Patent Publication Number: US-7585186-B2

Title: Performance enhancing contact module assemblies

Description:
BACKGROUND OF THE INVENTION 
   The subject matter herein relates generally to electrical connectors, and more particularly, to back plane connectors. 
   With the ongoing trend toward smaller, faster, and higher performance electrical components such as processors used in computers, routers, switches, etc., it has become increasingly important for the electrical interfaces along the electrical paths to also operate at higher frequencies and at higher densities with increased throughput. For example, performance demands for video, voice and data drive input and output speeds of connectors within such systems to increasingly faster levels. 
   In a traditional approach for interconnecting circuit boards, one circuit board serves as a back plane and the other as a daughter board. The back plane typically has a connector, commonly referred to as a header, which includes a plurality of signal contacts which connect to conductive traces on the back plane. The daughter board connector, commonly referred to as a receptacle, also includes a plurality of contacts. Typically, the receptacle is a right angle connector that interconnects the back plane with the daughter board so that signals can be routed therebetween. The right angle connector typically includes a mating face that receives the plurality of signal pins from the header on the back plane, and contacts on a mounting face that connect to the daughter board. 
   At least some right angle connectors include a plurality of contact modules that are received in a housing. The contact modules typically include a lead frame encased in a dielectric body. The lead frame includes a plurality of conductors that interconnect electrical contacts held on a mating end of the contact module with corresponding contacts held on a mounting end of the contact module. However, known connectors have problems operating at the higher performance levels of current systems. For example, known backplane connectors have limits to high speed electrical performance in the areas such as crosstalk, noise persistence, footprint impedance, and skew. 
   A need remains for a connector that overcomes at least some of the existing connector limitations to meet more demanding performance requirements in a cost effective and reliable manner. 
   BRIEF DESCRIPTION OF THE INVENTION 
   In one embodiment, a contact module assembly is provided that includes a dielectric body having a mating end with a plurality of mating contacts and a mounting end with a plurality of mounting contacts. A lead frame is at least partially encased by the dielectric body, wherein the lead frame has a plurality of conductors representing both signal conductors and ground conductors extending along a lead frame plane. The signal and ground conductors extend from respective ones of the mating contacts and the mounting contacts, wherein at least some of the ground conductors include a mating contact terminal proximate the respective mating contact and a mounting contact terminal proximate the respective mounting contact. The ground conductors extend only partially between the mating contact and the mounting contact associated with the respective ground conductor such that a gap exists between the mating contact terminal and the mounting contact terminal of the ground conductor. A commoning member electrically connects the mating contact terminal and the mounting contact terminal of at least one of the ground conductors, wherein the commoning member is oriented in a non-coplanar relation with the lead frame plane. 
   Optionally, the dielectric body may have a trench extending entirely therethrough at least partially along the gap between the mating contact terminal and the mounting contact terminal of at least one of the ground conductors. The dielectric body may have a side substantially parallel to the lead frame plane, wherein the commoning member extends along the side and includes at least one tab extending therefrom that engages the lead frame. Optionally, at least two adjacent conductors define ground conductors. The two adjacent ground conductors may cooperate to form a ground pad, wherein the commoning member is mechanically and electrically connected to the ground pad. Optionally, the signal conductors may have different lengths defined between the mating and mounting contacts, wherein the signal conductors define differential pairs, and wherein the longer signal conductors within a differential pair include at least one compensation region being wider than adjacent regions thereof, and at least a portion of the compensation region is exposed to air by a window in the dielectric body. 
   In another embodiment, an electrical connector is provided that includes a housing, and first and second contact module assemblies held by the housing. Each of the contact module assemblies include a dielectric body having a mating end with a plurality of mating contacts and a mounting end with a plurality of mounting contacts, and a lead frame at least partially encased by the dielectric body. The lead frame has a plurality of conductors representing both signal conductors and ground conductors extending along a lead frame plane, wherein the signal and ground conductors extending from respective ones of the mating contacts and the mounting contacts. At least some of the ground conductors include a mating contact terminal proximate the respective mating contact and a mounting contact terminal proximate the respective mounting contact, wherein the ground conductors extend only partially between the mating contact and the mounting contact associated with the respective ground conductor such that a gap exists between the mating contact terminal and the mounting contact terminal of the ground conductor. A commoning member electrically connects the mating contact terminal and the mounting contact terminal of at least one of the ground conductors, wherein the commoning member is oriented in a non-coplanar relation with the lead frame plane. 
