Low Profile Electrical Connector

The present invention relates to electrical connectors, and more particularly to electrical connectors used to interconnect electronic subassemblies, for example printed circuit boards, which are required to be mounted adjacent to each other often in a vertically stacked configuration.

Prior art methods are known for interconnecting electronic assemblies, particularly circuit boards. For example, it is well known to hard wire the boards together, or to use edge connectors carried by the boards which engage with complimentary fixed edge connectors carried within a frame in which the boards are mounted.

A concern with conventional board-to-board connectors is the limited space for connection of the boards or assemblies within the electronic device. With conventional connectors utilizing a plurality of terminals laterally arranged at intervals in a housing, one contact leg of each terminal is soldered to the circuit pattern of one printed board and the other leg of the contact is soldered to the circuit pattern on the other printed board. As a result of the narrow intervals between the terminals and vertical distance between the boards, it is extremely difficult to solder each of the terminals without bridging an adjacent terminal with solder. The soldering procedure is a time consuming and difficult task.

One suggested improvement is disclosed in the European patent specification Publication No. 0 463 487 published on Jan. 2, 1992. Therein, an electrical connector is described having a terminal housing with a plurality of terminals laterally arranged and fixed at regular intervals with two leg contacts of each terminal extending from the housing. A connector casing loosely accommodates the terminal housing and permits the terminal housing to slide up and down within the casing. The casing in turn has extensions for fixing it to one printed board and means to permit the printed board to come into contact with the other terminals. This device, however, requires an adequate space between the circuit boards to accommodate the connector casing and terminal housing. The minimum distance or height between adjacent circuit boards is thus unnecessarily limited, particularly in a stacked configuration of circuit boards.

The published PCT Application No. WO 97/02631 discloses an electrical connector for connecting adjacent circuit boards, including stacked circuit boards. The connector includes a generally I-shaped insulating body defining a plurality of adjacent recesses into which identical contact elements are mounted. The contact elements have at least one resilient contact arm that resiliently bends or moves within the body recess.

U.S. Pat. No. 5,041,016 and the European Patent Specification No. 0 346 206 disclose other types of printed circuit board connectors.

It is a principal object of the present invention to provide an improved electrical connector particularly suited for interconnecting stacked circuit boards.

Still a further object of the present invention is to provide an electrical connector having a relatively minimum height so as to interconnect vertically stacked circuit boards with a minimal separation distance therebetween.

Additional objects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.

In accordance with the objects and purposes of the invention, a low or "thin" profile electrical connector assembly is provided for interconnecting physically distinct circuit boards, particularly in a stacked configuration. The electrical connector includes at least one insulating body member having opposite ends and at least one longitudinally extending leg defined between the ends. It should be appreciated that a plurality of such legs may be provided. A plurality of adjacently disposed and spaced apart connector elements are disposed on each of the legs transverse to the longitudinal direction. Preferably, the connectors are disposed at distinct connector positions defined along the leg. For example, the connector positions may be grooves or recesses that are defined at least partly around a circumference of the leg. The grooves or recesses may further comprise engaging or positioning surfaces defined therein that are configured to retain and position each connector element at each connector position along the leg member.

The connector elements are generally open-ended or U-shaped and have a closed end and an open end defined by opposite arm members. The closed ends wrap around the leg at each connector position. Each connector element also includes an outwardly facing contact surface defined on each of the extending arms. In this manner, the connector is disposed between stacked circuit boards with the arms being in mating contact with respective pads of separate facing circuit boards.

Preferably, at least one of the arms of the connectors is an angled resilient arm disposed for pressing mating contact with a respective pad of one of the circuit boards. In this embodiment, the other connector arm may comprise a generally rigid arm that is disposed adjacent to an outer surface of the leg. Thus, the rigid arm may be soldered to its respective circuit board pad with the resilient arm being maintained in pressing contact with its respective pad without soldering. Alternatively, the resilient arm could also be soldered to its respective pad.

The resilient arm may be angled away from the leg and is preferably not in contact with the leg. The resilient arm does not derive its resiliency from being folded back onto the leg as this would limit the minimal height of the assembly due to additional bends in the connector elements. The resilient arm may also have a length so as to extend past, and even over, the longitudinal edge of the leg, for example within the groove or recess defined in the leg. It is preferred that the connector arms do not come into contact with each other.

