Abstract:
Provided is a light emitting semiconductor device comprising a flexible dielectric layer, a conductive layer on at least one side of the dielectric layer, at least one cavity or via in the dielectric substrate, and a light emitting semiconductor supported by the cavity or via. Also provided is a support article comprising a flexible dielectric layer, a conductive layer on at least one side and at least one cavity or via in the dielectric substrate. Further provided is a flexible light emitting semiconductor device system comprising the above-described light emitting semiconductor device attached to the above-described support article.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a national stage filing under 35 U.S.C. 371 of PCT/US2012/049889, filed Aug. 8, 2012, which claims priority to Provisional Application No. 61/524,646, filed Aug. 17, 2011, and Provisional Application No. 61/665,780, filed Jun. 28, 2012, the disclosures of which is incorporated by reference in its/their entirety herein. 
    
    
     TECHNICAL FIELD 
     This invention relates to flexible high power light emitting semiconductor devices. 
     BACKGROUND 
     Conventional light emitting semi-conductor (LES), including light emitting diodes (LEDs) and laser diodes, and LES devices (LESD) and packages containing LESDs have several drawbacks. High power LESDs generate a substantial amount of heat that must be managed. Thermal management deals with problems arising from heat dissipation and thermal stresses, which is currently a key factor in limiting the performances of light-emitting diodes. 
     In general, LES devices are commonly prone to damage caused by buildup of heat generated from within the devices, as well as heat from sunlight in the case of outside lighting applications. Excessive heat buildup can cause deterioration of the materials used in the LES devices, such as encapsulants for the LESDs. When LESDs are attached to flexible-circuit laminates, which may also include other electrical components, the heat dissipation problems are greatly increased. 
     When LESDs are packaged into sub-mount devices, which are then attached to secondary driver systems such as metal core PCB (MPCB), metal insulated substrate (MIS), Bergquist thermal boards, COOLAM substrates, etc., the thermal performance of the submount depends on the thermal resistance of each element in the structure including the sub-mount device, the secondary driver, and the heat sink. In many cases, the secondary driver limits the thermal performance of sub-mount device. Consequently, there is a continuing need to improve the design of support articles and packages to improve their thermal dissipation properties. 
     SUMMARY 
     At least one aspect of the present invention provides a cost-effective thermal management solution for current and future high power LESD constructions through a robust flexible LESD construction. The ability to dissipate large amounts of heat is needed for the operation of high power LESD arrays. According to at least one embodiment of the present invention, heat dissipation can be managed by integrating the LESDs into a system having a flexible dielectric layer that employs a via or cavity to accomplish better heat management. In at least some embodiment of the present invention, to create the vias or cavities, etching through (for vias) or into (for cavities) the dielectric layer is performed. 
     At least one embodiment of the present invention provides a light emitting semiconductor device Z comprising a flexible dielectric layer having a first major surface with a first conductive layer thereon and having a second major surface with a second conductive layer thereon, the dielectric layer having one or both of a first and second via extending through the dielectric layer and a cavity or a third via extending from the first surface to, or toward, the second surface of the dielectric layer, the first conductive layer comprising conductive features in electrical contact with one or both of the first and second vias, the cavity or third via at least partially filled with conductive material the second conductive layer comprising conductive features in electrical contact with one or both of the first and second vias; the cavity, or third via, being configured to receive a light emitting semiconductor. In at least one embodiment, one or both of the first and second vias may be hollow plated vias. In at least one embodiment, the second conductive layer may further comprise a conductive feature aligned with the third via or cavity. In at least one embodiment, the conductive features of the second layer may extend under at least a portion of the third via or cavity and are electrically isolated from each other. 
     At least on embodiment of the present invention provides a support article Y comprising a flexible dielectric layer having a first major surface and having a second major surface with a conductive layer thereon, the dielectric layer having at least two adjacent cavities or vias extending from the first major surface toward, or to, the second major surface, the two or more cavities or vias each configured to receive one or more bottom contacts of an LES package mounted on the support article, wherein contacts received by a single cavity or via have the same, or a neutral, polarity. In at least one embodiment, the conductive layer on the second major surface of the dielectric layer comprises a conductive feature disposed beneath each via. In at least one embodiment, the first major surface of the dielectric layer has a conductive layer thereon. In at least one embodiment, the conductive layer on the first major surface of the dielectric layer extends into the cavities or vias. In at least one embodiment, the cavities or vias contain conductive material. 
     At least on embodiment of the present invention provides a flexible LESD system X comprising an embodiment of light emitting semiconductor device Z and an embodiment of support article Y wherein the conductive features of the second conductive layer of the light emitting semiconductor device make one or both of electrical and thermal connections in the cavities or vias of the support article. 
     At least on embodiment of the present invention provides a flexible LESD system V comprising an embodiment of light emitting semiconductor device Z and an embodiment of a support article comprising a flexible dielectric layer having a first major surface with a first conductive layer thereon and having a second major surface, the dielectric layer having at least one cavity, or via, extending from the second major surface toward, or to, the first major surface, the at least one cavity, or via, containing conductive material, the first conductive layer comprising a first conductive feature disposed atop the cavity, or via, and at least one second conductive feature disposed adjacent the first conductive feature. In at least one embodiment, a cavity, or via, containing conductive material is disposed under the at least one second conductive feature of the support article. In at least one embodiment, the second major surface of the flexible dielectric layer of the support article has a second conductive layer thereon. 
     At least on embodiment of the present invention provides a flexible LESD system U comprising an embodiment of light emitting semiconductor Z and an embodiment of a support article comprising a flexible dielectric layer having a first major surface with a first conductive layer thereon and having a second major surface with a second conductive layer thereon, the dielectric layer having at least one cavity or via extending from the first major surface toward, or to, the second major surface and containing conductive material that form at least two electrically isolated conductive features. In at least one embodiment, one or both conductive features of the light emitting semiconductor device comprises a protrusion and at least one of the electrically isolated features comprises an indentation configured to receive the protrusion of the light emitting semiconductor device. 
     Additional embodiments of the present invention are described in the following paragraphs. 
