Micro lighting device

A micro lighting device includes a source line, a ground line, a main LED, and a redundant LED. The main LED includes a first electrode and a second electrode, and the redundant LED includes a third electrode and a fourth electrode. When the main LED is able to light up, the first electrode is electrically connected to the source line, the second electrode is electrically connected to the ground line, and at least one of the third electrode and the fourth electrode is electrically isolated from both the source line and the ground line. When the main LED is unable to light up, at least one of the first electrode and the second electrode is electrically isolated from both the source line and the ground line, the third electrode is electrically connected to the source line, and the fourth electrode is electrically connected to the ground line.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority of Taiwan Application No. 106142619 filed on 2017 Dec. 5.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is related to a micro lighting device, and more particularly, to a micro lighting device with repair mechanism.

2. Description of the Prior Art

Compared to traditional incandescent bulbs, light-emitting diodes (LEDs) are advantageous in low power consumption, long lifetime, small size, no warm-up time, fast reaction speed, and the ability to be manufactured as small or array devices. In addition to outdoor displays, traffic signs, and liquid crystal display (LCD) backlight for various electronic devices such as mobile phones, notebook computers or personal digital assistants (PDAs), LEDs are also widely used as indoor/outdoor lighting devices in place of fluorescent of incandescent lamps.

The size of traditional LED arrays is the dimension of millimeters (mm). The size of micro LED arrays may be reduced to the dimension of micrometers (μm) while inheriting the same good performances regarding power consumption, brightness, resolution, color saturation, reaction speed, life time and efficiency. In a micro LED manufacturing process, a thin-film, miniaturized and array design is adopted so that multiple micro LEDs are fabricated in the dimension of merely 1-10 μm. Next, these micro LEDs are mass transferred to be disposed on another circuit board. Protection layers and upper electrodes may be formed in a physical deposition process before packaging the upper substrate. Since the manufacturing process of micro LEDs is very complicated, there is a need to improve manufacturing yield.

SUMMARY OF THE INVENTION

The present invention provides a micro lighting device including a source line, a ground line, a main luminescent device having a first electrode and a second electrode, and a redundant luminescent device having a third electrode and a fourth electrode. The first electrode is electrically connected to the source line and the second electrode is electrically connected to the ground line and at least one of the third electrode and the fourth electrode is electrically isolated from both the source line and the ground line when the main luminescent device is able to light up. At least one of the first electrode and the second electrode is electrically isolated from both the source line and the ground line, the third electrode is electrically connected to the source line and the fourth electrode is electrically connected to the ground line when the main luminescent device is unable to light up.

The present invention further provides a micro lighting device including a source line, a ground line, a main luminescent device having a first electrode and a second electrode, a redundant luminescent device having a third electrode and a fourth electrode, and a conductive material. The first electrode is electrically connected to the source line and the second electrode is electrically connected to the ground line when the main luminescent device is able to light up. Both the first electrode and the second electrode are electrically isolated from both the source line and the ground line when the main luminescent device is unable to light up. The redundant luminescent device is arranged to be disposed on the main luminescent device when the main luminescent device is unable to light up and the conductive material is used for electrically connecting the third electrode to the source line and for electrically connecting the fourth electrode to the ground line.

The present invention further provides a method of manufacturing and repairing micro lighting device. The method includes fabricating a main luminescent device which includes a first electrode and a second electrode and then transferring the main luminescent device to be disposed on a substrate, fabricating a redundant luminescent device which includes a third electrode and a fourth electrode and then transferring the redundant luminescent device to be disposed on the substrate, electrically connecting the first electrode to a source line, electrically connecting the second electrode to a ground line, and electrically isolating at least one of the third electrode and the fourth electrode from both the source line and the ground line when the main luminescent device is able to light up, and electrically isolating at least one of the first electrode and the second electrode from both the source line and the ground line, electrically connecting the third electrode to the source line, and electrically connecting the fourth electrode to the ground line when the main luminescent device is unable to light up.

The present invention further provides a method of manufacturing and repairing micro lighting device. The method includes fabricating a main luminescent device which includes a first electrode and a second electrode, fabricating a redundant luminescent device which includes a third electrode and a fourth electrode, transferring the main luminescent device to be disposed on a substrate, electrically connecting the first electrode to a source line and electrically connecting the second electrode to a ground line when the main luminescent device is able to light up, electrically isolating at least one of the first electrode and the second electrode from both the source line and the ground line when the main luminescent device is able to light up, disposing the redundant luminescent device on the main luminescent device, and disposing a conductive material for electrically connecting the third electrode to the source line and for electrically connecting the fourth electrode to the ground line.

