RED FLIP CHIP LIGHT EMITTING DIODE, PACKAGE, AND METHOD OF MAKING THE SAME

Abstract

Flip chip LEDs comprise a transparent carrier and an active material layer such as AlInGaP bonded to the carrier and that emits light between about 550 to 650 nm. The flip chip LED has a first electrical terminal in contact with a first region of the active material layer, and a second electrical terminal in contact with a second region of the active material layer, wherein the first and second electrical terminals are positioned along a common surface of the active material layer. Chip-on-board LED packages comprise a plurality of the flip chip LEDs with respective first and second electrical terminals interconnected with one another. The package may include Flip chip LEDs that emit light between 420 to 500 nm, and the flip chip LEDs are covered with a phosphorus material comprising a yellow constituent, and may comprise a transparent material disposed over the phosphorus material.

Claims

1-38. (canceled)

39. A method of making a flip chip light emitting diode comprising the steps of: forming a layer of active material on a substrate; attaching a carrier to a surface of the active material layer opposite the substrate; removing the substrate from the active material layer to expose a surface of the active material layer opposite the carrier; and forming a pair of electrodes on the exposed surface of the active material layer for providing an electrical connection with electrical contacts of a connection member.

40. The method of claim 39, wherein the substrate has a crystalline lattice matching the crystalline lattice of the layer of active material.

41. The method of claim 39, wherein the carrier is formed from a material transparent to a wavelength of light emitted from the active material layer.

42. The method of claim 39, wherein the carrier has a continuous construction extending along the surface of the active material layer.

43. The method of claim 39, wherein a surface of the carrier opposite the active material layer is free of electrodes.

44. The method of claim 39, wherein during the step of attaching, the carrier is bonded to the active material layer by a transparent adhesive to provide a transparent interface therebetween, wherein the carrier is in direct contact with the transparent adhesive and the transparent adhesive is in direct contact with the active material layer.

45. The method of claim 39, wherein during the step of forming, a first electrode extends a partial depth from the active material layer surface to a first region of the active material, and a second electrode extends along a second region of the active material active material layer at the active material layer surface.

46. The method of claim 39, wherein the first and second electrodes are electrically isolated from one another.

47. A light emitting diode package comprising the flip chip light emitting diode made according to the method of claim 39, wherein the flip chip light emitting diode is positioned adjacent a second flip chip light emitting diode and emits a different wavelength of light, wherein one or both of the flip chip light emitting diodes are encapsulated with a phosphor material.

48. A method for making a flip chip light emitting diode comprising the steps of: forming a thickness of an active material onto a substrate having a crystalline lattice matching the crystalline lattice of the active material; attaching a carrier to a surface of the active material opposite the substrate, wherein the carrier is formed from a material transparent to a wavelength of light emitted from the active material; removing the substrate from the active material to expose a surface of the active material; and forming a pair of electrodes on the exposed active material surface, wherein a first electrode extends a partial depth into the active material to connect with a first region and a second electrode connected with a second region on a surface of the active material, wherein the first and second electrodes are electrically isolated from one another.

49. The method of claim 48, wherein the carrier is bonded to the active material by a transparent adhesive, and wherein the carrier is in direct contact with the transparent adhesive that is in direct contact with the active material.

50. The method of claim 48, wherein the pair of electrodes are positioned and configured for connecting with electrical contacts of an adjacent connection member positioned adjacent the active material exposed surface.

51. The method of claim 48, wherein the first and second electrodes are electrically isolated from one another by an insulating layer that is formed along a portion of the active material surface, and wherein a surface of the carrier opposed the active material is free of electrodes.

52. A method of making a flip chip light emitting diode package comprising the steps of: making a first flip chip light emitting diode by: forming an active material onto a substrate, wherein the substrate has a crystalline lattice matching a crystalline lattice of the active material; attaching a carrier to a surface of the active material opposite the substrate; removing the substrate from the active material to expose a surface of the active material; and forming a pair of electrodes on the exposed surface of the active material for connecting with electrical contacts of an adjacent connection member positioned adjacent the pair of electrodes; and combining the first flip chip light emitting diode with a second flip chip light emitting diode such that the first and second flip chip emitting diodes are positioned adjacent one another such that respective electrodes from the first and second flip chip emitting diodes are oriented to make contact with electrical contacts of a connection member to form a flip chip light emitting diode package.

53. The method of claim 52, wherein the carrier is transparent to a wavelength of light emitted from the active material.

54. The method of claim 52, wherein the carrier has a continuous construction extending throughout the active material surface and is free of electrodes.

55. The method of claim 52, wherein a first electrode extends from the surface of the active material a partial depth to connect with an active material first region, and a second electrode disposed on the surface of the active material to contact with an active material second region.

56. The method of claim 55, comprising forming an insulating layer along the exposed surface of the active material that electrically isolates the first electrode from the second electrode.