     Embodiment A 
     At least one aspect of the present invention provides a light emitting semiconductor device comprising a flexible dielectric layer having a first major surface with a first conductive layer thereon and having a second major surface with a second conductive layer thereon, the dielectric layer having two vias extending through the dielectric layer and a third via, or a cavity, extending from the first surface to, or toward, the second surface of the dielectric layer, the first conductive layer comprising conductive pads in electrical contact with each of the two vias, the first conductive layer further extending into the third via, or cavity, the second conductive layer comprising conductive pads in electrical contact with each of the two vias and optionally a conductive feature aligned with the via opening in the second surface, or with the cavity floor; the cavity, or via, being optionally filled with conductive material; and a light emitting semiconductor in the via, or cavity. All or a portion of the two vias may comprise hollow plated vias. The third via or cavity may contain conductive material in addition to the conductive material comprising the conductive layer that extends into the third via or cavity. 
     Embodiment B 
     At least one aspect of the present invention provides a support article comprising a flexible dielectric layer having a first major surface with a first conductive layer thereon and having a second major surface, the dielectric layer having at least one cavity, or via, extending from the second major surface toward, or to, the first major surface, the at least one cavity, or via, containing conductive material, the first conductive layer comprising a conductive feature disposed atop the cavity, or via, and conductive pads disposed adjacent the conductive feature. 
     Embodiment C 
     At least one aspect of the present invention provides a support article comprising a flexible dielectric layer having a first major surface with a first conductive layer thereon and having a second major surface, the dielectric layer having three cavities, or vias, extending from the second major surface toward, or to, the first major surface, the three cavities, or vias, containing conductive material, the first conductive layer comprising a conductive feature disposed atop one cavity, or via, and conductive pads disposed adjacent the conductive feature and atop the other two cavities, or vias. 
     Embodiment D 
     At least one aspect of the present invention provides a support article comprising a flexible dielectric layer having a first major surface with a first conductive layer thereon and having a second major surface, the dielectric layer having two cavities, or vias, extending from the second major surface toward, or to, the first major surface, the two cavities, or vias, containing conductive material, the first conductive layer comprising a conductive pads disposed atop each cavity, or via. 
     Embodiment E 
     At least one aspect of the present invention provides a support article comprising a flexible dielectric layer having a first major surface with a first conductive layer thereon and having a second major surface, the dielectric layer having one cavity and one via, extending from the second major surface toward, or to, the first major surface, the cavity and via containing conductive material, the first conductive layer comprising a conductive pads disposed atop each of the cavity and the via. 
     Embodiment F 
     At least one aspect of the present invention provides a support article comprising a flexible dielectric layer having a first major surface with a first conductive layer thereon and having a second major surface, the dielectric layer having one cavity, or via, extending from the second major surface toward, or to, the first major surface, the cavity, or via, containing conductive material, the first conductive layer comprising two conductive pads, one of which is disposed atop the cavity, or via. 
     Embodiment G 
     At least one aspect of the present invention provides a support article comprising a flexible dielectric layer having a first major surface with a first conductive layer thereon and having a second major surface with a second conductive layer thereon, the dielectric layer having two cavities, or vias, extending from the first major surface toward, or to, the second major surface; the first conductive layer extending into the two cavities, or vias; and the two cavities, or vias, optionally containing additional conductive material. 
     Embodiment H 
     At least one aspect of the present invention provides a support article comprising a flexible dielectric layer having a first major surface with a first conductive layer thereon and having a second major surface with a second conductive layer thereon, the dielectric layer having two cavities, or vias, extending from the second major surface toward, or to, the first major surface; the second conductive layer extending into the two cavities, or vias; the two cavities, or vias, optionally containing additional conductive material; and the first conductive layer comprising a conductive pad disposed atop each of the cavities, or vias. 
     Embodiment I 
     At least one aspect of the present invention provides a support article comprising a flexible dielectric layer having a first major surface with a first conductive layer thereon and having a second major surface with a second conductive layer thereon, the dielectric layer having at least one cavity, or via, extending from the first major surface toward, or to, the second major surface; the first conductive layer extending into the at least one cavity, or via; and the at least one cavity, or via, containing a conductive feature and two conductive pads, the conductive pads electrically insulated from each other and from the conductive feature. 
     Embodiment J 
     At least one aspect of the present invention provides a flexible LESD system comprising the light emitting semiconductor device of Embodiment A and the support article of Embodiment B or C wherein the conductive pads of the second conductive layer of the flexible light emitting semiconductor device are electrically and thermally connected to the conductive pads of the first conductive layer of the support article and the conductive feature of the second conductive layer of the light emitting semiconductor device is thermally connected to the conductive feature of the first conductive layer of the support article. 
     Embodiment K 
     At least one aspect of the present invention provides a flexible LESD system comprising the light emitting semiconductor device of Embodiment A and the support article of Embodiments D, E, F, or H wherein the conductive pads of the second conductive layer of the light emitting semiconductor device are one or both of electrically and thermally connected to the conductive pads of the first conductive layer of the support article. 
     Embodiment L 
     At least one aspect of the present invention provides a flexible LESD system comprising the light emitting semiconductor device of Embodiment A and the support article of Embodiment G wherein the conductive pads of the second conductive layer of the light emitting semiconductor device are one or both of electrically and thermally connected to the conductive material in the cavities, or vias, of the support article. 
     Embodiment M 
     At least one aspect of the present invention provides a system comprising the light emitting semiconductor device of Embodiment A and the support article of Embodiment I wherein the conductive pads of the second conductive layer of the light emitting semiconductor device are electrically and thermally connected to the conductive pads of the first conductive layer of the support article and the conductive feature of the second conductive layer of the light emitting semiconductor device is thermally connected to the conductive feature of the first conductive layer of the support article. 
     Embodiment N 
     At least one aspect of the present invention provides a light emitting semiconductor device comprising a flexible dielectric layer having a first major surface with a first conductive layer thereon and having a second major surface with a second conductive layer thereon, the dielectric layer having a cavity, or via, extending from the first major surface toward, or to, the second major surface of the dielectric layer, the first conductive layer extending into the cavity, or via; the cavity, or via, being optionally filled with additional conductive material; and a light emitting semiconductor in the cavity, or via. 
