Patent Publication Number: US-6336823-B2

Title: Electrical connector having female contact preload section

Description:
This is a division of application No. 09/444,956 filed Nov. 22, 1999 now U.S. Pat. No. 6,264,490. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to electrical connectors and, more particularly, to a socket connector for receiving terminals from a mating component. 
     2. Brief Description of Earlier Developments 
     U.S. Pat. No. 5,044,973 discloses an electrical connector for receiving male contacts of an electrical component. The connector has preload pins to preload arms of electrical contacts of the connector in an open position. U.S. Pat. No. 5,704,800 discloses an inner wall projection of a housing used to preload a contact arm. 
     One of the problems in the design of high pin count connectors is the amount of force that is required to mate the connectors. A minimum amount of normal force (approx. 30 grams per contact) is required for a reliable contact interface for gold plated contacts. Usually most applications limit the total mating forces to less than 10 lb for repetitive operations. This means that there is finite limit, based on the sliding friction alone, to the maximum pin count for a standard connector; around 450 contacts at the minimum normal force. However, this does not take into account the increased friction at the initial part of the contact mating cycle; when the contact is first opened. This additional force approximately doubles the initial forces which further limits the pin count. In other words, even less than 450 contacts will exceed the mating force limit. 
     Fortunately, there have been developed a number of techniques to allow large numbers of pins to be mated. One of these methods is ZIF, which means that either small or almost no “Z-axis” forces are required to mate the connector. This typically is done in two basic ways. In one case the contacts are “normally open” and are cammed into contact position using an external plate. In other cases the contacts are “normally closed” and they are temporarily cammed open and then closed after insertion of a pin. Both of these designs share the problem of having sufficient contact “wipe” to remove films and contaminants. Another method is to use some form of mechanical advantage to drive the pin assembly laterally into a contact, eliminating “Z-axis” forces and having sufficient contact wipe to maintain reliability. Typically, the mechanical advantage of a lever driving the pin assembly can reduce the mating forces to acceptable levels. However, historically these mechanisms have not been easy to design and implement. The designs typically have had problems with flexing and bowing resulting in hystersis in the connector assembly. Recent requirements of higher pin counts (600+pins) coupled with changes of density from 0.100 centers to 0.050 centers, in addition to requirements for lower mating heights, make these problems even more difficult to solve. 
     SUMMARY OF THE INVENTION 
     In accordance with one embodiment of the present invention, an electrical connector is provided comprising electrical contacts and a housing. The electrical contacts are connected to the housing. The housing comprises a first housing member and a second housing member movably connected to the first housing member. The second housing member comprises holes for allowing terminals of an electrical component to be inserted into the housing. The housing also comprises contact preload projections. The contact preload projections engage the electrical contacts to preload the electrical contacts and, when the terminals are inserted into the holes, the contact preload projections contact the terminals to form a strain relief support for the terminals. 
     In accordance with another embodiment of the present invention, an electrical connector and electrical component assembly is provided comprising an electrical component comprising male contacts; and an electrical connector for connecting the electrical component to another electrical component. The electrical connector comprises electrical contacts and a housing. The housing comprises first and second housing members movably connected relative to each other. The electrical contacts are connected to the first housing member. The second housing member comprises contact preload sections contacting the electrical contacts and apertures having the male contacts therein. The contact preload sections having a width less than a width of the male contacts. The contact arms of the electrical contacts are deflected outward by the male contacts as the electrical contacts move off of the contact preload sections onto the male contacts. 
     In accordance with another embodiment of the present invention, an electrical connector is provided comprising electrical contacts and a housing. The housing comprises first and second housing members movably connected to each other. The electrical contacts are mounted to the first housing member. The second housing member comprising a first section and contact preload sections extending from the first section. The second housing member has apertures through the first section and into the contact preload sections. Side openings are provided at the contact preload sections into the apertures. 