57. The method of claim 52, wherein the first flip chip light emitting diode emits light in a first wavelength range, and the second flip chip light emitting diode emits light in a second wavelength range that is different from the first wavelength range.

58. The method of claim 52 further comprising: disposing a phosphor material over one or both of the first and second light emitting diodes; and disposing a light transparent material over the phosphor material and the first and second flip chip light emitting diodes.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] These and other features and advantages of light-emitting diodes, assemblies and methods for making the same as disclosed herein will be appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings.

[0010] FIG. 1 illustrates a flip chip constructed to emit light in a blue wavelength;

[0011] FIG. 2 is a cross-sectional side view of an example light emitting diode as disclosed herein constructed to emit light in a red wavelength;

[0012] FIGS. 3a to 3e illustrates different steps in making the light emitting diode as disclosed herein;

[0013] FIG. 4 is a cross-sectional illustration of an example light emitting diode as disclosed herein;

[0014] FIG. 5 is a schematic side view of an example light emitting assembly/package comprising a blue light emitting diode and a light emitting diode as disclosed herein; and

[0015] FIG. 6 is a schematic side view of an example light emitting assembly/package comprising a blue light emitting diode and a light emitting diode as disclosed herein.

DETAILED DESCRIPTION

[0016] Light emitting diodes (LEDs) as disclosed herein are specially constructed having a flip chip architecture to emit light in yellow, amber and/or red wavelengths, and in an example in red wavelength of from about 550 to 650 nm. Such flip chips are referred to herein as red flip chip LEDs, and methods for making the same and packaging the same with other LEDs to provide an LED assembly/package capable of providing a multi-color output to meet the need of multi-color lighting applications are disclosed herein.

[0017] FIG. 1 illustrates a flip chip LED 10 constructed from materials enabling it to emit light in a blue wavelength in the range of from about 400 to 500 nm, herein referred to as a blue flip chip LED. In an example, the blue flip chip LED comprises an active material 12 formed for example from GaN that has been grown, e.g., epitaxially grown, onto a transparent substrate 14 such as one formed from sapphire or the like having a compatible crystalline lattice structure as GaN. The blue flip chip LED includes a pair of electrodes 16 and 18, e.g., P and N electrodes, disposed on one side of the LED 10, that extend to different regions of the GaN active material 12, and that facilitate electrical connection of the blue flip chip LED by connecting with respective electrical contacts opposite from and adjacent the blue flip chip LED, i.e., along one side of the blue flip chip LED.

[0018] FIG. 2 illustrates a flip chip LED 20 as disclosed herein construction from material enabling it to emit light in a red wavelength in the range of from about 550 to 650 nm, herein referred to as a red flip chip LED. Although it is to be understood that such flip chip LEDs as disclosed herein may also be constructed to emit light in the yellow and/or amber wavelengths. In an example, the red flip chip LED comprises an active layer 22 formed from a material capable of emitting such red wavelength light. In an example, the active material comprises AlInGaP. The active layer 22 is bonded or otherwise attached to a carrier 24 that is transparent to light emitted in such red wavelength. In an example, the carrier material can be selected from the group of materials including sapphire, glass, quartz, AIN, Gap and combinations thereof. In an example, the carrier is formed from sapphire. The red flip chip LED 20 includes a pair of electrodes 26 and 28, e.g., P and N electrodes, disposed on one side of the LED 20, that each extend to different regions of the AlInGaP active layer 22, and that facilitate electrical connection of the red flip chip LED by connecting with respective electrical contacts opposite from and adjacent the red flip chip LED, i.e., along one side of the red flip chip LED.

[0019] FIGS. 3a to 3e illustrate different stages of forming an example red flip chip LED as disclosed herein. Referring to FIG. 3a, in an initial stage of making construction 30, a layer of the active material 32 such as AlInGaP is epitaxially grown by known technique on a substrate 34. The substrate is selected from the group of materials having a crystalline lattice matching the crystalline lattice of the active material. In an example, where the active material is AlInGaP, the substrate is formed from GaAs. A desired layer thickness of the active material is grown onto the substrate as called for by the particular application.

[0020] Referring to FIG. 3b, in another stage of making construction 40, a carrier 42 is attached to the exposed surface of the active material 32 opposite from the substrate 34. The carrier can be selected from the materials noted above that is transparent to light in the red wavelength. The carrier 42 is bonded to the active material surface by transparent adhesive bond, fusion bond, and the like so that the interface between the active material and the carrier is transparent to permit light emitted from the active layer to pass through interface and through the carrier 42. Alternatively, the carrier may be provided in the form of a thick content of silicone or other transparent resin material that is bonded to the active material layer. At this stage of the process, the construction 40 comprises the active material 32 interposed or sandwiched between the carrier 42 on one side and the substrate 34 on an opposite side.

