Abstract:
A connector for connecting surface mount devices, such as light emitting diodes (LEDs), to printed circuit boards (PCBs). The connector may be prepackage with an LED assembly or on a PCB to which the LED assembly will be mounted. Connection complexity can be moved from the PCB to the connector, and LED assemblies may be customized differently for different customers. One to many and many to one connections are readily supported with variations on the connector.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to improvements in the field of physical mounting and electrical connection arrangements for semiconductor devices, such as light emitting devices, and, in particular, to methods and apparatus for improving the flexibility of light emitting device mounting and electrical connection arrangements. 
     BACKGROUND OF THE INVENTION 
       FIGS. 1A ,  1 B,  1 C and  1 D illustrate a standard LED packaging arrangement, such as that employed by the XLamp® 7090 XR-E series of LED products manufactured by Cree, Incorporated, and how that packaged LED lamp may be suitably mounted on a larger printed circuit board (PCB). As seen in  FIG. 1A , the packaged LED lamp  100  comprises a lens  102 , a reflector  104  and a mounting substrate  106 . The arrangement  100  may also be referred to as an LED, LED lamp or a lamp. As seen in  FIG. 1B , an LED chip  108  is electrically connected by bond wires  110  and  112  to electrical contact strips  114  and  116 , respectively, on the substrate  106  which may suitably be a printed circuit board (PCB), such as a flame resistant  4  (FR 4 ) board. When power is applied through the contacts  114  and  116 , chip  108  emits light. The chip  108  is shown as having two top contacts for a chip having a horizontal arrangement. However, alternative LED chips and chip mounting arrangements are possible where the LED has a horizontal or vertical orientation or is flip chip mounted, as would be understood by one of ordinary skill in the art. In the arrangement shown, reflector  104  helps direct the emitted light upwards and the lens  102  focuses the emitted light. The chip  108  is thermally mounted on top surface  118  of substrate  106  with a thermal bonding paste.  FIG. 1C  shows a bottom surface  120  of the substrate  110  and electrical contacts  114  and  116  along with representative dimensions for the XLamp® 7090 XR-E series of LED products. It will be recognized that 9.0 mm is slightly smaller than 1 cm and is about ⅓ of an inch. As a result, it can be seen that the XLamp® LED products and other similar products have a small form factor compared to typical incandescent bulbs.  FIG. 1D  shows a solder pad  120  for mounting the packaged LED lamp  100  to a larger PCB. 
     Reflow surface mount techniques are highly efficient for lamps, such as lamp  100  where bottom contacts  114  and  116  can be reflow soldered to traces of a printed circuit board. However, as LED lamps become more complex with larger numbers of contacts and chips being employed, for example, and a much wider array of different applications, as such lamps are more widely adopted, additional flexibility as to physical mounting and electrical connection arrangements is highly desirable. 
     For example, two applications assigned to the assignee of the present application address aspects of such needs. See, for example, U.S. application Ser. No. 11,614,261 filed Dec. 21, 2006 and issued as U.S. Pat. No. 7,549,786 and U.S. application Ser. No. 12/335,631 filed Dec. 16, 2009, both of which are incorporated by reference herein in their entirety. 
     SUMMARY OF THE INVENTION 
     The present invention recognizes and anticipates that more complex lamps with additional electrical contacts will present both connection and heat dissipation issues. Further designs where top contacts are desirable or required, and the like, present additional connection problems. In this context, the present invention recognizes that further additional flexible mounting techniques are highly advantageous. Among its several aspects, the present invention provides flexible connection arrangements as described further herein. Among the several advantages of such arrangements, the contacts of a connector can be modified to adapt a standard LED lamp as desired by a particular customer or customers to customize that lamp for the particular customer and the particular application. Thus, purely as an illustrative example, one customer might want to drive a string or strings of an LED lamp with the same current. Another, might want drive each line individually with a different predetermined drive current. Finally, a third might want to vary the drive current on a line by line basis. Additional advantages may include the simplification of board layout, allowing for populating or depopulating a board based on needs of lighting designers, and ease of manufacture by reducing the number of connectors to one as opposed to one or more for each LED. Connection arrangements such as those described herein facilitate such variations. 
