redistribution from the terminals on the die to a spacing that is conducive to cost effective printed circuit board (“PCB”) fabrication techniques. In many cases, the size and distance between die terminals is so small that the device cannot be connected to the final PCB without some sort of fan out or routing. The packages also serve to protect the fragile silicon or provide additional functions such as thermal management or near device decoupling. In many cases, the size and distance between die terminals is so small that the IC device cannot be connected to the final PCB without some sort of re-routing interface. 
     Most IC devices are produced with terminals in either a peripheral pattern that runs along the edges of the IC device or an area array pattern that spans across the surface of the IC device. A main method for attachment when the terminals are in an area array pattern is to connect the terminals with solder. Basically, the package has an array of terminals that correspond to the IC device terminals. Solder is applied the terminals on the IC device and/or the package and reflowed to create the mechanical and electrical connection in a process commonly called flip chip attachment. In a flip chip attachment the IC device is flipped over to mate the terminals on the die to the terminals on the IC package substrate. 
     Recent advancements in semiconductor processing have transitioned some IC devices towards copper pillar terminals rather than the traditional under bump metallization. These copper terminals are better electrically and thermally, and have become prevalent in the production of microprocessors. The copper bumps are typically created through a plating process, which essentially grows the copper post onto the die terminal. 
     The copper pillar terminal is a relatively recent introduction into the semiconductor fabrication process, and has shown some benefits and adoption into other device types. The main limitation of the process is the plating process that is used to grow the copper terminals. 
     Once the terminals are created, the IC devices in these types of packages are often under filled with an epoxy of some type to provide support and strength to the solder joints. The epoxy protects the solder joints during use from thermal expansion, mis-match and/or shock. In both cases, the connection of the IC device to the package is generally not reworkable once packaged and if there is a missing or broken connection it is difficult to repair. 
     Once the IC devices are packaged, they are usually tested in a variety of ways to determine the reliability and performance of the IC devices in the package as they would be used in the final application. In many cases, the functional performance of the IC device is not known prior to placing it into the package and if the packaged IC device fails testing the cost of the package and processing is lost. 
     A packaging method that has increased in popularity in recent years is called Wafer Level Packaging, where the packaging materials are applied to the IC devices directly while they are still in the wafer format prior to dicing. This method has shown to be effective for relatively small pin count devices and has some advantages over handling individual IC devices and packaging them in an offline operation. Wafer Level packages tend to have routing and termination that is within the footprint of the die and not fanned out due to the fact that the fan out would be cut when the wafer is diced. 
     Area array packaging has been utilized for many years, and provides a method for interconnecting IC devices with larger terminal counts than peripheral lead packaging. In general, the area array packaging is more expensive due to the larger pin counts and more sophisticated substrates required. The main limitations for area array packaging are the terminal pitch, thermal management, cost, ability to rework faulty IC devices and reliability of the solder joints. 
     BRIEF SUMMARY OF THE INVENTION 
     The present disclosure relates to the use of additive printing processes to create semiconductor die terminals, typically at the wafer level. The printing process provides unique opportunity to add function or performance enhancement at the die level. 
     The present methodology offers an alternative to plating or sputtering operations currently used to create copper pillars. Additive printing technologies permit a wide variety of materials to be applied on a layer with a registration relative to the features of the previous layer. Selective addition of conductive, non-conductive, or semi-conductive materials at precise locations to create a desired effect has the major advantages in tuning impedance or adding electrical function on a given layer. Tuning performance on a layer by layer basis relative to the previous layer greatly enhances electrical performance. 
     One embodiment is directed to a method of making semiconductor die terminals. At least a first mask layer is selectively printed on at least a portion of a wafer containing a plurality of the semiconductor devices to create first recesses aligned with electrical terminals on the semiconductor devices. A conductive material is deposited in a plurality of the first recesses to form die terminals on the semiconductor devices. The first mask layer is removed to expose the die terminals, and the wafer is diced into a plurality of discrete semiconductor devices. 
     In one embodiment, a second mask layer is printed selectively on the first mask layer to create second recesses aligned with the first recesses. Conductive material is deposited in the second recesses to extend the die terminals on the semiconductor devices and the second mask layer is removed. The second recesses optionally have a cross-sectional area different than a cross-sectional area of the first recesses. The conductive material deposited in the first recesses can be the same or different from the conductive material deposited in the second recesses. 
