TWI664710B - System and method for the fluidic assembly of emissive displays - Google Patents

Abstract

A fluid assembly method for manufacturing a light emitting display is provided. A light emitting substrate having a top surface is provided, in which a plurality of wells are formed. Each well has a bottom surface with a first electrical interface. A liquid suspension of the light-emitting element is also provided. The suspension flows through the light emitting substrate and the light emitting element is captured in the well. The light-emitting substrate is annealed such that an electrical connection is formed between each light-emitting element and the first electrical interface of its corresponding well. It is desirable to use a eutectic solder interface metal on the substrate or the light emitting element and to use a flux before thermal annealing. The light emitting element may be a surface mount light emitting diode (SMLED) having two electrical contact portions on its top surface (near the bottom surface of the well).

Description

System and method for fluid assembly of light emitting display

The present invention relates generally to integrated circuits (ICs), and more particularly to a fluid assembly method for manufacturing a light emitting display.

The fluid transfer of micro-machined electronic devices, optoelectronic devices, and sub-systems from mother substrates / wafers to large-area and / or unconventional substrates provides new opportunities for expanding the scope of applications of electronic and optoelectronic devices. For example, light-emitting diode (LED) microstructures, such as rods, sheets, or disks, that display the element size can be manufactured on a small-sized wafer and then transferred to a large panel glass substrate to achieve a direct light-emitting display. A traditional method of transferring such LED microstructures is through a pick-and-place process. However, for a display containing millions of elements, such a process may take several hours to complete and is therefore inefficient.

Electronic devices, such as LEDs and concentrating solar cells, are often self-assembled by minimizing the surface energy at the molten solder capillary interface, so that the mechanical and electrical connections to the electrodes can be achieved simultaneously during assembly, such as As described in U.S. Patent No. 7,774,929. In one aspect, the electronic device is captured in a shape-matched well structure, followed by an electrical integration process, as described in US Patent No. 6,316,278.

Some problems to be solved in the conventional fluid assembly process, with large-scale distribution methods, integration of micro-components into drive circuits over a large area, and repair of defective micro-components Related to the underlying structure. On a large scale, conventional fluid assembly into a well is challenged by the dual requirements of maximum speed for micro-element capture and minimum distribution speed for high-speed array assembly. Similarly, the micro-component distribution scheme and flow rate uniformity required to achieve high yields on monolithic assembly substrates that exceed the centimeter level have become very challenging.

The integration of the assembled micro-elements is mainly achieved by electrode deposition formed by photo-etching of the micro-elements, or a second electrical contact portion is laminated near the first electrode contact portion as part of the assembly scheme. However, due to contamination of any remaining micro-elements on the surface of the substrate, photolithography of the large substrate after fluid assembly may be suppressed. The top contact of the stack has not been proven to be sufficiently reliable to be electrically connected to the micro-devices used for display applications.

Finally, defect detection of electrically excited micro-components is the most reliable and effective method for pre-repair inspections. The assembled micro-element with the top contact electrode is held at least partially in an insulating matrix. Any repair involving the removal of defective micro-assemblies from this matrix is very difficult. In addition, any similar integrated micro-elements added to the array to compensate for defective micro-elements require repeated electrode contact processes. Although technical solutions may exist, they are expected to be more expensive, time consuming, and less reliable.

It would be advantageous if a fluid assembly process could be used to efficiently transfer light emitting elements to a display substrate with minimal process steps.

The fluid assembly and orientation method disclosed by the present invention uses a highly variable local stress applied to each micro-component. This high-variable stress results in a high-variation of velocity, so that as a range where the maximum assembly speed for capture exists, the speed of individual components may fall below this maximum threshold and settle into the well. The second benefit of high variability is the relatively fast arrangement of components on large (meter-scale) substrates. Once sinking into the well, the greatest stress is to prevent the assembled components from moving away from the correct direction, Instead, the misplaced parts are removed. This provides a low-cost and high-speed assembly method that achieves a predicted assembly speed of more than 56 million micro-components per hour. This assembly method is a universal method that can be applied to any number of substrates, but is well suited for low fill factor and high area arrays with limited surface topography.

Therefore, a fluid assembly method for manufacturing a light emitting display is provided. The method provides a light emitting substrate having a top surface on which a plurality of wells are formed. Each well has a bottom surface with a first electrical interface, and a matrix formed by a plurality of column traces and a plurality of walking lines, the plurality of column traces and a plurality of walking lines forming a plurality of column / row intersections . Each column / row intersection is associated with a corresponding one of the wells. A liquid suspension of a light emitting element is also provided. The liquid may be, for example, ethanol, a polyol, a ketone, a halogenated hydrocarbon, or water. The method flows the suspension through the top surface of the light emitting substrate, and the light emitting element is captured in the plurality of wells. The light-emitting substrate is annealed so that each light-emitting element is electrically connected to the first electrical interface of the corresponding well. The liquid suspension may contain a soldering flux, or the fluxing flux may be applied in a separate step before or after capturing the light emitting element in the plurality of wells and before the substrate is annealed. Additional process steps can form a color changing mechanism and a light diffusing mechanism on selected wells.

It is desirable to use a eutectic solder interface metal on the substrate or the light emitting element and to use a flux before thermal annealing. For example, dimethylammonium chloride, diethanolamine, and glycerol solutions can be dissolved in isopropanol. This solution can be used as an assembly fluid (suspension), or it can be introduced after the assembly fluid is removed by sweeping and evaporation.

In some aspects, the light emitting element is a surface mount light emitting diode (SMLED) with two electrical contacts on its top surface (the top surface of the SMLED is facing the well, near the bottom surface of the well). The electrical connection between the light-emitting element and the first electrical interface of the well is then achieved without the need to form a cover metal layer and additional conductive traces, or wire bonding on the substrate after annealing. no Then, if the light emitting element is a vertical LED (having one electrical contact on the top surface and one electrical contact on the bottom surface), an additional metallization step may be required after annealing. Generally, as the light emitting elements are captured in a plurality of wells, the uncaught light emitting elements are collected and reconfigured simultaneously for subsequent light emitting display manufacturing.

