Electrical connector

Abstract: An electrical connector (12) has an insulating housing (14) with contact terminals (24) which extend therethrough. The contact terminals (24) are provided to electrically connect a mother board to a daughter board. A board-receiving opening (22) is provided in the housing (14) for reception of the daughter board therein. A pair of latch members (38) are provided on the housing (14) for latching the daughter board to take a predetermined posture with respect to the mother board. A pair of restricting metal plates (54) are mounted on the housing (14) for restricting the latch members (38) from being flexed in a direction to move the paired latch members (38) away from each other. A spring (66) is provided in the board-receiving opening (22) for enabling a spring force to be applied to the daughter board in a direction to urge the daughter board into the predetermined posture against a push force by the daughter board received in the board-receiving opening (22).

Description: The present invention relates to an electrical connector for electrically connecting together, for example, printed circuit boards. In a system including printed circuit boards, a daughter board, such as a single-in-line memory module (SIMM), is connected to a memory control board (called a mother board) for a system extension purpose. An electrical connector has a plastic housing mountable on a mother board. The housing has a slot into which the daughter board is inserted. The daughter board is connected to the mother board with the daughter board inserted in the slot of the housing. At this time, the daughter board has its attitude vertically fixed relative to the surface of the mother board. The daughter board thus fixed is electrically connected to those contact terminals arranged in the slot and placed in contact with the mother board. In order to fix the daughter board at the vertical attitude, a pair of latch members are provided one at each end portion of the socket body such that they are integral with the socket body. Upon the insertion of the daughter board into the slot, the latch members are flexed in a direction to be moved by the daughter board away from each other, that is, are flexed outwardly of the socket body. Upon the full insertion of the daughter board's edge, the latch members are restored back to their initial configuration and the daughter board is sandwiched between the latch members. By so doing, the daughter board is fixedly held at a vertical attitude. Upon the detachment of the daughter board from the housing, the latch members are outwardly flexed in a direction to be moved away from each other. It is thus possible to withdraw the daughter board out of engagement with the latch members. Since there is the need to detachably fix the daughter board to the mother board and to achieve their positive electrical connection, it is necessary to secure a ready attaching/detaching operation of both the boards and to ensure the reliabilility with which both the boards are firmly brought into engagement with each other. In those structures where emphasis is placed on their improved operation, the socket members are liable to produce cracks, defects, bends etc; as well as involve inadequate durability, because the socket members, like the socket body, are made of plastics. Upon the repetitive attachment and detachment of the daughter board many times, the latch members are deformed beyond their elastic deformation limit and are difficult to restore back to their initial configuration due to fatigue in the deformed area. As a result, a force acting to hold the daughter board in a sandwiched relation is lowered, thus being liable to produce a poor electrical connection between the daughter board and the associated contact terminals. There sometimes occurs a damage to, or a fracture of, the latch members. In US-A-5004429 an electrical (SIMM) socket has a non-conductive housing with a receiving slot and a plurality of electrically conductive terminals. Each terminal may include a pair of contact beams for accepting the edge of a board at first alignment with minimal insertion force before the board is rotated to a second alignment in order to establish an electrical contact. At each end of the socket there is a retaining means for accurately positioning and retaining the board once in its fully inserted alignment. The retaining means includes a rigid rear wall for defining the limit of rotation of the board, and the wall may include a fonvardly extending projection for engaging a correspondingly dimensioned aperture in the board. The socket further comprises deflectable metal latches for retaining the board in the fully inserted alignment adjacent the rear walls of the socket. Each latch may have a rearwardly facing locking surface to act on the board and hold it against the rigid rear wall, and a forwardly facing ramped surface for facilitating the automatic deflection of the latch in response to the forces exerted during insertion of the board. It is an object of the present invention to provide an electrical connector which is simpler in structure and lower in manufacturing cost and ensures not only high durability of latch members but also a firm electrical connection between a circuit board and contacts. According to the invention there is provided an electrical connector for connecting a first circuit board to a second circuit board the electrical connector comprising: an insulative housing mountable on the first circuit board the housing having a recess for receiving the second circuit board wherein a plurality of contacts are positioned in the recess and configured to make an electrical connection with the second circuit board; a pair of latch members for latching the second circuit board at a predetermined posture with respect to the first circuit board, the pair of latch members being arranged in an opposed relation to each other with the recess placed therebetween; and a pair of restricting members for limiting movement of the latch members when the respective latch members are flexed in a direction away from each other, the pair of restricting members being arranged in an opposed relation to each other with the paired latch members located therebetween; characterised in that spring means is provided for applying a force to the second circuit board in a direction generally outwardly of the recess to co-operate with the latch members to maintain the second circuit board in the predetermined posture when the second circuit board is received in the recess. According to one embodiment of the present invention, the housing has guiding members for guiding the second circuit board into the recess, the guiding members being located in an opposed relation with the recess placed therebetween. Preferably, the housing has a spring receiving cavity having an open lower end, the spring means being insertable into the spring receiving cavity through the lower end. In this case there are a plurality of said spring means located in a plurality of said spring receiving cavities, each restricting member having a portion for supporting associated spring means the supporting portion extending across the open lower end of the associated spring receiving cavity. Each latch member of the housing may have an area that contacts a lateral edge of the second circuit board, each latch member being tapered towards its base end at the contacting area. Preferably, each latch member of the housing has a projection and the associated restricting member has a cut-out for engaging with the projection of the latch member. The latch members may also have a second projection for engaging with a slit in a lateral edge of the second circuit board when the second circuit board is positioned in the predetermined posture. The latch members can be integral with the housing. In one embodiment the or each spring means is a coil spring. According to the present invention, the flexing of the latch member is restricted by the restricting member, ensuring high durability of the latch member. Thus a stable and strong holding force can be maintained even after repetitive attachment and detachment of the second circuit board. A firm positive connection can be achieved between the first and second circuit boards by a mutual cooperation and coordination among the guiding members, latch members and restricting members. It is possible to attach and detach the second circuit board to and from the socket body with a small force applied by a simple operation. Furthermore, the latch members may be molded integral with the housing as in the conventional counterpart structure and hence a simpler structure is employed, thus not only improving their durability but also lowering the manufacturing cost. This invention can be more fully understood from the following detailed description when taken in conjunction with the accompanying drawings, in which: Fig. 1 is a perspective view showing an electrical connector with mother and daughter boards (first and second circuit boards respectively); Fig. 2 is a cross-sectional view, as taken along line II-II in Fig. 1, showing a contact in a housing; Fig. 3. is a perspective view, partly taken away, showing one end portion of the connector; Fig. 4. is a perspective view, partly taken away, showing one end portion of the connector with a restricting member or reinforcing member in the form of a metal plate and spring means, in this case a coil spring, omitted; Fig. 5. is a cross-sectional view, taken along V-V in Fig. 4, showing one end portion of the connector; and Fig.6 is a perspective view showing the restricting member, in this case a reinforcing metal plate. As shown in Fig. 1, an electrical connector 12 of the present invention is of such a type that a second circuit board, or daughter board 2 is vertically connected to a first circuit board, or mother board 1. The first circuit board 1 is comprised of, for example, a memory control board. The second circuit board 2 is, for example, an SIMM (single-in-line memory module) on which memory chips 3 are mounted. A plurality of solder pads 5 are provided at a base end portion 4 of the second circuit board 2 such that they are arranged in a direction of the width of the second circuit board 2. A slit 6 is provided at a predetermined position at each side portion of the first circuit board 2. The connector 12 has an elongated housing 14 molded of an elastic insulating material, such as suitable plastics. In the following explanation, a direction X denotes the longitudinal direction of the housing 14 and width direction of the second circuit board 2; a direction Y, the transverse direction of the housing 14; and a direction Z, the height direction of the housing 14. The housing 14 has a bottom surface 16 to be mounted on the first circuit board 1 and a top surface 18 on which the second circuit board 2 is mounted. A leg 