Patent Abstract:
A modular electrical assembly that includes a first enclosure that physically couples to a second enclosure to form a modular stackup arrangement. The first enclosure having a connection to an electrical ground for discharging electrostatic discharge (ESD) energy of ESD events of the modular electrical assembly. The first enclosure configured to enclose first circuitry and comprising at least one generally flat surface to electrically couple to the second enclosure. The second enclosure configured to enclose second circuitry and comprising at least one surface with a plurality of raised contact nodes arranged such that when in contact with the one surface of the first enclosure electrostatic discharge energy is directed over the raised contact nodes to the one surface of the first enclosure for discharging portions of the ESD energy through the electrical ground of the first enclosure.

Full Description:
RELATED APPLICATIONS 
     This application is a continuation of, and claims priority to, U.S. patent application Ser. No. 13/160,880, filed on Jun. 15, 2011, entitled “ELECTROSTATIC DISCHARGE PROTECTION FOR MODULAR EQUIPMENT.” 
    
    
     TECHNICAL FIELD 
     Aspects of the disclosure are related to the field of equipment enclosures and enclosure interfacing, and in particular, electrostatic discharge (ESD) protection in modular equipment. 
     TECHNICAL BACKGROUND 
     Equipment enclosures are typically employed to encase electronic components, such as circuit card assemblies, printed circuit boards, discrete electrical components, or other electrical equipment. The equipment enclosures provide protection from the surrounding environment, such as dust, dirt, vibration, electrical interference, or other environmental protection. Also, when electronic equipment is used in human-equipment environments, such as when a human operator must interact with the equipment, electrostatic discharge (ESD) events can occur. ESD events can include static electrical discharges from a human operator or handler of electronic equipment to the equipment itself, among other events. The ESD energy typically follows a path to an electrical ground from the ESD source, such as a finger or clothing. However, the ESD energy may pass through sensitive electrical components, such as integrated circuits, along the path to electrical ground, either causing temporary disruption or permanently damaging the sensitive equipment. 
     In modular equipment, such as when multiple equipment enclosures are stacked to form the equipment, gaps can exist between the enclosures or modules which can allow ESD energy to be transported along unpredictable or undesirable routes. Conductive gaskets, foams, or meshes can aid in sealing the gaps between modules. However, these gaskets add manufacturing costs and extra parts to equipment assemblies, and can be unsuited for certain environmental or industrial conditions. 
     Overview 
     What is disclosed is a modular electrical assembly. The modular electrical assembly comprises a modular stackup arrangement of a first enclosure and a second enclosure. The first enclosure physically couples to the second enclosure to form the modular stackup arrangement. The first enclosure includes a connection to an electrical ground for discharging electrostatic discharge (ESD) energy of ESD events of the modular electrical assembly. The first enclosure is configured to enclose first circuitry and comprises at least one generally flat surface to electrically couple to the second enclosure. The second enclosure is configured to enclose second circuitry and has at least one surface with a plurality of raised contact nodes arranged such that when in contact with the generally flat surface of the first enclosure electrostatic discharge energy is directed over the raised contact nodes to the first enclosure for discharging portions of the ESD energy through the electrical ground of the first enclosure. 
     What is also disclosed is a modular electrical assembly that includes a first enclosure that physically couples to a second enclosure to form the modular stackup arrangement. The first enclosure has a connection to an electrical ground for at least discharging electrostatic discharge (ESD) energy of ESD events of the modular electrical assembly. The first enclosure is configured to enclose first circuitry and has at least one surface with a plurality of raised contact nodes such that when in contact with a generally flat surface of the second enclosure, at least portions of the ESD energy received at the second enclosure is directed over the raised contact nodes from the generally flat surface of the second enclosure for discharging the portions of the ESD energy through the electrical ground of the first enclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. While several embodiments are described in connection with these drawings, the disclosure is not limited to the embodiments disclosed herein. On the contrary, the intent is to cover all alternatives, modifications, and equivalents. 
         FIG. 1  is a system diagram illustrating an example of an equipment enclosure system. 
