Abstract:
The invention is directed to a connector including an insulating housing with a plurality of channels accommodating at least one right-angle electro-conductive terminal leading from a mating side of the connector to a surface mount side of the connector. At least a part of channels is provided with a support surface which is adapted to pivotably support the terminal, the support surface being located at a distance above a bottom surface of these channel.

Description:
FIELD OF THE INVENTION 
     The invention relates to a connector, comprising an insulating housing with a plurality of channels accommodating electro-conductive terminals leading from a mating side to a surface mount, for a surface mount connection to a contact pad of a circuit board. 
     BACKGROUND OF THE INVENTION 
     Connectors for mounting to circuit boards or the like are provided with contact leads or terminals that engage contact pads on the surface of the circuit board. After positioning and securing the connector with respect to the circuit board, the terminals are usually soldered to the circuit board. To obtain a reliable soldered contact between the terminal leads and the circuitry of the circuit board, it is important that the terminals of the connector are coplanar and within the proximity of the solder pads on the surface of the circuit board. If the terminals are not coplanar to each other within a small range, typically about 0.10 mm, the lowest positioned terminals will sit on the top surface of the contact pad where they will be securely soldered, while the highest positioned terminals will be so far from the contact pads that they will not become securely soldered. 
     To prevent coplanarity problems, it has been proposed in EP 1 102 357 to have terminals pivotably floating within corresponding channels, in such a way that each terminal end pivots down under its own weight. When the connector is positioned for soldering, the terminal ends all rest on the corresponding contact pads on the circuit board, while a good contact is obtained under the weight of the pivoting terminals. The connector in EP 1 102 357 is particularly suitable when the terminal end does not require to be expandable in a resilient way, for instance to receive a pin of a mating connector. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide a connector with improved surface mount solderability without requiring very accurate coplanarity of the contact terminal ends for a broad range of surface mount connector types. 
     The object of the invention is achieved with a connector according to claim  1 . 
     As a result, when the connector is positioned for being mounted to a circuit board, the connection elements rest on the contact pads by their own weight and/or with a reaction force. As a result, all terminals rest on the corresponding contact pads or solder pastes on the printed circuit board, enabling secure soldering. Unevenness of the printed circuit board is also compensated. 
     The contact mating end comprise two opposite resilient fingers for resiliently engaging a pin of a mating connector. One of the resilient fingers may then be pivotably supported by the support surface in the channel. If the two resilient fingers are above each other, the upper resilient finger can, e.g., be pivotably supported by the support surface, so the lower resilient finger may be flexed downwardly when a connector pin is inserted between the two resilient fingers. Due to the fact that the pivot point is at a distance above the bottom of the channel, both fingers have full freedom to flex away from each other when a connector pin is inserted. After insertion of a contact pin between the resilient fingers of the floating terminal, the contact forces are equally divided over the two resilient fingers, regardless of the exact position of the inserted pins. 
     In one embodiment of such a connector, the tip of at least one of the resilient fingers comprises one or more stubs resting on a support surface. The supported resilient finger can for example have two stubs symmetrically arranged resting on two opposite support surfaces at either side of the resilient finger, in order to obtain a balanced support. 
     In an alternative embodiment, the two opposite resilient fingers may clamp around the support, which may for instance be a pre-load rail. Such a pre-load rail may for example be used to push the resilient fingers apart to allow easier insertion of a contact pin of a mating connector. The resilient fingers may have bent tips. These bent tips are arranged in such a way that the contact point between the upper finger and the support is at a distance closer to the mating side of the connector than the contact point between the lower finger and the support. This creates a moment resulting in a reaction force pushing the surface mount end downwards, which results in a better contact with the circuit board when the connector is positioned for soldering. The distance between the two contact points may be dimensioned such that the created moment is in balance with the connectors own weight in order to prevent that the surface mount ends lift the connector. 
     To limit the moveability of the terminal in its longitudinal direction, the terminal may be provided with one or more projections, such as a tab. A tab may stop the terminal from moving backward when a mating contact pin is inserted, without blocking the floating. The terminal may also have a stop preventing the terminal from moving too far into the direction of the mating side when a pin of a mating connector is taken out of the connector. 
     The terminals have a first leg with the connection end under an angle with a second leg comprising the terminal end. The first and second legs are substantially under right angles with each other. 
