WO2015059499A2 - Led package and led module - Google Patents

Led package and led module Download PDF

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Publication number
WO2015059499A2
WO2015059499A2 PCT/GB2014/053187 GB2014053187W WO2015059499A2 WO 2015059499 A2 WO2015059499 A2 WO 2015059499A2 GB 2014053187 W GB2014053187 W GB 2014053187W WO 2015059499 A2 WO2015059499 A2 WO 2015059499A2
Authority
WO
WIPO (PCT)
Prior art keywords
led
circuit board
conductive substrate
led die
electrical
Prior art date
Application number
PCT/GB2014/053187
Other languages
French (fr)
Other versions
WO2015059499A3 (en
Inventor
James Reeves
Andrew Young
Original Assignee
Litecool Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Litecool Limited filed Critical Litecool Limited
Publication of WO2015059499A2 publication Critical patent/WO2015059499A2/en
Publication of WO2015059499A3 publication Critical patent/WO2015059499A3/en

Links

Classifications

    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K1/00—Printed circuits
    • H05K1/02—Details
    • H05K1/0201—Thermal arrangements, e.g. for cooling, heating or preventing overheating
    • H05K1/0203—Cooling of mounted components
    • H05K1/021—Components thermally connected to metal substrates or heat-sinks by insert mounting
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/48—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor body packages
    • H01L33/64—Heat extraction or cooling elements
    • H01L33/642—Heat extraction or cooling elements characterized by the shape
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K1/00—Printed circuits
    • H05K1/02—Details
    • H05K1/0201—Thermal arrangements, e.g. for cooling, heating or preventing overheating
    • H05K1/0203—Cooling of mounted components
    • H05K1/0204—Cooling of mounted components using means for thermal conduction connection in the thickness direction of the substrate
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K1/00—Printed circuits
    • H05K1/18—Printed circuits structurally associated with non-printed electric components
    • H05K1/182—Printed circuits structurally associated with non-printed electric components associated with components mounted in the printed circuit board, e.g. insert mounted components [IMC]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L2224/42—Wire connectors; Manufacturing methods related thereto
    • H01L2224/47—Structure, shape, material or disposition of the wire connectors after the connecting process
    • H01L2224/48—Structure, shape, material or disposition of the wire connectors after the connecting process of an individual wire connector
    • H01L2224/4805—Shape
    • H01L2224/4809—Loop shape
    • H01L2224/48091—Arched
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/15—Details of package parts other than the semiconductor or other solid state devices to be connected
    • H01L2924/181—Encapsulation
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/48—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor body packages
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K2201/00—Indexing scheme relating to printed circuits covered by H05K1/00
    • H05K2201/06—Thermal details
    • H05K2201/066—Heatsink mounted on the surface of the PCB
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K2201/00—Indexing scheme relating to printed circuits covered by H05K1/00
    • H05K2201/09—Shape and layout
    • H05K2201/09009—Substrate related
    • H05K2201/09054—Raised area or protrusion of metal substrate
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K2201/00—Indexing scheme relating to printed circuits covered by H05K1/00
    • H05K2201/10—Details of components or other objects attached to or integrated in a printed circuit board
    • H05K2201/10007—Types of components
    • H05K2201/10106—Light emitting diode [LED]
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K2201/00—Indexing scheme relating to printed circuits covered by H05K1/00
    • H05K2201/10—Details of components or other objects attached to or integrated in a printed circuit board
    • H05K2201/10227—Other objects, e.g. metallic pieces
    • H05K2201/10416—Metallic blocks or heatsinks completely inserted in a PCB