DETAILED DESCRIPTION

FIG. 1Ais a structural diagram illustrating a micro lighting device100according to an embodiment of the present invention. A cross-sectional diagram of the micro lighting device100is depicted on the left side ofFIG. 1A, and a top-view diagram of the micro lighting device100is depicted on the right side ofFIG. 1A. The micro lighting device100with a thin-film, miniaturized and array design includes a plurality of main luminescent devices (only one main luminescent device10is depicted for illustrative purpose), at least one redundant luminescent device20, a source line30, and a ground line40.

The main luminescent device10and the redundant luminescent device20are fabricated by combining P-type and N-type semiconductor materials before being mass transferred to a substrate50. Under normal condition, when a positive voltage is applied to a P-electrode and a negative voltage is applied to an N-electrode, electrons flow from the N-region towards the P-region and holes flow from the P-region towards the N-region due to the forward-bias voltage. These electrons and holes then combine in the PN junction of the luminescent layer, thereby emitting photons of light. In an embodiment of the present invention, the main luminescent device10and the redundant luminescent device20may be micro LED devices. The main luminescent device10includes a P-type semiconductor layer12, an N-type semiconductor layer14, a P-electrode16, an n-electrode18, and a luminescent layer15, wherein the P-electrode16is electrically connected to the source line30and the N-electrode18is electrically connected to the ground line40. The redundant luminescent device20includes a P-type semiconductor layer22, an N-type semiconductor layer24, a P-electrode26, an n-electrode28, and a luminescent layer25, wherein the P-electrode26is electrically connected to the source line30but the N-electrode18is electrically isolated from the ground line40.

FIG. 1Bis a diagram illustrating a method of repairing the micro lighting device100according to an embodiment of the present invention. A cross-sectional diagram of the repaired micro lighting device100is depicted on the left side ofFIG. 1B, and a top-view diagram of the repaired micro lighting device100is depicted on the right side ofFIG. 1B, wherein the repair locations are designated by flash signs. For illustrative purpose, it is assumed that the main luminescent device10inFIG. 1Asomehow malfunctions and is unable to light up when applying voltages to the P-electrode16and the N-electrode18, while the normal redundant luminescent device20is unable to light up because no voltage can be applied to the N-electrode28. As depicted inFIG. 1B, the electrical connection between the P-electrode16of the main luminescent device10and the source line30may be cut off using laser cutting technique so as to prevent leakage current from the flawed main luminescent device10. Next, the electrical connection between the N-electrode28of the redundant luminescent device20and the ground line40may be established using laser repair technique so that the normal redundant luminescent device20may light up to replace the flawed main luminescent device10.

FIG. 2Ais a structural diagram illustrating a micro lighting device200according to another embodiment of the present invention. A cross-sectional diagram of the micro lighting device200is depicted on the left side ofFIG. 2A, and a top-view diagram of the micro lighting device200is depicted on the right side ofFIG. 2A. The micro lighting device200with a thin-film, miniaturized and array design includes a plurality of main luminescent devices (only one main luminescent device10is depicted for illustrative purpose), at least one redundant luminescent device20, a source line30, and a ground line40.

The main luminescent device10and the redundant luminescent device20are fabricated by combining P-type and N-type semiconductor materials before being mass transferred to a substrate50. Under normal condition, when a positive voltage is applied to a P-electrode and a negative voltage is applied to an N-electrode, electrons flow from the N-region towards the P-region and holes flow from the P-region towards the N-region due to the forward-bias voltage. These electrons and holes then combine in the PN junction of the luminescent layer, thereby emitting photons of light. In an embodiment of the present invention, the main luminescent device10and the redundant luminescent device20may be micro LED devices. The main luminescent device10includes a P-type semiconductor layer12, an N-type semiconductor layer14, a P-electrode16, an n-electrode18, and a luminescent layer15, wherein the P-electrode16is electrically connected to the source line30and the N-electrode18is electrically connected to the ground line40. The redundant luminescent device20includes a P-type semiconductor layer22, an N-type semiconductor layer24, a P-electrode26, an n-electrode28, and a luminescent layer25, wherein the N-electrode18is electrically connected to the ground line40but the P-electrode26is electrically isolated from the source line30.

