Electrical connector solder terminal

A connector is provided for mounting a module to a printed circuit board. The connector includes a housing having end walls defining a slot for receiving a module. Terminals are mounted within the housing on either side of the slot. Each terminal includes a tail. A solder mass is attached to each tail and is used to bond the connector to the printed circuit board. The solder mass is attached to each tail without the use of a reflow process. The solder mass can be attached to the tail of the terminal either through a mechanical attachment or through bonding. A reflow process is then used to attach the connector to the printed circuit board.

FIELD OF THE INVENTION

This invention is directed to an electrical connector and, in particular, to a solder terminal for use in an electrical connector and a method of making such a solder terminal for use in an electrical connector.

BACKGROUND OF THE INVENTION

Typical surface mounted connectors include a plurality of terminals and solder masses associated with each terminal. Each solder mass is typically in the shape of a ball and during assembly of the connector, the each solder mass is attached to a respective terminal using a reflow process. Upon assembly of the connector to a printed circuit board a second reflow process is typically used to fuse the terminals to contact pads on the circuit board by way of the solder mass.

It is important that the solder mass be securely attached to the terminal. This is so because the connectors using such solder terminals are generally shipped from one location to another location prior to the electrical connectors being installed on a circuit substrate, such as a printed circuit board. Thus, it is necessary to have sufficient retention of the solder mass to the terminal to ensure that the solder mass is not disengaged from the terminal during transportation. One known method of retaining the solder mass to a terminal is by fusing the solder mass to the terminal through the use of a reflow type process.

OBJECTS AND SUMMARY OF THE INVENTION

A primary object of the present invention is to provide a novel solder bearing terminal.

Another object of the present invention is to provide a method of making the solder bearing terminal.

Another object of the present invention is to provide an electrical connector that uses the solder bearing terminal, and which can be securely mounted to a circuit substrate, such as a printed circuit board.

An object of an embodiment of the present invention is to provide a mechanical engagement between the terminals of the electrical connector and the solder mass provided in the respective terminal.

An object of an embodiment of the present invention is to provide an adhesive engagement between the terminals of the electrical connector and a solder mass.

Yet another objection of the present invention is provide attachment of the solder masses to the terminals without using a reflow process.

Still another object of the present invention is to provide an efficient method for mounting a connector to a printed circuit board.

Briefly, and in accordance with the foregoing, a connector is provided in which a solder mass is securely attached to the tail end of each terminal of the connector. In one embodiment of the present invention, attachment of the solder mass is achieved through a mechanical engagement between the solder mass and the terminal. In another embodiment, the solder mass is securely retained to the terminal by a plating process. In yet another embodiment of the present invention, attachment of the solder mass is achieved through an adhesive engagement between the solder mass and the terminal. The securement of the solder mass can be accomplished by any of the above methods, individually, or by a combination of one or more of the above mechanisms. In each embodiment, engagement of the solder mass and the terminals is achieved without the use of a reflow process.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

A connector20for attachment of a module (not shown) to a printed circuit board21is provided. The module may be, for example, a voltage regulator module, a memory module, interface card, or some other type of auxiliary card or daughter circuit card. As shown inFIG. 1, the connector20includes a housing22, a plurality of terminals24positioned within and extending from the housing22, and a plurality of solder masses26. The printed circuit board21includes a plurality of contact pad30aligned with the plurality of terminals24.

The housing22is formed of an insulative material and includes a pair of side walls32,34having opposite ends and a pair of end walls36,38provided at each end of the side walls32,34and generally perpendicular to the side walls32,34. An elongated slot40extends from the front edge of the end walls36,38and is generally parallel to the side walls32,34. The slot40receives an edge of the module. A plurality of inner walls42extend perpendicularly from the inner surfaces of the side walls32,34. Terminal receiving passageways44are thus formed between the inner walls42and between the inner surfaces of the side walls32,34.