Definitions

  • the present invention relates to light emitting diodes and relates particularly but not exclusively to an improved LED package, an LED module comprising the improved LED package, and a method of manufacturing an LED module comprising the improved LED package.
  • a light-emitting diode is a p-n junction semiconductor diode that emits photons when a current is applied.
  • Figure la illustrates an example of a conventional LED die comprising p and n-type semiconductor layers, a substrate and electrical contact points. Before it can be used in a practical application, an LED chip or die must be packaged.
  • Figure lb illustrates an example of an LED package comprising the conventional LED die of Figure la, a packaging substrate/case, primary electrical connectors and commonly a primary optic in the form of a lens.
  • the primary electrical connectors are provided by leads that extend out through the packaging substrate/case from beneath the LED die, where they connect to a pair of electrical contacts provided on the lower surface of the LED die (i.e. the LED die has a lateral/horizontal architecture).
  • the LED die has a vertical architecture such that one of the electrical contacts is provided on the top of the LED die, and a wire bond can be used to connect this electrical contact to one of leads that extend out through the packaging substrate/case
  • One or more LED packages are then connected physically and electrically (i.e. by secondary electrical connectors) to a circuit board in order to form an LED module, such as that illustrated in Figure lc.
  • One or more LED modules can then be assembled into an LED device, referred to as luminaire or lamp.
  • Figure Id illustrates an example of an LED luminaire or lamp comprising an LED module, a heat sink, a reflector, and secondary optics (i.e. a secondary lens).
  • LED packages such as that illustrated in Figure lb, are designed to be mounted onto an upper surface of a circuit board during the manufacture of an LED module.
  • the surface of the LED package on which the LED die is mounted faces away from the circuit board, whilst the reverse surface of the LED package is bonded/connected to the circuit board, as illustrated in Figure lc.
  • the LED package substrate that separates the LED die from the circuit board is therefore either electrically insulating or includes at least an electrically insulating layer so as to ensure that, other than the connections provided by the primary electrical connectors, the electrical contacts of the LED die are isolated from the electrical tracks provided on the surface of the circuit board.
  • Figure 2 illustrates an example of an alternative LED package arrangement that is designed to be mounted onto a lower surface of a circuit board when included in an LED module, such that the (upper) surface of the LED package on which the LED die is mounted is bonded/connected to the circuit board with the LED die aligned with an aperture in the circuit board.
  • Figure 3 therefore illustrates an alternative LED module arrangement comprising the LED package arrangement of Figure 2.
  • the alternative LED package 1 illustrated in Figure 2 comprises an LED die 3 mounted onto a first (upper) surface 2a of a conductive substrate 2, and an electrically insulating substrate layer 4 is attached to a reverse, second (lower) surface 2b of the conductive substrate 2.
  • the primary electrical connectors are provided on the upper surface 2a of the LED package.
  • the LED die 3 has a vertical architecture such that a first electrical connector/contact 5 is connected to the LED die 3 by a wire bond 7, and is separated from the conductive substrate 2 by an electrical insulation layer 8.
  • a second electrical connector/contact 6 is then connected to the LED die 3 via the conductive substrate 2.
  • the LED package 1 may also optionally be provided with an encapsulation layer 9 that covers the LED die 3.
  • This alternative LED package provides for improved heat dissipation efficiency as the conductive substrate 2 can be used as a heat spreader so as to remove heat from the LED die 3 by thermal conduction and to spread the heat from the relatively small area of the LED die.
  • the LED package 1 is designed to be mounted beneath the circuit board when formed into an LED module, as illustrated in Figure 3, the lower surface of the LED package is exposed/uncovered. It is therefore possible to attach a heat-sink to the lower surface of the insulating substrate layer 4 using a thermal interface material, without having the circuit board interposed between them to disrupt the thermal path and limit the thermal dissipation.
  • a LED module comprises a circuit board provided with an aperture that extends through the circuit board, and an LED package comprising one or more LED die mounted to a conductive substrate, the LED package being mounted to the circuit board with the one or more LED die aligned with the aperture.
  • a first electrical connection between each of the one or more LED die and the circuit board is provided by a junction of a surface of the conductive substrate and a first electrical track provided on the circuit board, and a second electrical connection between each of the one or more LED die and the circuit board is provided by an interconnect device connecting the LED die to a second electrical track provided on the circuit board.
  • junction of a surface of the conductive substrate and the first electrical track may be provided by a fusible electrically conductive material that joins the surface of the conductive substrate to the first electrical track.
  • the circuit board may comprise a first surface and a second surface, the first surface being opposed to the second surface, and the aperture may extend through the circuit board in a direction perpendicular to the first and second surfaces.
  • the first electrical track may be provided on either the first surface or second surface of the circuit board, and the second electrical track may be provided on either the first surface or second surface of the circuit board.
  • the LED package may be mounted to the second surface of the circuit board.
  • the conductive substrate may comprise a first surface and a second surface, the first surface being opposed to the second surface, with the one or more LED die mounted to the first surface of the conductive substrate, and the LED package may then be mounted to the second surface of the circuit board with the first surface of the conductive substrate facing towards the second surface of the circuit board.
  • the conductive substrate may comprise a first surface and a second surface, the first surface being opposed to the second surface, the one or more LED die mounted to the first surface of the conductive substrate, and the LED package may be at least partially embedded within the circuit board with the first surface of the conductive substrate facing in the same direction as the first surface of the circuit board. The LED package may then be at least partially embedded within the circuit board such that the conductive substrate is at least partially contained/accommodated within the aperture that extends through the circuit board.
  • the aperture may be provided with a recess providing a ledge within the aperture to which the LED package is joined, such that the LED package is partially contained/accommodated within the aperture that extends through the circuit board.
  • the first electrical track may be provided on the second surface of the circuit board, and the first electrical connection between each of the one or more LED die and the circuit board may then be provided by a junction of a surface the conductive substrate and the first electrical track.
  • the second electrical track may then be provided on either the first surface or the second surface of the circuit board.
  • the first electrical track may be provided on either the first surface or the second surface of the circuit board, and the first electrical connection between each of the one or more LED die and the circuit board may then be provided by a junction of a surface the conductive substrate and the first electrical track.
  • the second electrical track may then be provided on either the first surface or the second surface of the circuit board.
  • Each of the one or more LED die may comprise a first surface and a second surface, the first surface being opposed to the second surface, and the first surface of the LED die may then be mounted to first surface of the conductive substrate.
  • the interconnect device connecting the LED die to the second electrical track may be provided by any of a wire bond formed between the second surface of the LED die and the second electrical track, and an isolated electrical pad provided on the first surface of the conductive substrate and contacting the first surface of the LED die.
  • Each of the one or more LED die may have a vertical structure, and for each of the one or more LED die the interconnect device connecting the LED die to the second electrical track may then be provided by a wire bond formed between the second surface of the LED die and the second electrical track.
  • each of the one or more LED die may have a lateral structure, and for each of the one or more LED die the interconnect device connecting the LED die to the second electrical track may then be provided by an isolated electrical pad provided on the first surface of the conductive substrate that contacts the first surface of the LED die.
  • the LED module may further comprise a lens formed on the first surface of the circuit board over the aperture.
  • a method of manufacturing an LED module comprises joining an LED package comprising one or more LED die mounted to a conductive substrate to a circuit board with the one or more LED die aligned with an aperture that extends through the circuit board, such that a first electrical connection between each of the one or more LED die and the circuit board is formed by a junction of a surface of the conductive substrate and a first electrical track provided on the circuit board, and forming a second electrical connection between each of the one or more LED die and the circuit board by connecting an interconnect device between the LED die and a second electrical track provided on the circuit board.
  • junction of a surface of the conductive substrate and the first electrical track may be formed by joining the surface of the conductive substrate to the first electrical track using a fusible electrically conductive material.
  • the step of connecting an interconnect device between the LED die and a second electrical track provided on the circuit board may comprises any of forming a wire bond between the LED die and the second electrical track, and connecting an isolated electrical pad provided on the first surface of the conductive substrate that is contact with the first surface of the LED die to the second electrical track.
  • the circuit board may comprise a first surface and a second surface, the first surface being opposed to the second surface, such that the aperture extends through the circuit board in a direction perpendicular to the first and second surfaces.
  • the method may further comprise forming the aperture in the circuit board.
