Patent Publication Number: US-7210955-B2

Title: Fully buffered press-fit DIMM connector

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to DIMM memory connector which cooperates with fully buffered requirements. 
   Card Connectors that connect a daughterboard such as a DIMM, to a motherboard have long been used in electronic devices such as personal computers. Such connectors typically include a connector housing having opposed contacts for interconnection to the DIMM module, are interconnected to the motherboard via contact tines, and have a latching mechanism which latches the DIMM to the card connector. However as the electronic speed continues to increase, so too, must the card connectors increase their performance. 
   Such is the case with the fully buffered requirements which requires a minimization of both contact skew as well as far/near end crosstalk. 
   As far as the contact skew is concerned, this requirement calls for a minimization of signal path difference in the contact system, and therefore requires substantially similar contact path lengths in the opposed contacts referred to above. With respect to the minimization of crosstalk, this requirement results in a contact configuration having no dead end stubs for contact rigidification, as is present in other DIMM designs. Such an example is shown in our U.S. Patent publication number U.S. 2005/0112933. 
   It is therefore an object to overcome these known shortcomings. 
   SUMMARY OF THE INVENTION 
   The objects have been accomplished by providing an electrical connector for a memory module, comprising a primary housing portion having a module receiving slot therein, with terminals opposing the slot for interconnection with a module. An alignment plate retains the terminals in place. The terminals comprise a printed circuit board contact extending downwardly from one end of an intermediate base portion, and an upper contact extending upwardly from the opposite end of the base portion. The base portions of the terminals are trapped between a lower face of the primary housing portion and an upper face of the alignment plate. 
   The upper contact may be defined by a flat blade portion with a contact portion extending from the flat blade portion. The contact portion may be defined by a central portion struck from the flat blade portion and extending outwardly from the flat blade portion and into the module receiving slot. The contact portion may be narrower than the base portion. The primary housing portion may include terminal receiving slots extending upwardly through a lower face. The terminal receiving slots may include rib-like walls adjacent to the module receiving slot, which form openings through which the contact portions extend. The rib-like walls may extend downwardly, and trap at least some of the terminal base portions between the alignment plate and the primary housing portion. 
   The lateral positions of the printed circuit board contacts may be staggered at longitudinal positions of the contacts. The primary housing portion may be elongate having the module receiving slot extending though an upper face of the housing, and extending longitudinally there along, and the housing further comprising first and second sidewalls extending along the length of the primary housing portion. At least some of the terminals may have the printed circuit board contact adjacent the first sidewall, with the base portion extending towards the module receiving slot, with the upper contacts extending upwardly adjacent to the module receiving slot; and some of the terminals have the printed circuit board contact adjacent the module receiving slot, with the base portions extending towards the second sidewall, with the upper contacts extending upwardly and redirected to a position adjacent to the module receiving slot. 
   At least some of the terminals may also have the printed circuit board contacts adjacent the second sidewall, with the base portions extending towards the module receiving slot, with the upper contacts extending upwardly adjacent to the module receiving slot; and some of the terminals may have the printed circuit board contact adjacent the module receiving slot, with the base portion extending towards the first sidewall, and with the upper contacts extending upwardly and redirected to a position adjacent to the module receiving slot. 
   The signal length of all of the terminals may be substantially equal in length. 
   In another embodiment of the invention, a electrical connector for a memory module, comprises an elongate primary housing portion having a module receiving slot extending though an upper face of the housing, and extending longitudinally there along. The housing further comprises first and second sidewalls extending along the length of the primary housing portion. An array of electrical terminals oppose the slot for interconnection with a memory module. An alignment plate retains the terminals in place. The array of electrical terminals generally comprise individual terminals with each comprising a printed circuit board contact extending downwardly from one end of an intermediate base portion, and an upper contact extending upwardly from the opposite end of the base portion, and the base portions of the terminals being trapped between a lower face of the primary housing portion and an upper face of the alignment plate. The array of electrical terminals comprises a first subset of terminals having first printed circuit board contacts adjacent the first sidewall, with first base portions extending towards the module receiving slot, and with the first upper contacts extending upwardly adjacent to the module receiving slot. A second subset of terminals has second printed circuit board contacts adjacent the module receiving slot, with second base portions extending towards the second sidewall, and with second upper contacts extending upwardly and redirected to a position adjacent to the module receiving slot. 
