ELECTRICAL CONNECTOR ASSEMBLY AND METHOD OF FORMING SAME

Abstract: A connector assembly (10) includes a stacked linear array of an alternating sequence of terminals (12) and resiliently compressible insulator portions (14). The array is linearly compressed in an accordian-­ like fashion and is inserted in a housing (24) having a cavity of length less than the uncompressed length of the array. The array is inserted in the housing and allowed to expand against opposing walls (26) of the housing thereby maintaining the terminals in a self-compensating floating arrangement. A method for forming the connector assembly includes the steps of arranging resiliently compressible dielectric material (14) between terminals (12) to form a stacked linear array, linearly compressing the stacked linear array in an accordian-like fashion, inserting the compressed array in a housing (24), and thereafter maintaining the array in linear compression within the housing.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention pertains to multi-circuit electrical connector arrangements which are mounted to an electronic device such as a printed circuit board, connector plug, or connector receptacle and extends to methods of forming such connectors. 2. Description of the Prior Art Multi-circuit electrical connectors of the type adapted for mounting on a printed circuit board or the like typically include a plurality of electrical terminals disposed within a unitary dielectric housing. Such housings typically totally surround the terminals, and provide inter-terminal barriers of insulation material. Difficulties in maintaining the pitch or center-line spacing of terminals has been encountered with increasing connector miniaturization. Difficulties in pitch control arise because of the inherent physical properties of the inter-terminal dielectric material of which the housings are made. For example, it is well known that many plastics tend to swell somewhat with increasing humidity. Also, thicknesses of the metal stock from which terminals are formed can vary slightly from terminal to terminal. These and other like processes tend to deteriorate the dimensional tolerance of connector assemblies. Nonetheless, there is an increasing need to reduce the pitch or centerline spacing of electrical connector assemblies, including not only assemblies mounted on a printed circuit board, but also the connector assemblies found in connector plugs, connector receptacles, and other electronic devices. Other difficulties have been encountered in providing connector arrangements for liquid crystal displays and the like. A liquid crystal display is typically a thin wafer-like electronic package encapsulated in glass. Because of its essentially two-dimensional configuration (i.e. its relatively thin construction), and because displays are elongated along a direction parallel to the mounted surface, it is difficult to provide effective simultaneous electrical connection with all segments of the display, while preventing stressing of the display which would cause the glass package to crack. One arrangement typically provided for overcoming these difficulties is popularly known in the art as a "Zebra strip". An example of this connector arrangement is shown in United States Patent No. 4,008,300 issued to Timothy Ponn. A method of producing this connector arrangement includes the steps of taking a dielectric sheet of resilient material such as natural or synthetic non-conductive rubber, and cutting the sheet to form a gasket-like frame against which the display is pressed. The cut frame is perforated with a series of holes for receiving discrete rod-like portions of resilient conductive material. The conductive material is in effect pressed into or otherwise formed within the dielectric rubber sheet. The display, when pressed against the dielectric sheet, is brought into intimate contact with the resilient conductive portions. Electrical leads of the display can conveniently be brought to an outside mating surface so as to be maintained in pressed engagement with the resilient conductive portions. A very similar arrangement is shown in DE-A-3224668 which discloses a number of compressible alternate conducting and insulating segments for providing electrical connection between two sets of contacts. A convenient method for forming the conductive portions is to fill the holes with a slurry of electrically conductive material which is then allowed to cure, with constriction of the holes applying sufficient radial force to the resilient conductor portions to cause them to bulge outwardly beyond the surfaces of the dielectric rubber sheet. Such arrangements are, however, limited to compressive engagement with coextensive planar electronic devices. The object of the present invention is to provide for better pitch control of terminals in connectors which may be of greatly reduced size and greatly reduced terminal centerline spacing. From one aspect the present invention provides a connector assembly adapted to mate electrically with an electronic device having closely spaced circuits comprising a generally linear terminal array having a plurality of spaced-apart terminals with dielectric means disposed to provide insulation between adjacent terminals, said dielectric means being a pitch controlling amount of a resiliently compressible dielectric material between adjacent sides of the terminals so that the terminal array is resiliently compressible in an accordian-like fashion, and characterised in that the terminals are metal terminals and each terminal has a portion adapted to mate with a corresponding one of said closely packed circuits and further characterised by housing means including a generally elongated terminal receiving cavity having a length less than the uncompressed length of the array for mounting said array in linear compression; whereby the spacings between the terminals are self-compensating to allow for alignment with said circuits. The