  • the method may further comprise forming a lens on the second surface of the circuit board over the aperture.
  • a light emitting diode (LED) package that consists of a conductive substrate that comprises a first surface and a second surface, the first surface being opposed to the second surface, one or more vertical LED die mounted to a first surface of the conductive substrate, wherein each of the one or more vertical LED die comprises a first surface and a second surface, the first surface being opposed to the second surface, and the first surface of the LED die is mounted to the first surface of the conductive substrate, and a dielectric material covering at least the second surface of the conductive substrate.
  • the first surface of the conductive substrate may be provided with one or more raised areas on which the one or more LED die are mounted.
  • the LED package may consist of a plurality vertical LED die that are mounted to the first surface of the conductive substrate.
  • a light emitting diode (LED) package that consists of a conductive substrate that comprises a first surface and a second surface, the first surface being opposed to the second surface, one or more lateral LED die mounted to the first surface of the conductive substrate, wherein each of the one or more lateral LED die (comprises a first electrode and a second electrode, the first electrode being in contact with an isolated electrical pad provided on the first surface of the conductive substrate and the second electrode being in contact with the first surface of the conductive substrate; and a dielectric material covering at least the second surface of the conductive substrate.
  • the first surface of the conductive substrate may be provided with one or more raised areas on which the one or more LED die are mounted.
  • the LED package may consist of a plurality of isolated electrical pads that are provided on the first surface of the conductive and a plurality of lateral LED die mounted to the first surface of the conductive substrate, with the first electrode of each of the plurality of lateral LED die being in contact with one of the plurality of isolated electrical pads.
  • the LED package may consist of a single isolated electrical pads provided on the first surface of the conductive substrate and a plurality of lateral LED die mounted to the first surface of the conductive substrate, with the first electrode of each of the plurality of lateral LED die being in contact with the isolated electrical pad.
  • Figure la illustrates a cross-sectional view of an example of a conventional LED die
  • Figure lb illustrates a cross-sectional view of an example of a conventional LED package comprising the conventional LED die of Figure la;
  • Figures lc illustrates a cross-sectional view of an example of a conventional LED module comprising one or more of the conventional LED packages of Figure lb;
  • Figure Id illustrates a cross-sectional view of an example of a conventional LED device comprising the conventional LED module of Figure lc;
  • Figure 2 illustrates a cross-sectional view of an example of an alternative LED package arrangement
  • Figures 3 illustrates a cross-sectional view of an example of an LED module comprising the alternative LED package of Figure 2;
  • Figure 4 illustrates a cross-sectional view of an example embodiment of a simplified LED package
  • Figure 5 illustrates a cross-sectional view of an example of an LED module comprising the simplified LED package of Figure 4;
  • Figure 6a illustrates a cross-sectional view of another example of an LED module comprising a simplified LED package
  • Figure 6b illustrates a cross-sectional view of an alternative example of an LED module comprising a simplified LED package
  • Figure 7 illustrates a cross-sectional view of an example of an LED module comprising a further example of a simplified LED package
  • Figure 8 illustrates a cross-sectional view of a yet further example embodiment of a simplified LED package
  • Figure 9 illustrates a cross-sectional view of another example embodiment of a simplified LED package
  • Figure 10 illustrates a cross-sectional view of an example of an LED module comprising simplified LED package of Figure 8.
  • Figure 11 illustrates a cross-sectional view of another example of an LED module comprising simplified LED package of Figure 8. It has been recognised by the present inventors that the alternative LED package arrangement described above in relation to Figure 2 can be simplified, thereby reducing the cost and complexity of manufacturing an LED package, and increasing the flexibility and density in the arrangement of multiple LED packages in an LED module. In particular, the present inventors have recognised that, for an LED package that is designed to be mounted to the lower surface of a circuit board, it is straightforward for one or both of the electrical connections between the LED die and the circuit board to be formed when mounting LED package to the circuit board.
  • the present inventors have recognised that it is not necessary to provide the LED package with any more than one distinct/discrete electrical connector/interconnect device (i.e. lead, track and/or wire bond) for each LED die included in the LED package, wherein a distinct electrical connector/interconnect device is a separate physical component of the LED package whose specific purpose is to provide means for forming an electrically conductive connection between the LED die and an external electrical circuit.
  • a distinct electrical connector/interconnect device is a separate physical component of the LED package whose specific purpose is to provide means for forming an electrically conductive connection between the LED die and an external electrical circuit.
  • FIG 4 therefore illustrates an example embodiment of a simplified LED package 10 as described herein.
  • the LED package 10 comprises a conductive substrate 11, an LED die 12 mounted to a first (upper) surface 11a of the conductive substrate, a dielectric material 13 on a reverse, second (lower) surface lib of the conductive substrate, and does not comprise any distinct electrical connectors.
  • the LED package does not include a primary optic.
  • the LED package 10 illustrated in the example of Figure 4 therefore consists entirely of the conductive substrate 11, the LED die 12, and the dielectric material 13.
  • Figure 5 then illustrates an LED module 20 that includes the LED package 10 of Figure 4.
  • the LED module 20 is formed by physically and electrically connecting the LED package 10 to a circuit board 21.
  • the circuit board 21 has a first (upper) surface 21a and a second (lower) surface 21b, and an aperture 22 that extends through the circuit board 21 in a direction perpendicular to the first and second surfaces 21a, 21b.
  • the LED package 10 is located such that first surface 11a of the conductive substrate 11 of the LED package 10 (i.e. on which the LED die 12 is mounted) faces the second surface 21b of the circuit board 21.
  • the LED die 12 mounted on the first surface 11a of the conductive substrate 11 is aligned with the aperture 22 such that light emitted by the LED die 12 will pass through the aperture 22.
  • a first electrical connection between the circuit board 21 and the LED die 12 is formed by the bonding/joining/attaching of a surface of the conductive substrate 11 to a first electrical track 23a provided on the lower surface 21b of the circuit board 21 (e.g. using a fusible conductive material such as solder) that is abutted by/adjoins the surface of the conductive substrate 11, whilst a second electrical connection is provided by forming a distinct electrical connector/interconnect device in the form of a wire bond 24 between the LED die 12 and a second electrical track 23b provided on the upper surface 21a of the circuit board 21.
  • both the conventional LED package illustrated in Figure lb and the alternative LED package illustrated in Figure 2 include distinct electrical connectors/interconnect devices (i.e. leads, tracks and/or wire bonds) that are formed as part of the LED package, and that are subsequently used to connect the LED die within the LED package to the circuit board of an LED module.
  • the LED module 20 can further comprise a lens 25 that is formed over the aperture 22 and the LED die 12. Therefore, as a lens covering the LED die 12 can be formed after the LED package 10 has been attached to the circuit board 21 of LED module 20, the LED package 10 does not require its own primary optic.
  • FIGS 6a and 6b illustrate further examples of an LED module 20 that includes the LED package 10 of Figure 4.
  • the LED package 10 is at least partially embedded within the circuit board 21.
  • the LED package 10 is at least partially contained/accommodated within the aperture 22 that extends through the circuit board 21 in a direction perpendicular to the first and second surfaces 21a, 21b, such that at least a portion of the conductive substrate 11 that is adjacent to the first (upper) surface 11a of the conductive substrate 11 is located within the aperture 22 itself. At least a portion of the conductive substrate 11 that is adjacent to the first (upper) surface 11a of the conductive substrate 11 is therefore surrounded by the sides of the circuit board 21 that define the aperture 22.
  • Embedding the LED package 10 within an aperture in the circuit board 21 of the LED module 20 allows for improved heat dissipation, by minimising the number of layers that are present in the thermal path between the LED die and the ultimate heat rejection (e.g. a heat sink attached to the lower surface of the LED module when incorporated into an LED luminaire or lamp), whilst also minimising the amount of light produced by the LED die 12 that is lost into the sides of the aperture 22.
  • the ultimate heat rejection e.g. a heat sink attached to the lower surface of the LED module when incorporated into an LED luminaire or lamp
  • the LED package 10 is partially embedded within the circuit board 21 with the first (upper) surface 11a of the conductive substrate 11 substantially aligned with the first surface 21a of the circuit board 21, such that the aperture 22 within the circuit board 21 is filled by the portion of the conductive substrate 11 that is located within the aperture 22 itself.
  • a first electrical connection between the circuit board 21 and the LED die 12 could be formed by the bonding/joining/attaching (e.g.
  • first electrical track 23a and the second electrical track 23b are both provided on the first (upper) surface 21a of the circuit board 21 then the first electrical track 23a and the second electrical track 23b would be electrically isolated from one another (e.g. by being physically separate from one another).
  • dielectric material at appropriately defined locations between the sides of the conductive substrate 11 (i.e. that are perpendicular to the first and second surfaces 11a, lib of the conductive substrate 11) and the sides of the circuit board 21 that define the aperture 22, so as to ensure that the conductive substrate 11 of the LED package 10 is electrically isolated from the second electrical track 23b provided on the upper surface 21a of the circuit board 21.
  • this could be achieved by providing that the dielectric material 13 also extends at least partially over one or more side faces lid, lie of the conductive substrate 11, as illustrated in the embodiment of Figure 6a.
