CN115775816A - LED chip transfer method and display panel - Google Patents

Abstract

The invention relates to a transfer method of an LED chip. The method comprises the following steps: providing a display back plate comprising a magnetic shielding layer, a substrate, at least one first sub-pad group and an adhesion layer; providing a first transfer plate carrying at least one first LED chip, wherein a first magnetic conducting layer is covered on a first electrode group of the first LED chip; at least partially embedding the first LED chip in the adhesive layer; applying an electrical signal to each first sub-pad group to generate a magnetic field; and stripping the first LED chip to be transferred from the first transfer plate, wherein the first magnetic conducting layer drives the first LED chip to move towards the first sub-bonding pad group under the action of magnetic force in the direction vertical to the substrate until the first electrode group is attached to the corresponding first sub-bonding pad group. The invention also provides a display panel. According to the LED chip transfer method and the display panel, the LED chip is fixed on the display back plate through magnetic force adsorption and adhesion, and the LED chip cannot be displaced when being stripped.

Description

LED chip transfer method and display panel

Technical Field

The present application relates to the field of semiconductor light emitting technologies, and in particular, to a method for transferring LED chips and a display panel.

Background

Because of its excellent characteristics of high luminous efficiency, high reliability, freely assembled size, etc., light Emitting Diodes (LEDs) are widely used in many lighting display fields, especially in large-size display application scenes such as outdoor large billboards, stage background walls, large text broadcast screens, etc. The next development trend of current LED display is to miniaturize LED core particles to micron size (i.e. Micro-LED) to replace the small and medium size display application scenes of indoor televisions, mobile phone displays, wearable devices, etc. occupied by the existing liquid crystal display screens and organic light emitting diode display screens.

The Micro-LED full-color display is realized mainly by means of a huge transfer technology of a Micro-LED chip, and at present, in the process of transferring the Micro-LED chip to a display back plate, when the Micro-LED chip is peeled off from a transfer plate, the Micro-LED chip is easy to displace, so that the corresponding positions of the LED chip and the display back plate cannot be aligned, and the transfer yield is low.

Disclosure of Invention

In view of the above deficiencies of the prior art, the present application aims to provide a method for transferring LED chips and a display panel, wherein the LED chips are not displaced under the combined action of magnetic force and adhesion force when the LED chips are peeled off from the transfer plate by the magnetic force adsorption action of the display backplane and the adhesion force of the adhesion layer of the display backplane to the LED chips, so that the LED chips can be precisely aligned and attached to corresponding positions of the display backplane, and the transfer efficiency and transfer yield of the LED chips are improved.

A method for transferring an LED chip comprises the following steps: providing a display back plate, wherein the display back plate comprises a magnetic shielding layer, a substrate, at least one pad group and an adhesion layer, the magnetic shielding layer is arranged on the first side of the substrate, the pad group is arranged on the second side of the substrate, the pad group comprises at least one first sub-pad group, the first side and the second side of the substrate are oppositely arranged, and the adhesion layer is arranged on the second side of the substrate and covers the pad group; providing a first transfer plate, wherein at least one first LED chip is carried on the first transfer plate, and a first magnetic conducting layer covers a first electrode group of the first LED chip; at least partially embedding the first LED chip in the adhesion layer, wherein the first LED chip to be transferred is aligned with the corresponding first sub-pad set; applying an electrical signal to each of the first sub-pad groups to generate a magnetic field at the second side of the substrate; and stripping the first LED chip to be transferred from the first transfer plate, wherein the first magnetic conducting layer drives the first LED chip to move to the corresponding first sub-bonding pad group under the action of magnetic force in the direction perpendicular to the substrate until the first electrode group is attached to the corresponding first sub-bonding pad group.

According to the LED chip transfer method, the magnetic adsorption effect of the display back plate on the first LED chip and the adhesion force of the adhesion layer on the first LED chip are utilized, so that when the first LED chip is peeled off from the first transfer plate, the first LED chip cannot be displaced under the combined action of the magnetic force and the adhesion force, the first LED chip can be accurately aligned and attached to the corresponding position of the display back plate, and the transfer efficiency and the yield of the first LED chip are improved.

Optionally, the first sub-pad group includes a positive pad and a negative pad, and the applying an electrical signal to each of the first sub-pad groups to generate a magnetic field on the second side of the substrate includes: and respectively applying a first electric signal and a second electric signal to the positive electrode bonding pad and the negative electrode bonding pad to form a voltage difference between the positive electrode bonding pad and the negative electrode bonding pad, and controlling the first electric signal and the second electric signal to periodically change the voltage difference so as to generate a magnetic field on the second side of the substrate.

Optionally, the controlling the first electrical signal and the second electrical signal such that the voltage difference varies periodically comprises: controlling the first electrical signal and the second electrical signal such that the voltage difference periodically increases from a first voltage difference value to a second voltage difference value.

Optionally, after the first electrode group is attached to the corresponding first sub-pad group, the method further includes: bonding the first electrode group, the first magnetic conductive layer and the first sub-pad group.

Optionally, a sacrificial layer is disposed between the first LED chip and the first transfer plate, and the peeling off the first LED chip to be transferred from the first transfer plate includes: selectively irradiating a sacrificial layer located within an orthographic projection area of the first LED chip to be transferred on the first transfer plate with laser light.

