Patent Application
20140268621
The present invention relates generally to printed circuits and in particular, to the electrical interface and coupling of the edge surface of one printed circuit to another printed circuit or target platform.
A printed circuit or printed circuit board (PCB) provides electrical connection to components mounted on its surface to achieve a specific function. It is at times more advantageous to provide a smaller PCB, hereinafter also referred to as a “daughter-board”, “module”, or “electric subassembly” for mechanically attaching and electrically interfacing or coupling, hereinafter also referred to as “mounting,” to a larger PCB, hereinafter referred to as “mother-board” or “main-board” or “target platform.” Modules enable system designers to add desired application features and reduce main-board surface area. Typically, mounting a module to the target platform requires providing both mechanical support of the module and connections for multiple electrical signals between the module and target platform. A module may be mounted with its component-carrying surface substantially perpendicular to the component-carrying surface of the target platform, hereinafter also referred to as “vertical mounting”.
Vertical mounting of a module has been provided by plating a set of gold fingers along an edge of the module on opposite sides of the board's component mounting surfaces. The portion of the module with the set of gold fingers may be called a parallel edge connection, for plugging into a corresponding socket on the target platform. Inside the socket, there is a set of fine-pitched parallel springs to make contact with the set of gold fingers on the module. Frequently, the set of fine-pitched parallel springs may suffer spring bending or dislocation due to insertion problems, or surface contamination due to exposure to dust or environmental contamination. Module insertion into the socket may also damage and scratch the surface of the gold fingers. These problems with the parallel edge connection system either on the module or at the socket may lead to failure. Replacing the damaged socket or module is sometimes not an easy task and expensive.
The module may be shaped so that the parallel edge connection fits into a socket in just one orientation, a mechanism called “keying”. The keying is achieved through one or two non-plated notches on module and one or two corresponding insulated bumps inside the socket. Besides the use for orientation identification, the keying is also used to align the positions of gold fingers on a module with the position of springs inside a socket. The accuracy of the keying position impacts insertion accuracy into the socket. Because the springs in the socket are manufactured through a mechanical punch and bending process, a severe limitation is imposed on the distance between two neighboring springs, or the finger pitch, especially if the number of fingers is large. The finest finger pitch for a large finger count socket is about 0.5 mm. It becomes harder to reduce the pin pitch further due to mechanical and manual insertion limitations. Off-the-shelf parallel edge connections and sockets have predetermined finger pitch, which may use up area on the component mounting surface of the module and the main-board and increase system cost. Additionally, the spacing between adjacent sockets is rather large because the width of the socket to support parallel edge connection is large which degrades effective use of the main board area. A solution to support vertical mounting but without these drawbacks of spring mechanical insertion and in parallel edge connection is desired.
According to one embodiment of the present invention, an electric apparatus is adapted to be electrically coupled to a target platform. The electric apparatus includes a first printed circuit including a first surface substantially parallel to a first plane and a second surface substantially parallel to a second plane perpendicular to the first plane. The first surface has a first area and the second surface has a second area smaller than the first area. A multitude of conductive traces are formed in a layer of the first printed circuit substantially parallel to the first plane. A first contact region overlays a first portion of the second surface. The first contact region is electrically connected to a first one of the multitude of conductive traces. A second contact region overlays a second portion of the second surface. The second contact region is electrically connected to a second one of the multitude of conductive traces. The first printed circuit is coupled to the target platform at the first and second contact regions when the first printed circuit is electrically coupled to the target platform.
According to one embodiment, the first contact region is coupled to a first circuit node and the second contact region is coupled to a second circuit node different than the first circuit node when the first printed circuit is electrically coupled to the target platform. According to one embodiment, a power and a ground carried on the multitude of conductive traces are coupled from the first printed circuit to the target platform respectively through the first and second contact regions at the second surface of the first printed circuit when the first printed circuit is electrically coupled to the target platform.
According to one embodiment, the first portion of the second surface is substantially planar where the first contact region overlays the second surface. According to one embodiment, the first contact region includes a first width in a first direction substantially parallel to an intersection of the first plane and the second plane. The second contact region includes a second width in the first direction different than the first width.