     Embodiment O 
     At least one aspect of the present invention provides a support article comprising a flexible dielectric layer having a first major surface with a first conductive layer thereon and having a second major surface with a second conductive layer thereon, the dielectric layer having at least one cavity, or via, extending from the first major surface toward, or to, the second major surface; the first conductive layer extending into the at least one cavity, or via; the at least one cavity, or via, optionally containing additional conductive material. 
     Embodiment P 
     At least one aspect of the present invention provides a flexible LESD system comprising the light emitting semiconductor device of Embodiment N and the support article of Embodiment O wherein the second conductive layer of the light emitting semiconductor device are one or both of electrically and thermally connected to the conductive material in the cavities, or vias, of the support article. 
     Embodiment Q 
     At least one aspect of the present invention provides a light emitting semiconductor device of Embodiment N further comprising protrusions extending from the second conductive layer. 
     Embodiment R 
     At least one aspect of the present invention provides a support article of Embodiment O further comprising indentation in conductive layer or conductive material in the cavity, or via. 
     Embodiment S 
     At least one aspect of the present invention provides a flexible LESD system comprising the light emitting semiconductor device of Embodiment Q and the support article of Embodiment R, wherein the protrusions extending from the second conductive layer of the light emitting semiconductor device fit into the indentation in the conductive layer or conductive material in the cavity, or via, of the support article. 
     As used in this application: 
     “LES” means light emitting semiconductor(s), including light emitting diodes and laser diodes; 
     “LESD” means light emitting semiconductor devices, including light emitting diode device(s) and laser diode device(s); an LESD may be a bare LES die construction, a complete packaged LES construction, or an intermediate LES construction comprising more than the bare die, but less than all the components for a complete LES package, such that the terms LES and LESD may be used interchangeably and refer to one or all of the different LES constructions; a “discrete LESD” typically refers to one or more LESDs that are “packaged” and ready to function once connected to an electrical source, such as driving circuits including MCPCBs, MISs, etc. Examples of discrete LESDs that may be suitable for use in embodiments of the present invention Golden DRAGON LEDs, available from OSRAM Opto Semiconductors GmbH, Germany; LUXEON LEDs, available from Philips Lumileds Lighting Company, USA; and XLAMP LEDs, available from Cree, Inc., USA, as well as the discrete LESDs described herein and similar devices. 
     “support article” means a circuitized flexible article to which one or more discrete LESDs are attached; commercially available alternatives to the support article of the present invention may include metal core printed circuit boards (MCPCBs), metal insulation substrates (MIS), Bergquist thermal boards, and COOLAM thermal substrates; 
     “flexible LESD” typically refers to a support article having one or more attached discrete LESD. 
     An advantage of at least one embodiment of the present invention is: 
     Using the support article of the present invention with a discrete LESD can reduce the overall thermal resistance of light emitting device. 
     Using the support article of the present invention with discrete LESDs can allow for quick and cost-effective repair in that, e.g., individual defective LESDs may be easily detached and removed from the vias or cavities and replaced with new LESDs. 
     The vias and cavities of the present invention containing conductive material provide excellent Z-axis thermal conductivity. 
     The size of the vias and cavities and the surface area of the conductive layers can be tailored to provide optimized thermal resistance values. 
     The vias and cavities can be designed to accommodate various LESD electrical contacts. 
     The use of a support article of the present invention with LESDs can eliminate the cost associated with conventional LED submounts. 
     The flexible LESDs of the present invention can provide a robust, cost-effective thermal management solution for current and future high power LESD constructions. 
     The above summary of the present invention is not intended to describe each disclosed embodiment or every implementation of the present invention. The Figures and detailed description that follow below more particularly exemplify illustrative embodiments. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  depicts an embodiment of a support article of the present invention. 
         FIGS. 2A-2E  depict a process for preparing a support article of the present invention. 
         FIG. 3  depicts an embodiment of a support article of the present invention. 
       FIGS.  4  and  4 ′ depict embodiments of LESDs of the present invention. 
         FIG. 5  depicts an embodiment of an LESD of the present invention attached to an embodiment of a support article of the present invention. 
         FIG. 6  depicts an embodiment of a support article of the present invention. 
         FIG. 7  depicts an embodiment of a support article of the present invention. 
         FIG. 8  depicts an embodiment of a support article of the present invention. 
         FIGS. 9A-9B  depict embodiments of support articles of the present invention. 
         FIGS. 9C-9D  depict embodiments of an LESD of the present invention attached to embodiments of support articles of the present invention. 
         FIGS. 10A-10B  depict embodiments of support articles of the present invention. 
         FIGS. 10C-10D  depict embodiments of an LESD of the present invention attached to embodiments of support articles of the present invention. 
       FIGS.  11 A and  11 A′ depict embodiments of LESDs of the present invention 
         FIG. 11B  depicts an embodiment of a support article of the present invention. 
         FIG. 11C  depicts an embodiment of an LESD of the present invention attached to an embodiment of a support article of the present invention. 
       FIGS.  12 A and  12 A′ depict embodiments of LESDs of the present invention. 
         FIG. 12B  depicts an embodiment of a support article of the present invention. 
         FIG. 12C  depicts an embodiment of an LESD of the present invention attached to an embodiment of a support article of the present invention. 
         FIG. 13A  depicts an embodiment of a support article of the present invention. 
         FIG. 13B  depicts an embodiment of an LESD of the present invention. 
         FIG. 13C  depicts an embodiment of an LESD of the present invention attached to an embodiment of a support article of the present invention. 
         FIG. 14  depicts an embodiment of a support article of the present invention with an LESD attached. 
         FIG. 15  depicts an embodiment of a support article of the present invention with an LESD attached. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, reference is made to the accompanying set of drawings that form a part of the description hereof and in which are shown by way of illustration several specific embodiments. It is to be understood that other embodiments are contemplated and may be made without departing from the scope or spirit of the present invention. The following detailed description, therefore, is not to be taken in a limiting sense. 
     Unless otherwise indicated, all numbers expressing feature sizes, amounts, and physical properties used in the specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the foregoing specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by those skilled in the art utilizing the teachings disclosed herein. The use of numerical ranges by endpoints includes all numbers within that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5) and any range within that range. 
