Corrosion prevention cover for module connector in a network device

In one embodiment, an apparatus includes a cover configured for installation over a connector mounted on a printed circuit board and operable to couple a module to the printed circuit board, the cover comprises a lower surface for contact with the printed circuit board and a slot for receiving the module for attachment of the module to the connector. The cover encloses contacts at the connector for mating with the module and the printed circuit board to prevent corrosion of the contacts.

TECHNICAL FIELD

The present disclosure relates generally to network devices in a communications network, and more particularly, to corrosion protection for components in a network device.

BACKGROUND

Network communications systems utilize network devices that include complex and sensitive electronic components. The network devices are typically designed to operate in a controlled environment such as data centers and central offices with controlled temperature, humidity, and air quality. However, network equipment is being deployed closer to a user base and deployments are often exposed to non-protected or partially protected outdoor environments. Network devices deployed in uncontrolled remote areas with high humidity, salt fog, hygroscopic dust, and other contaminants in the air often exhibit severe corrosion problems, which may reduce the operational life of the equipment or FRUs (Field Replaceable Units) within the equipment.

DESCRIPTION OF EXAMPLE EMBODIMENTS

Overview

In one embodiment, an apparatus generally comprises a cover configured for installation over a connector mounted on a printed circuit board and operable to couple a module to the printed circuit board, the cover comprises a lower surface for contact with the printed circuit board and a slot for receiving the module for attachment of the module to the connector. The cover encloses contacts at the connector for mating with the module and the printed circuit board to prevent corrosion of the contacts.

In one or more embodiments, the slot is defined by resiliently deformable flexible members configured to form a seal with outer surfaces of the module when the module is inserted into the cover. The resiliently deformable flexible members may comprise outer surfaces tapered towards the slot.

In one or more embodiments, the cover may be configured for sliding engagement with a 90 degree connector. In one or more embodiments, the cover may be configured for sliding engagement with a vertical connector.

In one or more embodiments, the cover comprises openings for receiving arms of the connector positioned adjacent to the module when the module is inserted into the connector.

In one or more embodiments, the cover comprises openings for receiving locking members of the connector.

In one or more embodiments, the cover defines an enclosure to protect the contacts from moisture and contaminants within cooling air flowing over the printed circuit board when installed in an operating network device.

In one or more embodiments, the cover reduces dissipation of heat from an interior of the cover when the cover is installed over the connector.

In one or more embodiments, the cover allows for an increase in temperature within an enclosure defined by the cover and the printed circuit board to reduce relative humidity within said enclosure and further prevent corrosion of the contacts when the cover is installed over the connector.

In another embodiment, an apparatus generally comprises a connector for mounting on a printed circuit board and coupling a module to the printed circuit board, the connector comprising contacts for mating with the module and the printed circuit board, a removable cover enclosing the contacts and comprising a lower surface for engagement with the printed circuit board, and a sealant located between at least a portion of an internal surface of the cover and the connector. The cover and the sealant reduce exposure of the contacts to contaminants and prevent corrosion of the contacts.

In yet another embodiment, an apparatus generally comprises a module, a printed circuit board, a connector mounted on the printed circuit board and coupling the module to the printed circuit board, and a cover enclosing contacts at a module to connector interface and a connector to printed circuit board interface, the cover comprising a slot for insertion of the module into the connector and removal of the module from the connector.

Further understanding of the features and advantages of the embodiments described herein may be realized by reference to the remaining portions of the specification and the attached drawings.

EXAMPLE EMBODIMENTS

The following description is presented to enable one of ordinary skill in the art to make and use the embodiments. Descriptions of specific embodiments and applications are provided only as examples, and various modifications will be readily apparent to those skilled in the art. The general principles described herein may be applied to other applications without departing from the scope of the embodiments. Thus, the embodiments are not to be limited to those shown, but are to be accorded the widest scope consistent with the principles and features described herein. For purpose of clarity, details relating to technical material that is known in the technical fields related to the embodiments have not been described in detail.

Network communications devices are increasingly being used in uncontrolled or partially uncontrolled environments that have different conditions than a data center or central office. In many of these deployments, the network device has no environmental protection (or only partial protection) and may be directly exposed to ambient air. Based on the climatic conditions of the area, the ambient air may not only carry a lot of dust and moisture, but also different chemical compounds. The network device may be subjected to adverse environmental factors including temperature and humidity extremes, airborne particulates, chemical pollutants, and other contaminants. The environment in which the network device operates may not be conducive to prolonged operation and life of the equipment.