According to one embodiment, the first printed circuit further includes a conductive layer overlaying a portion of the first surface, the conductive layer disposed adjoining to the first conductive region. The first contact region extends to an edge between the first surface and the second surface, the conductive layer being electrically connected to the first conductive region.
According to one embodiment, the first printed circuit includes a third surface parallel to the first plane. The first contact region extends from an edge between the first surface and the second surface to an edge between the second surface and the third surface.
According to one embodiment, the first printed circuit includes a third surface parallel to the first plane. The first contact region is recessed from an edge between the first surface and the second surface and recessed from an edge between the second surface and the third surface.
According to one embodiment, the first printed circuit includes a solder ball connected to the first conductive region. According to one embodiment, a center of the first contact region and a center of the second contact region are disposed substantially on a line in a direction perpendicular to the first plane.
According to one embodiment, the first contact region is connected to a conductive pin. According to one embodiment, the first contact region includes a conductive membrane layer. According to one embodiment, the first contact region includes an elastic contact. According to one embodiment, the first printed circuit includes a recess in the second surface adapted to align the first printed circuit to the target platform when the first printed circuit is coupled to the target platform.
According to one embodiment, the electric apparatus further includes a second printed circuit including a third surface substantially parallel to the first plane and a fourth surface substantially parallel to the second plane. The third surface has a third area and the fourth surface has a fourth area smaller than the third area. The second printed circuit is coupled to the first printed circuit. A multitude of conductive traces of the second printed circuit is formed substantially parallel to the first plane, and a third contact region overlays a first portion of the fourth surface. The third contact region is electrically connected to a first one of the multitude of conductive traces of the second printed circuit. The second printed circuit is coupled to the target platform at the third and fourth contact regions when the second printed circuit is electrically coupled to the target platform.
According to one embodiment, the electric apparatus further includes at least one conductor adapted to electrically connect a corresponding one of the multitude of conductive traces of the first printed circuit to a corresponding one of the multitude of conductive traces of the second printed circuit. According to one embodiment, the electric apparatus further includes a housing partially enclosing the first and second printed circuits, the housing adapted to mechanically position the first and second printed circuits so as to electrically couple the first and second printed circuits to the target platform when the first and second printed circuits are coupled to the target platform.
According to one embodiment, the electric apparatus further includes a thermally conducting and electrically insulating layer disposed in contact with the first printed circuit and the second printed circuit. According to one embodiment, the electric apparatus further includes a heat dissipater in mechanical contact with the thermally conducting and electrically insulating layer. According to one embodiment, the thermally conducting and electrically insulating layer includes a via adapted to position an interconnect element to connect a corresponding one of the multitude of conductive traces of the first printed circuit to a corresponding one of the multitude of conductive traces of the second printed circuit.
According to one embodiment of the present invention, a method electrically couples a first printed circuit to a target platform. The first printed circuit includes a first surface substantially parallel to a first plane and a second surface substantially parallel to a second plane perpendicular to the first plane. The first surface has a first area and the second surface has a second area smaller than the first area. The first printed circuit further includes a first multitude of conductive traces formed in a layer of the first printed circuit substantially parallel to the first plane. The method includes overlaying a first contact region on a first portion of the second surface of the first printed circuit, and overlaying a second contact region on a second portion of the second surface of the first printed circuit. The method further includes electrically connecting the first contact region to a first one of the first multitude of conductive traces, and electrically connecting the second contact region to a second one of the first multitude of conductive traces. The first printed circuit is coupled to the target platform at the first and second contact regions when the first printed circuit is electrically coupled to the target platform.
According to one embodiment, the method further includes coupling the first contact region to a first circuit node, and coupling the second contact region to a second circuit node different than the first circuit node when the first printed circuit is electrically coupled to the target platform. According to one embodiment, the method further includes coupling a power and a ground on the first multitude of conductive traces from the first printed circuit to the target platform respectively through the first and second contact regions at the second surface of the first printed circuit when the first printed circuit is electrically coupled to the target platform.
