Patent Abstract:
A light emitting module is disclosed. The light emitting module includes a lead frame body, lead frame, a heat spreader, an intermediate heat sink, and at least one light emitting element (LED). The lead frame body defines a cavity which accurately registers the heat spreader and includes optical or reflective walls surrounding the light emitting elements soldered on metallized traces of the heat spreader. The lead frame body encases and supports portions of the lead frame. The lead frame extends from outside the body into the cavity to accurately align with solder pads of the heat spreader. All the pre-aligned mechanical, thermal and electrical contacts are then soldered by solder reflow process under tight environmental control to prevent damage to the light emitting element. A robust, healthy 3-dimensional optical-electro-mechanical assembly having a very low thermal resistance in a thermal path from its light emitting element to its intermediate heatsink is created.

Full Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This patent application claims the benefit of priority under 35 USC sections 119 and 120 of U.S. Provisional Patent Application No. 61/302,474 filed Feb. 8, 2010, the entire disclosure of which is incorporated herein by reference. This patent application claims the benefit of priority under 35 USC sections 119 and 120 of U.S. Provisional Patent Application No. 61/364,567 filed Jul. 15, 2010, the entire disclosure of which is incorporated herein by reference. The applicant claims benefit to Feb. 8, 2010 as the earliest priority date. 
    
    
     BACKGROUND 
     The present invention relates to light emitting devices. More particularly, the present invention relates to light emitting device modules and lighting devices. 
     Light emitting diodes (LEDs) are typically made using semiconducting material doped with impurities to create a P-N junction. When electrical potential (voltage) is applied to the P-N junction current flows through the junction. Charge-carriers (electrons and holes) flow in the junction. When an electron meets a hole, it falls into a lower energy level, and releases energy in the form of light (photon, radiant energy) and heat (phonon, thermal energy). 
     In most applications, light is the desired form of energy from an LED and heat is not desired. This is because heat can and often causes permanently damages to the LED, degrades LED performance by causing decreased light output, and leads to a premature device failure. 
     However, in the current state of art, generation of undesired heat cannot be avoided. A typical high power LED chip of 1 mm 2  in area and 0.10 mm in thickness has a P-N junction active layer of only 0.003 mm thick. Yet, it can convert 1 to 2 watts of electrical energy into both radiant and thermal energy. More than 50% of electrical energy is actually converted into thermal energy which can heat up the whole LED within fraction of a second. Typically, such LED operates at a junction temperature of 120 degrees Celsius. That is, these LEDs operate at a temperature greater than the temperature of boiling water (water boils at 100° C.). Above 120 degrees C., the LED&#39;s forward voltage will increase, thus resulting in higher power consumption. Also, its luminous output will drop correspondingly and its reliability and life expectancy will also be adversely affected. 
     The problem of heat is even more apparent for high power LEDs. There is an increasing demand for increasingly brighter LEDs. To make brighter LEDs, the most obvious solution is to increase the electrical power applied to the LEDs. This however leads to LEDs operating at even greater temperatures. As the operating temperature increases, the efficiency of the LEDs decreases, resulting in light output that is less than expected or desired. That is, for example only, doubling the electrical power of the LED does not result in the generation of twice the amount of light. Rather, the light output is much less than the expected twice the luminosity. 
     The problem of heat is compounded by the way in which the LEDs are packaged within light emitting devices such as light bulbs. Light emitting devices of current art (using LEDs as the core of the device) often entrap heat within the device itself. This decreases the expected life of the LED and of the device itself. For example, many LEDs in the marketplace are sold as having expected operating life of 50,000 hours (at which time the LED output declines to seventy percent of its original output). However, light emitting devices (having such LEDs as the light emitting element of the device) typically specifies only 35,000 hours of expected operating life). 
     Accordingly, there remains a need for an improved LED module that eliminates or alleviates these problems associated with heat. 
     SUMMARY 
     The need is met by the present invention. In a first embodiment of the present invention, a light emitting module is disclosed. The light emitting module includes a lead frame body, lead frame, a heat spreader, and at least one light emitting element placed on the heat spreader. The lead frame body defines a cavity. A first portion of the lead frame is encased within the lead frame body wherein the lead frame body provides structural support and separation of leads of the lead frame. The heat spreader is positioned at least partially within the cavity of the lead frame body. The heat spreader is connected to the lead frame. At least one light emitting element is placed on the heat spreader such that heat generated by the light emitting element is drawn away from the light emitting element by the heat spreader. 
     In various embodiments, the light emitting module may include any one or more the following characteristics in any combination: The lead frame body defines a reflective surface surrounding the cavity. The lead frame includes at least two electrical conductors. The lead frame is electrically connected to the light emitting elements on the heat spreader. A snap in body engaging second portion of the lead frame. The lead frame body includes a first major surface, the first major surface defining a first plane, and wherein the lead frame is bent relative to the first plane. 