Although all types of outdoor equipment face these issues, the severity of the failure is typically higher for forced air cooled devices due to the high flow rate of contaminated air within equipment enclosures. In a forced air cooled network device, the contaminants in the air may react with metal used in electronic components and cause corrosion. Deployment of network devices in the presence of uncontrolled contamination in cooling air (e.g., dust, moisture, abrasive chemicals, water soluble salts, etc.), may lead to damage to FRUs (Field Replaceable Units). Failure of the network device or components may occur very quickly in an uncontrolled environment. These failures are not predictable and therefore create service interruption and high costs for replacement units. Since these failures are often not recoverable, the downtime associated with these failures may be significant.

One method for protecting components from corrosion is a conformal coating process that coats a printed circuit board with a thin film for protection of surface mounted components from corrosion. However, when the conformal coating is applied, reworking of components becomes difficult. For devices such as memory modules (e.g., DIMMs (Dual In-line Memory Modules)), eUSBs (embedded Universal Serial Buses), mSATA (miniature Serial Advanced Technology Attachment) drives, batteries, power supplies, SIM (Subscriber Identity Module) cards, memory sticks (M2), or other components that are coupled to the printed circuit board through a connector, the area around the connector cannot be coated.

The embodiments described herein provide a corrosion prevention cover (sleeve, shell, housing, enclosure, boot) configured to enclose and protect exposed contacts (e.g., pins, fingers, gold fingers, pads, leads, copper leads, wires) at a connector to printed circuit board interface and a connector to module interface for preventing (reducing, delaying) corrosion of the contacts. The corrosion prevention cover may be used, for example, to protect pins of a socket and contact fingers of a memory module that cannot be coated to help improve their durability when network devices are deployed in harsh environments.

As described in detail below, in one or more embodiments, an apparatus may comprise a cover for protecting a connector mounted on a printed circuit board and coupling (electrically, communicatively, physically) a module to the printed circuit board. The cover encloses (substantially encloses) contacts mating with the module and in communication with the printed circuit board (e.g., leads on the connector mating with fingers on the module, leads coupling the connector to the PCB) and comprises a slot for insertion or removal of the module into or from the connector and a lower surface for contact with the PCB. The cover reduces exposure of the contacts to contaminants (e.g., moisture, dust, salt, etc.) to prevent corrosion of the contacts.

It is to be understood that the term “module” as used herein may refer to any electronic device, field replaceable unit, card, memory device, drive, battery, USB, power supply, board, or other element coupled to a printed circuit board through a connector. The term “connector” as used herein may refer to a socket, receptacle, tray, arms, port, or other interface operable to couple the module to the printed circuit board. As described in detail below, contacts (pins, leads, contact members, fingers, gold fingers, pads, wires, copper elements) of the connector and module may be exposed to environmental conditions when installed in the network device. The corrosion prevention cover is configured to enclose exposed contacts (e.g., contacts at the module to connector interface, contacts at the connector to PCB interface) to prevent (e.g., delay, reduce, or prevent) corrosion of the contacts. The corrosion prevention cover encloses the contacts to protect the contacts from moisture or contaminants that may be present, for example, in cooling air flowing over the components (module, connector, PCB).

Referring now to the drawings, and first toFIG. 1, a memory module (e.g., DIMM)10is coupled to a printed circuit board (PCB)12through a connector (module connector)14. A corrosion prevention cover16is installed over the connector14and mounted on the PCB12, and the DIMM10is inserted through an opening (e.g., slot described below with respect toFIG. 3) in the cover and attached to the connector (end portion of DIMM inserted into socket). The corrosion prevention cover16encloses exposed contacts at the module to connector interface and connector to PCB interface.

In the example shown inFIG. 1, the DIMM10is installed horizontally (e.g., 90 degrees relative to the PCB, generally parallel to the PCB) and the connector is referred to as a 90 degree or horizontal connector. The connector may also be configured for receiving the module at a different orientation (e.g., vertical connector as shown inFIG. 5or any other angle). The PCB12may comprise any number of components (chips, memory, processors, power supplies, etc.) arranged in any format. One or more modules coupled to the PCB12through a connector may be protected by a corrosion prevention cover in accordance with the embodiments described herein.

As described below, the cover16is formed from a flexible material to provide for ease of installation of the cover over the connector14, engagement of a bottom surface of the cover with the PCB12, and insertion and removal of the module10. The cover16is preferably configured with thin walls and a minimal footprint to prevent interference with adjacent components mounted on the PCB12.