On the one hand, an auxiliary mechanism is used to distribute the light emitting elements on the substrate. Some examples of this auxiliary mechanism include brushes (rotating or non-rotating), wipers, rotating cylinders, pressurized fluids, and mechanical vibrations (such as acoustic or ultrasonic). The auxiliary mechanism facilitates the distribution of the light emitting element on the surface of the substrate by contacting or cooperating with the top surface of the light emitting element or the light emitting substrate in the suspension. For example, assuming that the light emitting substrate has a length and a width, the method causes the suspension to flow on the top surface of the light emitting substrate at a first speed along a first direction of the length of the light emitting substrate. An auxiliary mechanism brush has a rotating shaft and a brush length at least equal to the width of the light-emitting substrate, and the brush length is translated in a first direction across the length of the light-emitting substrate. While the brush is being translated for the first pass, the brush is rotated to generate a first region variable of a first speed. In one aspect, the first region variable generated by the brush rotation is greater than the first speed. The method may further repeat the translation of the brush in the first direction or the opposite direction thereof, and the rotation of the brush may generate a regional variable that is greater than or less than the first speed. The brush can rotate at a speed in a range of 120 to 300 revolutions per minute (RPM), and translate on the top surface of the light emitting substrate at a speed in a range of 3 to 10 centimeters per second (cm / s).

In one aspect, the surface mount light emitting element is manufactured to have a post extending from a bottom surface, or the vertical light emitting element is manufactured to have a post extending from a top surface. Then, the light-emitting element moves when the liquid suspension flows over the top surface of the substrate, at least in part in response to a torque generated on a pillar of the light-emitting element. Perhaps more importantly, the pillars extending from the bottom surface can help the surface orientation and directly cover the top surface of the light emitting element on the bottom surface of the well, so these pillars help capture the light emitting element in the well.

Additional details of the above method and a method for transferring light emitting elements of different shapes to a light emitting substrate will be provided below.

200‧‧‧light emitting substrate

202‧‧‧Top surface

204‧‧‧well

208, 208-0, 208-1, 208-2 ‧‧‧ First electrical interface

206‧‧‧ bottom surface

210‧‧‧column alignment

212, 212-0, 212-1, 212-2

214‧‧‧column / row intersection

209-0,209-1,209-2,310‧‧‧Second electrical interface

300‧‧‧ liquid suspension

302‧‧‧Light-emitting element

304‧‧‧First electrical contact

308‧‧‧Top

306‧‧‧Second electrical contact

402‧‧‧First semiconductor layer

404‧‧‧Second semiconductor layer

406‧‧‧Multi-quantum well layer

408‧‧‧electric insulator

500‧‧‧ length

502‧‧‧Width

504‧‧‧first direction

506‧‧‧ Brush

508‧‧‧Shaft

510‧‧‧Brush length

1400‧‧‧ lateral speed

1402‧‧‧speed

602‧‧‧ surface

600‧‧‧columns

804, 800‧‧‧ round well

808,812‧‧‧‧Light emitting element tray

806‧‧‧first diameter

802‧‧‧second diameter

814‧‧‧ third diameter

810‧‧‧Fourth diameter

900‧‧‧ first shape

902‧‧‧Second Shape

904‧‧‧ third shape

906‧‧‧Fourth shape

FIG. 1 is a flowchart of a fluid assembly method for preparing a light emitting display.

2A and 2B are a partial cross-sectional view and a partial plan view, respectively, of an exemplary light emitting substrate that may be provided in step 102 of FIG. 1, for example.

FIG. 3 is a partial cross-sectional view of implementing aspects of steps 104 to 108 of FIG. 1.

4A and 4B are a partial cross-sectional view and a plan view of an exemplary surface mount light emitting diode (SMLED), respectively.

FIG. 5 is a perspective view of an exemplary brush assist mechanism.

FIG. 6 is a partial cross-sectional view of a light emitting substrate occupied by a light emitting element having a pillar.

FIG. 7 is a flowchart of a first modified embodiment of a fluid assembly method for preparing a light emitting display.

FIG. 8 is a plan view supporting an embodiment version of the method shown in FIG. 7.

Fig. 9 is a plan view of a second embodiment version supporting the method shown in Fig. 7.

10 is a flowchart of a second modified embodiment of a fluid assembly method for preparing a light emitting display.

11A and 11B are a partial cross-sectional view and a partial plan view, respectively, of a second exemplary light emitting substrate that may be provided, for example, in step 102 of FIG. 1.

12A and 12B are partial cross-sectional views showing the function of the pillars of the light-emitting element in the orientation of the surface of the light-emitting element.

13A, 13B, and 13C are partial cross-sectional views showing the effect of capture speed on the fluid assembly of the light emitting element.

14 is a partial cross-sectional view showing the effect of the resistance of the fluid assembly suspension on the speed of the light emitting element during the assembly process.

FIG. 1 is a flowchart of a fluid assembly method for manufacturing a light emitting display. Although the method is described as a plurality of steps with a numbered order for clarity, numbering does not necessarily determine the order of the steps. Understandably, some of these steps can be skipped, executed concurrently, or executed without maintaining strict sequencing. However, in general, the method follows the numerical order of the steps shown. The method starts at step 100. Step 102 provides a light emitting substrate.