         FIG. 2  is a system diagram illustrating an example of an equipment enclosure system. 
         FIG. 3  is a system diagram illustrating an oblique projection of an example of an equipment enclosure system. 
         FIG. 4  is a view diagram illustrating examples of raised contact nodes. 
         FIG. 5  is a flow diagram illustrating a method of manufacturing an equipment enclosure system. 
         FIG. 6  is a system diagram illustrating an oblique projection of an example of a modular visualization display panel. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1 and 2  are system diagrams illustrating equipment enclosure system  100 . Equipment enclosure system  100  could comprise a modular equipment enclosure system, such as a modular visualization display panel, human-machine interface equipment, computer system enclosure, control panel enclosure system, graphics terminal, operator panel, operator interface, or industrial computer, among other modular equipment enclosures.  FIGS. 1 and 2  include first module  110 , second module  120 , and raised contact nodes  130 - 132 .  FIG. 2  also includes ESD source  140 , electrostatic discharge  142 , and discharge paths  150 . 
     First module  110  includes at least one surface and a connection to electrical ground  115 . The one surface of first module  110  in this example is the surface shown facing second module  120 , although other surfaces could be referenced. Electrical ground  115  includes an electrical connection to a ground potential for electrical equipment associated with first module  110  or second module  120 . Electrical ground  115  could include a chassis ground, digital ground, analog signal ground, neutral lead, common lead, or other electric reference potential connection. 
     Second module  120  also includes at least one surface. The one surface of second module  120  in this example is the surface shown facing first module  110 , although other surfaces could be referenced. The one surface of second module  120  includes raised contact nodes  130 - 132  arranged on the one surface of second module  120  such that when in contact with the one surface of first module  110 , electrostatic discharge (ESD) energy is directed over at least one of raised contact nodes  130 - 132  to the one surface of first module  110 . Although raised contact nodes  130 - 132  are arranged on the one surface of second module  120  in this example, it should be understood that raised contact nodes  130 - 132  could instead be arranged on the one surface of first module  110  in other examples, including combinations of arrangements thereof. 
     First module  110  and second module  120  could each be comprised of a conductive material, such as a metal composition. In other examples, first module  110  or second module  120  could be partly comprised of a non-conductive material, and the one surface of each module is comprised of a conductive material. First module  110  and second module  120  could each enclose electrical circuits, circuit card assemblies, printed circuit boards, subassemblies, user-accessible ports, displays, user-interface equipment, or other electrical or mechanical equipment. Either of first module  110  and second module  120  could act as a Faraday cage surrounding electronic components. Although first module  110  and second module  120  are shown in  FIGS. 1 and 2  in a two-dimensional side view representation for clarity, it should be understood that first module  110  and second module  120  could have been shown as three-dimensional enclosures, such as casings, equipment chassis, or other equipment enclosures, with raised contact nodes  130 - 132  arranged along a seam or edge of first module  110  or second module  120 . 
     Raised contact nodes  130 - 132  each comprise raised protrusions or bumps above the one surface of second module  120 , disposed on the one surface of second module  120 . In some examples, raised contact nodes  130 - 132  are each formed from the same material as the one surface of second module  120 , such as being machined from the same piece of material or formed in the same casting. In typical examples, raised contact nodes  130 - 132  each comprise a conductive material, such as a metal composition. The conductive material could be of the same composition as the one surface of second module  120 , the same composition as the one surface of first module  110 , or of a different composition. It should be understood that the shape of raised contact nodes  130 - 132  shown in  FIGS. 1 and 2  is merely representative of the raised protrusions above the one surface of second module  120 . Other shapes could be employed for each of raised contact nodes  130 - 132 , such as a polyhedron, pyramid, dome, round, oblate spheroid, half-ovate, ellipsoid, hemisphere, spike, tapered, teardrop, or portions thereof. 
