Shielded and wireless connector for electronics

Abstract: This invention provides shielded and wireless connectors for interconnecting electronic circuit boards that are stacked in metal carriers. Serial interconnectors through the carriers provide transmission line paths through the stacked layers through connector assemblies embedded in and fed through each carrier in collinear alignment with each other. Each of the embedded feed through connector assemblies has upper and lower button connectors interconnected by a metal conductor, all positions within an axial hole formed by a pair of substantially cylindrical dielectric inserts. The upper and lower button connectors protrude from the upper and lower surfaces of the upper and lower adjacent circuit boards, respectively. This invention provides connector assemblies having the ability to withstand very high inertial forces without degradation of the electrical contact with the metal pads of the respective circuit boards.

Description: This invention relates to shielded and wireless connectors for interconnecting individual electronic card assemblies. More particularly, this invention relates to card assemblies interconnections which allow signals of one assembly to be isolated from signals of other assemblies and any other signal going to or from that assembly. Surface mount and hybrid component technologies currently permit very high density individual electronic circuit board designs. Further, multilayer electronic circuit board technologies currently permit high frequency analog signals to be isolated from digital signals through the appropriate allocation of individual processing functions and/or electrical signals to individual layers of a multilayer board. Specifically, internal metallized layers within the circuit board are often used to isolate high frequency analog or digital signals of one layer from signals of another layer. Unfortunately, the level of manufacturing technology presently available limits multilayer circuit board designs to approximately 10 to 12 layers. Thus, in many complex electronic systems, 10 to 12 layers are insufficient to allow high frequency analog and digital signals to be constrained to the layers of the multilayer circuit board. Several individual multilayer circuit boards must therefore be employed, in which high frequency analog signals are limited to some boards and digital signals limited to other boards. However, these individual circuit boards must then be interconnected to each other. Typically, interconnection of individual circuit boards is accomplished using chassis-mounted circuit card connectors and cables (or wires). Alternatively, circuit card connectors may be mounted onto a printed circuit mother board allowing printed circuit daughter boards to be plugged into the connectors. As determined by the printed circuit on the mother board, each daughter board may be interconnected to adjacent daughter boards or to distant daughter boards loca-ted several connectors away. In either arrangement, the long interconnections between individual circuit boards reduce system electrical performance by introducing timing and phase shift errors and by compromising the isolation of high frequency analog signals from digital signals. U.S. Patents 4,710,133 and 4,806,110 disclose related types of electrical mother and daughter board edge connectors designed to minimize interference between circuit board signals and extraneous signals. U.S. Patent 5,007,843 discloses another type of edge connector which employs connector elements each composed of a strand of metal wire wadded together to form a "button" of wadded wire. U.S. Patent 5,007,843 also discloses a circuit board cable harness which employs button connector elements. Finally, as shown in U.S. Patent 4,992,053 on which the preamble of claim 1 is based, improved interconnection of circuit boards has been proposed through the use of a plurality of button connector assemblies, each comprising a pair of button connector elements positioned on opposing ends of a metal slug, with the button connector elements and the slug being positioned within a hole in a block of insulative material and with the circuit boards being bolted about the insulative material. In addition to signal isolation concerns, systems incorporating interconnecting signal wires or mother and daughter board arrangements, such as those discussed above, are difficult to design for very high inertial applications. Specifically, the interconnecting wires and mother and daughter boards flex under the high inertial acceleration and are therefore subject to failure. Furthermore, metal covers that are often employed to shield individual circuit boards, also flex under the same conditions and are therefore also subject to similar failures. In view of the foregoing, there presently exists a need for a shielded and wireless interconnection of individual circuit boards. There also exists a need for such shielded and wireless interconnection of circuit boards that is capable of withstanding very high inertial environments. This invention provides an apparatus which overcomes the aforementioned inadequacies of the prior art connectors and provides an improvement which is a significant contribution to the advancement of the circuit board interconnection art. This invention comprises a shielded and