     The heat spreader includes a ceramic substrate and a metal trace layer fabricated on the substrate. The substrate has a first major surface and a second major surface opposite the first major surface. The metal trace is adaptable for attaching light emitting element as well as for attaching the lead frame. 
     In an alternative embodiment of the heat spreader, the heat spreader includes a metallic substrate, a first dielectric layer above the metallic substrate, a second dielectric layer below the metallic substrate, a metal trace layer fabricated on the first dielectric layer, a metal layer fabricated below the second dielectric layer, and metal trace adaptable for attaching light emitting element as well as attaching the lead frame. 
     The light emitting element may include light emitting junction diode encased within resin. Alternatively, the light emitting element may include light emitting diode chip. 
     In a second embodiment of the present invention, a light emitting module is disclosed. The module includes lead frame, lead frame body, and a heat spreading light emitting component. The lead frame includes electrical conductors. The lead frame body encases first portion of the lead frame providing mechanical support to the lead frame. The lead frame body defines a cavity. The heat spreading light emitting component includes a thermally conductive substrate having a first major surface, and electrical traces on the first major surface of the substrate. The light emitting element mounted on the substrate is electrically connected to its metallized electrical traces. The lead frame is electrically connected to the metallized electrical traces of the first major surface of the heat spreader. 
     In a third embodiment of the present invention, a heat spreader apparatus is disclosed. The heat spreader includes a metallic substrate, a first dielectric layer above the metallic substrate, a second dielectric layer below the metallic substrate, a metal trace layer fabricated on the first dielectric layer, a metal layer fabricated below the second dielectric layer. The metal trace is adaptable for attaching light emitting element and adaptable for attaching the lead frame. The metallic substrate may include Aluminum. The first dielectric layer may include Aluminum oxide. The second dielectric layer may include Aluminum oxide. 
     In a third embodiment of the present invention, a light emitting subassembly is disclosed. The subassembly includes an intermediate heat sink and at least one light emitting module mounted on the intermediate heat sink. The light emitting module includes a lead frame body defining a cavity, lead frame wherein first portions of the lead frame are encased within the lead frame body, a heat spreader positioned at least partially within the cavity of the lead frame body, the heat spreader connected to the lead frame, and at least one light emitting element placed on the heat spreader. The heat spreader is mechanically and thermally connected to the intermediate heat sink by a robust solder joint covering its entire bottom surface area. 
     In the subassembly, intermediate heat sink defines slots for engagement with the light emitting module. The intermediate heat sink includes a reflective top surface. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a top perspective view of a light emitting module in accordance of one embodiment of the present invention. 
         FIG. 2  illustrates a bottom perspective view of the light emitting module of FIG.  1 . 
         FIG. 3  illustrates a top view of the light emitting module of  FIGS. 1 and 2 . 
         FIG. 4  illustrates a first side view of the light emitting module of  FIGS. 1 through 3 . 
         FIG. 5  illustrates a second side view of the light emitting module of  FIGS. 1 through 3 . 
         FIG. 6  illustrates a bottom view of the light emitting module of  FIGS. 1 and 2 . 
         FIG. 7  illustrates a cut away side view of the light emitting module of  FIGS. 1 through 3  cut along line A-A of  FIG. 3 . 
         FIG. 8  illustrates a cut away side view of the light emitting module of  FIGS. 1 through 3  cut along line B-B of  FIG. 3 . 
         FIG. 9  is another illustration of the top view of the light emitting module of  FIGS. 1 and 2  with portions of the light emitting module highlighted. 
         FIG. 10  is another illustration of the bottom view of the light emitting module of  FIGS. 1 and 2  with portions of the light emitting module highlighted. 
         FIG. 11  illustrates a top perspective view of a light emitting module in accordance of another embodiment of the present invention. 
         FIG. 12  illustrates a partially exploded top perspective view of the light emitting module of  FIG. 11 . 
         FIG. 13  illustrates a partially exploded bottom perspective view of the light emitting module of  FIG. 11 . 
         FIG. 14  illustrates an exploded side view of a first alternative embodiment of a portion of the light emitting module. 
         FIG. 15  illustrates an exploded side view of a second alternative embodiment of a portion of the light emitting module. 
         FIG. 16  illustrates a top perspective view of a subassembly in accordance with another embodiment of the present invention. 
         FIG. 17  illustrates a bottom perspective view of the subassembly of  FIG. 16 . 
         FIG. 18  illustrates a top view of the subassembly of  FIGS. 16 and 17 . 
         FIG. 19  illustrates a bottom view of the subassembly of  FIGS. 16 and 17 . 
         FIG. 20  illustrates a cut away side view of the subassembly of  FIG. 18  cut along line C-C. 
         FIG. 21  illustrates a cut away side view of the subassembly of  FIG. 18  cut along line D-D. 
         FIG. 22  illustrates a top perspective view of a subassembly in accordance with yet another embodiment of the present invention. 
         FIG. 23  illustrates a top perspective view of a subassembly in accordance with yet another embodiment of the present invention. 