  • the LED package 10 is partially embedded within the circuit board 21 with the first (upper) surface 11a of the conductive substrate 11 located within the aperture 22, such that the aperture 22 within the circuit board 21 is only partially filled by the portion of the conductive substrate 11 that is located within the aperture 22 itself.
  • Such a configuration reduces the amount of light emitted from the LED module 20 by eliminating any loss of light produced by the LED die 12 into the sides of the aperture 22.
  • a first electrical connection between the circuit board 21 and the LED die 12 would be formed by the bonding/joining/attaching of a surface of the conductive substrate 11 to a first electrical track 23a provided on the second (lower) surface 21b of the circuit board 21 that is abutted by/adjoins the surface of the conductive substrate 11 (e.g. using a fusible conductive material such as solder), whilst a second electrical connection would be provided by forming a wire bond 24 between the LED die 12 and a second electrical track 23b provided on the first (upper) surface 21a of the circuit board 21.
  • the circuit board 21 used to form the LED module 20 could have any of a variety constructions, such that the circuit board 21 could comprise any number of different layers of various materials, and the recess 22a could therefore extend into/through any number of the different layers that comprise the circuit board 21.
  • FIG. 7 illustrates a further example of an LED module 20 that includes another example embodiment of a simplified LED package 10 as described herein.
  • the conductive substrate 11 is formed such that the first surface 11a has a raised area/region 11c on which the LED die 12 is mounted.
  • the LED die 12 is raised up within the aperture 22 so as to reduce the amount of light produced by the LED die 12 that is lost into the sides of the aperture 22, and achieving a similar effect to that achieved in the embodiments illustrated in Figures 6a and 6.
  • Raising the LED die 12 within the aperture also makes the formation of the wire bond 24 easier.
  • Figure 8 illustrates a further example embodiment of a simplified LED package 10 as described herein.
  • the dielectric material 13 on the second (lower) surface lib of the conductive substrate 11 also extends at least partially over one or more side faces lid, lie of the conductive substrate 11.
  • the side faces lid, lie of the conductive substrate 11 are those surfaces of the conductive substrate 11 that extend between the first and second surfaces 11a, lib. Consequently, the side faces lid, lie of the conductive substrate 11 will typically be substantially perpendicular to the first and second surfaces 11a, lib; however, it is also possible that the side faces lid, lie could be angled relative to the perpendicular (e.g.
  • Extending the dielectric material 13 such that it at least partially covers the side faces of the conductive substrate 11 provides greater electrical isolation of the conductive substrate 11 and can assist in preventing electrical arcing/sparks to surrounding materials.
  • the dielectric material 13 would extend at least partially over all of the side faces of the conductive substrate of an LED package (e.g. over all four sides of a cuboid-shaped conductive substrate, over the single side of a cylindrical conductive substrate, etc).
  • the illustrated LED die 12 have vertical structures/architectures.
  • vertical LED die are formed such that the electrical contacts/electrodes are provided on opposite sides of the die (i.e. on the top and bottom).
  • the LED die 12 illustrated in Figures 4, 5, 6a, 6b, 7 and 8 therefore have a first electrode (not shown) on a first (lower) surface 12a of the LED die 12 that is bonded/joined/attached to the first surface 11a of the conductive substrate 11 (i.e. using a fusible conductive material).
  • the contact between the first electrode and the conductive substrate 11 therefore provides that, when LED packages 10 such as those illustrated in Figures 4, 5, 6a, 6b, 7 and 8 are formed into LED modules, the first electrical connection between the circuit board 21 and the LED die 12 can be formed by a junction of a surface of the conductive substrate 11 and a first electrical track 23a provided on either the first (upper) surface 21a or the second (lower) surface 21b of the circuit board 21 that is abutted by/adjoins the surface of the conductive substrate 11.
  • the second electrode (not shown) of the LED 12 is provided on a second (upper) surface 12a of the LED die 12 that faces away from the conductive substrate 11.
  • LED die can also have a lateral/horizontal structure/architecture, such that both of the electrical contacts/electrodes are provided on the same side of the die (i.e. on the top or bottom), and Figure 9 illustrates an alternative embodiment of a simplified LED package 10 as described herein in which the LED die 12 has a lateral structure.
  • lateral LED die can be described as "faceup" when both the p-electrode and n-electrode on the top side of the LED die (i.e. the side from which light exits the LED die), whilst lateral LED die that have both the p-electrode and n-electrode on the bottom side of the LED die (i.e.
  • the LED die 12 is provided with both a first electrode 121 and a second electrode 122 on the first (lower) surface 12a of the LED die 12.
  • the LED package 10 is therefore provided with a single distinct electrical connector/interconnect device 14 that is electrically isolated from the conductive substrate 11 and is provided specifically for forming an electrically conductive connection between the LED die 12 and an external electrical circuit.
  • the distinct electrical connector/interconnect device 14 comprises an isolated electrical pad 14a provided on/within the first surface 11a of the conductive substrate 11.
  • the electrical pad 14a extends part way along the first surface 11a of the conductive substrate 11 to an extent sufficient to enable the first electrode 121 of the LED die 12 to contact the electrical pad 14a and to also leave an exposed portion of electrical pad 14a available to form a contact with an external circuit, such as that provided by the electrical tracks on a lower surface of a circuit board.
  • the electrical pad 14a is electrically isolated from the conductive substrate 11 by a dielectric layer 14b that physically separates the electrical pad 14a from the conductive substrate 11.
  • Figure 10 then illustrates an LED module 20 that includes the LED package 10 of Figure 8.
  • the LED module 20 is formed by physically and electrically connecting the LED package 10 to a circuit board 21.
  • a first electrical connection between the circuit board 21 and the LED die 12 is provided by a junction formed by the bonding/joining/attaching of a surface of the conductive substrate 11 to a first electrical track 23a provided on the lower surface 21b of the circuit board 21 (e.g. using a fusible conductive material such as solder) that is abutted by/adjoins the surface of the conductive substrate 11.
  • the second electrical connection is then formed by the bonding/attaching/joining the electrical pad 14a provided on the first surface 11a of the conductive substrate 11 to a second electrical track 23b that is also provided on the lower surface 21b of the circuit board 21 that is abutted by/adjoins the electrical pad 14a of the conductive substrate 11 (e.g. using a fusible conductive material such as solder).
  • Figure 11 illustrates an alternative example of an LED module 20 that includes the LED package 10 of Figure 8.
  • the lateral LED package 10 is partially embedded within the circuit board 21 with the first (upper) surface 11a of the conductive substrate 11 substantially aligned with the first surface 21a of the circuit board 21, such that the aperture 22 within the circuit board 21 is filled by the portion of the conductive substrate 11 that is located within the aperture 22 itself.
  • a first electrical connection between the circuit board 21 and the LED die 12 is formed by the bonding/joining/attaching of a surface of the conductive substrate 11 to a first electrical track 23a provided on either the first (upper) surface 21a or the second (lower) surface 21b of the circuit board 21 that is abutted by/adjoins the surface of the conductive substrate 11 (with these alternatives being illustrated by the dashed lines in Figure 11), whilst a second electrical connection is provided by the bonding/attaching/joining of the electrical pad 14a provided on the first surface 11a of the conductive substrate 11 to a second electrical track 23b that is also provided on the first (upper) surface 21a of the circuit board 21 that is abutted by/adjoins the electrical pad 14a of the conductive substrate 11 (e.g. using a fusible conductive material such as solder).
  • the simplified LED package arrangement as described above is cheaper and more straightforward to manufacture than previous LED packages, as it is not necessary to provide the LED package with any more than one distinct/discrete electrical connector (i.e. lead, track and/or wire bond) for each of the LED die included in the LED package.
  • the process of using this simplified LED package arrangement in an LED module is no more complex than the process of using conventional LED packages in an LED module.
  • an LED module is manufactured using a conventional LED package such as that illustrated in Figure lb, it is necessary to bond the LED package to the upper surface of the circuit board, and to form first and second electrical connections between the primary electrical connectors of the LED package and the electrical tracks provided on the upper surface of the circuit board.
  • this will comprise using an adhesive or solder to bond the LED package to the circuit board, and soldering the primary electrical connectors to the electrical tracks.
  • LED packages that comprise a single LED die and no more than one distinct electrical connector
  • the LED packages described above could therefore equally comprise more than one LED die mounted on the conductive substrate. Consequently, for an LED package that comprises vertical LED die, such as that illustrated in Figures 4 to 7, it will be understood that multiple vertical LED die could be mounted onto the conductive substrate and the LED package provided with no distinct electrical connector. Similarly, for an LED package that comprises horizontal/lateral LED die, such as that illustrated in Figure 8, it will be understood that multiple lateral LED die could be mounted onto the conductive substrate and the LED package provided with no more than one distinct electrical connector for each lateral LED die.
  • an LED package that comprises multiple horizontal/lateral LED die then a number of these lateral LED die could share a single distinct electrical connector.
  • An LED package that comprises multiple lateral LED could therefore have only a single distinct electrical connector that is shared by all of the LED die, or a plurality of distinct electrical connectors that are each connected to one or more of the LED die provided that the total number of distinct electrical connectors is less than or equal to the number of LED die.

