CN114334839A - Transfer method of LED chip - Google Patents

Abstract

The application relates to the technical field of display arrays and discloses a transfer method of an LED chip, which comprises the following steps: providing a substrate, and putting a solution mixed with an LED chip into the substrate; the solution mixed with the LED chips is thrown onto the substrate provided with the electrodes arranged at intervals, the solution flows freely on the substrate to drive the LED chips to move randomly, after the solution is evaporated, the LED chips are deposited on the substrate, the LED chips can be basically distributed approximately uniformly, the distance between the two electrodes of the LED chips is larger than the minimum distance between any two adjacent electrodes on the substrate, the two electrodes of the two LED electrodes have the highest probability of falling on different electrodes and electrically contacting, the transferring process is completed, and the whole manufacturing process is simple.

Description

Transfer method of LED chip

Technical Field

The present application relates to a display array technology, and more particularly, to a method for transferring an LED (Light Emitting Diode) chip.

Background

The micro light emitting diode display technology is an advanced display technology and has the advantages of high brightness, high color gamut, low power consumption, wide viewing angle, high contrast, high color saturation, high response rate and the like. The transfer technology is an important process in the preparation process of the micro light-emitting diode display array and is also an important bottleneck in the commercialization of the micro light-emitting diode. In the current transfer method, for example, the LED chips need to be aligned by applying power, which has the problems of complex process and high cost.

Disclosure of Invention

The application aims to provide a transfer method of an LED chip, and aims to solve the problems of complex process and high cost in the conventional transfer technology.

The embodiment of the application provides a method for transferring an LED chip, which comprises the following steps:

providing a substrate, putting a solution mixed with an LED chip into the substrate, wherein the substrate is provided with a plurality of electrode units, each electrode unit comprises a plurality of substrate electrodes, each LED chip comprises a chip main body and two chip electrodes arranged on the chip main body at intervals, and the distance between the two chip electrodes of each LED chip is larger than the minimum distance between any two adjacent substrate electrodes;

heating to evaporate the solution so that the LED chip is placed on the substrate.

In one embodiment, the solution is further mixed with a photoresist, and after the heating to evaporate the solution, the LED chip disposed on the substrate is wrapped with a photoresist layer.

In one embodiment, the transfer method further includes:

removing the photoresist wrapped on the two chip electrodes of the LED chips and between the adjacent LED chips in an exposure mode;

forming metal layers on the LED chip and the substrate in a metal deposition mode;

and removing the photoresist deposited on the LED chip, and forming metal connection between two chip electrodes of the LED chip and the corresponding substrate electrodes.

In one embodiment, the solution further incorporates metal ions, and the heating to evaporate the solution comprises:

pre-evaporating the solution to evaporate a portion of the solution;

covering two chip electrodes of the LED chip and the substrate electrode with metal layers through electroplating;

the remaining solution was evaporated.

In one embodiment, the solution is mixed with flux and the substrate is further covered with a solder material, and the heating to evaporate the solution comprises:

carrying out a first-stage evaporation treatment on the solution;

heating the substrate to fuse the two chip electrodes of the LED chip, the substrate electrode and the welding material;

the remaining solution was evaporated to dryness.

In one embodiment, the substrate is provided with a plurality of areas, each area corresponds to one electrode unit, and the solution mixed with the LED chips is put into the substrate;

the solution is placed into each of the zones separately.

In one embodiment, the solution mixed with the photoresist further comprises, before the step of placing the solution into each of the regions:

printing a light conversion material to the area;

the heating to evaporate the solution comprises:

heating to evaporate the solution, wherein the outer surface of the LED chip is wrapped with the photoresist and the light conversion material.

In one embodiment, the regions include an R electrode region, a G electrode region, and a B electrode region; the printing of the light conversion material to the area includes:

printing the light conversion material to the R electrode area and the G electrode area respectively;

the heating to evaporate the solution comprises:

heating to evaporate the solution, wherein the photoresist and the light conversion material are wrapped on the outer surfaces of the LED chips of the R electrode area and the G electrode area, and the photoresist is wrapped on the outer surface of the LED chip of the B electrode area.

In one embodiment, after the heating to evaporate the solution, the method further comprises:

removing the photoresist which is wrapped between the two chip electrodes of the LED chip and the adjacent LED chip in an exposure mode;

and forming a metal layer between the two chip electrodes of the LED chip and the electrode in the electrode area by means of metal deposition.

In one embodiment, the solution includes a first solution mixed with a first light conversion material, a photoresist, and metal ions, a second solution mixed with a second light conversion material, a photoresist, and metal ions, and a third solution mixed with a photoresist and metal ions, the regions including an R electrode region, a G electrode region, and a B electrode region, and the solution mixed with an LED chip is put into a substrate, and the method includes:

putting the first solution into the R electrode area;

placing the second solution into the G electrode area;

and putting the third solution into the B electrode area.

In one embodiment, the heating to evaporate the solution comprises:

pre-evaporating the solution to evaporate a part of the solution;

covering two chip electrodes of the LED chip and the substrate electrode with metal layers through electroplating;

the remaining solution was evaporated by heating.

In one embodiment, the two chip electrodes of the LED chip are respectively wrapped at two ends of the chip main body.

In one embodiment, the plurality of substrate electrodes includes first substrate electrodes and second substrate electrodes, the first substrate electrodes and the second substrate electrodes on the substrate are arranged in a staggered manner along a longitudinal direction, and the first substrate electrodes and the second substrate electrodes on the substrate are arranged in a staggered manner along a transverse direction.

In one embodiment, the cross-sectional shapes of the first substrate electrode and the second substrate electrode are regular triangles, and the ratio of the minimum distance between the first substrate electrode and the second substrate electrode to the side length of each regular triangle is in the range: 0.005-0.05, wherein the ratio range of the side length of the regular triangle to the distance between the two chip electrodes of the LED chip is as follows: 0.1 to 1.

In one embodiment, the cross-sectional shapes of the first substrate electrode and the second substrate electrode are square, and the ratio of the minimum distance between the first substrate electrode and the second substrate electrode to the side length of the square is in the range: 0.01-0.1, wherein the ratio range of the side length of the square to the distance between two chip electrodes of the LED chip is as follows: 0.2 to 1.4.

In one embodiment, the cross-sectional shapes of the first substrate electrode and the second substrate electrode are square, and the distance between the two chip electrodes of the LED chip is smaller than the sum of the side length of the square and the minimum distance between the first substrate electrode and the second substrate electrode.

In one embodiment, the minimum spacing between adjacent electrode units is equal to the minimum distance between the first and second substrate electrodes between the electrode units.

In one embodiment, the plurality of substrate electrodes further includes a third substrate electrode, and any one of the first substrate electrode, the second substrate electrode, and the third substrate electrode on the substrate is adjacent to two other substrate electrodes, respectively.

In one embodiment, the cross-sectional shapes of the first substrate electrode, the second substrate electrode and the third substrate electrode are circular, and the ratio of the minimum distance between the first substrate electrode and the second substrate electrode to the diameter of the circle is in the range of: 0.01-0.1, the ratio range of the diameter of the circle and the distance between two chip electrodes of the LED chip is as follows: 0.6 to 2.

In one embodiment, the cross-sectional shapes of the first substrate electrode, the second substrate electrode and the third substrate electrode are regular hexagons, and the ratio of the minimum distance between the first substrate electrode and the second substrate electrode to the side length of the regular hexagons is in the range: 0.05-0.2, wherein the ratio range of the side length of the regular hexagon to the distance between two chip electrodes of the LED chip is as follows: 0.2 to 2.

In one embodiment, the minimum distances among the first substrate electrode, the second substrate electrode and the third substrate electrode in the electrode units are consistent, and the minimum distance between adjacent electrode units is equal to the minimum distance between the first substrate electrode and the second substrate electrode among the electrode units.

In one embodiment, in two adjacent substrate electrodes, a pair of limiting grooves is formed from the middle of one electrode to the middle of the other electrode.

In one embodiment, the sum of the length of the pair of limiting grooves and the minimum distance between two corresponding adjacent substrate electrodes is 1.05 times to 1.3 times of the distance between two chip electrodes of the LED chip.

In one embodiment, the solution comprises one or more of deionized water, toluene, xylene, methanol, ethanol, and isopropanol.

In one embodiment, the chip body is a cylinder, and the two chip electrodes are arranged on the side surface of the cylinder at intervals.

In one embodiment, the chip electrode is a circular ring structure, and the difference between the outer diameter of the chip electrode and the radius of the chip body is greater than 0 and less than 3 mm.

In one embodiment, the distance between the two chip electrodes is equal to the difference between the distance between the two ends of the chip body and the width between the two chip electrodes.

In one embodiment, the chip body is a cylinder, the two chip electrodes are arranged at two ends of the cylinder at intervals, and the distance between the chip electrodes is equal to the distance between the two ends of the cylinder.

In one embodiment, the chip body is a cylinder, and the two chip electrodes respectively coat the ends of the cylinder.

In one embodiment, the chip main body is a prism, the two chip electrodes are arranged on the side surfaces of the prism at intervals, the chip electrodes include a plurality of chip sub-electrodes, the number of the chip sub-electrodes is equal to the number of the side edges of the prism, and each chip sub-electrode is convexly arranged on one side surface of the chip main body to form a corresponding annular array.

According to the method for transferring the LED chips, the solution mixed with the LED chips is thrown onto the substrate provided with the electrodes arranged at intervals, the solution flows freely on the substrate to drive the LED chips to move randomly, after the solution is evaporated, the LED chips are deposited on the substrate, the LED chips can be basically and approximately uniformly distributed, the distance between two chip electrodes of the LED chips is larger than the minimum distance between any two adjacent electrodes on the substrate, and the two chip electrodes of the two LED electrodes with the maximum probability fall on different electrodes and are electrically contacted, so that the transferring process is completed.

Drawings

Fig. 1 is a schematic structural diagram of an LED chip in an embodiment of the present application;

FIG. 2 is a schematic structural diagram of another LED chip in the embodiment of the present application;

FIG. 3A is a schematic diagram of a substrate with square electrodes according to an embodiment of the present disclosure;

FIG. 3B is a schematic diagram of a structure of an LED chip transferred to a substrate with square electrodes according to an embodiment of the present disclosure;

FIG. 4A is a schematic structural diagram of a substrate with regular triangular electrodes according to an embodiment of the present disclosure;

FIG. 4B is a schematic structural diagram of an embodiment of an LED chip transferred to a substrate having regular triangular electrodes;

FIG. 5A is a schematic structural diagram of a substrate with regular hexagonal electrodes according to an embodiment of the present disclosure;

FIG. 5B is a schematic structural diagram of an LED chip transferred to a substrate with regular hexagonal electrodes according to an embodiment of the present disclosure;

FIG. 6A is a schematic structural diagram of a substrate with circular electrodes according to an embodiment of the present disclosure;

FIG. 6B is a schematic structural diagram of an embodiment of the present invention in which an LED chip is transferred to a substrate having circular electrodes;

FIG. 7 is a schematic cross-sectional view of a pixel structure with two types of electrodes according to an embodiment of the present application;

FIG. 8 is a schematic cross-sectional view of a pixel structure with three types of electrodes according to an embodiment of the present application;

fig. 9 is a circuit diagram of a driving circuit in the pixel structure shown in fig. 7;

fig. 10 is a circuit diagram of a driving circuit in the pixel structure shown in fig. 8;

fig. 11 is a schematic cross-sectional structure diagram of a pixel structure having two types of multiple electrodes in an embodiment of the present application;

fig. 12 is a schematic cross-sectional structure diagram of a pixel structure having three types of multiple electrodes in an embodiment of the present application;

fig. 13A is a schematic top view of the electrode layer in the pixel structure shown in fig. 11;

FIG. 13B is a schematic bottom view of the electrode line layer in the pixel structure shown in FIG. 11;

FIG. 14A is a schematic diagram of a top view of the electrode layer in the pixel structure shown in FIG. 12;

FIG. 14B is a schematic bottom view of the electrode line layer in the pixel structure shown in FIG. 12;

FIG. 15 is a diagram illustrating a split layout of a pixel structure in an embodiment of the present application;

FIG. 16 is a schematic view of a stacked layout of a pixel structure in an embodiment of the present application;

fig. 17 is a current timing diagram of the power supply line of the driving circuit shown in fig. 9;

fig. 18 is a current timing chart of the power supply line of the drive circuit shown in fig. 10;

fig. 19 is a flowchart of a transfer method of an LED chip in the embodiment of the present application;

