JPS6036114B2 - light emitting diode array - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to alphanumeric display devices, or displays, and more particularly to light emitting diode displays and solid state structures for constructing such displays.

It has been known for a long time that when a forward bias is applied to a pn junction formed in a certain compound semiconductor material, light is generated.

Such semiconductor pn junction diodes are arranged in an array to form an alphanumeric display or indicator. However, conventionally produced such arrays are relatively expensive. The reason for this is that during fabrication, the diode junction structure is placed on a large slice of material, which is then cut or broken into a large number of individual diodes, thereby making each individual diode electrically connected to each other. the diodes are then arranged again in an array or array to give the desired character. In this case, individual wire connections had to be made to at least one electrode of each diode. Additionally, non-uniformities, mismatches, and poor connections in the diode elements resulted in a significant rate of rework or abandonment. This fact, together with the high labor demands of the methods used and the inherently high rate of material waste,
This has made ED displays, or light emitting diode displays, relatively expensive to manufacture. According to the present invention, an LED alphanumeric character display can be manufactured much more cheaply than conventional methods.

According to the invention, small spheres of suitable light-emitting semiconductor material, each having a shallow subsurface pn junction, are produced by bulk processing methods, such as by fluid bed or rotary furnace deposition. These diode spheres are then assembled into arrays in automated equipment for use in displays. For example, the spheres can be quickly and easily positioned in an array configuration using a thin insulating plate or film with a pattern of holes of slightly smaller diameter than the spheres, which are then etched into each side of the plate. The circuit pattern can be used to provide contacts to the diode spheres of the array and to provide interconnections between the diode spheres. Further cost savings are achieved by using a diode sphere with a surface layer of relatively expensive luminescent material grown on a very inexpensive semiconductor material such as silicon or germanium. Accordingly, one object of the present invention is to provide a light emitting diode that can be assembled inexpensively in automated equipment. Still another object of the present invention is to provide a semiconductor element with a special structure that allows it to be manufactured at low cost as a light emitting diode device.

The above-mentioned objects and other objects and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings.

Referring now to FIG. 1, a semiconductor device, designated generally by the reference numeral 10, is shown in cross-section.

The light emitting diode and diode array of the present invention are made from this semiconductor element. Element 1 consists of a core 11 of single crystal semiconductor material, such as silicon or germanium. Small single-crystal starting spheres or pellets of semiconductors are disclosed in U.S. patent application Ser. Manufacturer ring Sora Cell S
emiconductor particles Su
itable farUse jnManufacGr
ingSolar Cells"). The core particle or sphere may be 1'8 or less, depending on the desired dimensions of the finished diode element.
It can have a diameter of 1/2 leg. Additional layers of material can be applied to core 11 by vapor phase or liquid phase epitaxial methods such as those disclosed in the above-mentioned US patents. For example, a layer 12 can be provided which is a bonding layer to achieve mechanical compatibility and expansion matching between the core 11 and other layers. However, layer 12 may also simply be a cardioprotective layer. The layer 12 is, for example, a silicon core 11.
The layer may be approximately 90% silicon mixed with 10% germanium formed above. Of course, many material combinations make layers corresponding to layer 12 unnecessary and can therefore be omitted. A crystallographic compatibility or matching layer 14 is then grown over the spheres.

Such a layer may vary in composition from its inner surface to its outer surface. For example, William W. Gartman (Wil
lianG. U.S. Patent No. 623,283 dated October 17, 1975 (title of the invention;
``Bay/f-Epitaxial Method For Depositing Gallium Arsenide Foss Wide
On Kalemanium and Silicon Substrate Wafer” VaporEpitaxialMet
hod For Depositing Galliu
n ArsenidePhOSphjde.

n Germanl Mountain m And SmC. nS
Much like the planar layer disclosed in StrateWafer, the inner surface of layer 14 is gallium arsenide for crystallographic matching with the germanium core, and the outer surface is 60% gallium arsenide and 40% phosphorous. The composition can be changed to become a gallium oxide material. Finally, a layer 16 of constant composition, which is the same composition as the outer surface of layer 14, is grown on the sphere. Layer 16 also provides n-type conductivity to the gallium arsenide-gallium phosphide.
It contains a small but effective amount of conductivity type determining impurities such as tellurium. A p-n junction is then diffused into the shallow outer surface region 18 of the layer 16 of an impurity to give the gallium arsenide-gallium phosphide a p-conductivity type, such as zinc, to serve as a light emitting diode just below the surface of the sphere. form 19. Alternatively, layer 18 is
It could also be shaped by adding appropriate impurities such as zinc during its formation. The multilayer sphere of FIG. 1 thus forms a special light emitting diode device suitable for use in place of any conventional LED device.