Abstract

According to a first aspect of the present invention there is provided a LED module. The LED module comprises a circuit board provided with an aperture that extends through the circuit board, and an LED package comprising one or more LED die mounted to a conductive substrate, the LED package being mounted to the circuit board with the one or more LED die aligned with the aperture. A first electrical connection between each of the one or more LED die and the circuit board is provided by a junction of a surface of the conductive substrate and a first electrical track provided on the circuit board, and a second electrical connection between each of the one or more LED die and the circuit board is provided by an interconnect device connecting the LED die to a second electrical track provided on the circuit board.

Description

LED PACKAGE AND LED MODULE
The present invention relates to light emitting diodes and relates particularly but not exclusively to an improved LED package, an LED module comprising the improved LED package, and a method of manufacturing an LED module comprising the improved LED package.
A light-emitting diode (LED) is a p-n junction semiconductor diode that emits photons when a current is applied. Figure la illustrates an example of a conventional LED die comprising p and n-type semiconductor layers, a substrate and electrical contact points. Before it can be used in a practical application, an LED chip or die must be packaged.
Figure lb illustrates an example of an LED package comprising the conventional LED die of Figure la, a packaging substrate/case, primary electrical connectors and commonly a primary optic in the form of a lens. In this example, the primary electrical connectors are provided by leads that extend out through the packaging substrate/case from beneath the LED die, where they connect to a pair of electrical contacts provided on the lower surface of the LED die (i.e. the LED die has a lateral/horizontal architecture). In an alternative arrangement of a conventional LED package, rather than having the leads connect to a pair of electrical contacts provided on the lower surface of the LED die, the LED die has a vertical architecture such that one of the electrical contacts is provided on the top of the LED die, and a wire bond can be used to connect this electrical contact to one of leads that extend out through the packaging substrate/case
One or more LED packages are then connected physically and electrically (i.e. by secondary electrical connectors) to a circuit board in order to form an LED module, such as that illustrated in Figure lc. One or more LED modules can then be assembled into an LED device, referred to as luminaire or lamp. Figure Id illustrates an example of an LED luminaire or lamp comprising an LED module, a heat sink, a reflector, and secondary optics (i.e. a secondary lens).
Conventional LED packages, such as that illustrated in Figure lb, are designed to be mounted onto an upper surface of a circuit board during the manufacture of an LED module. In other words, when included in an LED module, the surface of the LED package on which the LED die is mounted faces away from the circuit board, whilst the reverse surface of the LED package is bonded/connected to the circuit board, as illustrated in Figure lc. The LED package substrate that separates the LED die from the circuit board is therefore either electrically insulating or includes at least an electrically insulating layer so as to ensure that, other than the connections provided by the primary electrical connectors, the electrical contacts of the LED die are isolated from the electrical tracks provided on the surface of the circuit board.
Figure 2 illustrates an example of an alternative LED package arrangement that is designed to be mounted onto a lower surface of a circuit board when included in an LED module, such that the (upper) surface of the LED package on which the LED die is mounted is bonded/connected to the circuit board with the LED die aligned with an aperture in the circuit board. Figure 3 therefore illustrates an alternative LED module arrangement comprising the LED package arrangement of Figure 2.
The alternative LED package 1 illustrated in Figure 2 comprises an LED die 3 mounted onto a first (upper) surface 2a of a conductive substrate 2, and an electrically insulating substrate layer 4 is attached to a reverse, second (lower) surface 2b of the conductive substrate 2. In order to be connected to the lower surface of a circuit board, the primary electrical connectors are provided on the upper surface 2a of the LED package. In this example, the LED die 3 has a vertical architecture such that a first electrical connector/contact 5 is connected to the LED die 3 by a wire bond 7, and is separated from the conductive substrate 2 by an electrical insulation layer 8. A second electrical connector/contact 6 is then connected to the LED die 3 via the conductive substrate 2. The LED package 1 may also optionally be provided with an encapsulation layer 9 that covers the LED die 3.
This alternative LED package provides for improved heat dissipation efficiency as the conductive substrate 2 can be used as a heat spreader so as to remove heat from the LED die 3 by thermal conduction and to spread the heat from the relatively small area of the LED die. Moreover, as the LED package 1 is designed to be mounted beneath the circuit board when formed into an LED module, as illustrated in Figure 3, the lower surface of the LED package is exposed/uncovered. It is therefore possible to attach a heat-sink to the lower surface of the insulating substrate layer 4 using a thermal interface material, without having the circuit board interposed between them to disrupt the thermal path and limit the thermal dissipation.
According to a first aspect of the present invention there is provided a LED module. The LED module comprises a circuit board provided with an aperture that extends through the circuit board, and an LED package comprising one or more LED die mounted to a conductive substrate, the LED package being mounted to the circuit board with the one or more LED die aligned with the aperture. A first electrical connection between each of the one or more LED die and the circuit board is provided by a junction of a surface of the conductive substrate and a first electrical track provided on the circuit board, and a second electrical connection between each of the one or more LED die and the circuit board is provided by an interconnect device connecting the LED die to a second electrical track provided on the circuit board.
The junction of a surface of the conductive substrate and the first electrical track may be provided by a fusible electrically conductive material that joins the surface of the conductive substrate to the first electrical track.
The circuit board may comprise a first surface and a second surface, the first surface being opposed to the second surface, and the aperture may extend through the circuit board in a direction perpendicular to the first and second surfaces. The first electrical track may be provided on either the first surface or second surface of the circuit board, and the second electrical track may be provided on either the first surface or second surface of the circuit board.
The LED package may be mounted to the second surface of the circuit board.
The conductive substrate may comprise a first surface and a second surface, the first surface being opposed to the second surface, with the one or more LED die mounted to the first surface of the conductive substrate, and the LED package may then be mounted to the second surface of the circuit board with the first surface of the conductive substrate facing towards the second surface of the circuit board.
The conductive substrate may comprise a first surface and a second surface, the first surface being opposed to the second surface, the one or more LED die mounted to the first surface of the conductive substrate, and the LED package may be at least partially embedded within the circuit board with the first surface of the conductive substrate facing in the same direction as the first surface of the circuit board. The LED package may then be at least partially embedded within the circuit board such that the conductive substrate is at least partially contained/accommodated within the aperture that extends through the circuit board.
The aperture may be provided with a recess providing a ledge within the aperture to which the LED package is joined, such that the LED package is partially contained/accommodated within the aperture that extends through the circuit board.
The first electrical track may be provided on the second surface of the circuit board, and the first electrical connection between each of the one or more LED die and the circuit board may then be provided by a junction of a surface the conductive substrate and the first electrical track. The second electrical track may then be provided on either the first surface or the second surface of the circuit board.
The first electrical track may be provided on either the first surface or the second surface of the circuit board, and the first electrical connection between each of the one or more LED die and the circuit board may then be provided by a junction of a surface the conductive substrate and the first electrical track. The second electrical track may then be provided on either the first surface or the second surface of the circuit board.
Each of the one or more LED die may comprise a first surface and a second surface, the first surface being opposed to the second surface, and the first surface of the LED die may then be mounted to first surface of the conductive substrate.
For each of the one or more LED die, the interconnect device connecting the LED die to the second electrical track may be provided by any of a wire bond formed between the second surface of the LED die and the second electrical track, and an isolated electrical pad provided on the first surface of the conductive substrate and contacting the first surface of the LED die.
Each of the one or more LED die may have a vertical structure, and for each of the one or more LED die the interconnect device connecting the LED die to the second electrical track may then be provided by a wire bond formed between the second surface of the LED die and the second electrical track.
Alternatively, each of the one or more LED die may have a lateral structure, and for each of the one or more LED die the interconnect device connecting the LED die to the second electrical track may then be provided by an isolated electrical pad provided on the first surface of the conductive substrate that contacts the first surface of the LED die.
The LED module may further comprise a lens formed on the first surface of the circuit board over the aperture.
According to a second aspect of the present invention there is provided a method of manufacturing an LED module. The method comprises joining an LED package comprising one or more LED die mounted to a conductive substrate to a circuit board with the one or more LED die aligned with an aperture that extends through the circuit board, such that a first electrical connection between each of the one or more LED die and the circuit board is formed by a junction of a surface of the conductive substrate and a first electrical track provided on the circuit board, and forming a second electrical connection between each of the one or more LED die and the circuit board by connecting an interconnect device between the LED die and a second electrical track provided on the circuit board.
The junction of a surface of the conductive substrate and the first electrical track may be formed by joining the surface of the conductive substrate to the first electrical track using a fusible electrically conductive material.
For each of the one or more LED die, the step of connecting an interconnect device between the LED die and a second electrical track provided on the circuit board may comprises any of forming a wire bond between the LED die and the second electrical track, and connecting an isolated electrical pad provided on the first surface of the conductive substrate that is contact with the first surface of the LED die to the second electrical track.
The circuit board may comprise a first surface and a second surface, the first surface being opposed to the second surface, such that the aperture extends through the circuit board in a direction perpendicular to the first and second surfaces. The method may further comprise forming the aperture in the circuit board.
The method may further comprise forming a lens on the second surface of the circuit board over the aperture.