present invention further provides a method of forming a connector assembly for mating electrically to an electronic device having closely spaced circuits, the connector assembly including a plurality of spaced-apart metal terminals, each having a portion adapted to mate with a corresponding one of said closely spaced circuits, the method being characterized by the steps of disposing a pitch controlling amount of a resiliently compressible dielectric means adjacent each terminal so that, when the terminals are stacked, insulation is provided between adjacent terminals, arranging the terminals in a stacked generally linear array, linearly compressing the stacked array in an accordian-like fashion, inserting the compressed array in a housing, and maintaining the array in linear compression in said housing, whereby the spacings between the terminals are self-compensating to allow for alignment with said circuits. Some ways of carrying out the present invention in both its apparatus and method aspects will now be described in detail by way of example with reference to drawings. BRIEF DESCRIPTION OF THE DRAWINGS In the drawings, wherein like elements are rerferenced alike, FIG. 1 is an exploded perspective view of a connector assembly of the present invention, shown mounted to a printed circuit board; FIGS. 2a to 2d show the assembly of the connector of Figure 1 wherein Figures 2a and 2b show two different stacks of terminals having different thicknesses, Figure 2c shows the assembly of one of the terminal stacks within a housing, and Figure 2d shows the completed connector assembly mounted on a printed circuit board; FIG. 3 shows an exploded perspective view of a modular telephone plug constructed in accordance with the present invention; FIG. 4 is an exploded perspective view of a receptacle connector constructed in accordance with the present invention; FIGS. 5a to 5c show three different terminals ready for assembly in a connector assembly according to the present invention; FIG. 6 shows a stacked terminal assembly according to the present invention, utilizing terminals similar to those shown in Figure 5c; FIG. 7 is an elevational view of an improperly-formed stacked assembly of Figure 6 showing, in exaggerated form, fan-out misalignment of that assembly; FIG. 8 is a plan view of the assembly of Figure 6; FIG. 9 shows a plan view of two connector assemblies of the present invention, each having terminals of different thicknesses, illustrating the pitch control of terminals provided by the present invention; FIG. 10 is a schematic plan view of a work station for assembling a connector stack by a method according to the present invention; and FIG. 11 is an elevation view of Figure 10. DETAILED DESCRIPTION WITH REFERENCE TO THE DRAWINGS Referring now to the drawings, and especially to Figures 1 and 2, an electrical connector assembly according to the present invention is indicated generally at 10. Assembly 10 includes a generally linear array of spaced-apart metallic terminals 12 with layers of insulation 14 disposed between the terminals. Each terminal 12 has a generally C-shaped mating portion 16 adapted to mate with an edge of a printed circuit board, a board-engaging body portion 18 and a soldertail 20. Insulation 14 disposed between adjacent terminals is comprised of a resiliently compressible material such as rubber. The material of insulation 14 is of a type which is compressible at least 20% of its bulk, so as to exhibit both an outwardly directed spring bias force, and a spring resistance to further inward compression. The generally linear array of terminals 12 and insulation portions 14 is linearly compressed in the direction of arrows 22, in an accordian-like fashion, and inserted in a frame-like housing 24. Thereafter the array is allowed to expand in an outward direction against opposing walls 26 of housing 24. Housing 24 is dimensioned to maintain the array in partial linear compression so that insulator portions 14 bias terminals 12 for spring loaded, floating mounting. Housing 24 may include inwardly extending collar portions 28 which constrain the terminal body portions 18 against upward movement once installed in the housing. Also included in housing 24 are board-receiving slots 30 which co-operate with terminal mating portions 16 to receive an edge of a printed circuit board, as is known in the art. Thereafter, the connector assembly 10 is advanced toward printed circuit board 32 such that mounting ears 34 of housing 24 are received in corresponding apertures 36 formed in board 32. Concurrently therewith, the soldertails 20 are received in corresponding apertures 37 where they are brought in close proximity with circuits or electrical traces 38 formed on the underside 39 of board 32 (see Figure 2d). Referring now to Figure 2, assembly of connector arrangement 10 will be described in greater detail. Figures 2a and 2b show two alternative stacked arrays of terminals 12 and insulation layers 14. The terminals 12 of Figure 2a are formed from slightly thicker metal stock than those of Figure 2b, the different thickness being exaggerated for the purposes of illustration. In contrast, the terminals 12 of Figure 2b are formed from thinner stock. Either array, that of Figure 2a or of Figure 2b, may be encountered in a production environment. In either event, the array is linearly compressed to a final length La shown at the top of Figure 2c. The compressed array is inserted in housing 24, and allowed to expand against housing walls 26, which are spaced a distance Lh apart from each other. The final length Lh of the array is slightly larger than length La, but is significantly less than its uncompressed length by an amount which ensures at least 20% compression of the bulk of each insulator layer 14 to provide the required resilience for floating terminal mounting and automatic centerline self-compensation. The length Lh of the housing 24 is carefully controlled to match the total length