2A and 2B are respectively a partial cross-sectional view and a partial plan view of an exemplary light emitting substrate, which may be provided in step 102 of FIG. 1, for example. The light-emitting substrate 200 has a top surface 202 and a first plurality of wells 204 (wells 204-0 to 204-2 as shown) formed on the top surface 202. Basically, the substrate top surface 202 is flat, and the plurality of wells 204 are the only surface topography features that affect fluid assembly. Each well 204 includes a bottom surface 206 having a first electrical interface 208 that can be selectively coated with solder. The figures show the first electrical interfaces 208-0 to 208-2. The light emitting substrate 200 is generally transparent, and may have a multilayer structure (not shown) including a glass substrate and a dielectric material covering the glass substrate, and the plurality of wells are formed in the dielectric material. The light-emitting substrate 200 further includes a matrix having a plurality of column lines 210 and a plurality of walking lines 212. The column lines 210 and the walking lines 212 form a plurality of column / row intersections 214. The figures show walking lines 212-0 to 212-3 and column / row intersections 214-0 to 214-3. Each column / row intersection 214 is associated with its corresponding well 204. For example, column / row intersection 214-0 is associated with well 204-0. The column traces 210 and the walking traces 212 may form a simple passive matrix to selectively excite light emitting elements, or as part of an active matrix for the same purpose as described in more detail below. Therefore, the details of the interconnections between the columns, rows, and electrical interfaces are not shown in this figure.

11A and 11B are a partial cross-sectional view and a partial plan view of a second exemplary light-emitting substrate, which may be provided, for example, in step 102 of FIG. 1, respectively. In this regard, the light emitting element is a surface mount light emitting diode (SMLED) as shown in detail in FIGS. 4A and 4B. As explained below, the SMLED has two electrical contacts formed on its top surface, which is a surface opposite to the bottom surface 206 of the well. Therefore, two electrical interfaces are formed on the bottom surface 206 of the well, namely the first electrical interfaces 208-0 to 208-2 and the second electrical interfaces 209-0 to 209-2. In this regard, the light emitting substrate 200 is formed as a passive matrix with column traces and walking traces to selectively activate the plurality of SMLEDs. As shown, the column trace 210 is connected to the first electrical interface (208-0 to 208-2) in the column of the wells 204-0 to 204-2, and the traces 212-0 to 212-2 are respectively connected to the well 204 The second electrical interfaces (209-0 to 209-2) in the columns of -0 to 204-2 are connected.

Returning to FIG. 1, step 104 provides a liquid suspension of the light emitting element, and step 106 flows the suspension through the top surface of the light emitting substrate. The liquid in step 104 may be one of various types of alcohols, polyols, ketones, halogenated hydrocarbons, or water. Step 108 captures the light emitting elements in the plurality of wells. In one aspect, step 104 provides a liquid suspension of a light-emitting element including a flux. Alternatively or additionally, after capturing the light emitting elements in the plurality of wells (step 108) and before annealing the substrate (step 110), step 109a uses a flux to fill the wells into which the light emitting elements have entered.

FIG. 3 is a partial cross-sectional view of various aspects implementing steps 104 to 108 of FIG. 1. The liquid suspension 300 contains light-emitting elements 302, some of which are captured in the well 204, and have at least one light-emitting element first electrical contact 304. The figure also shows the second electrical contact portion 306 of the light emitting element. The contact portions 304 and 306 are each formed on the top surface 308 of the light emitting element 302. Similarly, a second electrical interface 310 is formed on the bottom surface 206 of each well.

Returning to FIG. 1, in step 110, the light emitting substrate is annealed. Due to the annealing, step 112 electrically connects each light-emitting element to the first dielectric interface of the corresponding well. As mentioned above, the first of the well The electrical interface can be coated with solder. Alternatively or in addition, one electrical contact or a plurality of electrical contacts on the light emitting element may be coated with a solder. The annealing is performed at a sufficiently high temperature to melt the flux used.

It is necessary to use a eutectic solder interface metal on a substrate or a light emitting element and to use a flux before thermal annealing. Using atomic concentration (at%), the Au28 / Ge62 solder eutectic has a melting point (MP) of 361 ° C, while the In49 / Sn51 solder has a melting point of 120 ° C. Pure indium has a melting point of 156 ° C, but it has the disadvantage that it cannot be bonded without pressure. The flux may be a solution of dimethyl ammonium chloride, diethanolamine, and glycerol dissolved in isopropanol, an organic acid, or a rosin-type fluid. This solution can be used as an assembly fluid (suspension) or introduced after the assembly fluid is removed by sweeping and evaporation.

4A and 4B are a partial cross-sectional view and a partial plan view showing an exemplary surface-mount light emitting diode (SMLED), respectively. The light-emitting element shown in FIG. 3 may be, for example, a SMLED. The SMLED 302 includes a first semiconductor layer 402 having an n-dopant or a p-dopant. The second semiconductor layer 404 contains a dopant that is not used in the first semiconductor layer 402. A multiple quantum well (MQW) layer 406 is located between the first semiconductor layer 402 and the second semiconductor layer 404. The MQW layer 406 may generally be a series of quantum well layers (not shown) (representatively, 5 layers, for example, 5 nm indium gallium nitride (InGaN) and 9 nm n-doped alternately not shown) GaN (n-GaN)). An aluminum gallium nitride (AlGaN) electron blocking layer (not shown) may be further provided between the MQW layer and the p-doped semiconductor layer. The outer layer may be about 200 nm thick p-doped GaN (Mg-doped). If a higher indium content is used in the MQW, a high-brightness blue LED or a green LED can be formed. The most practical materials for the first semiconductor layer and the second semiconductor layer are gallium nitride (GaN) capable of emitting blue or green light or aluminum gallium indium phosphorus (AlGaInP) capable of emitting red light.

In one aspect, the first electrical contact portion 304 is provided in a ring shape, and the second semiconductor layer 404 is in the shape of a disk, and an edge thereof is located below the ring of the first electrical contact portion 304. The second electrical contact portion 306 It is formed in the ring edge of the first electrical contact portion 304, and the first semiconductor layer 402 and the MQW layer 406 are stacked under the second electrical contact portion 306. A trench is formed between the ring edge of the first electrical contact portion 304 and the second electrical contact portion 306, and the trench is filled with an electrical insulator 408. Additional details of this SMLED are provided in a patent application entitled "DISPLAY WITH SURFACE MOUNT EMMISIVE ELEMENT" (application number: 15 / 410,001, filing date: 2017/1/19) invented by Schuele et al., Which patent here The application is cited as a reference. Advantageously, if a SMLED is used, the electrical connection between each light-emitting element and the first electrical interface in step 112 may eliminate the need to form a cover metal layer, additional conductive traces, and wire bonding the substrate after annealing, There is also no need to apply external pressure on the light-emitting elements to achieve the electrical connection between each light-emitting element and the first electrical interface. In one aspect shown, the SMLED includes a post 410 for alignment and orientation.