FIG. 20 is a cross-sectional view of an electrode on a substrate according to an embodiment of the present disclosure;

FIG. 21A is a schematic structural diagram of two types of electrodes with a limiting groove according to an embodiment of the present disclosure;

FIG. 21B is a schematic structural diagram of three types of electrodes with a limiting groove according to an embodiment of the present disclosure;

fig. 22 is a flowchart of a transfer method of an LED chip in the embodiment of the present application;

fig. 23 is a schematic view illustrating a process of selectively placing an LED chip into a solution according to a transfer method of the LED chip in the embodiment of the present application;

fig. 24 is a schematic view showing a process of indiscriminately placing the LED chip in the solution in the transfer method according to the embodiment of the present application;

FIG. 25 is a schematic view showing a process of evaporating a solution according to the first and second embodiments of the present application for enhancing the bonding strength between an electrode and an LED chip;

FIG. 26 is a schematic view of a photolithography process according to a second embodiment of the present application for enhancing the bonding strength between the electrodes and the LED chip;

FIG. 27 is a schematic diagram of a process of removing a portion of photoresist according to a second embodiment of the present application for enhancing the bonding strength between an electrode and an LED chip;

FIG. 28 is a schematic diagram of a metal deposition process according to a second embodiment of the present application for enhancing the bonding strength between the electrodes and the LED chip;

FIG. 29 is a schematic view of a process of removing all photoresist according to a second embodiment of the present application for enhancing the bonding strength between the electrodes and the LED chip;

FIG. 30 is a schematic view of a process of removing all photoresist according to a second embodiment of the present application for enhancing the bonding strength between the electrodes and the LED chip;

FIG. 31 is a schematic diagram of a first-stage evaporation process of a third embodiment for enhancing the bonding strength between an electrode and an LED chip in the present application;

FIG. 32 is a schematic view of a third embodiment of a bonding process for enhancing the bonding strength between an electrode and an LED chip according to the present invention;

FIG. 33 is a schematic diagram of a fourth embodiment of an electroplating process for enhancing the bonding strength between an electrode and an LED chip in the present embodiment;

FIG. 34 is a schematic diagram of a process of evaporating a solution according to a first embodiment of the luminescent color conversion in the example of the present application;

FIG. 35 is a schematic illustration of a photolithography process according to a first embodiment of luminescence color conversion in an embodiment of the present application;

FIG. 36 is a schematic view of a photoresist removal process for a first embodiment of luminescent color conversion in an embodiment of the present application;

FIG. 37 is a schematic view of a metal deposition process of a first embodiment of luminescent color conversion in an embodiment of the present application;

FIG. 38 is a schematic illustration of a metal deposition process for a first version of luminescent color conversion in an embodiment of the present application;

FIG. 39 is a schematic diagram of a second stage evaporation process of a second embodiment of luminescence color conversion in an embodiment of the present application;

FIG. 40 is a schematic view of a process for disposing a light-converting material according to a second embodiment of the conversion of emission colors in the example of the present application;

fig. 41 is a process diagram of a third scheme of luminescent color conversion in the example of the present application.

Detailed Description

In order to make the technical problems, technical solutions and advantageous effects to be solved by the present application clearer, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.

It will be understood that when an element is referred to as being "secured to" or "disposed on" another element, it can be directly on the other element or be indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or be indirectly connected to the other element.

It will be understood that the terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like, refer to an orientation or positional relationship illustrated in the drawings for convenience in describing the present application and to simplify description, and do not indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and thus should not be construed as limiting the present application.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present application, "a plurality" means two or more, and "/" means "or" several "means one or more unless specifically limited otherwise.

In this embodiment, the LED chip is a nanoscale chip, and includes a chip main body and two chip electrodes disposed on the chip main body at intervals, where the two chip electrodes may be disposed at any position along the length direction of the chip main body, and optionally, the two chip electrodes are respectively wrapped at two ends of the chip main body, that is, the electrodes surround the outer side wall of the chip main body and are located at two ends of the chip main body.

In this embodiment, a plurality of electrode units are disposed on the substrate, and each electrode unit includes a plurality of substrate electrodes (two or three electrodes), the plurality of electrode units are disposed at intervals, and the plurality of substrate electrodes of the electrode units are also disposed at intervals. When the electrode unit includes two substrate electrodes (which can be classified into a first substrate electrode and a second substrate electrode), in a preferred embodiment of the present embodiment, a distance between two chip electrodes of the LED chip is greater than a minimum distance between two adjacent substrate electrodes, and a distance between two chip electrodes of the LED chip refers to the minimum distance between the two chip electrodes.

Referring to fig. 1, fig. 1 shows a type of LED chip (hereinafter referred to as a type a LED chip) 20 that may be used in the present application. The chip body of the LED chip 20 is a column structure, the horizontal direction in fig. 1 is the height direction (i.e. length direction) of the LED chip 20, and the vertical direction is the width direction thereof. Generally, its length should be greater than its width, and its shape may be a cylinder (i.e., a circular cross-section along the longitudinal direction), a rectangular parallelepiped, or other suitable shape. As shown in fig. 1, along the length direction of the chip body, there are a first chip electrode 1, a first semiconductor conductive layer 2, an active region 3, a second type semiconductor conductive layer 4, and a second chip electrode 5 in sequence, wherein one of the first semiconductor conductive layer 2 and the second type semiconductor conductive layer 4 is an n-type semiconductor conductive layer, the other is a p-type semiconductor conductive layer, and one of the first chip electrode 1 and the second chip electrode 5 is a positive electrode, and the other is a negative electrode. When the first chip electrode 1 and the second chip electrode 5 are connected to the positive (negative) electrode and the negative (positive) electrode of the power supply, respectively, the LED chip 20 is driven to emit light when a suitable voltage is applied. The insulating layer 6 is coated on the side surface of the LED pillar, and has the function of preventing the LED chip 20 from short-circuiting with the outside, and passivating the sidewall of the active layer, thereby improving the quantum efficiency. At this time, the minimum distance between the two chip electrodes 1, 5 of the LED chip refers to the distance between the right sidewall of the first chip electrode 1 and the left sidewall of the second chip electrode 5.

Referring to fig. 2, fig. 1 shows another type of LED chip (hereinafter referred to as "B-type LED chip") 20 that can be used in the present application, and the components denoted by reference numerals 1 to 5 are the same as the a-type LED chip, except that the cladding layer 7 is a special material having a color conversion function (e.g., a light conversion material) in addition to the functions of insulation and passivation, and the special material is made of a semiconductor with a specific forbidden band width and is formed in the LED chip manufacturing process.

Generally, the part between two chip electrodes of the LED chip 20 with a columnar structure is completely covered by the insulating layer 6, the first semiconductor conducting layer 2, the active region 3, the second type semiconductor conducting layer 4 and the insulating layer 6 constitute a chip body, the first chip electrode 1 and the second chip electrode 5 are wrapped at the periphery of the chip body in the length direction at intervals, the length of the typical first chip electrode 1 and the second chip electrode 5 in the width direction of the LED chip 20 is greater than or equal to the width of the chip body, so that when the LED chip 20 is horizontally arranged on a plane, the first chip electrode 1 and the second chip electrode 5 can be in contact with the plane. Optionally, the first chip electrode 1 and the second chip electrode 5 are respectively wrapped at two ends of the chip main body.

In one embodiment, the chip body is a cylinder, and the two chip electrodes 1 and 5 are arranged on the side surface of the cylinder at intervals. Generally, the two chip electrodes 1 and 5 have the same structure, the chip electrodes 1 and 5 have a circular ring structure, the outer surface of the chip electrodes 1 and 5 has a circular ring shape and is circumferentially disposed on the side surface of the chip body, and the difference between the outer diameter of the chip electrodes 1 and 5 and the radius of the chip body is greater than 0 and less than 3mm, that is, the radius of the outer surface of the chip electrode is defined as R, the radius of the chip body is R, and 0< R-R <3mm, it should be noted that 3mm is only a preferred example, and this is not a limitation here.

In one embodiment, the distance between the two chip electrodes 1, 5 refers to the minimum distance between the two chip electrodes 1, 5 on the side of the chip body; when both chip electrodes 1, 5 are arranged parallel to the bottom surface of the chip body, the distance between the two chip electrodes 1, 5 is the distance between the cross sections of the two chip electrodes 1, 5, or the distance between the center points of the two chip electrodes 1, 5. In one embodiment, two chip electrodes 1, 5 are respectively disposed at two ends of the chip main body, and each chip electrode 1, 5 covers a bottom surface of the chip main body and a portion of a side surface connected to the bottom surface.

In one embodiment, the distance between the two chip electrodes 1, 5 is equal to the difference between the distance between the two ends of the chip body and the width between the two chip electrodes 1, 5 (the width refers to the dimension of the LED chip 20 in the length direction).

In an embodiment, when the chip main body is a cylinder, the two chip electrodes 1 and 5 are disposed at two ends of the cylinder at intervals, and the distance between the chip electrodes 1 and 5 is equal to the distance between the two ends of the cylinder.

In one embodiment, the chip body is a cylinder, and the two chip electrodes 1 and 5 respectively coat the ends of the cylinder. In other embodiments, the two chip electrodes 1 and 5 may cover the middle portion of the cylindrical body except the end portions thereof.

In an embodiment, the chip main body is a prism, the two chip electrodes 1 and 5 are disposed at intervals on the side surfaces of the prism, each chip electrode 1 and 5 includes a plurality of chip sub-electrodes (not shown), the number of the chip sub-electrodes is equal to the number of the side edges of the prism, each chip sub-electrode is protruded on one side surface of the chip main body, and one of the chip electrodes 1 or 5 may form a corresponding annular array. It will be appreciated that the width of any side of the prism should be less than the minimum distance between two adjacent substrate electrodes (the width of this side can be considered as the side length of the intersection between the cross-section of the prism and the side). For example, the prism may be a triangular prism, a quadrangular prism, a pentagonal prism, or a hexagonal prism, which is not limited herein.

In a preferred embodiment, the prism body may be one of a regular triangular prism, a regular quadrangular prism, a regular pentagonal prism, or a regular hexagonal prism.

In another preferred embodiment, the shapes and sizes of the plurality of chip sub-electrodes are uniform, but in other embodiments, the shapes and sizes of the plurality of chip sub-electrodes may be uniform or non-uniform, and the sizes may be uniform or non-uniform, which is not limited herein.

In an embodiment, the chip body is a prism, and the distance between the two chip electrodes 1 and 5 may be the distance between the cross sections of the formed annular array. In one embodiment, the chip electrodes 1, 5 in the annular array respectively cover one bottom surface (end surface) of the chip main body.

According to the LED chip transfer method provided by the technical scheme, a solution method (or called a fluid self-assembly method) is used for transferring the LED chips, the LED chips are uniformly placed in the solution, the solution flows freely on the substrate of the back plate to drive the LED chips to move randomly, after the solution is evaporated, the LED chips with the columnar structures are transversely and randomly deposited on the substrate, and two chip electrodes can be in contact with substrate electrodes on the substrate to finish the transfer process. Therefore, the substrate electrodes should be designed such that the two chip electrodes of the LED chips fall on different substrate electrodes with the highest probability under the condition of random distribution of the LED chips.

In one embodiment, referring to fig. 3A to 6B, the following provides 4 possible electrode shape designs of the backplane, a plurality of electrode units are disposed at intervals on the first surface of the substrate 10, each electrode unit includes two types of substrate electrodes 11, 12 disposed at intervals and in a consistent structure, or three types of substrate electrodes 11, 12, 13 disposed at intervals and in a consistent structure, and a distance (i.e., a minimum distance) between each substrate electrode should be limited, where the distance between each substrate electrode refers to a distance of facing edges, and a distance between a right side of a white square frame of a first row of a first column and a left side of a diagonal square frame of the first row of a second column in fig. 3A is a minimum distance between two adjacent chip electrodes. It should be noted that the uniform structure described herein may refer to the uniform shape of the substrate electrodes, such as in one embodiment, the substrate electrodes 11, 12 are square, and in another embodiment, the substrate electrodes 11, 12, 13 have a circular cross section. Further preferably, the substrate electrodes may have the same size, for example, the cross sections of the substrate electrodes 11, 12, 13 are all circular, and the radii of the corresponding circles of the substrate electrodes 11, 12, 13 are the same, but in practical applications, the sizes of the substrate electrodes may be different, and this is not limited herein.

