Patent Document

CROSS-REFERENCE TO RELATED APPLICATIONS 
   This is a continuation application of a copending patent application Ser. No. 10/329,022, filed Dec. 23, 2002, now U.S. Pat. No. 6,783,400. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to electrical connector assemblies, and more particularly to a connector assembly having two mating connectors used for high-speed signal transmission. 
   2. Description of Related Art 
   High-speed digital electronic apparatus, such as certain communication equipments and computer servers, require fast and accurate signal transmission. These apparatus have electronic components including connectors, wires, circuit boards, and integrated circuit packages. In low-speed applications, these components can function normally in cooperation with each other. However, in high-speed applications, conductivity and other electrical characteristics of these components become critical in ensuring that the electrical performance of the apparatus as a whole is satisfactory. 
   The faster the signal transmission required of an electronic apparatus, the harder it is to build suitable electrical connectors for the apparatus. One of the primary electrical factors affecting high-speed performance in connectors is cross talk mutually induced between two adjacent contacts of the connector. The intensity of cross talk depends on the distance between the two adjacent contacts. 
   Today, as electrical products become smaller and smaller, so too do their components such as connectors. In addition, the number of contacts in contemporary connectors is increasing due to the demand for more signal transmission paths and faster transmission speeds. Therefore, the distance between adjacent contacts inside a typical connector is becoming less and less. Cross talk induced between the contacts is becoming increasingly significant, and needs to be carefully addressed. 
   One way to deal with cross-talk inside a connector is to establish a ground reference means between every two contacts of the connector. U.S. Pat. No. 5,645,436 shows an example of a conventional connector system including jack and plug connectors. Each connector includes a plurality of signal contacts arranged in several rows and columns in an electrically insulative body. Signal paths comprising mutually engaged contacts of the jack and plug connectors have ground means alternately located therebetween. As a result, the number of contacts installed inside the jack and plug connectors is increased. In addition, manufacturing of the ground means and signal contacts becomes significantly complicated due to the different structural designs of the signal contacts and ground means. Furthermore, the increased number of contacts results in more difficulty when installing the contacts into the connector housing, because only a smaller pitch between every two adjacent receiving holes in the housing is available. These difficulties in manufacturing increase costs significantly, and do not necessarily guarantee better electrical performance. 
   Another way to deal with cross talk is to transmit differential signals in a connector, as described in the book High-Speed Digital Design (by Howard W. Johnson and Martin Graham, pp. 319–320). Such connector can provide better electrical performance with regard to impedance matching, cross talk reduction, and electromagnetic interference (EMI) reduction. What is needed is an electrical connector transmitting differential signals, which can overcome the above-described shortcomings of conventional connectors. 
   SUMMARY OF THE INVENTION 
   It is therefore an object of the present invention to provide an electrical connector assembly for high-speed signal transmission which has a simplified structure and enhanced electrical performance. 
   To achieve the above object, an electrical connector assembly of the present invention is provided to electrically connect two printed circuit boards. The connector assembly includes a first board-to-board connector and a second board-to-board connector mounted on the two printed circuit boards respectively. The first connector comprises a first insulative housing receiving a multiplicity of first contacts. The second connector comprises a second insulative housing receiving a multiplicity of second contacts. The first housing comprises an insulative mating part, and a multiplicity of first contact-receiving passages defined therein. The first passages are arranged along two opposing lengthwise sides of the mating part, and receive the first contacts therein. The second housing defines a mating groove corresponding to the mating part of the first connector. The second contacts are positioned at two lengthwise sides of the mating slot, and correspond to complementarily mating first contacts of the first connector. Thus the first and second contacts can electrically mate with each other to electrically interconnect the two printed circuit boards. 
   In a first preferred embodiment of the invention, the first contacts comprise a plurality of first signal contacts, a plurality of first ground contacts, and a plurality of first shield-joint contacts. 