     Unless otherwise indicated, the terms “coat,” “coating,” “coated,” and the like are not limited to a particular type of application method such as spray coating, dip coating, flood coating, etc., and may refer to a material deposited by any method suitable for the material described, including deposition methods such vapor deposition methods, plating methods, coating methods, etc. 
     Exemplary embodiments of the present invention as described herein may pertain to a support article comprising vias, which extend all the way through the dielectric layer, thereby forming an opening through the dielectric layer. Alternatively, in some embodiments of the support articles of the present invention, the dielectric layer is not etched all the way through, so that a cavity, having one open end and one closed end, is formed. If this is done, the remaining dielectric material is preferably thin, e.g., up to about 20% to about 30% of the thickness of the dielectric layer. For a dielectric layer having a thickness of about 50 micrometers, a suitable thickness for the remaining dielectric layer is up to about 10 to 15 micrometers (about 20% to about 30% of the total dielectric thickness), in some embodiments, preferably about 1 to about 5 microns, so that it will not significantly inhibit heat transfer. It may be desirable to retain this thin layer of dielectric material, for example, to provide structural integrity, to manage CTE mismatches of adjacent material, or to provide an electrical barrier between electrically conductive feature or layers. Throughout this description, it is intended that all embodiments described with vias have equivalent embodiments with cavities, and vice versa, unless such an alternate embodiment would be physically impossible. When substituting a via for a cavity, or more particularly when substituting a cavity for a via, modifications to the embodiments may be required to establish suitable electrical connections and paths. In at least some embodiments of the present invention, the conductive material within a cavity or via may comprise in whole or in part a portion of a conductive layer that extends from a surface of the flexible dielectric layer into the cavity or via. 
     Although the embodiments herein typically describe a single LESD or a single site on a support article for attaching an LESD, it is to be understood that the invention covers multiple LESDs and support articles with multiple sites for attaching LESDs. Additionally, the embodiments herein may include additional cavities or vias throughout the dielectric layer, for example, adjacent to the attached LESDs, to provide additional heat dissipation features. 
     Any suitable dielectric layer material may be used to form an embodiment of the present invention having a cavity in place of a via. Suitable methods for forming cavities include essentially the same methods as for forming a via except that methods that cannot be controlled sufficiently to leave a remaining layer of unetched dielectric material are not suitable. 
     At least one embodiment of a support article  2  of the present invention is illustrated in  FIG. 1 , which shows a flexible dielectric layer  12  having at least one via  10  filled with conductive material  20 , which may be copper or other conductive materials. Via  10  extends through dielectric layer  12  and may be any suitable shape, e.g., circular, oval, rectangular, serpentine, a channel, a grid (e.g., forming islands of dielectric layer separated by a continuous pattern of overlapping channels), etc. For example, if the via is channel-shaped or grid-shaped, a continuous path of conductive material  20  can be located within the outer confines of dielectric layer  12 . The flexible dielectric layer  12  has first and second major surface. Top conductive layer  17  is disposed on the first major surface of dielectric layer  12  and may be patterned to include a conductive feature  22 , which may be an electrically isolated conductive feature, on which feature LESD  24  is disposed. LESD  24  can be attached, directly, or indirectly, to conductive feature  22  using a known die bonding method such as eutectic, solder, adhesive, and fusion bonding. LESD  24  may be wire bonded through conductive pads  26  and  28  to electrically conductive circuits also patterned in top conductive layer  17 . In at least some embodiments of the invention, conductive pads  26 ,  28  (as well as  426 ,  426 ′,  428 , and  428 ′) are a particular type of conductive feature. They may be patterned features of top or bottom conductive layers  16  or  17  and may comprise Cu. Alternatively, they may comprise a different material such as Au, AuSn, AuGe, or other suitable materials. They typically provide at least an electrical connection and may optionally provide a thermal connection, as opposed to other conductive features, which might only provide a thermal connection in some embodiments. In some embodiments, a passivation or bonding layer is located beneath LESD  24  to facilitate bonding LESD  24  to an underlying layer. In at least one embodiment, thermally conductive layer  30  is attached to the support article adjacent the second major surface of dielectric layer  12 , which brings it into contact with conductive material  20  in via  10 . Thermally conductive layer  30  may be any material that is thermally conductive. For example, conductive substrate may be a thermal interface material (TIM), a metal strip, e.g., of copper or aluminum, a heat sink, or other heat transferring or heat absorbing material. Thermally conductive layer  30  may be attached to the support article using a thermally conductive adhesive. The juxtaposition of conductive feature  22 , conductive material  20  in via  10 , and thermally conductive layer  30  allows for efficient dissipation of heat generated by the LESD to thermally conductive layer  30 . In addition, the conductive material in via  10  can provide mechanical support for conductive feature  22 , which is essentially suspended over the opening of via  10 . In an alternate embodiment of the present invention, instead of applying thermally conductive layer  30  to conductive material  20 , an adhesive, e.g., a TIM with adhesive properties, on a liner can be applied to the conductive material  20 , so that the support article can be directly applied, at a later time, to a conductive substrate or a heat sink. 
       FIGS. 2A through 2E  show a method of making the support article  2  illustrated in  FIG. 1 . Top conductive layer  17  is applied and patterned on a first side of flexible dielectric layer  12  ( FIG. 2A ), then via  10  is formed in flexible dielectric layer  12 , extending from a second side to the first side of flexible dielectric layer  12  ( FIG. 2B ), a photoresist mask is applied over top conductive layer  17 , except for the portion exposed by via  10  ( FIG. 2C ), via  10  is filled with conductive material  20 , e.g., by electrodeposition such as electroplating by building up conductive material on the surface of the conductive layer facing the via ( FIG. 2D ), and the photoresist layer is removed ( FIG. 2E ). 
       FIG. 3  is an alternate embodiment of the support article of  FIG. 1 . The support article  2  of  FIG. 3  has two additional vias  36  and  38  extending through dielectric layer  12  beneath conductive pads  26  and  28  and are filled with conductive material  20 , which may be copper or other conductive materials. These vias can acts as both electrodes and heat transfer channels. If the support article has cavities in place of vias  36  and  38 , the cavities can act as heat transfer channels, but would not act as electrodes because they would be insulated from conductive pads  26  and  28  by a thin layer of dielectric material. 