In an alternative preferred embodiment, both of the connector arms may be resilient arm members disposed for pressing mating contact with respective pads of facing circuit boards. In this embodiment, the arms may move into grooves or recesses defined in the leg of the insulating body upon being pressed against mating pads of the facing circuit boards. The resilient arms may have a length so as to extend over the leg without contacting each other when in the pressed mating configuration to further limit the thickness or profile of the connector.

The connector may also include alignment structure defined on at least one of the ends of the insulating body. The alignment structure can comprise any manner of configuration so as to engage with complimenting structure on the circuit boards to precisely position the connector relative to the circuit boards. For example, the alignment structure may comprise one of a male or female member for engagement with a respective female or male member on the circuit board.

A principal concern of the present invention is to provide a connector having a minimal height or profile. In this regard, a preferred embodiment of the connector comprises a height or profile of less than about 1.0 mm between the opposite arms of the connector elements when the connector is in mating contact between facing circuit boards, and preferably between about 0.5 mm and 0.7 mm. The profile height of the connector is not, however, a limitation of the invention.

In order to aid in precise positioning of the connector element on the circuit boards, engaging structures, such as male or female members, may be defined on the body member so that a positioning cap or similar device may be used to grasp and precisely locate the connector element on a circuit board. This structure may also serve as positioning or alignment structure matable with complimenting structure on the circuit boards.

It should be appreciated that a plurality of connector assemblies according to the invention can be utilized in any number of configurations. For example, a plurality of the connector assemblies could be placed on a single placement cap for placement in any desired pattern on a circuit board.

The present connector assembly is not limited by any particular material of construction and, in this regard, any conventional suitable materials may be utilized in manufacture of the connector assembly components.

The invention will be described in greater detail below through preferred embodiments as illustrated in the attached figures.

FIG. 1 is a perspective view of one embodiment of an electrical connector according to the invention;

FIG. 2 is a perspective view of the underside of the connector shown in FIG. 1;

FIG. 3 is a perspective operational view of the connector indisposed between stacked circuit boards;

FIG. 4 is a view of one embodiment of a dual connector according to the invention;

FIG. 5a is a cross-sectional view of the connector assembly of FIG. 4 taken along the lines indicated;

FIG. 5b is a cross-sectional view of the connector assembly of FIG. 4 taken along the lines indicated in a mated configuration between opposing circuit boards;

FIG. 6 is an alternative view of a dual connector configuration shown with a placement device;

FIG. 7 is an underside view of the configuration shown in FIG. 6;

FIG. 8 is a cross-sectional view of the configuration of FIGS. 6 and 7;

FIG. 9 is a perspective view of an alternate dual connector configuration;

FIG. 10 is an enlarged underside view of the connector assembly shown in FIG. 9;

FIG. 11 is a partial perspective view of the connector assembly of FIG. 9 shown mated to a bottom circuit board; and

FIG. 12 is a cross-sectional view of the connector assembly of FIG. 9 shown mated between opposing circuit boards.

Reference will now be made in detail to the presently preferred embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, and not meant as a limitation of the invention. For example, features illustrated or described as part of one embodiment can be used on another embodiment to yield still a third embodiment. It is intended that the present invention include such modifications and variations as come within the scope and spirit of the present invention.

Exemplary preferred embodiments of a connector assembly, generally 10, according to the invention are illustrated in the figures. Connector assembly 10 is particularly useful in interconnecting oppositely facing conductive members, such as circuit boards, in a stacked configuration while minimizing the stack height between the conductive members. For ease of explanation and illustration, the conductive members are illustrated and referred to as circuit boards herein. However, this is not a limitation of the invention, and the connector assemblies 10 can be used to interconnect any conventional conductive members.

The connector assembly 10 is particularly useful when a minimal stack height between opposing circuit boards is desired. In this regard, in preferred embodiments, the connector assembly allows for stack heights of less than about 1.0 mm, and preferably between about 0.5 to 0.7 mm. Connector assembly 10 provides an efficient and secure device for interconnecting pads 14 of conventional facing circuit boards 12, as illustrated in FIG. 3, for example.

Although the invention will be described generally in terms of interconnecting circuit boards, and with reference to structure sufficient for connecting the circuit boards, it should be understood that the boards and connector assemblies 10 according to the invention may further be retained or secured in frame structure of whatever electrical component the elements are contained in. Such configurations are well understood by those skilled in the art and need not be described in great detail herein.