The terminals24are mounted within the terminal receiving passageways44. The terminals24extend generally parallel to the end walls36,38. The terminals24are generally formed from metal, such as, for example, copper using a stamping process and then formed into the shape described herein. Alternatively the terminals can be formed from plastic which is then plated with a conductive material, such as metal.

A solder mass26is attached to each terminal24using the methods described herein. A first embodiment of the invention is shown inFIGS. 2-6. A second embodiment of the present invention is shown inFIGS. 7-8.

Attention is now invited toFIG. 2in which a terminal24is shown in greater detail. Each terminal24includes a central portion46, a contact portion48and a tail portion50. Each terminal24includes a proximal surface51aand a distal surface51b. A tip58is provided at the outer end of each contact portion48. The tip58is angled relative to the remainder of the contact portion48.

The central portion46of the terminal extends between the contact portion48and the tail portion50. The central portion46is generally elongated and includes outwardly protruding barbs52and recesses54for mounting the terminals24within the housing22. The central portion46is generally rectangularly-shaped proximate the contact portion48and is tapered proximate the tail portion50.

The tail portion50of each terminal24includes a generally tubular-shaped wall59having opposite first60and second62ends. A slit63is provided in the tubular-shaped wall59and extends from the first end60to the second end62. A generally cylindrically-shaped passageway64is defined by the interior surface of the wall59and extends from the first end60of the wall59to the second end62of the wall59.

A solder mass26is associated with each terminal24of the connector20. The solder mass26is a generally cylindrically shaped slug. The diameter of the solder mass26is approximately the same as the diameter of the passageway64of the tail portion50. The generally tubular portion can be formed either prior to the solder mass being inserted into the tubular portion, or the tubular portion can be formed around the solder mass.

Attention is now invited toFIG. 3in which a portion of the housing22is shown along with two terminals24. Assembly of the connector20includes mounting the terminals24within the housing22. Prior to mounting the terminals24within the housing22, a solder mass26is inserted within each terminal passageway64and is mechanically attached to the tail portion50of the terminal24. A reflow process is not used to attached the solder mass26to the terminal24. As shown inFIG. 3, mechanical attachment of the solder mass26within the passageway64results in the encapsulation of the solder mass26by the tail portion50of the terminal24.

As shown inFIGS. 4a-4ca variety of methods can be used to mechanically attach the solder mass26to the terminal24. One method of mechanically attaching the solder mass26and the terminal24shown inFIG. 4ais crimping. For example, the solder mass26and terminal24can be mechanically attached by placing the solder mass26within the passageway64and then crimping the wall59of the tail portion50and the solder mass26to retain the solder mass26within the passageway64. This will cause the wall59to deform59aand engage the solder mass26.

Another method of mechanically attaching the solder mass26and terminal24shown inFIG. 4bincludes providing a surface interruption61between the solder mass26and the terminal24. For example, at least one dimple61or barb is provided in the wall59When the solder mass26is placed within the passageway64the dimple on the wall59engages the solder mass26to retain the solder mass26within the passageway64.

Yet another method of mechanically attaching the solder mass26and terminal24shown inFIG. 4cincludes cold forming the solder mass26within the passageway64of the terminal24. The second end62is blocked by a removable member and solder is forced into the passageway64through the first end60. As the solder mass26is forced within the passageway64, the solder mass26expands outwardly and engagement is provided between the solder mass26and the wall59.

As shown inFIG. 5, to further enhance the attachment between the tail portion50of the terminal24and the solder mass26, subsequent to the mechanical attachment processes described above, a plating process can be used in which the assembled terminal24and solder mass26are simultaneously plated. Such plating63is typically performed with a metal, such as, for example, a precious metal, tin or lead. Alternatively, the solder mass26may be retained within the passageway64by nothing more than a plating material63.

After attachment of a solder mass26with each of the tail portions50of the terminals24, the terminals24are mounted within the housing22. The barbs52and the recesses54are engaged with corresponding structure within the housing22to secure the terminals24within the housing22.