       FIG. 4  illustrates an embodiment of an LESD  24  that may be used with the support article  2  of  FIG. 1 . LESD  24  has many of the same or similar components as support article  2 . The flexible dielectric layer  412  has first and second major surface. Vias  410 ,  436 , and  438  extend through dielectric layer  412  from the first to second surfaces and may be any suitable shape. Vias  410 ,  436 , and  438  may be fully filled, as shown, or partially filled with conductive material  420 , which may be copper or other suitable conductive materials. Top conductive layer  417  is disposed on the first major surface of dielectric layer  412  and bottom conductive layer  416  is disposed on the second major surface of flexible dielectric layer  412 . Conductive layer  416  may be patterned to include a conductive feature  422 , which may be an electrically isolated conductive feature, and conductive features  430  and  432 , which may be electrically connected to conductive pads  426  and  428  through vias  436  and  438 , respectively. LES  424  can be attached, directly, or indirectly (e.g., through conductive material  420 ), to conductive feature  422  using a known die bonding method such as eutectic, solder, adhesive, and fusion bonding. Top conductive layer  417  may include conductive pads  426  and  428 . LES  424  may be wire bonded to conductive pads  426  and  428 . Conductive pads  426 ,  428  may comprise Au, AuSn, AuGe, or other suitable materials. In some embodiments, a passivation or bonding layer is located beneath LES  424  to facilitate bonding LES  424  to an underlying layer. 
     FIG.  4 ′ illustrates and LESD  24  similar to the LESD of  FIG. 4  except for several modified features: Vias  436 ′ and  438 ′ have hollow plated vias, i.e., at least a portion of the via has plated walls but is not fully filled with conductive material. Via  410 ′ has conductive material  420  on its walls, but none on conductive feature  422 . This can be accomplished, for example, by creating conductive feature  422  after conductive material  420  is applied to the walls of via  410 ′. Conductive pads  426 ′ and  428 ′ are located at (or around) the top edge of vias  436 ′ and  438 ′. LES  424  sits directly on conductive feature  422 . Bottom conductive layer  416  is optionally thicker than top conductive layer  417 . 
       FIG. 5  illustrates the LESD  24  of  FIG. 4  attached to the support article  2  of  FIG. 1 . In this embodiment, conductive features  430  and  432  are attached by solder  34  to conductive pads  26  and  28 , respectively, to establish an electrical (and thermal) path and conductive feature  422  is attached by solder  34  to conductive feature  22  to establish a thermal path. 
       FIG. 6  illustrates an embodiment of support article  2  having a flexible dielectric layer  12  having two vias  36  and  38  extending therethrough beneath conductive pads  26  and  28 , respectively, formed in top conductive layer  17 . Vias  36  and  38  are filled with conductive material  20 , which may be copper or other conductive materials. These vias can act as both electrodes and heat transfer channels. If the support article has cavities in place of vias  36  and  38 , the cavities can act as heat transfer channels, but would not act as electrodes because they would be insulated from conductive pads  26  and  28  by a thin layer of dielectric material. An optional thermally conductive layer  30 , which may comprise a thermal interface material (TIM) is shown in  FIG. 6 . 
       FIG. 7  illustrates an embodiment of support article  2  similar to that of  FIG. 6  except that there is a via  36  extending through dielectric layer  12  under conductive pad  26  and a cavity  38 ′ under conductive pad  28 . In this configuration, via  36  would be electrically connected to conductive pad  26 , cavity  38 ′ would not be electrically connected to pad  28 , but both would via  36  and cavity  38 ′ would act as heat transfer channels. 
       FIG. 8  illustrates an embodiment of support article  2  similar to that of  FIGS. 6 and 7  except that there is only a via  36  extending through dielectric layer  12  under conductive pad  26 . There is no via or cavity under conductive pad  28 . An optional conductive substrate  30 , e.g., a TIM layer, may be attached to the second surface of dielectric layer  12 . 
       FIGS. 9A and 9B  illustrate embodiments of support article  2  in which the cavities  11  ( FIG. 9A ) or vias  10  ( FIG. 9B ) extend from the first side to the second side of dielectric layer  12 .  FIG. 9A  includes bottom conductive layer  16  on the second surface of dielectric layer  12  and top conductive layer  17  on the first surface of dielectric layer  12 . Top conductive layer  17  is patterned on the first surface of dielectric layer  12  and extends into cavities  11 . Cavities  11  may contain additional conductive material (not shown). Bottom conductive layer  16  may be patterned or unpatterned and is electrically insulated from cavities  11 .  FIG. 9B  includes bottom conductive layer  16  on the second surface of dielectric layer  12  and top conductive layer  17  on the first surface of dielectric layer  12 . Top conductive layer  17  is patterned on the first surface of dielectric layer  12  and extends into vias  10 . Vias  10  extend entirely through dielectric layer  12  and may contain additional conductive material (not shown). Bottom conductive layer  16  is patterned at least to electrically isolate the vias  10  from one another.  FIGS. 9C and 9D  illustrate the support articles  2  of  FIGS. 9A and 9B , respectively, to which LESDs  24  have been attached by solder bonding conductive features  430  and  432  into cavities  11  or vias  10  using solder  34  (shown before reflow). An optional thermally conductive layer (not shown), e.g., a TIM layer, may be attached to bottom conductive layer  16 . The embodiments illustrated in  FIGS. 9C and 9D , in which solder  34  (not shown to scale) is placed in cavities  11  or vias  10  provide the additional advantage of a level solder pad. When the solder in the cavities  11  or vias  10  is reflowed, it is held in place by the walls of the cavities or vias and forms a level surface to which solder bonding features  430  and  432  may be attached (as illustrated in  FIGS. 14 and 15 ). 