     According to one aspect, a connector for physically and electrically connecting a light emitting device to a printed circuit board is provided. The connector comprises a stiff body shaped to help mount the light emitting device to the printed circuit board; a first plurality of exposed electrical contacts corresponding to electrical contacts on the light emitting device; a second plurality of exposed electrical contacts corresponding to electrical contacts on the printed circuit board; and electrical connections connecting the first plurality of exposed electrical contacts to the second plurality of exposed contacts. 
     According to another aspect, a connector and LED lamp package is provided. The package comprises an LED lamp mounted on a substantially planar mounting board having electrical contacts on a top surface; a connector for electrically connecting the electrical contacts of the LED lamp to corresponding electrical traces of a printed circuit board. The connector comprises a first plurality of exposed electrical contacts corresponding to the electrical contacts on the top surface of the LED lamp; a second plurality of exposed electrical contacts corresponding to where electrical contacts on a printed circuit board are to be; and electrical connections connecting the first plurality of exposed electrical contacts to the second plurality of exposed contacts. The first plurality of electrical contacts of the connector are soldered to the electrical contacts of the LED lamp to form an integrated package. 
     According to a further aspect, a board and connector package is provided. The package comprises a printed circuit board with electrical contacts for providing drive current to contacts of an LED lamp; a connector for electrically connecting the electrical contacts of the printed circuit board to the contacts of the LED lamp. The connector comprises a first plurality of exposed electrical contacts corresponding to the electrical contacts of the LED lamp; a second plurality of exposed electrical contacts corresponding to electrical contacts on the printed circuit board; and electrical connections connecting the first plurality of exposed electrical contacts to the second plurality of exposed contacts. The second plurality of contacts of the connector are soldered to the electrical contacts of the printed circuit board to form an integrated package. 
     These and other advantages and aspects of the present invention will be apparent from the drawings and Detailed Description which follow. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A ,  1 B and  1 C show a top perspective, a top, and a bottom view, respectively, of a typical prior art mounting arrangement for mounting an LED on a flame resistant (FR)  4  board; and  FIG. 1D  shows a printed circuit board (PCB) solder pad for mounting the LED lamp package of  FIGS. 1A-1C  to a larger PCB board for a particular application; 
         FIG. 2  illustrates a perspective view of a connector and mounting arrangement in accordance with a first embodiment of the present invention. 
         FIGS. 3A ,  3 B and  3 C illustrate a perspective view of an alternative mounting arrangement in which a connector in accordance with the present invention is preapplied to a printed circuit board, as well as, bottom views of two arms of the connectors; 
         FIG. 4  illustrates a perspective view of an alternative mounting arrangement in which a connector in accordance with the present invention is preapplied to a lamp mounting board; 
         FIG. 5  illustrates an arrangement in which a connector in accordance with the present invention provides multiple to one and one to multiple connectivity; 
         FIG. 6  illustrates an arrangement in which a connector in accordance with the present invention simplifies connections by internal rerouting; 
         FIG. 7  illustrates a perspective view in which a connector in accordance with the present invention applies spring pressure to insure good mechanical and electrical connection and additionally provides added thermal dissipation; 
         FIG. 8  illustrates a perspective view of connectors in accordance with the present invention utilized to adapt a smaller LED lamp for use with an existing printed circuit board with electrical traces for a larger lamp; 
         FIGS. 9A and 9B  illustrate side and cutaway views of a small footprint connector in accordance with the present invention; 
         FIGS. 10A and 10B  illustrate side and top views of a small footprint connector connecting multiple LED lamps to a printed circuit board; and 
         FIG. 11  illustrates a perspective view of a further connector for connecting multiple lamps. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 2  illustrates a connector and mounting arrangement in accordance with a first embodiment of the present invention. It shows a packaged LED lamp  200  with multiple top contacts  202 ,  204 ,  206 ,  208 ,  210  and  212  shown in dashed lines. The lamp  200  further comprises a lens  222  and a mounting substrate  226  which may suitably be a printed circuit board (PCB), such as a flame resistant  4  (FR 4 ) board. The arrangement  200  may also be referred to as an LED, LED lamp or a lamp. The lamp  200  includes three strings of LED chips  224 . Each string of LEDs has a cathode and anode contact comprising a pair of the contacts  202 - 212 . It will be recognized that single chip LED lamps, multiple chip lamps with all chips at the same wavelength, multiple chip lamps with chips of different wavelengths and lamps with strings of chips all exist so that myriad contact and drive current requirements are presented. As examples, see U.S. application Ser. Nos. 12/154,691 filed May 23, 2008 and 12/288,957 filed Oct. 28, 2008, which are assigned to the assignee of the present application, and incorporated by reference herein in their entirety. The present invention provides flexibility in adapting to the many existing arrangements, and for adapting as future designs evolve. 