         FIG. 24  illustrates a top perspective view of a subassembly in accordance with yet another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention will now be described with reference to the Figures which illustrate various aspects, embodiments, or implementations of the present invention. In the Figures, some sizes of structures, portions, or elements may be exaggerated relative to sizes of other structures, portions, or elements for illustrative purposes and, thus, are provided to aid in the illustration and the disclosure of the present invention. 
     This patent application claims the benefit of priority of and incorporates by reference the entirety of U.S. Provisional Patent Application No. 61/302,474 filed Feb. 8, 2010 and U.S. Provisional Patent Application No. 61/364,567 filed Jul. 7, 2010. Each of these incorporated provisional applications includes drawings and specifications including figure designations, reference numbers, and descriptions corresponding to the figure designations and to the reference numbers. To avoid confusion and to discuss the inventions with even more clarity, the figure designations and reference numbers used in the incorporated documents are not used in this document. Rather, in this document, new figure designations, reference numbers, and descriptions corresponding to the figure designations are used. 
       FIG. 1  illustrates a top perspective view of a light emitting module  1000  in accordance of one embodiment of the present invention.  FIG. 2  illustrates a bottom perspective view of the light emitting module  1000  of  FIG. 1 .  FIG. 3  illustrates a top view of the light emitting module  1000  of  FIGS. 1 and 2 .  FIG. 4  illustrates a first side view of the light emitting module  1000  of  FIGS. 1 through 3 .  FIG. 5  illustrates a second side view of the light emitting module  1000  of  FIGS. 1 through 3 .  FIG. 6  illustrates a bottom view of the light emitting module  1000  of  FIGS. 1 and 2 .  FIG. 7  illustrates a cut away side view of the light emitting module  1000  of  FIGS. 1 through 3  cut along line A-A of  FIG. 3 .  FIG. 8  illustrates a cut away side view of the light emitting module  1000  of  FIGS. 1 through 3  cut along line B-B of  FIG. 3 .  FIG. 9  is another illustration of the top view of the light emitting module  1000  of  FIGS. 1 and 2  with portions of the light emitting module  1000  highlighted.  FIG. 10  is another illustration of the bottom view of the light emitting module  1000  of  FIGS. 1 and 2  with portions of the light emitting module  1000  highlighted. 
       FIG. 11  illustrates a top perspective view of a light emitting module  1100  in accordance of another embodiment of the present invention. The light emitting module  1100  has the same components and elements as the light emitting module  1000  of  FIGS. 1 through 10  with portions in a different configuration.  FIG. 12  illustrates a partially exploded top perspective view of the light emitting module  1100  of  FIG. 11 .  FIG. 13  illustrates an exploded bottom prospective view of a first alternative embodiment of a portion of the light emitting module  1100  of  FIG. 12 .  FIG. 14  illustrates an exploded side view of a first alternative embodiment of a portion of the light emitting module  1100  of  FIG. 12 .  FIG. 15  illustrates an exploded side view of a second alternative embodiment of a portion of the light emitting module  1100  of  FIG. 12 . 
     That is,  FIGS. 1 through 10  illustrate different views of the light emitting module  1000  of the present invention.  FIGS. 11 and 12  illustrate the light emitting module  1000  in a different configuration and referred to as light emitting module  1100 . To avoid duplicity and confusion, and to increase clarity, in the Figures, not every referenced portion is annotated in every Figure. 
     Referring to  FIGS. 1 through 13 , in one embodiment of the present invention, the light emitting module  1000  includes a lead frame body  1010 , lead frame  1020 , at least one heat spreader  1050 , and at least one light emitting element  1080  placed on the heat spreader  1050 . 
     Lead Frame Body 
     The lead frame body  1010  is typically molded plastic but can be any other material. The lead frame body  1010  defines a cavity  1012  within which the heat spreader  1050  is accurately positioned. The body cavity  1012  is most clearly illustrated in  FIGS. 12 and 13 . In the illustrated embodiment, the heat spreader  1050  is mostly or entirely within the body cavity  1012  (best illustrated in  FIGS. 12 and 13 ); however, in other embodiments, the heat spreader  1050  may be only partially concealed inside the body cavity  1012 . The lead frame body  1010  can be made from thermoplastic or thermoset plastics which can withstand high temperatures over 200 C for a short period of time. In any event, the body cavity  1012  is large enough to expose the light emitting element  1080  while providing mechanical and structural support to the lead frame  1020 . 
     The lead frame body  1010  defines reflector surface  1014  surrounding the body cavity  1012 . In the illustrated embodiment, the body cavity  1012  has a substantially rectangular shape. Accordingly, the lead frame body  1010  defines four reflector surfaces  1014 . However, that the number of rectangular surfaces may vary depends on the shape of the body cavity  1012 . The reflector surface  1014  surrounds the body cavity  1012  wherein the light emitting elements  1080  are placed. Consequently, the reflector surface  1014  reflects and redirects light (directed to it from the light emitting elements  1080 ) toward a desired direction. The light directed to the reflector surface  1014  are at a very low angle (illustrated as angle  1015  in  FIG. 8 ) and is lost in the prior art devices which are typically MCPCB (metal-core printed circuit board) or PCB (printed circuit board) having non-reflective flat surfaces. Consequently, the luminous efficiency of the module is higher than that of the prior art. 