   In a further embodiment, a contact module assembly is provided that includes a dielectric body having a mating end with a plurality of mating contacts and a mounting end with a plurality of mounting contacts, the dielectric body defining at least one window therein. A lead frame is at least partially encased by the dielectric body, wherein the lead frame has a plurality of conductors representing both ground conductors and signal conductors arranged as differential pairs. The signal conductors extend from respective ones of the mating contacts and the mounting contacts such that at least some of the signal conductors have different lengths defined between the mating and mounting contacts. The longer signal conductor within a differential pair includes at least one compensation region being wider than adjacent regions thereof, wherein at least a portion of the compensation region is exposed to air by a respective one of the windows in the dielectric body. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of an exemplary embodiment of an electrical connector. 
       FIG. 2  is an exploded view of the electrical connector shown in  FIG. 1  illustrating a plurality of contact module assemblies. 
       FIG. 3  is a perspective view of one of the contact module assemblies shown in  FIG. 2 . 
       FIG. 4  is a side view of an exemplary embodiment of a lead frame for the contact module assembly shown in  FIG. 3 . 
       FIG. 5  is a side view of an alternative embodiment of a lead frame for another one of the contact module assemblies shown in  FIG. 2 . 
       FIG. 6  is an assembled view of the contact module assembly shown in  FIG. 3 , with an exemplary commoning member affixed thereto. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  illustrates an exemplary embodiment of an electrical connector  10 .  FIG. 2  is an exploded view of the electrical connector  10 . While the connector  10  will be described with particular reference to a backplane receptacle connector, it is to be understood that the benefits herein described are also applicable to other connectors in alternative embodiments. The following description is therefore provided for purposes of illustration, rather than limitation, and is but one potential application of the subject matter herein. 
   As illustrated in  FIG. 1 , the connector  10  includes a dielectric housing  12  having a forward mating end  14  that includes a shroud  16  and a mating face  18 . The mating face  18  includes a plurality of mating contacts  20  (shown in  FIG. 2 ), such as, for example, contacts within contact cavities  22 , that are configured to receive corresponding mating contacts (not shown) from a mating connector (not shown). The shroud  16  includes an upper surface  26  and a lower surface  28  between opposed sides  30 ,  32 . The upper and lower surfaces  26 ,  28  and sides  30 ,  32  each include a chamfered forward edge portion  34 . An alignment rib  36  is formed on the upper shroud surface  26  and lower shroud surface  28 . The chamfered edge portion  34  and the alignment ribs  36  cooperate to bring the connector  10  into alignment with the mating connector during the mating process so that the contacts in the mating connector are received in the contact cavities  22  without damage. 
   As illustrated in  FIG. 2 , the housing  12  also includes a rearwardly extending hood  38 . A plurality of contact module assemblies  50  are received in the housing  12  from a rearward end  52 . The contact module assemblies  50  define a connector mounting face  54 . The connector mounting face  54  includes a plurality of contacts  56 , such as, but not limited to, pin contacts, that are configured to be mounted to a substrate (not shown), such as, but not limited to, a circuit board. In an exemplary embodiment, the mounting face  54  is substantially perpendicular to the mating face  18  such that the electrical connector  10  interconnects electrical components that are substantially at a right angle to one another. In one embodiment, the housing  12  holds two or more different types of contact module assemblies  50 , such as, but not limited to, contact module assemblies  50 A,  50 B. Alternatively, the housing  12  may hold only a single type of contact module assembly  50 , such as, but not limited to, any of the contact module assemblies  50 A,  50 B. 
   In an exemplary embodiment, each of the contact module assemblies  50  includes a commoning member  60  that extends along one side thereof. Optionally, the commoning member  60  may define a ground plane for the respective contact module assembly  50 . In the illustrated embodiment, the commoning member  60  includes a plurality of contacts  62 , such as eye-of-the-needle contacts, that electrically and mechanically connect to the contact module assembly  50 . Optionally, the commoning member  60  may be used to provide shielding between adjacent contact module assemblies  50 . 
