# Patent

## Title
Redistribution layer for substrate contacts

## Abstract

A structure with an interconnection layer for redistribution of electrical connections includes a plurality of first electrical connections disposed on a substrate in a first arrangement. An insulating layer is disposed on the substrate over the first electrical connections. A plurality of second electrical connections is disposed on the insulating layer on a side of the insulating layer opposite the plurality of first electrical connections in a second arrangement. Each second electrical connection is electrically connected to a respective first electrical connection. An integrated circuit is disposed on the substrate and is electrically connected to the first electrical connections. The first electrical connections in the first arrangement have a greater spatial density than the second electrical connections in the second arrangement.

## Background
CROSS REFERENCE TO RELATED APPLICATIONS
Reference is made to U.S. Patent Application Ser. No. 62/055,472 filed Sep. 25, 2014, entitled Compound Micro-Assembly Strategies and Devices, and to U.S. patent application Ser. No. 14/743,981 filed Jun. 18, 2015, entitled Micro-Assembled Micro LED Displays and Lighting Elements, the contents of each of which are incorporated by reference herein in their entirety.
FIELD OF THE INVENTION
The present invention relates to electrical interconnections for integrated circuits in multiple layers on a substrate.
BACKGROUND OF THE INVENTION
Flat-panel displays are widely used in conjunction with computing devices, in portable devices, and for entertainment devices such as televisions. Such displays typically employ a plurality of pixels distributed over a display substrate to display images, graphics, or text. For example, liquid crystal displays (LCDs) employ liquid crystals to block or transmit light from a backlight behind the liquid crystals and organic light-emitting diode (OLED) displays rely on passing current through a layer of organic material that glows in response to the electrical current.
Most flat-panel displays use active-matrix thin-film transistors formed in a thin semiconductor layer on a substrate to control an array of light-emitting or light-controlling elements. However, the thin layer of semiconductor material is typically amorphous or has localized crystals, for example in amorphous silicon or polysilicon. These semiconductor material structures have a much lower performance than crystalline semiconductors found in typical integrated circuits. Moreover, it is difficult and expensive to make thin-film semiconductor structures on large substrates, limiting the size of integrated flat-panel devices such as displays. Passive-matrix control structures that do not require a thin-film semiconductor layer are also known but are limited in size resolution, and refresh rate.
At least in part because of these technical challenges, flat-panel displays were originally relatively small, for example having a display substrate diagonal measurement of only a few centimeters. As display substrate processing technology has improved, displays have increased in size, for example displays over three meters in diagonal have been demonstrated.
Large-format outdoor displays typically use inorganic light-emitting diodes (LEDs) individually mounted in a frame. In some displays, groups of LEDs are mounted in tiles and the tiles are assembled into the final display. If an LED in a tile fails, the faulty tile is removed and a good tile replaces the faulty tile. Moreover, tiles can be tested before assembly, increasing display yields. The use of tiles increases the available size of a display since each tile is separately made and is much smaller than the size of the display itself. However, it is in general challenging to provide electrical interconnections to the pixels in the tiles and to maintain a constant pixel pitch across the tile boundaries.
A variety of tiled display structures are known. U.S. Pat. No. 5,563,470 discloses a tiled panel display assembly with a common substrate on which a plurality of small display tiles are mounted in an array and electrically interconnected to form a large-area panel. Each tile includes a plurality of contact pads that are aligned with corresponding contact pads on the substrate. Solder joints between corresponding contact pads mechanically align and secure the tiles on the substrate, and provide electrical connections therebetween. Selected substrate contact pads are electrically interconnected to provide electrical connections between adjacent tiles. Each of the tiles contains a plurality of metal-filled vias that connect contact pads on the under surfaces of the tiles to electrodes on the upper surface of the tile. Alternatively, electrical connections extend around the outer peripheral surface of the tile substrate. U.S. Pat. No. 8,531,642 shows a similar wrap-around electrical connection.
EP1548571 describes a configurable and scalable tiled OLED display. The OLED materials are deposited in a passive-matrix configuration on a transparent substrate and then interconnected with solder bump technology to a printed circuit board located on top of the transparent substrate. U.S. Pat. No. 6,897,855 describes a different tiled OLED structure with display tiles having picture element (pixel) positions defined up to the edge of the tiles. Each pixel position has an organic light-emitting diode (OLED) active area that occupies approximately 25 percent of the pixel area. Each tile includes a memory that stores display data, and pixel-driving circuitry that controls the scanning and illumination of the pixels on the tile. The pixel driving circuitry is located on the back side of the tile and connections to pixel electrodes on the front side of the tile are made by vias which pass through portions of selected ones of the pixel areas that are not occupied by the active pixel material. U.S. Pat. No. 6,897,855 also describes a tiled structure that employs vias through substrates to provide the electrical connections from the driving circuitry to the pixels on the display tiles, as does U.S. Pat. No. 6,853,411. U.S. Pat. No. 6,853,411 also describes locating pixel-driving circuitry beneath an OLED light emitter. Such a structure requires additional layers in a tile structure.
In an alternative arrangement, U.S. Pat. No. 7,394,194 describes a tiled OLED structure with electrical standoffs connecting OLED electrodes on a tile substrate with conductors on a back panel. The electrical standoffs are located on the edge of each tile to avoid compromising the environmental integrity of the OLED materials on the tile.
Inorganic light-emitting diode displays using micro-LEDs (for example having an area less than 100 microns square or having an area small enough that it is not visible to an unaided observer of the display at a designed viewing distance) are also known. For example, U.S. Pat. No. 8,722,458 entitled Optical Systems Fabricated by Printing-Based Assembly teaches transferring light-emitting, light-sensing, or light-collecting semiconductor elements from a wafer substrate to a destination substrate. U.S. Pat. No. 5,739,800 describes an LED display chip with an array of micro-LEDs mounted on a mounting substrate and electrically connected to a driver substrate. However, this arrangement requires multiple substrates and the use of vias to connect integrated circuits on the driver substrate to the LED display substrate and is not suitable for a scalable tiled structure.
Some displays use light-emitting structures on a backplane together with integrated circuits mounted on the backplane to provide control signals to the light-emitting structures. As discussed in U.S. Pat. No. 5,686,790, integrated circuits mounted on the light-emitting side of the backplane unnecessarily increase the size of the backplane while integrated circuits mounted on the side of the backplane opposite the light-emitting structures require electrical vias through the backplane or electrical leads wrapped around the edge of the backplane to electrically connect the integrated circuits with the light-emitting structures. Such vias and leads are difficult and expensive to construct. Integrated circuits located within the display area of a display reduce the resolution and aperture ratio of the display. In flat-panel displays such as LCDs and OLEDs, a reduced aperture ratio also reduces the brightness or lifetime of the display.
Multi-layer printed circuit boards (PCBs) are widely used in digital electronic systems to interconnect electronic elements such as integrated circuits and passive components such as resistors and capacitors. Such printed circuit boards include layers of insulating material interdigitated with patterned conductive layers such as etched copper sheets laminated with electrically conductive through-hole vias to interconnect the electronic elements, for example as disclosed in U.S. Pat. No. 4,591,659. However, these PCBs can be limited in the spatial resolution provided for integrated circuit electrical interconnections. Daughter cards used in conjunction with motherboards (i.e., smaller printed circuit boards mounted upon and electrically connected to larger printed circuit boards) are also known but likewise have limited spatial resolution, orientation, and integration provided for integrated circuits.
There remains a need, therefore, for a display structure that is simple to make and has increased brightness or lifetime in a robust structure amenable to tiling. There is also a need for electrical interconnection structures that provide electrical connections to integrated circuits at a variety of spatial resolutions and in a variety of orientations.
SUMMARY OF THE INVENTION
The present invention provides an interconnection layer structure that is compatible with micro integrated circuits such as those used in micro transfer printing. Micro integrated circuits typically have very small connection pads, for example a few microns square that are not compatible with resolutions supported in conventional printed circuit board processes. Thus, photolithographic methods are used to electrically interconnect micro transfer printed integrated circuits. However, such methods are difficult or expensive to use for large substrates. By providing an interconnection structure that supports both the high resolutions necessary for micro integrated circuits and the low resolutions needed for low-cost, large-format printed circuit boards, micro transfer printed micro integrated circuits can be used over large areas, for example on a backplane. Furthermore, the claimed interconnection structure provides an efficient means of making tiles in a tiled structure, for example a display, which supports both micro integrated circuits with high-resolution connection pads and low-resolution backplane substrates.
In one aspect, the disclosed technology includes a structure with an interconnection layer for redistribution of electrical connections, the structure including: a substrate; a plurality of first electrical connections disposed on the substrate in a first arrangement; an insulating layer disposed on the substrate over the first electrical connections; a plurality of second electrical connections disposed on the insulating layer in a second arrangement and disposed on a side of the insulating layer opposite the plurality of first electrical connections, each second electrical connection of the plurality of second electrical connections electrically connected to a respective first electrical connection; an integrated circuit disposed on the substrate and electrically connected to the first electrical connections, wherein the first electrical connections in the first arrangement are more closely spaced than the second electrical connections in the second arrangement.