20 is provided at each end portion of the housing 14 and extends in the Z-direction at that location where the housing 14 is mounted on the first circuit board 1. The legs 20 inserted through the first circuit board 1 are fixed in place by soldering, etc., to allow an electrical connection to be made. A recess or board-receiving opening 22 is provided along the X-direction in that top surface 18 of the housing 14 where the second circuit board is mounted. A plurality of contact terminals 24 are arranged, as a row array, in the recess or opening 22 along the X-direction. The contact terminals 24 can be arbitrarily selected from the known elastic contact terminals for circuit board (SIMM, etc.) connection. The contacts 24 may be of such a type as indicated by a cross-sectional configuration in, for example, Fig. 2. The contacts 24 are electrically connected to the first circuit board 1 by a proper method for, for example, inserting one end portion 24a of the contacts 24 through a through hole la of the first circuit board 1. As shown in Figs. 3 and 4, a spring receiving cavity 26 is provided in the housing 14 at an area near each end of the recess 22 and extends from the bottom surface of the recess 22 toward the bottom surface 16 of the housing, noting that one end portion only of the recess 22 is shown for brevity's sake. As shown in Figs. 3 to 5, a latch receiving cavity 28 is provided at each end side of the recess 22. The cavity 28 extends through the housing 14 in the Z-direction and communicates with the recess 22 in the X-direction. The latch receiving cavity 28 communicates with the spring receiving cavity 26 via a depression 30 provided at the bottom surface 16 of the housing 14. A supporting or cover portion 58 of a reinforcing or restricting member 54 as will be set out below is so configured as to be fitted into the depression 30 of the housing 14. A pair of guiding members in the form of arms 32 are molded integral with the housing 14 and arranged at each end portion of the top surface 18. The guiding members of guide arms 32 have their opposed surfaces 34 and 36 facing in the Y direction with the latch receiving cavity 28 therebetween. A distance between the opposed wall surfaces 34 and 36 corresponds to the width of the search circuit board 2. A latch member 38 is located between the opposed wall surfaces 34 and 36 of the guiding members 32. The latch member 38 has its opposite side surfaces 40 provided integral with the opposed wall surfaces 34 and 36 of the guiding members 32, and upper and lower ends 42 and 44 of the latch member 38 are free ends. The lower end 44 of the latch member 38 is inserted into the latch receiving cavity 28. The opposed surfaces of the latch members 38, each, include a projection 46 for engaging with the side slit 6 of the second circuit board 2 and a support surface 48 to be abutted against a lateral edge 7 of the second circuit board. The latch member 38 is elastically deformable in the X direction. In the initial configuration of the latch member 38, the distance between the support surfaces 48 of the latch members 38 is made slightly smaller than the width W of the second circuit board 2 so as to elastically hold both side edges 7 of the second circuit board 2 between the support surfaces 48 of the latch members 38. The latch member 38 preferably has a tab 50 to facilitate disengagement of second circuit board 2 from the projections of the latch members. A projection in the form of a rib 52 projects from the outer surface of the tab 50. The latch member 38 has its support surface 48 tapered as seen in cross-section. The X-direction width t of the latch member 38 at the lower end 44 of the support surface 48 is smaller than the X-direction width t of the latch member 38 at the upper end of the support surface 48. As shown in Fig. 5, the support surface 48 of the latch member 38 is set at an angle of 90° to the top surface 18 and the latch member 38 has an outer wall surface 54a set an angle smaller than 90° to the top surface 18. In the latch member 38 having such a structure, a force acting to urgingly hold the second circuit board in the X direction between the pair of latching members 38 is automatically produced at the top end portions of the latch members 38. During the mounting of the daughter board it is not necessary to apply any excessive holding force from the restricting member 54. Thus a smaller force is required to mount the second circuit board. Referring to Figs. 1 and 3, the paired restricted members 54 are provided one at each end side of the top surface 18 of the housing 14 and each fixedly inserted in the latch receiving cavity 28. The restricting members 54 are arranged in an opposed relation in a manner so as to hold the latch members therebetween. As shown in Fig. 6, the restricting member in the form of a reinforcing metal plate 54 is L-shaped in cross-section. It has a reinforcing section 56 to abut the outer surface side of the latch member 38, and a supporting portion or cover portion 58 for covering the lower surface of the spring receiving cavity 26. During the soldering of the connector 12 to the first circuit board 1, the supporting portion 58 of the restricting member 54 holds spring means in the form of a coil spring 66, as will be set out below, to prevent slippage out of the housing 14. The reinforcing section 56 of the restricting member 54 reinforces the latch member 38 and, upon the attachment and detachment