of the array of circuits 38 to which the terminals must be mated. The same housing 24 would be used for either array of Figure 2a or Figure 3b, even though the uncompressed lengths of those arrays may differ. As will now become apparent, the terminals 12 of either array of Figure 2a or 2b are mounted in a "floating" arrangement, owing to the resiliently compressible material 14. As will be explained in greater detail herein, the connector assembly being described provides a self-compensating alignment of terminals, which automatically adjusts for differences in manufacturing tolerances of terminal stock, insulation stock, or the dimensions of housing 24. Housing 24 is configured to overlie circuit traces 38 in a predetermined alignment therewith, when mounting ears 34 are received in apertures 36. The resulting arrangement of Figure 2d is ready for a soldered mating of terminal soldertails 20 to the circuits 38 of printed circuit board 32. Once terminals 12 are soldered in place, the resilient material 14 is relied upon to electrically isolate adjacent terminals 12 from each other. With reference now to Figure 3, the present invention is directed not only to connector assemblies for printed circuit boards, but also to connector assemblies for other electrical devices. For example, the electrical device shown in Figure 3 comprises an electrical plug connector generally indicated at 44. The plug connector accepts a multiconductor cable 46 containing a plurality of circuits in the form of insulation-clad electrical conductors 48. As before, terminals 50 are spaced apart in a linear array by resiliently compressible insulator portions 52. Terminals 50 are of a type known in the modular telephone connector art, and include insulation piercing tips 53 for penetrating the insulation of conductors 48. Connector 44 includes a housing 54 formed of molded dielectric material. Housing 54 includes a frame-like portion 56 overlying the circuits or conductors 48, of cable 46. The array of terminals 50 and insulator portions 52 is linearly compressed, and inserted into the frame-like portion 56, in a manner similar to that illustrated in Figure 2. The frame portion 56 of housing 54 may be of sufficient array-receiving depth to allow the terminals 50 of the array to be received between opposing frame walls, before insulation piercing portions 53 are driven into insulation-clad conductors 48 (whereupon terminals 50 will be fixed in position, unable to float). If this extra depth cannot be provided in frame 56, then application tooling must be provided to linearly compress the array, and hold the array in linear compression as insulating piercing tips 53 are driven into conductors 48. Terminals 50 will be free to float within the application tooling prior to termination to conductors 48, it being understood that the application tooling must, in part, consist of a frame similar to the frame 56 of housing 54. Referring now to Figure 4, a further embodiment of a plug connector according to the present invention is indicated generally at 58. The connector arrangement includes a plurality of spaced-apart terminals 60 spaced apart by resiliently compressible material 62 disposed between each terminal. Terminals 60 include a forward mating portion 64 and a body portion 66. Mating portion 64 is of a type providing a downwardly directed spring bias force for mating with the edge of a printed circuit board, flat flexible cable, or a flag-type terminal. The array of terminals 60 and insulators 62 is, as explained before, linearly compressed and inserted in a dielectric housing 68. A frame-like portion 70 of housing 68 is provided to receive the compressed array. Terminals 60 are adapted to mate with circuits disposed within housing 68. For example, housing 68 can be made to accept a cable 72, similar to the cable 46 described with reference to Figure 3. Cable 72 includes a plurality of individual circuit conductors 74. The rearward ends of terminals 60 conveniently include piercing tips 76 which provide axial penetration of conductor 74, as the array is inserted in housing 68. Other electrical mating arrangements between terminals 60 and circuits carried within housing 68 will become apparent to those skilled in the art upon study of the description herein. In each of the several embodiments discussed above, the linear array of terminals and resiliently compressible insulator portions is linearly compressed to a foreshortened length to allow insertion in a frame-like housing. In each embodiment, the terminals are free to float when installed in the frame-like housing, owing to the compressible resilience of the insulator material. Referring now to Figures 5a to 5c , three different terminals 80, 82, 84 respectively are shown. The terminal 80 is of the surface mount type, having an engaging surface 81 adapted for soldered surface mounting to a conductive pad 83 affixed to the surface of substrate 85. Figures 5a to 5c illustrate alternative configurations of resiliently compressible insulation material 86 provided between terminals. In each of the figures, the terminals are assumed to be of equal thickness throughout their cross section. The centroid, or center of each cross-sectional area of each terminal can be mathematically computed, and is shown in its approximate position by the reference letter "C". The resiliently compressible material 86 is applied to each terminal such that, upon linear compression in a stacked array (as explained above with reference to Figure 2), the net forces applied to each terminal will be balanced about the centroid "C" of the terminal cross-section. This is achieved in a variety of ways, the diversity of which is illustrated in the different Figures 5a to 5c. For example, referring to Figure 6, terminals similar to those of Figure 5c are shown in a stacked linear array. If the forces are not balanced about the cross-sectional centroid "C" of each terminal 84, a fan-out misalignment of terminals 84 