       FIG. 2  includes ESD source  140 , as represented by a finger. Other sources of ESD energy could be employed, such as clothing, equipment, peripheral connectors, peripheral equipment, or other environmental sources. ESD source  140  discharges electrical energy as an electrostatic discharge  142  into equipment enclosure system  100 . The first point where the ESD energy is transferred into equipment enclosure system  100  is on second module  120 . Exemplary discharge paths are shown in  FIG. 1 , namely discharge paths  150 . In this example, the ESD energy is discharged along discharge paths  150  through second module  120 , over raised contact nodes  130 - 131 , and to first module  110 . Since first module  110  is connected to electrical ground  115 , the ESD energy is eventually discharged to electrical ground  115  once conducted to first module  110 . It should be understood that other electrostatic discharge paths could have been taken by electrostatic discharge  142 , and discharge paths  150  are merely representative of possible paths through at least one of raised contact nodes  130 - 132 . ESD energy may follow the outer surface of enclosure  120  to raised contact nodes  130 - 132 . 
     Typically, ESD energy will follow the path of least resistance to a lower voltage potential, such as electrical ground  115 . Without raised contact nodes  130 - 132 , the ESD energy of electrostatic discharge  142  would find an undesirable, unpredictable path to electrical ground  115  or to other ground potentials. This undesirable path could include a path through electronic circuits, or elements thereof, such as decoupling capacitors, integrated circuits, transient protection circuitry, printed circuit boards, printed circuit board mounting elements such as standoffs and screws, or other undesirable paths. However, with the addition of conductive bumps, such as raised contact nodes  130 - 132 , the ESD energy of electrostatic discharge  142  is directed through second module  120  and along at least one of raised contact nodes  130 - 132  through discharge paths  150  to electrical ground  115 . The elements of electronic circuits of first module  110  or second module  120  are thus protected from ESD energy. The enclosure-to-enclosure discharge pathway is shown in this example, and thus sensitive electronic circuitry is not traversed with excess ESD energy. 
     In other examples, the ESD energy may only be partially carried by surfaces of the enclosures or modules, and individual internal electrical components may still receive some exposure to ESD energy. However, individual internal electrical components would instead be only exposed to less than the total ESD energy of electrostatic discharge  142  due to multiple discharge paths by placement of raised contact nodes. For example, individual ones of discharge paths  150  could traverse electrical circuitry of second module  120  or first module  110 . However, since the total ESD energy is dispersed across multiple ones of raised contact nodes  130 - 132 , individual components in the electrical circuitry may only see a portion of the total ESD energy. Further examples are discussed herein. 
       FIG. 3  is a system diagram illustrating an oblique projection of equipment enclosure system  300 . Equipment enclosure system  300  is a modular equipment enclosure system, which includes logic module  310  and communication module  320 . Logic module  310  and communication module  320  join together in a stackable configuration, where each module mates with the other along a mating surface, namely first mating surface  311  for logic module  310  and second mating surface  321  for communication module  320 . Portions of logic module  310  and communication module  320  could overlap each other when joined in some examples. Although two modules are shown in  FIG. 3 , equipment enclosure system  300  could include further stacked modules or different modules, such as a display module, user interface module, machine interface module, control panel, or other modules. Also, although logic module  310  and communication module  320  are shown a distance apart in  FIG. 3 , both modules would be joined closely to each other in normal usage. The semi-exploded view in  FIG. 3  is employed for clarity. 
     In this example, logic module  310  includes electronic logic portions, such as processing system portions or user-interface portions and includes peripheral port  312 . Peripheral port  312  is a user-accessible connection for a peripheral device, such as for connecting a keyboard, mouse, storage device, or other peripheral for use with logic module  310 . In this example, peripheral connector  340  is intended to mate with peripheral port  312 . Peripheral port  312  could be a universal-serial bus (USB) port, Ethernet port, flash memory interface, mass storage device interface, serial port, video port, audio port, or other data input or output port. In typical examples, peripheral port  312  includes a conductive surround or shield portion which allows for a conductive physical connection between elements of peripheral port  312  with the case of logic module  310 , such as a metallic shield surrounding the signaling pins, power pins, or electrical contacts of peripheral port  312 . 