According to one embodiment, the method further includes forming the first portion of the second surface to be substantially planar where the first contact region overlays the second surface. According to one embodiment, overlaying the first contact region includes providing a first width in a first direction substantially parallel to an intersection of the first plane and the second plane. The second contact region includes a second width in the first direction different than the first width.
According to one embodiment, the method further includes overlaying a conductive layer on a portion of the first surface adjoining to the first conductive region, and electrically connecting the conductive layer to the first conductive region. Overlaying the first contact region includes extending the first contact region to an edge between the first surface and the second surface.
According to one embodiment, overlaying the first contact region includes extending the first contact region from an edge between the first surface and the second surface to an edge between the second surface and a third surface of the first printed circuit, the third surface being parallel to the first plane. According to one embodiment, overlaying the first contact region includes recessing the first contact region from an edge between the first surface and the second surface and recessing the first contact region from an edge between the second surface and a third surface of the second printed circuit, the third surface being parallel to the first plane.
According to one embodiment, overlaying the second contact region includes disposing a center of the first contact region and a center of the second contact region substantially on a line in a direction perpendicular to the first plane. According to one embodiment, the method further includes connecting a solder ball to the first conductive region. According to one embodiment, the method further includes connecting a conductive pin to the first contact region. According to one embodiment, the method further includes forming a recess in the second surface to align the first printed circuit to the target platform when the first printed circuit is coupled to the target platform.
According to one embodiment, the method further includes coupling a second printed circuit to the first printed circuit. The second printed circuit includes a third surface substantially parallel to the first plane and a fourth surface substantially parallel to the second plane. The third surface has a third area and the fourth surface has a fourth area smaller than the third area. The second printed circuit includes a second multitude of conductive traces formed in a layer of the second printed circuit substantially parallel to the first plane. The method further includes overlaying a third contact region on a third portion of the fourth surface of the second printed circuit, and electrically connecting the third contact region to a first one of the second multitude of conductive traces. The second printed circuit is coupled to the target platform at the third and fourth contact regions when the second printed circuit is electrically coupled to the target platform.
According to one embodiment, coupling includes electrically connecting at least one conductor between a corresponding one of the first multitude of conductive traces of the first printed circuit to a corresponding one of the second multitude of conductive traces of the second printed circuit.
According to one embodiment, the method further includes partially enclosing the first and second printed circuits in a housing, and mechanically positioning the first and second printed circuits with the housing to electrically couple the first and second printed circuits to the target platform when the first and second printed circuits are coupled to the target platform.
According to one embodiment, coupling includes disposing a thermally conducting and electrically insulating layer in contact with the first printed circuit and the second printed circuit. According to one embodiment, coupling includes mechanically connecting a heat dissipater to the thermally conducting and electrically insulating layer. According to one embodiment, the thermally conducting and electrically insulating layer includes a via for positioning an interconnect element connecting a corresponding one of the first multitude of conductive traces of the second printed circuit to a corresponding one of the second multitude of conductive traces of the second printed circuit.
According to one embodiment of the present invention, a method for electrically connecting a printed circuit to a target platform includes forming the printed circuit including a first surface substantially parallel to a first plane and a second surface substantially parallel to a second plane perpendicular to the first plane. The first surface has a first area and the second surface has a second area smaller than the first area. The method further includes forming a multitude of conductive traces in a layer of the printed circuit substantially parallel to the first plane, overlaying a first contact region on a first portion of the second surface of the printed circuit. The method further includes overlaying a second contact region on a second portion of the second surface of the printed circuit, electrically connecting the first contact region to a first one of the multitude of conductive traces, and electrically connecting the second contact region to a second one of the multitude of conductive traces.