   The first contacts are arranged in the first passages, and divided into several successively arranged groups. In each group, there are two pairs of first signal contacts. Each pair of first signal contacts transmits one set of differential signals. Each pair of first signal contacts is installed in the first passages almost adjacent the other pair of first signal contacts, with one first shield-joint contact separating the two pairs of first signal contacts. A first passage between first signal contacts of the same pair is empty. Two first ground contacts are installed in two of the first passages at respective opposite ends of the group of first contacts. 
   The second contacts are arranged in the second passages corresponding to the respective first contacts. The second contacts comprise a plurality of second signal contacts, a plurality of second ground contacts, and a plurality of second shield-joint contacts. The second signal contacts are paired corresponding to the first signal contacts. 
   Due to the wide interval between adjacent signal contacts, cross-talk between adjacent signal contacts can be reduced. In addition, the signal contacts are well shielded by the ground contacts and the shield-joint contacts. This significantly facilitates suppression of any EMI noise emanating from these signal transmission paths. Furthermore, because the distances between the paired signal contacts is increased, the impedance of the first and second connectors increases at the same time in order to match impedance of the signal circuitry at other electronic components along the same signal transmitting paths. 
   In a second preferred embodiment of the invention, the empty passage within each pair of signal contacts is not present. A distance between adjacent passages receiving a pair of signal contacts is twice as long as a distance between any other adjacent passages. In a third preferred embodiment of the invention, a first passage between first signal contacts of the same pair has a spare contact that is not used to transmit any signals. 
   Other objects, advantages and novel features of the present invention will be drawn from the following detailed description of the preferred embodiments of the present invention with the attached drawings, in which: 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a simplified, exploded isometric view of an electrical connector assembly in accordance with a first preferred embodiment of the present invention, showing a first connector and a second connector respectively with contacts installed therein; 
       FIG. 2  is an enlarged view of a circled portion II of  FIG. 1 ; 
       FIG. 3  is an enlarged view of a circled portion III of  FIG. 1 ; 
       FIG. 4  is an enlarged, isometric sectional view of the electrical connector assembly of  FIG. 1 , taken along line IV—IV of  FIG. 1 ; 
       FIG. 5  is a simplified, exploded isometric view of an electrical connector assembly in accordance with a second preferred embodiment of the present invention, showing a first connector and a second connector respectively with contacts installed therein; 
       FIG. 6  is an enlarged view of a circled portion VI of  FIG. 5 ; 
       FIG. 7  is an enlarged view of a circled portion VII of  FIG. 5 ; 
       FIG. 8  is a simplified, exploded isometric view of an electrical connector assembly in accordance with a third preferred embodiment of the present invention, showing a first connector and a second connector respectively with contacts installed therein; 
       FIG. 9  is an enlarged view of a circled portion IX of  FIG. 8 ; and 
       FIG. 10  is an enlarged view of a circled portion X of  FIG. 8 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Reference will now be in detail to the preferred embodiments of the present invention. 
   It should be noted that for a better understanding of the invention, most like components are designated by like reference numerals throughout the various figures of the embodiments. Referring to  FIGS. 1 to 4 , an electrical connector assembly  1  in accordance with a first preferred embodiment of the present invention includes a first board-to-board connector  2  and a second board-to-board connector  3  adapted to mate with each other. 
   The first connector  2 , a receptacle one of the assembly, includes a first insulative housing  21  receiving a multiplicity of first contacts  22 , and two first shield plates  26  separately attached on each of two lengthwise exterior surfaces of the first housing  21 . The first housing  21  defines a first mounting surface  211  seated on a printed circuit board (not shown), and a first mating surface  212  opposite to the first mounting surface  211  and facing toward the second connector  3 . An elongated mating part  213  is formed along a lengthwise central portion of the first mating surface  212 , and is surrounded on three sides by a U-shaped slot. The mating part  213  includes a multiplicity of first contact-receiving passages  214  defined therein, the first passages  214  being arranged along two opposing lengthwise sides of the mating part  213  at equal intervals. Each first passage  214  has two openings. One opening communicates with the slot, and the other opening is located at the first mounting surface  211 . 