Although single-crystal materials are generally preferred materials because they have high luminous efficiency, it should be understood that the material of the spherical diode element does not have to be a single-crystal material as long as it can function as a light emitter. be. In this connection it should be recognized that the inner core of the diode element can be monocrystalline or polycrystalline germanium or silicon or also solid or hollow glass blocks, ceramic metals or carbon or other suitable materials. It is. In FIG. 1, the diode sphere is not shown to scale for clarity of illustration. For example, spheres having finished dimensions of 0.125 mm and 0.5 mm have been found to be suitable for many uses. In a diode element of this size, the outer diffusion region 1
It would be appropriate for 8 to be about 1 to 5 degrees thick. The overall thickness of layer 16 is suitably between 2 and 10 ridges, and transition layer 12 and layer 14 have a thickness of 5 and 10 ridges.
It would be advantageous to have a joint thickness between the Buddhas. As shown in Figure 2, a diode element is used as a discrete LED.
For use as a device, an enclosure (not shown) can be attached between lead wires 21 and 22.

In such a structure, a portion of the outer region 18 (anode) connects the lead 21 to the layer 1 with solder 24 or the like.
It has been removed by polishing or etching to allow an ohmic connection to the n-type part of 6. It should be noted that such solder or brazing agent may include a material imparting n-type conductivity, such as tellurium, to ensure ohmic contact with the n-type region of layer 16 and prevent unwanted contact with the p-type region 18. It should be included. Lead wire 22 is ohmically connected to outer layer 18, such as by a braze 25 containing p-type impurities. Another method of mounting the LED device of the present invention is shown in FIG.

This method is particularly useful in the construction of multi-element diode arrays and is well suited for automated assembly methods. In the assembly shown in FIG. 3, support member 31 is a circuit board of acetate film or phenolic resin or other material to which thin layers 32 and 33 of copper or other suitable conductive material are applied. It is a relatively thin insulating member. The electrically conductive layer described above may be patterned, such as by etching, or the layer may also be provided in a pattern. For example, these conductive layers can be conductive inks or paints applied by silk-screening. A pattern of holes, as indicated by reference numeral 34, are cut into support member 31 and layers 32, 33 in the desired pattern of the diode array. The diameter of each hex is chosen to be slightly smaller than the diameter of the diode element 10. In this way, it is a simple matter to drop the diode elements into the respective holes of the support 31 to form the diode array in the desired pattern. The relative sizes of the hole and the diode element are chosen such that the diode element projects slightly to the other side of the support 31 when placed in the hole. Once the diode element 10 is secured, the outer p-type layer 18 is electrically connected to the conductive layer 32 by a braze or conductive epoxy adhesive, as indicated by the reference numeral 35. Once the diode element 10 is mounted on the support 31, the outer anode layer 18 is removed from the back-facing portion of the diode element by, for example, plasma etching or other suitable means. .

An electrical connection is then formed between conductor 33 and the cathode portion of layer 16. This connection is indicated by reference numeral 38.
This can be done by means of a conductive strip 36 which can be glued or brazed with conductive epoxy between the two parts. Of course, other suitable means can be used for this connection. 4 and 5 show another embodiment of the invention in the special form of a "seven line" numeric display, which is well suited for automated assembly.

4 and 5, the display substrate 40 is made of plastic, phenolic resin, or other suitable insulating material that can be formed into a relatively thin sheet.