   The array of terminals may also include a third subset of terminals having third printed circuit board contacts adjacent the second sidewall, with the third base portions extending towards the module receiving slot, with third upper contacts extending upwardly adjacent to the module receiving slot; and a fourth subset of electrical terminals having fourth printed circuit board contacts adjacent the module receiving slot, with fourth base portions extending towards the first sidewall, and with fourth upper contacts extending upwardly and redirected to a position adjacent to the module receiving slot. 
   The primary housing portion may include terminal receiving slots extending upwardly through a lower face. The terminal receiving slots include rib-like walls adjacent to the module receiving slot, which form openings through which the contact portions extend. The rib-like walls may extend downwardly, to form a shoulder which traps at least some of the terminal base portions between the alignment plate and the primary housing portion. The shoulder may trap the second and fourth base portions. The contact portions may be defined by a central portion struck from the flat blade portion and extending outwardly from the flat blade portion and into the module receiving slot. The contact portion may be narrower than the base portion. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of the memory module connector of the present invention; 
       FIG. 2  is a partial end view of the connectors shown in  FIG. 1 ; 
       FIG. 3  shows a portion of the connector of  FIG. 1  with the alignment plate exploded away from the memory connector housing; 
       FIG. 4  shows the underside perspective of the connector housing as shown in  FIG. 3 ; 
       FIG. 5  shows a cross sectional view through lines  5 — 5  of  FIG. 2 ; 
       FIG. 6  shows an enlarged perspective view of the area denoted in  FIG. 5 ; 
       FIG. 7  shows an enlarged view of a portion of the alignment plate; 
       FIG. 8  shows a perspective view of one of the opposed contact portions; 
       FIG. 9  shows a perspective view of the corresponding opposed terminal; 
       FIG. 10  is similar to  FIG. 6  showing the terminals and their respective positions; and 
       FIGS. 11–14  are cross sectional views taken along various longitudinal positions to show the cooperation of the electrical terminals in multiple assembled configurations, together with the cooperation of the alignment plate. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   With reference first to  FIG. 1 , the overall connector assembly is shown generally at  2 , and includes a two piece housing comprised of a primary housing portion  4  and an alignment plate  6 . The combination of the primary housing portion  4  and alignment plate  6  retains an array of electric terminals  10  therein. The connector assembly  2  further comprises latch members  11  at opposite ends to retain and extract a DIMM module (not shown). 
   With respect now to  FIGS. 2 through 4 , it should be noted that primary housing portion  4  is generally elongate, having first and second sidewalls  12 ,  13  and further includes a module receiving slot  14  therein. The slot  14  extends into an upper face  16  of housing portion  4 . It should also be noted from  FIGS. 3 and 4 , that alignment plate  6  is removable from a lower face  18  of housing portion  4 . With reference now to  FIGS. 5 and 6 , primary housing portion  4  will be described in greater detail. 
   As best shown in  FIG. 5 , housing portion  4  includes a plurality of terminal receiving slots  20  extending from lower face  18  to upper face  16 . As shown in  FIG. 6 , slots  20  generally include opposing faces  22  which form the side walls for terminal slots  20 . Terminal receiving openings  24  are formed between continuous wall  26  and contoured walls  28  where walls  28  are integrally formed on opposing faces  22 . Continuous wall  26  is formed with an end face  30  which opposes the end face  32  of contoured wall  28 . Contoured wall  28  further includes a relief area  34  to allow passage of a terminal into the slots upon insertion thereof. 