Referring to fig. 3A to 5B, in an embodiment, the substrate electrodes may include two types, including a first substrate electrode 11 and a second substrate electrode 12 that are disposed at an interval, the first substrate electrode 11 and the second substrate electrode 12 have substantially the same shape and structure, and a slight deviation is allowed without affecting performance, the first substrate electrode 11 and the second substrate electrode 12 on the substrate 10 are arranged in a longitudinally staggered manner, and the first substrate electrode 11 and the second substrate electrode 12 on the substrate 10 are also arranged in a laterally staggered manner, that is, the second substrate electrode 12 is adjacent to the first substrate electrode 11, and similarly, the first substrate electrode 11 is adjacent to the second substrate electrode 12. For another example, one second substrate electrode 12 is provided between two adjacent first substrate electrodes 11, and one first substrate electrode 11 is provided between two adjacent second substrate electrodes 12. As shown in fig. 3A, 3B, 4A, 4B.

In one embodiment, the first substrate electrodes 11 and the second substrate electrodes 12 are spaced apart, and the minimum distance between any two first substrate electrodes 11 is greater than the minimum distance between any two first substrate electrodes 11 and the second substrate electrodes 12.

A plurality of one type of substrate electrodes encloses one of the other type of substrate electrodes, as viewed across the first surface of the substrate 10, and the minimum distance between any two like substrate electrodes is greater than the minimum distance between any two dissimilar substrate electrodes.

Referring to fig. 5A to 6B, in one embodiment, the substrate electrodes include three types, including a first substrate electrode 11, a second substrate electrode 12, and a third substrate electrode 13, which are identical in structure, and any one of the first substrate electrode 11, the second substrate electrode 12, and the third substrate electrode 13 on the substrate is adjacent to the other two substrate electrodes, respectively, so that the first substrate electrode 11 is adjacent to the second substrate electrode 12 and the third substrate electrode 13, and is adjacent to the second substrate electrode 12 and the third substrate electrode 13 in the adjacent electrode units, that is, the second substrate electrode 12 and the third substrate electrode 13 are adjacent to the first substrate electrode 11; similarly, the first substrate electrode 11 and the third substrate electrode 13 are adjacent to the second substrate electrode 12, and the first substrate electrode 11 and the second substrate electrode 12 are adjacent to the third substrate electrode 13. A plurality of two types of substrate electrodes among them enclose one of the other substrate electrodes, as seen on the first surface of the entire substrate 10. For example, the second substrate electrode 12 and/or the third substrate electrode 13 are disposed between any two adjacent first substrate electrodes 11, the first substrate electrode 11 and/or the third substrate electrode 13 are disposed between any two adjacent second substrate electrodes 12, and the second substrate electrode 12 and/or the third substrate electrode 13 are disposed between any two adjacent third substrate electrodes 13, as shown in fig. 5A, 5B, 6A, and 6B.

The electrodes of the same type on the substrate 10 are short-circuited with each other through the electrode lines on the substrate 10, and different voltages can be applied between the electrodes of different types (such as the first substrate electrode 11 and the second substrate electrode 12) to form potential differences. If the two chip electrodes of the LED chip 20 are in contact with and electrically connected to different types of substrate electrodes, the two chip electrodes of the LED chip are lit up due to having a potential difference. Otherwise, if the two chip electrodes of the LED chip 20 fall on the same substrate electrode, the potential difference across it is 0 and will not be lit, so that this should be avoided as much as possible. Since the LED chips 20 are randomly oriented, appropriate driving circuits and driving signal timings should be matched in order to achieve effective driving of the LED chips 20, which will be described later. It should be noted that the cases described in fig. 3A to 6B are cases where the number of substrate electrode repetitions is large, and the actual number of substrate electrode repetitions should be designed with reference to the pixel area so that the area occupied by the entire substrate electrode coincides with the pixel area. It should be noted that the different types of substrate electrodes may be substrate electrodes to which the same voltage is not applied at the same time, that is, the different types of substrate electrodes are not applied with one voltage at the same time, or the different types of substrate electrodes are applied with the same voltage at different times.

Referring to fig. 3A and 3B, a first substrate electrode structure design is disclosed, which has two types of substrate electrodes, a first substrate electrode 11 filled with a pattern and a second substrate electrode 12 without filling, and the cross-sectional shape of each substrate electrode 11, 12 is square. The square substrate electrodes 11, 12 are closely spaced in a matrix form, leaving a spacing between the substrate electrodes 11, 12, and in one embodiment, the spacing between the first and second substrate electrodes 11, 12 (e.g., the distance between opposing sides of adjacent first and second substrate electrodes 11, 12) is uniform. Fig. 3B shows the situation after the LED chips 20 are randomly placed, the LED chips 20 without filling show an example of transfer failure, and the LED chips 20 with pattern filling show an example of transfer success.

According to the experiment, the ratio of the side length of the square to the length of the LED chip under the design of the substrate electrode, and the corresponding proportion of the LED chip 20 successfully transferred, are shown in the following table one:

table one:

it can be seen that the ratio of the side length of the square to the distance between the two chip electrodes of the LED chip 20 ranges: when the transfer rate is 0.6-1.2, the proportion of the successfully transferred LED chips exceeds 50 percent. In addition, with such substrate electrode design, when the minimum distance between the adjacent substrate electrodes is 0.01 to 0.1 times the side length of the square electrode, the proportion of successfully transferred LED chips can be further increased, and it should be noted that, if the distance between two chip electrodes of an LED chip 20 should be smaller than the sum of the side length of the square and the minimum distance between the first substrate electrode 11 and the second substrate electrode 12, it is possible to avoid short-circuiting two adjacent identical substrate electrodes 11/12 of one LED chip 20. In order to maximize the transfer success rate, the length of the LED chip is set to be basically equal to the side length of the square, so that the transfer success rate is better, and 64% of the transfer success rate can be obtained.

Referring to fig. 4A and 4B, a second substrate electrode structure design is disclosed, which has two types of substrate electrodes, a pattern-filled first substrate electrode 11 and an unfilled second substrate electrode 12, respectively, and the cross-sectional shape of each substrate electrode 11, 12 is an equilateral triangle. The pitch between the adjacent first substrate electrodes 11 and second substrate electrodes 12 is uniform, and similarly, the triangular substrate electrodes 11 and 12 are closely spaced, and a pitch is left between the substrate electrodes 11 and 12. Fig. 4B shows the transfer after the transfer of the LED chip. The LED chip 20 filled with the blank indicates an example of transfer failure, and the LED chip 20 filled with the pattern indicates an example of transfer success, where success refers to the fact that two chip electrodes of the LED chip 20 are respectively connected to two different types of substrate electrodes on the substrate, otherwise, the transfer is referred to as an example of failure.

According to the experiment, the ratio of the side length of the equilateral triangle to the length of the LED chip in the design of the substrate electrode, and the corresponding proportion of successfully transferred LED chips, are shown in the following table two:

table two:

as shown in fig. 4A and 4B, in the same row of electrodes, the bases of the same type of substrate electrodes (in this case, the side of the regular triangle parallel to the horizontal direction is taken as the base) are located on the same straight line, and as the bases of the first substrate electrodes 11 in one row are located on the same horizontal line, the bases of the second substrate electrodes 12 in the same row are located on the same horizontal line. Preferably, one side of the regular triangle corresponding to the first substrate electrode 11 in the electrode unit is opposite to and parallel to one side of the regular triangle corresponding to the second substrate electrode 12, and preferably, two sides of the adjacent regular triangle, which are close to the first substrate electrode 11 and the second substrate electrode 12, are opposite. If the range of the ratio of the side length of the regular triangle to the distance between the two chip electrodes of the LED chip 20 is: when the transfer rate is 0.4-0.7, the proportion of the successfully transferred LED chips exceeds 50%. In addition, in the substrate electrode design, the ratio of the minimum distance between the adjacent first substrate electrode 11 and the second substrate electrode 12 (the distance between two opposite parallel sides between two adjacent regular triangles) to the side length of the regular triangle is in the range: 0.005-0.05, the proportion of successfully transferred LED chips 20 can be further improved. In order to maximize the transfer success rate, the side length of the triangle is set to be about 0.55 times of the distance between the two chip electrodes of the LED chip 20, so that a better transfer success rate is achieved, about 61% of the LED chips 20 are successfully transferred onto the backplane, and it should be noted that success means that the two chip electrodes of the LED chip 20 are respectively connected to different types of substrate electrodes.

Referring to fig. 5A and 5B, a third substrate electrode structure design is disclosed, which includes three types of substrate electrodes, namely, a first substrate electrode 11, a second substrate electrode 12 and a third substrate electrode 13 filled with two different patterns, wherein the cross-sectional shape of each substrate electrode 11, 12, 13 is a regular hexagon. The regular hexagonal electrodes 11, 12, 13 are closely spaced and leave a spacing between the substrate electrodes 11, 12, 13, the spacing between adjacent substrate electrodes 11, 12, 13 being equal, which refers to the minimum distance between two adjacent substrate electrodes, as shown in fig. 5A, the distance between two opposing and parallel sides of adjacent first and second substrate electrodes 11, 12 being the minimum distance between adjacent substrate electrodes. Fig. 5B shows an example in which the LED chips 20 filled with blanks after the LED chips 20 are randomly placed indicate a transfer failure, and the LED chips 20 filled with patterns are an example in which the transfer is successful. According to the experiment, under the design of the substrate electrode, the ratio of the diameter of the inscribed circle of the regular hexagon to the length of the LED chip, and the corresponding proportion of the successfully transferred LED chip 20 refer to the following third table:

table three:

as can be seen, in any electrode unit, one side of the regular hexagon corresponding to the first substrate electrode 11 is opposite to and parallel to one side of the regular hexagon corresponding to the second substrate electrode 12, and the other side of the regular hexagon corresponding to the first substrate electrode 11 is opposite to and parallel to one side of the regular hexagon corresponding to the third substrate electrode 13, preferably opposite to and parallel to each other. The ratio range of the diameter of the inscribed circle of the regular hexagon to the distance between the two chip electrodes of the LED chip 20 is: when the transfer rate is 0.2-1.8, the proportion of the successfully transferred LED chips exceeds 60%. In addition, under the design of the substrate electrodes, the ratio range of the minimum distance between the adjacent substrate electrodes and the side length of the regular hexagonal electrode is as follows: 0.05-0.2, the proportion of successfully transferred LED chips 20 can be further increased. In order to maximize the success rate of the transfer, when the optimal value of the distance between the two chip electrodes of the LED chip 20 is 1.732 times of the side length of the regular hexagon, or the diameters of the two chip electrodes of the LED chip 20 and the inscribed circle of the regular hexagon are substantially equal, there is a better success rate of the transfer, and 98% of the chips can be successfully transferred at this time.

Referring to fig. 6A and 6B, a fourth substrate electrode design is disclosed, which has three types of substrate electrodes, a first substrate electrode 11, a second substrate electrode 12 and a third substrate electrode 13 filled with two different patterns, wherein the cross-sectional shape of each substrate electrode 11, 12, 13 is circular. The circular electrodes 11, 12, 13 are closely spaced, and a distance is left between the electrodes 11, 12, 13, the distance between the adjacent substrate electrodes is equal, the distance refers to a difference between a distance between centers of circles corresponding to the adjacent two substrate electrodes and a radius of the two circles (for example, the distance between the centers of the adjacent first substrate electrode 11 and second substrate electrode 12 is subtracted by the radius of the two circles, respectively, and the obtained difference is the distance), that is, the minimum distance between the two adjacent substrate electrodes. Fig. 6B shows an example in which the LED chips 20 filled with blanks after the LED chips 20 are randomly placed indicate a transfer failure, and the LED chips 20 filled with patterns are an example in which the transfer is successful. According to the experiment, the ratio of the diameter of the circle to the length of the LED chip for such a substrate electrode design corresponds to the ratio of successfully transferred LED chips 20 as shown in the following table four:

table four:

it can be seen that the ratio of the diameter of the circle to the distance between the two chip electrodes of the LED chip 20 ranges from: when the transfer rate is 0.6-1.8, the proportion of the successfully transferred LED chips exceeds 50%. In addition, in the design of the substrate electrodes, the ratio of the minimum distance between adjacent substrate electrodes to the diameter of the circular electrode is in the range: 0.01-0.1, the proportion of successfully transferred LED chips can be further improved. While, in order to maximize the transfer success rate, the transfer success rate is better when the two chip electrodes of the LED chip 20 are disposed substantially equal to the diameter of the circular electrode, at which time 75% of the chips can be transferred successfully.