According to one embodiment of the present invention, a first electric subassembly is adapted to be electrically connected to a second electric subassembly. The first electric subassembly includes a multitude of planar bases. At least one of the multitude of planar bases includes a first surface substantially parallel to a first plane having a first area, and a second surface substantially parallel to a second plane perpendicular to the first plane, the second surface having a second area smaller than the first area. At least one of the multitude of planar bases further includes a multitude of electrically conductive traces positioned in the first plane, a multitude of regions on the second surface, and a multitude of electrical conductors each being associated with and overlaying a different one of the multitude of regions. The multitude of electrical conductors are each associated with and electrically connected to a different one of the multitude of electrically conductive traces. At least one thermally conducting and electrically insulating layer is disposed between at least a first subset of the multitude of planar bases.
According to one embodiment, each of the multitude of regions is substantially co-planar with the second surface where each of the multitude of electrical conductors overlays the second surface.
A better understanding of the nature and advantages of the embodiments of the present invention may be gained with reference to the following detailed description and the accompanying drawings.
A printed circuit, hereinafter also referred to as a printed circuit board (PCB), is a pattern comprising printed wiring formed in a predetermined design in, or attached to, the surface or surfaces of a common base. The base of a printed circuit may include an insulating planar substrate or board formed from a heat resistant resin and reinforcing fiber such as FR4, polyimide, ceramic or other insulating materials. In contrast, semiconductor material forms at least part of the base or substrate of an integrated circuit. The printed circuit may provide electrical connection and mechanical support to an integrated circuit or semiconductor chip mounted on at least one of the two component mounting surfaces of the printed circuit. A printed circuit is thus distinguished from an integrated circuit because the base of a printed circuit does not include a semiconductor material between the two component mounting surfaces of the printed circuit.
The printed wiring is a patterned conductive layer or layers on a surface of and/or within the printed circuit, so as to provide point-to-point, point-to-multipoint, point-to-ground or power plane electric connection and to make electrical connection when electrical components are mounted on a component mounting surface of the printed circuit. It is understood in describing the embodiments of the present invention that the term conductive applies to any material including electrical resistivity less than 10−2 ohm-cm. It is understood in describing the embodiments of the present invention that the terms connect, connected, and connecting applies to making direct electrical contact or connection between at least two conductive elements without intervening passive or active circuit elements. For example, two conductive elements may be connected by direct mechanical contact, solder, conductive glue, conductive membrane or other conductive material.
The present invention relates generally to printed circuits and in particular, to the electrical interface and coupling of the edge surface of one printed circuit to another printed circuit or target platform. According to an embodiment of the present invention, a multitude of conductive regions, hereinafter also referred to as contact regions, may be formed on an edge surface of a module. The contact regions on the edge surface of the module function as connectors, which facilitate vertical mounting of the module to a target platform and reduce the cost and size of the module and connection system.
Contact region 110 overlays a portion of edge surface 120 and may include a width We in a first direction, which is substantially parallel to an intersection of the first plane and the second plane, e.g. in the direction of edge 140 between the edge surface and the component mounting surface. Contact region 110 may include a height Hc in a direction substantially perpendicular to the first plane. The portion of edge surface 120 under contact region 110 may be substantially planar where contact region 110 overlays edge surface 120, which simplifies manufacturing of the module. Consequently, contact region 110 may form a substantially planar contact area. In one embodiment, the material forming the contact region may be a layer of copper or other metal common to printed wiring, similar to conductive composite materials, and/or include a conductive membrane layer. In one embodiment, PCB 105 includes a thickness Tb. Height Hc may be equal to or smaller than thickness Tb. The shape of contact region 110 may include a square, a rectangle, a trapezoid, a circle, an ellipse, or any shape or combination of shapes.
In one embodiment, PCB 105 may include a surface conductive layer 150, which may overlay a portion of component mounting surface 130 disposed adjoining contact region 110. In another embodiment, surface conductive layer 150 may overlay a portion of component mounting surface 130 disposed adjoining and directly connected to contact region 110 at edge 140, the contact region being extended to edge 140 in this case. Surface conductive layer 150 may improve the mechanical and electrical integrity of the connection of PCB 105 to a motherboard (not shown) after mounting. In some embodiments, surface conductive layer 150 may be optional and omitted to free-up area on the component mounting surface.