     In the illustrated embodiment, the reflectivity of the reflector surface  1014  is greater than 85 percent. To realize the reflective surface  1014 , the lead frame body  1010  may include high temperature thermoplastics or thermoset plastics that are loaded with reflective materials such as, for example only, Titanium Dioxide (TiO2), Barium Sulfate (BaSO4), and others. In one embodiment, the material used for the lead frame body  1010  is a Polyphthalamide (also known as PPA, High Performance Polyamide) with trade name as Amodel which has a reflectivity of 90 percent with a low percentage of scattering. 
     Lead Frame 
     The lead frame  1020  may, but is not required to, include multiple leads, portions, or both as illustrated. In the illustrated embodiment, the lead frame  1020  is used to conduct electrical power and is a stamped metal such as, for example only, copper or other metal alloy. The stamped metal can be, for example, sheet metal. 
     In the illustrated embodiment, the lead frame  1020  includes four leads extending from outside the lead frame body  1010 , through the substance of the lead frame body  1010 , and into the body cavity  1012 . In the body cavity  1012 , the lead frame  1020  makes contact with the heat spreader  1050 . Consequently, in the illustrated embodiment, the lead frame body  1010  encases the portion of the lead frame  1020  that lies within the lead frame body  1010  as the lead frame  1020  extends from beyond the lead frame body  1010  into the body cavity  1012 . This portion is referred to as the first portion. In  FIGS. 9 and 10 , the lead frame  1020  is highlighted using cross hatches for even more clear illustration of the lead frame  1020  in relation to the lead frame body  1010 . Such encasing configuration is often referred to as over molding. 
     For ease of discussion, various portions of the lead frame  1020  may be referenced using an alphabetical letter following the lead frame reference number  1020 . For example, the portion of the lead frame  1020  extending into the body cavity  1012  is referred to as the inner end  1020 A of the lead frame  1020 . In generally, reference number  1020  indicates the lead frame  1020  as a whole or in general. 
     The inner end  1020 A of the lead frame  1020  is engaged to metal traces  1052  of the heat spreader  1050 . In the illustrated embodiment, the inner end  1020 A of the lead frame  1020  is soldered on to the metal traces  1052  of the heat spreader  1050 . The soldering method can be any suitable method, for example, solder reflow process in which a small dot of solder paste is heated to its melting temperature; thus, the inner end  1020 A and the traces  1052  are bonded by a robust solder joint. 
     Here, the lead frame body  1010  acts as an alignment fixture between all the lead frame  1020  and corresponding metal circuit traces  1052 , soldering of all of the light emitting elements  1080  to the heat spreader  1050  can be done simultaneously. This simplifies the process time and reduces the exposure of LEDs to heat more than once. Furthermore, the lead frame body  1010  provides for electrical isolation and alignment between multiple leads of the lead frame  1020 . 
     Outer ends  1020 B of the lead frame are adapted to be connected to an external electrical power supply. The lead frame  1020  can be bent or formed into various shape to suit the mounting requirements. Similarly, other portions  1020 C may extend out of the body for other purposes such as, for example only, mounting or engaging with additional components not illustrated herein. 
     One embodiment of the reconfigured light emitting module  1000  of  FIGS. 1 and 2  are illustrated in  FIGS. 11 through 13  as the light emitting module  1100 . The light emitting module  1100  has the same elements or components as the light emitting module  1000  of  FIGS. 1 and 2 ; however, its lead frame  2010  is bent 90 degrees (orthogonal) to facilitate solder connections with its electrical components located behind the optical front face of the module; and also to provide an easy engagement with thermal or mechanical component, such as, for example only, an intermediate heat sink  1090  illustrated in  FIGS. 16 through 24  and discussed in more detail herein below. The orthogonal bent is 90 degrees relative to a plane defined by the first major surface  1016  defined by the lead frame body  1010 . However, the degree of the bent angle is not limited to 90 degrees in the present invention. 
     This bent configuration allows the light emitting module  1100  to be snapped into another assembly with its snap in body structure shown in the Figures and discussed below. This facilitates its manufacturing process resulting lower manufacturing costs and times. 
     Once assembled with the intermediate heat sink  1090 , the entire assembly, or can be the core component of general lighting applications such as, for example only, and without limitation, light bulbs, lighting luminairs, street lights or parking light modules. 