In certain embodiments, the first electrical connections are spaced apart by a first spacing and the second electrical connections are spaced apart by a second spacing that is larger than the first spacing.
In certain embodiments, the second electrical connections are spaced apart at least two times farther, at least five times farther, at least ten times farther, at least twenty times farther, at least fifty times farther, at least one hundred times farther, or at least 250 times farther than the first electrical connections are spaced apart.
In certain embodiments, one or more vias are located above a corresponding first electrical connection, one or more vias are located below a corresponding second electrical connection, or both.
In certain embodiments, one or more micro-wires are located on the same side of the insulating layer as the first electrical connections or one or more micro-wires are located on the same side of the insulating layer as the second electrical contacts, or both.
In certain embodiments, the one or more micro-wires located on the same side of the insulating layer as the first electrical connections have a width that is less than the width of the one or more micro-wires located on the same side of the insulating layer as the second electrical contacts.
In certain embodiments, one or more of the first electrical connections have a first area and one or more of the second electrical connections have a second area greater than the first area.
In certain embodiments, the insulating layer is light absorbing, is a black matrix, includes light-absorbing dyes, includes light-absorbing pigments, or is black.
In certain embodiments, the structure includes a plurality of micro-wires; and a plurality of vias in the insulating layer, wherein each second electrical connection of the plurality of second electrical connections is electrically connected to a respective connection of the first electrical connections through a via of the plurality of vias and a micro-wire of the plurality of micro-wires.
In certain embodiments, the micro-wires electrically connect the first electrical connections to the vias.
In certain embodiments, the structure includes wires electrically connecting the vias to the second electrical connections and wherein the wires are wider than the micro-wires.
In certain embodiments, two or more of the first electrical connections are separated by less than 100 microns and the second electrical connections are separated by at least 100 microns.
In certain embodiments, the integrated circuit has external electrical connections having a spacing equal to or less than a spacing of the first electrical connections in the first arrangement.
In certain embodiments, the integrated circuit is an inorganic light emitter or an inorganic light-emitting diode.
In certain embodiments, the integrated circuit comprises a plurality of integrated circuits in a regular arrangement forming a display, each integrated circuit of the plurality of integrated circuit electrically connected to a portion of the first electrical connections.
In certain embodiments, the substrate is a transparent substrate and the first integrated circuits emit light through the transparent substrate.
In certain embodiments, the integrated circuit is a first integrated circuit and the structure comprises a second integrated circuit disposed on the insulating layer and electrically connected to the second electrical connections.
In certain embodiments, the second integrated circuit has external electrical connections spaced apart by a distance equal to or greater than the second electrical connections in the second arrangement are spaced apart.
In certain embodiments, the first integrated circuit electrically communicates with the second integrated circuit.
In certain embodiments, the second integrated circuit electrically controls the first integrated circuit.
In certain embodiments, one or more external electrical connections disposed on the insulating layer in an external arrangement, each of the external electrical connections electrically connected to one or more of the second electrical connections.
In certain embodiments, the external electrical connections are spaced apart by an external spacing that is larger than the second spacing.
In certain embodiments, the insulating layer comprises vias that spatially correspond to electrical connections of the integrated circuit and the electrical connections of the integrated circuit form the first electrical connections.
In certain embodiments, the insulating layer is a first insulating layer and the structure includes: a second insulating layer disposed over the first insulating layer and over the second electrical connections, the second insulating layer having a plurality of vias and a plurality of micro-wires electrically connected to the second electrical connections; and a plurality of third electrical connections disposed on the second insulating layer on a side of the second insulating layer opposite the plurality of second electrical connections in a third arrangement, each of the third electrical connections in the plurality of third electrical connections electrically connected to one of the second electrical connections through the vias and micro-wires of the second insulating layer; wherein the second electrical connections are more closely spaced than the third electrical connections.
In certain embodiments, the substrate is a tile substrate and the structure comprises a backplane substrate and a plurality of tile substrates affixed to the backplane substrate.
In certain embodiments, the structure includes wires directly electrically connecting a first tile substrate of the plurality of tile substrates to a second tile substrate of the plurality of tile substrates.
In certain embodiments, the first integrated circuits are located between the backplane substrate and the tile substrate.
In certain embodiments, the backplane substrate comprises a plurality of backplane electrical connections and the backplane electrical connections are electrically connected to the second electrical connections.
In certain embodiments, the structure includes one or more backplane integrated circuits disposed on the backplane substrate and electrically connected to the first integrated circuits through the second electrical connections.
In certain embodiments, the second electrical connections are directly affixed to and electrically connected to the backplane electrical connections.
In certain embodiments, the second electrical connections are soldered to the backplane electrical connections.
In certain embodiments, the backplane substrate is not rectangular.
In certain embodiments, one of the tile substrates is electrically connected to another tile substrate through the backplane substrate.
In certain embodiments, the plurality of tile substrates comprises first and second tile substrates, each of the first and second tile substrates having an edge and wherein the edge of the first tile substrate is adjacent and substantially parallel to the edge of the second tile substrate.
In certain embodiments, the first and second tile substrates each comprises an edge integrated circuit adjacent to the edge of the tile substrate and an interior integrated circuit that is not adjacent to the edge of the tile substrate and the edge and interior integrated circuits are electrically connected to the first electrical connections and have first integrated circuit connections spaced by a first spacing smaller than a second spacing of the second electrical connections; wherein the distance between the edge integrated circuit of the first tile substrate and the edge integrated circuit of the second tile substrate is substantially equal to the distance between the edge integrated circuit and the interior edge integrated circuit of either the first or second tile substrates.
In certain embodiments, each of the plurality of tile substrates has a plurality of edge and interior integrated circuits and the edge and interior integrated circuits form a regular array.
In certain embodiments, the backplane substrate is a display substrate and the edge and interior integrated circuits are light emitters that form a display.
In certain embodiments, the structure includes a plurality of integrated circuits disposed on the substrate, each electrically connected to a set of first electrical connections that are more closely spaced than a corresponding set of second electrical connections disposed on the insulating layer.
In another aspect, the disclosed technology includes a method of making a display incorporating a structure with an interconnection layer for redistributing electrical connections, the method including: disposing one or more inorganic light emitter(s) on a substrate, the light emitter(s) electrically connected to first electrical connections on the substrate in a first arrangement; disposing an insulating layer on the substrate over the first electrical connections; and disposing a plurality of second electrical connections on the insulating layer in a second arrangement on a side of the insulating layer opposite the plurality of first electrical connections, each second electrical connection of the plurality of second electrical connections electrically connected to a respective connection of the first electrical connections, wherein the first electrical connections in the first arrangement are more closely spaced than the second electrical connections in the second arrangement.
In certain embodiments, the method includes assembling the substrate onto a backplane substrate.
In certain embodiments, the substrate is a tile substrate and the method includes: disposing one or more inorganic light emitter(s) on each tile substrate of a plurality of tile substrates, the light emitter(s) electrically connected to first electrical connections in a first arrangement on the tile substrate; forming an insulating layer disposed on each of the tile substrates over the first electrical connections; forming a plurality of second electrical connections disposed on the insulating layer of each tile substrate in a second arrangement and disposed on a side of the insulating layer opposite the plurality of first electrical connections, each second electrical connection of the plurality of second electrical connections electrically connected to a respective connection of the first electrical connections, wherein the first electrical connections in the first arrangement are more closely spaced than the second electrical connections in the second arrangement; and assembling the tile substrates onto a backplane substrate so that adjacent light emitters are spaced apart by the same distance.
In certain embodiments, locating the one or more inorganic light emitter(s) on the substrate comprises micro transfer printing the one or more inorganic light emitter(s) to the substrate.
In certain embodiments, the method includes disposing a regular array of inorganic light emitters on the substrate, each light emitter in the regular array is electrically connected to first electrical connections in a first arrangement on the corresponding substrate.
In certain embodiments, the substrate is a member selected from the group consisting of polymer, plastic, resin, polyimide, PEN, PET, metal, metal foil, glass, a semiconductor, and sapphire.
In certain embodiments, the backplane substrate is a member selected from the group consisting of polymer, plastic, resin, polyimide, PEN, PET, metal, metal foil, glass, a semiconductor, and sapphire.
An interconnection layer structure provides electrical connections to integrated circuits at a variety of spatial resolutions and in a variety of orientations. The interconnection layer structure supports arrangements of tiles on a backplane substrate, for example in a tiled display.



BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing and other objects, aspects, features, and advantages of the present disclosure will become more apparent and better understood by referring to the following description taken in conjunction with the accompanying drawings, in which:
FIG. 1 is an exploded perspective of an embodiment of the present invention;
FIGS. 2A and 2B are perspectives of partial layers in the embodiment of FIG. 1;
FIG. 3 is a perspective of an alternative layer having second integrated circuits in accordance with an embodiment of the present invention;
FIG. 4 is a perspective of an alternative layer having light-emitting integrated circuits in accordance with an embodiment of the present invention;
FIG. 5 is a perspective of a detail view of light emitters on a substrate in accordance with embodiments of the present invention;
FIGS. 6 and 7 are cross sections of various light emitter structures in accordance with embodiments of the present invention;
FIG. 8 is a perspective of an alternative embodiment of the present invention including a backplane substrate;
FIG. 9 is a cross section of a tiled structure in accordance with an embodiment of the present invention including a backplane substrate inverted with respect to FIG. 8;
FIG. 10 is a plan view of a tiled structure corresponding to FIG. 9 in accordance with an embodiment of the present invention including a backplane substrate; and
FIG. 11 is a flow chart illustrating a method of the present invention.



The features and advantages of the present disclosure will become more apparent from the detailed description set forth below when taken in conjunction with the drawings, in which like reference characters identify corresponding elements throughout. In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The figures are not drawn to scale since the variation in size of various elements in the Figures is too great to permit depiction to scale.
DETAILED DESCRIPTION OF THE INVENTION
Referring to the exploded perspective of FIG. 1 and the partial details of FIGS. 2A and 2B, in an embodiment of the present invention a structure with an interconnection layer 5 for the redistribution of electrical connections includes a substrate 10 having a plurality of first electrical connections 20 disposed on a substrate surface 16 of the substrate 10 in a first arrangement 26. An insulating layer 18 is disposed on the substrate 10 over the first electrical connections 20. In various embodiments, the insulating layer 18 is light absorbing, is a black matrix, includes light-absorbing dyes or pigments, or is black. A plurality of second electrical connections 22 is disposed on the insulating layer 18 in a second arrangement 28 and disposed on a side of the insulating layer 18 opposite the plurality of first electrical connections 20. The second electrical connections 22 can be arranged in an array 23, for example a regular array 23.
The first and second electrical connections 20, 22 can be considered electrical contacts for making electrical connections to electrical conductors in the same layer, in other layers, or on other substrates, and can have a variety of shapes, for example square, rectangular, polygonal, circular, or oval. Each second electrical connection 22 of the plurality of second electrical connections 22 is electrically connected to a respective first electrical connection 20. At least one integrated circuit 30 is disposed on the substrate 10 and is electrically connected to the first electrical connections 20, for example with first and second contacts 37, 39. The first electrical connections 20 in the first arrangement 26 have a greater spatial density (i.e., are more closely spaced) than the second electrical connections 22 in the second arrangement 28.
The first and second arrangements 26, 28 are dispositions or locations of the first and second electrical connections 20, 22 and can be random or structured in a geometric configuration. The second arrangement 28 can be completely different from the first arrangement 26 or can be similar to the first arrangement 26, for example larger than, a reflection of, or a rotation of the first arrangement 26. In an embodiment the integrated circuit 30 is located at least partially beneath the insulating layer 18. In another embodiment, the insulating layer 18 includes vias that spatially correspond to electrical connections of the integrated circuit 30 (e.g., contact pads) and the contact pads form the first electrical connections 20. In another embodiment the insulating layer 18 does not include vias spatially corresponding to the electrical connections of the first integrated circuits 30. In either embodiment, the insulating layer 18 can, but need not, entirely cover the integrated circuits 30.
The first electrical connections 20 are spaced apart by a distance D1 and the second electrical connections 22 are spaced apart by a distance D2 that is larger than the distance D1. Thus, the first electrical connections 20 are spaced apart by a first spacing and the second electrical connections 22 are spaced apart by a second spacing that is larger than the first spacing. The second electrical connections 22 can be spaced apart at least two times farther, at least five times farther, at least ten times farther, at least twenty times farther, at least fifty times farther, at least one hundred times farther, or at least 250 times farther than the first electrical connections 20 are spaced apart. In an embodiment, two or more of the first electrical connections 20 are separated by less than 100 microns and the second electrical connections 22 are separated by at least 100 microns. The integrated circuit 30 can have electrical connections to the integrated circuit 30 (for example connection pads or pins) having a spacing equal to or less than a spacing of the first electrical connections 20 in the first arrangement 26.
According to an embodiment of the present invention, differences in spacing are dependent upon the relative resolution of a photolithographic interconnection process for semiconductors and an interconnection process for printed circuit boards. Thus, the substrate 10 and first electrical connections 20 are compatible with a relatively high-resolution photolithographic process and structure capable of electrically interconnecting micro integrated circuits 30 and the second electrical connections 22 are provided so that the substrate 10 and the micro integrated circuits 30 can be electrically interconnected with a relatively low-resolution printed circuit board process and structure.
As illustrated in the embodiment of FIG. 1 and in FIG. 2A, the first electrical connections 20 are arranged in groups; the first electrical connections 20 in each group are electrically connected to a corresponding integrated circuit 30. (For clarity, an integrated circuit 30 is not shown in the first arrangement 26 of first electrical connections 20 in FIG. 1.) A distance D3 greater than the distance D1 can separate the groups of first electrical connections 20. Similarly, the second electrical connections 22 can, but need not, be arranged in groups; groups of second electrical connections 22 can correspond to groups of first electrical connections 20 but are more spatially spread apart so that they have a lower spatial density. The spatial density of the first arrangement 26 can be the spatial density of all of the first electrical connections 20 taken together in a contiguous area over the substrate 10. Alternatively and as shown in FIGS. 1 and 2A, the spatial density of the first arrangement 26 can be the spatial density of each group of first electrical connections 20 taken together in a contiguous area over the substrate 10. Similarly, the spatial density of the second arrangement 28 can be the spatial density of all of the second electrical connections 22 taken together in a contiguous area over the substrate 10. Alternatively and as shown in FIG. 2B, the spatial density of the first arrangement 26 can be the spatial density of each group of second electrical connections 22 taken together in a contiguous area over the substrate 10.
