HK1062501B - Semiconductor light emitting element formed on a clear or translucent substrate - Google Patents

Description

Semiconductor light emitting element formed on transparent or translucent substrate

Technical Field

The present invention relates generally to electronic devices and, more particularly, to semiconductor light emitting elements formed on and disposed on transparent or translucent substrates to provide more efficient and uniform light distribution, thereby improving the viewing of articles or objects at night or in dark light environments. The substrate may be formed by or as part of a protective housing, lens or cover for the object to be illuminated.

Background

Lighting is widely used in the electronics industry, ranging from cellular phones, calculators, watches, palm computers, global positioning units and positioning devices. Lighting devices are also used in many other industries, such as automotive, signage, advertising, and decoration.

Light emitting diodes offer many advantages over competing light emitting elements, such as electroluminescent, phosphorescent, fluorescent, and LCD and incandescent elements, in terms of, for example, size, price, color variability, reliability, and power consumption.

Semiconductor light emitting diodes have been used in cellular phones, watches, and other electronic devices, but as described in us patent 6017127-Timex, 3899871-Seiko, 4115994-Tomlinson, their illumination is limited because they are placed underneath, embedded in a crystal, or on the side of a light transmissive object that receives illumination.

Electroluminescence, hereinafter referred to as EL, has been widely used in the electronics industry and is often placed beneath an object or object, such as a watch dial or other surface, as described in us patent 3,749,977-Sliker, 4775964-Timex, 4208869-Hanaoka. In these references, direct illumination is provided upward toward the viewer, and any aesthetic angle is restricted. Another disadvantage of ELs is that they require complex ancillary circuitry and provide limited color to the consumer market.

Disclosure of Invention

It is therefore an object of the present invention to provide an improved and efficient lighting device for viewing objects or objects, by arranging lighting means directing light towards the object to be illuminated, so as to be easier to view, more efficient and less irritating to a viewer.

It is a further object of the present invention to eliminate the packaging of semiconductor light emitting diodes, including the reflective directional taper and the surrounding glass or plastic protective sleeve, thereby leaving only the original form of the light emitting element which radiates at a 180 degree angle when placed on the lower surface of a transparent or translucent substrate, and which is virtually invisible to a non-emitting light emitting device when in the off mode.

It is another object of the present invention to provide an illumination device for electronic devices that eliminates the use of any EL as the primary illumination source and its associated circuitry, such as: cellular phones, watches, palm-top computers, global positioning units, positioning devices, automobiles, signs, advertising, and decorative devices.

It is another object to combine the red, green, and blue configured semiconductor light emitting diode chips, collectively or in selected substrate areas, independently regulated by a circuit or ASICS chip with current limiting resistors to provide unlimited spectral color.

Another object is to allow constant or pre-programmed lighting variations that can be initiated by a power supply with pre-programmed electronic circuits or programmable ASICS chips, controlled by actuation switches that can be placed in close proximity to an article or object.

These and other objects of the present invention, along with features and advantages thereof, will become apparent from the following detailed description of the preferred embodiments, the appended claims, and the accompanying drawings.

A lighting device is disclosed herein that is constructed from a transparent, translucent, or opaque substrate. A plurality of conductive lines are formed on a substrate by a thin film deposition technique. The wires may include several coextensive layers including a chromium layer, a nickel layer, and a gold layer. A protective layer is then applied to cover and protect the wires.

The device also includes one or more light-emitting elements, each element being composed of a semiconductor material forming a semiconductor junction. It is important that no lens is provided to concentrate the light emitted by these elements, thereby ensuring that the light emitted from the device is uniformly distributed. Preferably, the or each light emitting element is encapsulated in a flip chip having a connection flange on one side. Thus, the chip can be directly connected to the wire.

The device may be made up of several light emitting elements arranged in groups of multiple colors. Each group includes elements of red, green, and blue. The groups may then be activated to form a still or moving color image.

Drawings

FIG. 1 depicts a plan view of a lighting device constructed in accordance with the present invention;

FIG. 2 is a cross-sectional view of the device of FIG. 1;

FIG. 3 is an enlarged cross-sectional view of the lighting device with wire details;

FIG. 4 depicts a cross-sectional view of a watch incorporating the subject illumination device;

FIG. 5 is an enlarged cross-sectional view of the watch of FIG. 4; and

fig. 6 shows a substrate with multi-color light emitting elements.