Optionally, the pad group further includes at least one second sub-pad group, and after the first electrode group is attached to the corresponding first sub-pad group, the method further includes: providing a second transfer plate, wherein at least one second LED chip is loaded on the second transfer plate, a second magnetic conducting layer covers a second electrode group of the second LED chip, and the light emitting color of the second LED chip is different from that of the first LED chip; at least partially embedding the second LED chip in the adhesion layer, wherein the second LED chip to be transferred is aligned with the corresponding second sub-pad set; applying an electrical signal to each of the second sub-pad groups to generate a magnetic field at the second side of the substrate; and stripping the second LED chip to be transferred from the second transfer plate, wherein the second magnetic conducting layer drives the second LED chip to move to the corresponding second sub-bonding pad group under the action of magnetic force in the direction perpendicular to the substrate until the second electrode group is attached to the corresponding second sub-bonding pad group.

Optionally, the pad group further includes at least one third sub-pad group, and after the second electrode group is attached to the corresponding second sub-pad group, the method further includes: providing a third transfer plate, wherein at least one third LED chip is loaded on the third transfer plate, a third electrode group of the third LED chip is covered with a third magnetic conductive layer, and the light emitting color of the third LED chip is different from the light emitting colors of the first LED chip and the second LED chip; at least partially embedding the third LED chip in the adhesion layer, wherein the third LED chip to be transferred is aligned with the corresponding third sub-pad set; applying an electrical signal to each of the third sub-pad groups to generate a magnetic field at the second side of the substrate; and stripping the third LED chip to be transferred from the third transfer plate, wherein the third magnetic conductive layer drives the third LED chip to move to the corresponding third sub-bonding pad group under the action of a magnetic force in a direction perpendicular to the substrate until the third electrode group is attached to the corresponding third sub-bonding pad group.

Optionally, the transferring method further comprises: bonding the first electrode group, the first magnetic conductive layer and the first sub-pad group, and simultaneously bonding the second electrode group, the second magnetic conductive layer and the second sub-pad group and bonding the third electrode group, the third magnetic conductive layer and the third sub-pad group.

Optionally, the first electrode group includes a positive electrode and a negative electrode, and when the first electrode group is attached to the corresponding first sub-pad group, the positive electrode is attached to the positive electrode pad, and the negative electrode is attached to the negative electrode pad.

Based on the same inventive concept, the display panel comprises a display back plate and at least one LED chip fixed on the display back plate, and the at least one LED chip is fixed on the display back plate by adopting the LED chip transfer method.

According to the display panel, the at least one LED chip is transferred onto the display back plate by the LED chip transfer method, and the at least one LED chip cannot be displaced under the combined action of magnetic force and adhesive force, so that the at least one LED chip can be accurately aligned and attached to the corresponding position of the display back plate, and the transfer efficiency and the transfer yield are improved.

Drawings

Fig. 1 is a flowchart of a transfer method of an LED chip according to an embodiment of the present disclosure;

FIG. 2 is a schematic cross-sectional view of a display backplane provided in an embodiment of the present application;

FIG. 3 is a schematic cross-sectional view of a first transfer plate provided in an embodiment of the present application;

fig. 4 is a schematic diagram illustrating a positional relationship between the first transfer plate and the display back plate after step S103 in fig. 1 is completed;

fig. 5 is a schematic diagram illustrating a positional relationship between the first LED chip and the display back plate after step S105 in fig. 1 is completed;

FIG. 6 is a schematic diagram showing the positional relationship between the positive and negative pads and the positive and negative electrodes;

FIG. 7 is a schematic of the voltage difference between the positive and negative leads as a function of time;

FIG. 8 is a schematic view of the direction of the electric field, the direction of the magnetic field, and the direction of the magnetic force;

fig. 9 to 10 are schematic views illustrating a process of separating a first LED chip from a first transfer plate according to an embodiment of the present application;

fig. 11 is a flowchart of a transfer method of an LED chip according to another embodiment of the present application;

fig. 12 is a schematic cross-sectional view of a second transfer plate provided in an embodiment of the present application;

fig. 13 is a schematic view illustrating a positional relationship between the second transfer plate and the display back plate after step S107 in fig. 11 is completed;

fig. 14 is a schematic diagram illustrating a positional relationship between the second LED chip and the display back plate after step S109 in fig. 11 is completed;

fig. 15 is a flowchart of a transferring method of an LED chip according to another embodiment of the present application;

FIG. 16 is a schematic cross-sectional view of a third transfer plate provided in an embodiment of the present application;

fig. 17 is a schematic view illustrating a positional relationship between the third transfer plate and the display backplane after step S110 in fig. 15 is completed;

fig. 18 is a schematic diagram of a positional relationship between the third LED chip and the display back plate after step S112 in fig. 15 is completed.

Description of reference numerals:

100-a display backplane;

110-a magnetic shielding layer;

120-a substrate;

130-pad group;

131-a first set of sub-pads;

1311-positive electrode pad;

1312-negative electrode pad;

132-a second set of sub-pads;

133-a third sub-pad group;

140-an adhesive layer;

150-positive lead;

160-negative electrode lead;

210-a first transfer plate;

220-a first LED chip;

221-a first electrode group;

222-a first epitaxial structure;

230-a first magnetically conductive layer;

2211-positive electrode;

2212-negative electrode;

40-a sacrificial layer;

310-a second transfer plate;

320-a second LED chip;

321-a second electrode group;

322-a second epitaxial structure;

330-a second magnetically conductive layer;

410-a third transfer plate;

420-a third LED chip;

421-a third electrode group;

422-a third epitaxial structure;

430-third magnetically conductive layer.