According to a third aspect of the present invention there is provided a light emitting diode (LED) package that consists of a conductive substrate that comprises a first surface and a second surface, the first surface being opposed to the second surface, one or more vertical LED die mounted to a first surface of the conductive substrate, wherein each of the one or more vertical LED die comprises a first surface and a second surface, the first surface being opposed to the second surface, and the first surface of the LED die is mounted to the first surface of the conductive substrate, and a dielectric material covering at least the second surface of the conductive substrate. The first surface of the conductive substrate may be provided with one or more raised areas on which the one or more LED die are mounted.
The LED package may consist of a plurality vertical LED die that are mounted to the first surface of the conductive substrate.
According to a fourth aspect of the present invention there is provided a light emitting diode (LED) package that consists of a conductive substrate that comprises a first surface and a second surface, the first surface being opposed to the second surface, one or more lateral LED die mounted to the first surface of the conductive substrate, wherein each of the one or more lateral LED die (comprises a first electrode and a second electrode, the first electrode being in contact with an isolated electrical pad provided on the first surface of the conductive substrate and the second electrode being in contact with the first surface of the conductive substrate; and a dielectric material covering at least the second surface of the conductive substrate. The first surface of the conductive substrate may be provided with one or more raised areas on which the one or more LED die are mounted.
The LED package may consist of a plurality of isolated electrical pads that are provided on the first surface of the conductive and a plurality of lateral LED die mounted to the first surface of the conductive substrate, with the first electrode of each of the plurality of lateral LED die being in contact with one of the plurality of isolated electrical pads.
The LED package may consist of a single isolated electrical pads provided on the first surface of the conductive substrate and a plurality of lateral LED die mounted to the first surface of the conductive substrate, with the first electrode of each of the plurality of lateral LED die being in contact with the isolated electrical pad.
The above and other features associated with the present invention will now be more particularly described by way of example only with reference to the accompanying drawings, in which:
Figure la illustrates a cross-sectional view of an example of a conventional LED die;
Figure lb illustrates a cross-sectional view of an example of a conventional LED package comprising the conventional LED die of Figure la;
Figures lc illustrates a cross-sectional view of an example of a conventional LED module comprising one or more of the conventional LED packages of Figure lb;
Figure Id illustrates a cross-sectional view of an example of a conventional LED device comprising the conventional LED module of Figure lc;
Figure 2 illustrates a cross-sectional view of an example of an alternative LED package arrangement;
Figures 3 illustrates a cross-sectional view of an example of an LED module comprising the alternative LED package of Figure 2;
Figure 4 illustrates a cross-sectional view of an example embodiment of a simplified LED package; Figure 5 illustrates a cross-sectional view of an example of an LED module comprising the simplified LED package of Figure 4;
Figure 6a illustrates a cross-sectional view of another example of an LED module comprising a simplified LED package;
Figure 6b illustrates a cross-sectional view of an alternative example of an LED module comprising a simplified LED package;
Figure 7 illustrates a cross-sectional view of an example of an LED module comprising a further example of a simplified LED package;
Figure 8 illustrates a cross-sectional view of a yet further example embodiment of a simplified LED package;
Figure 9 illustrates a cross-sectional view of another example embodiment of a simplified LED package;
Figure 10 illustrates a cross-sectional view of an example of an LED module comprising simplified LED package of Figure 8; and
Figure 11 illustrates a cross-sectional view of another example of an LED module comprising simplified LED package of Figure 8. It has been recognised by the present inventors that the alternative LED package arrangement described above in relation to Figure 2 can be simplified, thereby reducing the cost and complexity of manufacturing an LED package, and increasing the flexibility and density in the arrangement of multiple LED packages in an LED module. In particular, the present inventors have recognised that, for an LED package that is designed to be mounted to the lower surface of a circuit board, it is straightforward for one or both of the electrical connections between the LED die and the circuit board to be formed when mounting LED package to the circuit board.
Consequently, the present inventors have recognised that it is not necessary to provide the LED package with any more than one distinct/discrete electrical connector/interconnect device (i.e. lead, track and/or wire bond) for each LED die included in the LED package, wherein a distinct electrical connector/interconnect device is a separate physical component of the LED package whose specific purpose is to provide means for forming an electrically conductive connection between the LED die and an external electrical circuit.
Figure 4 therefore illustrates an example embodiment of a simplified LED package 10 as described herein. The LED package 10 comprises a conductive substrate 11, an LED die 12 mounted to a first (upper) surface 11a of the conductive substrate, a dielectric material 13 on a reverse, second (lower) surface lib of the conductive substrate, and does not comprise any distinct electrical connectors. In addition, the LED package does not include a primary optic. The LED package 10 illustrated in the example of Figure 4 therefore consists entirely of the conductive substrate 11, the LED die 12, and the dielectric material 13.
Figure 5 then illustrates an LED module 20 that includes the LED package 10 of Figure 4. The LED module 20 is formed by physically and electrically connecting the LED package 10 to a circuit board 21. In Figure 5, the circuit board 21 has a first (upper) surface 21a and a second (lower) surface 21b, and an aperture 22 that extends through the circuit board 21 in a direction perpendicular to the first and second surfaces 21a, 21b. The LED package 10 is located such that first surface 11a of the conductive substrate 11 of the LED package 10 (i.e. on which the LED die 12 is mounted) faces the second surface 21b of the circuit board 21. The LED die 12 mounted on the first surface 11a of the conductive substrate 11 is aligned with the aperture 22 such that light emitted by the LED die 12 will pass through the aperture 22.
A first electrical connection between the circuit board 21 and the LED die 12 is formed by the bonding/joining/attaching of a surface of the conductive substrate 11 to a first electrical track 23a provided on the lower surface 21b of the circuit board 21 (e.g. using a fusible conductive material such as solder) that is abutted by/adjoins the surface of the conductive substrate 11, whilst a second electrical connection is provided by forming a distinct electrical connector/interconnect device in the form of a wire bond 24 between the LED die 12 and a second electrical track 23b provided on the upper surface 21a of the circuit board 21. Consequently, the electrical connections are formed when the LED package 10 is connected to the circuit board 21 of the LED module 20, such that the LED package 10 does not require any distinct/discrete electrical connectors/interconnect devices. In contrast, both the conventional LED package illustrated in Figure lb and the alternative LED package illustrated in Figure 2 include distinct electrical connectors/interconnect devices (i.e. leads, tracks and/or wire bonds) that are formed as part of the LED package, and that are subsequently used to connect the LED die within the LED package to the circuit board of an LED module. In addition, the LED module 20 can further comprise a lens 25 that is formed over the aperture 22 and the LED die 12. Therefore, as a lens covering the LED die 12 can be formed after the LED package 10 has been attached to the circuit board 21 of LED module 20, the LED package 10 does not require its own primary optic.
Figures 6a and 6b illustrate further examples of an LED module 20 that includes the LED package 10 of Figure 4. In these examples, the LED package 10 is at least partially embedded within the circuit board 21. In particular, the LED package 10 is at least partially contained/accommodated within the aperture 22 that extends through the circuit board 21 in a direction perpendicular to the first and second surfaces 21a, 21b, such that at least a portion of the conductive substrate 11 that is adjacent to the first (upper) surface 11a of the conductive substrate 11 is located within the aperture 22 itself. At least a portion of the conductive substrate 11 that is adjacent to the first (upper) surface 11a of the conductive substrate 11 is therefore surrounded by the sides of the circuit board 21 that define the aperture 22.
Embedding the LED package 10 within an aperture in the circuit board 21 of the LED module 20 allows for improved heat dissipation, by minimising the number of layers that are present in the thermal path between the LED die and the ultimate heat rejection (e.g. a heat sink attached to the lower surface of the LED module when incorporated into an LED luminaire or lamp), whilst also minimising the amount of light produced by the LED die 12 that is lost into the sides of the aperture 22.
In the LED module embodiment illustrated in Figure 6a the LED package 10 is partially embedded within the circuit board 21 with the first (upper) surface 11a of the conductive substrate 11 substantially aligned with the first surface 21a of the circuit board 21, such that the aperture 22 within the circuit board 21 is filled by the portion of the conductive substrate 11 that is located within the aperture 22 itself. Such a configuration maximises the amount of light emitted from the LED module 20 by eliminating any loss of light produced by the LED die 12 into the sides of the aperture 22. In the LED module embodiment illustrated in Figure 6a, a first electrical connection between the circuit board 21 and the LED die 12 could be formed by the bonding/joining/attaching (e.g. using a fusible conductive material such as solder) of a surface the conductive substrate 11 to a first electrical track 23a provided on either the first (upper) surface 21a or the second (lower) surface 21b of the circuit board 21 (with these alternatives being illustrated by the dashed lines in Figure 6a) that is abutted/adjoined by the surface of the conductive substrate 11. A second electrical connection would then be provided by forming a wire bond 24 between the LED die 12 and a second electrical track 23b provided on the first (upper) surface 21a of the circuit board 21. In this regard, if the first electrical track 23a and the second electrical track 23b are both provided on the first (upper) surface 21a of the circuit board 21 then the first electrical track 23a and the second electrical track 23b would be electrically isolated from one another (e.g. by being physically separate from one another).
In such an embodiment, it may be preferable to provide dielectric material at appropriately defined locations between the sides of the conductive substrate 11 (i.e. that are perpendicular to the first and second surfaces 11a, lib of the conductive substrate 11) and the sides of the circuit board 21 that define the aperture 22, so as to ensure that the conductive substrate 11 of the LED package 10 is electrically isolated from the second electrical track 23b provided on the upper surface 21a of the circuit board 21. For example, this could be achieved by providing that the dielectric material 13 also extends at least partially over one or more side faces lid, lie of the conductive substrate 11, as illustrated in the embodiment of Figure 6a.
In the LED module 20 illustrated in Figure 6b the LED package 10 is partially embedded within the circuit board 21 with the first (upper) surface 11a of the conductive substrate 11 located within the aperture 22, such that the aperture 22 within the circuit board 21 is only partially filled by the portion of the conductive substrate 11 that is located within the aperture 22 itself. Such a configuration reduces the amount of light emitted from the LED module 20 by eliminating any loss of light produced by the LED die 12 into the sides of the aperture 22.