Based on the electrode pattern of any of the above-described modes, the LED chip 20 is transferred onto the substrate 10 and then electrically contacted with the substrate electrode on the substrate 10, thereby constituting each pixel structure in the back sheet of the LED display device.

Referring to fig. 7, in some embodiments, the pixel structure includes a substrate 10, a plurality of electrode units, and a plurality of LED chips 20, where the electrode units are disposed on a first surface of the substrate 10 at intervals, and a distance between two chip electrodes of each LED chip 20 is greater than a minimum distance between any two adjacent first substrate electrodes 11 and second substrate electrodes 12, where two chip electrodes of one LED chip 20 are respectively connected to the first substrate electrode 11 and the second substrate electrode 12 of one electrode unit, or one chip electrode of one LED chip 20 is connected to the first substrate electrode 11 of one electrode unit, and another chip electrode of one LED chip 20 is connected to the second substrate electrode 12 of another electrode unit adjacent to the electrode unit.

Generally, the minimum spacing between adjacent electrode units is substantially equal to the minimum distance between the first substrate electrode 11 and the second substrate electrode 12 between the electrode units, and a slight deviation may be allowed without affecting the performance. The substrate electrodes on the whole pixel structure are compactly and tidily arranged, and the transfer efficiency of the LED chip is improved.

In the pixel structure, two substrate electrodes 11 and 12 are arranged on the substrate 10 at intervals, which is beneficial to uniform and effective transfer of the LED chips 20, so that the manufactured lamp panel and the display device can emit light uniformly; in addition, the two substrate electrodes 11 and 12 do not need to distinguish the positive electrode from the negative electrode, after the LED chip 20 is randomly connected to the two substrate electrodes 11 and 12, only a driving power supply with a proper time sequence needs to be set on the two substrate electrodes 11 and 12, so that a potential difference exists between the two substrate electrodes 11 and 12, and the LED chip 20 randomly connected to the two substrate electrodes 11 and 12 can be lightened, thereby improving the transfer success ratio; meanwhile, the LED chips 20 are lighted in a time-sharing sequence, so that the service life of the LED chips can be prolonged, and the loss can be reduced.

Referring to fig. 8, in another embodiment, the electrode unit further includes at least one third substrate electrode 13, the first substrate electrode 11, the second substrate electrode 12, and the third substrate electrode 13 are disposed at intervals, and the third substrate electrode 13 has a structure substantially identical to that of the first substrate electrode 11, so that a fine deviation can be allowed without affecting performance. In this way, when the electrode unit has three types of substrate electrodes, two chip electrodes of the LED chip 20 are connected to any two of the first substrate electrode 11, the second substrate electrode 12, and the third substrate electrode 13, respectively.

In general, the minimum distances among the first substrate electrode 11, the second substrate electrode 12, and the third substrate electrode 13 in the electrode unit are substantially uniform, and a fine deviation can be allowed without affecting the performance; the minimum pitch substrate between adjacent electrode units is equal to the minimum distance between the first substrate electrode 11 and the second substrate electrode 12 between the electrode units, and a slight deviation can be allowed without affecting the performance. The arrangement of the substrate electrodes on the whole pixel structure is compact and neat, the utilization rate of the substrate 10 is favorably improved, and the transfer success rate of the LED chips is improved.

In the pixel structure, the three types of substrate electrodes 11, 12 and 13 are arranged on the substrate 10 at intervals, so that the LED chips 20 which are further uniformly and effectively transferred are facilitated, and the manufactured lamp panel and the display device can uniformly emit light; in addition, the three types of substrate electrodes 11, 12 and 13 do not need to be distinguished from each other in terms of positive and negative electrodes, after the LED chip 20 is randomly connected to any two types of substrate electrodes (11, 12)/(12, 13)/(13 and 11), only a driving power supply with a proper timing sequence needs to be set on the two types of substrate electrodes (11, 12)/(12, 13)/(13 and 11), so that potential differences exist on the two types of substrate electrodes (11, 12)/(12, 13)/(13 and 11), the LED chips 20 randomly connected to the two types of substrate electrodes (11, 12)/(12, 13)/(13 and 11) can be lightened, and the transfer success ratio is further improved; meanwhile, the LED chips 20 are sequentially turned on in three components, so that the life span thereof can be further increased and the loss can be reduced.

Referring to fig. 7, the substrate 10 may be glass, crystal, sapphire substrate, plastic, or flexible polymer film, but the disclosure is not limited thereto. The area of the substrate 10 according to the embodiment may vary according to the area of the substrate electrodes disposed in the first surface of the substrate 10 and the size and number of the LED chips 20 disposed between the respective substrate electrodes, which will be described later.

A driving circuit 30 for driving the LED chip 20 may be fabricated on the substrate 10, and in the pixel structure having the two types of substrate electrodes, the driving circuit 30 is electrically connected to the first substrate electrode 11 and the second substrate electrode 12; referring to fig. 8, in the pixel structure having three types of substrate electrodes, the driving circuit 30 is electrically connected to the first substrate electrode 11, the second substrate electrode 12 and the third substrate electrode 13.

Generally, the driving circuit 30 includes a series of components, such as Thin Film Transistors (TFTs), capacitors, etc., and the driving circuit 30 also includes metal lines between the components, and an interlayer insulating layer 102 is disposed above the driving circuit 30, and certain positions are connected to the electrode units above the driving circuit through the metal vias 50.

In one embodiment, referring to fig. 7 and 8, an upper insulating layer 101 is covered between adjacent substrate electrodes 11 and 12, so that the upper surface of the entire substrate 10 is in a planar state without height difference, which is beneficial to improving the transfer success rate of the LED chip 20. It can be understood that the upper surface of the substrate 10 presents a planar state, which can make the width (referred to as the dimension in the LED chip width direction) of the LED chip 20 of the cylinder and the LED chip 20 whose side surface (when the chip body is a prism) is smaller than the minimum distance between the two adjacent substrate electrodes (11, 12)/(12, 13)/(13, 11), when the chip electrode falls on the gap between the two adjacent substrate electrodes (11, 12)/(12, 13)/(13, 11), will not cause the two adjacent substrate electrodes (11, 12)/(12, 13)/(13, 11) to short.

In an embodiment, when the LED chip 20 is placed on the substrate 10, the LED chip is horizontally placed on the uppermost surface of the pixel structure, and fig. 7 and a cross-sectional view showing the pixel structure after the LED chip 20 is placed, since the upper surface of the substrate 10 is a plane, the position of the LED chip 20 is relatively regular, and the situation that the LED chip 20 is tilted and the like does not occur, and is relatively regular.

Referring to fig. 9, in one embodiment, the driving circuit 30 is adapted to a pixel structure having two types of substrate electrodes, and includes: the driving circuit comprises a first driving transistor M1-1, a second driving transistor M1-2, a third driving transistor M2-1, a fourth driving transistor M2-2, a first capacitor C1, a second capacitor C2, power lines P1 and P2 for connecting a power supply, a Data line Data for connecting a Data signal and a scanning line Scan for connecting a scanning signal.

In the present embodiment, a first pole of the first driving transistor M1-1 is electrically connected to the first power line P1, and a second pole of the first driving transistor M1-1 is electrically connected to at least one first substrate electrode 11; a first pole of the second driving transistor M1-2 is electrically connected to the second power line P2, and a second pole of the second driving transistor M1-2 is electrically connected to the at least one second substrate electrode 12; a first pole of the third driving transistor M2-1 is electrically connected to the control pole of the first driving transistor M1-1, a second pole of the third driving transistor M2-1 is electrically connected to the Data line Data, and a control pole of the third driving transistor M2-1 is electrically connected to the Scan line Scan; a first pole of the fourth driving transistor M2-2 is electrically connected to the control pole of the second driving transistor M1-2, a second pole of the fourth driving transistor M2-2 is electrically connected to the Data line Data, and a control pole of the fourth driving transistor M2-2 is electrically connected to the Scan line Scan.

Referring to fig. 10, in another embodiment, suitable for a pixel structure having three types of substrate electrodes, the driving circuit 30 includes a first driving transistor M1-1, a second driving transistor M1-2, a third driving transistor M1-3, a fourth driving transistor M2-1, a fifth driving transistor M2-2, a sixth driving transistor M2-3, a first capacitor C1, a second capacitor C2, a third capacitor C3, power lines P1, P2, and P3 for connecting a power supply, a Data line for connecting a Data signal, and a Scan line Scan for connecting a Scan signal.

A first pole of the first driving transistor M1-1 is electrically connected to the first power line P1, and a second pole of the first driving transistor M1-1 is electrically connected to at least one first substrate electrode 11; a first pole of the second driving transistor M1-2 is electrically connected to the second power line P2, and a second pole of the second driving transistor M1-2 is electrically connected to the at least one second substrate electrode 12; a first pole of the third driving transistor M1-3 is electrically connected to the third power line P3, and a second pole of the third driving transistor M1-3 is electrically connected to at least one third substrate electrode 13; a first pole of the fourth driving transistor M2-1 is electrically connected to the control pole of the first driving transistor M1-1, a second pole of the fourth driving transistor M2-1 is electrically connected to the Data line Data, and a control pole of the fourth driving transistor M2-1 is electrically connected to the Scan line Scan; a first pole of the fifth driving transistor M2-2 is electrically connected to the control pole of the second driving transistor M1-2, a second pole of the fifth driving transistor M2-2 is electrically connected to the Data line Data, and the control pole of the fifth driving transistor M2-2 is electrically connected to the Scan line Scan; a first pole of the sixth driving transistor M2-3 is electrically connected to the control pole of the third driving transistor M1-3, a second pole of the sixth driving transistor M2-3 is electrically connected to the Data line Data, and the control pole of the sixth driving transistor M2-3 is electrically connected to the Scan line Scan; the first capacitor C1, the second capacitor C2, and the third capacitor C3 are connected between the gate and the first electrode of the first driving transistor M1-1, the gate and the first electrode of the second driving transistor M1-2, and the gate and the first electrode of the third driving transistor M1-3, respectively.

In the two embodiments of the driving circuit 30, the first capacitor C1, the second capacitor C2, and the third capacitor C3 are used for charging and discharging to drive the driving transistor to be connected to be turned on and off; the first pole, the second pole and the control pole of the transistor are respectively a source electrode, a drain electrode and a grid electrode of the transistor. The transistor is generally a TFT device, such as an n-type mos transistor, a p-type mos transistor, an insulated gate bipolar transistor or the like.

Referring to fig. 3A to 4B, fig. 11 and fig. 13B, in some embodiments, the pixel structure having two types of substrate electrodes includes a plurality of first substrate electrodes 11, a plurality of second substrate electrodes 12, first substrate electrode lines 41 and second substrate electrode lines 42, wherein the first substrate electrode lines 41 connect the plurality of first substrate electrodes 11 to each other through metal vias 50; the second substrate electrode lines 42 connect the plurality of second substrate electrodes 12 to each other through the metal vias 50; the metal via 50 penetrates through the intermediate insulating layer 102, and since one of the first substrate electrodes 11 and the second substrate electrodes 12 is surrounded by one of the other substrate electrodes, the two chip electrodes of the LED chip 20 are in electrical contact with the different first substrate electrodes 11 and second substrate electrodes 12 respectively with the highest probability under the condition that the LED chips 20 are randomly distributed.

Referring to fig. 5A to 6B, fig. 12 and fig. 14B, in some embodiments, the pixel structure with three types of substrate electrodes includes a plurality of first substrate electrodes 11, a plurality of second substrate electrodes 12, a plurality of third substrate electrodes 13, first substrate electrode lines 41, second substrate electrode lines 42 and third substrate electrode lines 43, wherein the first substrate electrode lines 41 connect the plurality of first substrate electrodes 11 to each other through metal vias 50; the second substrate electrode lines 42 connect the plurality of second substrate electrodes 12 to each other through the metal vias 50; the third substrate electrode lines 43 connect the plurality of third substrate electrodes 13 to each other through the metal vias 50; the metal via 50 penetrates through the intermediate insulating layer 102, and since one of the first substrate electrodes 11, the second substrate electrodes 12, and the third substrate electrodes 13 is surrounded by a plurality of two substrate electrodes, the two chip electrodes of the LED chip 20 have the highest probability of being electrically contacted with the different first substrate electrodes 11, second substrate electrodes 12, and third substrate electrodes 13 when the LED chips 20 are randomly distributed.