Detailed Description

To facilitate an understanding of the present application, the present application will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present application are given in the accompanying drawings. This application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

In the description of the present application, the terms "first", "second", "third", etc. are used for distinguishing different objects, not for describing a particular order, and furthermore, the terms "upper", "lower", "inner", "outer", etc. indicate orientations or positional relationships based on those shown in the drawings, only for convenience of description and simplicity of description, but do not indicate or imply that the referred device or element must have a particular orientation, be constructed in a particular orientation, and be operated, and thus, should not be construed as limiting the present application.

Throughout the description of the present application, unless expressly stated or limited otherwise, the term "coupled" is to be construed broadly, e.g., as meaning fixedly attached, detachably attached, or integrally attached; they may be connected directly or indirectly through intervening media, or may be interconnected between two elements. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art as appropriate.

Referring to fig. 1, fig. 1 is a flowchart of a transfer method of an LED chip provided in the present embodiment, fig. 2 is a schematic cross-sectional view of a display backplane 100 provided in the present embodiment, fig. 3 is a schematic cross-sectional view of a first transfer plate 210 provided in the present embodiment, fig. 4 is a schematic positional relationship between the first transfer plate 210 and the display backplane 100 after step S103 in fig. 1 is completed, and fig. 5 is a schematic positional relationship between the first LED chip 221 and the display backplane 100 after step S105 in fig. 1 is completed. As shown in fig. 1, the transfer method of the LED chip includes the following steps:

s101: providing the display back plate 100 as shown in fig. 2, wherein the display back plate 100 includes a magnetic shielding layer 110, a substrate 120, at least one pad group 130 and an adhesion layer 140, the magnetic shielding layer 110 is disposed on a first side of the substrate 120, the at least one pad group 130 is disposed on a second side of the substrate 120, the pad group 130 includes at least one first sub-pad group 131, the first side and the second side of the substrate 120 are disposed opposite to each other, and the adhesion layer 140 is disposed on the second side of the substrate 120 and covers the pad group 130.

S102: providing a first transfer plate 210 as shown in fig. 3, wherein at least one first LED chip 220 is carried on the first transfer plate 210, and a first magnetic conductive layer 230 is covered on a first electrode group 221 of the first LED chip 220.

S103: the first LED chip 220 is at least partially embedded in the adhesive layer 140, wherein the first LED chip 220 to be transferred is aligned with the corresponding first sub-pad group 131, resulting in fig. 4.

S104: an electric signal is applied to each of the first sub-pad groups 131 to generate a magnetic field at the second side of the substrate 120.

S105: the first LED chip 220 to be transferred is peeled off from the first transfer plate 210, and the first magnetic conductive layer 230 drives the first LED chip 220 to move to the corresponding first sub-pad group 131 under the action of a magnetic force perpendicular to the substrate 120 direction until the first electrode group 221 is attached to the corresponding first sub-pad group 131, with the result as shown in fig. 5.

Here, the steps S104 and S105 may be performed simultaneously, that is, the first LED chip 220 to be transferred is peeled off from the first transfer plate 210 while an electrical signal is applied to the first sub-pad group 131. Alternatively, step S104 precedes step S105, i.e., the magnetic field is generated on the second side of the substrate 120, and then the first LED chip 220 to be transferred is peeled off from the first transfer plate 210.

In some embodiments, as shown in fig. 3, the first LED chip 220 further includes a first epitaxial structure 222, and the first epitaxial structure 222 and the first electrode group 221 are sequentially stacked on the first transfer plate 210.

The magnetic shielding layer 110 may be at least one of a silicon steel sheet and a CNTs/GO layer (graphene oxide/carbon nanotube) for shielding a magnetic field on the first side of the substrate 120. The adhesive layer 140 is a non-conductive adhesive layer, which may be made of a polymer material, such as epoxy resin.

The magnetic conductive layer may be a metal material with magnetism, such as iron, nickel, iron-nickel alloy, and the like.

According to the transfer method of the LED chips, the magnetic adsorption effect of the display back plate 100 on the first LED chips 220 and the adhesion force of the adhesion layer 140 on the first LED chips 220 are utilized, so that when the first LED chips 220 are peeled off from the first transfer plate 210, the first LED chips 220 cannot be displaced under the combined action of the magnetic force and the adhesion force, and therefore the first LED chips 220 can be accurately aligned and attached to corresponding positions of the display back plate 100, and the transfer efficiency and the transfer yield of the first LED chips 220 are improved.

Referring to fig. 6, fig. 6 is a schematic diagram illustrating the positional relationship between the positive electrode bonding pad 1311 and the negative electrode bonding pad 1312 and the positive electrode 2211 and the negative electrode 2212. As shown in fig. 6, in some embodiments, the first sub-pad group 131 includes a positive pad 1311 and a negative pad 1312, the first electrode group 221 includes a positive electrode 2211 and a negative electrode 2212, and when the first electrode group 221 is attached to the corresponding first sub-pad group 131, the positive electrode 2211 is attached to the positive pad 1311, and the negative electrode 2212 is attached to the negative pad 1312. The materials of the positive electrode 2211, the negative electrode 2212, the positive electrode pad 1311 and the negative electrode pad 1312 may be all metal materials, such as gold, indium, tin, copper, nickel, etc.