     Optionally, a weight block can be used to provide additional weight to the surface mount end of the connection element. This results in an extra force pushing the contact ends downwardly. If one of the terminals keeps hanging on a projecting irregularity, such as a burr, the full weight of the block rests on the burr, so the weight of the block may push the terminal past the burr. Moreover, the weight of the block or blocks may shift the center of gravity and stabilize the position of the connector. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be understood with reference to the figures wherein: 
         FIG. 1 : shows in perspective view a connector according to the invention; 
         FIG. 2 : shows in perspective view a terminal of the connector of  FIG. 1 ; 
         FIG. 3 : shows in cross section the connector of  FIG. 1  before being mounted on a circuit board; 
         FIG. 4 : shows in cross section the connector of  FIG. 1  mounted on a circuit board; 
         FIG. 5 : shows in cross section the connector of  FIG. 1  mounted on a circuit board after connection with a mating connector; 
         FIG. 6 : shows in cross section an alternative embodiment of a connector according to the invention before mounting on a circuit board; 
         FIG. 7 : shows in cross section a third embodiment of a connector according to the invention before being mounted on a circuit board; 
         FIG. 8 : shows in cross section the connector of  FIG. 7  mounted on a circuit board; 
         FIG. 9 : shows in cross section the connector of  FIG. 7  mounted on a circuit board after connection with a mating connector; 
         FIG. 10 : shows in cross section a fourth embodiment of a connector according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       FIG. 1  shows an example of surface mount connector  1  according to the present invention. The connector  1  comprises an insulating housing  2  with a plurality of electro-conductive terminals  4  leading from a mating side  5  of the connector  1  to a surface mount side  6  of the connector  1 . In use, the surface mount connector  1  is connected to a printed circuit board by soldering the terminals  4  on the contact pads of the circuit board. At its mating side  5 , a mating connector can be coupled to the connector  1 . 
     As can be seen in  FIG. 1 , openings  9  are arranged in two staggered rows  16 ,  17  corresponding to a staggered, space-saving arrangement of the terminals  4  within the connector  1 . In an alternative embodiment, the terminals can be arranged in a non-staggered configuration, e.g., right above one another, or in any other suitable arrangement. 
       FIG. 2  shows in perspective view a terminal or contact lead  4  as encased in the connector  1  of  FIG. 1 . The terminal  4  comprises a connection end or connection mating portion  7  and a bent surface mount end  8 . The connection mating portion  7  is accessible from the mating side  5  of the connector  1  via the openings  9 . The bent surface mount end  8  projects from the surface mount side  6  of the connector  1 . The connection mating portion  7  is part of a first leg  10  of the terminal  4  which is under right angles with a second leg  11  comprising the surface mount end  8 . The connection mating portion  7  comprises an upper resilient finger  7   a  and a lower resilient finger  7   b  linked by a bridging section  14  at a distance closer to the second leg  11  of the terminal  4 . 
     The resilient fingers  7   a ,  7   b  comprise, respectively:
         a first portion  12 ,  13  connected to the bridging section  14 ; and   a second cantilevered arm  12   a ,  13   a  extending from the first portion  12 ,  13 .       

     The second cantilevered arms  12   a ,  13   a  are further bent inwardly with respect to the first portion  12 ,  13  so that they converge towards each other. The second cantilevered arms  12   a ,  13   a  comprise a tip  22 , 23  having inwardly facing opposed contact end. Each tip  22 ,  23  is curved in order to enable easier insertion of a pin. Each tip  22 ,  23  is formed with a lateral wing (or extension)  12   b  and  13   b  the purpose of which will be explained below. 
     It should be noted that the total length of the upper resilient finger  7   a  is longer than that one of the lower resilient finger  7   b . Such an arrangement is advantageous for improving downward pivoting movement of the terminal due to gravity force exerted on the terminal. 
     When a mating connector is mated with the connector  1 , pins of the mating connector are introduced into the openings  9  in the connector  1  and are clamped between the two resilient fingers  12 ,  13 . The bridging section  14  is provided with a tab  15  the function of which will be described below. 
       FIG. 3  shows a cross section of the connector  1  of  FIG. 1  in a plane perpendicular to the longitudinal direction of the connector  1 . For reasons of clarity, the cross section of  FIG. 3  represents the terminals  4  as if they were in line above one another. In  FIG. 3 , the connector  1  is not yet mounted and is held at a distance above a printed circuit board  18 . 