As shown in the exploded view ofFIG. 2, the connector14comprises a plurality of exposed leads20(only a few shown for simplification) for electrical coupling of the connector to the PCB12. In the example shown inFIG. 2, the memory module10comprises a plurality of memory chips22(e.g., DRAM (Dynamic Random Access Memory) integrated circuits) and contacts (pins, fingers)24(only two shown for simplification) for communication between the chips and the board12through the connector14. The contacts24of the module10are coupled with the PCB12through the leads20on the connector14. The module10may comprise any number of chips22and contacts24on one or both sides (upper side26a, lower side26bas viewed inFIG. 2) of the module. In the example shown inFIG. 2, the 90 degree connector comprises two arms28extending outward for receiving the module10therebetween (FIGS. 1 and 2). The arms28may comprise locking members or tabs for securely retaining the memory module10within the connector14.

As can be seen in the exploded perspective shown inFIG. 3, the connector14comprises an opening (slot)34for receiving the module10. The connector opening34comprises contacts36aligned for mating with the contacts24on the module10at the connector to module interface and in communication with the pins20(FIG. 2) at the connector to PCB interface. The corrosion prevention cover16comprises a horizontal slot30for slidable insertion of the module10into the cover and removal of the module from the cover and vertical slots32on opposite end portions to slide over arms28of the connector14. As described below with respect toFIG. 4, flexible members (flaps) defining the slot30of the cover effectively form a seal with outer surfaces of the module (upper and lower external surfaces26a,26bof DIMM PCB) through resilient spring back of the flaps upon insertion of the module into the slot. The vertical slots32of the cover are also configured to minimize entry of contaminants into the enclosure created by the cover16.

It is to be understood that the terms upper, lower, top, bottom, and the like as used herein are relative terms based on orientation of the board or network device and are provided as examples and not to be interpreted as limiting the orientation, arrangement, or layout of components.

FIG. 4is a cross-sectional view of the module10inserted into the connector14with the cover16installed as shown inFIG. 1. The module10is inserted into the slot30of the cover16and contacts24on the module mate with the aligned contacts36in the connector opening34. The cover16includes a lower surface45in contact with the PCB12to create an enclosure48protecting the contacts (e.g., fingers24, leads36at the module to connector interface, contacts20at the connector to board interface).

The slot30of the cover16is defined by flexible resilient members (flaps)40a,40bthat are generally in contact with one another in their relaxed state (no module inserted as shown inFIG. 3) and upon receiving the memory module10(as shown inFIG. 4) resiliently bend towards outer surfaces of the module for sealing engagement (substantially sealing engagement) to effectively create a seal between the cover16and module10and prevent entry of contaminants into the enclosure48defined by the cover and PCB12.

The cover16may be formed from an elastically deformable material to engage with the module10and PCB12and create a seal at the cover to module interface and between the lower edge45of the cover16and the PCB (FIGS. 1 and 4). An adhesive material or sealant may be provided at the lower edge45to improve sealing between the cover16and PCB12or the seal may be formed from compression of the cover on the PCB when the module10is inserted into the cover. In one or more embodiments, the cover16is a one-piece element made of a molded elastomer material having suitable chemical resistance and material stability over a specified temperature range corresponding to operating conditions of the module10, board12, and surrounding components. The material may comprise, for example, rubber, silicone, or other suitable material.

FIG. 5illustrates a memory module (DIMM)50inserted vertically into a connector54(180 degrees relative to the PCB) and a corrosion prevention cover56placed over the connector54to enclose exposed contacts between the module50and connector54or connector and PCB. The vertical connector54may include locking members58at opposite ends to mate with notches57in the module50to securely hold the module in place. The locking members58may be released to remove the module50.

FIG. 6is an exploded view of the memory module50, connector54, and corrosion prevention cover56. The connector54is mounted on a PCB52. As previously noted, any number of components may be mounted on the PCB in any arrangement and one or more of the components may include a corrosion prevention cover (16,56) (FIGS. 1 and 6). The connector54includes an opening (slot) comprising contacts60for mating with contacts (fingers)64(only one shown for simplification) on the module50. As previously described, the module50may comprise any number of contacts (pins, fingers) on one or both sides of the module and any number of chips62. An upper surface of the cover56comprises a slot66for insertion or removal of the module50. Each end of the cover56includes openings72for receiving the locking members58of the connector54.