In the transfer method of the LED chip provided by the present application, a first sub-magnetic conductive layer and a second sub-magnetic conductive layer are respectively covered on the positive electrode 2211 and the negative electrode 2212 of the first electrode group 221, and the first sub-magnetic conductive layer and the second sub-magnetic conductive layer drive the positive electrode 2211 and the negative electrode 2212 to respectively move to the corresponding positive pad 1311 and the corresponding negative pad 1312 under the action of a magnetic force perpendicular to the direction of the substrate 120, so that the positive electrode 2211 and the negative electrode 2212 are respectively aligned and attached to the corresponding positive pad 1311 and the corresponding negative pad 1312.

In some embodiments, the applying an electrical signal to each of the first sub-pad groups 131 to generate a magnetic field at the second side of the substrate 120 includes: applying a first electrical signal and a second electrical signal to the positive pad 1311 and the negative pad 1312, respectively, such that a voltage difference is formed between the positive pad 1311 and the negative pad 1312, and controlling the first electrical signal and the second electrical signal such that the voltage difference is periodically varied to generate a magnetic field at the second side of the substrate 120.

Specifically, referring to fig. 6 again, in some embodiments, the display back plate 100 further includes a positive electrode lead 150 and a negative electrode lead 160, the positive electrode pad 1311 of the first sub-pad group 131 is connected to the positive electrode lead 150, the negative electrode pad 1312 is connected to the negative electrode lead 160, the negative electrode lead 160 is grounded, the voltage value of the negative electrode lead 160 is 0, the positive electrode lead 150 is connected to a voltage input terminal, the voltage difference between the positive electrode lead 150 and the negative electrode lead 160 is the voltage value applied to the positive electrode lead 150, a voltage difference is formed between the positive electrode lead 150 and the negative electrode lead 160, such that a voltage difference is generated between the positive electrode pad 1311 and the negative electrode pad 1312 to generate an electric field, and a magnetic field is generated between the positive electrode pad 1311 and the negative electrode pad 1312 by setting the voltage difference between the positive electrode lead 150 and the negative electrode lead 160 to periodically increase with time, and such that the magnetic field covers an area between the first sub-group 131 and the first electrode group 221. When the first LED chip 220 is in the magnetic field, the first magnetic conductive layer 230 is subject to a magnetic force in a direction perpendicular to the substrate 120.

For example, referring to fig. 7, fig. 7 is a schematic diagram of the voltage difference V changing with time t, as shown in fig. 7, the voltage difference V periodically increases from a first voltage difference a to a second voltage difference B, so that the intensity of the electric field between the positive pad 1311 and the negative pad 1312 periodically increases. During the process of increasing the strength of the electric field, a magnetic field is generated between the positive electrode pad 1311 and the negative electrode pad 1312, and the direction of the magnetic field can be determined in a right-hand spiral manner according to the direction of the electric field, wherein the right-hand spiral manner refers to: the thumb of the right hand is straightened and is approximately vertical to the index finger, the other four fingers are bent, the pointing direction of the thumb of the right hand is the direction of the electric field, and the pointing direction of the bent four fingers of the right hand is the direction of the magnetic field.

Referring to fig. 8, fig. 8 illustrates a direction of the electric field on the cross section of the positive pad 1311 and the negative pad 1312, and as shown in fig. 8, a direction X of the electric field is from the positive pad 1311 to the negative pad 1312, that is, a direction in which the positive pad 1311 points to the negative pad 1312 is a direction of a thumb of a right hand, and a direction in which a four-finger of the right hand bends is perpendicular to and inward of the cross section of the positive pad 1311 and the negative pad 1312, that is, a direction in which the magnetic field is perpendicular to and inward of the cross section of the positive pad 1311 and the negative pad 1312, that is, a direction perpendicular to and inward of a paper surface shown in fig. 8. The cross sections of the positive electrode bonding pad 1311 and the negative electrode bonding pad 1312 are surfaces cut by the central connecting line of the positive electrode bonding pad 1311 and the negative electrode bonding pad 1312, and the cross sections of the positive electrode bonding pad 1311 and the negative electrode bonding pad 1312 are perpendicular to the substrate 120 and parallel to the central connecting line of the positive electrode bonding pad 1311 and the negative electrode bonding pad 1312. When the first magnetic conductive layer 230 is in the magnetic field, the direction of the magnetic force received by the first magnetic conductive layer 230 in the magnetic field is determined by a left-hand rule, where the left-hand rule refers to: five fingers are all straightened and are roughly in the same plane, and the thumb and the forefinger of right hand are roughly perpendicular, the direction in magnetic field passes the center of the palm of the left hand, and the pointing direction of the four fingers that the left hand is straightened is the electric field direction, and the pointing direction of the thumb of the left hand is the magnetic force direction.

Specifically, referring to fig. 8 again, fig. 8 further illustrates a direction Z of a magnetic force applied to the first magnetic conductive layer 230 in the magnetic field, as shown in fig. 8, the direction Z of the magnetic force is a direction perpendicular to the substrate 120 and a direction in which the first magnetic conductive layer 230 is close to the substrate 120. The first magnetic conductive layer 230 is subjected to a magnetic force in the Z direction and relatively fixed to the first sub-pad group 131 on a plane parallel to the substrate 120, so that when the first LED chip 220 is peeled off from the first transfer plate 210, the first LED chip 220 is not displaced, and thus can be precisely attached to the first sub-pad group 131 aligned therewith.

When the voltage difference V periodically decreases from the second voltage difference B to the first voltage difference a, magnetic fields with opposite directions are generated between the positive pad 1311 and the negative pad 1312, and the time for the voltage difference V to decrease from the second voltage difference B to the first voltage difference a is set to be very short, so that the time for the first magnetic conductive layer 230 to be in the magnetic fields with opposite directions is very short, and the time for the first magnetic conductive layer 230 to be subjected to the magnetic forces with opposite directions is very short, so that the first LED chip 220 does not move due to the magnetic forces with opposite directions.