In one embodiment, PCB 105 may include a conductive trace 170 having a width Wt in the first direction and formed in a layer of PCB 105, which is substantially parallel to component mounting surface 130. Conductive trace 170 may be on a surface of PCB 105, or may be on a layer embedded within PCB 105 (not shown). Conductive trace 170 may be electrically connected directly to contact region 110 or optionally through surface conductive layer 150. PCB 105 may include single-layered printed wiring or multi-layered printed wiring. The conductive trace 170 may carry power, ground, and/or signals to and from contact region 110, which in-turn may carry those signals to an associated contact on the surface of the motherboard or target platform where the module is to be mounted. Contact region 110 is adapted to transfer electricity from conductive trace 170 to the target platform through contact region 110 at edge surface 120 when PCB 105 is electrically coupled to the target platform. In other words, PCB 105 is electrically coupled to the target platform at contact region 110 when PCB 105 is electrically coupled to the target platform. The target platform may be a mother-board, main-board, another module, or a socket or connector mounted on a chassis.
The term coupled means not directly connected but connected through other elements. For example, the PCB may be coupled to the target platform through the contact region and a connector adapted to electrically interconnect the PCB to the target platform. Alternatively, the PCB may be coupled to the target platform through an anisotropic conductive membrane (ACM) positioned at the target platform, or through a conductive membrane or conductive spring at the contact region of the PCB, to facilitate electrical connection between the PCB and the target platform.
In one embodiment, a module electrical system 470 may be coupled between one of the multitude of contact traces 170 and the second contact trace 270 on PCB 305/second module 300. Module electrical system 470 may include one or more integrated circuit (IC), active and/or passive devices mounted on the component mounting surface of second module 300. The electrical circuit on target platform 405 may complete the circuit connections on second module 300 when the target platform is powered up, forming a completed electrical system 400. Thus, conductive traces 170 and 270 may correspond to different electrical nodes of the module electrical system 470. In other words, one of the multitude of contact regions 110 may be coupled to a first circuit node 170 and the second contact region 210 may be coupled to a second circuit node 270 different than the first circuit node when second module 300 is electrically coupled to target platform 405. In another embodiment, a power and a ground electrical supplies are carried on one of the multitude of conductive traces 170 and conductive trace 270, which are coupled from second module 300 to target platform 405 respectively through the first and second contact regions 110 and 210 at the edge surface of second printed circuit 305, when the module is electrically coupled to the target platform.
In one embodiment, target platform 405 includes an optional keying extension 430 that may be adapted to engage with recess 330 on PCB 305 when module 300 is properly aligned to target platform 405 so that all the contact regions 110 and 210 are properly aligned with the contact targets 410 to the target platform, when module 300 is electrically coupled to target platform 405. To accomplish the alignment, recess 330 may be positioned offset from the center of module 300 so that placement of the module on the target platform will not be made in reverse orientation. If a module is placed with reverse orientation but approximately in the correct location, keying extension 430 would not be able to engage into recess 330, preventing module 300 from being placed in a proper position relative to target platform 405, which would be detectable by placement equipment before module mounting is completed. Keying extension 430 may be implemented by a pin or ridge built into the target platform
Unlike prior art solutions, contact regions 110 and 210 on module 300 eliminate the significant cost added to the module when a discrete prefabricated, off-the-shelf socket is used. Further, module 300 enables the module to be mounted closer to other modules on the main-board's component surface than would be possible in common vertical mounting due to the larger width required by using a parallel edge connection socket on the main-board. Module 300 thus provides a tighter module spacing to fit into systems requiring smaller form factors.
