Jetting a Highly Reflective Layer Onto an LED Assembly

Abstract

A layer of Highly Reflective (HR) material is deposited by jetting microdots of the HR material in liquid form onto a substrate and then allowing the HR material to harden. In one example, the HR layer is the HR layer of a white LED assembly. The HR layer is jetted onto the substrate around LED dice of the assembly after die attach and wire bonding have been completed. The HR material can be made to flow laterally so that areas of the substrate under wire bonds are coated with HR material, so that HR material contacts side edges of the LED dice, and so that HR material contacts the inside side edge of a retaining ring. By jetting the HR material in this way, the amount of substrate that is not covered with HR material is reduced, thereby improving the light efficiency of the resulting LED assembly.

1 - 25  (canceled) 
     
     
         26 . An apparatus comprising:
 a substrate having an upper surface;   a Light Emitting Diode (LED) die having a plurality of side edges, wherein the LED die is disposed on a first part of the upper surface of substrate; and   a layer of highly reflective (HR) material disposed on a second part of the upper surface of the substrate such that the layer does not extend under the LED die and does not extend over the LED die but such that the layer contacts at least one of the side edges of the LED die.   
     
     
         27 . The apparatus of  claim 26 , further comprising:
 a bond wire attached to the LED die, wherein the layer of HR material extends under the bond wire between the bond wire and the substrate.   
     
     
         28 . The apparatus of  claim 26 , wherein the layer of HR material is more than 10 microns thick, and wherein the HR material comprises titanium. 
     
     
         29 . The apparatus of  claim 26 , wherein the HR material has a reflectivity of more than 85 percent. 
     
     
         30 . The apparatus of  claim 26 , wherein the upper surface of the substrate forms a well, wherein the LED die is disposed in the well, and wherein at least a portion of the layer of HR material is disposed in the well. 
     
     
         31 . The apparatus of  claim 26 , wherein the upper surface of the substrate has a nonplanar shape, and wherein the layer of HR material is substantially conformal to the upper surface but does not cover the LED die. 
     
     
         32 . The apparatus of  claim 26 , wherein the layer of HR material comprises titanium dioxide and silicone. 
     
     
         33 . The apparatus of  claim 26 , wherein the HR material has a viscosity less than 1100 centipois (cP) at room temperature when deposited on the second part of the upper surface of the substrate. 
     
     
         34 . The apparatus of  claim 26 , wherein the layer of HR material is substantially planar, wherein there is a window in the layer of HR material, and wherein the LED die is disposed in the window. 
     
     
         35 . The apparatus of  claim 26 , wherein the substrate is a printed circuit board. 
     
     
         36 . An apparatus comprising:
 a substrate having an upper surface;   a Light Emitting Diode (LED) die that is disposed on a first part of the upper surface of substrate; and   a layer of highly reflective (HR) material disposed on a second part of the upper surface of the substrate such that the layer of HR material does not extend under the LED die and does not extend over the LED die, wherein the layer of HR material has a reflectivity of at least 85 percent.   
     
     
         37 . The apparatus of  claim 36 , wherein the LED die has a plurality of side edges, and wherein the layer of HR material contacts at least one of the side edges of the LED die. 
     
     
         38 . The apparatus of  claim 36 , wherein none of the upper surface of the substrate is not covered by the HR material between the LED die and the layer of HR material. 
     
     
         39 . The apparatus of  claim 36 , further comprising:
 a bond wire attached to the LED die, wherein the layer of HR material extends under the bond wire between the bond wire and the substrate.   
     
     
         40 . The apparatus of  claim 36 , wherein the layer of HR material is more than 10 microns thick. 
     
     
         41 . The apparatus of  claim 36 , wherein the layer of HR material comprises titanium dioxide and silicone. 
     
     
         42 . The apparatus of  claim 36 , wherein the upper surface of the substrate forms a well with sidewalls, wherein the LED die is disposed in the well, and wherein at least a portion of the layer of HR material is disposed on the sidewalls of the well. 
     
     
         43 . The apparatus of  claim 36 , wherein the upper surface of the substrate has a nonplanar shape, and wherein the layer of HR material is substantially conformal to the upper surface but does not cover the LED die. 
     
     
         44 . The apparatus of  claim 36 , wherein the HR material has a viscosity less than 1100 centipois (cP) at room temperature when deposited on the second part of the upper surface of the substrate. 
     
     
         45 . The apparatus of  claim 36 , wherein the layer of HR material is substantially planar, wherein there is a window in the layer of HR material, and wherein the LED die is disposed in the window.