     The terminals  4  are accommodated in channels  19  leading to the openings  9 . The channels  19  have a bottom surface  20 . Pre-load rails  21  are arranged in the channels  19  at either side of each opening  9  at a distance above the bottom surface  20 . The pre-load rails  21  are positioned only between the side edges of the connection ends  7 , leaving a free space between the resilient fingers  7   a ,  7   b  for entrance of a pin from a mating connector, as is shown in  FIG. 5 . The pre-load rails  21  push the resilient fingers  7   a ,  7   b  away from each other. This way, the fingers of all contacts are equally spaced so variation in required force to insert a contact pin, resulting from deflection variations is effectively reduced. The lateral wing  12   b  of the upper resilient finger  7   a  has a contact point  24  with the pre-load rail  21 , which is at a distance closer to the opening  9  than the contact point  25  between the pre-load rail  21  and the lateral wing  13   b  of the lower resilient finger  7   b . This creates a moment resulting in a force pushing the surface mount end  8  downwards, enforcing the moment caused by gravity. This way the pre-load rail  21  forms a support surface pivotably supporting the mating portion  7  of the terminal  4 . 
       FIG. 4  shows the connector  1  in the same cross section as shown in  FIG. 3 , after the connector  1  has been mounted on the printed circuit board  18 . While the housing  2  rests on the circuit board  18 , the surface mount ends  8  of the terminals  4  are lifted. Due to the rotational moment caused by the weight of the terminals  4  and by the reaction forces at the contact points  24 ,  25 , all surface mount ends  8  are gently pressed onto corresponding contact pads (not shown) on the circuit board  18 . There are no deficient contacts caused by coplanarity deviancies. Any unevenness of the circuit board  18  is also compensated by the gentle downward pressure on the surface mount ends  8 . 
       FIG. 4  also shows a compatible pin connector  30  to be mated with the connector  1 . The pin connector  30  comprises connector pins  31  projecting from an insulating housing  32 , which can be inserted in openings  9  and between the tips  22 ,  23 , as shown in  FIG. 5 . The pins  31  press the resilient fingers  7   a ,  7   b  away from each other, disengaging them from the pre-load rail  21 . 
     In reference with  FIG. 5 , while inserting a pin  31  into an opening between two resilient fingers  7   a ,  7   b , the exerted force pushes the terminal  4  backwards. To stop a backward movement of the terminal  4 , the channel  19  is provided with an internal stop  33  engaging the tab  15  when the terminal  4  moves backward. 
     In an alternative embodiment, shown in  FIG. 6 , the contact points  24 ,  25  between the pre-load rail  21  and the tips  22 ,  23  are arranged right above each other. In that case, the force pushing down the contact ends  8  is gravitational. To increase this gravitational force, additional weights  34 , for instance a plastic block, can be positioned on the first sections of the terminals close to the second leg  11 . 
       FIG. 7  shows an alternative embodiment of a connector  40  according to the present invention. In the drawing, same referential numbers are used for parts that are the same as with the connector shown in  FIGS. 1-5 . 
     The connector  40  comprises a housing  41  of an insulating material. In the connector  40 , the tips  22 ,  23  are respectively extended with positioning stubs  42 ,  43 , positioned in an upper slot  44  and lower slot  45  respectively. The slots  44 ,  45  extend in a direction parallel to the longitudinal direction of the resilient fingers  7   a ,  7   b . The positioning stubs  42 ,  43  and the slots  44 ,  45  may be of a smaller width than the main part of the resilient fingers  7   a ,  7   b . Inside the housing  41  of the connector  40 , the openings  9  are provided with an inwardly projecting upper rim  46  and a lower rim  47 . The upper rim serves as a support surface for the upper positioning stub  42 . When the connector  40  is positioned on a printed circuit board, the surface mount ends  8  are lifted and the upper rim  46  with the positioning stub  42  forms a pivot point. 
       FIG. 8  shows the connector  40  mounted on a circuit board  18 . The contact ends  8  are lifted to the level of the bottom surface of the housing  2 . Positioning stub  42  rests on the upper rim  46 . 
     In  FIG. 9 , a pin connector  30  with pins  31  is mated to the connector  40 . Pins  31  are inserted in the openings  9  between resilient fingers  7   a ,  7   b . The upper positing stubs  42  do not rest anymore on the upper rims  46 . 
       FIG. 10  shows a fourth possible embodiment of a connector  50  according to the present invention, which is for most parts the same as the embodiment shown in  FIGS. 7 ,  8  and  9 . Again, same referential numbers are used for parts that are the same as with the connector shown in  FIG. 7 . 
     The connector  50  comprises a housing  51  of an insulating material. In the connector  50 , only the upper resilient finger  7   a  has an outer tip  22  extended with a positioning stub  42  positioned in an upper slot  44 . The lower finger  7   b  is not extended with such a stub. An upper rim  46  serves as a support surface for the positioning stub  42 . When the connector  50  is positioned on a printed circuit board, the surface mount ends  8  are lifted and the upper rim  46  forms a pivot point for the positioning stub  42 . Due to the absence of a lower slot, a higher density of channels  19  can be obtained resulting in a more compact connector construction.