     FIG. 3  illustrates an exemplary embodiment of one of the contact module assemblies  50  that includes an exemplary embodiment of an internal lead frame  100  and a dielectric body  102 .  FIG. 4  illustrates the lead frame  100  that is held within the dielectric body  102 . The various features of the contact module assembly are designed to provide an electrical connector  10  operable at frequencies, densities and/or throughputs that are relatively higher than electrical connectors without some or all of the features described herein, by reducing crosstalk, reducing noise persistence, reducing impedance footprint mismatch and/or reducing intra-pair skew, as described in further detail below. 
   As illustrated in  FIG. 3 , the lead frame  100  is enclosed within the body  102 , but is at least partially exposed by the body  102  in certain areas. In some embodiments, the body  102  is manufactured using an over-molding process. During the molding process, the lead frame  100  is encased in a dielectric material, which forms the body  102 . The mating contacts  20  extend from a mating end portion  104  of the body  102 , and the mounting contacts  56  extend from a mounting end portion  106  of the body  102  and the lead frame  100 . The mating end portion  104  and the mounting end portion  106  are generally perpendicular to one another. In the illustrated embodiment, a mating contact  20 A defines a radially inner mating contact, while a mating contact  20 B defines a radially outer mating contact. Similarly, a mounting contact  56 A defines a radially inner mounting contact, while a mounting contact  56 B defines a radially outer mounting contact. The body  102  includes opposite side portions  108  and  110  that extend substantially parallel to and along the lead frame  100 . 
   As illustrated in  FIG. 4 , the mating and mounting contacts  20 ,  56  are integrally formed with the lead frame  100 . The lead frame  100  is generally planar and defines a lead frame plane. A carrier strip  112  initially holds the lead frame  100  and then is removed and discarded after the body  102  (shown in  FIG. 3 ) is over-molded. The lead frame  100  includes a plurality of conductors  116  that extend along predetermined paths between each mating contact  20  to a corresponding mounting contact  56 . In an exemplary embodiment, the contacts  20 ,  56  are integrally formed with, and define portions of, the conductors  116 . Alternatively, the contacts  20 ,  56  may be terminated to the ends of the conductors  116 . The conductors  116  may be either signal conductors, ground conductors, or power conductors. The lead frame  100  may include any number of conductors  116 , any number of which may be selected as signal conductors, ground conductors, or power conductors according to a desired pinout selected for the contact module assembly  50 . Optionally, adjacent signal conductors may function as differential pairs, and each differential pair may be separated by at least one ground conductor. 
     FIG. 4  illustrates the conductors  116  and associated contacts  20 ,  56  arranged according to an exemplary pinout for one contact module assembly, such as contact module assembly  50 A. The lead frame  100  includes both ground and signal conductors (identified in  FIG. 4  with either a G for ground or an S for signal), wherein the signal conductors are arranged as differential pairs. The lead frame  100  provides two ground conductors between each differential pair of signal conductors, such that a first pinout, as defined from the radially outer conductor, is ground-signal-signal-ground-ground-signal-signal-ground-ground-signal-signal-ground-ground-signal-signal. By providing two ground conductors between adjacent differential pairs, the separation between adjacent (e.g. nearest) signal conductors of the adjacent differential pairs is increased as compared to pinouts having only a single ground conductor therebetween. In some alternative embodiments, at least some of the signal conductors are separated by only a single ground conductor, more than two ground conductors, or alternatively, no ground conductors. 
   As further illustrated in  FIG. 4 , the conductors  116  defining the signal conductors extend entirely between the respective mating and mounting contacts  20 ,  56 . However, each of the conductors  116  defining ground conductors extend only partially between the respective mating and mounting contacts  20 ,  56 . The conductors  116  defining the ground conductors have mating contact terminals  120  proximate the mating contacts  20 , and the conductors  116  defining the ground conductors have mounting contact terminals  122  proximate the mounting contacts  56 . A gap  124  is defined between the mating contact terminal  120  and the mounting contact terminal  122  of each ground conductor. 
   By providing the gap  124 , and removing at least a portion of the ground conductors between the mating and mounting contact terminals  120 ,  122 , the noise persistence of the contact module assembly  50  may be reduced as compared to contact module assemblies having ground conductors that extend entirely between the mating and mounting contacts  20 ,  56 . The amount of noise persistence (and noise persistence reduction) may be controlled by selecting a length of the gap  124  and a length of each of the mating contact terminal  120  and the mounting contact terminal  122 . For example, the lengths of the mating contact terminal  120  and the mounting contact terminal  122  cooperate to define the length of the gap  124  (e.g. the distance between the mating contact terminal  120  and the mounting contact terminal  122 ), wherein the length of the gap  124  may be lengthened by decreasing the length of at least one of the mating contact terminal  120  and the mounting contact terminal  122 . In some alternative embodiments, at least some of the ground conductors extend entirely between the mating and mounting contacts  20 ,  56 , and the ground conductors may include terminals proximate the mating contacts  20  and/or the mounting contacts  56 . 