Attention is now invited toFIG. 6. When the terminals24are mounted to the housing22, the contact portions48of the terminals24are located within the housing22such that a portion of each of the terminals24can contact the edge of a module which is inserted within the slot40. The tail portions50of the terminals24extend rearwardly of the housing22and are aligned with the contact pads30on the circuit board28.

To attach the connector20to the printed circuit board28, the tail portions50of the connector20are placed in contact with the contact pads30on the printed circuit board28. A reflow process is then performed, wherein the tail portions50of the terminals24, along with the solder masses26encapsulated therein, are heated until the solder mass26melts and a solder joint is formed between the tail portions50of the terminals24and the contact pads30of the printed circuit board28.

Mechanically attaching the solder masses26to the tail portions50of the terminals24eliminates the need for a reflow process for the purpose of attaching the solder mass26to the terminal24. Thus, a heating step is eliminated resulting in a more efficient manufacturing process. A reflow process is then used to fuse the solder masses26, terminals24and the contact pads30of the printed circuit board28.

The solder mass26provides a greater volume and mass of solder than that used to form a joint under the prior art methods which, for example, use a standard SMT foot. The encapsulated solder mass26, promotes the ability to provide a proper solder filet to obtain a more robust attachment and a more reliable joint between the connector20and the printed circuit board28. By plating the encapsulated solder mass26and terminal24the attachment between the solder mass26and terminal24can be further enhanced. Plating in this manner is particularly useful when the connectors are to be shipped as further protection is provided to the bond between the solder masses26and the terminals24.

Although the tail portions50of the terminals24have been shown and described as tubularly shaped and the solder masses26have been shown as cylindrically shaped, the tail portions50and the solder masses26can be shaped in any configuration which allows for mechanical engagement between the tail portions50and the solder mass26and the substantial encapsulation of the solder mass26, so long as a reflow process is not necessary.

A second embodiment of the present invention is shown inFIGS. 7aand7b. As shown inFIG. 7athe terminal124includes a central portion146and a tail portion150extending from the central portion146. Similar to the first embodiment shown inFIGS. 1-6, a plurality of terminals124are mounted within a housing to form a connector. The tail portion150of each terminal124is to be attached to a solder mass152, which will then be attached to the contact pads on a printed circuit board.

The terminal124is generally formed from metal, such as, for example, copper using a stamping process and then formed to the shape described herein. Alternatively, the terminal124is formed from plastic which is plated with a conductive material, such as a metal. The tail portion150of the terminal124includes two curved fingers154,156which extend from opposite sides of the terminal124. A surface158nearest the mounting surface28of the PCB21is formed by the finger154,156.

A bonding agent160, such as the bonding agent commonly referred to as sticky flux, is provided on the surface158of the tail portion150. The solder mass152, which is spherically shaped, is then brought into contact with the sticky flux160to securely attach the solder mass152to the tail portion150of the terminal124.

To attach the terminals to the printed circuit board, the solder mass152is placed in contact with the contact pads on the printed circuit board. A reflow process is then performed, wherein the tail portions150of the terminals124and the solder mass152are heated until the solder mass152melts and a solder joint is formed between the tail portions150of the terminals124and the contact pads of the printed circuit board.

Bonding the solder mass152to the tail portions150of the terminals124using sticky flux eliminates the need to use a reflow process at the time when the solder mass26is engaged to the tail150of the terminal124. As with the first embodiment described above, a heating step is eliminated and as a result the manufacturing process is more efficient than processes which require reflow in order to attach the solder mass152to the tail portion150of the terminals124.

Alternatively, rather than applying the sticky flux to the rear surface158of the tail portion150, the sticky flux can be pre-applied to the solder mass152. In the event that sticky flux is pre-applied to the solder mass152, the sticky flux must be activated prior to attaching the solder mass152to the tail portion150of the terminal. To activate the sticky flux, the temperature of the solder masses152is elevated and volatiles are driven off the solder masses152by tumbling and heating the solder masses152. Thereafter the solder mass152is placed in contact with the respective tail portion150of the terminals124and bonds thereto. Although activation of the sticky flux requires heat, the temperatures required to activate the sticky flux are lower than the temperatures required to perform the reflow process. Therefore, in the event solder masses with pre-applied sticky flux are used, an elevation of temperature, such as that required to perform reflow, is not required in order to bond the solder mass152with the terminal124. Thus, a more efficient manufacturing process results.