In the LED module embodiment illustrated in Figure 6b, a first electrical connection between the circuit board 21 and the LED die 12 would be formed by the bonding/joining/attaching of a surface of the conductive substrate 11 to a first electrical track 23a provided on the second (lower) surface 21b of the circuit board 21 that is abutted by/adjoins the surface of the conductive substrate 11 (e.g. using a fusible conductive material such as solder), whilst a second electrical connection would be provided by forming a wire bond 24 between the LED die 12 and a second electrical track 23b provided on the first (upper) surface 21a of the circuit board 21.
In such an embodiment, it may be preferable to provide an additional recess 22a within the aperture 22 that extends around the perimeter of aperture 22 from the second (lower) surface 21b of the circuit board 21, thereby forming a ledge/rim/lip within the aperture 22 that provides a surface onto which the LED package 10 can easily be bonded. However, the provision of such a recess 22a is not essential. Furthermore, whilst not shown in Figure 6b, the circuit board 21 used to form the LED module 20 could have any of a variety constructions, such that the circuit board 21 could comprise any number of different layers of various materials, and the recess 22a could therefore extend into/through any number of the different layers that comprise the circuit board 21.
Figure 7 illustrates a further example of an LED module 20 that includes another example embodiment of a simplified LED package 10 as described herein. In this example, the conductive substrate 11 is formed such that the first surface 11a has a raised area/region 11c on which the LED die 12 is mounted. By mounting the LED die 12 onto a raised area 11c on the surface of the conductive substrate 11, the LED die 12 is raised up within the aperture 22 so as to reduce the amount of light produced by the LED die 12 that is lost into the sides of the aperture 22, and achieving a similar effect to that achieved in the embodiments illustrated in Figures 6a and 6.. Raising the LED die 12 within the aperture also makes the formation of the wire bond 24 easier.
Figure 8 illustrates a further example embodiment of a simplified LED package 10 as described herein. In this example, the dielectric material 13 on the second (lower) surface lib of the conductive substrate 11 also extends at least partially over one or more side faces lid, lie of the conductive substrate 11. In this regard, the side faces lid, lie of the conductive substrate 11 are those surfaces of the conductive substrate 11 that extend between the first and second surfaces 11a, lib. Consequently, the side faces lid, lie of the conductive substrate 11 will typically be substantially perpendicular to the first and second surfaces 11a, lib; however, it is also possible that the side faces lid, lie could be angled relative to the perpendicular (e.g. sloped) and/or provided with a chamfer where they meet one or both of the first and second surfaces 11a, lib. Extending the dielectric material 13 such that it at least partially covers the side faces of the conductive substrate 11 provides greater electrical isolation of the conductive substrate 11 and can assist in preventing electrical arcing/sparks to surrounding materials. Preferably, the dielectric material 13 would extend at least partially over all of the side faces of the conductive substrate of an LED package (e.g. over all four sides of a cuboid-shaped conductive substrate, over the single side of a cylindrical conductive substrate, etc).
In the embodiments described above with respect of Figures 4, 5, 6a, 6b, 7 and 8, the illustrated LED die 12 have vertical structures/architectures. In this regard, vertical LED die are formed such that the electrical contacts/electrodes are provided on opposite sides of the die (i.e. on the top and bottom). The LED die 12 illustrated in Figures 4, 5, 6a, 6b, 7 and 8 therefore have a first electrode (not shown) on a first (lower) surface 12a of the LED die 12 that is bonded/joined/attached to the first surface 11a of the conductive substrate 11 (i.e. using a fusible conductive material). The contact between the first electrode and the conductive substrate 11 therefore provides that, when LED packages 10 such as those illustrated in Figures 4, 5, 6a, 6b, 7 and 8 are formed into LED modules, the first electrical connection between the circuit board 21 and the LED die 12 can be formed by a junction of a surface of the conductive substrate 11 and a first electrical track 23a provided on either the first (upper) surface 21a or the second (lower) surface 21b of the circuit board 21 that is abutted by/adjoins the surface of the conductive substrate 11. However, the second electrode (not shown) of the LED 12 is provided on a second (upper) surface 12a of the LED die 12 that faces away from the conductive substrate 11. Consequently, when LED packages 10 such as those illustrated in Figures 4, 5, 6a, 6b, 7 and 8 are formed into LED modules, a wire bond 24 is required between the second surface 12b of the LED die 12 and the second electrical track 23b provided on the upper surface 21a of the circuit board 21 in order to form the second electrical connection to the LED die 12.
In contrast, LED die can also have a lateral/horizontal structure/architecture, such that both of the electrical contacts/electrodes are provided on the same side of the die (i.e. on the top or bottom), and Figure 9 illustrates an alternative embodiment of a simplified LED package 10 as described herein in which the LED die 12 has a lateral structure. In this regard, lateral LED die can be described as "faceup" when both the p-electrode and n-electrode on the top side of the LED die (i.e. the side from which light exits the LED die), whilst lateral LED die that have both the p-electrode and n-electrode on the bottom side of the LED die (i.e. the side opposite to that from which light exits the LED die) can be referred to as "flip-chip" LED die. In the embodiment of Figure 9, the LED die 12 is provided with both a first electrode 121 and a second electrode 122 on the first (lower) surface 12a of the LED die 12. The LED package 10 is therefore provided with a single distinct electrical connector/interconnect device 14 that is electrically isolated from the conductive substrate 11 and is provided specifically for forming an electrically conductive connection between the LED die 12 and an external electrical circuit. In this embodiment, the distinct electrical connector/interconnect device 14 comprises an isolated electrical pad 14a provided on/within the first surface 11a of the conductive substrate 11. The electrical pad 14a extends part way along the first surface 11a of the conductive substrate 11 to an extent sufficient to enable the first electrode 121 of the LED die 12 to contact the electrical pad 14a and to also leave an exposed portion of electrical pad 14a available to form a contact with an external circuit, such as that provided by the electrical tracks on a lower surface of a circuit board. The electrical pad 14a is electrically isolated from the conductive substrate 11 by a dielectric layer 14b that physically separates the electrical pad 14a from the conductive substrate 11. Figure 10 then illustrates an LED module 20 that includes the LED package 10 of Figure 8. The LED module 20 is formed by physically and electrically connecting the LED package 10 to a circuit board 21. In Figure 10, a first electrical connection between the circuit board 21 and the LED die 12 is provided by a junction formed by the bonding/joining/attaching of a surface of the conductive substrate 11 to a first electrical track 23a provided on the lower surface 21b of the circuit board 21 (e.g. using a fusible conductive material such as solder) that is abutted by/adjoins the surface of the conductive substrate 11. The second electrical connection is then formed by the bonding/attaching/joining the electrical pad 14a provided on the first surface 11a of the conductive substrate 11 to a second electrical track 23b that is also provided on the lower surface 21b of the circuit board 21 that is abutted by/adjoins the electrical pad 14a of the conductive substrate 11 (e.g. using a fusible conductive material such as solder).
Figure 11 illustrates an alternative example of an LED module 20 that includes the LED package 10 of Figure 8. In this example, the lateral LED package 10 is partially embedded within the circuit board 21 with the first (upper) surface 11a of the conductive substrate 11 substantially aligned with the first surface 21a of the circuit board 21, such that the aperture 22 within the circuit board 21 is filled by the portion of the conductive substrate 11 that is located within the aperture 22 itself.
In the LED module embodiment illustrated in Figure 11, a first electrical connection between the circuit board 21 and the LED die 12 is formed by the bonding/joining/attaching of a surface of the conductive substrate 11 to a first electrical track 23a provided on either the first (upper) surface 21a or the second (lower) surface 21b of the circuit board 21 that is abutted by/adjoins the surface of the conductive substrate 11 (with these alternatives being illustrated by the dashed lines in Figure 11), whilst a second electrical connection is provided by the bonding/attaching/joining of the electrical pad 14a provided on the first surface 11a of the conductive substrate 11 to a second electrical track 23b that is also provided on the first (upper) surface 21a of the circuit board 21 that is abutted by/adjoins the electrical pad 14a of the conductive substrate 11 (e.g. using a fusible conductive material such as solder).
The simplified LED package arrangement as described above is cheaper and more straightforward to manufacture than previous LED packages, as it is not necessary to provide the LED package with any more than one distinct/discrete electrical connector (i.e. lead, track and/or wire bond) for each of the LED die included in the LED package. In addition, the process of using this simplified LED package arrangement in an LED module is no more complex than the process of using conventional LED packages in an LED module. In this regard, when an LED module is manufactured using a conventional LED package such as that illustrated in Figure lb, it is necessary to bond the LED package to the upper surface of the circuit board, and to form first and second electrical connections between the primary electrical connectors of the LED package and the electrical tracks provided on the upper surface of the circuit board. Typically, this will comprise using an adhesive or solder to bond the LED package to the circuit board, and soldering the primary electrical connectors to the electrical tracks.
It will be appreciated that individual items described above may be used on their own or in combination with other items shown in the drawings or described in the description and that items mentioned in the same passage as each other or the same drawing as each other need not be used in combination with each other. In addition, the expression "means" may be replaced by actuator, system, unit or device as may be desirable. Furthermore, although the invention has been described in terms of preferred embodiments as set forth above, it should be understood that these embodiments are illustrative only. Those skilled in the art will be able to make modifications and alternatives in view of the disclosure which are contemplated as falling within the scope of the appended claims. For example, whilst the embodiments described above and illustrated in the figures refer to LED packages that comprise a single LED die and no more than one distinct electrical connector, the skilled person will understand that multiple LED die can be included in a single LED package. The LED packages described above could therefore equally comprise more than one LED die mounted on the conductive substrate. Consequently, for an LED package that comprises vertical LED die, such as that illustrated in Figures 4 to 7, it will be understood that multiple vertical LED die could be mounted onto the conductive substrate and the LED package provided with no distinct electrical connector. Similarly, for an LED package that comprises horizontal/lateral LED die, such as that illustrated in Figure 8, it will be understood that multiple lateral LED die could be mounted onto the conductive substrate and the LED package provided with no more than one distinct electrical connector for each lateral LED die. Moreover, in the case of an LED package that comprises multiple horizontal/lateral LED die, then a number of these lateral LED die could share a single distinct electrical connector. An LED package that comprises multiple lateral LED could therefore have only a single distinct electrical connector that is shared by all of the LED die, or a plurality of distinct electrical connectors that are each connected to one or more of the LED die provided that the total number of distinct electrical connectors is less than or equal to the number of LED die.