     The lamp  200  is shown mounted on a larger printed circuit board  250  which is shown cutaway in  FIG. 2  for ease of illustration. A connector  270  connects the contacts  202 - 212  to respective electrical connections or traces  252 ,  254 ,  256 ,  258 ,  260  and  262  on the printed circuit board  250  utilizing conductive connections  253 ,  255 ,  257 ,  259 ,  261  and  263  which are part of the connector  270 . Connector  270  may suitably comprise a flexible or moldable material that can be modified or manufactured to include electrical connections suitable for carrying the current needed by the lamp or lamps utilized by an application. Other examples are a stiff metal bent or otherwise shaped as needed with electrically isolated connectors thereon. Heat resistive plastic or ceramic with electrically isolated conductive traces may also be employed. 
     As shown in  FIG. 2 , the connector  270  is reflow soldered to both the contacts of the lamp  200  and the traces of the printed circuit  270  in a single step after board  226  of lamp  200  has been reflow solder mounted to the printed circuit board  270 . Several advantages can result from employing this approach of the present invention. First, because top contacts are employed for electrical connection of the lamp  200 , the entire bottom surface of board  226  can be employed for thermal dissipation. By contrast, when the bottom contacts shown in  FIG. 1C  are employed, electrical isolation strips  113  and  115  isolate the electrical contacts  114  and  116  from thermal pad  119  effectively reducing the surface area employed for thermal dissipation. Second, the single connector  270  eliminates the need for soldering multiple individual connecting wires or packages of wires. 
     As an alternative to the arrangement shown in  FIG. 2 , as seen in  FIG. 3A , a connector  370  can be premounted on a substrate  350  so that a connector-substrate package is formed. By adding a bend downward in arm  372  of connector  370  which ends in an upward curve  374 , a spring tension can be generated which will help physically hold a lamp, such as lamp  200  on the substrate  350 . The curve  374  also helps guide the lamp  200  so it slides into place under arm  372 . As so designed, the connector is effectively a spring providing mechanical stability and reliable electrical contact. In some instances, such as building test samples to test a lamp, it will be recognized that a thermal paste may be employed between a lamp to be tested and the printed circuit board  350  to provide effective thermal dissipation, but the lamp may be simply held in place by the spring force provided by connector  370  rather than reflow soldered in place. Such an arrangement allows for ready replaceability of lamps, upgradeability, and the like.  FIGS. 3B  and  3 C show bottom views of arms  371  and  372  of connector  370  with illustrative solder pads preformed or pre-reflowed thereon. 
     As a further alternative to the arrangement shown in  FIG. 2 , as seen in  FIG. 4 , a connector  470  can be premounted on a substrate  426  of a lamp  400  so that a connector-lamp package is formed.  FIG. 4  illustrates an array of chips  420  connected in three strings as discussed above in connection with  FIG. 2 . Among its several advantages, this mounting arrangement of  FIG. 4  can be utilized to mount a smaller lamp on a landing pad on a presently printed circuit board for a larger lamp by extending the contacts outwardly from the lamp to meet existing power traces, as seen in  FIG. 8 , for example. 