An example of an alternatively shaped terminal224of a connector made in accordance with a second embodiment of the present invention is shown inFIG. 7b. The terminal224includes a center portion246and a tail portion250. The tail portion250of the terminal225is hook shaped with a curved outer surface252and a curved inner surface254. Sticky flux260is applied to the inner surface254. A solder mass264is placed in contact with the sticky flux260and bonded to the tail portion250of the terminal224.

Two tail portions150,250have been shown and described with respect to the second embodiment of the present invention. The invention, however, allows the tail portion of the terminal to be shaped in any manner which allows for bonding of the solder mass using sticky flux. A sampling of different tail portions which could be used in connection with the present invention is shown inFIGS. 8a-8f. Likewise, although the solder masses152,264shown inFIGS. 7aand7bare each spherically shaped, the solder mass can be formed in essentially any shape. Preferably, the solder mass is formed in a shape which corresponds to the shape of the tail portion of the terminal with which it will be used. In addition, it is preferred that there is at least 25% surface engagement between the terminal and the solder mass.

To further enhance the attachment between the tail portions150of the terminals124and the solder mass152, or the tail portion250of the terminal224and the solder mass264, a plating process can be used in which the assembled terminal124and the solder mass152or the assembled terminal224and solder mass264are simultaneously plated. Such plating is typically performed with a metal, such as, for example, tin or lead.

As shown inFIG. 9, the method of attaching a terminal to a solder mass in accordance with the present invention begins with the step300of forming a terminal. Next, it must be determined if a mechanical attachment, plating attachment or a bonding attachment is to be used as represented by step302.

If a mechanical attachment is to be used the next step304is to mechanically attach the solder mass and the terminal. The mechanical attachment can be achieved in a variety of ways, such as, for example, using surface interruptions on the solder mass and the terminal, crimping the solder mass and the terminal, or cold forming the solder mass and the terminal. Each of these mechanical attachment methods has been described in detail above.

If a plating attachment is to be used, the next step305is to locate the solder mass proximate to the tail portion of the terminal. The tail portion and the solder mass are then plating in such a manner that the plating process retains the solder mass to the tail portion of the terminal.

If bonding attachment between the tail portion of the terminal and the solder mass is to be used, it must then be determined if a bonding agent has been pre-applied to the solder mass, as represented by step306inFIG. 9. If the bonding agent has not been pre-applied to the solder mass, the bonding agent is to be applied to the terminal, as represented by step308inFIG. 9. If a bonding agent has been pre-applied to the solder mass, the pre-applied bonding agent is to be activated, as represented by step310. The bonding agent is activated by, for example, tumbling and heating the solder mass. Subsequent to applying the bonding agent to the terminal or activating the bonding agent on the solder mass, the terminal and the solder mass are placed in contact with each other and thereby bonded together, as represented by step312.

After attachment (using either the mechanical or adhesive steps), it must be determined whether the attachment between the solder mass and the terminal will be enhanced by plating, as represented by step314. If the attachment is to be enhanced, the attached solder mass and terminal are plated, as represented by step316.

With the solder mass and terminal attached, the terminal and solder mass are mounted within the connector housing, as represented by step318. Finally, a reflow process is performed wherein the tail portions of the terminals are aligned with the contact pads on the circuit board and the solder mass and terminal are heated so as to melt the solder mass providing a bond between the tail portion of the terminal and the contact pad of the printed circuit board, as represented by step320ofFIG. 9.

While the terms up, down, forward, rearward and the like are used herein, it is to be understood that these terms are used for ease in describing the invention and do not denote a required orientation of the connector20when mounted to the printed circuit board28.

While preferred embodiments of the present invention are shown and described, it is envisioned that those skilled in the art may devise various modifications of the present invention without departing from the spirit and scope of the appended claims.