     The die terminals are optionally plated. In one embodiment, the step of depositing the conductive material includes printing a conductive material in the recesses and sintering the conductive material or printing a conductive ink in the recesses. 
     In one embodiment, at least one electrical device is printed in at least one of the recesses. The electrical device is electrically coupled to a die terminal. The electrical devices can be one or more of transistors, capacitors, resistors, RF antennae, shielding, filters, signal or power altering and enhancing devices, memory devices, embedded IC, optical fibers, printed optical quality material, coaxial structures, or printed micro strip RF circuits. In another embodiment, one or more of a non-conductive material or a semi-conductive material are printed in one or more of the recesses. 
     The method also includes locating pre-formed conductive materials in one or more of the recesses and plating the recesses to form die terminals with substantially cross-sectional shapes corresponding to a cross-sectional shape of the first recesses. Alternatively, conductive foil is pressed into at least a portion of the recesses. The conductive foil is sheared along edges of the recesses. The excess conductive foil not located in the recesses is removed. The recesses are plated to form conductive traces with substantially rectangular cross-sectional shapes. 
     In another embodiment, the conductive material is printed in a plurality of the first recesses and subsequently processed to form die terminals on the semiconductor devices. 
     The present disclosure is also directed to a semiconductor with die terminals made according to the methods disclosed herein. 
     The present disclosure is also directed to an electrical assembly including a circuit member with a plurality of contact pads electrically coupled to the die terminals on the semiconductor device. This coupling can be done before dicing of the wafer or on the discrete semiconductor devices. The circuit member can be selected from one of a dielectric layer, a printed circuit board, a flexible circuit, a bare die device, an integrated circuit device, organic or inorganic substrates, or a rigid circuit. 
     The present disclosure is also directed to several additive processes that combine the mechanical or structural properties of a polymer material, while adding metal materials in an unconventional fashion, to create electrical paths that are refined to provide electrical performance improvements. By adding or arranging metallic particles, conductive inks, plating, or portions of traditional alloys, the compliant printed semiconductor package reduces parasitic electrical effects and impedance mismatch, potentially increasing the current carrying capacity. 
     The printing process permits the fabrication of functional structures, such as conductive paths and electrical devices, without the use of masks or resists. Features down to about 10 microns can be directly written in a wide variety of functional inks, including metals, ceramics, polymers and adhesives, on virtually any substrate—silicon, glass, polymers, metals and ceramics. The printing process is typically followed by a thermal treatment, such as in a furnace or with a laser, to achieve dense functionalized structures. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         FIG. 1  is a cross-sectional view of a method of making a semiconductor die terminals in accordance with an embodiment of the present disclosure. 
         FIG. 2  illustrates a method of printing mask layers on the semiconductor devices of  FIG. 1 . 
         FIG. 3  illustrates a method of printing die terminals on the semiconductor devices of  FIG. 1 . 
         FIG. 4  illustrates an optional second mask layer for extending the die terminals of  FIG. 3 . 
         FIG. 5  illustrates metalizing the recesses of  FIG. 4 . 
         FIG. 6  illustrates semiconductor die terminals in accordance with an embodiment of the present disclosure. 
         FIG. 7  illustrates the semiconductor devices of  FIG. 6  after dicing. 
         FIG. 8  illustrates an alternate method of making die terminals in accordance with an embodiment of the present disclosure. 
         FIG. 9  illustrates die terminals with undercuts in accordance with an embodiment of the present disclosure. 
         FIG. 10  illustrates an alternate method of making die terminals with complex shapes in accordance with an embodiment of the present disclosure. 
         FIG. 11  illustrates the die terminals of  FIG. 10 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  is a side sectional view of semiconductor wafer  50  containing a plurality of IC devices  52 A,  52 B,  52 C (collectively “ 52 ”) located on substrate  54 . The IC terminals  56  are facing up. The substrate  54  may be a temporary work surface or may be a portion of a semiconductor package. 