       FIGS. 10A and 10B  illustrate embodiments of support article  2  in which the cavities  11  ( FIG. 10A ) or vias  10  ( FIG. 10B ) extend from the second side to the first side of dielectric layer  12 .  FIG. 10A  includes conductive layer  16  on the second surface of dielectric layer  12  and top conductive layer  17  on the first surface of dielectric layer  12 . Bottom conductive layer  16  is patterned on the second surface of dielectric layer  12  and extends into cavities  11 . Cavities  11  may contain additional conductive material (not shown). Top conductive layer  17  is patterned to form conductive pads  26  and  28  to which LESDs may be attached. These conductive pads are electrically insulated from cavities  11 .  FIG. 10B  includes conductive layer  16  on the second surface of dielectric layer  12  and top conductive layer  17  on the first surface of dielectric layer  12 . Conductive layer  16  is patterned on the second surface of dielectric layer  12  and extends into vias  10 . Vias  10  extend entirely through dielectric layer  12  and may contain additional conductive material (not shown). Top conductive layer  17  is patterned to form conductive pads  26  and  28  to which LESDs may be attached. These conductive pads are electrically connected to vias  10 .  FIGS. 10C and 10D  illustrate the support articles  2  of  FIGS. 10A and 10B , respectively, to which LESDs  24  have been attached by solder bonding conductive features  430  and  432  to conductive pads  26  and  28  with solder  34 . An optional thermally conductive layer  30 , e.g., a TIM layer, may be attached to conductive layer  16  and conductive material  32 , e.g., a TIM, may be placed into vias  10  and cavities  11  as illustrated in  FIGS. 10C and 10D . As illustrated in  FIGS. 10C and 10D , if conductive layer  30  comprises conformable material, it may flow into, or be pressed into, cavities  11  or vias  10  thereby allowing the application of conductive layer  30  and conductive material  32  in a single step. Alternatively, conductive material  32  may comprise a different (or the same) material than conductive layer  30  and may be applied in a different step. 
       FIG. 11A  illustrates an embodiment of an LESD of the present invention similar to the LESD of  FIG. 4  except that the LESD  24  of  FIG. 11A  has a cavity  411  instead of a via. FIG.  11 A′ illustrates an embodiment of an LESD  24  of the present invention similar to the LESD of  FIG. 11A  with some exceptions. In FIG.  11 A′, LES  424  has both a top and bottom contact such that only one wire bond is required. Wire bond  408  connects the top contact of LES  424  to conductive pad  426 ′, which is electrically connected to solder bonding features  430  through via  436 ″. The bottom contact of LES  424  is connected to conductive pad  428 ′ through top conductive layer  417  including the portion of top conductive layer  417  extending into cavity  411 . Conductive pad  428 ′ is electrically connected to solder bonding feature  432  through via  438 ″. Vias  436 ″ and  438 ″ comprise in part hollow plated vias, i.e., at least a portion of the via has plated walls but is not fully filled with conductive material. However, in contrast to the hollow plated vias  436 ′ and  438 ′ of FIG.  4 ′, vias  436 ″ and  438 ″ have conductive material filling the bottom portion of the via. This can be accomplished, for example, by applying bottom conductive layer  416  prior to depositing conductive material in the vias. Conductive pads  426 ′ and  428 ′ are located at (or around) the top edge of vias  436 ′ and  438 ′. Bottom conductive layer  416  is optionally thicker than top conductive layer  417 .  FIG. 11B  illustrates an embodiment of support article  2  in which cavity  11  extends from the first to the second surface of dielectric layer  12 , conductive feature  22  is located within cavity  11  and conductive pads  26  and  28  are patterned to extend into cavity  11 . Bottom conductive layer  16  may optionally be on the second surface of dielectric layer  12  and an optional thermally conductive layer  30 , e.g., a layer of TIM (not shown), may optionally be applied to conductive layer  16  and/or the second surface of dielectric layer  12 .  FIG. 11C  illustrates the support article of  FIG. 11B  with LESD  24  of  FIG. 11A  attached to conductive pads  26  and  28  and conductive feature  22  within cavity  11 . In this embodiment, the height of LESD  24  above the height of the support article  2  can be minimized to keep the overall height of the article low. 
       FIG. 12A  illustrates an LESD  224  that may be placed in via  10  of support article  2  of  FIG. 12B . LESD  224  includes cavity  411  that extends from the first to the second surface of dielectric layer  412 . Top conductive layer  417  is patterned on the first surface of dielectric layer  412  and extends into cavity  411 . Bottom conductive layer  416  may optionally be on the second surface of dielectric layer  412 . LES  424  has both a top and bottom contact such that only one wire bond is required. Wire bond  408  connects the top contact of LES  424  to conductive pad  426 , which is electrically connected to solder bonding features  430  through via  466 . The bottom contact of LES  424  is connected to conductive pad  428  through conductive material  420  (e.g., solder or copper) and the portion of top conductive layer  417  extending into cavity  411 . Conductive pad  428  is electrically connected to solder bonding feature  432  through via  468 . A gap  440  separated solder bonding features  430  and  432 . FIG.  12 A′ illustrates an LESD  224  similar to that of the LESD of  FIG. 12A . The LESD of FIG.  12 A′ differs from that of  FIG. 12A  in that it comprises via  410  instead of cavity  411  and there is no via  468  and no solder bonding pad  432 . Instead, the bottom contact of LES  424  is electrically connected to conductive feature  422  (which serves the purpose of missing solder bonding feature  432  in this embodiment) directly through the conductive material  420  (and the portion of top conductive layer  417  extending into via  410 ) located in via  410 .  FIG. 12B  illustrates an embodiment of support article  2  in which via  10  extends from the first to the second surface of dielectric layer  12 . Top conductive layer  17  is patterned on the first surface of dielectric layer  12  and extends into via  10 . Bottom conductive layer  16  may optionally be on the second surface of dielectric layer  12  and a thermally conductive layer (not shown), e.g., a layer of TIM, may optionally be applied to bottom conductive layer  16  and/or the second surface of dielectric layer  12 . A physical gap  40  is formed in bottom conductive layer  16  and the conductive material in via  10  so that the bottom contacts of an LES placed in via  10  will be electrically separated.  FIG. 12C  illustrates LESD  224  of  FIG. 12A  in via  10  of the support article of  FIG. 12B . Gaps  1240  and  40  align. In this embodiment, the height of LESD  224  above the height of the support article  2  can be minimized to keep the overall height of the article low. Optional thermally conductive layer  30  is shown. 
       FIG. 13A  illustrates a modified embodiment of the LESD  224  of  FIG. 12A  having protrusions  440 ,  442  extending from solder bonding features  430 ,  432  of bottom conductive layer  216 , respectively.  FIG. 13B  illustrates a modified embodiment of the support article  2  of  FIG. 12B  in which via  10  includes notches  40 ,  42  for making electrical and mechanical contact with mating protrusions  440 ,  442  of LESD  224 .  FIG. 13C  illustrates LESD  224  of  FIG. 13A  in via  10  of the support article  2  of  FIG. 13B . 