wireless interconnecting system for electronic circuit boards as defined by the features of claim 1. More particularly, the invention comprises a plurality of stacked layers, each layer comprising a circuit board mounted to a metal carrier. Each metal carrier comprises an upper recess for receiving the circuit board and a lower recess for receiving the electrical components of its lower adjacent circuit board positioned within the upper recess of the lower adjacent carrier. In this stacked arrangement, each circuit board is fully enclosed within the recesses of the adjacent metal carriers. Thus, signals of one circuit board are isolated from signals of its adjacent (and distant) circuit boards. The serial interconnections through the carriers form transmission line paths through the stacked layers. Each serial interconnection is accomplished by means of connector assemblies which are embedded within and feed-through each carrier in collinear alignment with each other. Each of the embedded feed-through connector assemblies comprises upper and lower button connectors interconnected by a metal conductor, all positioned within an axial hole formed by a pair of substantially cylindrical dielectric inserts. The upper and lower button connectors protrude from the upper and lower surfaces of the carrier to electrically contact metal pads on the lower and upper surfaces of the upper and lower adjacent circuit boards, respectively. Importantly, the aligned metal pads on the upper and lower surfaces of each circuit board may be electrically connected to each other by means of a plated-through-hole. In this manner, serial interconnection with adjacent and distant circuit boards is easily accomplished. Moreover, the metal pads on the surfaces of a circuit board may be electrically connected by internal or external circuit traces to its circuit board. It should be readily appreciated that the embedded feed-through connector assemblies are fully shielded by the metal carrier in which they are embedded. Most importantly, the impedance of the dielectric inserts of each aligned connector assemblies may be selected so as to achieve an optimal impedance for that serial interconnection, much in the same manner of selecting the optimal impedance of a transmission line. Another feature of the shielded and wireless interconnection of the invention which utilizes metal carriers, is the ability to survive very high levels of shock and/or acceleration in excess of 1000 times the force of gravity. Specifically, the layers of circuit boards and metal carriers in a sandwiched, stacked configuration are capable of withstanding very high inertial forces, such as those experienced in cannon-launched applications. Moreover, the embedded feed-through connector assemblies are specifically designed so as to also survive very high levels of shock and/or acceleration without degrading their electrical contact with the metal pads of the respective circuit boards. The foregoing has outlined rather broadly the more pertinent and important features of the present invention in order that the detailed description of the invention that follows may be better understood so that the present contribution to the art can be more fully appreciated. Additional features of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings in which: Fig. 1 is a diametrical cross-sectional view of the circuit board interconnect apparatus of the invention employed within a cannon-launched projectile; Fig. 2 is a partial enlarged view of Fig. 1, partially exploded, illustrating two circuit boards enclosed by adjacent metal carriers and illustrating a transmission line path formed by embedded feed-through connector assemblies; Fig. 3A is a top plan view of a metal carrier employing transmission line paths positioned in inner and outer circles and Fig. 3B is a diametrical cross-sectional view of Fig. 3A; Fig. 4 is a diametrical cross-sectional view showing how heat energy is transferred from high powered components into the carrier for thermal management; and Fig. 5 is a diametrical cross-sectional view of another embodiment of a connector assembly. Similar reference characters refer to similar parts throughout the several views of the drawings. As shown in Figs. 1 and 2, the shielded and wireless interconnect apparatus 10 of the invention comprises a plurality of stacked layers 12, each layer 12 comprising a circuit board 14 mounted to a metal carrier 16. A plurality of connector assemblies, generally indicated by numeral 18, are embedded within the metal carrier 16 to protrude therefrom and interconnect its circuit board 14 with the circuit board 14 of the adjacent layer 12. More particularly, each metal carrier 16 comprises an upper recess 20 defined by upstanding retaining edge 22 and a lower recess 24. The upper recess 20 defined by retaining edge 22 is configured and dimensioned so as to allow circuit board 14 to fit within the upper recess 20 and be bounded by the retaining edge 22. Similarly, lower recess 24 is configured and dimensioned so as to provide sufficient volume to receive the electrical components 52 of the lower adjacent circuit board 14 when the layers 12 are stacked together. Notably, when the layers 12 are stacked together the upper surface 26 of the retaining edge 22 of one layer 12 electrically contacts the lower surface 28 of the upper