Patent Publication Number: US-2018054015-A1

Title: Electrical connection including a lubricant

Description:
BACKGROUND 
     The invention relates to stationary electrical connections and particularly to lubricated stationary connections that are subject to extreme operating conditions. 
     One of the challenges in designing systems used in harsh environments is maintaining quality electrical connections on high speed busses. Vibration and corrosion are primary contributors which can lead to connection failures. In early stages these failures may appear as intermittent communication or undetected devices, requiring removal and reinstallation before normal operation is restored. In more advanced stages, these connections may become worn to the extent that a reseat will no longer resolve the issue and hardware replacement is necessary. 
     With the growing size and weight of graphics or other auxiliary cards, PCI express connections have been one of the most susceptible connectors to mechanical failure. Significant time has been spent designing and validating mechanical retention mechanisms to support and retain these cards. However, when these large cards are used in a high vibration environments mechanical wear can still occur. 
     SUMMARY 
     In one construction, an electrical system includes a motherboard including a receptacle that provides a first plurality of electrical connectors and an auxiliary card including an extension defining a second plurality of electrical connectors. The extension is fixedly coupled to the receptacle to substantially fix the position of the auxiliary card with respect to the mother board and to electrically connect the first plurality of electrical connections and the second plurality of electrical connections. An electrically-conductive lubricant is disposed between the extension and the receptacle. 
     In another construction, an electrical system includes a motherboard including a receptacle that includes a slot having a first width, a first plurality of electrical connections disposed within the slot and providing a plurality of electrical connectors between the receptacle and the motherboard, and an auxiliary card including an extension having a second width that is larger than the first width. A second plurality of electrical connectors is coupled to the extension and provides a plurality of electrical connections between the extension and the auxiliary card. The extension is insertable into the receptacle to define an interference fit therebetween to substantially fix the position of the auxiliary card with respect to the motherboard and to electrically connect the auxiliary card and the motherboard. An electrically-conductive lubricant is disposed between the extension and the receptacle. 
     In yet another construction, the invention provides a method of reducing wear between an auxiliary card and a motherboard. The method includes providing a mother board having a receptacle that defines a slot having a first width, providing an auxiliary card including an extension that defines a second width that is greater than the first width, and applying a lubricant to one of the extension and the slot. The method further includes inserting the extension into the slot to define an interference fit therebetween to substantially fix the position of the auxiliary card with respect to the motherboard and to electrically connect the auxiliary card and the motherboard. 
     Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top view of a motherboard including various connectors including several PCI Express connectors; 
         FIG. 2  is an exploded perspective view of an auxiliary card and a receptacle for receiving the card; 
         FIG. 3  is an enlarged view of a connector of the card of  FIG. 2  after operation without a lubricant; and 
         FIG. 4  is an enlarged view of a connector of the card of  FIG. 2  after operation with a lubricant. 
     
    
    
     Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings. 
     DETAILED DESCRIPTION 
       FIG. 1  illustrates a mother board or main board  10  that includes various electrical components  15  (e.g., memory, central processing unit, resistors, capacitors, etc.) and several Peripheral Component Interconnect (PCI)  20  and Peripheral Component Interconnect Express (PCI Express)  25  receptacles arranged to receive auxiliary cards  30  that connect using the PCI or PCI Express standard. As one of ordinary skill in the art will realize, other connector types or standards are possible and could be used with the present invention. 
     As illustrated in  FIG. 2 , the PCI Express receptacle  25  includes a slot  35  and a plurality of electrical connectors  40  disposed in the slot  35 . The space between electrical connectors  40  across the slot  35  defines a slot width  45 . The auxiliary card  30  includes an extension  50  that supports a plurality of electrical connectors  55  permanently affixed to the exterior of the extension  50 . The electrical connectors  55  are spaced apart from one another across the extension  50  to define a second width  60 . In preferred constructions the second width  60  is greater than the first width  45  to define an interference fit between the auxiliary card  30  and the receptacle  25 . Thus, in order to install the auxiliary card  30 , the user must apply sufficient force to open the receptacle  25  to slide the extension  50  into the slot  35  of the receptacle. The stiffness and rigidity of the receptacle  25  squeezes the extension  50  to firmly hold the card  30  in place and to provide a good electrical connection between the connectors  40  within the slot  35  and the connectors  55  on the exterior of the extension  50 . 
     A lubricant  65 , illustrated in  FIG. 2  is placed on the connectors  55  of the extension  50  and/or into the slot  35  of the receptacle  25 . The lubricant  65  assists in the installation of the auxiliary card  30  and reduces the likelihood of damage to the connectors  40 ,  55  during the installation process. In a preferred construction, the lubricant  65  includes a synthetic hydrocarbon grease with more preferred constructions including silica as a thickening agent to assure that the lubricant  65  has the proper consistency for use in the intended operating environment. A preferred lubricant  65  has an operating temperature range between about −40 degrees centigrade and 135 degrees centigrade and a dielectric strength of about 115 Volts/mil (4530 Volts/mm). One suitable lubricant  65  is sold under the name NYOGEL. 
     A test was defined to evaluate the impact of the lubricant  65  on a typical PCIe connection. A MIL-STD-810F test was selected to reproduce an environment containing high levels of vibration. The vibration profile parameters were selected from MIL-STD-810F 514.5C-1 and were executed for a duration of four hours. A baseline test was performed using a system without lubrication applied to the connectors  40 ,  55 . After the test was completed the system was powered on and the PCIe device was not detected by the system. After powering the unit off and reseating the card  30 , it was able to be detected. The card  30  was then removed from the system, cleaned with electrical contact cleaner and eraser. The contacts  55  used for this test are shown in  FIG. 3 . The contacts  55  have pitting at the highest compression point  57  of the contacts  55  as well as longer, shallower, wear lines over the length of the contact  55 . 
     A second test was then completed using identical hardware. Prior to installing the PCIe card  30  in the second system the lubricant  65  was applied to the contacts  55  on the card  30 . The test was then completed according to the method described above. Upon test completion the unit was powered on and the PCIe card  30  was detected and functioned properly. The card  30  was then removed and the contacts  55  were cleaned with contact cleaner and an eraser. The contacts  55  were pitted similarly to the first test card  30 , however there were no visible wear lines on the contacts  55 . The image of the contacts  55  are shown in  FIG. 4 . 
     To prevent adverse material reactions it is critical to confirm that the lubricant  65  is compatible with the materials used in the contacts  40 ,  55  and nearby components  15 . The following table identifies the common materials used in systems and their compatibility with the selected lubricant  65 . 
     
       
         
           
               
               
               
               
             
               
                   
               
               
                 Component(s) 
                 Material 
                 Material Type 
                 Compatibility 
               
               
                   
               
             
            
               
                 PCB&#39;s 
                 AIM SN100C, Lead-free solder material 
                 metal 
                 yes 
               
               
                 Memory 
                 Aluminum 
                 metal 
                 yes 
               
               
                 Memory 
                 Borophosphosilicate glass (BPSG) 
                 glass 
                 yes 
               
               
                 PCB&#39;s 
                 Brass 
                 metal 
                 yes 
               
               
                 PCB&#39;s 
                 Ceramic 
                 glass 
                 yes 
               
               
                 PCB&#39;s 
                 Clear Chromate coating 
                 metal 
                 yes 
               
               
                 PCB&#39;s 
                 Copper 
                 metal 
                 yes 
               
               
                 PCB&#39;s 
                 FR4, board material in PCB&#39;s 
                 multiple 
                 yes 
               
               
                 Memory 
                 Glass (Silicon Dioxide) 
                 glass 
                 yes 
               
               
                 Memory, PCB&#39;s 
                 Gold 
                 metal 
                 yes 
               
               
                 Memory 
                 Lead 
                 metal 
                 yes 
               
               
                 PCB&#39;s 
                 Nickel 
                 metal 
                 yes 
               
               
                 PCB Connectors 
                 NY6T 
                 plastic 
                 yes 
               
               
                 PCB Connectors 
                 Nylon 46 
                 plastic 
                 yes 
               
               
                 PCB Connectors 
                 Nylon 66 
                 plastic 
                 yes 
               
               
                 PCB Connectors 
                 Nylon 67 
                 plastic 
                 yes 
               
               
                 PCB Connectors 
                 Nylon 9T 
                 plastic 
                 yes 
               
               
                 PCB&#39;s 
                 PA66 (Glass) 
                 glass 
                 yes 
               
               
                 PCB&#39;s 
                 Phosphor Bronze 
                 metal 
                 yes 
               
               
                 Memory 
                 Silicon 
                 glass 
                 yes 
               
               
                 PCB&#39;s 
                 Silver 
                 metal 
                 yes 
               
               
                 PCB&#39;s 
                 Stainless Steel 
                 metal 
                 yes 
               
               
                 PCB Brackets, Chassis Parts 
                 Steel 
                 metal 
                 yes 
               
               
                 Memory, PCB&#39;s 
                 Tin 
                 metal 
                 yes 
               
               
                 PCB&#39;s 
                 Woven Glass 
                 glass 
                 yes 
               
               
                 PCB Brackets, Chassis Parts 
                 Zinc 
                 metal 
                 yes 
               
               
                   
               
            
           
         
       
     