     Snap in Body 
     A snap in body  1030  can be used to provide additional structural support the lead frame  1020  as well as electrical isolation between the leads of the lead frame  1020 . As illustrated, the snap in body  1030  engages or surrounds a second portion of the lead frame  1020  that is proximal to the outer ends  1020 B of the lead frame  1020 . The snap in body  1030  may include potions such as snap in finger  1030 A to securely engage with other components such as an intermediate heat sink to be discussed below. A stopper  1030 B portion of the snap in body  1030  allows the snap in body  1030  to be secured with a mating component such as an intermediate heat sink illustrated in  FIGS. 16 through 24 . 
     Heat Spreader 
     The heat spreader  1050  is connected to the lead frame  1020  as indicated in Figures, and most clearly in  FIGS. 9 and 10 . The layers associated with the heat spreader  1050  and its connection to the lead frame  1020  is discussed in more detail herein below. 
     At least one light emitting element  1080  is placed on the heat spreader  1050 . In the illustrated embodiment, the light emitting module  1000  includes six (6) light emitting diode packages (LEDs). Each diode package includes at least one light emitting chip encapsulated in an encapsulant, e.g. silicone or epoxy. In alternative embodiments, each light emitting element  1080  may have at least one raw light emitting chip. Each light emitting element  1080  can have a few LED chips of any color or a mixture of different color or size. Moreover, the different colors and sizes of light emitting element  1080  that can be placed on the heat spreader  1050  is only limited by its physical and electrical limitations, and, depending on applications, can be very large. 
     If light emitting chips are used as the light emitting elements  1080 , then die attach of chips is fabricated on the heat spreader  1050  followed by wire bonding and finally by an encapsulation process. In this configuration, the heat spreader  1050  also serves as the substrate for multiple light emitting chips. Also, the encapsulation process can be simple due to its large optical lens that can be placed over the entire body cavity  1012  and then filled with silicone gel to optically couple it to all the light emitting elements under it. The encapsulant can be filled with phosphors to alter the wavelengths of the LED chips mounted on the heat spreader. Or, the encapsulant can be loaded with some fine particles of reflective materials such as, for example only, Titanium Dioxide (TiO2), Barium Sulfate (BaSO4), and others. 
     The heat spreader  1050  can be made of any thermally conductive material, for example, ceramics or Aluminum coated with dielectric. Other examples of suitable materials for the heat spreader  1050  include, without limitation, ceramics such as Alumina, Aluminum Nitride, or Anodized Aluminum. 
     Dimensions of the heat spreader  1050  can vary greatly. For example, the heat spreader  1050  may have thickness ranging from sub-millimeters (mm) to many centimeters (cm). In the illustrated embodiment, the heat spreader  1050  thickness ranges from below one (1) mm to a few mm depending on size and requirements. 
       FIG. 14  illustrates an exploded side view of a first alternative embodiment of the heat spreader  1050  and is referred to herein as the heat spreader  1050 A. Referring to  FIGS. 1 to 14  but mostly  FIG. 14 , the heat spreader  1050 A includes a substrate  1054 A made with ceramics. The substrate  1054 A has a first major surface  1056  and a second major surface  1058  opposite the first major surface  1056 . The metal trace layer  1052  is fabricated on the first major surface  1056 . The metal trace  1052  is adaptable for attaching light emitting elements  1080 . 
     Additionally, the metal trace  1052  is adaptable for attaching the inner end  1020 A of the lead frame  1020 . Because the substrate  1054 A is ceramic (thereby electrically insulating), no insulating material is needed to isolate the substrate  1054 A from the traces  1052 . A metal layer  1060  is fabricated on the second major surface  1058 . The metal layer  1060  allows for solder attachment of the heat spreader  1050  to the intermediate heat sink  1090  illustrated in  FIGS. 16 through 24  and discussed in more detail herein below. Then, a solder layer  1062  is used to bond the heat spreader  1050  to the intermediate heat sink  1090 . This solder layer  1062  can be, but is not required to be lead free. Lead free solder has typical thermal conductivity of approximately 57 watts per meter degrees Kevin. This is significantly higher than other methods of heat contact. A solder layer  1062  is used to solder the heat spreader  1050 A onto an intermediate heat sink  1090  illustrated in  FIGS. 16 through 24  and discussed in more detail herein below. Soldering the heat spreader  1050 A creates a much better thermal contact (between the heat spreader  1050 A and the intermediate heat sink  1090 ) compared to the currently used technique of screw attachment. 
       FIG. 15  illustrates an exploded side view of a second alternative embodiment of heat spreader  1050  and is referred to herein as the heat spreader  1050 B. Referring to  FIGS. 1 to 15  but mostly  FIG. 15 , the heat spreader  1050 B includes a substrate  1054 B made with Aluminum. Dielectric layers  1064  and  1066  include insulation materials such as, for example, Aluminum oxide. The insulation layers can be fabricated using anodizing process. This prevents the traces  1052  from shorting out. Again, the substrate  1054 B and with its dielectric layers  1064  and  1066  has a first major surface  1056  and a second major surface  1058  opposite the first major surface  1056 . The metal trace layer  1052  is fabricated on the first major surface  1056 &#39;s dielectric layer  1064  using a combination of a thin-film and plating processes. The metal trace  1052  may consist of Titanium, Nickel, Copper, Nickel, and Gold for example only and is adaptable for soldering to the light emitting elements  1080 . Additionally, the metal trace  1052  is adaptable for soldering to the inner end  1020 A of the lead frame  1020 . 