     Although the embodiments of  FIGS. 11C ,  12 C, and  13 C show a single LESD in the cavity or via of the support article, the vias or cavities may be made to hold multiple LESDs. 
       FIG. 14  illustrates an embodiment of support article  2  in which two vias  10  extend from the top surface to the bottom surface of dielectric layer  12 . Bottom conductive layer  16  is on the bottom surface of dielectric layer  12  and there is no conductive layer on the top surface of dielectric layer  12 . Conductive layer  16  is patterned on the bottom surface of dielectric layer  12  and includes conductive features  18 , electrically isolated from each other and two of which are located beneath vias  10 . Vias  10  contain conductive material  20 , which may be, for example, solder. A flip chip LESD  24  is attached to support article  2  by the conductive material  20  in vias  10 . In the illustrated embodiment, a solder mask  21  is applied over conductive layer  16 . A reflective solder mask  22  may optionally be applied to the first surface of support article  2 , including under LESD  24  (not shown). The embodiment of  FIG. 14  illustrates that if conductive material  20  in vias  10  comprises solder paste or other conductive material that can be reflowed, it provides the additional advantage of a level solder pad. When solder in the vias  10  is reflowed, it is held in place by the walls of the vias and forms a level surface to which flip chip LESD  24  may be attached. The two vias  10  act as anode and cathode electrodes for the flip chip LESD  24 . An optional thermally conductive layer, which may comprise a TIM, may be attached to conductive layer  16  instead of, or in addition to, the solder mask. The thermally conductive layer may be used to attach the support article  2  to a substrate such as a flexible metal foil, a rigid metal layer, or a heat sink. These substrates may be made from any suitable material, but are typically copper or aluminum. 
       FIG. 15  illustrates an embodiment of support article  102  in which three vias  110  extend from the top surface to the bottom surface of dielectric layer  112 . Conductive layer  116  is on the bottom surface of dielectric layer  112  and there is no conductive layer on the top surface of dielectric layer  112 . Conductive layer  116  is patterned on the bottom surface of dielectric layer  112  and includes conductive features  118 , electrically isolated from each other and three of which are located beneath vias  110 . Vias  110  contain conductive material  120 , which may be, for example, solder. A flip chip LESD  124  is attached to support article  102  by the conductive material  120  in vias  110 . In the illustrated embodiment, a solder mask  121  is applied over conductive layer  116 . A reflective solder mask  122  may optionally be applied to the first surface of support article  102 , including under LESD  24  (not shown). In the same manner as the embodiment illustrated in  FIG. 14 , if conductive material  120  comprises solder paste or other conductive material that can be reflowed, it provides the additional advantage of a level solder pad. When the solder in the vias  100  is reflowed, it is held in place by the walls of the vias and forms a level surface to which flip chip LESD  124  may be attached. In at least one embodiment of the present invention, the outer vias  110  act as anode and cathode electrodes and the inner via  110  acts as a thermal via to improve heat transfer away from the flip chip LESD  124  through its center contact pad. An optional thermally conductive layer  126 , which may comprise a TIM layer, is attached to solder mask  121 . The thermally conductive layer  126  may be used to attach the support article  2  to a substrate  128  such as a flexible metal foil, a rigid metal layer, or a heat sink. These substrates may be made from any suitable material, but are typically copper or aluminum. 
     Each via  10  and  110  of support articles  2  and  102  of  FIGS. 14 and 15  connects with one contact of an LESD  24  or  124  having to two or more contacts. In some embodiments in which the LESD has, e.g., two contacts having the same polarity or two contacts wherein one contact is electrically neutral, a single via might connect with the two contact, but a second adjacent via will connect to the contact of the LESD having a polarity opposite to the polarity of a contact connected with the first via. 
     Suitable dielectric layers for the present invention include polyesters, polycarbonates, liquid crystal polymers, and polyimides. Polyimides are preferred. Suitable polyimides include those available under the trade names KAPTON, available from DuPont; APICAL, available from Kaneka Texas corporation; SKC Kolon PI, available from SKC Kolon PI Inc.; and UPILEX and UPISEL, available from Ube-Nitto Kasei Industries, Japan. Most preferred are polyimides available under the trade designations UPILEX S, UPILEX SN, and UPISEL VT, all available from Ube-Nitto Kasei Industries. These polyimides are made from monomers such as biphenyl tetracarboxylic dianhydride (BBDA) and phenyl diamine (PDA). In at least one embodiment, the thickness of the dielectric layer is preferably 50 micrometers or less, but may be any thickness suitable for a particular application. 
     The dielectric layers may alternatively be materials such as FR4, depending on the application. 
     The dielectric layers (substrates) may be initially clad on one or both sides with a conductive layer. If the conductive layer(s) are to be formed into circuits, they may be pre-patterned, or may be patterned during the process of making the support articles. A multilayer flexible substrate (having multiple layers of dielectric and conductive material) may also be used as a substrate. The conductive layers may be any suitable material including copper, gold, nickel/gold, silver, and stainless steel, but are typically copper. The conductive layer may be applied in any suitable manner such as sputtering, plating, chemical vapor deposition, or it may be laminated to the dielectric layer or attached with an adhesive. 
     Vias or cavities may be formed in the dielectric layers using any suitable method such as chemical etching, plasma etching, focused ion-beam etching, laser ablation, embossing, microreplication, injection molding, and punching. Chemical etching may be preferred in some embodiments. Any suitable etchant may be used and may vary depending on the dielectric layer material. Suitable etchants may include alkali metal salts, e.g. potassium hydroxide; alkali metal salts with one or both of solubilizers, e.g., amines, and alcohols, such as ethylene glycol. Suitable chemical etchants for some embodiments of the present invention include KOH/ethanol amine/ethylene glycol etchants such as those described in more detail in U.S. Patent Publication No. 2007-0120089-A1, incorporated herein by reference. Other suitable chemical etchants for some embodiments of the present invention include a KOH/glycine etchants such as those described in more detail in co-pending U.S. Provisional Patent Application No. 61/409,791, incorporated herein by reference. Subsequent to etching, the dielectric layers may be treated with an alkaline KOH/potassium permanganate (PPM) solution, e.g., a solution of about 0.7 to about 1.0 wt % KOH and about 3 wt % KMnO4. 