More specifically, the step 102 provides a light emitting substrate having a well, wherein the bottom surface of the well has a first electrical interface and a second electrical interface. If a passive matrix (PM) is used, the column traces and traces are connected to the first electrical interface and the second electrical interface. If an active matrix (AM) is used, the column traces and the traces are used to activate a driving circuit associated with each well, and an output terminal of the driving circuit is connected to the first electrical interface. In the case of using AM, the wiring matrix in the light-emitting substrate will also include a line connecting a DC power source to each driving circuit. The light emitting substrate further includes an electrical interface reference voltage network connected to a second electrical interface of each well. More details of the AM and PM implementation are provided in the parent patent application 15 / 410,001.

Next, step 104 provides a liquid suspension containing a surface-mount light-emitting element (such as SMLED). The surface-mount light-emitting element has a bottom surface and a top surface, and a first electrical contact portion and a second electrical contact are formed on the top surface. Contact. Capturing the light emitting element in the well in step 108 includes capturing the top surface of each surface mount light emitting element directly covering the bottom surface of the corresponding well. The first electrical contact of each light-emitting element and the first dielectric of the corresponding well are made by an annealing process (step 112). Surface electrical connection includes electrically connecting a first electrical contact portion of each surface-mount light-emitting element and a first electrical interface of a corresponding well, and a second electrical contact portion of each light-emitting element and a second electrical contact of a corresponding well. The electrical interface is electrically connected.

In a different aspect, the step 104 provides a liquid suspension of a vertical light emitting element including a bottom surface having a first electrical contact portion and a top surface having a second electrical contact portion. This step 108 captures the bottom surface of the light-emitting element to directly cover the bottom surface of its corresponding well, and this step 112 electrically connects the first electrical contact portion of each light-emitting element and the first electrical interface of its corresponding well. In this regard, after step 112 of electrically connecting the first electrical contact portion of the light emitting element and the first electrical interface of its corresponding well, step 114 forms a reference voltage interface layer on the top surface of the light emitting substrate. As can be understood in the art, such a step may require depositing an isolation layer on the top surface of the substrate and etching to open a contact hole penetrating the isolation layer so that a subsequently formed reference voltage interface layer can be electrically connected to The second electrical contact. Step 116 connects the second electrical contact portion of each vertical light emitting element with the reference voltage interface layer. For example, a thin film process may be used to form a metallized interconnect on a top surface of the light emitting substrate. In the case of a passive matrix design using vertical light emitting elements, a part of the column / row matrix (for example, a column line) may be provided as described in step 102 and a part of the column / row matrix (for example, a walking line) ) Is provided in step 114.

In one aspect, step 107 selectively uses an auxiliary mechanism for dispensing light emitting elements. For example, the auxiliary mechanism may be a brush (rotating or non-rotating), a wiper, a rotating cylinder, a pressurized fluid, or a mechanical vibration. The "fluid" can be a gas or a liquid. Examples of the mechanical vibration include sonic vibration and ultrasonic vibration. Step 108 then captures the light-emitting element, at least in part, due to the effect of the auxiliary mechanism on the light-emitting element in the suspension or on the top surface of the light-emitting substrate.

FIG. 5 is a perspective view showing an exemplary brush assist mechanism. Referring to FIGS. 1 and 5, step 102 provides a light emitting substrate 200 having a length 500 and a width 502. Step 106 provides the The light emitting substrate 200 has a suspension having a first velocity in a first direction 504 of a length 500. Then, step 107 uses a brush 506 having a rotating shaft 508 and a brush length 510, which is at least equal to the width 502 of the light-emitting substrate 200 in the subsequent sub-steps. In step 107a, in the first pass, the brush length 510 is translated in a first direction across the length 500 of the light emitting substrate 200. In one aspect, the brush is translated at a speed in the range of 3 to 10 centimeters per second (cm / s) in step 107a. While the brush is being translated for the first pass, step 107b rotates the brush to generate a first region variable in a first speed. As shown, the first region variable is a speed greater than the first speed. Alternatively, the first region variable may be a smaller speed than the first speed. In one aspect, step 107b rotates the brush at a speed of 120 to 300 revolutions per minute (RPM). In one embodiment, the linear velocity of the brush on the surface of the substrate is 35 cm / s, and a low-speed capture area appears in the front of the brush pushing the suspension to move.

For example, a cylindrical brush used as an auxiliary mechanism may have an outer diameter of 50 mm and be composed of a plurality of 3 mm tufts formed by 75 micron diameter nylon or polypropylene bristles, and the plurality of tufts may be arranged to be closely packed. The spiral pattern or bidirectional spiral pattern, the tuft distance from the center point to the center point is 6mm. These dimensions are given above to illustrate a cylindrical brush that has fine, closely packed bristles made of a non-contaminating material and has a better interaction with both the micro-component and the carrier fluid.

In a specific example, the brush starts from the first edge of the substrate. In the first step, the brush is moved towards the second edge of the substrate and rotated counterclockwise to increase the area variable. In the second step, the brush stops at a short distance from the second edge, and the rotation is reversed clockwise. In the third step, the brush continues to move to the second edge, but then moves in the opposite direction toward the first edge and still keeps rotating clockwise. In the fourth step, the brush stops at a short distance from the first edge, and the reverse rotation is a counterclockwise rotation. In the fifth step, the brush finishes moving to the first edge. Optionally, the above steps may be repeated.