     Logic module  310  also includes conductive bumps  315 . Conductive bumps  315  are disposed along a first edge of first mating surface  311 . The first edge could be the longest linear edge of first mating surface  311  although other configurations could be employed, such as an edge with the greatest potential or possibility for physical or electrical gapping, as in the longest mating edge, the most curved edge, or the edge with the most complex edge features, among others. Logic module  310  and communication module  320  join together in a stackable configuration, and couple through conductive bumps  315 . Conductive bumps  315  allow discrete modules to electrically interface through conductive bumps  315 , namely second mating surface  321  of communication module  320  contacts first mating surface  311  of logic module  310  through conductive bumps  315 . When first mating surface  311  is in contact with second mating surface  321 , electrostatic discharge (ESD) energy received by logic module  310  is directed over at least one of conductive bumps  315  to second mating surface  321 . 
     Conductive bumps  315  each comprise halved-ellipsoid raised protrusions which protrude above first mating surface  311 . In this example, conductive bumps  315  are each formed from the same material as first mating surface  311 , such as being machined from the same piece of material or formed in the same casting. Conductive bumps  315 , and likewise first mating surface  311 , comprise a conductive material, such as a metal composition. The conductive material could be of the same composition as second mating surface  321 , or a different composition. 
     Communication module  320  also encloses electronic circuit portions, which may include similar or different types of electronic circuit portions as logic module  310 . Communication module  320  interfaces elements of logic module  310  to further systems and equipment through interface cable  325 . Communication module  320  is attached electrically to interface cable  325  in this example. The electrical connection could be achieved through a ground wire, shield, braid, or other conductive coupling to interface cable  325 . Interface cable  325  could include further elements, such as signaling wires, optical fiber, communication cables, or other communication, power, or grounding elements. In this example, interface cable  325  is also in electrical connection with a ground potential, not shown for clarity. When ESD energy is received by second mating surface  321 , the ESD energy is conducted by communication module  320  to interface cable  325  for discharge to a ground potential. 
     In this example, logic module  310  and communication module  320  are each modular cases, used to enclose electronic circuit portions, among other portions, and each includes a mating surface, namely first mating surface  311  and second mating surface  321 . The portions that each of logic module  310  and communication module  320  encase might only be partially encased in some examples. Also in this example, second mating surface  321  is formed from the same piece of material as the case of communication module  320 . Likewise, first mating surface  311  and conductive bumps  315  are formed from the same piece of material as the case of logic module  310 . 
     The ESD source is shown as peripheral connector  340  in  FIG. 3 . Other sources of ESD energy could be employed, such as clothing, humans, equipment, or other environmental sources. Peripheral connector  340  discharges electrical energy as an electrostatic discharge  342  into equipment enclosure system  300 . The first point where the ESD energy is transferred into equipment enclosure system  300  is at peripheral port  312  of logic module  310 . In this example, the ESD energy is discharged through a shield or surround portion of peripheral port  312  or peripheral connector  340  to the outside case surface of logic module  310  and then to first mating surface  311 . First mating surface  311  includes conductive bumps  315 , which contact second mating surface  321 , and the ESD energy is discharged across at least one of conductive bumps  315  to second mating surface  321 . The ESD energy is further discharged through communication module  320 , such as along the outer case surface of communication module  320  to interface cable  325 . 
     It should be understood that other electrostatic discharge paths be taken by electrostatic discharge  342 . For example, individual electrical components within logic module  310  or communication module  320  may still receive some exposure to ESD energy, but instead be only exposed to less than the total ESD energy of electrostatic discharge  342  due to multiple discharge paths dispersing the total ESD energy over multiple conductive bumps  315 . In this manner, any individual internal electrical component may see only a portion of the total ESD energy, as individual portions of the total ESD energy are directed through different discharge paths by individual ones of conductive bumps  315 . 
       FIG. 4  is a view diagram of illustrating examples of raised contact nodes. In  FIG. 4 , three examples of raised contact nodes are shown, although further configurations could be used. Each of the examples is shown in a side view and an end view to illustrate the shape of the raised contact nodes. Also, each of the examples could be comprised of the various materials described herein. The first example is rounded bump  400 , the second example is penetrating protrusion  410 , and the third example is tapered bump  420 . 