In a further embodiment of the present invention and as shown in FIG. 2B, one or more vias 19 are located above a corresponding first electrical connection 20. Thus, in an embodiment each first electrical connection 20 can correspond to the contact area exposed by a via 19 on the substrate 10. Alternatively, one or more vias 19 are located below a corresponding second electrical connection 22 (shown in FIG. 4). In general, the vias 19 can be located anywhere in the insulating layer 18 so as to enable an electrical interconnection between the first and second electrical connections 20, 22. Micro-wires 17 can electrically connect the vias 19 to the second electrical connections 22. Micro-wires 17 can also form the first and second contacts 37, 39 or be formed beneath the insulating layer 18 to electrically interconnect the vias 19 to the first electrical connections 20 or electrical connections to the integrated circuit 30 (not shown). Thus, an embodiment of the present invention includes a plurality of micro-wires 17 electrically connecting the second electrical connections 22 to a respective first electrical connection 20 through corresponding vias 19 in the insulating layer 18.
In embodiments, one or more micro-wires 17 are located on the same side of the insulating layer 18 as the first electrical connections 20. Alternatively, or one or more micro-wires 17 are located on the same side of the insulating layer 18 as the second electrical connections 22, or one or more micro-wires 17 are located on the same side of the insulating layer 18 as the first electrical connections 20 and on the same side of the insulating layer 18 as the second electrical connections 22. In a further embodiment, the one or more micro-wires 17 located on the same side of the insulating layer 18 as the first electrical connections 20 have a width that is less than the width of the one or more micro-wires 17 located on the same side of the insulating layer 18 as the second electrical contacts 22. Thus, micro-wires 17 beneath the insulating layer 18 can have a smaller width than the micro-wires 17 above the insulating layer 18. Similarly, one or more of the first electrical connections 20 can have a first area and one or more of the second electrical connections 22 can have a second area greater than the first area.
In a further embodiment, referring to FIG. 3, the integrated circuits 30 are first integrated circuits 30 and the interconnection layer structure 5 of the present invention further includes a second integrated circuit 40 disposed on the insulating layer 18 and electrically connected to the second electrical connections 22. The second integrated circuit 40 can have external electrical connections (e.g., contact pads or pins) spaced apart by a distance equal to or greater than the second electrical connections 22 in the second arrangement 28 are spaced apart. The external electrical connections of the second integrated circuit 40 can be the second electrical connections 22. In various embodiments, the first integrated circuit 30 electrically communicates with the second integrated circuit 40 or the second integrated circuit 40 electrically controls the first integrated circuit 30. For example, the first integrated circuits 30 are light emitters in a pixel 38 controlled by the second integrated circuit 40.
Furthermore, as shown in FIGS. 1 and 3, the interconnection layer structure 5 of the present invention further includes one or more external electrical connections 24 disposed on the insulating layer 18 in an external arrangement 29. Each of the external electrical connections 24 is electrically connected to one or more of the second electrical connections 22. The external electrical connections 24 can be spaced apart by an external spacing having a separation distance D4 that is larger than the second spacing distance D2.
In a further embodiment of the present invention, the insulating layer 18 is a first insulating layer and the interconnection layer structure 5 of the present invention further includes a second insulating layer disposed over the first insulating layer 18 and over the second electrical connections 22. The second insulating layer also includes a plurality of vias 19 and a plurality of micro-wires 17 electrically connected to the second electrical connections 22. A plurality of third electrical connections are disposed on the second insulating layer on a side of the second insulating layer opposite the plurality of second electrical connections 22 in a third arrangement (e.g., similar to the external or backplane arrangements 29 of FIGS. 1, 3, and 8). Each of the third electrical connections in the plurality of third electrical connections is electrically connected to one of the second electrical connections 22 through the vias 19 and micro-wires 17 of the second insulating layer. The second arrangement 28 has areas of greater electrical-connection spatial density than the third arrangement. Elements of this embodiment are illustrated in FIG. 8, described below.
Referring to FIGS. 4 and 5, in an embodiment of the present invention the integrated circuits 30 are inorganic light emitters or inorganic light-emitting diodes (LEDs). A plurality of such integrated circuits 30 can be arranged in a regular arrangement forming a display. The inorganic LEDs can be bottom emitters mounted to emit light through the substrate 10 and the substrate 10 can be transparent to the light emitted by the inorganic LEDs. Different inorganic LEDs that emit different colors of light (e.g., red, green, and blue light emitters 32, 34, 36 that emit red, green, and blue light, respectively) can be included in groups integrated circuits 30 forming pixels 38 that are electrically connected to the first electrical connections 20 with first and second contacts 37, 39. The locations of vias 19 through the insulating layer 18 (not shown in FIG. 4) are indicated with dashed lines.
Referring next to FIG. 6, bottom emitting light emitters 30 can be formed on the substrate 10 by forming a transparent first contact 37 on the substrate 10 and depositing layers of doped or undoped semiconductors 33 on the transparent first contact 37. Dielectric 50 is patterned over the semiconductor 33 leaving a contact area on which the second contact 39 is formed, for example a reflective metal contact that reflects light emitted by the semiconductor 33 through the transparent first contact 37 and transparent substrate 10 when the semiconductor 33 is energized by a current flowing between the first and second contacts 37, 39. Alternatively, as illustrated in FIG. 7, the first contact 37 is not necessarily transparent and is connected to the semiconductor 33 on a side of semiconductor 33 rather than between the semiconductor 30 and substrate 10, as shown. In this embodiment, light emitted by the semiconductor 33 passes only through the transparent substrate 10 and does not pass through the first contact 37. In this case, the first contact 37 can be metal or made of the same material and made in the same steps as the second contact 39.
As shown in FIG. 8, embodiments of the present invention are useful in forming tiled structures such as displays. Referring to FIG. 8, the substrate 10 is a tile substrate 10 and the interconnection layer structure 5 of the present invention further includes a backplane substrate 12 and a plurality of tile substrates 10 affixed to the backplane substrate 12. The first integrated circuits 30 (and any second integrated circuits 40) are therefore located between the backplane substrate 12 and the tile substrates 10. In one embodiment (not shown) wires directly electrically connect a first tile substrate 10A to a second tile substrate 10B. Alternatively, one of the tile substrates 10A is electrically connected to another tile substrate 10B through the backplane substrate 12 (as shown). In such an alternative embodiment, the backplane substrate 12 can include a plurality of backplane electrical connections 27 (for example corresponding to the third electrical connections described above) in a backplane arrangement 29. The backplane electrical connections 27 are electrically connected to the tile electrical connections 24 (for example by a solder connection 25, solder balls are illustrated) and then to the second electrical connections 22 with wires (e.g., micro-wires 17 labeled in FIG. 2B).
The backplane substrate 12 can support one or more backplane integrated circuits 42 disposed on the backplane substrate 12 and electrically connected to the second integrated circuits 40 through the backplane electrical interconnections 27, the tile electrical interconnections 24, and the micro-wires 17. The backplane integrated circuits 42 can also be, but are not necessarily, electrically connected directly to the first integrated circuits 30 through the first and second electrical interconnections 20, 22 rather than through the second integrated circuits 40. The backplane integrated circuits 42 can also be located between the backplane substrate 12 and the tile substrate 10 (and are therefore illustrated with dashed lines indicating a hidden structure).
