Close packing LED assembly with versatile interconnect architecture

#The invention relates to the electronic and optoelectronic arts. It is especially applicable to the packaging of light emitting diodes (LED's), and will be described with particular reference thereto. However, the invention will also find application in the packaging other electronic and optoelectronic devices, such as photodetectors, signal receivers, vertical cavity surface emitting lasers (VCSEL's), photovoltaic devices, and the like.

#Light emitting diodes (LED's) find application in fiber optical communications, lighting applications, display applications, and other applications where a compact, low voltage, rugged, and high efficiency light source is advantageous. In many LED applications, a plurality of LED's are advantageously arranged into an array or other pre-determined arrangement comprising similar or dissimilar LED types. In lighting or display applications, LED's emitting in the red, green, and blue regions are preferably closely packed to form a color “pixel” that blends the three colors. In this manner white light can be generated. Alternatively, by selectively varying the optical output intensity of the three colored LED's, a selected color can be generated. An array of such “pixels” can form a color display or an illuminating surface emitting white light, among other applications.

#The prior art includes fabrication of LED arrays on-chip. In this approach, semiconductor layers comprising the LED's are generated on a substrate, usually a semiconductor substrate, and individual LED's of the array are isolated by etching mesas in the LED layers. This approach is limited in application. The LED's are typically required to be all of one type. The choice of substrate is limited to those compatible with the semiconductor layer generation method. Many commercial LED's are formed from III-V compound semiconductor layers, and the substrates which are used for the growth of such layers, typically including GaAs and InP wafers, sapphire substrates, and the like, are often expensive, fragile, and of limited lateral area.

#The invention may take form in various components and arrangements of components, and in various steps and arrangements of steps. The drawings are only for purposes of illustrating a preferred embodiment and are not to be construed as limiting the invention.

#FIG. 1 shows an exemplary array of twelve rhombic substrates forming a hexagonal array of twenty-four components.

#FIG. 2 shows the geometry of an exemplary rhombic substrate.

#With reference to FIGS. 1 and 2, a modular mounting assembly 10 is described. A plurality of substrates 12 each have one or more components 14 arranged thereon. In the illustrated embodiment of FIG. 7, each substrate 12 has two LED components 14 arranged thereon. The plurality of substrates 12 are arranged in a selected manner to form the mounting assembly 10 that arranges the components 14 in a selected arrangement, such as the hexagonal arrangement of FIG. 1 comprised of twelve substrates 12 and twenty four LED components 14.

#In one embodiment shown in FIGS. 1 and 2, each substrate 12 has the shape of a rhombus, i.e. a parallelogram having four sides of essentially equal length L, with oppositely oriented angles equal. Thus, a rhombus can be specified by two angular parameters α and β, along with the side length L, as shown in FIG. 2. In the illustrated embodiment of FIG. 1, the angles α and β are 60° and 120°, respectively, so that each rhombic substrate 12 corresponds to a primitive unit cell of a hexagon, thus enabling particularly close packing of the components 14 such as in the assembly 10 shown in FIG. 1. Hexagonal symmetry is particularly advantageous because hexagons can be arranged to form densely packed two-dimensional arrays. Hexagonal symmetry also can be used to create three-dimensional structures such as spheres or geodesic-type domes.

#In another embodiment (not shown), α=β=90° so that a square unit cell substrate results. It will be appreciated that the rhombic shape provides a high degree of symmetry that enables arrangement of a plurality of rhombic substrates 12 into a wide range of selected spatial arrangements. Of course, other values for the angles α and β can also be used within the geometrical limitation that α+β=180° for the rhombic geometry shown in FIG. 2.