     Testing to determine the change on several common parts was then conducted to confirm chemical compatibility findings. The test involved applying the lubricant  65  to several parts while leaving other areas uncoated. The parts were then placed in a thermal chamber at 70 degrees C. for 336 hours. Once removed the parts we placed at room temperature and allowed to cool. The lubricated surfaces were then cleaned with a towel. Multiple durometer measurements were performed on each part. Both lubricated and unlubricated surfaces were measured. The following table shows the impact of the parts: 
     
       
         
           
               
               
               
               
               
             
               
                   
               
               
                   
                 Durometer 
                 Durometer 
                 Durometer 
                   
               
               
                 Description 
                 (Untested) 
                 (Tested) 
                 (Tested w/ Nyogel) 
                 % Diff 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 Overmolding Sleeve—Trexprene Black 
                 N/A 
                 73.75 
                 69.75 
                 −5%   
               
               
                 SATA cable—Insulation 
                 N/A 
                 97 
                 99 
                 2% 
               
               
                 SATA cable—Connector 
                 N/A 
                 88.25 
                 93 
                 5% 
               
               
                 Serial cable—Insulation 
                 N/A 
                 94.25 
                 93.25 
                 −1%   
               
               
                 Serial cable—Connector 
                 N/A 
                 79.5 
                 76.5 
                 −4%   
               
               
                 Dual USB Front panel cable—Connector 
                 N/A 
                 59.5 
                 60.5 
                 2% 
               
               
                 Dual USB Front panel cable—Insulation 
                 N/A 
                 88 
                 85.5 
                 −3%   
               
               
                 Floppy to SATA Power cable—Insulation 
                 N/A 
                 87.5 
                 86 
                 −2%   
               
               
                 Capacitor (C649) 
                 101.5 
                 N/A 
                 101.5 
                 0% 
               
               
                 CMOS Battery 
                 95.5 
                 N/A 
                 96 
                 1% 
               
               
                 RAM DDR3 SODIMM Socket (SODIMM0) 
                 81 
                 N/A 
                 79.75 
                 −2%   
               
               
                 PCI Express 1.0a ×1 Housing (PCIe ×1) 
                 50.5 
                 N/A 
                 53 
                 5% 
               
               
                 PCI Express Half-Mini Card Slot (PCIe HMC) 
                 75.25 
                 N/A 
                 71.25 
                 −5%   
               
               
                 3-Wire System Fan Header 
                 67.5 
                 N/A 
                 68 
                 1% 
               
               
                 Audio Line In Connector (Pink) 
                 85.75 
                 N/A 
                 87.5 
                 2% 
               
               
                 Audio Line Out Connector (Green) 
                 86 
                 N/A 
                 84.75 
                 −1%   
               
               
                 LVDS Connector 
                 92.25 
                 N/A 
                 93.5 
                 1% 
               
               
                 Internal Power Connector, 2 Pin 
                 96.5 
                 N/A 
                 92.5 
                 −4%   
               
               
                 Cap. Package (C353/C354/C373/C374) 
                 97.5 
                 N/A 
                 97.25 
                 0% 
               
               
                 VGA Connector 
                 60 
                 N/A 
                 58.5 
                 −3%   
               
               
                 CG82NM10 SLGXX Chip (IC VGA) 
                 100 
                 N/A 
                 100 
                 0% 
               
               
                 SATA Power Connector 
                 87.5 
                 N/A 
                 94.5 
                 8% 
               
               
                 SATA Data Connector (SATA0) 
                 84 
                 N/A 
                 85.25 
                 1% 
               
               
                 SATA Data Connector (SATA1) 
                 93.75 
                 N/A 
                 94.75 
                 1% 
               
               
                 Chip Package (L28) 
                 96.5 
                 N/A 
                 97.5 
                 1% 
               
               
                 PCB 
                 94.5 
                 94.5 
                 95.25 
                 1% 
               
               
                 PCI Video Card Slot 
                 N/A 
                 89.5 
                 89.75 
                 0% 
               
               
                   
               
            
           
         
       
     
     Durometer (untested) indicates a measurement taken on a part that was not subjected to the prolonged heat. Durometer (tested) indicates that the part was subjected to the heat prior to making the durometer measurement. 
     As the table above shows, all parts tested experienced less than a 10 percent change in durometer readings. This small amount of change is further minimized by the additional mechanical retention that is used to support connections with significant mass such as add in cards  30  or large cables. 
     By applying lubrication  65  to the contacts  40 ,  55 , friction is minimized and contact wear and damage (e.g., installation damage, fretting, oxidation, etc.) is reduced resulting in a significant reliability improvement. 
     Various features and advantages of the invention are set forth in the following claims.