In some embodiments, a TFT (thin film transistor) layer is disposed on the second side of the substrate 120, the TFT layer is respectively connected to the pad group 130, the positive lead 150, and the negative lead 160, and the TFT layer is configured to selectively control the connection of the first sub-pad group 131 in the pad group 130 with the positive lead 150 and the negative lead 160 when a voltage is applied to the positive lead 150 and the negative lead 160, so that an electric field is generated between the positive pad 1311 and the negative pad 1312 of only the first sub-pad group 131 in the pad group 130, and a magnetic field is further generated, thereby preventing a magnetic field direction generated by other pad groups except the first sub-pad group 131 in the pad group 130 from affecting a magnetic field direction generated by the first sub-pad group 131.

In some embodiments, after the first electrode group 221 is attached to the corresponding first sub-pad group 131, the method further includes: the first electrode group 221, the first magnetic conductive layer 230, and the first sub-pad group 131 are bonded. Wherein the first electrode group 221, the first magnetic conductive layer 230, and the first sub-pad group 131 may be fusion-bonded into a whole by heating the first electrode group 221, the first magnetic conductive layer 230, and the first sub-pad group 131. For example, the bonding temperature is controlled to be 600 ℃ to 800 ℃, the first electrode group 221, the first magnetic conductive layer 230, and the first sub-pad group 131 are melted and fused at the bonding temperature, and the first electrode group 221, the first magnetic conductive layer 230, and the first sub-pad group 131 are bonded together by cooling the first electrode group 221, the first magnetic conductive layer 230, and the first sub-pad group 131.

Referring to fig. 9 to 10, fig. 9 to 10 are schematic views illustrating a process of separating the first LED chip 220 from the first transfer plate 210 according to an embodiment of the present disclosure. In some embodiments, a sacrificial layer 40 is disposed between the first LED chip 220 and the first transfer plate 210, and the peeling of the first LED chip 220 to be transferred from the first transfer plate 210 in the foregoing step S105 includes: as shown in fig. 9, the first transfer plate 210 is irradiated with laser light from the side of the first transfer plate 210 far from the first LED chip 220 to be transferred, the area of the laser light irradiated on the first transfer plate 210 coincides with the orthographic projection of the first LED chip 220 to be transferred on the first transfer plate 210, and the laser light removes the sacrificial layer 40 located between the first LED chip 220 and the first transfer plate 210, so that the first LED chip 220 is separated from the first transfer plate 210, and the result is shown in fig. 10.

In this embodiment, the first transfer plate 210 is a substrate made of a semiconductor material, and since the forbidden bandwidth of the sacrificial layer 40 is smaller than that of the substrate, when the substrate is irradiated with laser light having energy between the forbidden bandwidth of the sacrificial layer 40 and that of the substrate from the side of the substrate away from the sacrificial layer 40, the laser light passes through the substrate and is absorbed by the sacrificial layer 40, so that the sacrificial layer 40 is thermally decomposed, and the first LED chip 220 is separated from the substrate.

The substrate may be made of a semiconductor material such as sapphire or silicon carbide, and the sacrificial layer 40 may be a gallium nitride layer or an ion-doped gallium nitride layer.

In this embodiment, the sacrificial layer 40 positioned in the forward projection area of the first LED chip 220 to be transferred on the first transfer plate 210 is selectively irradiated with laser light, thereby selectively peeling the first LED chip 220 to be transferred from the substrate. In addition, in the embodiment, the first LED chip 220 grown on the substrate is directly transferred to the display backplane 100, compared to the conventional transfer technique in which the LED chip is transferred from the substrate to the display backplane through multiple transfers to the transient board, the transfer method provided in the embodiment reduces the number of transfers, and improves the transfer efficiency and yield.

In some other embodiments, the sacrificial layer 40 between the first LED chip 220 and the first transfer plate 210 is an adhesive layer, and the peeling of the first LED chip 220 to be transferred from the first transfer plate 210 in the foregoing step S105 includes: the first transfer plate 210 is irradiated with laser light from a side of the first transfer plate 210 away from the first LED chip 220 to be transferred, an area of the first transfer plate 210 irradiated with the laser light coincides with an orthographic projection of the first LED chip 220 on the first transfer plate 210, and an adhesive layer between the first LED chip 220 to be transferred and the first transfer plate 210 becomes low in viscosity under irradiation of the laser light, so that the first LED chip 221 can be separated from the first transfer plate 210. Wherein, the adhesive layer can be a photolysis layer. The first transfer plate 210 may be a glass plate.

In this embodiment, by selectively irradiating the adhesive layer located in the orthographic projection area of the first LED chip 220 to be transferred on the first transfer plate 210 with laser, the viscosity of the adhesive layer located between the first LED chip 220 to be transferred and the first transfer plate 210 is selectively reduced, so that the first LED chip 220 to be transferred can be selectively peeled off from the first transfer plate 210.