Referring to fig. 12, the structure of the upper surface of the substrate 10 can be considered as having an upper layer, a middle layer and a lower layer, the upper layer is an electrode layer of an electrode region (electrode unit), and the first substrate electrode 11, the second substrate electrode 12 and the third substrate electrode 13 are electrically isolated from each other by the upper insulating layer 101; the lower layer is an electrode line layer provided with gold fingers, the first substrate electrode lines 41, the second substrate electrode lines 42 and the third substrate electrode lines 43, and the gold fingers are electrically isolated among the first substrate electrode lines 41, the second substrate electrode lines 42 and the third substrate electrode lines 43 by a lower insulating layer (namely, a second insulating layer) 103; the intermediate layer is a via layer provided with metal vias 50 electrically connecting the electrode unit and the electrode line, respectively, and the respective metal vias 50 are electrically isolated from each other by an intermediate insulating layer (first insulating layer) 102. The chip electrodes of the LED chip 20 are sequentially connected to the driving circuit 30 through the substrate electrodes 11, 12, 13, the metal vias 50, and the electrode lines 41, 42 in a one-to-one correspondence.

An upper and lower layer structure of the pixel structure is illustrated; for example, in a pixel structure having two types of square electrodes, fig. 13A shows the upper layer (electrode layer) surface of the structure, fig. 13B shows the lower layer (electrode layer) bottom surface of the structure, and black circles are drawn in the figure to represent the metal vias 50. In fig. 13A, 13B, the patterns shown correspond up and down in the physical structure, and in fig. 13A, each substrate electrode 11, 12 is connected to at least one metal via 50; in fig. 13B, the first substrate electrode 11 and the second substrate electrode 12 are connected together by the first substrate electrode line 41 and the second substrate electrode line 42, respectively, through the metal via 50, form a short circuit, and are led out to the drive circuit 30.

For example, in a pixel structure having three types of regular hexagonal electrodes, fig. 14A shows the upper layer (electrode layer) surface of the structure, fig. 14B shows the lower layer (electrode layer) bottom surface of the structure, and black circles are drawn in the drawing to represent the metal vias 50. In fig. 14A, 14B, the patterns shown correspond up and down in the physical structure, and in fig. 14A, each substrate electrode 11, 12, 13 is connected to at least one metal via 50. In fig. 14B, the first substrate electrode 11, the second substrate electrode 12, and the third substrate electrode 13 are connected together by the first substrate electrode line 41, the second substrate electrode line 42, and the third substrate electrode line 43, respectively, through the metal via 50, form a short circuit, and are drawn out to the driving circuit 30.

In addition, in fig. 13A to 14B, since the regions illustrated in the respective drawings are positions where the electrodes of the respective types of substrates are disposed, the transfer of the LED chip 20 also occurs mainly in this region, and thus this region can be defined as an electrode region. Generally, the related embodiments are described with one electrode area corresponding to one electrode unit.

In one embodiment, in an actual pixel structure, the region (or TFT region) where the driving circuit 30 is disposed and the electrode unit may be separately disposed side by side. As shown in fig. 15, the pixel structure is a pixel structure of an RGB (red, green, blue) pixel, and the pixel includes three electrode units 1, 2, and 3 capable of emitting different colors (RGB) respectively. In this pixel structure, the driving circuit 30 may be a single layer design, or a metal or semiconductor device, and therefore, in the region where one pixel is located on the upper surface of the substrate 10, the three electrode units 1, 2, and 3 and the three driving circuits 30 are respectively located in the three corresponding electrode regions 1, 2, and 3, and the region where the driving circuit 30 is located may be located in a portion not occupied by the electrode units 1, 2, and 3, so that the driving circuit 30 is located on one side of the electrode units 1, 2, and 3.

In another embodiment, the region where the driving circuit 30 is disposed and the electrode unit may also be in a stacked form. As shown in fig. 11 and 12, the driving circuit 30 is located below the electrode layers ( electrode units 1, 2, and 3 in fig. 16), and the electrode line layer is located above the driving circuit 30 and in contact with the driving circuit 30 between the electrode layers. The top view of the stacked structure is shown in fig. 16, which is a region where a pixel is located, and the three electrode regions 1, 2, and 3 respectively include three electrode units 1, 2, and 3 capable of emitting different colors (RGB). Since the projection of the area (layer) of the driving circuit 30 and the projection of the electrode area (layer) in the direction perpendicular to the substrate 10 can be overlapped, the backplane formed by the pixel structure can place more light-emitting areas in a unit area, and higher pixel density is realized. The stacked structure may save space, achieve higher device density, and also transfer a greater number of chips in the same area of the display device backplane than the split design shown in fig. 15.

In addition, the stacked pixel structure, as shown in fig. 11 and 12, requires electrical connection between the driving circuit 30 and the first substrate electrode 11, the second substrate electrode 12 and the third substrate electrode 13, and for this reason, a special upper insulating layer 101, a special middle insulating layer 102 and a special lower insulating layer 103 need to be fabricated therebetween, and the growth rate of the upper insulating layer 101, the middle insulating layer 102 and the special lower insulating layer 103 can be 50% of that of the conventional insulating layer, and the growth temperature is 30 ℃ higher than that of the conventional insulating layer. Also, the total thickness of the upper insulating layer 101, the middle insulating layer 102 and the lower insulating layer 103 is not less than 100nm, and preferably not more than 2000nm, because considering that too thin thicknesses of the upper insulating layer 101, the middle insulating layer 102 and the lower insulating layer 103 may cause poor insulating effect, leakage may be easy, and too thick thicknesses of the upper insulating layer 101, the middle insulating layer 102 and the lower insulating layer 103 may make deposition of the metal via 50 difficult. In the stacked pixel structure, the driving circuit 30 layer has a plurality of TFT device structures having heights different from those of the non-TFT device portions, and the thicknesses of the upper insulating layer 101, the middle insulating layer 102, and the lower insulating layer 103 should compensate for the height difference therebetween so that the upper electrode metals are in the same plane.

In some embodiments, the width of the space between two adjacent substrate electrodes (11, 12)/(12, 13)/(13, 11) is 0.005 times to 0.2 times the length of a side (e.g., square, regular triangle) or a diameter (e.g., inscribed circle, circle of regular hexagon) of the shape. In addition, please refer to the above embodiments for the shapes and the related sizes of the substrate electrodes of the pixel structure, which are not described herein again.

Referring to fig. 9, in some embodiments, the present application further provides a pixel structure driving method, including:

step one, respectively inputting a scanning signal and a data signal to the electrode unit to carry out addressing.

And step two, providing a current source to the plurality of electrode units, wherein a positive current is sequentially provided to one of the first substrate electrode 11 and the second substrate electrode 12, and a negative current is sequentially provided to the other, so as to sequentially light the LED chip 20 connected between the first substrate electrode 11 and the second substrate electrode 12.

It is understood that, in this embodiment, a pixel structure having two types of substrate electrodes is applicable, the Scan line Scan and the Data line Data input a Scan signal and a Data signal, respectively, and the first power line P1 and the second power line P2 are connected to two current sources, respectively. The transistors M1-1/2, M2-1/2 and the capacitor C1/2 constitute a three 2T (transistor) 1C (capacitor) driver circuit 30. The LED chips 20 between the first substrate electrode 11 and the second substrate electrode 12 are randomly arranged, and the LED chips 20 with different polarities exist between different substrate electrodes.

It is assumed that the LED chip 20 between the first substrate electrode 11 and the second substrate electrode 12 includes D1, D2. Fig. 17 is a timing chart of the currents of the first power line P1 and the second power line P2. In this example, each cycle is divided into three phases. The first phase is addressing, in which neither the first power line P1 nor the second power line P2 has current, so that the Scan line Scan and the Data line Data perform addressing. In the last two stages, the first power line P1 and the second power line P2 alternately serve as current outflow ends, and the other serves as a current inflow end, so that the current outflow end is set to be a constant current output, the total current of the operation of the LED chips 20 is determined, and the total current is uniformly distributed among the LED chips 20 connected in parallel. Since the current is proportional to the brightness, the total brightness is controlled when the total current is controlled, and the gray scale of the display can be controlled.

For example, in the second phase, the first power line P1 is a current outflow terminal, the second power line P2 is a current inflow terminal, and the current flows through the LED chip D1 having its anode connected to the first power line P1, and the total current controls the total brightness of the LED chip D1.

Referring to fig. 10, in other embodiments, a method for driving a pixel structure is further provided, including:

step one, respectively inputting a scanning signal and a data signal to the electrode unit to carry out addressing.

And step two, providing a current source to the plurality of electrode units, wherein a positive current is sequentially provided to one of the first substrate electrode 11, the second substrate electrode 12 and the third substrate electrode 13, and a negative current is sequentially provided to the other two of the first substrate electrode 11, the second substrate electrode 12 and the third substrate electrode 13, so as to sequentially light up the LED chip 20 connected between the first substrate electrode 11 and the second substrate electrode 12, the LED chip 20 connected between the first substrate electrode 11 and the third substrate electrode 132, and the LED chip 20 connected between the second substrate electrode 12 and the third substrate electrode 13.

It is to be understood that, in this embodiment, a pixel structure having three types of substrate electrodes is applied, and the Scan line Scan and the Data line Data input a Scan signal and a Data signal, respectively. The first power line P1, the second power line P2, and the third power line P3 are connected to three current sources, respectively. The transistors M1-1/2/3, M2-1/2/3 and the capacitors C1/2/3 form three 2T1C driving circuits 30. The LED chips 20 are randomly arranged among the first substrate electrode 11, the second substrate electrode 12 and the third substrate electrode 13, and two chip electrodes of the LED chips 20 are respectively connected to different types of substrate electrodes.

Referring to fig. 10, it is assumed that the LED chip 20 between the first substrate electrode 11, the second substrate electrode 12 and the third substrate electrode 13 includes D1, D2, D3, D4, D5 and D6. Fig. 18 shows a current timing diagram of the first power line P1, the second power line P2, and the third power line P3. In this example, each cycle is divided into four phases. The first phase is addressing, and at this time, no current flows through the first power line P1, the second power line P2 and the third power line P3, so that the Scan line Scan and the Data line Data perform addressing. In the last three stages, the first power line P1, the second power line P2 and the third power line P3 alternately serve as current outflow ends, and the other two power lines serve as current inflow ends to set the current outflow ends to be constant current output, so that the total current of the operation of the LED chips 20 is determined, and the total current is uniformly distributed among the LED chips 20 connected in parallel. Since the current is proportional to the brightness, the total brightness is controlled when the total current is controlled, and the gray scale of the display can be controlled.

For example, in the second phase, the first power line P1 is a current outflow terminal, the second power line P2 and the third power line P3 are current inflow terminals, and when the current flows through the LED chips D1 and D3 with anodes connected to the first power line P1, the total current controls the total brightness of the LED chips D1 and D3.

It should be noted that the high (level) voltage on the Data line Data should be higher than the peak voltage of the power lines P1, P2, P3, and the high (level) voltage on the Scan line Scan should be higher than the high (level) voltage on the Data line Data to ensure the normal operation of the circuit.

In the driving method of the pixel structure, the pixel structure comprises two or three types of substrate electrodes, and no fixed positive and negative electrodes are arranged, so that after the LED chips 20 are randomly connected to the two types of substrate electrodes, only positive currents are required to be sequentially provided on the two/three types of substrate electrodes, potential difference exists on the two types of substrate electrodes, the LED chips 20 randomly connected to the two types of substrate electrodes can be lightened, the effective utilization rate of the LED chips 20 transferred to the substrate 10 is greatly improved, and the transfer success ratio is improved; meanwhile, the LED chips 20 are lighted in a time-sharing sequence, so that the service life of the LED chips can be prolonged, and the loss can be reduced.

The application also provides a lamp panel and a display device, wherein the lamp panel comprises the pixel structure; the display device comprises the lamp panel.