of the second circuit board, restricts the latch member 38 to prevent any undesired flexing. A cutout or slit 60 is provided at the upper end portion of the reinforcing metal section 56 of the restricting member 54 to engage with the rib 52 of the tab 50. Upon flexing the latch members 38 away from each other, the latch members 38 are restricted against any excessive flexing due to the rib 52 engaging with the cutout 60 of the restricting member 54. It is thus possible to prevent a breakage of the latch member 38. In this case, restriction against any excessive flexing of the latch member 38 can be provided by simply forming the cutout slit 60 at the plate-like reinforcing section 56 located at the back of the latch member 38 in the X direction in which case the cutout slit 60 allows a displacement of the rib 52 resulting from the flexing of the latch member 38. This type of restricting member is simpler in its structure. The restricting member 54 restricts the latch member 38 from being flexed as set out above and does not serve to impart a supplementary holding force to the latch member 38 through the internal pushing of the latch member 38. The top end 56a of the reinforcing section 56 of the restricting member 54 is desirably curved to prevent its edge from damaging the latch member as shown in Fig. 6. That portion of the side edge 62 of the reinforcing section 56 which is situated in the latch receiving cavity 28 has holding spikes 64 which bite into the inner wall of the latch member receiving cavity 28. By so doing, the restricting member 54 is fixed to the housing 14. The supporting portion 58 of the restricting member 54 is fitted into the depression 30 of the first circuit board mount surface 16 of the housing 14 and covers the lower side of the spring receiving cavity 26. Spring means, in this case a coil spring 66 is inserted in the associated cavity 26 as shown in Fig. 3, to rest on the upper surface of the supporting portion 58 of the restricting member 54. When the first circuit board 2 is to be mounted in the connector, the second circuit board 2 is placed between the paired guiding arms 32 with the base end portion 4 of the second circuit board 2 facing down towards the recess 22. The second circuit board is slidably moved along the guiding arms 32 toward the contacts 14 until the solder pads 5 of the base and portion 4 of the second circuit board 2 are seated into electrical connection with the contacts 24 at the recess 22. At this time, the projections 46 of the latch members 38 are actuated by the second circuit board 2 to cause the latch members to be moved away from each other, through being elastically deformed. With the base end portion 4 of the second circuit board 2 seated on the contacts 24, the projections 46 of the latch members 38 are brought into engagement with the side slits 6 of the second circuit board 2 and the latch member 38 is elastically restored back to its initial configuration. At the same time, the support surfaces 48 of the latch members 38 are brought into abutting engagement with the lateral edges 7 of the second circuit board to hold the second circuit board 2 between the side surfaces of the latch members 38 at a predetermined posture with respect to the first circuit board. The spring means or coil spring 66 is compressed by the base end portion 4 of the second circuit board, producing a force for pushing up the second circuit board 2 away from the insulative housing 14. By so doing, the projection 46 of the latch member 38 is pushed against an upper edge 6a of the side slit 6 of the second circuit board 2, urging the projectoin 46 into engagement with the slit 6. The second circuit board 2 is positively held in place. This ensures a positive electrical connection between the solder pads 5 of the second circuit board 2 and the contacts 24. Upon the detachment of the daughter board 2 from the connector 12, the latch members 38 are pushed away from each other. This operation is easier to do in the case where the tab 50 is provided integral with the latch member 38. This unlatches the second circuit board 2 from the latch members 38. At this time, the second circuit board 2 is pushed up under a vertical upward spring action of the spring means or coil spring 66 and ejected out of the contact terminals 24 and hence the recess 22. The unlatched second circuit board 2 is then pulled vertically out of the connector 12 until it is freely clear of the connector 12. When the latch members 38 are deformed away from one another during the attachment and detachment of the board 2, each latch member 38 is restricted by it's restricting member 54 from being excessively flexed. This prevents damage to the latch members 38 and ensures improved durability. The present invention is not restricted to the embodiment set out above and various changes or modifications of the present invention can be made. For example, although the second circuit board 2 mounted on the socket (12, 14) has been explained as taking a vertical attitude relative to the first circuit board 4, it may be so mounted as to take a horizontal or an oblique attitude relative to the mother board. As another example, a plurality of recesses 22 may be provided in one housing 14 and a corresponding number of second circuit boards 2 may be provided in one housing in which case latch members 38, restricting members 54, coil springs or spring means 66, and so on, are provided in each recess 22.