will result, as shown in the elevation view of Figure 7. The misalignment is shown in a vertical plane in Figure 7, it being understood that misalignment can also occur in a perpendicular, i.e. horizontal, plane when insulation material 86 is improperly applied in an unbalanced fashion. However, centroid balancing can be readily achieved, such that horizontal fan-out misalignment does not occur, as shown in the plan view of Figure 8. In Figures 6 to 8, the line 88 lies along the cross-section centroid "C" of each terminal 84 of the linear array. Referring now to Figure 9, the self-compensating, or self-centering feature will be described in greater detail. Figure 9 is a plan view of a housing 92 having two frame-like array-receiving recesses 94, 96 respectively. An array of terminals 98 and resiliently compressible insulator portions 100 is shown in the upper portion of Figure 9, installed in recess 94. Similarly, a linear array of terminals 102 and resiliently compressible insulator portions 104 is shown installed in lower recess 96. Recesses 94, 96 are similarly dimensioned, but the terminals 102 are (shown to an exaggerated degree) wider or thicker than the terminals 98, by an amount "d". As a result, the resiliently compressible insulators 104 are compressed to a greater extent than insulators 100. For convenience in further description, the array of terminals and insulators mounted in recess 94 will be designated by the numeral 106 while the array mounted in recess 96 will be designated by the numeral 108. In the particular arrangement shown in Figure 9, insulator portions are not provided at the ends of the several arrays 106, 108. Consequently, the outside end surfaces of each stacked array 106, 108 will be precisely aligned with each other. Due to the difference in thickness "d" between terminals 98, 102, the centerline positions of the end terminals will not be colinearly aligned. However, misalignment will not be as great as the full thickness difference "d". In fact, the difference in centerline positions of end terminals is of thickness 1/2d. When an odd number of terminals are provided in a given linear stacked array, the centerline positions of the central terminals will also be colinearly aligned regardless of variation in terminal thicknesses or insulator thicknesses. The remaining ("intermediate") terminals of an array will have their centerline positions displaced or offset by a fraction of the thickness difference "d". For example, in the five terminal arrangements shown in Figure 9, the centerline offsets of the "intermediate" terminals (those not at the end or the center of a stacked linear array) will be offset by the difference one-fourth d. If eleven terminals were provided the offset difference of intermediate terminal centerlines would be offset one-tenth d. Thus, the center or central terminals would always be identically placed, the end terminals would be offset at most by a distance 1/2 d, and the remaining intermediate terminals would have an average centerline offset significantly smaller than the assumed difference d--that is, the remaining 1/2 d offset is spread out or averaged over the number of intermediate terminals. The same averaging principle applies to even quantities of terminals. Refering now to Figure 10, an arrangement for forming a connector assembly of the present invention by a method according to the present invention is generally indicated at 112. Work station 112 includes a first feed track 114 for the terminals 12, which are conveniently stamped from a unitary metal blank, being formed in an end-to-end reelable configuration as shown in the elevation view of Figure 11. Similarly, work station 112 includes a second feed track 116 for supplying a plurality of insulator portions 14 which are conveniently provided by stamping an integral blank of resiliently compressible material to produce insulator portions 14 arranged end-to-end in a reelable configuration. Cutting blades not shown in the figure are provided at each feed track to sever individual terminals 12 and individual insulator portions 14. Upon severing, an individual terminal 12 is inserted in a generally U-shaped forming track 118 (see Figure 10) where it is pushed by plunger 120 against a stop wall 122 formed at the bight of the forming track 118. Thereafter, an individual insulator portion 14 is formed, and introduced into forming track 118. Plunger 120 pushes the insulator portion 14 against the previously-formed terminal 12. In this manner, a linear array of terminals 12 and insulator portions 14 is conveniently stacked in forming track 118. The stacked linear array can thereafter be relocated to an insertion station where it is loaded in one of the aforedescribed frame-like housings. If desired, a stripe of binder material such as varnish can be applied across a stacked array in the direction of stroke of plunger 120 to hold the array together as a free standing, but freely compressible assembly, it being understood that the binder material would not impede the linear compression of insulator portions in their final application. As shown in Figures 10 and 11, it is preferred that the sequential succession of terminals is preserved in the resulting stacked linear array, and likewise the sequential succession of insulator portions 14 is also preserved within that array. This ensures a minimum offset in centerline terminal positions, due to variations in the blank material from which the terminals and/or insulating portions 14 are formed. There has been described multi-circuit electrical connector assemblies which compensate for changes in thicknesses of terminal members to provide a self-compensating centerline spacing, thereby to maintain a centerline spacing over a range of terminal thicknesses. The electrical connector assemblies of improved centerline spacing can be incorporated in an electrical connector housing, such as that of an electrical connector plug or connector receptacle.