     While  FIG. 2  illustrates an arrangement in which multiple contacts  202 - 212  are connected to multiple traces  252 - 262 , the present invention also provides a ready technique for connecting multiple contacts  502 ,  504  and  506  of a lamp  500  to a single trace  552  on a printed circuit board  550  or for connecting a single contact  508  to multiple traces  554 ,  556  and  558  on the printed circuit board  550  as illustrated in  FIG. 5 . This approach serves the general purpose of moving wiring complexity off the printed circuit board or off the LED lamp board and onto the connector. More particularly, the multiple lamp contacts to one printed circuit board trace connection is advantageously employed where it is desired to drive three different LEDs or strings of LEDs with the same drive current. In a similar vein, the single lamp contact to multiple printed circuit board traces connections is advantageously employed where it is desired to drive the same LED or string of LEDs with a different drive current to achieve different lighting effects. In an alternative embodiment, the adaptive connector of the present invention can be used to connect M contacts on a board  550  to N contacts on an LED lamp where M and N are greater than or equal to one and M is not equal to N. Depending on the embodiment, M can be equal to N. 
       FIG. 6  shows a further arrangement in which an LED lamp  600  has four cathodes  601 ,  603 ,  605  and  607  and four anodes  602 ,  604 ,  606  and  608  are interleaved and a connector  670  serves to simplify the trace arrangement on printed circuit (PCB) board  650  by deinterleaving them so that the cathodes connect to one trace  652  and the anodes connect to one trace  654  on PCB  650 . 
       FIG. 7  shows a further arrangement in which an LED lamp  700  has two contacts  702  and  704  connected by electrical connectors  772  and  774  in a connector  770  to electrical traces  752  and  754  on a PCB  750 . In this embodiment, arm  780  of connector  770  has been extended in size to increase the mechanical support of lamp  700 . In addition, an insert  785  has been provided to increase the thermal dissipation of heat from lamp  700 . Insert  785  may suitably be aluminum, copper or another material with good heat dissipation properties. While an approach utilizing an insert is described, that approach is exemplary of a wide range of approaches to utilize a connector, such as the connector  770  to provide additional heat dissipation. 
     As shown in  FIG. 8 , two connectors  870  and  875  can be utilized to adapt an LED lamp  800  with a given footprint to fit an existing printed circuit board  850  designed for another LED device. More particularly, LED lamp  800  has a smaller footprint than the LED lamp for which board  850  was originally designed. For example, an LED lamp having a ceramic submount with top side contacts can be converted into or at least compatible with an LED package having leads, such as would be used in a lead frame based LED lamp with a molded plastic body encapsulating the lead frame with extended leads. Alternatively, lead frame based LED lamp package with molded plastic body can be converted into or be compatible with a LED package having top side contacts. As would be understood by one of ordinary skill in the art with the benefit of this disclosure, other conversions between different style packages is possible. 
     As seen in  FIG. 8 , connectors  870  and  875  extend from contacts  803  and  805  on the smaller footprint LED lamp  800  to an existing set of traces  852 ,  854 ,  856  and  858  on the printed circuit board  850  originally designed for the larger LED. In this embodiment, the two connectors  870  and  875  may be reflow soldered to the LED lamp  800  to form a connector-lamp package which is then in turn reflow soldered to the PCB  850  and the traces  852 - 856  for contexts such as a high throughput manufacturing environment. 
     Alternatively, in a context such as a device demonstration or evaluation environment, the connectors  870  and  875  may be reflow soldered to the PCB  850  to foam a connector-board package, and with the spring arrangement illustrated in  FIG. 3 , for example, the LED lamp  800  may simply be slid into place beneath the connectors  870  and  875  with the spring force downward from these connectors ensuring good mechanical and electrical contact. 
     Such an arrangement advantageously allows the devices with similar footprints and electrical contacts to be compared in a first one and them the other test so viewers can gauge the performance of the two. With a smaller LED lamp, the approach allows a side by side comparison with larger LED lamps utilizing the same board without the need to make up a different board with different electrical traces. 
       FIGS. 9A and 9B  illustrate side and cutaway views of a further connector  970  having a small footprint. 