adjacent metal carrier 16 so as to define fully enclosed recesses 20 and 24 of adjacent layers 12, thereby precluding any interference between the signals of the circuit board 14 positioned within the adjacent recesses 20 and 24. The connector assemblies 18 are each positioned within a hole 30 formed through the metal carrier 16. Each of the connector assemblies 18 comprises a metal conductor 32 having a pair of button connectors 34 positioned at the end 36 of the metal conductor 32. The metal conductor 32 and its button connectors 34 are secured in axial alignment in an axial hole 38 formed by a pair of dielectric inserts 40 and 42. The dielectric inserts 40 and 42 are preferably retained within hole 30, such as by press fitting. Preferably, each of the button connectors 34 are typically farmed from a strand of gold plated resilient wire which is wadded together to form a nearly cylindrical "button" of wadded metal wire having a density of between 20 and 30%. As known in the art, these types of button connectors make electrical contact at multiple points when pressed against a contact area. Hence, button connectors have significant advantages over other types of connectors by providing low parasitic connections of high integrity and reliability with high current capability and zero insertion force. Furthermore, the compression force required for deflecting the button can be accurately predetermined based upon the metal wire and the density that the metal wire is wadded. Thus, button connectors are particularly advantageously employed in electronic assemblies subjected to high inertial forces since the percent button deflection for a particular rate of acceleration is easily predetermined. As shown in Fig. 2, each of the dielectric inserts 40 and 42 includes a reduced diameter portion 44 which functions to compress the midline of the button connector 34 positioned therein into an "hour-glass" configuration thereby retaining the button connector 34 therein. The reduced diameter portion 44 also functions to create a shoulder 46 which bears against the edges 48 of the metal conductor 32. Upon proper dimensioning, the metal conductor 32 may be securely retained within the axial holes 38 of the dielectric inserts 40 and 42 thereby precluding any axial movement of the metal conductor 32 within the axial holes 38. Finally, as shown in Fig. 2, the protruding ends 50 of the button connectors 34 may be rounded into a semi-circle configuration or, as shown in Fig. 5, may be formed into a cylindrical configuration. The circuit board 14 comprises a conventional multi-layer board having electrical components 52 mounted to the surface thereof. A pair of metal pads 54 are formed on the upper and lower surfaces of the circuit board 14 so as to electrically contact the protruding ends 50 of the button connectors 34 of adjacent connector assemblies 18. The metal pads 54 on opposing sides of the circuit board 14 are electrically interconnected by means of a plated-through-hole 56 extending transversely through the laminated layers of the circuit board 14. Notably, any one of the circuit functions of the circuit board 14 may be electrically connected to the metal pads 54 by means of an internal (or external) circuit traces 58. A dielectric insulator 60 is preferably sandwiched between the lower surface of the circuit board 14 and the upper recess 20 so as to insulate the circuit board 14 from the metal carrier 16. However, the dielectric insulator 60 contains a plurality of holes 62 so as to permit the interconnection of the protruding ends 50 of the button connectors 34 with the respective metal pads 54 of the circuit board 14. Similarly, an upper, dielectric insulator 64 with holes 66 is provided for positioning between the upper surface of the circuit board 14 and the lower surface 28 of the adjacent metal carrier 16 so as to insulate the circuit board 14 from the metal carrier 16 while allowing interconnection of the protruding ends 50 of the button connectors 34 with the respective metal tabs 54 of the circuit board via hole 66. This upper dielectric insulator 64 is shaped so as to allow room for the electrical components 52. Returning to Fig. 1, it is seen that the shielded and wireless interconnect apparatus 10 of the invention is particularly suitable for use in connection with a cannonlaunched projectile 70 which is subjected to acceleration forces. In this particular application, the circuit boards 14 and correspondingly, metal carrier 16, are preferably circular so as to define a substantially cylindrical configuration when the layers 12 are stacked together within the projectile 70 thereby forming a part of the support structure of the projectile and to define its overall design. Notwithstanding, it should be realized that other, non-circular configurations may be employed without departing from the spirit and scope of this invention. As shown in Figs. 3A and 3B, it should also be realized that a substantial plurality of aligned connector assemblies 18 may be employed so as to create many transmission line paths interconnecting adjacent and distant circuit boards 14 of the stack. Furthermore, while the foregoing description describe transmission line paths extending through the outer periphery of the stacked layers 12, it should be appreciated that the transmission line paths formed by the connector