Claims: A connector assembly (22, 24) adapted to mate electrically with an electronic device (32) having closely spaced circuits comprising a generally linear terminal array having a plurality of spaced-apart terminals (12) with dielectric means (14) disposed to provide insulation between adjacent terminals, said dielectric means being a pitch controlling amount of a resiliently compressible dielectric material between adjacent sides of the terminals so that the terminal array is resiliently compressible in an accordian-like fashion, and characterised in that the terminals (12) are metal terminals and each terminal has a portion adapted to mate with a corresponding one of said closely packed circuits, and a housing means (24) includes a generally elongated terminal receiving cavity having a length less than the uncompressed length of the array for mounting said array in linear compression; whereby the spacings between the terminals are selfcompensating to allow for alignment with said circuits. The assembly of claim 1 further comprising means (34) for mounting said housing to the electronic device (32) so as to overlie said circuits in a predetermined alignment therewith. The assembly of claim 2 wherein the electronic device is a printed circuit board (32) having circuits comprising soldertail-receiving apertures (37) and circuit traces (38) formed in said printed circuit board, said mating terminal portions comprising soldertails (20) to be received through the circuit board apertures and electrically mated with said printed circuit board traces. The assembly of claim 2 wherein the electronic device is a printed circuit board (85) having circuits comprising conductive pads (83) mounted to the surface of said printed circuit board, said mating terminal portions comprising a mounting surface (81) to engage said conductive pads. The assembly of claim 1 wherein said housing comprises a terminal receiving recess (56) formed in an insulator member overlying said circuits. The assembly of claim 5 wherein said insulator member comprises a connector housing adapted to receive said circuits in the form of insulation-clad electrical wires (46) disposed in said housing, and said terminal mating portions comprise insulation penetrating portions (53) adapted to penetrate said wire insulation and make contact with said electrical wires. A method of forming a connector assembly for mating electrically to an electronic device having closely spaced circuits, the connector assembly including a plurality of spaced-apart metal terminals, each having a portion adapted to mate with a corresponding one of said closely spaced circuits, the method being characterized by the steps of disposing a pitch controlling amount of a resiliently compressible dielectric means adjacent each terminal so that, when the terminals are stacked, insulation is provided between adjacent terminals, arranging the terminals in a stacked generally linear array, linearly compressing the stacked array in an accordian-like fashion; inserting the compressed array in a housing; and maintaining the array in linear compression in said housing; whereby the spacings between the terminals are self-compensating to allow for alignment with said circuits. The method of claim 7 wherein said step of arranging said terminals in a generally linear array comprises the steps of forming a continuous sequential succession of terminals from a metal blank, forming a continuous sequential succession of resiliently compressible dielectric members from a dielectric body and maintaining the sequences of said terminals and said dielectric members while interleaving said terminals and said dielectric members in a stacked linear array. The method of claim 8 wherein said terminal forming step and said dielectric member forming step each comprises the step of forming said terminals and said dielectric members in end-to-end continuous sequences from unitary metal and dielectric blanks, and severing the formed blanks to form discrete terminals and dielectric members respectively. The method of claim 7, 8 or 9 further comprising the step of coating said stacked linear array with a binder material to form a free standing compressible assembly. The method of claim 7, 8, 9 or 10 further comprising the step of mounting said housing to said device so as to overlie said circuits in a predetermined alignment therewith. The method of claim 7, 8, 9, 10 or 11 wherein the step of maintaining the array in linear compression while in said housing comprises the step of providing a housing having a generally elongated terminal receiving cavity with a length less than the uncompressed length of the array, and allowing the array to partially expand against the housing after being inserted therein.

Inventors: STIPANUK, JOHN, WALSE, ALAN S.
Applicants: MOLEX INCORPORATED
Application year: 1986
Main classification: H01R43
IPC codes: H01R12, H01R24, H01R43