     The substrate  54  can be constructed from a variety of rigid or flexible polymeric materials, such as for example, UV stabilized tetrafunctional epoxy resin systems referred to as Flame Retardant 4 (FR-4); bismaleimide-triazine thermoset epoxy resins referred to as BT-Epoxy or BT Resin; and liquid crystal polymers (LCPs), which are polyester polymers that are extremely unreactive, inert and resistant to fire. Other suitable plastics include phenolics, polyester (PET), polyimide (PI), polyethylene napthalate (PEN), Polyetherimide (PEI), along with various fluoropolymers (FEP) and copolymers, and Ryton® available from Phillips Petroleum Company. For some applications, the substrate  54  can be a polyimide film due to their advantageous electrical, mechanical, chemical, and thermal properties. Alternatively, the substrate can be made of an insulator such as undoped silicon, glass, or a plastic material. The substrate can further be a metal foil insulated from the gate electrode by a non-conducting material. The substrate can also be a woven material or paper, planarized or otherwise modified on at least one surface by a polymeric or other coating to accept the other structures. 
       FIG. 2  illustrates mask layer  58  printed to top surface  60  of the wafer  50  at locations  62  between IC terminal  56 . The printed mask layer  58  at locations  62  creates one or more recesses  64  corresponding to each of the IC terminals  56  that are used in subsequent steps of the process. 
     As illustrated in  FIG. 3 , the recesses  64  for the IC terminals  56  are metalized to create terminals  70 . Metalizing can be performed by printing conductive particles followed by a sintering step, by printing conductive inks, or a variety of other techniques. The metalizing material is preferably of copper or similar metallic materials such as phosphor bronze or beryllium-copper. The resulting terminals  70  are optionally plated to improve conductive properties. The plating is preferably a corrosion resistant metallic material such as nickel, gold, silver, palladium, or multiple layers thereof. 
     In one embodiment, the terminals  70  are formed by depositing a conductive material in a first state in the recesses  64 , and then processed to create a second more permanent state. For example, the metallic powder is deposited in the recesses  64  and subsequently sintered, or the curable conductive material flows into the recesses  64  and is subsequently cured. As used herein “cure” and inflections thereof refers to a chemical-physical transformation that allows a material to progress from a first form (e.g., flowable form) to a more permanent second form. “Curable” refers to an uncured material having the potential to be cured, such as for example by the application of a suitable energy source. 
     As illustrated in  FIG. 4 , mask layer  72  is printed on surface  74  with recesses  76 . Alternatively, a mask layer  72  is placed on surface  74 . The recesses  76  can be defined by printing, embossing, imprinting, chemical etching with a printed mask, or a variety of other techniques. As illustrated in  FIG. 5 , the recesses  76  are metalized as discussed above to add another layer  78  to terminals  70 . 
     The recesses  64 ,  76  in the layers  58 ,  72  permit control of the location, cross section, material content, and aspect ratio of the terminals  70 . The recesses  64 ,  76  control the aspect ratio of the terminals  70 , with the corresponding improvement in signal integrity. 
     In another embodiment, pre-patterned or pre-etched thin conductive foil is transferred to the recesses  64 ,  76 . For example, a pressure sensitive adhesive can be used to retain the copper foil in the recesses  64 ,  76 . The recesses  64 ,  76  are then post-plated. The plating material fills the open spaces in the recesses  64 ,  76  not occupied by the foil circuit geometry, resulting in a cross-sectional shape corresponding to the shape of the recesses  64 ,  76 . 
     In another embodiment, a thin conductive foil is pressed into the recesses  64 ,  76 , and the edges of the recesses  64 ,  76  act to cut or shear the conductive foil. The process locates a portion of the conductive foil in the trenches  64 ,  76 , but leaves the negative pattern of the conductive foil not wanted outside and above the trenches  64 ,  76  for easy removal. Again, the foil in the trenches  64 ,  76  is preferably post plated to add material to increase the thickness of the terminals  70  and to fill any voids left between the conductive foil and the recesses  64 ,  76 . 
     In yet another embodiment, layer  78  includes one or more electrical devices, such as for example, transistors, capacitors, resistors, RF antennae, shielding, filters, signal or power altering and enhancing devices, memory devices, embedded IC, optical fibers, printed optical quality material, coaxial structures, or printed micro strip RF circuits. The electrical devices  78  can be formed using printing technology, adding intelligence to the semiconductor devices  52 . Features that are typically located on the IC device  52  can be incorporated into the terminals  70  in accordance with an embodiment of the present disclosure. 