   Returning to  FIG. 3 , in an exemplary embodiment, the body  102  includes a plurality of trenches  126  formed entirely through the body  102  between the sides  108 ,  110 . The trenches  126  provide an air gap through the body  102 . The trenches  126  are aligned with the gaps  124  (shown in  FIG. 4 ). As such, the trenches  126  are provided between signal conductors of adjacent differential pairs. The trenches  126  are defined by side walls  128  and end walls  130 . Optionally, the side walls  128  may be slanted and extend non-perpendicular from the sides  108 ,  110 . The trenches  126  have lengths  132  measured between the end walls  130 , and the lengths  132  are selected to balance structural integrity of the contact module assembly  50  with the enhancement in the electrical performance of the contact module assembly  50 . For example, webs  134  are formed between trenches  126  that provide rigidity to the body  102 . Additionally, the trenches  126  provide an air gap between signal conductors, which may decrease the cross-talk of the contact module assembly  50  by providing an air dielectric therebetween as opposed to only a plastic dielectric. Selecting the width and the length of the trenches  126  may balance these factors. Optionally, the trenches  126  may be filled with a dielectric material having certain characteristics that may enhance at least one of the stability and the electrical performance of the contact module assembly  50 . 
   In an exemplary embodiment, and as illustrated in  FIG. 4 , adjacent ground conductors are commoned to form a ground pad  136 . For example, the ground conductors are integrally formed with one another downstream of the respective contacts  20 ,  56 . The ground pads  136  are more rigid and/or sturdier as compared to individual conductors  116 , as the ground pad  136  is wider than an individual conductor  116 . In an exemplary embodiment, and for reasons described more fully below, each of the ground pads  136  includes an opening  138  therethrough that receive the contacts  62  of the commoning member  60  (shown in  FIG. 2 ). Additionally, as illustrated in  FIG. 3 , the body  102  includes openings  140  within the sides  108 ,  110  that are aligned with and provide access to at least a portion of the ground pads  136 , and particularly, the openings  138 . When connected, the commoning member  60  interconnects and electrically commons each of the ground conductors to which the commoning member  60  is connected. In some alternative embodiments, at least some of the ground conductors do not form ground pads and/or are not connected to the commoning member  60 . 
   Each of the conductors  116  defining signal conductors have a predetermined length  142  defined between the mating contact  20  and the mounting contact  56 . The lengths  142  of each of the signal conductors are different, due at least in part to the right angle nature of the contact module assembly  50 . For example, the radially inner conductors  116  are generally shorter than the radially outer conductors  116 . While each signal conductor within a differential pair has approximately equal lengths, because of factors such as the size constraint of the contact module assembly  50  and the cost or complexity of manufacture, the radially inner signal conductor within each differential pair is generally slightly shorter than the radially outer signal conductor. Any difference in length may lead to skew problems, as the signals within the differential pair travel along different path lengths. 
   In an exemplary embodiment, at least some of the signal conductors include compensation regions  144 . For example, the radially outer signal conductors within each differential pair each include compensation regions  144 . The compensation regions  144  are defined as having increased widths along the conductors  116 . With reference back to  FIG. 3 , the compensation regions  144  are at least partially exposed to air by the body  102  to provide a different dielectric through which the signal conductor extends. For example, the body  102  includes windows  146  formed in the sides  108 ,  110  that expose the conductors  116  and/or the compensation regions  144 . In an exemplary embodiment, the windows  146  only expose the radially outer signal conductor within each differential pair, such that the radially inner signal conductor remains encased along the corresponding portion of the length thereof. Within each differential pair, the different dielectric (e.g. air for the radially outer signal conductor) allows the differential signal of the radially outer conductor to travel at a different rate along the compensation region  144  as compared to the rate of travel of the differential signal of the radially inner conductor through another dielectric (e.g. plastic). In alternative embodiments, rather than air, the window may be filled with a different dielectric having different characteristics than the dielectric of the body  102  that allows the signal to travel at a faster rate. Additionally, in other alternative embodiments, the radially inner signal conductors (rather than, or in addition to, the radially outer conductor having the compensation region  144 ) may include compensation regions that travel through a dielectric having a different characteristic that slows the travel of the signal therethrough. 