Recesses 41 in the form of inverted pyramids or inverted cones are formed in a pattern on one surface of the substrate 40 . These recesses terminate in small openings 42 in the lower surface of the substrate 40, and these 4-hole openings 42 allow the diode element sphere 10 to form a base as shown in FIG. The size is such that it can protrude slightly downward from the bottom surface of the material 40 to support the diode element spherical body 10. Selected depression 4 is on the top surface of Motomura.
A passage 43 is formed which is connected to one group. As can be seen, each group of depressions corresponds to one of the seven line segments of each character of the indicator or display. The depressions 41 and the passages 43 have a reflective and conductive coating 45 applied on their surfaces. Coating 45 may be plated with silver, copper, or other suitable metal, or alternatively may be plated with silver, nickel, or other suitable material, or a conductive base metal for high reflectivity. The area of hole 42 can be plated with solder, tin, or other low melting point material. In assembly of the display, a single diode element sphere 10 is dropped into each recess 41, and the entire assembly is brazed so that the outer surface 16 of each diode element is brazed to the coating 45 in the recess it occupies. Heat until warm.

Thereafter, the bottom Z side of the assembly is exposed to etching vapor, thereby removing the outer layer 18 of the diode element in the portion of the element exposed through the hole 42. A common connection to all of the exploding diode elements is then formed, for example by a metal plate 51. This metal plate 51
can be connected to each diode element as indicated by reference numeral 52 by a low melting point braze or conductive epoxy adhesive. In operation of this indicator, the recessed coating 45 not only acts as an electrical contact means, but also as a reflector, thereby providing sufficient light for each relatively large character of the indicator. Only 8 small diode elements are sufficient for all the diode elements needed to emit light.

A light emitting diode array using special light emitting diode elements and light emitting diode elements suitable for use as an alphanumeric character display device has been described above.

Although the present invention has been described with reference to the illustrated embodiments, it will be apparent to those skilled in the art that various modifications and changes may be made thereto without departing from the spirit and scope of the invention. .

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the LED diode element of the present invention, FIG. 2 is a cross-sectional view of the diode element of FIG. 1 with electrical contacts attached, and FIG. 3 is a cross-sectional view of the diode element of FIG.
FIG. 4 is a plan view of a seven-line numeric display using the diode element of the present invention, and FIG. 5 is a cross-sectional view illustrating how to attach it to a display member. FIG. FIG. 10...Diode element, 11...'○, 12, 14,
16, 18, 32, 33... layer, 19...
... pn junction, 21, 22... lead wire, 24...
... Solder, 25 ... Brazing agent, 31 ...
... Support member, 34 ... Hole, 36 ... Strip, 40 ... Base material, 41 ... Hollow, 42
...Open □, 43...Aisle, 45...
...Coating, 51...Metal plate. 〃ta'／〃evening, that〃evening, 3 〃ta'evening〃tag'

Claims (1)

[Claims] 1. An insulating support member having two main surfaces and a plurality of holes communicating between the main surfaces, and a plurality of substantially spherical semiconductor diode elements, each of the diode elements each of the diode elements having a subsurface p-n junction and a diameter large enough to prevent passage completely through the hole;
is arranged in each of the holes from the main surface side of the support member, and is further provided adjacent to the first main surface of the support member for providing electrical connection to the diode element on the first region side of the pn junction. and means for providing an electrical connection to the diode elements on the other side of the pn junction, the means being adjacent the other major surface of the support member. 2. The light emitting diode array according to claim 1, wherein the opening of the hole is larger on one of the main surfaces than on the other main surface. 3. The light emitting diode array according to claim 2, wherein the hole has a conical portion. 4. The light emitting diode array according to claim 2, wherein the hole has a pyramidal portion. 5. A light emitting diode array according to any one of claims 2 to 4, characterized in that the walls of the apertures have a reflective coating. 6. A light emitting diode array as claimed in claim 5, wherein the reflective coating is electrically conductive and the reflective coating is electrically conductive and the reflective coating is provided with the reflective coating for providing an electrical connection to the diode element on a first region side of the pn junction. A light emitting diode array, characterized in that it acts as a means. 7. A light emitting diode array as claimed in claim 6, characterized in that the holes are grouped to give characters formed from seven line segments.