   Housing portion  4  further includes an elongate rib-like wall  36  which extends from a position adjacent upper face  16  to a position coplanar with lower face  18  to form a clamping surface  38 . Rib-like wall  36  further includes a sidewall portion  40  and a rearwardly facing wall portion  42 . Finally, rib-like wall  36  includes interference wall portion  44  as will also be described herein in greater detail. 
   With respect now to  FIG. 7 , alignment plate  6  is shown having an inner face  46  and an outer face  48 . Two elongate side by side contoured wells  50  are formed on the inner face  46  for aligning and retaining the array of terminals  10  as shown herein. It should also be appreciated that the contoured walls form a repeating pattern and in the embodiment shown in  FIG. 7 , has a repeating pattern of four configurations that is, positions A–D. It should be understood that neither the repeating pattern, nor the number of configurations, is necessary to carry out the invention. 
   For example, at longitudinal position A, the alignment plate  6  includes surfaces  52  which lead into openings  54 , where the openings  54  are on the near side of the surfaces  52  as shown in  FIG. 7 . At longitudinal position B, the alignment plate  6  includes surfaces  56  leading into openings  58  on the far side of surfaces  56  as viewed in  FIG. 7 . At longitudinal position C, surfaces  60  are similar to surfaces  52  and further include an opening  62  similar to opening  54 , however longitudinal position C includes a retaining post  70  in combination therewith. Finally at longitudinal position D, the alignment plate includes surfaces  64  in combination with openings  66 , and further in combination with retaining post  72 . 
   As mentioned above, connector assembly  2  includes an array of electrical terminals  10 . The array of electric terminals is comprised of individual terminals  80 ,  100  as shown in  FIGS. 8 and 9  and as more particularly described below. 
   As shown in  FIGS. 8 and 9 , terminals  80 ,  100  include printed circuit board tine portions  82 ,  102  where each tine portion includes a printed circuit board contact  84 ,  104 . As shown in the embodiments of  FIGS. 8 and 9  the contacts  84 ,  104  are shown as “eye of the needle” type press fit contacts. Terminals  80 ,  100  further include a flattened base portion  86 ,  106 ; a transition portion  88 ,  108 ; retention portions  89 ,  109  and an inwardly directed portion  90 ,  110  (inwardly in relation to the module receiving slot). Upper contacts  91 ,  111  comprise flat blade portions  92 ,  112  which extend upwardly from the corresponding transition portions  90 ,  110  to define the upper contacts with inwardly directed contact portions at  94 ,  114 . As shown, contact portions  94 ,  114  are defined by central portions stamped from the blade portions  92 ,  112 . It should also be understood that the terminals  80 ,  100 , even though differently configured, have substantially equal lengths, from the standpoint of their respective signal path lengths. 
   With respect now to  FIGS. 10 to 13 , the cooperation of the primary housing portion  4 , alignment plate  6  and terminals  80 ,  100  will be described in greater detail. 
   With respect first to  FIG. 10 , two terminals  80 ,  100  are shown trapped between alignment plate  6  and housing portion  4 . This position corresponds with longitudinal position D shown in  FIG. 7  (assuming a cross section is taken with a view looking to the left in  FIG. 7 ). In particular, terminal  80  is shown with the flattened base portion  86  positioned against surface  64  and trapped beneath clamping surface  38 . Meanwhile tine portion  82  extends through opening  66  of alignment plate  6  and contact portion  94  protrudes between sidewall portions  40 . It should be noted from  FIG. 10 , that the contact portion  94  is narrower than the base portion  86 . This allows the terminal  80  to be slidably received in the slot  20 , while at the same time, allows clamping surface  38  to abut the base portion  86 . Finally, it should be appreciated that retention portion  88  is press fit between end faces  30 ,  32 . 
   On the opposite side of the connector, terminal  100  is positioned with its flattened base portion  106  being positioned between surface  64  and lower face  18  of primary housing portion  4 . Retaining post  72  is also shown trapped in the terminal receiving slot  20  between interference walls  44 . It should be noted that the retention of the terminal  100  is slightly different. As base portion  106  extends towards side wall  13 , away from contact portion  104 , base portion  106  is simply retained between lower face  18  and surface  64 . 