   Each first contact  22  includes a tail portion  221 , a fixing portion  222 , a joint portion  223 , and an engaging portion  224 . The first contacts  22  comprise three types: first signal contacts  22 A, first ground contacts  22 B, and first shield-joint contacts  22 C. The first signal contacts  22 A are used to transmit desired signals for the first connector  2 . The first ground contacts  22 B are grounded when they are attached to the printed circuit board. Finally, the first shield-joint contacts  22 C are usually grounded and electrically engaged with a corresponding first shield plate  26 . 
   The first contacts  22  are arranged in the first passages  214 , and divided into several successively arranged groups. Each group of first contacts  22  includes seven contacts: four first signal contacts  22 A, two first ground contacts  22 B, and one first shield joint contact  22 C. The four first signal contacts  22 A are paired as two differential signal transmission paths. Each pair of first signal contacts  22 A is installed in the first passages  214  almost adjacent the other pair of first signal contacts  22 A, with only the shield-joint contact  22 C being located in a centermost first passage  214  separating the two pairs of first signal contacts  22 A. A first passage  214  between first signal contacts  22 A of the same pair is empty. The two first ground contacts  22 B are installed in two of the first passages  214  at respective opposite ends of the group of first contacts  22 . 
   Each group of first contacts  22  has the same arrangement of first contacts  22  therein as described above. Each two adjacent groups of first contacts  22  overlap at one first ground contact  22 B. That is, each two adjacent groups of first contacts  22  share the first ground contact  22 B that is located at a common end of the two adjacent groups of first contacts  22 . Due to the empty first passages  214 , signal noise can be reduced for each differential first signal contact pair  22 A. Thus stable high-frequency signal transmission can easily be achieved by the contact arrangement of the first connector  2 . 
   The second connector  3 , a plug one of the assembly, includes a second insulative housing  31 , a multiplicity of second contacts  32  received in the second housing  31 , and two second shielding plates  36  separately attached on each of two lengthwise exterior surfaces of the second housing  31 . The second housing  31  defines a second mounting surface  311  seated on a printed circuit board (not shown), and a second mating surface  312  opposite to the second mounting surface  311  and facing toward the first connector  2 . A mating groove  313  is defined along a lengthwise central portion of the second mating surface  312 . A multiplicity of pairs of second contact-receiving passages  314  is defined in opposite lengthwise walls of the housing  31  at the mating groove  313 , corresponding to the first passages  214  of the first connector  2 . Each second passage  314  has two openings. One opening communicates with the mating groove  313 , and the other opening is located at the second mounting surface  311 . 
   Each second contact  32  includes a mating portion  322  mating with a corresponding first contact  22 , and a solder tail  321  perpendicular to the mating portion  322  and extending out of the second housing  31 . The second contacts  32  comprise three types: second signal contacts  32 A, second ground contacts  32 B, and second shield-joint contacts  32 C. These three types of second contacts  32  correspond to the above-described three types of first contacts  22 . The second signal contacts  32 A are used to transmit desired signals for the second connector  3 . The second ground contacts  32 B are grounded when they are attached to the printed circuit board. The second shield-joint contacts  32 C are usually grounded and electrically engaged with a corresponding second shield plate  36 . 
   The second contacts  32  are arranged in the second passages  314 . The second signal contacts  32 A are installed in the second passages  314  corresponding to the first signal contacts  22 A. The second ground contacts  32 B are installed in the second passages  314  corresponding to the first ground contacts  22 B. The second shield-joint contacts  32 C are installed in the second passages  314  corresponding to the first shield-joint contacts  22 C. A second passage  314  between second signal contacts  32 A of the same pair is empty, in like manner as described above in relation to the first signal contacts  22 A. 