   The compensation regions  144  generally have a longitudinal axis extending substantially parallel to the length of the conductor  116  extending from the mating contact  20  to the mounting contact  56 . In the illustrated embodiment, the compensation regions  144  are generally rectangular extensions extending radially outward from the radially outer signal conductor. In an exemplary embodiment, the compensations regions  144  extend at least partially into the gaps  124  created by the absence of at least part of the ground conductors. The number, size and shape of the compensation regions  144  may be selected to substantially reduce skew. For example, by increasing the size or number of compensation regions  144 , the skew may be reduced as compared to smaller or less compensation regions  144 . Additionally, the increased width in the compensation region  144  controls the impedance, as the impedance changes with the change in dielectric constant. 
   In an exemplary embodiment, the mounting contacts  56  of the signal conductors, shown in the figures as signal mounting contacts  150 , are different than the mounting contacts  56  of the ground conductors, shown in the figures as ground mounting contacts  152 . For example, the ground mounting contacts  152  are represented by eye-of-the-needle contacts and the signal mounting contacts  150  are represented by micro-compliant pins that have a reduced cross section as compared to eye-of-the-needle pins. However in alternative embodiments, different types of contacts may be used for either the signal or ground mounting contacts  150 ,  152  and the signal and ground mounting contacts  150 ,  152  may be the same types of contacts. 
   In the illustrated embodiment, the ground mounting contacts  152  are longer than the signal mounting contacts  150  and are mated to the circuit board prior to the signal mounting contacts  150  being mounted thereto. The ground mounting contacts  152  are designed to engage the circuit board prior to the signal mounting contacts  150  to provide alignment and/or keying for the signal mounting contacts  152 . For example, an alignment tolerance of the signal mounting contacts  150  may be less than a tolerance of the ground mounting contacts  152  such that the ground mounting contacts  152  are guided into respective mounting holes to more accurately align the signal mounting contacts  150  with respective signal mounting holes. Additionally, because the ground mounting contacts  152  are longer, and mounted within respective holes prior to the signal mounting contacts  150 , the mating force of the electrical connector  10  (shown in  FIG. 1 ) may be reduced as less than all of the mounting contacts  56  are engaging the holes at one time. 
   The signal mounting contacts  150  are generally smaller (e.g. narrower or have a reduced cross section) than the ground mounting contacts  152 . As such, and as illustrated in  FIG. 4 , while each of the mating contacts  56  has substantially the same centerline spacing (i.e. the centers of adjacent mounting holes on the circuit board are the same distance from each other), a spacing  154  between adjacent signal mounting contacts  150  is increased as compared to a spacing  156  between adjacent ground mounting contacts  152 . Additionally, the spacing  154  is increased as compared to a spacing  158  between the signal mounting contact  150  and the adjacent ground mounting contact  152 . The increased spacing  154  may reduce the impedance between the adjacent signal mounting contacts  150  which may increase the overall performance of the contact module assembly  50  as compared to contact module assemblies that use larger signal mounting contacts. For example, the increased spacing spreads the signals which reduces capacitive coupling with each other, which reduces impedance. Similarly, the signal mounting contacts  150  are received in vias or holes in the circuit board that have a corresponding reduced size or diameter. The reduced diameter of the vias similarly increases the spacing therebetween which may reduce the impedance. 
     FIG. 5  is a side view of an alternative embodiment of a lead frame  200  for another one of the contact module assemblies, such as the contact module assembly  50 B, shown in  FIG. 2 . The lead frame  200  is similar to the lead frame  100  in some aspects, and like reference characters of the lead frame  100  are utilized in  FIG. 5  to denote like features of the lead frame  200 . The lead frame  200  may be at least partially enclosed by a dielectric to form the body  102  of the contact module assembly  50 B. 