     The availability of printable silicon inks provides the ability to print terminals and/or electrical devices  70 ,  78 , such as disclosed in U.S. Pat. No. 7,485,345 (Renn et al.); U.S. Pat. No. 7,382,363 (Albert et al.); U.S. Pat. No. 7,148,128 (Jacobson); U.S. Pat. No. 6,967,640 (Albert et al.); 6,825,829 (Albert et al.); U.S. Pat. No. 6,750,473 (Amundson et al.); U.S. Pat. No. 6,652,075 (Jacobson); U.S. Pat. No. 6,639,578 (Comiskey et al.); U.S. Pat. No. 6,545,291 (Amundson et al.); U.S. Pat. No. 6,521,489 (Duthaler et al.); U.S. Pat. No. 6,459,418 (Comiskey et al.); U.S. Pat. No. 6,422,687 (Jacobson); U.S. Pat. No. 6,413,790 (Duthaler et al.); U.S. Pat. No. 6,312,971 (Amundson et al.); U.S. Pat. No. 6,252,564 (Albert et al.); U.S. Pat. No. 6,177,921 (Comiskey et al.); U.S. Pat. No. 6,120,588 (Jacobson); U.S. Pat. No. 6,118,426 (Albert et al.); and U.S. Pat. Publication No. 2008/0008822 (Kowalski et al.), which are hereby incorporated by reference. In particular, U.S. Pat. No. 6,506,438 (Duthaler et al.) and U.S. Pat. No. 6,750,473 (Amundson et al.), which are incorporated by reference, teach using ink-jet printing to make various electrical devices, such as, resistors, capacitors, diodes, inductors (or elements which may be used in radio applications or magnetic or electric field transmission of power or data), semiconductor logic elements, electro-optical elements, transistor (including, light emitting, light sensing or solar cell elements, field effect transistor, top gate structures), and the like. 
     The terminals and/or electrical devices  70 ,  78  can also be created by aerosol printing, such as disclosed in U.S. Pat. No. 7,674,671 (Renn et al.); U.S. Pat. No. 7,658,163 (Renn et al.); U.S. Pat. No. 7,485,345 (Renn et al.); U.S. Pat. No. 7,045,015 (Renn et al.); and U.S. Pat. No. 6,823,124 (Renn et al.), which are hereby incorporated by reference. 
     Printing processes are preferably used to fabricate various functional structures, such as conductive paths and electrical devices, without the use of masks or resists. Features down to about 10 microns can be directly written in a wide variety of functional inks, including metals, ceramics, polymers and adhesives, on virtually any substrate—silicon, glass, polymers, metals and ceramics. The substrates can be planar and non-planar surfaces. The printing process is typically followed by a thermal treatment, such as in a furnace or with a laser, to achieve dense functionalized structures. 
     Ink jet printing of electronically active inks can be done on a large class of substrates, without the requirements of standard vacuum processing or etching. The inks may incorporate mechanical, electrical or other properties, such as, conducting, insulating, resistive, magnetic, semi conductive, light modulating, piezoelectric, spin, optoelectronic, thermoelectric or radio frequency. 
     In one embodiment, a plurality of ink drops are dispensed from the print head directly to a substrate or on an intermediate transfer member. The transfer member can be a planar or non-planar structure, such as a drum. The surface of the transfer member can be coated with a non-sticking layer, such as silicone, silicone rubber, or Teflon. 
     The ink (also referred to as function inks) can include conductive materials, semi-conductive materials (e.g., p-type and n-type semiconducting materials), metallic material, insulating materials, and/or release materials. The ink pattern can be deposited in precise locations on a substrate to create fine lines having a width smaller than 10 microns, with precisely controlled spaces between the lines. For example, the ink drops form an ink pattern corresponding to portions of a transistor, such as a source electrode, a drain electrode, a dielectric layer, a semiconductor layer, or a gate electrode. 