     In accordance with one method of the present invention, a method of connecting male contacts to electrical contacts in an electrical connector is provided comprising steps of inserting the male contacts in a first direction into holes in a housing of the electrical connector; and moving the male contacts in a second different direction, with a portion of the housing, into contact with electrical contacts of the electrical connector. The electrical contacts are preloaded against preload sections of the portion of the housing, the preload sections having a width smaller than a width of the male contacts and, during the step of moving, the male contacts deflect contact arms of the electrical contacts outward as the electrical contacts move off of the preload sections onto the male contacts. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing aspects and other features of the present invention are explained in the following description, taken in connection with the accompanying drawings, wherein: 
     FIG. 1 is a perspective view of an electrical connector incorporating features of the present invention; 
     FIG. 2A is an enlarged exploded partial cross-sectional view of the connector shown in FIG. 1; 
     FIG. 2B is an exploded partial cross-sectional view of the connector shown in FIG. 2A taken along line  2 B— 2 B; 
     FIG. 3A is an enlarged partial cross-sectional view of the connector shown in FIG. 1 at a first position and connecting two electrical components to each other; 
     FIG. 3B is a partial cross-sectional view of the connector shown in FIG. 3A taken along line  3 B— 3 B; 
     FIG. 3C is a partial cross-sectional view of two of the contacts and the preload section shown in FIG. 3A; 
     FIG. 4A is an enlarged partial cross-sectional view of the connector shown in FIG. 1 at a second position and connecting two electrical components to each other; 
     FIG. 4B is a partial cross-sectional view of the connector shown in FIG. 4A taken along line  4 B— 4 B; and 
     FIG. 4C is a partial cross-sectional view of two of the contacts and the preload section shown in FIG.  4 A. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1, there is shown a perspective view of an electrical connector  10 , specifically a socket connector, incorporating features of the present invention. Although the present invention will be described with reference to the single embodiment shown in the drawings, it should be understood that the present invention can be embodied in many alternate forms of embodiments. In addition, any suitable size, shape or type of elements or materials could be used. 
     The connector  10  generally comprises a housing  12 , electrical contacts  14  (see FIGS.  2 A and  2 B), and a movement or actuation mechanism  16 . The connector  10  is generally intended to connect an electrical component, such as a computer chip, pin grid array (PGA) component or multi-chip module to another electrical component, such as a printed circuit board. Similar connectors are disclosed in U.S. Pat. Nos. 5,704,800; 5,649,836; and 5,044,973 which are hereby incorporated by reference in their entireties. However, features of the connector  10  could be used to connect any suitable types of electrical or electronic components. Referring also to FIGS. 2A and 2B, enlarged, partial exploded views of the connector  10  are shown. The housing  12  generally comprises a relatively stationary base  18  and a movable cover  20 . The cover  20  is movably mounted to the base and can move in the direction of arrow A in FIG. 1 between a first position shown in FIG. 1 and a second position. The movement mechanism  16  can comprise a cam lever  22 . The cam lever  22  can be moved by a user in direction B from the position shown in FIG. 1 to a latched position between latches  24 . The cam lever  22  has a camming surface  26  that cooperates with portions of the cover  20  and base  18  to move the cover relative to the base as the cam lever is moved. However, in alternate embodiments any suitable type of movement mechanism can be provided for moving the cover relative to the base. In another alternate embodiment, the movement mechanism could be adapted to move a third housing member (not shown) located between the base and cover; the third housing member having the contact preload sections and/or male contact strain relief described below. 