If the substrate is tilted at an angle, the flow velocity at the first speed may be driven by gravity. The flow rate may also be an oscillation or a pulse. It should also be understood that the speed of the light emitting elements in the suspension is not necessarily the same as the speed of the liquid. The first speed as in this application refers to the liquid speed.

In one aspect, the liquid suspension is a plurality of LEDs with a high concentration of 2 to 8 microns thick in isopropanol, and the LED has a diameter or maximum cross-sectional size of 20 to 150 microns. There is a low thickness of isopropyl alcohol on the substrate surface, and a level brush with nylon or polypropylene bristles rotates close to the substrate surface. The brush is equal in length to one dimension of the substrate so that the brush can completely cover the surface of the substrate when translated across. In translation, the rotation initially causes the linear velocity of the bristles that are in contact with the liquid suspension to have the same direction and a higher amplitude as the translation. In this way, the brush forces the light-emitting elements across the surface of the substrate to converge. A single light-emitting element typically moves rapidly from its moving point and travels at a large initial speed (close to the linear speed of the brush) and moves a distance from the brush before settling on the surface again. Usually this settling causes it to be assembled into a well.

13A to 13C are partial cross-sectional views showing the effect of capture speed on the fluid assembly of a light emitting element. When the light emitting element speed (V _O ) is less than or equal to the critical capture speed (V _CRIT ), the light emitting element 302 moves slowly enough to be captured in the well 204. The critical capture speed is manifested in the initial conditions for the light-emitting element to approach the capture well position, combined with fluid dynamics, the shape of the light-emitting element and the local substrate, and the initial element position relative to the well, etc., which defines a magnitude of velocity, Above this magnitude, the light-emitting element cannot be captured, and below this magnitude, the light-emitting element is captured. A decisive factor is whether the interaction between the sidewall of the well and the light emitting element provides resistance on the light emitting element. In this way, even if the main part of the light-emitting element sinks below the plane of the top surface of the substrate, further fluid force drives the light-emitting element out of the well if the edge of the side wall of the light-emitting element guide is completely on the plane of the top surface of the substrate. In contrast, if the leading edge of the light emitting element is captured by the sidewall of the well, its momentum is transferred to the substrate and it may settle into the well. The fixed downward force (excluding the hydrodynamic force) acting on the light-emitting element is gravity opposite to the buoyancy generated in the fluid. Therefore, V _{CRIT is} determined by fluid density as well as geometry and initial conditions.

This critical capture velocity is shown in a two-dimensional map, and in fact, the path traveled by the light emitting element may not pass through the center of the well, and therefore includes components moving in or out of the two-dimensional map. Because the fall of the light-emitting element before it touches the far side wall of the well determines whether the light-emitting element is captured, and the path through the center represents the longest path that the light-emitting element can take without touching the side wall, it is understandable that Significantly reduced speed is required to capture light-emitting elements traveling eccentrically along the well. In other words, the magnitude of the critical capture velocity is described for a light-emitting element traveling above the center of the well, and the maximum limit value (first order) for assembly is described. To achieve high yields in practice, the minimum light emitting element speed is significantly lower than the V _CRIT described here.

14 is a partial cross-sectional view showing the effect of the resistance of the fluid assembly suspension on the speed of the light emitting element during the assembly process. When the carrier fluid velocity (V) is greater than the critical carrier fluid velocity (V _CRIT ), the brush 506 may push the light-emitting disc upwards away from the surface 202 of the substrate. As shown, the force acting on the light emitting element 302 may also be a function of the lateral speed 1400 of the brush 506 and the rotational speed 1402 of the brush 506. The fluid may be turbulent, and to some extent the movement of the light-emitting element is independent of the overall fluid flow (beyond the initial brush stroke). Generally, there are high-density light-emitting elements near the brush area, and then the light-emitting elements are dispersed forward on the substrate, relying on fluid flow and experiencing resistance, decelerating, and eventually settle on the surface and enter the well before the advancing brush reaches them. Therefore, the initial speed of the brush must be very high, but the light-emitting element 302 decelerates and stabilizes at a speed lower than V _CRIT , which is the main advantage of the brush method used. The higher-speed bristles will cause the incorrectly-oriented light plate to fall off, and push the high-density waves in front of the light-emitting element in front of it, thereby giving them the opportunity to locate in front of the brush. The bristle speed (mainly from the rotation speed of the brush) is selected by the release force window used to orient the light-emitting disc, and the linear travel speed of the brush is selected by the settling time of the light-emitting element in the liquid. In this way, the assembly method separates the individual light-emitting element assembly speed (which is limited by V _CRIT ) from the overall display element assembly speed (which is fast).

Assembly can be done in less than one pass, so it is usually necessary to perform multiple translation and rotation changes in direction. However, translation and rotation need not change direction at the same time. In order to save the occupation of unassembled components on the substrate surface (i.e., not in the well), the rotation is first changed while the brush is translated in the same direction as before, until all unassembled components are brought back towards the assembly area. The brush's translation direction is also changed.

In one aspect, the maximum local density of the light-emitting element when assembled is about 0.3-0.8 single layer of the component to allow space for settlement with a large number of opportunities for capture. When the light emitting element is captured, it is desirable to replenish the number of uncaught (misaligned) light emitting elements in front of the moving brush and an additional dose of suspension fluid. Good results are obtained with excess components, that is, the number of components in the liquid suspension above the assembly area exceeds the number of capture points by at least 50% to increase capture yield and reduce assembly time. After all positions (wells) are occupied by correctly oriented light-emitting elements, use the same brushing tool but use a different scheme (e.g., to translate the brush to a degree beyond the substrate area with a uniform rotation direction) to remove excess unassembled element. The swept components are collected in a reservoir for reuse (steps 109a and 109b).

