Random partitionable dot matrix LED display

(1) Field of the Invention

This invention relates to light emitting diodes (LED), in particular to LED displays.

(2) Brief Description of Related Art

FIG. 1 shows a prior art 8×8 LED display panel. The two electrodes of each LED is coupled to a pair of soldering pads which are mounted on a substrate 01 . Each soldering pad is connected by printed wiring 05 to plated-through holes 04 for connection to the bottom side of the substrate 01 . Such printed wiring 05 have irregular pattern printed on the substrate 01 .

FIG. 2 shows the bottom side of the substrate 01 , again showing the irregularity of the wiring pattern.

The irregularity of the layout does not allow for design flexibility. When the dimension of the display panel is changed, a new layout must be patterned. The mating between the LED display panel and the motherboard does not follow any regular rule, and makes it more difficult to test. If any one of the LEDs is defective, the whole display panel must be discarded.

An object of this invention is to provide a LED display panel, which is partitionable and configurable to different number of pixels. Another object of this invention is to disable any defective LED in a display panel. Still another object of this invention is to provide a LED display panel, which can easily be tested.

These objects are achieved by arranging the LEDs of a display as a matrix array. The metal interconnections for accessing the LEDs of the matrix array are laid out as vertical columns and horizontal rows as in a two-dimensional random access memory array. These matrix array can be cut and partitioned to reduce the number of pixels of the display panel, or be expanded to increase the number of pixels. The partitioned sub-arrays can be pieced together by aligning the corresponding interconnections and connecting them through a motherboard. Any defective LED in the array can be inactivated by not accessing the particular defective LED. The LEDs can be mounted on plated-through holes to reach the opposite side of the substrate for surface mounting to a motherboard.

FIG. 1 shows an irregular wiring pattern of a prior art LED display panel.

FIG. 2 shows the irregular wiring pattern at the bottom side of the prior art LED shown in FIG. 1 .

FIG. 3 shows the basic layout of the configurable LED matrix array display panel based on the present invention.

FIG. 4 shows the mounting of the LEDs on the soldering pads laid out according to FIG. 3 .

FIG. 5 shows the perspective view of the bottom side of the LED display panel shown in FIG. 3 .

FIG. 6 shows the layout of a reduced-size LED sub-matrix array.

FIG. 7 shows the layer out of a LED sub-matrix array further reduced than FIG. 6 .

FIG. 8 shows a single LED pixel.

FIG. 9 shows plated-through soldering pads for mounting the LEDs.

FIG. 10 shows mounting pads for LEDs with only bottom electrodes.

FIG. 3 shows the basic layout of the LED matrix array. As an example, an 8×4 LED matrix is shown. An LED is placed near each cross-point of rows of interconnections X 1 , X 2 , . . . X 8 , and columns of interconnections Y 1 , Y 2 , . . . Y 4 . Each LED is mounted on one or two soldering pads at the cross-point of the orthogonal interconnections. A common metal interconnections X 1 , X 2 , X 8 is connected to each right hand soldering pad on the same row. Similarly, a common metal interconnections Y 1 , Y 2 , . . . Y 4 is connected to left hand soldering pad on the same column. The X-interconnections and the Y-interconnections are insulated from each other. A particular LED is activated by coincident addressing. For, instance, the LED ( 11 ) is activated when row X 1 and column Y 1 are energized coincidentally; the LED ( 22 ) is activated when row X 2 and column Y 2 are activated coincidentally; the LED ( 84 ) is activated when row X 8 and column Y 4 are activated coincidentally; etc.

FIG. 4 shows how the horizontal interconnections X 1 , X 2 , . . . X 8 are insulated from the vertical interconnections Y 1 , Y 2 , . . . Y 4 . As shown, the vertical lines Y 1 , Y 2 , . . . Y 4 are printed on the bottom of the substrate shown as dotted lines. An LED 203 is mounted on the left hand soldering pad 201 , which is plated through the substrate to contact the wiring at the bottom side and be connected to the common vertical interconnection Y 4 . The top electrode of the LED 203 is wire bonded to the right bonding pad 202 , which is connected to a common horizontal interconnection X 1 . Thus, each LED at a cross-point can be activated at random. If the LED has two bottom electrodes, both bottom electrodes can rest over the two soldering pads as a flip-chip.

FIG. 5 shows the perspective view of the bottom side of the substrate shown in FIG. 4 . The LEDs ( 11 ), ( 22 ) and ( 84 ) can be activated as explained in connection with FIG. 3 . Such a regular layout pattern is amendable to partitioning. When such an array is cut for partitioning, more than one partitioned blocks can be pieced together to form a larger display panel. By aligning the corresponding interconnections either horizontally or vertically, the continuity of the interconnections can be preserve. During application, different horizontal interconnections or vertical interconnections of the partitioned blocks can be extended by coupling through an underlying motherboard, thus increasing the design flexibility.

FIG. 6 shows how the 8×4 LED matrix array shown in FIG. 4 is reduced to a 5×3 LED matrix array by cutting off three horizontal rows X 6 , X 7 and X 8 and vertical columns Y 4 . The layout of the remaining LED matrix array is the same as the 8×4 LED matrix. Therefore, there is no need to redesign the layout. The LEDs ( 11 ), ( 22 ) and ( 53 ) can be energized by coincident addressing as explained in connection with FIG. 3 .

FIG. 7 shows a further reduction of the LED matrix array to a 4×2 matrix array with only four horizontal rows X 1 , X 2 , X 3 , X 4 and two columns Y 1 , Y 2 . As in FIGS. 3 and 6, the LEDs ( 11 ), ( 22 ) and ( 42 ) can be energized by coincident addressing.

FIG. 8 shows a further reduction of the LED matrix to a single LED pixel. The LED ( 22 ) is energized by the coincident addressing of row X 2 and column Y 2 . Conversely, if the LED ( 22 ) is found to be defective, this LED can be deactivated by disabling the address X 2 , Y 2 . Also, if one of the LEDs is defective, the display panel can be cut to a smaller sub-display panel.

FIG. 9 shows the bonding pads for insertion-type LEDs with two bottom electrodes. The LED ( 22 ) has one bottom electrode inserted in the left soldering pad with a plated-through via hole for connection to a vertical interconnection Y 2 as described in FIG. 4 . The second bottom electrode of the LED is inserted in the right-hand soldering pad, which is connected to the common horizontal interconnection X 2 .

FIG. 10 shows another LED matrix panel which is cut to a non-rectangular display. As shown, row X 1 has three LEDs such as ( 11 ), row X 2 has two LEDs such as ( 22 ), and row X 3 has only one LED. As before, the panel can be cut from the original 8×4 matrix array. Yet, the horizontal interconnections and/or vertical interconnections can be extended, because of the regularity of the layout patterns.

While the preferred embodiments of the invention have been described, it will be apparent to those skilled in the art that various modifications may be made in the embodiments without departing from the spirit of the present invention. Such modifications are all within the scope of this invention.