The backplane electrical interconnections 27 can be affixed and electrically connected directly to the tile electrical connections 24 (as shown) so that the spatial location of the backplane electrical interconnections 27 corresponds to the spatial location of the tile electrical connections 24 (as shown). Alternatively (not shown), the backplane electrical interconnections 27 can be directly affixed and electrically connected to the second electrical connections 22 so that the spatial location of the backplane electrical interconnections 27 corresponds to the spatial location of the second electrical connections 22, for example by soldering the backplane electrical interconnections 27 to the second electrical connections 22 with a solder connection 25.
In an embodiment, the backplane substrate 12 is not rectangular, the tile substrates 10 are not rectangular, or the tile substrates 10 are not arranged in a rectangular array 23. Such non-rectangular arrangements can be used to make structures, such as displays, with alternative form factors, such as triangles, circles, ovals, hexagons, etc.
Referring next to FIG. 9, the first and second tile substrates 10A, 10B are mounted on the backplane substrate 12 and illustrated with the backplane substrate 12 beneath the first and second tile substrates 10A, 10B, rather than above as in FIG. 1. The backplane electrical connections 27 are electrically connected with solder connections 25 to the tile electrical connections 24. Second integrated circuits 40 are located on the insulating layer 18 and are electrically connected to the tile electrical connections 24. Backplane integrated circuits 42 can be included on the backplane substrate 12, as shown. First integrated circuits 30 are mounted on the first and second tile substrates 10A, 10B. The tile substrates 10A, 10B have edges 60. Those integrated circuits 30 closest to the edges 60 are also labeled edge integrated circuits 62. In an embodiment, the distance D3 between the first integrated circuits 30 that are not on the edge 60 is the same as the distance D3 between edge integrated circuits 62 that are on the edges 60 of adjacent first and second tile substrates 10A, 10B so that the distance between the edge integrated circuit 62 of the first tile substrate 10A and the edge integrated circuit 62 of the second tile substrate 10B is substantially equal to the distance between the edge integrated circuit 62 and the interior integrated circuit 64 of either the first or second tile substrates 10A, 10B. The edges 60 of the adjacent first and second tile substrates 10A, 10B can be substantially parallel.
Referring further to the plan view of FIG. 10, an array of tile substrates 10 are affixed to the backplane substrate 12. Each tile substrate 10 includes a three-by-four array 23 of integrated circuits 30. Those integrated circuits 30 adjacent to the edge of the array 23 are labeled edge integrated circuits 62; those integrated circuits 30 interior to the array 23 are labeled as interior integrated circuits 64. An edge integrated circuit 62 adjacent to the edge 60 of the array 23 has no integrated circuit 30 between the edge integrated circuit 62 and the edge 60 of the tile substrate 10. Conversely, an interior integrated circuit 64 that is not adjacent to the edge 60 of the array 23 has at least one integrated circuit 30 between the interior integrated circuit 64 and the edge 60 of the tile substrate 10. The edge and interior integrated circuits 62, 64 are electrically connected to the first electrical connections 20 and have first integrated circuit 30 connections spaced by a first spacing smaller than a second spacing of the second electrical connections 22. Thus, the spacing of the integrated circuit 30 connections or first electrical connections 20 has a higher resolution than that of the second electrical connections 22. In various embodiments, each of the plurality of tile substrates 10 has a plurality of edge and interior integrated circuits 62, 64 and the edge and interior integrated circuits 62, 64 form a regular array 23, as shown in FIG. 10, the backplane substrate 12 is a display substrate, and the edge and interior integrated circuits 62, 64 are light emitters that form a display.
As shown in FIG. 11, a method of making a display incorporating a plurality of tiles each having a structure with an interconnection layer for redistribution of electrical connections includes providing a plurality of tile substrates 10 in step 100, providing light emitters in step 105, and providing a backplane substrate 12 in step 102. The backplane substrate 12 and tile substrates 10 can be glass, plastic, metal, fiber glass, resin, or other materials on which circuits can be patterned and integrated circuits mounted, for example printed circuit board materials of any type. Alternatively, the tile substrates 10 can be a semiconductor, ceramic, or other material suitable for high-resolution photolithographic processes.
A regular array 23 of inorganic light emitters (for example red, green, and blue light emitters 32, 34, 36) are disposed on the tile substrates 10 in an arrangement, for example a regular array 23, having edge and interior light emitters 62, 64 on each of the tile substrates 10 in step 110. The light emitters 30 can be inorganic LEDs formed in native substrates, for example in semiconductor wafers, that are distinct and separate from the non-native tile substrates 10 or non-native backplane substrate 12 and are considered to be integrated circuits 30 herein. The light emitters 30 can be micro transfer printed from a native semiconductor wafer substrate to the tile substrate 10. Additional details useful in understanding and performing aspects of the present invention are described in U.S. patent application Ser. No. 14/743,981 filed Jun. 18, 2015, entitled Micro-Assembled Micro LED Displays and Lighting Elements.
In step 120, each light emitter 30 in the regular array 23 of light emitters 30 is electrically connected to first electrical connections 20 in a first arrangement on the corresponding tile substrate 10. Electrical connections can be made be depositing a conductive layer (such as a layer of metal deposited on the tile substrate 10 by evaporation or sputtering) and patterning the conductive layer (for example by photolithographic methods that etch a patterned photoresist material). The patterned metal conductors can also electrically connect contact pads on the light emitters 30 and can form micro-wires 17, for example as shown in FIGS. 5 and 7. Although FIG. 11 illustrates the light emitters 30 disposed on the tile substrates 10 before the first electrical connections 20 are formed, according to another embodiment, the first electrical connections 20 are formed before the light emitters 30 are disposed on the tile substrates 10. In that case, the light emitters 30 can electrically contact existing first electrical connections 20, for example using a soldered electrical connection. In another embodiment, the micro-wires 17 are formed both before and after the first integrated circuits 30 are disposed on the substrate 10.
An insulating layer 18 is disposed on each of the tile substrates 10 over the first electrical connections 20, and optionally over at least some portion of the light emitters 30, in step 130. Such an insulating layer 18 can be formed by coating a curable liquid, for example a resin or photoresist, and then curing the coated liquid with heat or electromagnetic radiation.
In step 140, vias 19 and micro-wires 17 are formed in or on the insulating layer 18. The vias 19 can be formed as a part of the process used to make the insulating layer 18, for example by using a photoresist to form or coat the insulation layer 18, curing the photoresist by exposure to a pattern of radiation, and developing or etching the photoresist or insulating layer 18 to form the vias 19. Micro-wires 17 can then be formed on the insulating layer 18 and in the vias 19 to electrically connect any micro-wires or first electrical connections 20 through the vias 19.