     Rounded bump  400  comprises a smooth, contoured top edge, similar to a halved ellipsoid or ovoid shape. Rounded bump  400  is disposed on a surface by the flat bottom side of rounded bump  400 , and configured to contact a mating surface through the contoured top side. Rounded bump  400  could be configured to deform the mating surface when in contact with the mating surface. 
     Penetrating protrusion  410  comprises a sharp, angled top edge, similar to a truncated pyramid or knife shape. Penetrating protrusion  410  is disposed on a surface by the flat bottom side of penetrating protrusion  410 , and configured to penetrate a mating surface through the sharp top side. Penetrating protrusion  410  could be configured to penetrate partially into a mating surface, possibly through a non-conductive layer of the mating surface to reach a conductive later of the mating surface. 
     Tapered bump  420  comprises a smooth, tapered top edge, similar to a halved teardrop shape. Tapered bump  420  is disposed on a surface by the flat bottom side of tapered bump  420 , and configured to contact a mating surface through the tapered top side. Tapered bump  420  could be configured to deform the mating surface when in contact with the mating surface. 
       FIG. 5  is a flow diagram illustrating a method of manufacturing an equipment enclosure system, such as equipment enclosure system  100 , equipment enclosure system  300 , or modular visualization display panel  600 , although other configurations could be employed. The method of  FIG. 5  could be employed in manufacturing a modular equipment enclosure system, such as a modular human-machine interface system, modular visualization display panel system, modular control panel, or other modular electronic enclosure system. 
     In  FIG. 5 , operation  501  includes forming a first casing from a first metal to enclose electronic circuits, where the first casing comprises a first mating surface and a plurality of raised contact nodes protruding beyond the first mating surface. In some examples, the first casing is machined from a bulk piece of material, such as a metal or metal alloy. In other examples, the first casing is cast in a mold using a metal or metal alloy. The first casing could include a hollow portion to encase or otherwise contain electronic circuitry, mechanical equipment, or other user-interface, processing, or communication equipment. The first mating surface could be any of the surfaces of the first casing, intended for mating or joining with another casing, mounting plate, or module, to form a stacked configuration with the first casing. 
     The plurality of raised contact nodes are disposed over the first mating surface, and configured to protrude above the first mating surface. The raised contact nodes could be raised protrusions, bumps, or other localized individual protrusions above the first mating surface. In typical examples, the raised contact nodes are disposed along a single outer edge of along the perimeter of the first mating surface. In further examples, the raised contact nodes are disposed along multiple edges of the first mating surface, or along the entire perimeter of the first mating surface. Raised contact nodes could also be disposed along internal portions of the first mating surface. The raised contact nodes could be formed from the first mating surface, such as being formed from the same bulk material as the first mating surface or the first casing, and thus could comprise the same metal or metal alloy. In examples of machining, the raised contact nodes would be machined from the same bulk piece of material, such as with a lathe or computer-aided machining equipment. In examples of casting, impressions of the raised contact nodes could be integrated into the mold so as to form from the same material as the first casing when the material is injected into the mold. In yet further examples, the raised contact nodes are formed separately from the first mating surface or the first casing and attached to the first mating surface, such as using fasteners, conductive adhesive, welds, solder, or other electrically conductive attachment techniques. In even further examples, the raised contact nodes could be formed from welds or solder material itself. 
     Operation  502  includes forming a second casing from a second metal, where the second casing comprises a second mating surface. In some examples, the second casing is machined from a bulk piece of material, such as a metal or metal alloy. In other examples, the second casing is cast in a mold using a metal or metal alloy. As with the first casing, the second casing could include a hollow portion to encase or otherwise contain electronic circuitry, mechanical equipment, or other user-interface, processing, or communication equipment. The second mating surface could be any of the surfaces of the second casing, intended for mating or joining with another casing, mounting plate, or module, to form a stacked configuration with the second casing. 