     There is no bonding adhesive needed on an anodized Aluminum for bonding the traces  1052  to the dielectric layer  1064 . In the illustrated embodiment, the thickness of Anodized layer is in the region of 33-55 microns approximately. As the Aluminum oxide layers  1064  and  1066  have a high thermal conductivity of about 18 Watt per Meter-degree Kelvin, the thermal conductivity of the Anodized Aluminum is much higher compared to the thermal conductivity of MCPCB (metal-core printed circuit boards) often used in the prior art lighting modules. The existing designs using MCPCB typically has lower thermal conductivity of less than 2 Watt per Meter-degree Kelvin. Accordingly, the present invention provides for higher thermal conductivity to remove heat away from the light emitting elements  1080  compared to that of the existing art. 
     An anodized aluminum heat spreader  1050 B uses its aluminum oxide layer  1064  and  1066  as natural dialectical layers. In contrast, MCPCB of the prior art uses organic dielectric layers as a dielectric. 
     In the illustrated embodiment, the anodized Aluminum oxide dielectric layers  1064  and  1066  are approximately 33 microns to 55 microns thick and their thermal conductivity is approximately 18 Watt per Meter-degree Kelvin. In contrast, the organic dielectric layers of MCPCB as typically 75 microns to 125 microns thick and their thermal conductivity is in the range of approximately 2 Watt per Meter-degree Kelvin. Hence, anodized Aluminum heat spreader  1050  of the present invention has a much superior thermal conducting performance. 
     A metal layer  1060  is fabricated on the second major surface  1058 &#39;s dielectric layer  1066 . Again, the metal layer  1060  allows for solder attachment of the heat spreader  1050  to the intermediate heat sink  1090 . A solder layer  1062  is used to solder the heat spreader  1050 B onto an intermediate heat sink  1090  illustrated in  FIGS. 16 through 24  and discussed in more detail herein below. Soldering the heat spreader  1050  creates a much better thermal contact (between the heat spreader  1050  and the intermediate heat sink  1090 ) compared to the currently used technique of screw attachment with less contact surface area and with a high interface resistance. 
     In one example embodiment, the heat spreader  1050  is made of Aluminum with a top surface area of 174 mm 2  and a thickness of 0.63 mm. With six light emitting elements  1080  soldered on the metal traces  1052 , each requiring about 1 mm 2  area, the surface area ratio of the heat spreader  1050  to that of the light emitting elements  1080  is 174 to 6, or approximately 29 to 1. As such, its thermal spreading resistance is almost zero. 
     The heat spreader  1020  and the light emitting elements  1080 , combined, are referred to herein as the heat spreading lighting component. 
     Intermediate Heat Sink 
       FIG. 16  illustrates a top perspective view of a light emitting subassembly  1200  in accordance with another embodiment of the present invention.  FIG. 17  illustrates a bottom perspective view of the light emitting subassembly  1200  of  FIG. 16 .  FIG. 18  illustrates a top view of the light emitting subassembly  1200  of  FIGS. 16 and 17 .  FIG. 19  illustrates a top view of the light emitting subassembly  1200  of  FIGS. 16 and 17 .  FIG. 20  illustrates a cut away side view of the light emitting subassembly  1200  of  FIG. 18  cut along line C-C.  FIG. 21  illustrates a cut away side view of the light emitting subassembly  1200  of  FIG. 18  cut along line D-D. 
     Referring to  FIGS. 16 through 21 , the subassembly  1200  includes an intermediate heat sink  1090  and at least one light emitting module  1100  mounted on the intermediate heat sink  1090 . The light emitting module  1100  is the same light emitting module of  FIGS. 11 through 13  and discussed herein above in more detail. 
     The intermediate heat sink  1090  is soldered (structurally and thermally connected) to the heat spreader  1050 . The heat spreader  1050 , in turn, is soldered (structurally and thermally connected) to the light emitting elements  1080 . This is most clearly illustrated in  FIGS. 20 and 21 . Accordingly, heat generated by the light emitting elements  1080  is drawn away from the light emitting elements  1080  by the heat spreader  1050 . The heat is then drawn away from the heat spreader  1050  by the intermediate heat sink  1090 . 
     The intermediate heat sink  1090  may have any shape and size depending on the final product design requirements. In the illustrated embodiment, the intermediate heat sink  1090  is made of metal such as, for example only, copper alloy or aluminum alloy, and can be plated with nickel. Such plating allows for easier soldering of the heat spreader  1050  to the intermediate heat sink  1090 . The intermediate heat sink  1090  defines slots  1094  to allow portions of the light emitting module  1100  to pass through the slots and thereby engage the intermediate heat sink  1090 . Further, the slots  1094  aid in alignment of the intermediate heat sink  1090  to the light emitting module  1100 . Using this alignment technique, the manufacturing process is less labor intensive compared to the manufacturing process of the existing products. This results in higher yield and lower cost of assembly. 