One factor that underscores this approach is that the electrical contact of the components does not occur during assembly or after assembly is only achieved by the deposited metal, but rather occurs at an annealing that exceeds the eutectic melting temperature of the metal at the interface between the light emitting element and the substrate period. Although some prior art methods include a flux (such as HCl) in an aqueous suspension for molten solder assembly, this method gradually dissolves the solder contacts, making consistent electrical connection to the micro-component difficult. The concentration of the flux used in the present application was initially low enough not to be corrosive, but during annealing, the residual isopropanol was first volatilized and then glycerol was volatilized. In each step, the concentration of the flux increases, removing surface oxidation And contaminants to keep the metal surface clean and easy to bond. Unlike the pick-and-place method, this method achieves good electrical contact without requiring any external pressure on the component interface.

In one aspect, step 106 causes the light emitting element to flow in a suspension, the light emitting element having a higher volume percentage at the top surface of the light emitting substrate than the liquid. In a related modified embodiment, step 106 is in a range of 0.3 to 0.8 single layer, and the suspension is flowed through the top surface of the light-emitting substrate by generating the maximum local density of the light-emitting element in the suspension.

FIG. 6 is a partial cross-sectional view of a light emitting substrate occupied by a light emitting element having a pillar. Referring to FIGS. 1 and 6, step 104 provides a liquid suspension of a light emitting element 302 having a post 600 extending from a surface 602. In this embodiment, the light-emitting element is a surface-mount light-emitting element. Step 106 The flowing liquid suspension is performed by moving the light emitting element across the top surface of the substrate, at least in part, in response to the torque generated on the pillar 600 of the light emitting element. Further, capturing the light-emitting element in the well (step 108) may include surface-oriented surface-mounting the light-emitting element top surface 308 directly covering the bottom surface of the well through the pillar 600 of the light-emitting element.

12A and 12B are partial cross-sectional views showing a function of a pillar on a surface orientation of a light emitting element. During fluid assembly, the liquid flow (indicated by arrow 1200) causes a drag force to act on the pillars 600 of the light emitting element 302 across the surface of the substrate 200. Since the post 600 extends from the light emitting element surface 602, the drag force has an asymmetrical effect on the surface orientation of the surface diode. In particular, the drag force causes a positive moment around a fixed fixed point of rotation (eg, the edge of the light emitting element that is in contact with the surface of the substrate 200), which flips the inverted light emitting element 302 into a non-inverted orientation. In contrast, the drag force acting on the non-inverted light-emitting element 302 due to the liquid flow is mainly caused by the disturbance of the surrounding column 600, and the force applied on the light-emitting element 302 results in a negative net moment. This negative net moment forces the leading edge of the light emitting element (ie, the edge guided in the direction of arrow 1200) downward and stabilizes the light emitting element in a non-inverted direction.

Similar asymmetric effects of drag force occur in light emitting elements 302 (see FIG. 12A) deposited in well 204 in a non-inverted orientation and light emitting elements 302 (see FIG. 12B) deposited in well 204 in an inverted orientation. between. As shown in FIG. 12A, any moment in the lower right corner of the surrounding light emitting element 302 caused by the liquid flow is cancelled by the force applied on the surface 602, resulting in a negative net moment tending to maintain the light emitting element deposited in the well 204. As shown in FIG. 12B, when the light-emitting element 302 is inverted in the well 204, the surface 602 acts as a hydrofoil that generates a lifting force from the liquid flow, so that a positive net moment acts on the side of the light-emitting element 302 that is opposite to the well 204 Touch the right side. This positive net moment tends to cause the light-emitting element 302 to flip in the direction shown by arrow 1202, so that the light-emitting element is driven out of the well 204 and when the liquid flow moves the light-emitting element toward another downstream well that may re-deposit, it is possible Become a non-inverted orientation.

In one aspect, while capturing the light emitting elements in the well (step 108), step 109b collects the uncaught light emitting elements, and step 109c resuspends the collected light emitting elements for subsequent manufacturing of the light emitting display. In another aspect, step 118 forms a plurality of color changing mechanisms that cover the exposed surfaces of the corresponding plurality of light emitting elements. Alternatively or in addition, step 118 forms a plurality of light diffusion mechanisms covering the corresponding plurality of light emitting elements.

If the light-emitting element has two bottom contacts (for example, SMLED), annealing (step 110) is the last processing step, which can save color change integration and passivation processing. If the electrode is on the opposite surface as in the case of a vertical light emitting element, a passivation layer is deposited on the top surface contact portion of the light emitting element and exposes the contact portion, and the patterned metal achieves an electrical connection with the light emitting element ( Steps 114 and 116).

FIG. 7 is a flowchart of a first modified embodiment of a fluid assembly method for preparing a light emitting display. The method starts at step 700. Step 702 provides a light emitting substrate having a top surface on which a plurality of wells are formed. Each well includes a bottom surface having a first electrical interface, and the substrate further includes a matrix formed by a plurality of column traces and walking lines, and the plurality of column traces and walkings Lines form a plurality of column / row intersections. Each column / row intersection is associated with its corresponding well. Step 704 provides a first liquid suspension containing a first type of light emitting element. In step 706, the first suspension flows through the top surface of the light-emitting substrate. Step 708 captures the first type of light emitting element in the well. Step 710 provides a second liquid suspension containing a second type of light emitting element. Step 712 The second suspension flows through the top surface of the light emitting substrate. Step 714 performs final annealing of the light emitting substrate. With the final annealing, the light-emitting element is electrically connected to the first electrical interface of the corresponding well in step 716. In one aspect, before the second suspension flows, step 709 performs an initial anneal to electrically connect the light emitting element of the first type that has been captured in the well to the electrical interface. The specific details of the manufacturing method can be found in the foregoing description of FIG. 1, and for the sake of brevity, it will not be repeated here. In one aspect, the well in which the captured light emitting element of the second type is located is formed after step 708 and before step 712.

In one aspect, before the final annealing in step 714, step 713a provides a third liquid suspension containing a third type of surface mount light-emitting element. Step 713b, the third suspension flows through the top surface of the light emitting substrate. Although not shown, an additional step after step 713b is to anneal the third type of light emitting element to connect the third type of light emitting element to the electrical interface of the well where it has been captured. Although not shown, the method can be extended to deposit any number of light-emitting element types in a corresponding number of different suspensions.