[0021] Referring to FIG. 3c, in another stage of making construction 50, the substrate (34 in FIG. 3b) is removed from the active material 32, thereby exposing a surface 52 of the active material 32. The substrate may be removed by etching process, by cutting process, and the like, or by other techniques and/or methods know in the art. The carrier 42 remains bonded to the active material.

[0022] Referring to FIG. 3d, in another stage of making construction 60, after the substrate has been removed and the surface 52 of the active material 32 exposed, electrodes 62 and 64, e.g., P and N electrodes, are formed along different sections of the construction, and portions 66 of the active material are removed for subsequent dicing to form LED dies. The carrier 42 remains bonded to the active material. FIG. 3e illustrates a further stage of making the construction 70, wherein the construction has been flipped over with the electrodes 62 and 64 positioned along a bottom portion of the construction 70 and attached with the active material 32. At this stage of making, the construction 70 has been subjected to a dicing process for forming individual dies 72, 74, and 76 therefrom. The carrier 42 remains bonded to the active material in each of the so-formed dies.

[0023] FIG. 4 illustrates a cross-sectional side view of a red flip chip LED 80 as disclosed herein. In an example, during the method step illustrated in FIG. 3d, the electrodes are formed using a buried contact process. As shown, a portion 84 of the active material 82 is removed a determined depth from the surface 52 to reach a first region 86 of the active material, e.g., a N region. An electrically insulating material 88 is disposed onto the surface 52 and into the depth of the active material to insulate a first electrode 90, e.g., an N electrode, from making contact with other regions of the active material. A second electrode 92, e.g., a P electrode, is formed on the surface 52 of the active material 82, e.g., a P region, and is electrically isolated from the first electrode and connects with a surface region 87 of the active material. If desired, the surface of one or both of the electrodes can be enlarged or increased or otherwise configured to facilitate accommodating a particular LED package/assembly. In an example, one of the electrodes, e.g., the P electrode, may be construed having surface area that is greater than the other electrode, e.g., that may occupy 95 percent or so of the electrical contact area for the LED. It is to be understood that the particular size and/or configuration of the electrodes can and will vary depending on the particular application and electrical connection member or substrate.

[0024] FIG. 5 schematically illustrates a construction, package, or assembly 100 comprising a blue flip chip LED 102 that is positioned next to a red flip chip LED 104 as disclosed herein, wherein both flip chip LEDs are packaged together on a member 105. In this example, both the blue flip chip LED 102 and the red flip chip LED 104 are covered or encapsulated by a phosphor material 106 having a yellow constituent. In one example, the phosphor material covering the blue flip chip LED may have a different composition or amount of the yellow constituent, e.g., a greater amount, than the phosphor material covering the red flip chip LED. In such embodiment, the amount of the yellow constituent can be different to enable the assembly to emit light having a desired wavelength, e.g., an efficient warm while wavelength. In another embodiment, the phosphor material covering the blue flip chip LED and the red flip chip LED may have the same composition or amount of the yellow constituent. In such embodiment, where the phosphor material is the same, it may be desired that the concentration of the yellow constituent avoids or minimally overlaps light emitted from the red flip chip LED. The assembly 100 further comprises a transparent layer of material 108 that is disposed over the phosphor material. In an example, the transparent layer of material may comprise a silicone material.

[0025] FIG. 6 schematically illustrates a construction, package, or assembly 120 comprising a blue flip chip LED 122 that is positioned next to a red flip chip LED 124 as disclosed herein, wherein both flip chip LEDs are packaged together on a member 125. In this example, only the blue flip chip LED 122 is covered or encapsulated by a phosphor material 126 having a yellow constituent and the red flip chip LED 124 is not covered or encapsulated by the phosphor material. In such embodiment, the amount of the yellow constituent is provided to enable the assembly to emit light having a desired wavelength, e.g., an efficient warm while wavelength, without having to cover the red flip chip LED. The assembly 120 further comprises a transparent layer of material 128 that is disposed over the phosphor material covering the blue flip chip LED and over the red flip chip LED. In an example, the transparent layer of material may comprise a silicone material.

[0026] A feature of red flip chip LEDs, packaging, constructions and/or assemblies comprising the same, and methods of making as disclosed herein is that such enables use of flip chip architecture for introducing LEDs capable of emitting light in a red wavelength with other flip chip LEDs, e.g., blue flip chip LEDs, for the purpose of meeting needs of a variety of multi-color light applications, and efficiently being able to do so using LED assemblies already configured to accommodate such flip chip LED architecture, such as chip-on board LED packaging.

[0027] Although certain specific embodiments have been described and illustrated for purposes or reference, it is to be understood that the disclosure and illustrations as provided herein not limited to the specific embodiments. Accordingly, various modifications, adaptations, and combinations of various features of the described embodiments can be practiced without departing from the scope what has been disposed herein including in the following passages.