   In a like manner,  FIG. 11  shows a cross sectional view through the combination of the primary housing portion, terminals  80 ,  100 , and alignment plate  6 , at a position corresponding to longitudinal position A (again assuming a cross section is taken with a view looking to the left in  FIG. 7 ). This cross-section shows terminals  80 ,  100  trapped against corresponding surfaces  52  as described above in  FIG. 10 .  FIG. 11  also shows a first of four subsets of terminal configurations. As shown, a first subset includes a printed circuit board contact portion  104  being positioned adjacent to first side wall  12 , with base portion  106  extending towards module receiving slot  14 . Upper contact  111  extends from the opposite end of base portion  106 , from contact portion  104 , and extends upwardly and is redirected towards the module receiving slot  14 .  FIG. 11  also shows a second subset of terminal configuration where printed circuit board contact  84  is adjacent to the module receiving slot  14 , and base portion  86  extends towards second sidewall  13 . Upper contact  91  extends from base portion  86 , and is redirected to a position adjacent the module receiving slot  14 . 
     FIG. 12  shows a cross sectional view similar to that of  FIG. 11 , at a position corresponding to longitudinal position B (assuming a cross section is taken with a view looking to the left in  FIG. 7 ) with the terminals  80 ,  100  trapped against corresponding surfaces  56 .  FIG. 12  also shows a third of four subsets of terminal configurations. In this subset, printed circuit board contacts  104  are adjacent to second sidewall  13 , and base portion  106  extends towards the module receiving slot  14 . Upper contact  111  is thereafter redirected to a position adjacent module receiving slot  14 . 
   Finally,  FIG. 12  also shows the fourth subset of terminal configurations and in this configuration, contact  84  is adjacent module receiving slot  14  and base portion  86  extends towards first sidewall  12 . Upper contact  91  is thereafter redirected to a position adjacent module receiving slot  14 . 
     FIG. 13  shows a cross sectional view similar to that of  FIG. 11 , at a position corresponding to longitudinal position C of  FIG. 7 , (assuming a cross section is taken with a view looking to the left in  FIG. 7 ) with terminals  80 ,  100  trapped against the corresponding surfaces  60 . Finally,  FIG. 14  shows a cross sectional view similar to that of  FIG. 11 , at a position corresponding to longitudinal position D of  FIG. 7 , (assuming a cross section is taken with a view looking to the left in  FIG. 7 ) showing terminals  80  and  100  trapped against corresponding surface  64 , as was described above with respect to  FIG. 10 . 
   It should be appreciated from the above description that when terminal  100  is used, a flattened portion  106  is trapped between the lower face of the primary housing portion  4  lower face  18  and its corresponding alignment plate surface  52 ,  56 ,  60  and  64 ; and when terminal  80  is used it is trapped beneath clamping surface  38  and its corresponding surface  52 ,  56 ,  60  and  64 . It should also be appreciated that this configuration allows the terminals  80 ,  100  to be assembled from the lower face  18  of the primary housing portion  4 , that the terminals are held in place by a combination of their retention portions  89 ,  109  in combination with the end faces  30 ,  32 ; and in further combination with the alignment plate  6 . Furthermore, it should be understood that the contacts are press-fit contacts and that the terminals have positive back stops in the housing, that is surfaces  18 ,  38 , for rigidification of the terminals  80 ,  100 , when the connector assembly  2  is press fit into a board. 
   With respect to the electrical characteristics, it should be appreciated from  FIGS. 8 and 9  that the terminals  80 ,  100 , while slightly different in configuration, have an overall signal length substantially identical in length. Moreover, as viewed in  FIGS. 8 and 9 , the terminals  80 ,  100  do not include any stubbed portions, or discontinuous portions which could effect the cross talk characteristics. Thus, the present connector meets the fully buffered requirements.