Referring to fig. 11 to 14 together, fig. 11 is a flowchart of a transfer method of an LED chip according to another embodiment of the present application, fig. 12 is a schematic cross-sectional view of a second transfer plate 310 according to the present application, fig. 13 is a schematic positional relationship between the second transfer plate 310 and the display back plate 100 after step S107 in fig. 11 is completed, and fig. 14 is a schematic positional relationship between the second LED chip 320 and the display back plate 100 after step S109 in fig. 11 is completed. As shown in fig. 13, in some embodiments, the pad group 130 further includes at least one second sub-pad group 132. As shown in fig. 11, after the first electrode group 221 is attached to the corresponding first sub-pad group 131, the method for transferring the LED chip further includes the following steps:

s106: providing a second transfer plate 310 as shown in fig. 12, wherein at least one second LED chip 320 is carried on the second transfer plate 310, a second magnetic conductive layer 330 covers a second electrode group 321 of the second LED chip 320, and a light emitting color of the second LED chip 320 is different from a light emitting color of the first LED chip 220.

S107: the second LED chip 320 is at least partially embedded in the adhesive layer 140, wherein the second LED chip 320 to be transferred is aligned with the corresponding second sub-pad group 132, resulting in fig. 13.

S108: an electrical signal is applied to each of the second sub-pad groups 132 to generate a magnetic field at the second side of the substrate 120.

S109: the second LED chip 320 to be transferred is peeled off from the second transfer plate 310, and the second magnetic conductive layer 330 drives the second LED chip 320 to move to the corresponding second sub-pad group 132 under the action of a magnetic force perpendicular to the direction of the substrate 120 until the second electrode group 321 is attached to the corresponding second sub-pad group 132, with the result shown in fig. 14.

In the transfer method of the LED chip provided in the embodiment of the application, because the first LED chip 220 is fixed on the side of the first sub-pad group 131 of the display back plate 100 away from the substrate 120 under the action of magnetic adsorption and adhesion, the process of transferring the second LED chip 320 to the display back plate 100 is not affected, and the problem of mutual interference when transferring LED chips with different light emitting colors respectively is avoided.

In some embodiments, as shown in fig. 12, the second LED chip 320 further includes a second epitaxy structure 322, and the second epitaxy structure 322 and the second electrode group 321 are sequentially stacked on the second transfer plate 310.

Here, the steps S108 and S109 may be performed simultaneously, that is, the second LED chip 320 to be transferred is peeled off from the second transfer plate 310 while applying an electrical signal to the second sub-pad group 132. Alternatively, step S108 precedes step S109, i.e. the magnetic field is generated on the second side of the substrate 120, and then the second LED chip 320 to be transferred is peeled off from the first transfer plate 310.

The method for peeling the second LED chip 320 to be transferred from the second transfer plate 310 may refer to the aforementioned method for peeling the first LED chip 220 from the first transfer plate 210, and is not described herein again.

In some embodiments, the second electrode group 321 also includes a positive electrode and a negative electrode, the second sub-pad group 132 also includes a positive electrode pad and a negative electrode pad, when the second electrode group 321 is attached to the corresponding second sub-pad group 132, the positive electrode of the second electrode group 321 is attached to the corresponding positive electrode pad of the second sub-pad group 132, and the negative electrode of the second electrode group 321 is attached to the negative electrode pad of the second sub-pad group 132. The materials of the positive electrode of the second electrode group 321, the negative electrode of the second electrode group 321, the positive electrode pad of the second sub-pad group 132, and the negative electrode pad of the second sub-pad group 132 may all be metal materials, such as gold, indium, tin, copper, nickel, and the like.

Specifically, the TFT layer is further configured to selectively control the connection of the second sub-pad group 132 of the pad group 130 with the positive lead 150 and the negative lead 160 when the second LED chip 320 is transferred to the display backplane 100, so that an electric field is generated only between the positive pad of the second sub-pad group 132 and the negative pad of the second sub-pad group 132 of the pad group 130, and a magnetic field is generated, thereby preventing a magnetic field direction generated by other sub-pad groups except the second sub-pad group 132 of the pad group 130 from affecting a magnetic field direction generated by the second sub-pad group 132.

Referring to fig. 15 to 18 together, fig. 15 is a flowchart of a transfer method of an LED chip according to still another embodiment of the present disclosure, fig. 16 is a schematic cross-sectional view of a third transfer plate 410 according to the present disclosure, fig. 17 is a schematic positional relationship between the third transfer plate 410 and the display back plate 100 after step S110 in fig. 15 is completed, and fig. 18 is a schematic positional relationship between the third LED chip 420 and the display back plate 100 after step S112 in fig. 15 is completed. As shown in fig. 17, in some embodiments, the pad group 130 further includes at least one third sub-pad group 133. As shown in fig. 15, after the second electrode group 321 is attached to the corresponding second sub-pad group 132, the method for transferring the LED chip further includes the following steps:

s110: providing a third transfer plate 410 as shown in fig. 16, wherein at least one third LED chip 420 is carried on the third transfer plate 410, a third electrode group 421 of the third LED chip 420 is covered with a third magnetic conductive layer 430, and the light emitting color of the third LED chip 420 is different from the light emitting color of the first LED chip 220 and the light emitting color of the second LED chip 320.

S111: the third LED chip 420 is at least partially embedded in the adhesive layer 140, wherein the third LED chip 420 to be transferred is aligned with the corresponding third sub-pad set 133, resulting in the structure shown in fig. 17.

S112: an electric signal is applied to each of the third sub-pad groups 133 to generate a magnetic field at the second side of the substrate 120.

S113: the third LED chip 420 to be transferred is peeled off from the third transfer plate 410, and the third magnetic conductive layer 430 drives the third LED chip 420 to move to the corresponding third sub-pad group 133 under the action of a magnetic force in a direction perpendicular to the substrate 120 until the third electrode group 421 is attached to the corresponding third sub-pad group 133, with the result as shown in fig. 18.