     The side wall angles resulting from chemical etching varies, and is most dependent on etch rate, with slower etching rates resulting in shallower side wall angles. Typical side wall angles resulting from chemical etching are about 5° to about 60°, and in at least one embodiment, about 25° to about 28°. For purposes of this application, a sloped side wall means a side wall that is not perpendicular to the horizontal plane of the dielectric layer. Vias or cavities with sloped sidewalls could also be made using methods such as embossing, microreplication, and injection molding. Vias or cavities having sloped sidewalls may also be made with methods such as punching, plasma etching, focused ion-beam etching, and laser ablation; however, with these methods, the side walls typically have a steeper angle, e.g., up to 90°. 
     Embodiments of the present invention having vias or cavities with sloped side walls may be preferred because, e.g., for a given thickness of dielectric layer and a given via or cavity diameter nearest a conductive feature, a via having sloped side walls can contain more conductive material that a via having 90° side walls. For example, the opening of a via adjacent a conductive feature typically will be limited by the size of that conductive feature; however, by employing sloped via side walls, the opening at the opposing end of the via may be enlarged to an optimum size such that the via can contain a larger amount of conductive material (to transfer more heat away from the LESD) and the conductive at this opening has a large surface area that can interface more effectively with a heat transferring or absorbing material, such as a thermal interface material (TIM) or a metal substrate, which may be attached to the dielectric layer and conductive-filled vias. 
     If the vias in embodiments of the present invention have a conductive layer adjacent one opening, it can be filled with conductive material by electrodeposition, such as electroplating, by building up conductive material on the surface of the conductive layer facing the via. 
     Any suitable TIM may be used in embodiments of the present invention. Depending on the embodiment, the TIM may be applied to the support article as a liquid, paste, gel, solid, etc. Suitable methods for applying TIM depend on the properties of the specific TIM, but include precision coating, dispensing, screen printing, lamination etc. 
     Suitable methods for curing a curable TIM include UV curing, thermal curing etc. 
     The TIM may be coated on, e.g., as a liquid or a semi-solid such as a gel or paste, or may be laminated on in sheet form. A combination of TIMs could be used. For example, in some embodiments, such as those shown in  FIGS. 10C and 10D , a first type of TIM may be applied in the vias or cavities and a second type of TIM may be applied to the second major surface of the dielectric layer, which would bring it into contact with the first type of TIM. In some embodiments, the TIM may also be adhesive-based. In such an embodiment, the TIM could adhere directly to the support article on one side and a conductive substrate on the other. A TIM that does not have adhesive properties could be applied to one or both of the substrate article and the conductive substrate with a thermally conductive adhesive. The TIM may be first applied to the substrate article and a conductive substrate applied to the TIM thereafter, or the TIM may be first applied to a conductive substrate and the TIM-coated conductive substrate applied to the substrate article thereafter. 
     The discrete LESDs can be made in a batch process or a continuous process such as a roll-to-roll process that is often used in making flexible circuits. Arrays of LESDs can be formed in any desired pattern on the flexible substrate. The LESDs can then be divided as desired, e.g., singulated into individual LESDs, strips of LESDs, or arrays of LESDs, e.g., by stamping or by slitting the substrate. Accordingly, an entire reel of LESDs on a flexible substrate can be shipped without the need for the traditional tape and reel process in which individual LESDs are typically transported in individual pockets of a carrier tape. 
     The support articles can also be made in a batch process or a continuous process such as a roll-to-roll process that is often used in making flexible circuits. The support articles can be formed with any desired pattern of LESD attachment sites on the flexible substrate. The support articles can then be divided as desired, e.g., singulated to provide individual LESD attachment sites, strips of LESD attachment sites, or arrays of LESD attachment sites, e.g., by stamping or by slitting the substrate. 
     Before or after forming support articles with individual, strips, or arrays of LESD attachment sites, the support articles can be attached to an additional substrate, for example with a thermally conductive adhesive. The thermally conductive adhesive can further facilitate the transfer of heat away from the LESDs, once attached to the support article. The support articles can be attached to any desired substrate, depending on their intended use. The additional substrate may be thermally and/or electrically conductive or may be a semiconductor, ceramic, or polymeric substrate, which may or may not be thermally conductive. For example, the additional substrates can be flexible or rigid metal substrates, such as copper or aluminum, heat sinks, dielectric substrates, circuit boards, etc. 
     If the flexible LESDs (comprising both the support article and discrete LESDs) are for use as a lighting strip, they could be enclosed in a waterproof/weatherproof, transparent casing, as described above. 
     If the flexible LESDs are in strip or array form, the discrete LESDs may be electrically connected to one or more of the other discrete LESDs in the strip or array. Additional elements such as Zener diodes and Schottky diodes can also be added to the top or bottom surface of the support article, e.g. using direct wafer bonding or flip chip processes. These elements may also be electrically connected to the LESDs. 
     In at least one embodiment of the present invention, the flexible LESs are thinner than conventional single or multiple LESD submounts because the LESD sits in a cavity or via in the support article. This enables the flexible LESDs of the present invention to be used in applications with tight volume restrictions, such as cell phones and camera flashes. For example, the support articles of the present invention can provide a package profile of approximately 0.7 to 4 mm, and in some embodiments 0.5 to 2 mm whereas conventional LESD submount profiles are typically greater than 4 mm and are approximately 4.8 mm to 6.00 mm. Moreover, the support articles of the present invention can be flexed or bent to easily fit into a non-linear or non-planar assembly if desired. 
     Although specific embodiments have been illustrated and described herein for purposes of description of the preferred embodiment, it will be appreciated by those of ordinary skill in the art that a wide variety of alternate and/or equivalent implementations may be substituted for the specific embodiments shown and described without departing from the scope of the present invention. This application is intended to cover any adaptations or variations of the preferred embodiments discussed herein. Therefore, it is manifestly intended that this invention be limited only by the claims and the equivalents thereof.