Detailed Description

Figures 1 and 2 illustrate a lighting device constructed in accordance with the present invention. The apparatus 10 includes a substrate 12, which in one embodiment of the invention is constructed of a transparent or translucent material such as glass, quartz, or crystal. The substrate may be circular, rectangular, square, as shown in fig. 1, or any other regular or irregular shape as desired. The two wires 14, 16 are formed on the substrate using semiconductor technology, as will be described in more detail below. The conductors 14, 16 extend from two connectors 18A, 18B, the two connectors 18A, 18B preferably being positioned near the edge of the substrate 12. The other ends of the wires 14, 16 are constituted by pads 20A, 20B, respectively. Light emitting element 22 is fixed to pads 20A, 20B (element 22 is shown by a dotted line in fig. 1). Preferably, the element 22 is provided in the form of a flip-chip having a connecting flange (not shown) on only one surface 22A. Flip chips and methods of attaching flip chips to substrates are disclosed, for example, in U.S. patent No.5,869,886 (incorporated herein by reference). Thus, the component 22 can be securely mounted on the substrate 12 without any connectors or leads on its upper surface 22A. Element 22 is oriented such that when it is excited by the current in wires 14 and 16, it emits light as shown by ray R in fig. 2. Alternatively, instead of flip-chip mounting, the element 22 may be a light emitting element having a line on each of the surfaces 22A and 22B, as shown in commonly known U.S. Pat. No.6,106,127, which is incorporated herein by reference. Such light emitting elements are available in various colors from Agilent Technologies, a subsidiary of Hewlett Packard Company, and Sharp Corporation, Japan.

Light emitting diodes are semiconductor devices that are readily available in a variety of sizes, power output colors, configurations, and the like. A typical light emitting diode includes a light emitting element and a lens. The light emitting element is composed of two semiconductor materials forming a junction, and when a current flows through the junction, light is emitted. The emitted light is then intercepted by the lens and directed in a predetermined direction. To the best of the inventors' knowledge, no lighting device is currently available that has only light emitting elements and no lens. However, the present inventors have disclosed that light emitting diode elements without lenses can be effectively utilized, while disclosing how best this element 22 can be used. The use of a lighting device such as device 10, i.e. a light-emitting element without a lens, having such an arrangement has several advantages: first, it can illuminate objects more uniformly and over a larger area. Second, the light emitting element and its wires can be made so small as to be substantially invisible, thus providing an interesting and attractive aesthetic perspective to any object so illuminated.

The conductive lines 14 and 16 are formed on the substrate 12 using standard thin film techniques well known in the art. For example, the wires may be formed in the following order:

a. coating a photoresist material on the substrate 12 with, for example, a spin coater;

b. baking the substrate for a time sufficient to cure the photoresist material (e.g., 30 minutes);

c. placing a negative mask on the photoresist material using an aligner, the mask forming a pattern corresponding to the shape of the conductive lines;

d. exposing the mask to UV light;

e. immersing the substrate in a developer solution for the photoresist material to remove the exposed photoresist material;

f. loading the substrate into a plasma polisher (asher) and cleaning with oxygen;

g. placing a substrate in a vacuum chamber;

h. depositing a metal on the substrate by evaporation with an electrode beam;

i. allowing the substrate to cool and then removing it from the vacuum chamber;

j. the substrate is immersed in an acid to remove the remaining photoresist material.

Preferably, the process is carried out on a large substrate to simultaneously produce a plurality of lighting devices, for example, arranged in a two-dimensional array. After step (j), the final product may be inspected and cut to the desired size and shape.

The wires may be integrally formed on the substrate using the above-described process or other similar processes, and may be made of gold, silver, copper, nickel, and various alloys having a relatively low resistivity. Furthermore, it has been found that instead of using a single metal layer, multiple layers can be used to form the conductive lines. For example, in step (h), three different layers may be deposited, as shown in FIG. 3: a layer of chromium Cr, which bonds well to the glass substrate 12; a layer of nickel, Ni, which is easily weldable; and a layer of gold Au, which has a very small resistance. Finally, a non-conductive resin may be applied on top of the gold layer to protect the wires during handling.

The first layer, or adhesion layer, may also be formed of titanium or a titanium tungsten alloy. The second layer may also be formed with platinum or palladium. The third layer may be formed from silver, copper and other alloys. The second and third layers may be interchanged.

In addition, the conductive lines 14, 16 may be formed of a transparent material or a translucent material such as Indium Tin Oxide (ITO).

Fig. 4 and 5 show a cross-sectional view of watch 30, while indicating how the subject invention may be used. The watch 30 includes a housing 32, a dial 34 having indicia 36. The shaft 38 is used to rotate two hands 40, 42 in a conventional manner. Placed on top of the hands 40, 42 is the substrate 12 with the leads 14, 16 and the light emitting element 22, the light emitting element 22 being oriented downward to illuminate the dial 34 and hands 40, 42.