The second electrical connections 22 can be formed in step 150 on the insulating layer 18 opposite the plurality of first electrical connections 20 using a patterned conductive layer in a second arrangement 28 and methods similar to those used to make the first electrical connections 20. In one embodiment, the micro-wires 17, any connections through the vias 19 to a respective connection of the first electrical connections 20, and the second electrical connections 22 are formed in a common step with common materials, for example using patterned metals, such as aluminum, tantalum, silver, gold, titanium, or other metals or metal composites. In an alternative method, inkjet printing with conductive inks are used to form the micro-wires 17 or second electrical connections 22. Curable conductive inks suitable for inkjetting, for example including silver nano-particles, are commercially available. The first electrical connections 20 in the first arrangement 26 have a greater spatial density than the second electrical connections 22 in the second arrangement 28. Although the terms first and second electrical connections 20, 22 are used herein, they can also be considered to be connection pads or contact pads, for example providing electrical connection areas to the vias 19, first or second integrated circuits 30, 40, or in the case of the second electrical connections 22, a connection area to an off-substrate electrical connector, as is specifically the case for the external electrical connection or tile electrical connection 24.
In a further embodiment in step 160, second integrated circuits 40, for example pixel controllers or light-emitter controllers are disposed on the insulating layer 18 and electrically connected to the micro-wires 17 or second electrical connections 22. As with the first integrated circuits 30, the second integrated circuits 40 can be disposed on the insulating layer 18 either before or after the micro-wires 17 or second electrical connections 22 are formed on the insulating layer 18, or both before and after.
In one embodiment, both the first and second integrated circuits 30, 40 are micro integrated circuits, for example unpackaged integrated circuit dice, located on the insulating layer 18, for example, by micro transfer printing. In another embodiment, the second integrated circuits 40 are packaged integrated circuits located on the insulating layer 18 by more conventional pick-and-place printed circuit board assembly techniques. Thus, in an embodiment, the first integrated circuits 30 are unpackaged integrated circuits and the second integrated circuits 40 are packaged integrated circuits and the electrical connections (contact pads) of the first integrated circuits 30 have a pitch that is much smaller than the electrical connections (contact pads or pins) of the second integrated circuits 40.
The first and second integrated circuits 30, 40 can be made using conventional integrated circuit methods and materials, for example CMOS or bipolar techniques and provided in a wafer (if unpackaged) or packaged on a reel. Techniques for making integrated circuits suitable for micro transfer printing are described in U.S. patent application Ser. No. 14/713,877 entitled Printable Inorganic Semiconductor Structures and in U.S. patent application Ser. No. 14/743,984 entitled Systems and Methods for Preparing GaN and Related Materials for Micro Assembly whose contents are incorporated herein by reference. Assembly strategies for tile substrates 10 (e.g., intermediate substrates) are discussed in U.S. Patent Application Ser. No. 62/055,472 filed Sep. 25, 2014, entitled Compound Micro-Assembly Strategies and Devices.
In an optional step, not shown in FIG. 11, external or tile electrical connections 24 are also formed and electrically connected with micro-wires 17 on the insulating layer 18. These additional tile electrical connections 24 can be made in a common step and with common materials as the second electrical connections 22.
After the backplane substrate 12 is provided in step 102, in step 170 backplane electrical connections 27 are formed on or in the backplane substrate 12 and in step 180 any backplane integrated circuits 42 desired are disposed and interconnected on the backplane substrate 12, for example using printed circuit board manufacturing methods and materials. The backplane integrated circuits 42 can communicate with the first and second integrated circuits 30, 40 as desired. The backplane integrated circuits 42 can be pixel controllers or light-emitter controllers, or not, as desired and as required by the functionality of the second integrated circuits 40, if any.
In step 190, the completed tile substrates 10 (e.g., from step 160) are assembled on the backplane substrate 12. The tile substrates 10 can be removably and replaceably plugged in, for example with connectors, or more permanently affixed, for example by soldering with a solder connection 25 in step 200. The actual location of the tile substrate 10 on the backplane substrate 12 can be precisely controlled using surface tension effects provided by the second electrical connections 22, tile electrical connections 24, and backplane electrical connections with a melted solder joint that hardens in place. This enables accurate pixel placement for display applications using inorganic micro LEDs for the first integrated circuits 30. Thus, the tile substrates 10 can be assembled onto the backplane substrate 12 so that the interior light emitters 64 on each tile substrate 10 are spaced apart by substantially the same distance that separates corresponding edge light emitters 62 on adjacent tile substrates 10.
In operation, power and ground signals are supplied through the backplane substrate 12 and backplane interconnections 27 to the tile substrate 10. Control signals are provided from the backplane integrated circuits 42 to the second integrated circuits 40, if any, and thence to the first integrated circuits 30 (e.g., light emitters 30) by means of the second electrical connections 22, micro-wires 17, vias 19 through the insulating layer 18, first electrical connections 20, and first and second contacts 37, 39. The control signals cause the first integrated circuits 30 to operate, for example to emit light as desired and provide images on the tiled display.
The present invention provides a hierarchical structure for forming displays and other integrated circuit systems. At each level of the hierarchy, the required resolution decreases and the sizes of the integrated circuits can increase. At the first level, the first electrical connections 20 and first integrated circuits 30 can have resolutions and sizes compatible with integrated circuit photolithographic processes, for example in the micron to 100 micron range. At the second level, the second electrical connections 22 and second integrated circuits 40 can have resolutions and sizes compatible with fine printed circuit board processes, for example in the 100 micron to one millimeter range. At the third level, the backplane electrical connections 27 and backplane integrated circuits 42 can have resolutions and sizes compatible with coarse printed circuit board processes, for example equal to or exceeding one millimeter. At each increasing level, the cost of the associated manufacturing materials and methods is reduced. Thus, the present invention provides a high-resolution method for tiled structures having reduced cost, replaceable components, and high resolution.
As is understood by those skilled in the art, the terms “over” and “under” are relative terms and can be interchanged in reference to different orientations of the layers, elements, and substrates included in the present invention. For example, a first layer on a second layer, in some implementations means a first layer directly on and in contact with a second layer. In other implementations a first layer on a second layer includes a first layer and a second layer with another layer there between.
Having described certain implementations of embodiments, it will now become apparent to one of skill in the art that other implementations incorporating the concepts of the disclosure may be used. Therefore, the invention should not be limited to the described embodiment, but rather should be limited only by the spirit and scope of the following claims.
Throughout the description, where apparatus and systems are described as having, including, or comprising specific components, or where processes and methods are described as having, including, or comprising specific steps, it is contemplated that, additionally, there are apparatus, and systems of the disclosed technology that consist essentially of, or consist of, the recited components, and that there are processes and methods according to the disclosed technology that consist essentially of, or consist of, the recited processing steps.
It should be understood that the order of steps or order for performing certain action is immaterial so long as the disclosed technology remains operable. Moreover, two or more steps or actions in some circumstances can be conducted simultaneously. The invention has been described in detail with particular reference to certain embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.
PARTS LIST