     Operation  503  includes coupling the first mating surface of the first casing to the second mating surface of the second casing through the raised contact nodes, where the raised contact nodes contact the second mating surface to discharge electrostatic discharge energy between the first mating surface and the second mating surface. The first casing is joined to the second casing in a stacked configuration in this example, where the first casing joins to the second casing at the associated mating surfaces. The first casing and the second casing could be joined to each other by fasteners, such as screws, or by an adhesive, weld, or other coupling devices or materials, including combinations thereof. The raised contact nodes of the first mating surface conductively contact the second mating surface, and thus conductively couple the first mating surface to the second mating surface. Other points of conductive contact could exist between the first mating surface and the second mating surface. However, the raised contact nodes typically provide a less-resistive path or a more repeatable conductive path for electrical contact between the two surfaces. 
     In some examples, the raised contact nodes are configured to deform the second mating surface when the first casing is coupled to the second mating surface. In further examples, the raised contact nodes are configured to penetrate the second mating surface when the first casing is coupled to the second mating surface. The penetration depth could be partial or total into the second mating surface. The second mating surface could comprise a non-conductive layer deposited over a conductive layer, such as a coating, paint, anodized layer, or other non-conductive layer over a metal or metal alloy. In examples of a partial penetration depth, the raised contact nodes could be configured to penetrate the non-conductive layer of the second mating surface, such as a coating, paint, anodized layer, or other non-conductive layer, and make electrical contact with another layer of the second mating surface, such as the underlying bulk conductive material of the second casing. 
     The material composition of any of the first casing, first mating surface, second casing, second mating surface, or raised contact nodes could each comprise any conductive material, such as such as a metal, a metal alloy, composite material, laminated material, or could comprise polymers or other non-conductive materials impregnated with conductive particles, fibers, or plates. The metal or metal alloys could include aluminum, magnesium, iron, steel, zinc, beryllium, or any other electrically conductive metal, alloy, or composite material, including combinations thereof. 
     In further examples, the first mating surface and the second mating surface are each comprised of different metal compositions. The different metal compositions could be susceptible to galvanic corrosion, such as when using dissimilar metals. The raised contact nodes could be comprised of an intermediate material composition, and a different composition than both the first mating surface and the second mating surface. The composition of the raised contact nodes could include a metal or metal alloy which is compatible with both the first mating surface and the second mating surface, thus acting as a conductive buffer between the dissimilar metals of the first mating surface and the second mating surface. The raised contact nodes could thus prevent or reduce galvanic corrosion of the first mating surface or second mating surface. Also, redox potentials could be brought closer by the material selection discussed herein to ensure that galvanic corrosion will be minimized. When a different material composition is used for the raised contact nodes, the raised contact nodes could be formed separately from the first mating surface and attached with welds, conductive adhesives, solder, or other attachment techniques. 
     The raised contact nodes are employed to transfer ESD energy from the first mating surface to the second mating surface, and likewise from the first casing to the second casing. Furthermore, the raised contact nodes are employed to disperse the ESD energy over multiple discharge paths. The raised contact nodes can augment other ESD protection schemes, which could include mechanical elements such as conductive gaskets, conductive meshes, conductive fingers, or electrical protection devices such as transient voltage suppression (TVS) diodes, varistors, gas discharge tubes, capacitors, resistors, inductors, or other mechanical or electrical electronic transient protection schemes and elements, including combinations thereof. 
       FIG. 6  is a system diagram illustrating a modular visualization display panel  600 . Modular visualization display panel  600  is a modular equipment enclosure system, which includes communication module  610 , logic module  620 , and display module  630 . Communication module  610 , logic module  620 , and display module  630  join together in a stackable configuration, where each module joins with another along opposing mating surfaces. Although three modules are shown in  FIG. 6 , modular visualization display panel  600  could include further stacked modules or different modules. Also,  FIG. 6  shows modular visualization display panel  600  in an exploded view for clarity, and the individual modules would be joined closely to each other in normal usage. Each module of modular visualization display panel  600  includes a casing which surrounds internal components of each module. The individual casings also include holes for ventilation and inter-module fasteners. It should be understood that the naming of each module is merely for clarity and should not imply a necessary function of the module. 