FIG. 2Bis a diagram illustrating a method of repairing the micro lighting device200according to an embodiment of the present invention. A cross-sectional diagram of the repaired micro lighting device200is depicted on the left side ofFIG. 2B, and a top-view diagram of the repaired micro lighting device200is depicted on the right side ofFIG. 2B, wherein the repair locations are designated by flash signs. For illustrative purpose, it is assumed that the main luminescent device10inFIG. 2Asomehow malfunctions and is unable to light up when applying voltages to the P-electrode16and the N-electrode18, while the normal redundant luminescent device20is unable to light up because no voltage can be applied to the P-electrode26. As depicted inFIG. 2B, the electrical connection between the N-electrode18of the main luminescent device10and the ground line40may be cut off using laser cutting technique so as to prevent leakage current from the flawed main luminescent device10. Next, the electrical connection between the P-electrode26of the redundant luminescent device20and the source line30may be established using laser repair technique so that the normal redundant luminescent device20may light up to replace the flawed main luminescent device10.

FIG. 3Ais a structural diagram illustrating a micro lighting device300according to another embodiment of the present invention. A cross-sectional diagram of the micro lighting device300is depicted on the left side ofFIG. 3A, and a top-view diagram of the micro lighting device300is depicted on the right side ofFIG. 3A. The micro lighting device300with a thin-film, miniaturized and array design includes a plurality of main luminescent devices (only two main luminescent devices11and12are depicted for illustrative purpose), a source line30, and a ground line40.

The main luminescent devices11and12are fabricated by combining P-type and N-type semiconductor materials before being mass transferred to a substrate50. Under normal condition, when a positive voltage is applied to a P-electrode and a negative voltage is applied to an N-electrode, electrons flow from the N-region towards the P-region and holes flow from the P-region towards the N-region due to the forward-bias voltage. These electrons and holes then combine in the PN junction of the luminescent layer, thereby emitting photons of light. In an embodiment of the present invention, the main luminescent devices11and12may be micro LED devices each including a P-type semiconductor layer12, an N-type semiconductor layer14, a P-electrode16, an n-electrode18, and a luminescent layer15, wherein the P-electrode16is electrically connected to the source line30and the N-electrode18is electrically connected to the ground line40.

FIGS. 3B-3Dare diagrams illustrating a method of repairing the micro lighting device300according to an embodiment of the present invention. A cross-sectional diagram of the repaired micro lighting device300is depicted on the left side ofFIGS. 3B-3D, and a top-view diagram of the repaired micro lighting device300is depicted on the right side ofFIGS. 3B-3D, wherein the repair locations are designated by flash signs. For illustrative purpose, it is assumed that the main luminescent device11inFIG. 3Asomehow malfunctions and is unable to light up when applying voltages to its P-electrode16and its N-electrode18, while the normal main luminescent device12is able to light up when applying voltages to its P-electrode16and its N-electrode18. As depicted inFIG. 3B, the electrical connection between the P-electrode16of the main luminescent device11and the source line30and the electrical connection between the N-electrode18of the main luminescent device11and the ground line40may be cut off using laser cutting technique so as to prevent leakage current from the flawed main luminescent device11. Next as depicted inFIG. 3C, a redundant luminescent device20may be fabricated by combining P-type and N-type semiconductor materials before being transferred to be displaced on the main luminescent device11. The redundant luminescent device20includes a P-type semiconductor layer22, an N-type semiconductor layer24, a P-electrode26, an n-electrode28, and a luminescent layer25. Next as depicted inFIG. 3D, conductive material35may be deposited on the redundant luminescent device20so that the P-electrode26and the n-electrode28may be electrically connected to the source line30and the ground line40, respectively. Therefore, the normal redundant luminescent device20may light up to replace the flawed main luminescent device11.

In an embodiment of the present invention, the conductive material35may be tantalum, molybdenum or tungsten metal which may be welded to the electrodes of the redundant luminescent device20in a laser metal transfer (LMT) process. In another embodiment of the present invention, the conductive material35may be Ni(CO)4, Fe(CO)5, Cr(CO)6, Mo(CO)6, or W(CO)6 metal compounds which may be deposited on the electrodes of the redundant luminescent device20in a laser chemical vapor deposition (LCVD) process. However, the type of the conductive material35does not limit the scope of the present invention.

In conclusion, the present invention provides a micro lighting device with repair mechanism. In addition to good performances regarding power consumption, brightness, resolution, color saturation, reaction speed, life time and efficiency, the present micro lighting device can also improve manufacturing yield using the repair mechanism.