Here, the steps S112 and S113 may be performed simultaneously, that is, the third LED chip 420 to be transferred is peeled off from the third transfer plate 410 while applying an electrical signal to the third sub-pad group 133. Alternatively, step S112 precedes step S113, that is, a magnetic field is generated on the second side of the substrate 120, and then the third LED chip 420 to be transferred is peeled off from the second transfer plate 410.

In some embodiments, as shown in fig. 16, the third LED chip 420 further includes a third epitaxial structure 422, and the third epitaxial structure 422 and the third electrode group 421 are sequentially stacked on the third transfer plate 410.

The method for peeling the third LED chip 420 to be transferred from the third transfer plate 410 may refer to the aforementioned method for peeling the first LED chip 220 from the first transfer plate 210, and is not described herein again.

In some embodiments, the third electrode group 421 also includes a positive electrode and a negative electrode, the third sub-pad group 133 also includes a positive electrode pad and a negative electrode pad, when the third electrode group 421 is attached to the corresponding third sub-pad group 133, the positive electrode of the third electrode group 421 is attached to the positive electrode pad of the third sub-pad group 133, and the negative electrode of the third electrode group 421 is attached to the negative electrode pad of the third sub-pad group 133. The materials of the positive electrode of the third electrode group 421, the negative electrode of the third electrode group 421, the positive electrode pad of the third sub-pad group 133, and the negative electrode pad of the third sub-pad group 133 may all be metal materials, such as gold, indium, tin, copper, nickel, and the like.

Specifically, the TFT layer is further configured to selectively control the connection of the third sub-pad group 133 in the pad group 130 with the positive lead 150 and the negative lead 160 when the third LED chip 420 is transferred to the display backplane 100, so that an electric field is generated only between the positive pad of the third sub-pad group 133 and the negative pad of the third sub-pad group 133 in the pad group 130, and a magnetic field is generated, thereby preventing a magnetic field direction generated by other pad groups except the third sub-pad group 133 in the pad group 130 from affecting a magnetic field direction generated by the third sub-pad group 133.

In some embodiments, after the first electrode group 221 is attached to the corresponding first sub-pad group 131, the second electrode group 321 is attached to the corresponding second sub-pad group bonding 132, and the third electrode group 421 is attached to the corresponding third sub-pad group 133, the method for transferring an LED chip further includes: the first electrode group 221 and the first magnetic conductive layer 230 are bonded to the first sub-pad group 131, and the second electrode group 321 and the second magnetic conductive layer 330 are simultaneously bonded to the second sub-pad group 132 and the third electrode group 421 and the third magnetic conductive layer 430 are simultaneously bonded to the third sub-pad group 133.

Specifically, the first electrode group 221, the first magnetic conductive layer 230, the first sub-pad group 131, the second electrode group 321, the second magnetic conductive layer 330, the second sub-pad group bonding 132, the third electrode group 421, the third magnetic conductive layer 430, and the third sub-pad group 133 may be heated at the same time, so that the first electrode group 221, the first magnetic conductive layer 230, and the first sub-pad group 131 are fused, the second electrode group 321, the second magnetic conductive layer 330, and the second sub-pad group bonding 132 are fused, the third electrode group 421, the third magnetic conductive layer 430, and the third sub-pad group 133 are fused, and the first electrode group 221, the first magnetic conductive layer 230, the first sub-pad group 131, the second sub-pad group 321, the second magnetic conductive layer 330, the second sub-pad group bonding 132, the third magnetic electrode group 421, the third magnetic conductive layer 430, and the third sub-pad group bonding 132 are cooled, so that the first magnetic conductive layer 221, the first magnetic conductive layer 230, the second sub-pad group bonding 132, the third magnetic conductive layer 421, the third sub-pad group 133, and the second sub-pad group bonding 132 are integrally bonded, and the third sub-pad group bonding pad group 133.

In the transfer method of the LED chip provided in the embodiment of the application, since the electrode group of the LED chip is adsorbed on the pad group of the display backplane 100, after the electrode group of the three-color LED chip is attached to the pad group of the display backplane 100, the electrode group of the three-color LED chip is bonded to the pad group of the display backplane 100 at the same time, compared with the prior art in which another single-color LED chip is transferred after the electrode group of the single-color LED chip is bonded to the pad group of the display backplane, damage to the LED chip due to multiple bonding is avoided, and the bonding material is prevented from being oxidized or damaged due to multiple bonding, so that the bonding between the electrode group and the pad group is poor.

The embodiment of the application also provides a display panel. The display panel comprises the display back plate 100 and at least one LED chip fixed on the display back plate 100, wherein the at least one LED chip is fixed on the display back plate 100 by using the aforementioned LED chip transfer method.

According to the display panel provided by the embodiment of the application, the LED chips are transferred by using the LED chip transfer method, and the display back plate 100 has a magnetic adsorption effect on the at least one LED chip and the adhesion force of the adhesion layer 140 on the at least one LED chip, so that when the at least one LED chip is peeled off from the transfer plate, the at least one LED chip cannot be displaced under the combined action of the magnetic force and the adhesion force, and can be accurately aligned and attached to the corresponding position of the display back plate 100, the transfer efficiency and the transfer yield are improved, and the manufacturing cost of the display panel is reduced.

It should be noted that for simplicity of description, the above-mentioned embodiments of the method are described as a series of acts, but those skilled in the art should understand that the present application is not limited by the described order of acts, as some steps may be performed in other orders or simultaneously according to the present application.