Claims: An electrical connector for connecting a first circuit board (1) to a second circuit board (2), the electrical connector comprising: an insulative housing (14) mountable on the first circuit board (1) the housing having a recess (22) for receiving the second circuit board (2) wherein a plurality of contacts (24) are positioned in the recess (22) and configured to make an electrical connection with the second circuit board (2); a pair of latch members (38) for latching the second circuit board (2) at a predetermined posture with respect to the first circuit board (1), the pair of latch members (38) being arranged in an opposed relation to each other with the recess (22) placed therebetween; and a pair of restricting members (54) for limiting movement of the latch members (38) when the respective latch members are flexed in a direction away from each other, the pair of restricting members (54) being arranged in an opposed relation to each other with the paired latch members (38) located therebetween; characterised in that spring means (66) is provided for applying a force to the second circuit board (2) in a direction generally outwardly of the recess to co-operate with the latch members (38) to maintain the second circuit board in the predetermined posture when the second circuit board is received in the recess (22). A connector according to claim 1, further comprises guiding members (32) for guiding the second circuit board (2) into the recess (22) the guiding members (32) being located in an opposed relation with the recess (22) placed therebetween. A connector according to claim 1 or 2, and further comprising a spring receiving cavity (26) having an open lower end, the spring means (66) being insertable into the spring receiving cavity (26) through the lower end. A connector according to claim 3, wherein there are a plurality of said spring means (66) located in a plurality of said spring receiving cavities (26), each restricting member (54) having a portion (58) for supporting associated spring means (66), the supporting portion (58) extending across the open lower end of the associated spring receiving cavity (26). A connector according to any one of claims 1 to 4, wherein each latch member (38) has an area that contacts a lateral edge ofthe second circuit board (2) and each latch member (38) is tapered toward its base end at the contacting area. A connector according to any one of claims 1 to 5, wherein each latch member (38) has a projection (52) and the associated restricting member (54) has a cut-out (60) for engaging with the projection (52) of the latch member (38). A connector according to any one of claims 1 to 6, wherein each latch member (38) has a projection (46) for engaging with a slit (6) in a lateral edge (7) of the second circuit board (2) when the second circuit board is positioned in its pre-determined posture. A connector according to any one of claims 1 to 7 wherein each latch member (38) is integral with the housing (14). A connector according to any one of claims 1 to 8 wherein the or each spring means (66) is a coil spring. A connector according to any one of claims 1 to 9 wherein each restricting member (54) has a reinforcing section (56) abutted against the outer surface side (54a) of the associated latch member (38) to reinforce it.

Inventors: NAI HOCK LWEE
Applicants: BERG ELECTRONICS MFG, CONNECTOR SYSTEMS TECH NV, BERG ELECTRONICS MANUFACTURING B.V., CONNECTOR SYSTEMS TECHNOLOGY N.V.
Application year: 1992
Main classification: H01R23
IPC codes: H01R24, H01R12, H01R13