     Electrodes can be printed with metals, such as aluminum or gold, or conductive polymers, such as polythiophene or polyaniline. The electrodes may also include a printed conductor, such as a polymer film comprising metal particles, such as silver or nickel, a printed conductor comprising a polymer film containing graphite or some other conductive carbon material, or a conductive oxide such as tin oxide or indium tin oxide. 
     Dielectric layers can be printed with a silicon dioxide layer, an insulating polymer, such as polyimide and its derivatives, poly-vinyl phenol, polymethylmethacrylate, polyvinyldenedifluoride, an inorganic oxide, such as metal oxide, an inorganic nitride such as silicon nitride, or an inorganic/organic composite material such as an organic-substituted silicon oxide, or a sol-gel organosilicon glass. Dielectric layers can also include a bicylcobutene derivative (BCB) available from Dow Chemical (Midland, Mich.), spin-on glass, or dispersions of dielectric colloid materials in a binder or solvent. 
     Semiconductor layers can be printed with polymeric semiconductors, such as, polythiophene, poly(3-alkyl)thiophenes, alkyl-substituted oligothiophene, polythienylenevinylene, poly(para-phenylenevinylene) and doped versions of these polymers. An example of suitable oligomeric semiconductor is alpha-hexathienylene. Horowitz, Organic Field-Effect Transistors, Adv. Mater., 10, No. 5, p. 365 (1998) describes the use of unsubstituted and alkyl-substituted oligothiophenes in transistors. A field effect transistor made with regioregular poly(3-hexylthiophene) as the semiconductor layer is described in Bao et al., Soluble and Processable Regioregular Poly(3-hexylthiophene) for Thin Film Field-Effect Transistor Applications with High Mobility, Appl. Phys. Lett. 69 (26), p. 4108 (December 1996). A field effect transistor made with a-hexathienylene is described in U.S. Pat. No. 5,659,181, which is incorporated herein by reference. 
     A protective layer can optionally be printed onto the electrical devices. The protective layer can be an aluminum film, a metal oxide coating, a substrate, or a combination thereof. 
     Organic semiconductors can be printed using suitable carbon-based compounds, such as, pentacene, phthalocyanine, benzodithiophene, buckminsterfullerene or other fullerene derivatives, tetracyanonaphthoquinone, and tetrakisimethylanimoethylene. The materials provided above for forming the substrate, the dielectric layer, the electrodes, or the semiconductor layer are exemplary only. Other suitable materials known to those skilled in the art having properties similar to those described above can be used in accordance with the present disclosure. 
     The ink-jet print head preferably includes a plurality of orifices for dispensing one or more fluids onto a desired media, such as for example, a conducting fluid solution, a semiconducting fluid solution, an insulating fluid solution, and a precursor material to facilitate subsequent deposition. The precursor material can be surface active agents, such as octadecyltrichlorosilane (OTS). 
     Alternatively, a separate print head is used for each fluid solution. The print head nozzles can be held at different potentials to aid in atomization and imparting a charge to the droplets, such as disclosed in U.S. Pat. No. 7,148,128 (Jacobson), which is hereby incorporated by reference. Alternate print heads are disclosed in U.S. Pat. No. 6,626,526 (Ueki et al.), and U.S. Pat. Publication Nos. 2006/0044357 (Andersen et al.) and 2009/0061089 (King et al.), which are hereby incorporated by reference. 
     The print head preferably uses a pulse-on-demand method, and can employ one of the following methods to dispense the ink drops: piezoelectric, magnetostrictive, electromechanical, electro pneumatic, electrostatic, rapid ink heating, magneto hydrodynamic, or any other technique well known to those skilled in the art. The deposited ink patterns typically undergo a curing step or another processing step before subsequent layers are applied. 
     While ink jet printing is preferred, the term “printing” is intended to include all forms of printing and coating, including: pre-metered coating such as patch die coating, slot or extrusion coating, slide or cascade coating, and curtain coating; roll coating such as knife over roll coating, forward and reverse roll coating; gravure coating; dip coating; spray coating; meniscus coating; spin coating; brush coating; air knife coating; screen printing processes; electrostatic printing processes; thermal printing processes; and other similar techniques. 
       FIG. 6  illustrates the IC devices  52  with the mask layers  58 ,  72  removed to expose the terminal  70 . As illustrated in  FIG. 7 , the IC devices  52  are then singulated or cut from the wafer  50  at locations  84  using traditional methods and removed from the substrate  52 . The terminals  70  are optionally post plated to enhance conductivity, strength, resistance to corrosion, and the like. 