    D1 distance
    D2 distance
    D3 distance
    D4 distance
    5 interconnection layer structure
    10 substrate/the substrate
    10A first tile substrate
    10B second tile substrate
    12 backplane substrate
    16 substrate surface
    17 micro-wires
    18 insulating layer/first insulating layer
    19 vias
    20 first electrical connection
    22 second electrical connection
    23 array
    24 external electrical connection/the electrical connection
    25 solder connection
    26 first arrangement
    27 backplane electrical interconnection
    28 second arrangement
    29 external arrangement/backplane arrangement
    30 integrated circuit/first integrated circuit/light emitter
    32 red light emitter
    33 semiconductor
    34 green light emitter
    36 blue light emitter
    37 first contact
    38 pixel
    39 second contact
    40 second integrated circuit/pixel controller
    42 backplane integrated circuit
    50 dielectric
    60 edge
    62 edge integrated circuit/edge light emitter
    64 interior integrated circuit/interior light emitter
    100 provide tile substrate step
    102 provide backplane substrate step
    105 provide light emitters step
    110 dispose light emitters on tile substrates step
    120 form first electrical connections on tile substrate step
    130 form insulating layer on tile substrates step
    140 form vias and micro-wires on tile substrates step
    150 form second electrical connections on tile substrates step
    160 locate pixel controllers on second electrical connections step
    170 form backplane electrical connections on backplane step
    180 locate display controllers on backplane electrical connections step
    190 assemble tile substrates on backplane substrate step
    200 electrically connect tile substrates to backplane substrate step