     In this example, logic module  620  includes electronic logic portions, such as processing system portions or user-interface portions and also includes raised contact nodes  621  and user ports  625 . The electronic logic portions of logic module  620  are encased in a casing of logic module  620 , which comprises a metallic material, such as aluminum. Serpentine air ventilation channels are also formed from the casing of logic module  621 , as shown on the left top side of logic module  620 . It should be understood that other examples may lack the ventilation channels. 
     The casing of logic module  620  includes user ports  625 . User ports  625  are user-accessible connections for peripheral devices, such as for connecting a keyboard, mouse, storage device, network cable, serial cable, or other peripherals for use with modular visualization display panel  600 . Each of user ports  625  includes a conductive surround or shield portion which allows for a conductive physical connection between grounding elements of user ports  625  with the case of logic module  620 , such as a metallic shield surrounding the signaling pins, power pins, or electrical contacts of user ports  625 . 
     The casing of logic module  620  also includes raised contact nodes  621 . Raised contact nodes  621  are disposed at periodic points along a rim of logic module  620  which mates with communication module  610 . In  FIG. 6 , raised contact nodes  621  are disposed on the far, top edge of logic module  620 , from the perspective of the observer. Also, raised contact nodes  621  are disposed along the longest edge mating to communication module  610 , although other configurations could be used. Raised contact nodes  621  are positioned along the most ESD vulnerable side of logic module  620  in this example, and positioned near the edge of the casing to redirect ESD energy away from vulnerable internal areas. Logic module  620  and communication module  610  join together in a stackable configuration, and couple through raised contact nodes  621 . Raised contact nodes  621  allow communication module  610  and logic module  620  to electrically interface through raised contact nodes  621 , and to improve contiguous mating by reducing gaps between the two mated modules. When logic module  620  and communication module  610  are joined together, electrostatic discharge (ESD) energy received by logic module  620  is at least partially dispersed over at least one of raised contact nodes  621  to communication module  610 . Raised contact nodes  621  each comprise halved teardrop-shaped raised protrusions which protrude above the surface of logic module  620  which mates with communication module  610 . Raised contact nodes  621  are each formed from the same material as the casing of logic module  621 , such as being machined from the same piece of material or formed in the same casting. Raised contact nodes  621 , and likewise the casing of logic module  621 , comprise a conductive material, such as a metal composition. The conductive material could also be of the same composition as the casing of communication module  610 , or a different composition. 
     Communication module  610  also encloses electronic circuit portions, which may include similar or different types of electronic circuit portions as logic module  620 . Communication module  610  interfaces elements of logic module  620  to further systems and equipment through external connector  615 . A metallic surround or shroud of external connector  615  is electrically bonded to the casing of communication module  610 , or could be formed of the same bulk material as communication module  610 . In operation, an external cable could be connected to external connector  615  for interfacing modular visualization display panel  600  to other systems and equipment. A ground wire, shield, braid, or other conductive coupling could provide an electrical ground connection to external connector  615  and likewise to the casing of communication module  610 . When ESD energy is received at the casing of communication module  610 , the ESD energy is conducted by communication module  610  to external connector  615  for discharge to a ground potential. 
     Display module  630  encloses electronic circuit portions, a display screen, or other visual user interface elements of modular visualization display panel  600 . In operation, a user of modular visualization display panel  600  would view the display screen of display module  630  and possibly interact with a display screen, touchscreen, buttons, dials, or other user interface elements associated with modular visualization display panel  600 . Display module  630  joins with logic module  620  and communication module  610  in a stackable configuration to form modular visualization display panel  600 . The casing of display module  630  includes chassis ground  616 . In operation, an external cable could be connected to chassis ground  616  for interfacing modular visualization display panel  600  to a chassis ground electrical potential. A ground wire, shield, braid, or other conductive coupling could provide an electrical chassis ground connection to chassis ground  616  and likewise to the casing of display module  630 . When ESD energy is received at the casing of display module  630 , the ESD energy is conducted by display module  630  to chassis ground  616  for discharge to a ground potential. In this example, logic module  620  and display module  630  are mated by several screws. 