FIG. 8 is a plan view supporting an embodiment version of the method shown in FIG. 7. Here, step 702 provides a light emitting substrate having a plurality of circular wells 804 having a first diameter 806 and a plurality of circular wells 800 having a second diameter 802, wherein the second diameter 802 is smaller than the first diameter 806. Then, the first liquid suspension of step 704 provides a first type of light emitting element tray 812, which is a circular shape having a third diameter 814 larger than the second diameter 802 and smaller than the first diameter 806 shape. Step 710 provides a second liquid suspension containing a light emitting element tray 808 of a second type, which is a circular shape having a fourth diameter 810 smaller than a second diameter 802.

Fig. 9 is a plan view of a second embodiment version supporting the method shown in Fig. 7. In this regard, step 702 provides a light emitting substrate having a plurality of wells having a first shape 900 and a plurality of wells having a second shape 902, which is different from the first shape 900. In this embodiment, the first shape 900 is a square, and the second shape 902 is a circle. However, the method is not limited to any particular shape or combination of shapes. Step 704 provides a first liquid suspension containing a first type of light-emitting element. The first type of light-emitting element has a third shape 904. The third shape 904 can be filled in the first shape well 900, but cannot be filled in. In a second shape well 902. Step 710 provides a second liquid suspension containing a second type of light emitting element. The second type of light emitting element has a fourth shape 906 that can be filled in the second shape well 902. In one aspect, the light emitting element having the fourth shape 906 cannot be filled in the first shape well 900.

10 is a flowchart of a second modified embodiment of a fluid assembly method for preparing a light emitting display. The method starts at step 1000. Step 1002 provides a light emitting substrate having a top surface, a plurality of wells having a first shape, and a plurality of wells having a second shape different from the first shape. Each well includes a bottom surface having a first electrical interface. Step 1002 also provides a matrix formed by a plurality of column traces and a plurality of walking lines, where the plurality of column traces and the plurality of walking lines form a plurality of column / row intersections. Each column / row intersection is associated with a corresponding well. Step 1004 provides a liquid suspension containing a light emitting element of a first type. The light emitting element of the first type has a third shape. The third shape can be filled in the first shape well, but cannot be filled in the second shape well. The liquid suspension of step 1004 also contains a second type of light-emitting element. The second type of light-emitting element has a fourth shape. The fourth shape can be filled in the second shape well, but cannot be filled in the first shape well. Step 1006 The suspension flows over the top surface of the light emitting substrate. Step 1008 captures a first type of light emitting element in a first shape well and captures a second type of light emitting element in a second shape well. Step 1010 anneals the light emitting substrate. By annealing, step 1012 electrically connects the light-emitting element and the first electrical interface of the corresponding well.

The application provides a fluid assembly process for manufacturing a light emitting display. Examples of specific materials, dimensions, and circuit layouts have been provided to illustrate the invention. However, the present invention is not limited to these embodiments. Those skilled in the art will envision other variations and embodiments of the invention.

Claims (25)