In addition, the application also provides a transfer method of the LED chip. It should be noted that, in each embodiment of the transfer method of the LED chip, the electrode unit includes three types of substrate electrodes as an example, and the electrode unit includes two types of substrate electrodes is substantially similar to the embodiment including three types of substrate electrodes, and therefore, the description is omitted.

Referring to fig. 19 in combination with fig. 1 to 18, in a first embodiment: the transfer method of the LED chip 20 includes:

step S110, putting a solution mixed with an LED chip into a substrate, wherein the substrate is provided with a plurality of electrode units, each electrode unit comprises a plurality of substrate electrodes, each LED chip comprises a chip main body and two chip electrodes arranged on the chip main body at intervals, and the distance between the two chip electrodes of each LED chip is larger than the minimum distance between any two adjacent substrate electrodes.

Step S130, heating to evaporate the solution, so that the LED chip is placed on the substrate.

The transferring method of the LED chip 20 is suitable for transferring the LED chip 20 to the substrate 10 having the two types of substrate electrodes, please refer to fig. 3A to 4B; the transfer to the substrate 10 of the above-described three types of substrate electrodes is also applicable, see fig. 5A to 6B.

Wherein, the solution can be one or at least one of deionized water, toluene, xylene, methanol, ethanol, isopropanol and the like. It can be understood that, the solution mixed with the LED chips 20 is placed on the substrate 10 provided with the substrate electrodes arranged at intervals, the solution flows freely on the substrate 10 to drive the LED chips 20 to move randomly, after the solution is evaporated, the LED chips 20 are deposited on the substrate 10, and the structure and the distance of the substrate electrodes on the substrate 10 are consistent, so that the LED chips can be almost uniformly distributed, and the two chip electrodes of the LED chips 20 with the highest probability fall on different substrate electrodes and are electrically contacted, thereby completing the transfer process.

Referring to fig. 20, in some embodiments, a pair of limiting grooves 60 may be formed between the first substrate electrode 11 and the second substrate electrode 12, between the second substrate electrode 12 and the third substrate electrode 13, and between the third substrate electrode 13 and the first substrate electrode 11, in the adjacent substrate electrodes, from the middle of one of the substrate electrodes to the middle of the other substrate electrode; specifically, the pair of limiting grooves 60 is formed in pairs on two adjacent substrate electrodes, and after the pair of limiting grooves 60 is communicated, the pair of limiting grooves extends from the surface of one of the substrate electrodes to the surface of the other substrate electrode. It is understood that the central portion of the substrate electrode refers to other positions except for the edge of the substrate electrode (as shown in fig. 20, the area surrounded by two side edges connected to one side edge of the upper surface of the first substrate electrode 11 is the central portion, and the upper surface refers to the surface of the first substrate electrode 11 contacting with the LED chip 20). The pair of stopper grooves 60 penetrates the upper insulating layer 101, which is a filling layer between the substrate electrodes. Because the limiting groove pairs 60 form potential energy low points, the LED chip 20 has higher probability of falling into the limiting groove pairs 60, and the success rate of the LED chip 20 in the transfer process is increased under the traction of the limiting groove pairs 60.

Referring to fig. 21A and 21B, two examples of the electrodes with square cross-section and regular hexagonal cross-section are shown. It can be understood that the pair of limiting grooves 60 is formed by communicating the open grooves respectively formed on the two adjacent substrate electrodes; the direction of each pair of slots should be aligned; in each pair of slots, the ratio of the lengths of the two slots is between 0.5 and 2 (for example, the slot pair comprises a first slot and a corresponding second slot, and the ratio of the length of the first slot to the length of the second slot can be 0.5 to 2); and, the width of each slot is adapted to, such as coincident with, the width of the LED chip 20; the sum of the length of the pair of limiting grooves 60 and the distance between the two corresponding adjacent substrate electrodes should be 1.05 to 1.3 times the length of the LED chip 20. In addition, the distance between the position of each notch and the adjacent substrate electrode side is not less than 2 times the width of the LED chip 20.

In another embodiment, two adjacent substrate electrodes may be respectively provided with a groove, the two grooves have the same direction, the notches are opposite, the two grooves form a limiting groove, and the structure of the limiting groove may be the same as that of the above-mentioned pair of grooves, which is not described herein again.

Referring to fig. 22, in some embodiments, before or while the step S110 is executed, the transferring method further includes a step S120: and a step of disturbing the solution to connect at least one LED chip 20 to both substrate electrodes in one electrode unit. It will be appreciated that disturbing the solution may result in a more uniform distribution of the LED chips 20 over the surface of the substrate 10; further, the LED chip 20 may have a greater probability of falling into the pair of stopper grooves 60. In step S120, for example, the perturbation duration is 10S to 600S.

Specifically, the manner of disturbing the solution includes: one or more of shaking the solution, applying a magnetic field to the solution (using magnetic force to move the LED chip 20), applying a shock wave (such as sound waves) to the solution, and agitating the solution.

Referring to fig. 23, in some embodiments, the substrate 10 has a plurality of regions, each region corresponding to an electrode unit, and the step S110 of putting the solution mixed with the plurality of LED chips into the substrate includes putting the solution into each region respectively. Certainly, each region may correspond to two or three electrode units, so as to directly and respectively put the solution into the region of one RGB pixel point.

In this manner, the solution may be selectively placed on the substrate 10, such as by printing, onto the substrate 10 in areas where there are substrate electrodes. Since the other region does not need the LED chip 20, the solution is selectively placed, and the number of the LED chips 20 can be saved. If this is done, some structure for restricting the flow of the solution can be provided near the electrode regions on the substrate 10, such as a raised edge for restricting the flow of the solution along the periphery of each electrode region, so that the solution does not easily flow to an undesired place to assist the transfer.

Referring to fig. 24, in another embodiment, the step S110 of putting the solution mixed with the LED chips into the substrate includes: a plurality of electrode units are positioned in the same area, and a solution is put into the area. In this way, the solution can be deposited indifferently onto the substrate 10, filling the area of the substrate 10 with the solution, and the substrate 10 is completely immersed in the solution, which has the advantage that the transfer can be carried out relatively simply without the need for a printing process. In this embodiment, some structures for restricting the solution flow may be disposed near the electrode regions on the substrate 10, such as a raised edge for restricting the solution flow along the periphery of each electrode region, so that the LED chips 20 in the solution do not easily flow to a position outside the electrode regions to assist the transfer.

After the transfer process of the LED chip 20 is completed, the solution is evaporated to dryness. At this time, only weak connection exists between the LED chip 20 and the first, second, and third substrate electrodes 11, 12, and 13, the contact resistance has randomness, and the contact resistance of a part of the LED chip 20 may be large, which may cause non-uniformity of the entire display. Meanwhile, since there is only a weak connection between the LED chip 20 and the substrate 10, if the substrate 10 is moved, the LED chip 20 may be shifted, the transfer effect may be damaged, and the transfer yield may be reduced. Therefore, in order to solve this problem, a bonding method that intensively strengthens the connection strength of the LED chip 20 and the substrate electrode on the substrate 10 is proposed below, and thus a bonded LED chip can be obtained.

It should be noted that, in each embodiment of the bonding method for the LED chip, the electrode unit includes three types of substrate electrodes as an example, and the electrode unit includes two types of substrate electrodes is substantially similar to the embodiment including three types of substrate electrodes, and therefore, the description is omitted.

Referring to fig. 25, the first solution: in step S110, a solution mixed with a plurality of LED chips is put into the substrate 10, a photoresist is mixed into the solution, and after the solution is evaporated to be dry, the bonded LED chip 20 placed on the substrate 10 is covered with a layer of photoresist (i.e., a photoresist layer) 104. Due to the photoresist layer 104, the position of the LED chip 20 is fixed and not shifted by the movement of the substrate 10, and effective electrical contact and mechanical protection can be formed.

The photoresist may be a positive or negative photoresist. The concentration of the photoresist must not be too high, otherwise the solution mobility deteriorates and transfer cannot be achieved. The photoresist concentration must not be too low or insufficient to hold the chip and provide support for subsequent processing. Generally, the mass ratio of the photoresist to the solution is between 0.05 and 0.25.

After the LED chip 20 is sufficiently moved during the transfer, the solution is heated. In the heating process, the effects of evaporating the solvent and curing the photoresist are simultaneously realized. The temperature at which the photoresist is heated is preferably 100 c to 140 c, and a solvent having a boiling point lower than this temperature, such as ethanol, should be selected. The baking time is preferably 30 seconds to 10 minutes.

The second solution is: in order to further enhance the electrical connection between the LED chip 20 and the substrate 10, a metal layer 105 may be further covered between the two chip electrodes of the LED chip 20 and the first, second, and third substrate electrodes 11, 12, and 13. Photoresist is a necessary process during the deposition of the metal layer 105, so pre-coating the photoresist can also save one step of the photolithography process. In addition, compared to the conventional process of placing photoresist such as spin coating, the photoresist placed on the substrate by the first solution is more uniform.

Specifically, on the basis of the first solution, after the step 130 of heating to evaporate the solution, the transferring method further includes:

referring to fig. 26 and 27, the photoresist covering the two chip electrodes of the LED chip 20 and the photoresist between the adjacent LED chips 20 are removed by exposure, and the photoresist on the upper surface of the LED chip 20 is remained, so that the two chip electrodes of the LED chip 20 and the substrate electrodes 11, 12, and 13 are exposed.

Specifically, in this step, the photoresist layer 104 is selectively exposed, and the exposed region overlaps with the region where the first, second, and third substrate electrodes 11, 12, and 13 are located. Next, the exposed region is removed. The effect is shown in fig. 27.

Referring to fig. 28, a metal layer 105 is formed on the LED chip 20 and the first surface of the back plate by metal deposition. Specifically, the metal layer 105 deposited in this process has a thickness that is thinner than the thickness of the photoresist layer 104. The manner of depositing the metal may be evaporation or sputtering, in addition to electroplating.

Referring to fig. 29, the photoresist deposited on the LED chip 20 is removed, and a metal connection is formed between two chip electrodes of the LED chip 20 and corresponding substrate electrodes of the substrate 10. The effect is shown in fig. 29, as the photoresist layer 104 is removed, the metal layer 105 above the photoresist layer 104 is also removed. This forms a metal connection between the LED chip 20 and the first, second and third substrate electrodes 11, 12 and 13. These metals effectively reduce the contact resistance between the LED chip 20 and the substrate 10, and also provide a strong fixing force between the LED chip 20 and the substrate electrode. In the case shown in fig. 29, the thickness of the deposited metal layer 105 exceeds the width of the LED chip 20.

It can be understood that the thickness of the deposited metal layer 105 may also be smaller than the width of the LED chip 20, as shown in fig. 30, since chip electrodes are originally present at two ends of the LED chip 20, in the process of depositing the metal layer 105, the newly deposited metal may be fused with the two chip electrodes of the LED chip 20 to form a whole. Effective electrical contact and mechanical protection can be formed even if the thickness of the metal layer 105 is smaller than the width of the LED chip 20.

A third solution to the above problem: in step S110, a solution mixed with the LED chip 20 is put into the substrate, wherein the solution is not mixed with the photoresist, but mixed with some flux as the fixing paste, the flux may be rosin, or rosin resin based flux composed of resin, halide-containing activator, additive and organic solvent, and when the substrate electrode is disposed, a layer of soldering material 106, such as tin (Sn) or indium (In), is covered on the upper surface of the substrate electrode. The weight ratio of flux to solution ranges between 0.1 and 0.3. The process temperature may vary depending on the solder material 106.

Heating to evaporate the solution at step S130 includes:

referring to fig. 31, the solution is pre-evaporated to evaporate a portion of the solution.

The heating solution pre-evaporation is to perform a first-stage evaporation treatment on the solution, and after the first-stage evaporation treatment is performed on the solution, the volume of the solution is reduced to 0.1-0.5 times of the original volume, namely the volume of the solution after evaporation is 0.1-0.5 times of the volume of the solution before evaporation.

Referring to fig. 32, after the first-stage evaporation treatment is performed on the solution, the substrate 10 is heated to raise the temperature for entering the soldering process, so that the two chip electrodes of the LED chip 20, the first, second, and third substrate electrodes 11, 12, and 13 on the substrate 10 are respectively fused with the soldering material 106; the solution is then subjected to a second stage evaporation treatment to evaporate the remaining solution. Thus, when the transfer of the LED chip 20 is completed, the two chip electrodes of the LED chip 20 are lapped on the bonding material 106 of the two substrate electrodes, and the two chip electrodes of the LED chip 20 are directly contacted with the bonding material 106, so that an effective electrical contact and mechanical protection can be formed.