## Claims

1. A structure with an interconnection layer for redistribution of electrical connections, comprising:
a substrate having a side;
a plurality of first electrical connections disposed on the side of the substrate in a first arrangement, each of the first electrical connections having a first size;
a single insulating layer comprising a cured material coated on the side of the substrate over the first electrical connections;
a plurality of second electrical connections disposed on the insulating layer in a second arrangement and disposed on a side of the insulating layer opposite the plurality of first electrical connections, each of the second electrical connections having a second size, wherein the second sizes are greater than the first sizes, each second electrical connection of the plurality of second electrical connections electrically connected to a respective first electrical connection through a via having a size corresponding to the first size of the respective first electrical connection and smaller than the second sizes of the plurality of second electrical connections;
a plurality of integrated circuits disposed on the side of the substrate, each electrically connected to a set of the first electrical connections that are more closely spaced within the set on the substrate side than within a corresponding set of the second electrical connections on the insulating layer.

2. The structure of claim 1, wherein one or more vias are located above a corresponding first electrical connection, one or more vias are located below a corresponding second electrical connection, or one or more vias are located above a corresponding first electrical connection and one or more vias are located below a corresponding second electrical connection.

3. The structure of claim 1, wherein one or more micro-wires are located on the same side of the insulating layer as the first electrical connections or one or more micro-wires are located on the same side of the insulating layer as the second electrical contacts, or both.

4. The structure of claim 1, wherein one or more first micro-wires are located on the same side of the insulating layer as the first electrical connections and one or more second micro-wires are located on the same side of the insulating layer as the second electrical contacts and wherein the first micro-wires have a width that is less than the width of the second micro-wires.

5. The structure of claim 1, wherein one or more of the first electrical connections have a first area and one or more of the second electrical connections have a second area greater than the first area.

6. The structure of claim 1, wherein the insulating layer is a black matrix, includes light-absorbing dyes, includes light-absorbing pigments, or is black when exposed to visible light.

7. The structure of claim 1, comprising:
a plurality of micro-wires; and
a plurality of vias in the insulating layer, wherein each second electrical connection of the plurality of second electrical connections is electrically connected to a respective connection of the first electrical connections through a via of the plurality of vias and a micro-wire of the plurality of micro-wires.

8. The structure of claim 7, wherein the micro-wires electrically connect the first electrical connections to the vias.

9. The structure of claim 8, comprising wires electrically connecting the vias to the second electrical connections and wherein the wires are wider than the micro-wires.

10. The structure of claim 1, wherein two or more of the first electrical connections are separated by less than 100 microns and the second electrical connections are separated by at least 100 microns.

11. The structure of claim 1, wherein one of the plurality of integrated circuits has external electrical connections having a spacing equal to or less than a spacing of the first electrical connections in the first arrangement.

12. The structure of claim 1, wherein one of the plurality of integrated circuits is an inorganic light emitter or an inorganic light-emitting diode.

13. The structure of claim 1, wherein the plurality of integrated circuits are in a regular arrangement forming a display.

14. The structure of claim 1, wherein the plurality of integrated circuits comprises a first integrated circuit and a second integrated circuit, wherein the first integrated circuit has external electrical connections spaced apart by a first distance, and the second integrated circuit has external electrical connections spaced apart by a second distance equal to or greater than the first distance.

15. The structure of claim 1, wherein the plurality of integrated circuits comprises a first integrated circuit and the structure comprises a second integrated circuit disposed on the insulating layer and electrically connected to at least one of the second electrical connections and wherein the first integrated circuit electrically communicates with the second integrated circuit.

16. The structure of claim 1, wherein the plurality of integrated circuits comprises a first integrated circuit and the structure comprises a second integrated circuit disposed on the insulating layer and electrically connected to at least one of the second electrical connections and wherein the second integrated circuit electrically controls the first integrated circuit.

17. The structure of claim 1, wherein the substrate is a tile substrate and the structure comprises a backplane substrate and a plurality of tile substrates affixed to the backplane substrate.

18. The structure of claim 17, wherein the plurality of integrated circuits are located between the backplane substrate and the tile substrate.