   Therefore, when the second connector  3  is mated with the first connector  2 , all the signal contacts  22 A,  32 A are well shielded by the ground contacts  22 B,  22 C,  32 B,  32 C and by the first and second shielding plates  26 ,  36 . This significantly facilitates suppression of any EMI noise emanating from these signal transmission paths. In addition, every signal contact  22 A,  32 A of its respective differential signal pair is further separated by an empty first or second passage  214 ,  314 . The enlarged intervening space between respective adjacent signal contacts  22 A,  32 A reduces cross talk and improves their electrical performance. 
   Because the distance between each paired first signal contacts  22 A is increased, the impedance of the first connector  2  increases at the same time in order to match impedance of the signal circuitry at other electronic components along the same transmitting path. Similar advantages are obtained for the second connector  3  having a similar arrangement of paired second signal contacts  32 A. 
   Referring to  FIGS. 5 to 7 , an electrical connector assembly  4  in accordance with a second preferred embodiment of the present invention includes a first board-to-board connector  202  and a second board-to-board connector  302  adapted to mate with each other. An insulative mating part  2132  of the first connector  202  includes a multiplicity of first contact-receiving passages  2142  defined in opposite lengthwise sides of the mating part  2132 . 
   First contacts  2202  comprise first signal, ground and shield-joint contacts  2202 A,  2202 B,  2202 C arranged in the first passages  2142 . The configuration of the second preferred embodiment is similar to the above-described configuration of the first preferred embodiment, except that the empty first passages  214  of the first preferred embodiment are not found in the mating part  2132  of the second preferred embodiment. A distance between adjacent first passages  2142  receiving a pair of first signal contacts  2202 A is twice as long as a distance between any other adjacent first passages  2142 . 
   A mating groove  3132  is defined in the second connector  302 . A multiplicity of pairs of second contact-receiving passages  3142  is defined in opposite lengthwise walls of the second insulative housing  3102  at the mating grove  3132 , corresponding to the first passages  2142  of the first connector  2112 . 
   Second contacts  3202  are arranged in the second passages  3142 . Second signal contacts  3202 A installed in the second passages  3142  correspond to the first signal contacts  2202 A. Second ground contacts  3202 B installed in the second passages  3142  correspond to the first ground contacts  2202 B. Second shield-joint contacts  3202 C installed in the second passages  3142  correspond to the first shield-joint contacts  2202 C. 
   Referring to  FIGS. 8 to 10 , an electrical connector assembly  5  in accordance with a third preferred embodiment of the present invention includes a first board-to-board connector  203  and a second board-to-board connector  303  adapted to mate with each other. An insulative mating part  2133  of the first connector  203  includes a multiplicity of first contact-receiving passages  2143  defined in opposite lengthwise sides of the mating part  2133 . 
   The first contacts  2203  comprise first signal, ground, shield-joint and spare contacts  2203 A,  2203 B,  2203 C,  2203 D. The spare contacts  2203 D are not used to transmit any signals. The configuration of the third preferred embodiment is similar to the above-described configuration of the first preferred embodiment, except that the empty first passages  214  of the first preferred embodiment are replaced by the first passages  2143 , with the first passages  2143  receiving the spare contacts  2203 D. 
   A mating groove  3133  is defined in the second connector  303 . A multiplicity of pairs of second contact-receiving passages  3143  is defined in opposite lengthwise walls of the second insulative housing  3103  at the mating groove  3133 , corresponding to the first passages  2143  of the first connector  203 . 
   Second contacts  3203  are arranged in the second passages  3143 . Second signal contacts  3203 A installed in the second passages  3143  correspond to the first signal contacts  2203 A. Second ground contacts  3203 B installed in the second passages  3143  correspond to the first ground contacts  2203 B. Second shield-joint contacts  3203 C installed in the second passages  3143  correspond to the first shield-joint contacts  2203 C. Second spare contacts  3203 D installed in the second passages  3143  correspond to the first spare contacts  2203 D. 
   While the present invention has been described with reference to specific embodiments, the description is illustrative of the invention and is not to be construed as limiting the invention. Various modifications to the present invention can be made to the preferred embodiments by those skilled in the art without departing from the true spirit and scope of the invention as defined by the appended claims.

Technology Category: 5