The two chip electrodes of the LED chip 20 are fused with the welding material to achieve electrical contact, the temperature is maintained at a high temperature for a certain time, and after the welding is completed, the temperature is lowered to room temperature, and the welding is completed.

In the above and other embodiments, the implementation steps can be flexibly changed under the same concept of the present solution. Such as another staged LED chip 20 solder reinforcement process:

stage one: the solution is more, the concentration is lower, and the LED chip 20 can move freely. The LED chips 20 can be moved fully in the process and are uniformly distributed on the back plate as much as possible; the solution may be specifically shaken slightly (i.e. perturbed), generally for a duration of 10s to 600s, the end of phase one marker: the LED chips 20 may be substantially uniformly distributed.

And a second stage: at this time, the arrangement of the LED chips 20 is substantially completed, some solution is evaporated to make the LED chips 20 not easily move, and then the temperature-rising soldering is started; specifically, the solution may be first heated to evaporate to reduce the volume of the solution to 0.1-0.5 times of the original volume, and then the solution is heated and welded, generally at 150-300 ℃ for 2-30 minutes. In the case of Sn, the preferred process temperature is between 220 ℃ and 250 ℃ and the duration of heating is between 15 minutes and 20 minutes.

In another embodiment, the two-stage thermal evaporation treatment of the solution in the above embodiment may be performed continuously in one step without any significant first-second stage boundary.

A fourth solution to the above problem: the solution is not mixed with photoresist or flux, but metal ions. The metal ions can be nickel, gold, copper, cadmium, etc. (electroplating simple substance electricity)Polar), or a mixture thereof (plating alloy electrode), and the concentration range of the metal ions is 10^-2mol/L to 10¹mol/L。

Because the pixel structure is provided with the first, second and third substrate electrodes 11, 12 and 13, one of the first, second and third substrate electrodes can be connected with the positive electrode of the power supply, the other two are connected with the negative electrode of the power supply, or one of the first and second substrate electrodes is connected with the positive electrode of the power supply, so that voltage difference exists between different types of substrate electrodes, and after the electrodes are electrified, metal ions are deposited on the surfaces of the two chip electrodes of the LED chip and the first, second and third substrate electrodes 11, 12 and 13, thereby playing a role in electroplating. Or applying power to the electrodes on the substrate 10 by the pixel structure driving method to perform the electroplating process. When the plating time is long enough, the metal on the surfaces of the first, second, and third substrate electrodes 11, 12, and 13 and the two chip electrodes of the LED chip 20 are connected together, as shown in fig. 33, to obtain a bonded LED chip. After the transfer is completed, the deposition of the metal layer 105 can be completed without moving the substrate 10, and better electrical contact and mechanical fixation can be achieved.

Referring to fig. 33, in the step of heating to evaporate the solution in step S130, the solution is pre-evaporated to evaporate a portion of the solution, and the first-stage evaporation treatment is performed on the solution to reduce the volume of the solution to 0.1 to 0.5 times of the original volume. Thereafter, the two chip electrodes of the LED chip 20 are covered with metal layers by electroplating; the solution is then subjected to a second stage evaporation treatment to evaporate the remaining solution.

In other embodiments, the electroplating process for depositing metal in the second and fourth solutions belongs to the same concept of the present solution, and the implementation steps can be flexibly changed. For example, another staged electroplating process described above:

stage one: the solution is more, the concentration is lower, and the LED chip 20 can move freely. The LED chips 20 can be moved fully in the process and are uniformly distributed on the back plate as much as possible; the solution may be specifically shaken slightly (i.e. perturbed), generally for a duration of 10s to 600s, the end of phase one marker: the LED chips 20 can be substantially uniformly distributed.

Stage two, at which time the arrangement of the LED chips 20 has been substantially completed, stage two: the solution is first heated to evaporate, reducing the volume of the solution to 0.1-0.5 times of the original volume. Then, the electroplating current is applied to carry out electroplating, the metal ions to be electroplated are preferably copper ions, and the time is preferably 5min to 30 min.

In addition, in the electroplating process, the electroplating rate should be controlled to be 0.4 to 0.6 microns per minute, and the time generally should not exceed one hour. If the pixel structure is a stacked type, the substrate electrode can protect the driving circuit 30 of the TFT region from being damaged during the plating process. If the pixel structure is such that the electrode unit and the TFT region are juxtaposed on the upper surface of the substrate 10, a higher-density intermediate insulating layer 102 (the intermediate insulating layer 102 has the same process requirements as the upper insulating layer 101 and the lower insulating layer 103 of the stacked structure) should be additionally fabricated above the TFT region, and the thickness is not less than 1 μm, so as to protect the TFT region.

The advantage of using an electroplating process to make the electrode reinforcement connection is that the upper metal layer 105 can be automatically deposited in the area where the substrate electrode is present without the need for photolithography and without the need for alignment. Moreover, the deposited metal layer 105 is not easy to climb onto the part of the LED chip 20 without metal, so as to avoid light blocking caused by the metal layer 105, and the light extraction efficiency of the LED chip 20 is high by this process.

In some embodiments, before step S130, the transferring method further includes: a power source is applied to the first, second, and third substrate electrodes 11, 12, and 13 to automatically align (i.e., self-assemble) the plurality of LED chips, so that two chip electrodes of the plurality of LED chips 20 are connected to any two substrate electrodes of the at least two substrate electrodes. The application of power to the first, second and third substrate electrodes 11, 12, 13 is similar to the application of power to the electrodes on the substrate 10 in the pixel structure driving method described above. This step can also be added to the transfer method in each of the above embodiments to improve the transfer efficiency of the LED chip during transfer.

If the electrode areas are selectively placed on the substrate 10, and solutions containing red (R), green (G) and blue (B) LED chips 20 are placed in the electrode areas, and the LED chips are prevented from mutually permeating, the LED chips are respectively arranged by any one of the bonding methods of the first embodiment, the first, the second, the third and the fourth solutions for chip electrode reinforcement, so that light emitting with three colors can be realized for each pixel point, and color conversion is not needed. In this embodiment, the LED chip 20 to be used may be a BG chip implemented by the above-mentioned a-type gallium nitride-based LED chip, an R chip implemented by the a-type gallium arsenide-based LED chip, or a B-type LED chip with the color coating layer 7.

If the LED chip 20 put in each electrode region is not of the target emission color, color conversion is necessary. Several color conversion methods are provided on the premise that each region corresponds to one electrode unit. Specifically, if each region corresponds to one electrode unit, the step S110 of putting the solution mixed with the plurality of LED chips into the substrate includes; put the solution into each zone separately, then the color conversion scheme is illustrated as follows:

first luminescent color conversion scheme: putting a solution mixed with the photoresist and the light conversion material into each area respectively; the solution is heated to evaporate, and the outer surface of the LED chip 20 is covered with a photoresist and a light conversion material. Thus, referring to FIG. 34, the top surface of the substrate 10 after being placed in the solution is coated with a photoresist layer 104 having a light conversion material.

Specifically, in this step, in addition to the blue LED chip 20 (which is a B-type LED chip or a gallium nitride-based LED chip), a light conversion material and a photoresist are mixed into the solution, and the light conversion material may be quantum dots or phosphor. The solution is printed on a specific electrode region in a selective input manner as shown in fig. 23, and the R and G electrode regions are printed with the solution with the light conversion material of the corresponding color, and the solution of the B electrode region is not provided with the light conversion material but may have a photoresist, see fig. 40.

After heating to evaporate the solution at step S130, further comprising:

first, the photoresist layer 104 wrapped between the two chip electrodes of the LED chip 20 and the adjacent LED chip 29 is removed by exposure, so that the two chip electrodes and the substrate electrode of the LED chip 20 are exposed.

Specifically, referring to FIG. 35, in this example, the irradiated regions of the photoresist are cured. The curing area is the gap area between the substrate electrodes or is slightly larger than the gap area of the substrate electrodes so as to increase the color conversion and the light extraction efficiency. Next, the photoresist layer 104 with the light conversion material of the non-irradiated region is removed, and the effect is as shown in fig. 36. The mass ratio of the light conversion material to the solution is in the range of 0.01 to 0.1, and the photoresist should be selected to be transparent after curing, that is, the photoresist is transparent after curing, so that light cannot be shielded.

Thereafter, a metal layer 105 is formed between the two chip electrodes of the LED chip 20 and the substrate electrode in the electrode area by metal deposition. Referring to fig. 37, the thickness of the metal layer 105 in this example is larger than the diameter of the LED chip 20; referring to fig. 38, the thickness of the metal layer 105 in this example is smaller than the diameter of the LED chip 20. The specific principle and function of the two settings are described with reference to the related embodiments in fig. 29 and fig. 30.

Second luminescent color conversion scheme: in contrast to the first luminescence color conversion scheme, the regions (electrode units) are printed with a light conversion material before each region is put in a solution, respectively.

Then, a solution mixed with a photoresist is put into each region separately. The solution may be printed on a specific electrode region in a selective input manner as shown in fig. 23, or the substrate 10 may be immersed in the solution in a non-differential input manner as shown in fig. 24.

After heating to evaporate the solution in step S130, referring to fig. 39, the outer surface of the LED chip 20 is covered with the photoresist layer 104 having the light conversion material.

In an alternative embodiment, the regions include an R electrode region, a G electrode region, and a B electrode region, and then printing the light conversion material to the regions includes:

printing light conversion materials on the R electrode area and the G electrode area respectively;

in step S130, after heating to evaporate the solution, the R color conversion layer 107 and the G color conversion layer 108 formed by photoresist and light conversion material are coated on the outer surface of the LED chip in the R and G electrode regions, and the photoresist layer 104 formed by photoresist is coated on the outer surface of the LED chip in the B electrode region, as shown in fig. 40.

Finally, after step 130, the method further includes:

referring to fig. 35 and 36, the photoresist on the region other than the upper surface of the chip body of the LED chip 20 is removed by exposure;

referring to fig. 37 and 38, a metal layer 105 is formed between two chip electrodes of the LED chip and the substrate electrode in the electrode area by metal deposition.

Third emission color conversion scheme: placing a solution mixed with an LED chip into a substrate at step S110, the solution including a first solution, a second solution and a third solution, the first solution being further mixed with a first light conversion material (red), a photoresist, and metal ions, the second solution being mixed with a second light conversion material (green), a photoresist, and metal ions, the third solution being further mixed with a photoresist and metal ions, the regions including an R electrode region, a G electrode region, and a B electrode region, the placing the solution mixed with an LED chip into the substrate at step S110 includes: putting a first solution into the R electrode area; putting a second solution into the G electrode area; a third solution is placed into the B electrode area. It should be noted that the R electrode region may be prepared for connecting LED chips emitting red light, the B electrode region may be prepared for connecting LED chips emitting blue light, and the G electrode region may be prepared for connecting LED chips emitting green light. In addition, the first solution, the second solution and the third solution may be one or at least one of deionized water, toluene, xylene, methanol, ethanol, isopropanol, etc., respectively, which is not limited herein.

In one example, red quantum dots (or phosphor) as a first light conversion material are added to the first solution, and green quantum dots (or phosphor) as a second light conversion material are added to the second solution.

Specifically, the step of heating to evaporate the solution at step S130 includes: firstly, carrying out first-stage pre-evaporation on the solution put into the substrate 10 to evaporate part of the solution; next, referring to fig. 33, similar to the fourth solution of the electrode reinforcing connection: after the first-stage evaporation treatment is performed on the solution, a power supply is applied to the substrate electrode of at least two types of substrate electrodes to perform an electroplating process, so that the two chip electrodes and the substrate electrode of the LED chip 20 are covered with the metal layer 105, and the two chip electrodes of the LED chip 20 and the first, second and third substrate electrodes 11, 12 and 13 form relatively fixed electrical connections. The pre-evaporation is to evaporate a part of the solution, so that the LED chip 20 is not easily separated from the substrate, but the amount of the solution is sufficient to perform the electroplating. On the first, second and third substrate electrodes 11, 12 and 13, electroplating is performed (because the solution contains metal ions) by the fourth solution bonding method described above, and the plated metal layer 105 is coated on the chip electrodes of the LED chip 20. After heating to evaporate the remaining solution, fig. 40 is a schematic diagram showing the effect of the region of one pixel.