Connector assembly 10 includes at least one insulating body member 18 having opposite ends 20, 22, and at least one longitudinally extending leg 24 extending between ends 20, 22. Insulating body 18 may be formed of any suitable insulating material, for example a high temperature plastic material such as STANYL high temperature resistant nylon.

A plurality of adjacently disposed and spaced apart connector elements 34 are positioned along each longitudinal leg 24. Connector elements 34 will be described in greater detail below.

Connector elements 34 are secured to longitudinal leg 24 in any suitable manner. One preferred manner illustrated in the figures is to define adjacent grooves or recesses 28 along the length of longitudinal leg 24 and to locate connector elements 34 within grooves 28. For example, elements 34 may be simply press-fitted into grooves 28. In this regard, grooves 28 may preferably contain structure such as wedge recesses 30 defining a mating press-fit surface for wedge edges 32 defined on connector elements 34. Any suitable structure may be utilized in this regard for securely retaining connector elements 34 in position along the length of longitudinal leg 24. Also, grooves 28 are defined around at least a portion of the circumference of longitudinal length 24, and preferably around the entire circumference thereof so as to define a space for resilient arms of connector elements 34 to be depressed into when connector assembly 10 is in mating connection with opposing circuit boards, as described in greater detail below.

Connector elements 34 are formed of any conventional conducting material, for example a conventional copper alloy material having a thickness of about 0.1 mm. Each connector element 34 is generally U-shaped having an open end 38 and a closed end 36. The term "U-shape" is used generically to denote any shape having an open end and a closed end, including V-shapes, C-shapes, etc. Closed end 36 generally wraps around an edge 25 of longitudinal leg 24, preferably within grooves 28 as illustrated in the figures. As discussed above, connector elements 34 may be press-fitted into grooves 28, or otherwise secured to longitudinal leg 24.

Open end 38 of each connector element 34 is defined by extending arms 40. Each arm 40 comprises an outwardly facing contact surface 42 positioned and configured for mating contact with respective pads 14 of circuit boards 12. In the embodiment illustrated in FIGS. 1 through 5b, each arm 40 is a resilient arm designed for pressing mating contact with a respective pad 14. Arms 40 are not in contact with leg 24 along the resilient portion thereof and do not derive their resiliency from being folded back onto the arm. Each leg 40 also has a length so as to extend past or over longitudinal edge 27 of leg 24, as particularly illustrated in FIGS., 5a and 5b. The resilient arms may extend at an angle of generally less than 90.degree. from a horizontal plane through longitudinal leg 24. The resilient arms 40 are movable towards the leg into groove 28 upon being pressed against mating pads 14 of a circuit board 12 without contacting each other, as generally illustrated in FIG. 5b.

Referring to FIGS. 5a and 5b, upper resilient arm 40 includes a generally arcuate contact surface 42 defined by a radiused extension 44. Lower resilient arm 40 is defined also by a generally arcuate contact surface 42 and a generally horizontal extension 46. In the pressed mating configuration between circuit boards 12 illustrated in FIG. 5b, upper arm 40 is pressed into groove 28 and generally nest within lower arm 40, as illustrated in the figure. Arms 40 have enough resiliency so as to be in constant pressing contact against pads 14 without being soldered even when circuit board 12 rests against the upper surface 27 of each longitudinal leg 24, as particularly illustrated in FIG., 5b. Thus, the minimum stack height or vertical width of connector assembly 10 is generally defined by the upper and lower longitudinal surfaces of insulating body 18, and more particularly longitudinal legs 24. In this regard, arms 40 of connector elements 34 have a length so as generally extend over outward edge 27 of longitudinal leg 24 when in pressing mating contact with respective circuit boards 12, as illustrated in FIGS. 5a and 5b.

Each connector assembly 10 may also preferably include alignment structure to aid in precisely positioning the connector assembly relative to the circuit boards. For example, such structure may include male members 60 or female members 62 defined on opposite ends 22, 20 of body member 18. Male member 60 may be defined simply as a protruding member having a shape and configuration so as to engage in respective female structure 64 defined in circuit boards 12. Alternatively, female structure 62, which may be defined as a simple hole or recess, has a shape and configuration so as to engage with corresponding male structure defined on circuit boards 12. It should be appreciated by those skilled in the art that any manner of engaging structure can be utilized in this regard and that the embodiments illustrated in the figures are examples of but one suitable means.