In one embodiment, a conductor 1020 for connecting signals, power or ground may be embedded between adjacent attached modules. Conductor 1020 may be adapted to electrically connect a corresponding one of the multitude of conductive traces of printed circuit 1015 to a corresponding one of the multitude of conductive traces of printed circuit 2010. In one embodiment, modules 1015 and 1010 may be attached at a few predetermined locations. In one embodiment, modules 1015 and 1010 may be attached substantially continuously using an in-fill or adhesive material across substantially all matching attachment surfaces. The attached modules embodiment may be combined with any of the embodiments described above that facilitate the recess keying function, surface or internal conductive trace, recessed contact region, partly recessed contact region (e.g. as shown in
In one embodiment, a thermally conducting and electrically insulating layer 1095 may be in contact with, sandwiched or disposed between modules 1010 and 1015. In one embodiment, the thermally conducting and electrically insulating layer 1095 may be formed such that a portion of thermally conducting and electrically insulating layer 1095A extends to a surface other than the surface adjacent the component mounting surfaces. Thermally conducting and electrically insulating layer 1095 may be provided to attach modules 1010 and 1015. Thermally conducting and electrically insulating layer 1095 may be an epoxy adhesive with a thermally conducting but electrically insulating filler material such as boron nitride such as 3M™ Thermally Conductive Epoxy Adhesive TC-2810. A heat dissipater 1096 may be placed in contact with thermally conducting and electrically insulating layer 1095A. Heat dissipater 1096 may include a heat sink, a heat pipe, a heat sink with fan, or a thermoelectric cooler, and so on. It is understood that more than two modules may be attached together. In one embodiment, an interconnect element or conductor 1020 may be placed through a via in thermally conducting and electrically insulating layer 1095. The via may be adapted to position an interconnect element to connect a corresponding one of the plurality of conductive traces 170 of module 1010 to a corresponding one of the plurality of conductive traces of module 1015.
Recess 330 may be optional included in any combination. For example, recess 330 may be aligned between all the modules and cut through the thermally conducting and electrically insulating layer 1095 at corresponding locations forming a slot in the edge surface of assembly 1000. The slot in the edge surface of assembly 1000 enables assembly 1000 to engage with a ridge or fin extending out of the target platform when assembly 1000 is mounted, to the target platform to facilitate the keying function as described above.
In one embodiment, a multitude of modules may be attached together forming a compact 3-D module with the plane of the component mounting surfaces on each module positioned substantially perpendicular to the component mounting surface of the target platform when the 3-D module is mounted to the target platform. The thermally conducting and electrically insulating layer and heat dissipater embodiment may be combined with any of the embodiments described above in any combination. In one embodiment, semiconductor chips, other discrete components, or packaged discrete components may be mounted at any of the component mounting surfaces of modules 1015 and 1010.
In one embodiment, the mechanical positioning of assembly 1100 within housing 1130 is facilitated by interposers 1150A, 1150B, and 1150C positioned between the inner surfaces of housing 1130 and the outer surfaces assembly 1100. In one embodiment, the mechanical positioning of housing 1130 onto target platform 1405 is provided by locking clips 1160 that engage through holes in the target platform to secure housing 1130, assembly 1100 and interposers 1150A, 1150B, and 1150C against target platform 1405 at a position to properly align contact regions 110 on assembly 1100 with contact targets 410 on the target platform. Interposers 1150A, 1150B, and 1150C may be a mechanically elastic material that provides cushioning and/or may be thermally conductive to provide heat dissipation from assembly 1100 to housing 1130, which may also function as a heat radiator.
The above embodiments of the present invention are illustrative and not limiting. Various alternatives and equivalents are possible. Although, the invention has been described with reference to a PCB by way of an example, it is understood that the invention is not limited by the terms board, base, or substrate so long as the base material may be manufactured with a contact region on an edge surface of the base. The embodiments of the present invention are not limited by the size or shape of the contact region. The embodiments of the present invention are not limited by the type of target platform. The embodiments of the present invention are not limited by the size of the printed circuit, the size of the target platform, or the size relationship between the printed circuit and the target platform. The embodiments of the present invention are not limited by types of discrete components connected to the component mounting surface of the printed circuit, such as discrete passive components, microelectronic circuits, semiconductor circuits, other printed circuits or circuit boards, solar panels, thin-film-transistor arrays, and so on. Further, the invention may be used in electrically connecting one printed circuit to another printed circuit or target platform, not limited to permanent or removable electrical connections. Other additions, subtractions, or modifications are obvious in view of the present disclosure and are intended to fall within the scope of the appended claims.