assemblies 18 and corresponding metal pads 54/plated-through-holes 56 may be formed through any area of the stacked layers 12, such as in a circular ring 68 of transmission line paths formed inwardly of the outer periphery of the metal carriers 16. The shielded and wireless interconnect apparatus 10 of this invention offers many advantages. Specifically, the stacked arrangement of the layers of circuit boards 14 mounted within the recesses 20 and 24 of the metal carriers 16 result in each circuit board 14 being fully enclosed within the adjacent metal carriers 16. Thus, signals of one circuit board 14 in one layer are isolated from signals of adjacent and distant circuit boards 14 and from outside interference signals. The layers of the shielded and wireless interconnect apparatus 10 of this invention may therefore be optimally designed to isolate analog signals from digital signals (or any combination thereof). Similarly, the connector assemblies 18 are also fully shielded by the metal carriers 16 in which they are respectively embedded. Thus, each transmission line path formed by aligned connector assemblies 18 is electrically shielded, thereby preventing any electrical interference between adjacent and distant transmission line paths and from outside interferences. Another important advantage is the fact that the metal carriers 16 provide structural support for the circuit boards 14 thereby increasing the ruggedness of the circuit boards 14 when employed in high inertial applications, such as shown in Fig. 1. A still further advantage is the fact that the metal carriers 16 may function as a heat sink for high power components. Specifically, as shown in Fig. 4, high powered components 72 may be adhered, via a hole 74 in the circuit board 14, to the metal carrier 16 by means of a thermally conductive epoxy 76. Finally, it should be noted that while one embodiment of the connector assemblies 18 is illustrated others are possible without departing from the scope of this invention. For example, as shown in Fig. 5, connector assemblies 18 may comprise a sleeve 80 composed of a dielectric material having its lumen 82 plated with an electrically conductive material 84. The conductor buttons 34 may be cylindrically shaped and are retained in opposing ends of the sleeve 80 by additionally plating until the buttons 34 are bonded to the lumen 82 of the sleeve 80. The sleeve 80 is then press fitted into hole 30 of the metal carrier 16.

Claims: Interconnecting system for a plurality of circuit boards (14), comprising: a pluarlity of carriers (16) stacked together with the circuit boards (14) and a plurality of transmission line paths extending through the carriers (16) to the circuit boards (14) each path comprising a connector assembly (18) embedded within a carrier (16) and having a central conductor element (32) and a pair of button connectors (34) in alignment therewith and each button connector protruding from the respective carrier (16) characterized in that each circuit board (14) is received within a recess (20, 24) which is defined by two adjacent carriers (16) formed of electrically conductive material, the circuit boards (14) are insulated from the carriers (16) by means of dielectric insulators (60, 64) positioned between two adjacent carriers (16), and the connector assemblies (18) are insulated from the carriers by dielectric inserts (40, 42). Interconnecting system according to claim 1, characterized in that the recess between two adjacent carriers (16) is formed within the upper and the lower surface respectively of each carrier. Interconnecting system according to claim 2, characterized in that the recess (20) formed within the upper surface of each carrier (16) is defined by an upstanding retaining edge (22) for enclosing the circuit board therein and that the recess (24) formed within the lower surface of each carrier (16) encloses electrical components (52) mounted to the circuit board (14). Interconnecting system according to claim 3, characterized in that an upper surface (26) of the retaining edge (22) of each carrier (16) is planar and parallel with respect to a planar lower surface of the adjacent carrier (16) such that the surfaces are electrically interconnected to fully enclose and shield each circuit board (14) positioned between adjacent carriers (16). Interconnecting system according to claims 1 - 4, characterized in that the connector assemblies (18) comprise a sleeve (80) composed of a dielectric material having its lumen (82) plated with an electrically conductive material (84). Interconnecting system according to claim 1, characterized in that the dielectric inserts are formed in two sections (40, 42), each section including a reduced diameter portion (44) for securing the button connectors (34) therein and for securing the conductor elements (32) within the sections (40, 42) of the inserts (14). Interconnecting system according to claim 1, characterized in that each button connector (34) comprises a semispherical end (50) or a cylindrical configuration which protrudes from the respective carriers.

Inventors: BURKETT FRANKLIN S JR, FERNANDEZ ALLEN NMN, BURKETT, FRANKLIN S., JR., FERNANDEZ, ALLEN (NMN)
Applicants: HERCULES DEFENSE ELECTRONICS S, HERCULES DEFENSE ELECTRONICS SYSTEMS, INC.
Application year: 1992
Main classification: H01R23
IPC codes: H01R12, H05K7