Structure may also be provided to interconnect one or more of the connector assemblies 10. For example, referring to FIGS. 3 through 5b, single row connector assemblies 10 are shown connected to each other by way of the female/male engaging structure to define essentially a dual row connector assembly. In FIG. 3, the connected assembly is shown in phantom for sake of clarity. Two connected assemblies 10 are particularly illustrated in FIG. 4. The construction of each assembly 10 is the same, and such an assembly may be utilized for connecting dual rows of pads between facing circuit boards 12, such as illustrated in FIG. 3. It should thus be appreciated by those skilled in the art that any configuration of connected assemblies 10 may be utilized in this regard.

An alternative configuration of a dual row connector assembly is illustrated particularly in FIGS. 9 through 12. In this configuration, body member 18 includes two longitudinally extending legs 24 defined between ends 20, 22. The configuration of connectors 34 along each leg 24 may be as described above with regards to opposite resilient legs 40. In this embodiment, engaging structure is defined on ends 22 in the form of male protruding members 60. It should be understood that any configuration of engaging structures may be utilized in this regard. For example, the engaging structure could be defined as female receiving structures for mating engaging with male structures on the circuit boards.

The embodiment of the connector assemblies illustrated in FIGS. 1 through 5b may be considered as a "solder-less" connector assembly since both of the contact surfaces 42 are defined on resilient arms that remain in pressing mating contact against pads 14 without the necessity of soldering each individual element 34 to pads 14. The resiliency of arms 40 ensures that connector elements 34 remain electrically connected to pads 14. However, in an alternative embodiment illustrated for example in FIGS. 9 through 12, connector elements 34 may include at least one generally rigid arm 48 defining a contact surface 42 at the end thereof. Rigid arm 48 is generally straight and rigidly set against a surface of longitudinal leg 24, for example within groove 28 so as to protrude just slightly above the outer surface of leg 24. In this regard, engaging structure may be defined for retaining rigid arm 48 relative to longitudinal leg 24. Referring to FIG. 10, this structure may include retaining recesses 50 defined generally at the end of each groove 28 for press-fitting contact with complimenting press-fit surfaces 52 defined on each connector element 34. In this embodiment, as illustrated in FIGS. 11 and 12, bottom rigid arms 48 are set on pads 14 of a bottom circuit board 12 and are conventionally soldered with solder 16 thereto. Thus, in this configuration, connector assembly 10 is permanently secured to at last one of the circuit boards.

The embodiments of FIGS. 9 through 12 illustrate the upper connector arm of each connector element 34 as a resilient arm 40, which operates as discussed above. However, it should be appreciated that each of the arms of connector elements 34 may actually comprise rigid arm members as discussed herein.

FIGS. 6 through 8 illustrate an alternative configuration of a dual connector assembly according to the invention, and also a conventional method of positioning the connector assemblies relative to the circuit boards. FIGS. 6 and 7 illustrate two connector assemblies 10 releasably mounted onto a placement cap device 66. Cap device 66 has a general profile corresponding to the ends and longitudinal leg 24 of insulating body member 18. Each connector assembly 10 includes female engaging structure 62 for releasably engaging with male structure 61 defined on the underside of placement cap 66. In this regard, placement cap 66 includes end sections 67 spanning across each of the connector assemblies 10 with dual engaging members 61 defined on the underside thereof for engagement with each of the connector assemblies 10, as illustrated particularly in FIG. 7. A central section 69 extends between ends 67. Spacing nubs 70 are defined on the underside of ends 67 to maintain a separation between the ends of insulating body members 18 and the placement cap 66.

As generally known in the art, a suction nozzle or device attaches to placement cap 66 on the upper surface thereof and is used to precisely position connector assemblies 10 relative to the circuit boards. The placement cap 66 maintains connector assemblies 10 in position as bottom legs 48 soldered to their respective pads 14 on a lower circuit board 12, as generally illustrated in FIG. 12. Once connector assemblies 10 have been soldered in place, placement cap 66 can be removed simply by pulling the cap off of connector assemblies 10 and lower circuit board 12. The upper circuit board 12 is maintained in pressing mating contact against resilient arms 40 of the connector assemblies 10. Thus, in this embodiment, it is not necessary that engaging structure be defined between connector assembly 10 and the respective circuit board 12, although such structure could certainly be utilized.

It should be appreciated by those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope and spirit of the invention. For example, features illustrated as part of one embodiment can be used on another embodiment to yield still further embodiments. Such modifications and variations are within the scope and spirit of the invention and appended claims.