     The base  18  is preferably comprised of a dielectric material, such as a molded plastic or polymer material. However, any suitable material(s) could be used. The base  18  has a bottom side  28 , a top side  30 , and contact receiving areas  32  between the two sides. The bottom side  28  is adapted to be located adjacent an electrical component, such as a printed circuit board. The contacts  14  are fixedly connected to the base  18  in the areas  32 . The contacts  14  are comprised of electrically conductive material, such as stamped and formed from a sheet of copper alloy. However, any suitable contacts could be provided and any suitable process(es) could be used to form the contacts. In this embodiment the contacts  14  each comprise a bottom end  34 , a middle section  36 , and a top end  38 . The bottom ends  34  of the contacts  14  are located at the bottom side  28 . The bottom ends  34  could have any suitable shape, such as a through-hole mounting solder tail, or a surface mounting solder tail, or could use a solder ball for surface mounting. However, any suitable contact end at the bottom of the contacts could be provided. The middle section  36  connects the contact  14  to the base  18  in the receiving area  32 . The top end  38  generally comprises two opposing cantilevered contact arms  40 . However, in an alternate embodiment, any suitable shape of the to p ends  38  could be provided, such as only one cantilevered contact arm. In this embodiment the two contact arms  40  form a space or receiving area  42  between the two arms. In addition, the arms  40  have contact areas  44  located directly opposite each other. The contacts  14  are aligned in rows with their receiving areas  42  aligned in each row parallel to direction A. 
     The cover  20  is preferably comprised of dielectric material, such as molded plastic or polymer material. However, any suitable material(s) and process(es) for forming the cover could be used. The cover  20  includes a top section  46  and a plurality of contact preload sections  48 . The top section  46  has a top side  50 , a bottom side  52 , and side platforms  54 . The bottom surfaces  56  of the side platforms  54  could be located on the top surfaces  58  of the side platforms  60  of the base  18 . However, any suitable movable engagement between the cover  20  and base  18  could be provided. The contact preload sections  48  extend or project downward from the bottom side  52 . The cover  20  includes lead-in holes or apertures  62 . The holes  62  extend through the top section  46  from the top side  50  and into the contact preload sections  48 . In this embodiment the preload sections  48  each form individual preload portions  48   a  which preferably flank the contacts  14 . The portions  48   a  are generally separated from each other by the holes  62  and openings  66 , but with a connecting portion  49 . However, in an alternate embodiment the portions  49  need not be provided, such as when the portions  48   a  are not directly connected to each other. The contact preload sections  48  each generally comprise a wedge shaped bottom tip  64 , a substantially uniform width, a general elongate length and a general elongate height. In addition, the contact preload sections  48  also include lateral side openings or windows  66  on both opposite lateral sides of each preload section into each of the holes  62 . The contact preload sections  48  are arranged in lines parallel with direction A. In this embodiment the holes  62  have a slight taper between walls  68 ,  69  towards the distal bottom end of the holes  62 . However, in an alternate embodiment this taper need not be provided. 
     When the connector  10  is assembled, the cover  20  is typically snap fitted over the base  18 . The wedge shaped tips  64  of the preload sections  48  help to wedge the pairs of contact arms  44  apart during the assembly of the cover  20  to the base  18 . The cover  20  can slide relative to the base as indicated by arrow A when the cam lever  22  is moved down and in a reverse direction when the lever is moved up. FIGS. 3A and 3B show the connector  10  at a first position for connecting or removing the first electrical component  70  with the connector  10 . In this first position the cover  20  is located relative to the base  18  such that the holes  62  and openings  66  are offset from the contact areas  44  of the contacts  14 . The tail ends  34  of the contacts  14  are shown connected to a printed circuit board  72  by solder  74 . When the cover  20  is connected to the base  18  and the cover and base are in their first relative position, the contact preload portions  48   a  are inserted between respective pairs of arms  40  of each contact  14  into areas  42 . The contact preload sections  48  are wider than the space between contact areas  44 . Therefore, the pairs of arms  40  are spread apart by the preload sections  48  and thereby preloaded against the lateral sides of the preload sections  48 . With the connector  10  in the first position, the male contact pins  76  of the component  70  can be inserted into the holes  62  through the top surface  50  of the cover  20 . As the pins  76  extend into the holes  62  they can be contacted by the opposing walls  68 ,  69 . This