As can be seen more clearly in fig. 5, the logic provided by IC chip 44 provided under dial 34 is used for movement of hands 40, 42 and/or for light emitting element 22. The chip 44 is connected to the leads 14, 16 by a bond 46.

It should be noted that substrate 12 may be too fragile to properly protect the watch, and therefore, substrate 12 may also be reinforced with an additional protective crystal or other transparent sheet (not shown).

In a further embodiment of the invention, dial 34 may be illuminated from the bottom instead of, or in addition to, being illuminated from the top. In this embodiment, the dial 34 may be made of a transparent or translucent material, and the illumination device 12A is placed beneath the dial 34, substantially similar to the device 12. With this arrangement, the light emitting element (not shown) of device 12A is facing upward, causing its light to pass through dial 34. Advantageously, the device 12A can be made as a separate component or can be integral with the chip 44 or the dial 34.

The subject device shown in fig. 1-3 has been described in terms of an illuminated watch application, however, the device may also be used to illuminate a number of other devices, such as various electronic devices, including cellular telephones, calculators, PDAs, and the like.

The element 22 can emit light at a single wavelength or can be adapted to emit several wavelengths, for example by providing several semiconductor junctions on the same substrate. In the latter configuration, additional leads are required to provide proper actuation of the device.

Fig. 6 illustrates another embodiment of the present invention in which there are multiple light emitting elements, such as elements 22A, 22B, and 22C on substrate 12'. Of course, these elements may be distributed in any desired pattern over the substrate 12' and produce a still or moving image on the substrate. Each element may be connected to a lead C providing excitation to the elements. In this figure, the conductive lines C are drawn to be formed in a radial pattern. However, the conductors may be arranged in any pattern. Furthermore, it is also possible to provide two wires per element, or to share some wires, especially if more than one element is activated at a time.

These elements are activated by connecting the associated wires on these elements to a suitable mechanism and/or electronic switch as is well known in the art.

Light emitting elements in a multi-color arrangement may form groups of red, blue, and green elements, and thus, when appropriately activated, can form a color image with each element.

It will be evident that many other modifications may be made thereto without departing from the scope of the invention as set forth in the following claims.

Claims (19)

1. A semiconductor lighting device comprising:

a substrate;

a plurality of conductive lines disposed on the substrate and having two ends; and

a light emitting element flip-chip packaged, adhered to the substrate and connected to the terminals.

2. The device of claim 1, wherein said substrate is transparent.

3. The device of claim 1, wherein said substrate is opaque.

4. The device of claim 1, wherein the light emitting element is adapted to produce light of a plurality of colors.

5. A semiconductor lighting device comprising:

a substrate;

a plurality of conductive lines disposed on the substrate; and

a plurality of light emitting elements adhered to the substrate and adhered to the wires receiving the excitation signal.

6. The device of claim 5, wherein each of said light emitting elements produces a different color of light.

7. The device of claim 5, wherein the plurality of light emitting elements are encapsulated in a flip chip having a surface of a connection pad, the connection pad being electrically connected to the wire.

8. The apparatus of claim 5, wherein the conductive line comprises a plurality of layers, a first layer formed of a conductive material, and a protective layer.

9. The device of claim 5, wherein each of the conductors comprises a plurality of coextensive layers including a chromium layer, a nickel layer, and a gold layer, the chromium layer being deposited on the substrate.

10. The apparatus of claim 9, further comprising a protective layer for protection formed on top of the other layers.

11. The apparatus of claim 9, wherein said substrate is glass.

12. A method of making a lighting device, the steps comprising:

providing a substrate;

depositing a plurality of wires on the substrate by using a thin film technology;

on the substrate, a light emitting element is mounted so as to be electrically coupled with the wire.

13. The method of claim 12, wherein said substrate is transparent glass.

14. The method of claim 12, wherein said step of depositing said conductive line comprises depositing a layer of Cr on the glass, depositing a layer of Ni on the Cr, and depositing a layer of Au on the Ni.

15. The method of claim 14, further comprising depositing a layer of protective resin on the Au.

16. The method of claim 12 further comprising mounting the light emitting element on a flip chip package having a connection flange on one side surface and connecting said flange to said wire.

17. The method of claim 12 wherein said light emitting elements are lensless so that their light is not concentrated.

18. The method of claim 12, further comprising arranging the light emitting elements in groups of three on said substrate.

19. The method of claim 18, wherein each group includes red, green, and blue elements.