Claims

An LED module (20) comprising:
a circuit board (21) provided with an aperture (22) that extends through the circuit board; and
an LED package (10) comprising one or more LED die (12) mounted to a conductive substrate (11), the LED package being mounted to the circuit board with the one or more LED die aligned with the aperture;
wherein a first electrical connection between each of the one or more LED die and the circuit board is provided by a junction of a surface of the conductive substrate and a first electrical track (23a) provided on the circuit board, and a second electrical connection between each of the one or more LED die and the circuit board is provided by an interconnect device (14, 24) connecting the LED die to a second electrical track (23b) provided on the circuit board.
The LED module as claimed in claim 1, wherein the junction of a surface of the conductive substrate (11) and the first electrical track (23a) is provided by a fusible electrically conductive material that joins the surface of the conductive substrate to the first electrical track.
The LED module as claimed in any preceding claim, wherein the circuit board (21) comprises a first surface (21a) and a second surface (21b), the first surface being opposed to the second surface, and the aperture (22) extends through the circuit board in a direction perpendicular to the first and second surfaces.
The LED module as claimed in claim 3, wherein the first electrical track (23a) is provided on either the first surface (21a) or second surface (21b) of the circuit board, and the second electrical track (23b) is provided on either the first surface (21a) or second surface (21b) of the circuit board.
The LED module as claimed in any of claims 3 or 4, wherein the LED package (10) is mounted to the second surface (21b) of the circuit board (21).
The LED module as claimed in claim 5, wherein the conductive substrate (11) comprises a first surface (11a) and a second surface (lib), the first surface being opposed to the second surface, and the one or more LED die (12) are mounted to the first surface (11a) of the conductive substrate, and the LED package (10) is mounted to the second surface (21b) of the circuit board with the first surface (11a) of the conductive substrate (11) facing towards the second surface (21b) of the circuit board (21).
The LED module as claimed in any of claims 1 to 5, wherein the conductive substrate (11) comprises a first surface (11a) and a second surface (lib), the first surface being opposed to the second surface, and the one or more LED die (12) are mounted to the first surface (11a) of the conductive substrate, and the LED package (10) is at least partially embedded within the circuit board (21) with the first surface (11a) of the conductive substrate (11) facing in the same direction as the first surface (21a) of the circuit board (21).
8. The LED module as claimed in claim 7, wherein the LED package (10) is at least partially embedded within the circuit board (21) such that the conductive substrate (11) is at least partially contained/accommodated within the aperture (22) that extends through the circuit board.
9. The LED module as claimed in claim 8, wherein the aperture (22) is provided with a recess (22a) providing a ledge within the aperture to which the LED package (10) is joined, such that the LED package is partially contained/accommodated within the aperture that extends through the circuit board.
10. The LED module as claimed in any of claims 3 to 6, wherein the first electrical track (23a) is provided on the second surface (21b) of the circuit board (21), and the first electrical connection between each of the one or more LED die (12) and the circuit board is provided by a junction of a surface the conductive substrate and the first electrical track (23a).
11. The LED module as claimed in claim 10, wherein the second electrical track (23b) provided on either the first surface (21a) or the second surface (21b) of the circuit board. 12. The LED module as claimed in any of claims 7 to 9, wherein the first electrical track (23a) is provided on either the first surface (21a) or the second surface (21b) of the circuit board (21), and the first electrical connection between each of the one or more LED die (12) and the circuit board is provided by a junction of a surface the conductive substrate and the first electrical track (23a).
13. The LED module as claimed in claim 12, wherein the second electrical track (23b) provided on either the first surface (21a) or the second surface (21b) of the circuit board.
14. The LED module as claimed in any preceding claim, wherein each of the one or more LED die (12) comprise a first surface (12a) and a second surface (12b), the first surface being opposed to the second surface, and the first surface (12a) of the LED die is mounted to first surface (11a) of the conductive substrate (11).
15. The LED module as claimed in claim 14, wherein, for each of the one or more LED die (12), the interconnect device connecting the LED die to the second electrical track is provided by any of a wire bond (24) formed between the second surface (12b) of the LED die (12) and the second electrical track (23b), and an isolated electrical pad (14) provided on the first surface (11a) of the conductive substrate (11) and contacting the first surface (12a) of the LED die (12).
16. The LED module as claimed in claim 15, wherein each of the one or more LED die (12) has a vertical structure, and for each of the one or more LED die (12) the interconnect device connecting the LED die to the second electrical track (23b) is provided by a wire bond (24) formed between the second surface (12b) of the LED die (12) and the second electrical track (23b).
17. The LED module as claimed in claim 15, wherein each of the one or more LED die (12) has a lateral structure, and for each of the one or more LED die (12) the interconnect device connecting the LED die to the second electrical track (23b) is provided by an isolated electrical pad (14) provided on the first surface (11a) of the conductive substrate (11) and contacting the first surface (12a) of the LED die (12).
18. The LED module as claimed in any preceding claim, and further comprising a lens (25) formed on the first surface (21a) of the circuit board (21) over the aperture (22).
19. A method of manufacturing an LED module comprising:
joining an LED package (10) comprising one or more LED die (12) mounted to a conductive substrate (11) to a circuit board (21) with the one or more LED die aligned with an aperture (22) that extends through the circuit board, such that a first electrical connection between each of the one or more LED die and the circuit board is formed by a junction of a surface of the conductive substrate and a first electrical track (23a) provided on the circuit board; and
forming a second electrical connection between each of the one or more LED die and the circuit board by connecting an interconnect device (14, 24) between the LED die and a second electrical track (23b) provided on the circuit board.
20. The method as claimed in claim 19, wherein the junction of a surface of the conductive substrate (11) and the first electrical track (23a) is formed by joining the surface of the conductive substrate to the first electrical track using a fusible electrically conductive material.
21. The method as claimed in any of claims 19 or 20, wherein, for each of the one or more LED die (12), the step of connecting an interconnect device (14, 24) between the LED die and a second electrical track (23b) provided on the circuit board comprises any of:
forming a wire bond (24) between the LED die (12) and the second electrical track (23b); and
connecting an isolated electrical pad (14) provided on the first surface (11a) of the conductive substrate (11) and contacting the first surface (12a) of the LED die (12) to the second electrical track (23b).
22. The method as claimed in any of claims 19 to 21, wherein the circuit board (21) comprises a first surface (21a) and a second surface (21b), the first surface being opposed to the second surface, and the aperture (22) extends through the circuit board in a direction perpendicular to the first and second surfaces. 23. The method as claimed in any of claims 19 to 22, and further comprising forming the aperture
(22) in the circuit board (21).
24. The method as claimed in any of claims 19 to 23, and further comprising forming a lens (25) on the second surface (21b) of the circuit board over the aperture.
25. A light emitting diode, LED, package (10) consisting of:
a conductive substrate (11) that comprises a first surface (11a) and a second surface (lib), the first surface being opposed to the second surface;
one or more vertical LED die (12) mounted to the first surface (11a) of the conductive substrate, wherein each of the one or more vertical LED die (12) comprises a first surface (12a) and a second surface (12b), the first surface being opposed to the second surface, and the first surface (12a) of the LED die is mounted to the first surface (11a) of the conductive substrate; and
a dielectric material covering at least a second surface (lib) of the conductive substrate (11).
26. The LED package as claimed in claim 25, wherein the LED package consists of a plurality of vertical LED die (12) that are mounted on the first surface (11a) of the conductive substrate (11).
27. A light emitting diode, LED, package (10) consisting of:
a conductive substrate (11) that comprises a first surface (11a) and a second surface (lib), the first surface being opposed to the second surface;
one or more lateral LED die (12) mounted to the first surface (11a) of the conductive substrate, wherein each of the one or more lateral LED die (12) comprises a first electrode
(121) and a second electrode (122), the first electrode (121) being in contact with an isolated electrical pad (14) provided on the first surface (11a) of the conductive substrate (11) and second electrode (122) being in contact with the first surface (11a) of the conductive substrate (11) ; and
a dielectric material covering at least a second surface (lib) of the conductive substrate (11).
The LED package as claimed in claim 27, wherein the LED package consists of a plurality of isolated electrical pads (14) that are provided on the first surface (11a) of the conductive substrate (11) and a plurality of lateral LED die (12) mounted to the first surface (11a) of the conductive substrate, the first electrode (121) of each of the plurality of lateral LED die being in contact with one of the plurality of isolated electrical pads (14).
29. The LED package as claimed in claim 27, herein the LED package consists of a single isolated electrical pads (14) provided on the first surface (11a) of the conductive substrate (11) and a plurality of lateral LED die (12) mounted to the first surface (11a) of the conductive substrate, the first electrode (121) of each of the plurality of lateral LED die being in contact with the isolated electrical pad (14).
30. The LED package as claimed in any of claims 27 to 29, wherein the first surface (11a) of the conductive substrate (11) is provided with one or more raised areas (11c) on which the one or more LED die (12) are mounted.
PCT/GB2014/053187 2013-10-25 2014-10-24 Led package and led module WO2015059499A2 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GBGB1318870.1A GB201318870D0 (en) 2013-10-25 2013-10-25 LED package and LED module
GB1318870.1 2013-10-25

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WO2015059499A3 WO2015059499A3 (en) 2015-06-18

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US11490520B2 (en) * 2018-01-30 2022-11-01 Vivo Mobile Communication Co., Ltd. Printed circuit board, method of manufacturing the same, and mobile terminal

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ATE425556T1 (en) * 2001-04-12 2009-03-15 Matsushita Electric Works Ltd LIGHT SOURCE COMPONENT WITH LED AND METHOD FOR PRODUCING IT
US20030058650A1 (en) * 2001-09-25 2003-03-27 Kelvin Shih Light emitting diode with integrated heat dissipater
US20070096132A1 (en) * 2005-11-01 2007-05-03 Jiahn-Chang Wu Coaxial LED lighting board
US20070176182A1 (en) * 2006-01-27 2007-08-02 Way-Jze Wen Structure for integrating LED circuit onto heat-dissipation substrate
US7547924B1 (en) * 2007-12-31 2009-06-16 Chien-Feng Lin Light-emitting diode structure
TW201246618A (en) * 2010-10-19 2012-11-16 Kyushu Inst Technology Led module device, method for manufacturing same, led package used for led module device, and method for manufacturing same

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US11490520B2 (en) * 2018-01-30 2022-11-01 Vivo Mobile Communication Co., Ltd. Printed circuit board, method of manufacturing the same, and mobile terminal

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