causes the distal ends  76   a  of the pins  76  to be sandwiched between the two walls  68 ,  69 . In the preferred embodiment, the walls  68 ,  69  only contact the distal ends  76   a  of the pins  76  to minimize frictional insertion forces of the pins into the holes  62 . However, any suitable areas and lengths of contact between the pins  76  and walls  68  and/or  69  could be provided. In an alternate embodiment, the distal ends of the pins need not contact the walls  68  and/or  69  when inserted into the holes  62 . Referring also to FIG. 3C, in this embodiment the pins  76  have a general circular cross-section. However, any suitable cross-sectional shape could be provided. In this embodiment the walls  68 ,  69  have curved surfaces to cooperatingly mate with the distal ends  76   a  of the pins  76 . The pins  76  are wider than the preload sections  48 . Thus, lateral sides  76   b  of the pins  76  extend out of the openings  66 . When the pins  76  are inserted in the holes  62 , contact with the walls  68 ,  69  slightly resists insertion, but only by a relatively small amount (e.g., a total of 10 pounds or less). The surfaces of the walls  68 ,  69  can be configured to reduce this initial insertion force to minimize frictional forces by reducing contact area, but still allow the walls  68 ,  69  to support the sides  76   c  and/or  76   d  of the pins  76 . In an alternate embodiment only the one side  76   c  need contact the preload section  48 . Alternatively, neither side  76   c  or  76   d  is contacted by the preload section  48 ; except perhaps as a spaced limit or stop surface to stop bending of the pins  76  at predetermined deformations. In the embodiment shown in FIG. 3C, the preload sections  48  provide a function of a strain relief for the pins  76 . More specifically, the surfaces of the walls  68 ,  69  in the holes  62  limit bending of the pins  76  relative to the cover  20  and the main body  71  of the component  70  as the pins move into and out of contact with the electrical contacts  14 . This reduces strain on the pins, such as on the solder joint connections of the pins  76  with the main body  71 . Thus, there is less risk of damage to the component  70  at the connections between its pins and its main body. This could also allow the pins to have smaller cross-sectional shapes with no increase in pin deformation as the pins contact the electrical contacts in the connector  10 . Thus, contact pitch or spacing between contact pins could be reduced. 
     Referring now to FIGS. 4A and 4B, the connector  10  is shown at a second position wherein the cover  20  and the component  70  have been moved to a second position relative to the base  18 . More specifically, when a user moves the lever  22  from the up position shown in FIG. 1 to a down position into the latches  24 , the cover  20  is moved in direction A relative to the base  18 . The component  70  is moved with the cover  20 . As seen with reference to FIG. 4C, the pins  76  are moved into a position between respective pairs of arms  40  of the contacts  14 . The contact areas  44  of the contacts  14  move off of the preload portions  48   a  and onto the sides  76   b  of the pins  76 ; the sides  76   b  extending out of the openings  66 . Because the pins  76  are wider than the preload sections  48 , the arms  40  are wedged or deflected outward when they contact the pins  76 . Thus, the contact areas  44  and pins  76  wipe against each other. This contact wiping action ensures a good electrical connection between the contacts  76 ,  14 . Since contacts  14  are preloaded, a reduced force is required to deflect contacts  14  with pins  76  than without preload portions  48   a.  This helps reduce stress build up in the housing  12  during actuation. Even with the preloading, a sufficient force is still exerted by the arms  40  against the pins  76 . 
     The initial mating angle and the pin tip is preferably optimized. An approach to doing this, as described above, is to design a cover for the connector so that small elongated pillars of plastic are between the contact pins. These pillars are slightly smaller in width than the diameter of the pins. When the assembly is first inserted, the plastic pillars will be inserted between the tines of the contacts and will open them so that they are pre-loaded open. This means that there will be some z-axis force required to assemble the connector, but significantly less than that seen by a normal pin. The pin/cover assembly is then cammed into place, laterally contacting the receptacle contacts. These pillars have an additional function, since they will be also provided strain relief of the pin to prevent solder joint damage of the small diameter pin. Subsequent movement of the lever  22  to an up position will move the cover  20  and pins  76  back to the position shown in FIGS. 3A-3C to allow the component  70  to be removed if necessary. 
     It should be understood that the foregoing description is only illustrative of the invention. Various alternatives and modifications can be devised by those skilled in the art without departing from the invention. Accordingly, the present invention is intended to embrace all such alternatives, modifications and variances which fall within the scope of the appended claims.