   The lead frame  200  includes the mating and mounting contacts  20 ,  56 , and the conductors  116  that extend along predetermined paths between each mating contact  20  to a corresponding mounting contact  56 .  FIG. 5  illustrates the conductors  116  and associated contacts  20 ,  56  arranged according to an exemplary pinout, that is different than the pinout (shown in  FIG. 4 ) for the contact module assembly  50 A. The lead frame  200  includes both ground and signal conductors, wherein the signal conductors are arranged as differential pairs. The lead frame  200  provides two ground conductors between each differential pair of signal conductors, such that a second pinout, as defined from the radially outer conductor, is signal-signal-ground-ground-signal-signal-ground-ground-signal-signal-ground-ground-signal-signal-ground. 
   The first and second pinouts are different from one another such that, when the contact module assemblies  50 A (having the lead frame  100  with the first pinout) is placed within the housing  12  (shown in  FIGS. 1 and 2 ) adjacent to at least one of the contact module assemblies  50 B (having the lead frame  200  with the second pinout), then the signal contacts are at least partially offset with respect to one another. By staggering the signal conductors of adjacent contact module assemblies  50 A,  50 B, the electrical performance of the electrical connector  10  may be increased, such as by reducing crosstalk. Additionally, by providing pinouts having double ground conductors between the differential pairs, the spacing between each differential pair of signal conductors is increased further than if only a single ground conductor was positioned therebetween, thus reducing the crosstalk even further. 
   As with the lead frame  100 , the conductors  116  of the lead frame  200  that define the signal conductors extend entirely between the respective mating and mounting contacts  20 ,  56 . However, the conductors  116  defining ground conductors extend only partially between the respective mating and mounting contacts  20 ,  56  to form the gaps  124 . The trenches  126  in the body  102  may be provided along the gaps  124 . The conductors  116  defining the ground conductors have mating contact terminals  120  proximate the mating contacts  20 , and the conductors  116  defining the ground conductors have mounting contact terminals  122  proximate the mounting contacts  56 . Adjacent ground conductors form the ground pads  136  that receive the commoning member  60  (shown in  FIG. 2 ). Each of the conductors  116  defining signal conductors include compensation regions  144  that may be exposed by windows  146  in the body  102 . As with the lead frame  100 , the signal mounting contacts  150  of the signal conductors of the lead frame  200  are different than the ground mounting contacts  152 . For example, the ground mounting contacts  152  are represented by eye-of-the-needle contacts and the signal mounting contacts  150  are represented by micro-compliant pins that have a reduced cross section as compared to eye-of-the-needle pins. 
     FIG. 6  is an assembled view of the contact module assembly  50 A (shown in  FIG. 2 ), with an exemplary commoning member  60  affixed thereto. While  FIG. 6  illustrates the contact module assembly  50 A, having the lead frame  100  (shown in  FIG. 4 ), it is realized that the contact module assembly  50 B (shown in  FIG. 2 ), that includes the lead frame  200  (shown in  FIG. 5 ) would include a similar commoning member  60 . 
   During assembly, the commoning member  60  is mounted to the contact module assembly  50 A. The contacts  62  of the commoning member  60  are electrically and mechanically connected to the ground pads  136  (shown in  FIG. 4 ) to electrically common each ground pad  136  to one another. In some embodiments, the commoning member  60  is connected to less than all of the ground pads  136 . When installed, the commoning member  60  defines a ground plane that is oriented parallel to, but in a non-coplanar relation with, the lead frame plane. Because there are no redundant grounds between the signal conductors, the noise persistence of the contact module assembly  50 A may be reduced, as compared to contact module assemblies that have ground conductors in plane, and in between respective ones of the signal conductors. 
   In an exemplary embodiment, when the commoning member  60  is installed, the commoning member  60  covers each of the signal conductors of the lead frame  100 . As such, the commoning member may effectively shield each of the signal conductors from an adjacent contact module assembly when the contact module assemblies are assembled within the housing  12  (shown in  FIGS. 1 and 2 ). 
   It is to be understood that the above description is intended to be illustrative, and not restrictive. For example, the above-described embodiments (and/or aspects thereof) may be used in combination with each other. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its scope. Dimensions, types of materials, orientations of the various components, and the number and positions of the various components described herein are intended to define parameters of certain embodiments, and are by no means limiting and are merely exemplary embodiments. Many other embodiments and modifications within the spirit and scope of the claims will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Moreover, in the following claims, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements on their objects. Further, the limitations of the following claims are not written in means—plus-function format and are not intended to be interpreted based on 35 U.S.C. § 112, sixth paragraph, unless and until such claim limitations expressly use the phrase “means for” followed by a statement of function void of further structure.