In addition, when an electroplating process is required, it should be noted that the concentration of the light conversion material should be increased appropriately, because the metal deposition process may mix the light conversion material on the substrate electrode, resulting in a decrease in the concentration of the light conversion material. Since the substrate electrodes are not transparent, this mixing has no effect on the screen performance, but the concentration of the color conversion material should be increased appropriately to compensate for the decrease in concentration during the plating process.

Fourth emission color conversion scheme: in the region of each pixel point, light-emitting units of three colors of R, G and B need to be manufactured. Since, in this example, the solution put in step S110 is a single color LED chip, such as blue; therefore, two electrode regions (R electrode region, G electrode region) among them need to be color-converted. In one example, color conversion includes the following processes:

in the first stage, only the red quantum dots (or phosphors) are mixed into the solution, so that the entire substrate 10 can be covered with the R color conversion layer 107 made of the red quantum dots after the solution is evaporated. In the second stage, the R color conversion layer 107 can be selectively removed by photolithography, and only the R color conversion layer 107 in the R electrode region remains.

In the third stage, green light conversion material is placed on the G electrode region by conventional quantum dot printing to form the G color conversion layer 108. Thus, the manufacturing process of the primary color conversion material is reduced by using the scheme, and fig. 40 is a schematic diagram of the effect of the region of one pixel point.

Fifth luminescent color conversion scheme: referring to fig. 41, instead of differentiating the light conversion materials of three colors, a mixture of two other color conversion materials different from the light emitting color of the mixed LED chip 20 may be covered on all pixel areas, for example, the mixed LED chip 20 is a blue LED chip, and the mixture is the RG color conversion layer 110. This way the process can be simplified, the composition of the color conversion material and the thickness of the constituent color conversion layer being such that the converted and transmitted light has RGB components at the same time. In order to realize three colors, a filter corresponding to the emission color is required to be disposed above the color conversion layer in each electrode region, a G filter 111 is disposed in the G electrode region, an R filter 112 is disposed in the R electrode region, and a B filter 113 is disposed in the B electrode region. In order to prevent interference between adjacent colors, a light shielding layer 115 should be formed between different light emitting (electrode) regions to shield light.

In step S110, a solution mixed with a plurality of LED chips is put into a substrate, the solution is mixed with a photoresist and a light conversion material, and the photoresist with the light conversion material is coated on the upper surface of the substrate 10; referring to fig. 41, after the solution is evaporated in step S130, the transferring method further includes: a light-shielding layer 115 is provided between the respective electrode units; the filter films 111-113 with predefined colors are arranged on each electrode unit. In another embodiment, in step S110, metal ions, flux, and the like may be mixed into the solution to reinforce the connection strength between the LED chip 20 and the substrate electrode in the substrate 10.

In the above embodiments, the whole manufacturing processes are described by taking the substrate 10 with three types of substrate electrodes as related examples, and it is understood that the processes of the above embodiments are also applicable to the substrate 10 with two types of substrate electrodes or more than four types of substrate electrodes, and thus the details are not repeated here. In addition, in the above embodiment, it is mentioned that the LED chip 20 mixed with the solution mostly uses a blue LED chip, and for this reason, it can be understood that the light emitting color of the LED chip 20 mixed with the solution can be arbitrarily selected according to application requirements, cost, and the like, and after the light emitting color of the LED chip 20 mixed with the solution is selected, a light emitting region which needs to be subjected to color conversion can select a light conversion material with an adapted color according to the situation, and those skilled in the art can arrange the light conversion material according to requirements, and details are not described here.

The above-mentioned embodiments are only used for illustrating the technical solutions of the present application, and not for limiting the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications and substitutions do not substantially depart from the spirit and scope of the embodiments of the present application and are intended to be included within the scope of the present application.

Claims (30)

1. A method for transferring LED chips is characterized by comprising the following steps:

providing a substrate, putting a solution mixed with an LED chip into the substrate, wherein the substrate is provided with a plurality of electrode units, each electrode unit comprises a plurality of substrate electrodes, each LED chip comprises a chip main body and two chip electrodes arranged on the chip main body at intervals, and the distance between the two chip electrodes of each LED chip is larger than the minimum distance between any two adjacent substrate electrodes;

heating to evaporate the solution so that the LED chip is placed on the substrate.

2. The transfer method of claim 1 wherein said solution is further mixed with a photoresist and after said heating to evaporate said solution, an LED chip disposed on said substrate is coated with a photoresist layer.

3. The transfer method according to claim 2, wherein the transfer method further comprises:

removing the photoresist wrapped on the two chip electrodes of the LED chips and between the adjacent LED chips in an exposure mode;

forming metal layers on the LED chip and the substrate in a metal deposition mode;

and removing the photoresist deposited on the LED chip, and forming metal connection between two chip electrodes of the LED chip and the corresponding substrate electrodes.

4. The transfer method of claim 1, wherein the solution is further mixed with metal ions, and wherein the heating to evaporate the solution comprises:

pre-evaporating the solution to evaporate a portion of the solution;

covering two chip electrodes of the LED chip and the substrate electrode with metal layers through electroplating;

the remaining solution was evaporated.

5. The transfer method of claim 1, wherein the solution is mixed with flux and the substrate is further covered with a solder material, and wherein the heating to evaporate the solution comprises:

carrying out a first-stage evaporation treatment on the solution;

heating the substrate to fuse the two chip electrodes of the LED chip, the substrate electrode and the welding material;

the remaining solution was evaporated to dryness.

6. The transfer method according to claim 1, wherein said substrate is provided with a plurality of areas, each area corresponding to one of said electrode units, and said introducing a solution mixed with LED chips into the substrate comprises;

the solution is placed into each of the zones separately.

7. The transfer method of claim 6, wherein said solution mixed with photoresist, before said separately introducing said solution into each of said regions, further comprises:

printing a light conversion material to the area;

the heating to evaporate the solution comprises:

heating to evaporate the solution, wherein the outer surface of the LED chip is wrapped with the photoresist and the light conversion material.

8. The transfer method according to claim 7, wherein the regions include an R electrode region, a G electrode region, and a B electrode region; the printing of the light conversion material to the area includes:

printing the light conversion material to the R electrode area and the G electrode area respectively;

the heating to evaporate the solution comprises:

heating to evaporate the solution, wherein the photoresist and the light conversion material are wrapped on the outer surfaces of the LED chips of the R electrode area and the G electrode area, and the photoresist is wrapped on the outer surface of the LED chip of the B electrode area.

9. The transfer method of claim 8, wherein after said heating to evaporate said solution, further comprising:

removing the photoresist which is wrapped between the two chip electrodes of the LED chip and the adjacent LED chip in an exposure mode;

and forming a metal layer between the two chip electrodes of the LED chip and the electrode in the electrode area by means of metal deposition.

10. The transfer method according to claim 6, wherein the solutions include a first solution mixed with a first light conversion material, a photoresist, and metal ions, a second solution mixed with a second light conversion material, a photoresist, and metal ions, and a third solution mixed with a photoresist, and metal ions, the regions including an R electrode region, a G electrode region, and a B electrode region, and the solution mixed with LED chips is put into the substrate, including:

putting the first solution into the R electrode area;

placing the second solution into the G electrode area;

and putting the third solution into the B electrode area.

11. The transfer method of claim 10, wherein said heating to evaporate said solution comprises:

pre-evaporating the solution to evaporate a part of the solution;

covering two chip electrodes of the LED chip and the substrate electrode with metal layers through electroplating;

the remaining solution was evaporated by heating.

12. The transfer method according to any one of claims 1 to 11, wherein two chip electrodes of the LED chip are respectively wrapped around both ends of the chip body.

13. The transfer method according to claim 1, wherein the plurality of substrate electrodes includes first and second substrate electrodes, the first and second substrate electrodes on the substrate being staggered in a longitudinal direction, and the first and second substrate electrodes on the substrate being staggered in a transverse direction.

14. The transfer method according to claim 13, wherein the first substrate electrode and the second substrate electrode have a cross-sectional shape of a regular triangle, and a ratio of a minimum distance between the first substrate electrode and the second substrate electrode to a side length of the regular triangle is in a range of: 0.005-0.05, wherein the ratio range of the side length of the regular triangle to the distance between the two chip electrodes of the LED chip is as follows: 0.1 to 1.

15. The transfer method according to claim 13, wherein the first substrate electrode and the second substrate electrode have a square cross-sectional shape, and a ratio of a minimum distance between the first substrate electrode and the second substrate electrode to a side length of the square is in a range of: 0.01-0.1, wherein the ratio range of the side length of the square to the distance between two chip electrodes of the LED chip is as follows: 0.2 to 1.4.

16. The transfer method according to claim 13, wherein the first substrate electrode and the second substrate electrode have a square cross-sectional shape, and a distance between two chip electrodes of the LED chip is smaller than a sum of a side length of the square and a minimum distance between the first substrate electrode and the second substrate electrode.

17. The transfer method of any one of claims 13 to 16, wherein a minimum spacing between adjacent electrode units is equal to a minimum distance between a first substrate electrode and a second substrate electrode between the electrode units.

18. The transfer method of claim 13, wherein the plurality of substrate electrodes further comprises a third substrate electrode, and wherein any one of the first substrate electrode, the second substrate electrode, and the third substrate electrode on the substrate is adjacent to two other substrate electrodes, respectively.

19. The transfer method according to claim 18, wherein the first substrate electrode, the second substrate electrode, and the third substrate electrode have a circular cross-sectional shape, and a ratio of a minimum distance between the first substrate electrode and the second substrate electrode to a diameter of the circular shape ranges from: 0.01-0.1, the ratio range of the diameter of the circle and the distance between two chip electrodes of the LED chip is as follows: 0.6 to 2.

20. The transfer method according to claim 18, wherein the first substrate electrode, the second substrate electrode, and the third substrate electrode have a cross-sectional shape of a regular hexagon, and a ratio of a minimum distance between the first substrate electrode and the second substrate electrode to a side length of the regular hexagon is in a range of: 0.05-0.2, wherein the ratio range of the side length of the regular hexagon to the distance between two chip electrodes of the LED chip is as follows: 0.2 to 2.

21. The transfer method of claim 18, wherein the minimum distances between the first substrate electrode, the second substrate electrode, and the third substrate electrode in the electrode units are identical, and the minimum distance between adjacent electrode units is equal to the minimum distance between the first substrate electrode and the second substrate electrode between the electrode units.

22. The transfer method according to any one of claims 1 to 11, 13 to 16, and 18 to 21, wherein a pair of stopper grooves is formed in two adjacent substrate electrodes in a direction from a central portion of one electrode toward a central portion of the other electrode.

23. The transfer method of claim 22, wherein the sum of the length of the pair of limiting grooves and the minimum distance between two corresponding adjacent substrate electrodes is 1.05 times to 1.3 times the distance between two chip electrodes of the LED chip.

24. The transfer method of any one of claims 1 to 11, wherein the solution comprises one or more of deionized water, toluene, xylene, methanol, ethanol, and isopropanol.

25. The transfer method of claim 1, wherein the chip body is a cylinder, and the two chip electrodes are spaced apart from each other on a side of the cylinder.

26. The transfer method of claim 25, wherein the chip electrode is a circular ring structure, and a difference between an outer diameter of the chip electrode and a radius of the chip body is greater than 0 and less than 3 mm.

27. The transfer method of claim 26, wherein the spacing between the two chip electrodes is equal to the difference between the distance between the two ends of the chip body and the width between the two chip electrodes.

28. The transfer method according to claim 1, wherein the chip body is a cylinder, the two chip electrodes are spaced apart from each other at both ends of the cylinder, and the pitch of the chip electrodes is equal to the distance between both ends of the cylinder.

29. The transfer method according to claim 1, wherein the chip body is a cylinder, and the two chip electrodes respectively coat ends of the cylinder.

30. The transfer method according to claim 1, wherein the chip body is a prism, the two chip electrodes are arranged at intervals on the side surfaces of the prism, the chip electrodes comprise a plurality of chip sub-electrodes, the number of the chip sub-electrodes is equal to the number of the side edges of the prism, and each chip sub-electrode is protruded on one side surface of the chip body to form a corresponding annular array.

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