     The intermediate heat sink  1090  is covered by an optical reflective element or itself coated with reflective materials on the top side  1092  to form a reflective bowl to reflect and recycle light thereby minimizing loss of light. The reflective material or component may have a mirror finished Aluminum or a silver coating having thickness of a few Angstroms. 
     In the illustrated embodiment, the heat generated by the light emitting elements  1080  is drawn away from the light emitting elements  1080  by the heat spreader  1050  that spreads the heat into its own body which has a much greater thermal mass than the light emitting elements  1080 . Further down along the thermal path, the heat is conducted to the intermediate heat sink  1090  which dimensions and surface areas are many times that of the heat spreader  1050 . Consequently, the heat generated by the light emitting elements  1080  is effectively removed from the light emitting elements  1080  thereby reducing adverse effects of heat on the light emitting elements  1080  such as reduction of luminous output, damage to the LED chips, and ultimately shortened service life. 
       FIG. 22  illustrates a top perspective view of a light emitting subassembly  1300  in accordance with another embodiment of the present invention. Referring to  FIG. 22 , the subassembly  1300  includes an intermediate heat sink  1310  and at least one light emitting module  1100  mounted on the intermediate heat sink  1310 . The light emitting module  1100  is the same light emitting module of  FIGS. 11 through 13  and discussed herein above in more detail. 
     The intermediate heat sink  1310  is substantially flat in the illustrated embodiment as opposed to a bowl shaped intermediate heat sink  1090  (of  FIGS. 16 through 21 ). Further, the intermediate heat sink  1310  generally has a flat cylindrical shape. However, the intermediate heat sink  1310  is similar to the intermediate heat sink  1090  (of  FIGS. 16 through 21 ) in composition and function. For example, the intermediate heat sink  1310  is made of thermally conductive material such as metal alloy. Further, the intermediate heat sink  1310  has a top surface  1312  that is coated with reflective material. Also, the intermediate heat sink  1310  defines slots  1314  used to aid in the engagement of and alignment with the intermediate heat sink  1310  with the one light emitting module  1100 . 
       FIG. 23  illustrates a top perspective view of a light emitting subassembly  1400  in accordance with yet another embodiment of the present invention. Referring to  FIG. 23 , the subassembly  1400  includes an intermediate heat sink  1410  and at least one light emitting module  1100  mounted on the intermediate heat sink  1410 . The light emitting module  1100  is the same light emitting module of  FIGS. 11 through 13  and discussed herein above in more detail. 
     The intermediate heat sink  1410  is substantially flat in the illustrated embodiment as opposed to a bowl shaped intermediate heat sink  1090  (of  FIGS. 16 through 21 ). Further, the intermediate heat sink  1410  generally has a rectangular prism shape. However, the intermediate heat sink  1410  is similar to the intermediate heat sink  1090  (of  FIGS. 16 through 21 ) in composition and function. For example, the intermediate heat sink  1410  is made of thermally conductive material such as metal alloy. Further, the intermediate heat sink  1410  has a top surface  1412  that is covered with an optical reflective element or itself coated with reflective material. Also, the intermediate heat sink  1410  defines slots  1414  used to aid in the engagement of and alignment with the intermediate heat sink  1410  with the one light emitting module  1100 . 
       FIG. 24  illustrates a top perspective view of a light emitting subassembly  1500  in accordance with yet another embodiment of the present invention. Referring to  FIG. 24 , the subassembly  1500  includes an intermediate heat sink  1510  and at least one light emitting module  1100  mounted on the intermediate heat sink  1510 . In fact, in the illustrated embodiment, the light emitting subassembly  1500  includes two light emitting modules  1100 . The light emitting module  1500  is the same light emitting module of  FIGS. 11 through 13  and discussed herein above in more detail. 
     Again, the intermediate heat sink  1510  is substantially flat in the illustrated embodiment as opposed to a bowl shaped intermediate heat sink  1090  (of  FIGS. 16 through 21 ). Further, the intermediate heat sink  1510  generally has a rectangular prism shape. However, the intermediate heat sink  1510  is similar to the intermediate heat sink  1090  (of  FIGS. 16 through 21 ) in composition and function. For example, the intermediate heat sink  1510  is made of thermally conductive material such as metal alloy. Further, the intermediate heat sink  1510  has a top surface  1512  that is covered with an optical reflective element or itself coated with reflective material. Also, the intermediate heat sink  1510  defines slots  1514  used to aid in the engagement of and alignment with the intermediate heat sink  1510  with the one light emitting module  1100 . 