       FIGS. 10A and 10B  illustrate side and top views of a two sided connector  1070  for connecting multiple lamps  1000   1-N  and  1001   1-N  utilizing the one connector  1070  in accordance with the present invention resulting in a dramatic reduction in connectors as compared with one or more per lamp. As seen in  FIG. 10A , lamps, such as lamps  1000   1 , and  1001   1 , having substrates  1026 , and  1027 , are located on either side of the connector  1070  with their electric contacts connected to corresponding contacts on a printed circuit board (PCB)  1050  by the connector  1070 . As illustrated in  FIG. 10B , by extending the length of the connector  1070 , a number of lamps, N, can be connected to the PCB  1050  thereby. 
       FIG. 11  illustrates a connector and mounting arrangement in accordance with a further embodiment of the present invention.  FIG. 11  shows an arrangement with mirrored left and right halves. For ease of illustration only the right half is shown in detail. Right half of  FIG. 11  comprises packaged LED lamps  1100   1 - 1100   N  (collectively  1100 ) with multiple top contacts  1102   1 - 1102   N ,  1104   1 - 1104   N ,  1106   1 - 1106   N ,  1108   1 - 1108   N ,  1110   1 - 1110   N , and  1112   1 - 1112   N  (collectively  1102 - 1112 ) shown in dashed lines. Lamps  1100   1 - 1100   N  further comprise lenses and mounting substrates  1126   1 - 1126   N  (collectively  1126 ) which may suitably be a printed circuit board (PCB), such as a flame resistant  4  (FR 4  board). Each lamp may include three strings of LED chips. Each string of LEDs has a cathode and anode contact comprising a pair of the contacts  1102 - 1112 . It will be recognized that single chip LED lamps, multiple chip lamps with all chips at the same wavelength, multiple chip lamps with chips of different wavelengths and lamps with strings of chips all exist so that myriad contact and drive current requirements are presented. The present invention provides flexibility in adapting to the many existing arrangements, and for adapting as future designs evolve. 
     The lamps  1100   1 - 1100   N  are shown mounted on a larger printed circuit board  1150  which is shown cutaway in  FIG. 11  for ease of illustration. A connector  1170  connects the contacts  1102 - 1112  to respective electrical connections, contacts, pads or traces  1154  and  1160  on the printed circuit board  1150  utilizing conductive connections  1153   1-N ,  1155   1-N ,  1157   1-N ,  1159   1-N ,  1161   1-N , and  1163   1-N  (collectively  1153 - 1163 ) which are part of the connector  1170 . Connector  1170  may suitably comprise a flexible or moldable material that can be modified or manufactured to include electrical connections suitable for carrying the current needed by the lamp or lamps utilized by an application. Other examples are a stiff metal bent or otherwise shaped as needed with electrically isolated connectors thereon. Heat resistive plastic or ceramic with electrically isolated conductive traces may also be employed. 
     While the arrangement of  FIG. 11  shows all strings of LEDs sharing common drive signals, it will be recognized that the present invention can be readily applied to individual drive currents for each string as discussed above. 
     While the present invention has been disclosed in the context of various aspects of a number of exemplary embodiments, it will be recognized that the invention may be suitably applied to other environments and adapted to other contexts consistent with the claims which follow. By way of example, while the present invention has been disclosed primarily in the context of exemplary LEDs and mounting arrangements, it will be recognized that the present teachings may be readily adapted to other LEDs and mounting arrangements, as well as, other lighting emitting devices, such as other light emitting semiconductor or solid state devices, such as laser diodes, and optoelectronic device chips, such as phototransistors and the like, by way of example. As one example, while examples of multiple contacts on one or more LED lamps are shown connected to one or more contacts on a printed circuit board and multiple contacts on a printed circuit board are shown connected to one or more contacts on one or more LED lamps, it will be recognized that the approach can be generalized to arrangements for connecting M×N contacts as needed in a particular lighting application. Further, while presently preferred materials and arrangements of exemplary LEDs are described herein with examples of materials and exemplary connections, other materials and connections may be provided to address the needs of particular lighting environments.