FIG. 7Ais a top perspective of the cover56andFIG. 7Bis a bottom perspective of the cover. The slot66is defined by mating flaps (flexible members)70a,70b, without the module inserted. In one or more embodiments, an outer surface of the flaps70a,70bare tapered to provide a sealing surface against the module50when inserted into the cover, described below with respect toFIG. 8. As shown inFIG. 7B, a lower surface75of the cover56comprises an edge margin for mating with the PCB52(FIG. 6) to substantially create a seal and define a generally moisture and particulate resistant enclosure (interior of cover)78to prevent corrosion of the enclosed contacts at the module and connector.

FIG. 8is a cross-sectional view of the connector54mounted on the PCB52with the memory module50inserted into the connector and cover56. As previously noted, in one or more embodiments, the upper outer surface of the flexible members70a,70bare tapered downward towards the slot66to provide improved sealing against the module50and prevent entry of contaminants into enclosure78defined by the cover56and PCB52(FIGS. 7A, 7B, and 8).

The contamination protection and corrosion prevention provided by the cover56may be further enhanced by combining with a removable or ‘strippable’ sealant material (seal coating, sealant, adhesive)90a,90bas shown inFIG. 9.FIG. 9is an enlarged cross-sectional view of the connector54mounted on the PCB52with the memory module50inserted into the connector and cover56. In this example, the sealant is applied as a secondary seal to further protect the contacts. In one or more embodiments, the sealant may be placed at least partially between an internal surface of the cover56and an external surface of the connector54. For example, as shown inFIG. 9, sealant90amay be applied along a lower edge of the connector54at a gap92defined between the connector and the cover56. In one example, a thin strip of adhesive is applied from a tube (e.g., small caulking gun) to an external surface of the connector54at the gap92between the PCB52and the DIMM connector54lower edge. The cover56may then be placed over the connector54with its lower internal edge margin positioned adjacent to (and mating with) the sealant90a.

In one example, the sealant90bmay be applied after the module50is inserted into the cover56and connector54to provide a strip of adhesive between outer surfaces of the module50and the flexible members70a,70bdefining the slot in the cover. The flaps70a,70bmay, for example, start in a vertical (open) position and then folded downward approximately ninety degrees after the adhesive is deposited at the DIMM socket and board interface. This would allow the adhesive to flow into open gaps and fix the flaps in the down position to protect the adhesive material.

It is to be understood that only sealant90amay be used, only sealant90bmay be used, or both the sealant90aand90bmay be used together.

In one or more embodiments, the sealant90a,90bmay comprise a fugitive adhesive or a strippable film.

The fugitive adhesive may have substantially the same adherent properties as an adhesive, however, it also possess the ability to be removed mechanically after application as a contiguous mass and not leave material residue. An example of such a fugitive adhesive is 3M™ Hot Melt Adhesive 3798LM. This particular material may be heated in an applicator “gun” and applied as a hot (e.g., approximately 250° F.) liquid. Once cooled, this adhesive retains an adherent “tacky” property, but it also can be mechanically peeled from surfaces if desired. One advantage of liquid application is that the adhesive will tend to flow readily into gaps, crevices, and voids, facilitating substantially complete filling or sealing of the target object. The cooled material may then serve as both an adhesive, effectively facilitating joining two or more parts, and as a barrier or sealant against moisture and fluids, particulate residue, and other airborne contaminants.

The strippable film may be a relatively thin (e.g., approximately 3-5 mils) polymeric film such as polyurethane, vinyl chlorides, or acrylic polymers mixed with other thickening and bonding agents. The film may be applied by brush or spray, for example. Once cured, the resultant film provides an environmental barrier that may be peeled or stripped away when needed.

FIGS. 10A and 10Billustrate an example of a module cover partially filled with the sealant. In this example, the module comprises a battery100inserted into a battery socket (connector)104and a cover106is installed over the module and connector. The connector104couples the battery100to a printed circuit board102.

FIG. 11is a cross-sectional perspective of the battery (module)100inserted into the connector104with the cover106installed. A lower external surface110comprises a battery contact that mates with a connector contact (e.g., finger). The cover106prevents entry of contaminants into the enclosure and prevents corrosion of the contacts. An internal surface of the cover106defines a circumferential gap112between the connector104and cover, and a horizontal gap114between an upper surface of the battery100and the cover.