     The intermediate heat sink  1090 ,  1310 ,  1410 ,  1510  transfers heat from the heat spreader  1050  to an ultimate heat sink. The ultimate heat sink, in many applications, is the body of the lighting device such as the light bulb that includes light emitting subassembly  1200 ,  1300 ,  1400 , and  1500 . At the body of the lighting device, the heat is dissipated, often by convention to the surrounding air, or even to other heat dissipating mechanisms such as an external heat sink. 
     Thermal Path 
     Referring to  FIGS. 1 through 24 , and more specifically to  FIGS. 16 through 24 , as illustrated, the thermal path of heat generated by the light emitting elements  1080  is drawn away from the light emitting elements  1080  by the heat spreader  1050  that spreads the heat into its own body which has a much greater thermal mass than the light emitting elements  1080 . At the same time, the heat is then conducted to the intermediate heat sink  1090  which has even greater dimensions than the dimensions of the heat spreader  1020  as well as much greater surface area. Consequently, the heat generated by the light emitting elements  1080  is effectively removed from the light emitting elements  1080  thereby reducing adverse effects of heat on the light emitting elements  1080  such as reduction of luminous output, damage to the light emitting elements  1080 , and ultimately shortened service life. 
     For subassemblies  1200 ,  1300 ,  1400 ,  1500  where its included heat spreader  1050 A has the configuration illustrated in  FIG. 14 , the thermal path from the light emitting elements  1080  to the intermediate heat sink  1090 ,  1310 ,  1410 ,  1510  is as follows: the heat flux flows from light emitting element  1080  in the following sequence to the solder, the metal traces  1052 , the ceramic substrate  1054 A, the metal layer  1060 , the solder  1062 , and finally to the intermediate heat sink  1090 ,  1310 ,  1410 ,  1510 . 
     For subassemblies  1200 ,  1300 ,  1400 ,  1500  where its included heat spreader  1050 B has the configuration illustrated in  FIG. 15 , the thermal path from the light emitting elements  1080  to the intermediate heat sink  1090 ,  1310 ,  1410 ,  1510  is as follows: the light emitting element  1080  to solder to metal traces  1052  to dielectric layer  1064  to substrate  1054 B to dielectric layer  1066  to metal layer  1060  to solder  1062  to the intermediate heat sink  1090 ,  1310 ,  1410 ,  1510 . 
     For example, in experiments and test, it has been demonstrated that an Alumina heat spreader  1050  having a top surface area of approximately 150 square mm and a thickness of 0.63 mm, can effectively provide negligible spreading thermal resistance for a six light emitting elements, each element including 1 to 2 watt LED packages. Only where LED chips are clustered very close together, a better thermal conductive ceramics such as AlN or anodized aluminum is used. 
     Assembly, Construction, and Additional Advantages 
     Referring to  FIGS. 1 through 24 , and more specifically to  FIGS. 14 ,  15 ,  20 , and  21 , it has already been discussed that the light emitting elements  1080  are soldered onto the metal traces  1052  of the light emitting modules  1000  and  1100  and that the heat spreader  1050  is soldered onto the intermediate heat sinks  1090 ,  1310 ,  1410 , and  1510 . 
     In the present invention, the illustrated designs allow for use of solder reflow technique to solder all the light emitting elements  1080  to the metal traces  1052  and all the lead frame  1020  and heatsink spreader  1050  to the intermediate heatsink  1090 ,  1310 ,  1410  or  1510  all at the same time. That is, only one or at most two soldering cycles are required to solder all the light emitting elements  1080  to form a thermally efficient subassembly. This is a significant advantage over the existing art where hot-bar soldering technique are necessary to solder loose wires from power supply to a MCPCB (metal core printed circuit board) where light emitting diode packages are soldered first. Further, in the present invention, during a single or two solder reflow cycles, the light emitting elements  1080  are exposed only to its allowable peak temperature and time duration, hence protected from overheating and over exposure. These factors reduce the risk of damaging light emitting elements  1080  during the manufacturing process. 
     Also, in manufacturing, the first solder reflow process can be carried out to solder all light emitting elements  1080  to the heat spreader  1050 , then the second solder reflow process is to solder the heat spreader  1050  to lead frame  1020  and the intermediate heat sink all at once. The same solder alloy can be used for both reflow processes because the solder from the first solder reflow has absorbed other metals as impurities and will not melt during the second solder reflow. Hence, the light emitting elements  1080  will not be unsoldered during the second reflow by the same eutectic soldering temperature again. 
     The present invention has a number of potential applications including lighting products such as light bulbs of any wattage and of various luminous performance and physical size and connection. Such device can be built more cheaply than the existing technology having the same luminous performance. Its 3-dimensional modular design can serve as a light engine for any conceivable lighting product such as street light, stadium light, industrial light, security light or any illumination product. 
     CONCLUSION 
     From the foregoing, it will be appreciated that the present invention is novel and offers advantages over the existing art. Although a specific embodiment of the present invention is described and illustrated above, the present invention is not to be limited to the specific forms or arrangements of parts so described and illustrated. For example, differing configurations, sizes, or materials may be used to practice the present invention.

Technology Classification (CPC): 5