In the above embodiments, the descriptions of the respective embodiments have respective emphasis, and for parts that are not described in detail in a certain embodiment, reference may be made to related descriptions of other embodiments.

It is to be understood that the invention is not limited to the examples described above, but that modifications and variations may be effected thereto by those of ordinary skill in the art in light of the foregoing description, and that all such modifications and variations are intended to be within the scope of the invention as defined by the appended claims.

Claims (10)

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

providing a display back plate, wherein the display back plate comprises a magnetic shielding layer, a substrate, at least one pad group and an adhesion layer, the magnetic shielding layer is arranged on the first side of the substrate, the pad group is arranged on the second side of the substrate, the pad group comprises at least one first sub-pad group, the first side and the second side of the substrate are oppositely arranged, and the adhesion layer is arranged on the second side of the substrate and covers the pad group;

providing a first transfer plate, wherein at least one first LED chip is loaded on the first transfer plate, and a first magnetic conducting layer is covered on a first electrode group of the first LED chip;

at least partially embedding the first LED chip in the adhesion layer, wherein the first LED chip to be transferred is aligned with the corresponding first sub-pad set;

applying an electrical signal to each of the first sub-pad groups to generate a magnetic field at the second side of the substrate; and

and peeling the first LED chip to be transferred from the first transfer plate, wherein the first magnetic conducting layer drives the first LED chip to move to the corresponding first sub-bonding pad group under the action of magnetic force in the direction vertical to the substrate until the first electrode group is attached to the corresponding first sub-bonding pad group.

2. The transfer method of claim 1, wherein the first sub-pad groups include positive and negative pads, and the applying an electrical signal to each of the first sub-pad groups to generate a magnetic field on the second side of the substrate comprises:

and respectively applying a first electric signal and a second electric signal to the positive electrode bonding pad and the negative electrode bonding pad to form a voltage difference between the positive electrode bonding pad and the negative electrode bonding pad, and controlling the first electric signal and the second electric signal to periodically change the voltage difference so as to generate a magnetic field positioned on the second side of the substrate.

3. The transfer method of claim 2, wherein said controlling the first electrical signal and the second electrical signal such that the voltage difference varies periodically comprises:

controlling the first electrical signal and the second electrical signal such that the voltage difference periodically increases from a first voltage difference value to a second voltage difference value.

4. The transfer method of claim 1, wherein after the first electrode set is attached to the corresponding first sub-pad set, the method further comprises:

bonding the first electrode group, the first magnetic conductive layer and the first sub-pad group.

5. The transfer method according to claim 1, wherein a sacrificial layer is provided between the first LED chip and the first transfer plate, and the peeling of the first LED chip to be transferred from the first transfer plate comprises:

selectively irradiating a sacrificial layer located within an orthographic projection area of the first LED chip to be transferred on the first transfer plate with laser light.

6. The transfer method of claim 1, wherein the pad set further comprises at least one second sub-pad set, and after the first electrode set is attached to the corresponding first sub-pad set, the method further comprises:

providing a second transfer plate, wherein at least one second LED chip is loaded on the second transfer plate, a second magnetic conductive layer covers a second electrode group of the second LED chip, and the light emitting color of the second LED chip is different from that of the first LED chip;

at least partially embedding the second LED chip in the adhesion layer, wherein the second LED chip to be transferred is aligned with the corresponding second sub-pad set;

applying an electrical signal to each of the second sub-pad sets to generate a magnetic field at the second side of the substrate; and

and stripping the second LED chip to be transferred from the second transfer plate, wherein the second magnetic conducting layer drives the second LED chip to move to the corresponding second sub-bonding pad group under the action of magnetic force in the direction vertical to the substrate until the second electrode group is attached to the corresponding second sub-bonding pad group.

7. The transfer method of claim 6, wherein the set of pads further comprises at least one third set of sub-pads, the method further comprising, after the second set of electrodes is attached to the corresponding second set of sub-pads:

providing a third transfer plate, wherein at least one third LED chip is loaded on the third transfer plate, a third electrode group of the third LED chip is covered with a third magnetic conductive layer, and the light emitting color of the third LED chip is different from the light emitting colors of the first LED chip and the second LED chip;

at least partially embedding the third LED chip in the adhesion layer, wherein the third LED chip to be transferred is aligned with the corresponding third sub-pad set;

applying an electrical signal to each of the third sub-pad sets to generate a magnetic field at the second side of the substrate; and

and peeling the third LED chip to be transferred from the third transfer plate, wherein the third magnetic conducting layer drives the third LED chip to move to the corresponding third sub-bonding pad group under the action of a magnetic force in a direction vertical to the substrate until the third electrode group is attached to the corresponding third sub-bonding pad group.

8. The transfer method as claimed in claim 7, wherein the transfer method further comprises: bonding the first electrode set, the first magnetic conductive layer and the first sub-pad set, and simultaneously bonding the second electrode set, the second magnetic conductive layer and the second sub-pad set and bonding the third electrode set, the third magnetic conductive layer and the third sub-pad set.

9. The transfer method according to claim 2, wherein the first electrode group includes a positive electrode and a negative electrode, and the positive electrode is attached to the positive electrode pad and the negative electrode is attached to the negative electrode pad when the first electrode group is attached to the corresponding first sub-pad group.

10. A display panel, comprising a display back plate and at least one LED chip fixed on the display back plate, wherein the at least one LED chip is fixed on the display back plate by the transfer method of the LED chip according to any one of claims 1 to 9.

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