As shown inFIGS. 12A and 12B, a sealant120may be placed within the cover106to fill the gaps112,114shown inFIG. 11and provide a secondary seal.FIG. 12Bshows an internal surface118of the cover106and illustrates how the cover106may be partially filled with the sealant120before the cover is positioned over the battery100and connector104(FIG. 12A). In one or more embodiments, the cover106may include an internal fill line marking to ensure proper adhesive volume. The cover106may also include one or more short vertical walls to increase bonding area between the cap and adhesive.

It is to be understood that the modules10,50,100and connectors14,54,104shown inFIGS. 1-12Aand described above are only examples and that the corrosion prevention cover16,56,106may be used to protect any contacts (e.g., copper leads, fingers) that cannot be conformal coated. For example, the corrosion prevention cover may be used with card edge connectors including, but not limited to memory cards (e.g., DIMM), expansion cards, power supplies, eUSBs, SIM cards, battery sockets, board-to-board connectors, or any other modules or connectors that comprise contacts that are susceptible to corrosion.

As shown inFIGS. 1, 5 and 11, and described above, the cover16,56,106encloses the contacts at the module to connector interface and connector to board interface to prevent corrosion of the contacts. The corrosion prevention cover16,56is preferably formed from a material that does not conduct heat well, therefore, heat generated by the components or board and transferred to the module or connector contacts will result in an increase in temperature within the cover enclosure. The cover provides a higher thermal resistance when installed over the connector, such that the heat conducted from the printed circuit board cannot be dissipated into an air stream (air flow over the components) as efficiently as in the absence of the cover. The cover therefore reduces (e.g., prevents, attenuates) dissipation of heat from an interior of the cover when the cover is installed over the connector. As temperature increases within the cover enclosure, the relative humidity decreases, thereby reducing corrosion rate at the contacts. Copper corrosion rate, for example, significantly increases with increasing relative humidity rates in the absence of other reactants, as shown in graphs130,132ofFIGS. 13A and 13Billustrating examples of corrosion rate in copper versus relative humidity. In environments in which reactive sulfide is present, the corrosion increases substantially as the sulfide content increases. With the corrosion prevention cover16,56,106in place, the local temperature of the air increases with lower relative humidity, thus reducing corrosion rate and increasing lifetime expectancy of the components.

In one example, the embodiments described herein may operate in the context of a data communications network including multiple network devices. The network may include any number of network devices in communication via any number of nodes (e.g., routers, switches, gateways, controllers, edge devices, access devices, aggregation devices, core nodes, intermediate nodes, or other network devices), which facilitate passage of data over one or more networks. The network devices may communicate over or be in communication with one or more networks, which may include any number or arrangement of network communications devices (e.g., switches, access points, routers, or other devices) operable to route (switch, forward) data communications.

FIG. 14illustrates an example of a network device140that may implement the embodiments described herein. In one or more embodiments, the network device140is a programmable machine that may be implemented in hardware, software, or any combination thereof. The network device140includes one or more processor142, memory144, network interface (port)146, and module (e.g., card edge connector, SIM card, battery, and the like)148.

Memory144may be a volatile memory or non-volatile storage, which stores various applications, operating systems, modules, and data for execution and use by the processor142. Memory144may include one or more of the modules148. The network device140may include any number of memory components, including for example, any number of memory modules (e.g., DIMMs) that are protected from corrosion using the corrosion prevention cover described herein.

Logic may be encoded in one or more tangible media for execution by the processor142. For example, the processor142may execute codes stored in a computer-readable medium such as memory144. The computer-readable medium may be, for example, electronic (e.g., RAM (random access memory), ROM (read-only memory), EPROM (erasable programmable read-only memory)), magnetic, optical (e.g., CD, DVD), electromagnetic, semiconductor technology, or any other suitable medium. In one example, the computer-readable medium comprises a non-transitory computer-readable medium. The network device140may include any number of processors142.

The network interface146may comprise any number of interfaces (line cards, ports) for receiving data or transmitting data to other devices.

It is to be understood that the network device140shown inFIG. 14and described above is only an example and that different configurations of network devices may be used. For example, the network device140may further include any suitable combination of hardware, software, algorithms, processors, devices, components, or elements operable to facilitate the capabilities described herein. Also, it is to be understood that the embodiments described herein are not limited to use in a network device and may be used in any type of electronic equipment with components that are susceptible to corrosion.

Although the method and apparatus have been described in accordance with the embodiments shown, one of ordinary skill in the art will readily recognize that there could be variations made without departing from the scope of the embodiments. Accordingly, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.