Low Profile and High Efficiency Light Device for Backlighting Applications

Abstract

A light source having a flexible substrate and a plurality of dies having LEDs is disclosed. The light source can be conveniently utilized to provide an extended light source by bonding the light source to a suitable light pipe. The substrate is divided into first and second regions. The dies are bonded to the substrate in a first region. A portion of the surface of the substrate in the second region is reflective. The substrate is bent such that the second region forms a reflector that reflects light that would otherwise be emitted in a non-useful direction to a more useful direction. The substrate can be constructed from a three layer flexible circuit carrier in which the dies are mounted on a bottom metal layer to provide an improved thermal path for heat generated in the dies.

1 . A light source comprising:
 a flexible substrate having a dielectric layer sandwiched between top and bottom metal layers, said flexible substrate being divided into first and second regions; and   a plurality of dies bonded to said bottom layer in said first region, each die comprising a semiconductor light emitting device that emits light, said first region being characterized by a normal to said bottom layer in said first region, at least one of said top and bottom metal layers comprising a plurality of electrical traces for connecting said dies to circuitry that is external to said light source;   wherein said top metal layer of said substrate is reflective in said second region, said substrate being bent such that said first region is at an angle with respect to said second region and a portion of said light emitted from said dies at an initial angle greater than zero to said normal striking said second region and being reflected therefrom into a direction having an angle with respect to said normal that is less than said initial angle.   
     
     
         2 . The light source of  claim 1  wherein said flexible substrate has a thickness of less than 600 μm. 
     
     
         3 . The light source of  claim 1  wherein said second region comprises a reflective layer bonded to said top metal layer. 
     
     
         4 . The light source of  claim 1  wherein said dies are covered by a layer of encapsulant in said first region. 
     
     
         5 . The light source of  claim 1  wherein said substrate comprises a connector region outside of said first region and having a plurality of electrical contacts connected to said traces, said connector region being configured to mate to a connector that is external to said light source. 
     
     
         6 . The light source of  claim 1  further comprising a rigid member bonded to said bottom metal layer. 
     
     
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