     In operation, an ESD source could discharge ESD energy to any of user ports  625 . Sources of ESD energy could include humans, clothing, cabling, connectors, equipment, or other environmental sources. In this example, the ESD energy discharged at user ports  625  would be conducted through a shield or surround portion of user ports  625  to the casing of logic module  620 . The casing of logic module  620  includes raised contact nodes  621 , which contact the casing of communication module  610 , and at least a portion of the ESD energy is dispersed by at least one of raised contact nodes  621  to the casing of communication module  610 . The ESD energy could be further discharged through communication module  610 , such as along the outer case surface of communication module  610  to external connector  615 . It should be understood that other electrostatic discharge paths be taken by ESD energy, such as to display module  630  and chassis ground  616 , although in this example, at least a portion of the ESD energy would be directed along at least one of raised contact nodes  621  when traversing between logic module  620  and communication module  610 . 
     Raised contact nodes  621  provide a way to redirect ESD energy safely around critical components of logic module  620 , and utilize the casing of logic module  620  to provide the ESD protection. By using multiple raised contact nodes, placed periodically along the rim of logic module  620 , ESD energy can be disbursed along controlled, parallel paths, instead of a single path, a serial path, or unintentional paths through sensitive or vulnerable electrical components. Although raised contact nodes  621  could be augmented by further ESD protection devices and techniques, such as gaskets, foams, wide chassis ground interfaces, and distributed chassis to ground capacitances, these additional devices and techniques are not required in the examples herein. 
     Furthermore, by directing ESD energy across multiple ones of raised contact nodes  621 , even if the ESD energy still takes a path through sensitive electrical components of communication module  610  or logic module  620 , the total ESD energy would be dispersed or divided amongst the multiple ESD paths induced by the multiple ones of raised contact nodes  621 . As a further example, ESD energy could be designed to traverse sensitive electrical components, such as through electrical components of communication module  610  or logic module  620 , but since the ESD energy is dispersed across multiple ones of raised contact nodes  621 , the individual portion of the ESD energy experienced by any individual electrical component is low enough to be within the ESD tolerances of the individual electrical components. Thus, multiple electrical components could share the total ESD energy as divided or dispersed by raised contact nodes  621  across a larger distance. 
     The spacing of raised contact nodes  621  is determined at a distance that minimizes current flow in any one area of logic module  620  or communication module  610 , where the current flow is induced from ESD events. For example, the distance between raised contact nodes  621  could be optimized for a separation that allows for surface variation and energy dispersion. The height of raised contact nodes  621  is determined to avoid excessive standoff or vertical height between modules and of the contact nodes themselves, while still ensuring good physical and electrical contact between modules. The height of raised contact nodes  621  could be chosen to optimize contact pressure between modules. For example, within tolerances of the logic module casing and the communication module casing, the height of raised contact nodes  621  could be selected to provide proper seating of any mating electrical connectors between the modules. 
     Advantageously, raised contact nodes  621  can decrease the susceptibility of modular visualization display panel  600  to ESD events, while minimizing impact on the packaging associated with the individual modules. Raised contact nodes  621  provide energy guidance and dispersion to minimize ESD aggression toward critical circuit operation. Furthermore, extra parts and equipment for ESD protection can be reduced or eliminated by utilizing raised contact nodes  621  to coerce ESD energy along predetermined paths and along the casings and mating surfaces of individual modules. By reducing the need for specialized parts such as gaskets, foams, and discrete electrical protection components, modular visualization display panel  600  is better suited to extreme environments, such as industrial, chemical, or marine environments for machine equipment automation and control. 
     The included descriptions and figures depict specific embodiments to teach those skilled in the art how to make and use the best mode. For the purpose of teaching inventive principles, some conventional aspects have been simplified or omitted. Those skilled in the art will appreciate variations from these embodiments that fall within the scope of the invention. Those skilled in the art will also appreciate that the features described above can be combined in various ways to form multiple embodiments. As a result, the invention is not limited to the specific embodiments described above, but only by the claims and their equivalents.

Technology Classification (CPC): 8