A fluid assembly method for manufacturing a light-emitting display is improved. The method includes: providing a light-emitting substrate having a top surface and a matrix formed by a plurality of column traces and a plurality of traces, and a top surface is formed on the top surface. A plurality of wells, each well including a bottom surface having a first electrical interface, the plurality of column traces and the plurality of walking lines forming a plurality of column / row intersections, wherein each column / row intersection and a corresponding Associated with a well; providing a liquid suspension of a light-emitting element having a post extending from one surface thereof; passing the suspension through a top surface of the light-emitting substrate; capturing the light-emitting element in the plurality of In a well; annealing the light-emitting substrate; and electrically connecting each light-emitting element to a first electrical interface of a well corresponding thereto by the annealing. The method according to claim 1, wherein: electrically connecting each light-emitting element includes connecting each light-emitting element to the first electrical interface without forming a cover metal layer, adding conductive traces, or bonding wires on a substrate. The method according to claim 1, wherein the method further comprises: using an auxiliary mechanism for dispensing the light emitting element, the auxiliary mechanism selected from the group consisting of a rotating or non-rotating brush, a wiper, a rotating cylinder, and a pressurized fluid And a group consisting of mechanical vibration; wherein said capturing said light-emitting element in said well comprises: capturing said light-emitting element by cooperating with a light-emitting element in said suspension or a top surface of said light-emitting substrate by said auxiliary mechanism. The method of claim 3, wherein: providing the light-emitting substrate comprises providing a light-emitting substrate having a length and a width; wherein flowing the suspension through the top surface of the light-emitting substrate includes crossing the light The suspension is supplied at a first speed in a first direction of the length of the substrate; wherein using the auxiliary mechanism includes using a brush having a rotating shaft and a length of the brush at least equal to the width of the light-emitting substrate. Use as follows: In the first pass, the length of the brush will be translated along the first direction to span the length of the light-emitting substrate; while the first pass of the brush is translated, the brush is rotated to produce The first region variable in the first speed is described. The method of claim 4, wherein: using the auxiliary mechanism comprises: rotating the brush at a rate in a range of 120 to 300 revolutions per minute (RPM); and at a rate of 3 to 10 centimeters per second (cm / Speed of range s) to translate the brush. The method of claim 1, wherein providing the light-emitting substrate includes a solder-coated first electrical interface. The method of claim 1, wherein flowing the suspension through the top surface of the light-emitting substrate includes forming a single layer having a maximum local density of 0.3-0.8 in the suspension. The method of claim 1, wherein providing the liquid suspension of the light-emitting element includes providing a vertical light-emitting element having a bottom surface with a first electrical contact portion and a second surface with a second electrical contact portion A top surface, wherein capturing the light-emitting element in the plurality of wells includes capturing a bottom surface with the light-emitting element to directly cover a bottom surface of a well corresponding thereto; wherein each of the light-emitting element and a first electric power of the well corresponding thereto are captured The interface electrical connection includes electrically connecting the first electrical contact portion of each of the light emitting elements and a first electrical interface of a corresponding well therewith. The method of claim 1, wherein: electrically connecting each of the light-emitting elements includes electrically connecting each of the light-emitting elements with a first electrical interface of a well corresponding thereto, without applying the light-emitting element. External pressure. The method of claim 1, wherein flowing the liquid suspension through the top surface of the light-emitting substrate includes moving the light-emitting element through the top surface of the substrate at least partially under impact. The effect of the torque generated by the pillar of the light-emitting element is described. The method of claim 1, wherein capturing the light-emitting element in the plurality of wells includes directing a surface of the light-emitting element through a pillar of the light-emitting element to directly cover a surface of the well. Bottom surface. The method of claim 1, wherein: providing the light-emitting substrate comprises each of the wells including a bottom surface having a first electrical interface and a second electrical interface; wherein providing a liquid suspension of the light-emitting element includes providing Surface-mount light-emitting elements on the bottom surface and the top surface, and the surface-mount light-emitting element has a first electrical contact portion and a second electrical contact portion formed on the top surface; wherein the light-emitting element is captured in the plurality of The well includes capturing the top surface of each surface-mount light-emitting element to directly cover the bottom surface of the well corresponding to it; electrically connecting each of the light-emitting elements and the first electrical interface of the well corresponding thereto by the annealing includes connecting each The first electrical contact portion of each of the surface mount light emitting elements is electrically connected to a first electrical interface of a well corresponding thereto, and the second electrical contact portion of each of the light emitting elements and a well corresponding thereto are electrically connected The second electrical interface is electrically connected. The method according to claim 1, wherein providing a liquid suspension of the light-emitting element includes providing a suspension containing a flux. The method according to claim 1, wherein the method further comprises: after capturing the light-emitting element in the plurality of wells and before annealing the light-emitting substrate, filling the light-filled element that has been filled with the light-emitting element with a flux. well. The method according to claim 1, wherein: the method further comprises: capturing the light emitting elements while collecting the plurality of wells, collecting the light elements not captured; and resuspending the collected light emitting elements for subsequent use Of light emitting display. The method according to claim 1, wherein the method further comprises: forming a plurality of color changing mechanisms and covering the exposed surfaces of the corresponding plurality of light emitting elements. The method according to claim 1, wherein the method further comprises: forming a plurality of light diffusion mechanisms and covering the corresponding plurality of light emitting elements. The method of claim 1, wherein providing a liquid suspension of the light-emitting element comprises providing a liquid selected from the group consisting of ethanol, a polyol, a ketone, a halogenated hydrocarbon, and water. The method of claim 1, wherein providing the liquid suspension of the light-emitting element includes providing a light-emitting element having electrical contacts coated with solder. A fluid assembly method for manufacturing a light-emitting display is improved. The method includes: providing a light-emitting substrate having a top surface and a matrix formed by a plurality of column traces and a plurality of traces, on the top surface. A plurality of wells are formed, each well including a bottom surface having a first electrical interface, the plurality of column traces and the plurality of walking lines forming a plurality of column / row intersections, wherein each of the columns / rows The intersection is associated with a corresponding one of the wells; providing a first liquid suspension containing a first type of light emitting element; flowing a first suspension through the top surface of the light emitting substrate; capturing the first type of light emitting element at In the plurality of wells; providing a second liquid suspension containing a second type of light emitting element; flowing a second suspension through the top surface of the light emitting substrate; performing final annealing on the light emitting substrate; and by The final annealing electrically connects the light emitting element and the first dielectric interface of the corresponding well; wherein the well providing the light emitting substrate includes providing a plurality of wells having a first shape, and Providing a plurality of wells having a second shape; wherein providing the first liquid suspension includes providing a light emitting element of a first type, the light emitting element of the first type having a third shape, and the third shape can be filled in the The well of the first shape cannot be filled in the well of the second shape; providing the second liquid suspension includes providing a light emitting element of a second type, and the light emitting element of the second type has a fourth shape. The fourth shape can be filled in the well of the second shape. The method according to claim 20, wherein the method further comprises: before the final annealing, providing a third liquid suspension containing a third type of surface mount light-emitting element; and passing the third suspension through the light-emitting substrate The top surface. The method according to claim 20, wherein the plurality of wells having a first shape are a plurality of circular wells having a first diameter, and the plurality of wells having a second shape are smaller than the first A plurality of circular wells of a second diameter in diameter; wherein providing the first liquid suspension includes providing a light emitting element disc of a first type having a circle having a third diameter, the third diameter being greater than the second diameter Diameter and smaller than the first diameter; wherein providing the second liquid suspension includes providing a second type of light emitting element disc having a circular shape having a fourth diameter, the fourth diameter being smaller than the second diameter. The method of claim 20, wherein the first shape is different from the second shape. The method of claim 20, wherein the method further comprises: performing an initial annealing before flowing the second suspension. A fluid assembly method for manufacturing a light-emitting display, which is improved in that the method includes: providing a light-emitting substrate having a top surface, a plurality of wells having a first shape, and a first hole having a shape different from the first shape. A plurality of wells of two shapes, each well including a bottom surface having a first electrical interface, and providing a matrix formed by a plurality of column traces and a plurality of walklines, the plurality of column traces and the plurality of walklines Forming a plurality of column / row intersections, wherein each of said column / row intersections is associated with a corresponding one of the wells; providing a liquid suspension containing a first type light emitting element and a second type light emitting element, said first type The light-emitting element has a third shape that can be filled in the well of the first shape but cannot be filled in the well of the second shape. The second-type light-emitting element has a fourth shape. Four shapes can be filled in the wells of the second shape but not in the wells of the first shape; the suspension is allowed to flow through the top surface of the light-emitting substrate; A type of light emitting element in the first shape well, capturing the second type of light emitting element in the second shape well; annealing the light emitting substrate; and annealing the light emitting element and corresponding to the light emitting element The first electrical interface of the well is electrically connected.