       FIG. 8  is a side sectional view of an alternate semiconductor wafer  100  containing a plurality of IC devices  102 A,  102 B,  102 C (collectively “ 102 ”) located on substrate  104 . The IC terminals  106  are facing up. Mask layer  108  is printed to create recesses  110 , which are subsequently metalized to create terminals  112 , as discussed above. Mask layer  114  is printed to create recesses  116  with a larger cross-sectional opening  118  and/or a different cross-sectional shape, than the cross-section of the terminal  112 . The recesses  116  are then metalized. 
       FIG. 9  illustrates the terminal  112  after removal of the mask layers  108 ,  114 , and the wafer  100  is diced. The resulting terminals  112  include undercut  120  that can aid in packaging the IC devices  102 . As is clear from  FIG. 9 , the cross-sectional shape of the terminal can be uniform or non-uniform, depending on the application. 
       FIG. 10  illustrates alternate semiconductor die terminals  150  in accordance with an embodiment of the present disclosure. A plurality of mask layers  152 A,  152 B,  152 C,  152 D,  152 E (“ 152 ”) are progressively printed on semiconductor wafer  154  so that the resulting recesses  156 A,  156 B,  156 C,  156 D,  156 E (“ 156 ”) are offset from each other. After each mask layer  152  is printed the recesses  156  are metalized, resulting in die terminals  150  with a curvilinear shape. The size, shape and number of mask layers  152  is exaggerated to illustrate the present curvilinear die terminal  160 . 
       FIG. 11  illustrates one of the semiconductor devices  162  after dicing and with the mask layers  152  removed. The die terminals  150  comprise a shape that permits flexure or elastic deformation in direction  160  when the semiconductor device is mechanically coupled with another circuit member  164 , such as for example, a die package. Other possible shape for the die terminals  160  include coils, sloping linear structures, and the like. As used herein, the term “circuit member” refers to, for example, a packaged integrated circuit device, an unpackaged integrated circuit device, a printed circuit board, a flexible circuit, a bare-die device, an organic or inorganic substrate, a rigid circuit, or any other device capable of carrying electrical current. 
     Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limit of that range and any other stated or intervening value in that stated range is encompassed within the embodiments of the disclosure. The upper and lower limits of these smaller ranges which may independently be included in the smaller ranges is also encompassed within the embodiments of the disclosure, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either both of those included limits are also included in the embodiments of the present disclosure. 
     Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the embodiments of the present disclosure belong. Although any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the embodiments of the present disclosure, the preferred methods and materials are now described. All patents and publications mentioned herein, including those cited in the Background of the application, are hereby incorporated by reference to disclose and described the methods and/or materials in connection with which the publications are cited. 
     The publications discussed herein are provided solely for their disclosure prior to the filing date of the present application. Nothing herein is to be construed as an admission that the present disclosure is not entitled to antedate such publication by virtue of prior invention. Further, the dates of publication provided may be different from the actual publication dates which may need to be independently confirmed. 
     Other embodiments of the disclosure are possible. Although the description above contains much specificity, these should not be construed as limiting the scope of the disclosure, but as merely providing illustrations of some of the presently preferred embodiments of this disclosure. It is also contemplated that various combinations or sub-combinations of the specific features and aspects of the embodiments may be made and still fall within the scope of the present disclosure. It should be understood that various features and aspects of the disclosed embodiments can be combined with or substituted for one another in order to form varying modes of the disclosed embodiments of the disclosure. Thus, it is intended that the scope of the present disclosure herein disclosed should not be limited by the particular disclosed embodiments described above. 
     Thus the scope of this disclosure should be determined by the appended claims and their legal equivalents. Therefore, it will be appreciated that the scope of the present disclosure fully encompasses other embodiments which may become obvious to those skilled in the art, and that the scope of the present disclosure is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.” All structural, chemical, and functional equivalents to the elements of the above-described preferred embodiment(s) that are known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the present claims. Moreover, it is not necessary for a device or method to address each and every problem sought to be solved by the present disclosure, for it to be encompassed by the present claims. Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims.