Mass transfer method

Abstract

A mass transfer method comprises: forming a plurality of protruding structures on a circuit backplane, wherein the protruding structures are arranged between two adjacent pads on the circuit backplane; bonding a light-emitting element on a temporary substrate to the pads; heating to melt the protruding structures to form a connection layer, wherein the connection layer fills the gap between two adjacent pads and fills at least part of the gap between two adjacent light-emitting elements; after the connection layer is subsequently solidified, the light-emitting element and the circuit backplane can be connected through the connection layer, so that the light-emitting element is subjected to two fixing forces, one is the bonding force of the pads, and the other is the connection force of the connection layer on the light-emitting element, thereby improving the fixing effect of the light-emitting element and the circuit backplane, so that the light-emitting element will not be removed with the temporary substrate, thereby ensuring that all light-emitting elements can be successfully transferred to the circuit backplane, thereby improving the yield.

Description

Technical Field

[0001] The present invention relates to the field of mass transfer technology, and in particular to a mass transfer method. Background Art

[0002] Micro-LED (Micro-light-emitting diode) has attracted widespread attention as a high-performance display device. It has become a new generation of display device with its excellent performance of high brightness, low power consumption and long life.

[0003] In the Micro-LED manufacturing process, how to achieve efficient mass transfer has become the key to the success of the technology, among which achieving stable bonding between Micro-LED and circuit backplane is an important part of mass transfer technology. Currently, the welding of light-emitting elements on the temporary substrate to the pads of the circuit backplane by welding materials mainly has the following problems: after the bonding is completed, during the process of removing the temporary substrate, due to the viscosity of the adhesive between the light-emitting elements and the temporary substrate, some light-emitting elements cannot be transferred to the circuit backplane, thus affecting the yield.

[0004] Therefore, how to ensure that the light-emitting element is completely transferred to the circuit backplane is an urgent problem to be solved. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the purpose of the present application is to provide a mass transfer method, aiming to solve the problem of completely transferring the light-emitting elements to the circuit backplane.

[0006] The present application provides a mass transfer method, comprising:

[0007] forming a plurality of protruding structures on the circuit backplane, wherein the protruding structures are arranged between two adjacent pads on the circuit backplane;

[0008] bonding the light emitting element on the transient substrate to the pad;

[0009] The protruding structure is melted by heating to form a connecting layer, which fills the gap between two adjacent pads and fills at least part of the gap between two adjacent light-emitting elements. The connecting layer is solidified to connect the light-emitting element to the circuit backplane through the connecting layer.

[0010] By forming a raised structure, the light-emitting element is bonded to the pad, and the raised structure melts to form a connecting layer. After the connecting layer is solidified, it connects the circuit backplane and the light-emitting element, so that the light-emitting element is subjected to two fixing forces, one is the bonding force of the pad, and the other is the connecting force of the connecting layer on the light-emitting element. This improves the fixing effect of the light-emitting element and the circuit backplane, so that the light-emitting element will not be removed when the temporary substrate is removed, thereby ensuring that all light-emitting elements can be successfully transferred to the circuit backplane, which can improve the yield.

[0011] In one embodiment, the melting temperature of the protruding structure is 70° C.-100° C. In the process of heating the solder, when the temperature reaches the melting temperature of the protruding structure, the protruding structure melts first to form a connection layer surrounding the pad and the light-emitting element. At this time, the connection layer wraps around the periphery of the solder. When the temperature continues to rise to melt the solder, the solder is confined to flow in a fixed space due to the wrapping of the connection layer, which can prevent the solder from overflowing and connecting with other pads to cause a short circuit.

[0012] In one embodiment, in a direction perpendicular to the pad surface of the circuit backplane, the height of the protruding structure is greater than the height of the pad and less than the total height of the pad and the light-emitting element. This allows the protruding structure to be connected to the light-emitting element after melting, and when bonding the light-emitting element to the pad, it is possible to prevent the protruding structure from being too high so that the light-emitting element cannot contact the pad.

[0013] In one embodiment, the protruding structure is in a table shape, the area of ​​the surface of the protruding structure connected to the circuit back plate is not less than the area of ​​the end surface facing away from the circuit back plate, and the longitudinal section of the protruding structure is in a polygonal shape, wherein each edge of the polygon is a straight line or a combination of a straight line and a curve. The protruding structure is set to be in a table shape, and the area of ​​the surface connected to the circuit back plate is larger than the area of ​​the end surface facing away from the circuit back plate, so that two adjacent protruding structures can form a larger opening angle, which is convenient for the light-emitting element to extend into and bond with the pad, and avoids interference.

[0014] In one embodiment, the plurality of pads form a plurality of groups, each group of pads includes a first pad and a second pad, a group of pads is bonded to a light emitting element, and the protruding structure is arranged between two adjacent groups of pads. The protruding structure is arranged between two adjacent groups of pads so that the protruding structure has enough space for arrangement and does not interfere with the light emitting element.

[0015] In one embodiment, forming a plurality of the protruding structures on the circuit backplane includes: coating a glue layer on the circuit backplane, the glue layer covering the plurality of pads; and patterning the glue layer to form the plurality of the protruding structures. The process of forming the plurality of protruding structures by patterning the glue layer is simple and easy to implement.

[0016] In one embodiment, patterning the adhesive layer includes: exposing, developing and etching the adhesive layer to remove the adhesive layer on the pads, retaining the adhesive layer between the plurality of pads, and forming the protruding structure. The process of coating the adhesive layer, removing part of the adhesive layer, and retaining part of the adhesive layer to form the protruding structure is simple and easy to implement.

[0017] In one embodiment, the light emitting element is bonded to the pad by heating, and during the bonding process of the light emitting element and the pad, the protruding structure is heated and melted. The protruding structure is melted during the bonding process of the light emitting element and the pad, which can save the step of heating to melt the protruding structure, save labor time, and avoid damage to the light emitting element and other structures caused by multiple heating.

[0018] In one embodiment, the mass transfer method further includes: solidifying the connection layer and peeling off the temporary substrate. When the protruding structure melts into the connection layer, and the solder bonds the light-emitting element to the pad, the connection layer is solidified. Since the material of the connection layer has adhesiveness, the solidified connection layer can firmly fix the light-emitting element on the circuit backplane. In addition, the bonding force between the pad and the light-emitting element can ensure that when the temporary substrate is peeled off, the light-emitting element will not be peeled off. Peel off the temporary substrate to facilitate subsequent packaging.

[0019] In one embodiment, the mass transfer method further includes: forming an encapsulation layer on the connection layer, wherein the encapsulation layer encapsulates the plurality of light-emitting elements. By first forming the connection layer, the connection layer fixes the light-emitting element to the circuit backplane, and then forming the encapsulation layer on the connection layer, when the encapsulation layer squeezes the light-emitting element, the light-emitting element will not be offset due to the fixing effect of the connection layer on the light-emitting element, thereby improving the yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A flowchart of a mass transfer method according to an embodiment;

[0021] Figure 2 A structural diagram of a step of a mass transfer method according to an embodiment;

[0022] Figure 3 A structural diagram of a step of a mass transfer method according to an embodiment;

[0023] Figure 4a A structural diagram of a step of a mass transfer method according to an embodiment;

[0024] Figure 4b A structural diagram of a step of a mass transfer method according to another embodiment;

[0025] Figure 4cA structural diagram of a step of a mass transfer method according to another embodiment;

[0026] Figure 4d A structural diagram of a step of a mass transfer method according to another embodiment;

[0027] Figure 4e A structural diagram of a step of a mass transfer method according to another embodiment;

[0028] Figure 4f A structural diagram of a step of a mass transfer method according to another embodiment;

[0029] Figure 4g A structural diagram of a step of a mass transfer method according to another embodiment;

[0030] Figure 4h A structural diagram of a step of a mass transfer method according to another embodiment;

[0031] Figure 5 A structural diagram of a step of a mass transfer method according to an embodiment;

[0032] Figure 6 A structural diagram of a step of a mass transfer method according to an embodiment;

[0033] Figure 7 A structural diagram of a step of a mass transfer method according to an embodiment;

[0034] Figure 8 A structural diagram of a step of a mass transfer method according to an embodiment.

[0035] Description of reference numerals:

[0036] 10-circuit backplane;

[0037] 20- pad, 21- first pad, 22- second pad;

[0038] 30-adhesive layer, 31-convex structure, 31'-convex structure, 35-connecting layer;

[0039] 40-transient substrate;

[0040] 50-adhesive layer;

[0041] 60-light emitting element, 61-epitaxial, 62-first electrode, 63-second electrode;

[0042] 70-Encapsulation layer. DETAILED DESCRIPTION

[0043] In order to facilitate the understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present application are given in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thoroughly and comprehensively understood.

[0044] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0045] Currently, there are the following main problems in welding the light-emitting elements on the temporary substrate to the pads of the circuit backplane through soldering materials: after the bonding is completed, during the process of removing the temporary substrate, due to the adhesion of the glue between the light-emitting elements and the temporary substrate, some light-emitting elements will be removed together, resulting in some light-emitting elements failing to be transferred to the circuit backplane, thereby affecting the yield.

[0046] Therefore, how to ensure that the light-emitting element is completely transferred to the circuit backplane is an urgent problem to be solved.

[0047] Based on this, the present application hopes to provide a solution that can solve the above-mentioned technical problems, the details of which will be described in the subsequent embodiments.

[0048] Please refer to Figures 1 to 8 , the present application embodiment provides a mass transfer method, including:

[0049] S100 , forming a plurality of protruding structures 31 on the circuit back plate 10 , wherein the protruding structures 31 are disposed between two adjacent pads 20 on the circuit back plate 10 .

[0050] S200, bonding the light emitting element 60 on the temporary substrate 40 to the pad 20;

[0051] S300 , heating to melt the protruding structure 31 to form a connecting layer 35 , wherein the connecting layer 35 fills the gap between two adjacent pads 20 and fills at least a portion of the gap between two adjacent light emitting elements 60 .

[0052] After the connection layer 35 is cured, the cured connection layer 35 can connect the light emitting element 60 and the circuit backplane 10. According to the material of the connection layer 35, the connection layer 35 can be cured by natural cooling, accelerated cooling, or heating, etc., without any specific limitation.

[0053] In the present embodiment, the light-emitting element 60 is bonded to the pad 20 by forming a protruding structure 31, and the protruding structure 31 is melted to form a connecting layer 35. After the connecting layer 35 is solidified, it connects the circuit backplane 10 and the light-emitting element 60, so that the light-emitting element 60 is subjected to two fixing forces, one is the bonding force of the pad 20, and the other is the connecting force of the connecting layer 35 on the light-emitting element 60, thereby improving the fixing effect of the light-emitting element 60 and the circuit backplane 10, so that when the temporary substrate 40 is removed, the light-emitting element 60 will not be removed, thereby ensuring that all the light-emitting elements 60 can be successfully transferred to the circuit backplane 10, which can improve the yield.

[0054] For details, please refer to 2 and Figure 5 , a plurality of pads 20 are formed on the circuit backplane 10. The circuit backplane 10 may be a printed circuit board having a driving circuit trace thereon, the driving circuit trace being connected to the plurality of pads 20, and being able to supply power to the pads 20, so that the light-emitting element 60 subsequently bonded to the pads 20 emits light. The light-emitting element 60 is specifically a Micro-LED chip, which can be divided into a red light-emitting element, a green light-emitting element, a blue light-emitting element, etc. according to the light-emitting color. The specific structure of the light-emitting element 60 includes an epitaxial wafer 61 and a first electrode 62 and a second electrode 63 connected to the epitaxial wafer 61.

[0055] Please refer to Figure 2 and Figure 5 The plurality of pads 20 include a plurality of groups, each group of pads 20 includes a first pad 21 and a second pad 22, and a group of pads 20 is used to bond with a light emitting element 60. Specifically, the first electrode 62 of the light emitting element 60 is bonded with the first pad 21, and the second electrode 63 is bonded with the second pad 22. During bonding, solder is usually placed on the pad 20, and the composition of the solder is, for example, In (indium). After the electrode of the light emitting element 60 contacts the solder, the solder is melted by heating, and the electrode and the pad 20 are welded and fixed.

[0056] Please refer to Figure 2 The first pads 21 and the second pads 22 in each group of pads 20 are spaced apart by a first spacing W1 , and two adjacent groups of pads 20 are spaced apart by a second spacing W2 , and the second spacing W2 is greater than the first spacing W1 .

[0057] Optional, please refer to Figure 4a The protruding structure 31 is disposed between two adjacent groups of pads 20 .

[0058] The protruding structure 31 is disposed between two adjacent groups of pads 20 , so that the protruding structure 31 has enough space for arrangement and will not interfere with the light emitting element 60 .

[0059] Optional, please refer to Figure 4bA protruding structure 31' may also be provided between the first pad 21 and the second pad 22 in the same pad group. In this case, the height of the protruding structure 31' should not exceed the height of the first pad 21 and the second pad 22 relative to the circuit backplane 10 (e.g. Figure 4b (as shown in H2).

[0060] Please refer to Figure 4a and Figure 5 , the height H1 of the raised structure 31 is greater than the height H2 of the pad 20, and is less than the total height (H2+H3) of the pad 20 and the light-emitting element 60. With such a configuration, the raised structure 31 can be connected to the light-emitting element 60 after melting, and when the light-emitting element 60 is bonded to the pad 20, it can be prevented that the raised structure 31 is too high so that the light-emitting element 60 cannot contact the pad 20. Among them, the height H3 of the light-emitting element 60 is the total height of the first electrode 62 or the second electrode 63 and the epitaxial wafer 61. The above heights are all dimensions perpendicular to the pad surface of the circuit backplane 10. The pad surface may refer to the surface of the circuit backplane 10 connected to the pad 20, or may refer to the surface of the pad 20 facing away from the circuit backplane 10. That is, Figure 4a The vertical dimension of the medium viewing angle.

[0061] Please refer to Figure 4a to Figure 4h The raised structure 31 is in a table shape, the area of ​​the surface of the raised structure 31 connected to the circuit back plate 10 is not less than the area of ​​the end surface facing away from the circuit back plate 10, and the shape of the longitudinal section of the raised structure 31 is a polygon, wherein each edge of the polygon is a straight line or a combination of a straight line and a curve. The raised structure 31 is set to be in a table shape, and the area of ​​the surface connected to the circuit back plate 10 is larger than the area of ​​the end surface facing away from the circuit back plate 10, so that two adjacent raised structures 31 can form a larger opening angle, which is convenient for the light emitting element 60 to extend and bond with the pad 20, and avoid interference.

[0062] Optional, please refer to Figure 4a and Figure 4b The shape of the longitudinal section of the protruding structure 31 is a trapezoid, the lower bottom of the trapezoid is connected to the circuit back plate 10, and the upper bottom of the trapezoid faces away from the circuit back plate 10. The protruding structure 31 with a trapezoidal longitudinal section can make two adjacent protruding structures 31 have a larger opening angle, which is convenient for the light emitting element 60 to extend and bond with the pad 20, avoiding interference. In this embodiment, the manufacturing process of the protruding structure 31 can adopt any feasible process.

[0063] Optional, please refer to Figure 4c The shape of the longitudinal section of the protruding structure 31 may also be a rectangle.

[0064] Optional, please refer to Figure 4d The shape of the longitudinal section of the protruding structure 31 may also be a triangle.

[0065] Optional, please refer to Figure 4e The shape of the longitudinal section of the protruding structure 31 can also be a trapezoid with arcs on both sides, wherein the upper base and the lower base of the trapezoid are straight lines and the waists on both sides are concave arcs.

[0066] Optional, please refer to Figure 4f The shape of the longitudinal section of the protruding structure 31 can also be a trapezoid with two side waists being arcs, wherein the upper base and the lower base of the trapezoid are straight lines, and the two side waists are convex arcs.

[0067] Optional, please refer to Figure 4g The shape of the longitudinal section of the protruding structure 31 may also be a triangle with two sides being arcs, wherein the side connecting the triangle and the circuit back plate 10 is a straight line, and the other two sides are concave arcs.

[0068] Optional, please refer to Figure 4g The shape of the longitudinal section of the protruding structure 31 may also be a triangle with two sides being arc lines, wherein the side connecting the triangle and the circuit back plate 10 is a straight line, and the other two sides are convex arc lines.

[0069] Above Figure 4a to Figure 4h The patterning of the protruding structure 31 in various shapes can be achieved by adjusting the light transmittance of the mask, adjusting the etching power, temperature, etching gas composition and etching time, etc.

[0070] Optional, above Figure 4a to Figure 4h The cross-sectional shape of the protrusion structure 31 can be rectangular, circular, etc., without specific limitation.

[0071] In one embodiment, please refer to Figures 1 to 4a In step S100, a plurality of protruding structures 31 are formed on the circuit back plate 10, including:

[0072] Please refer to Figure 2 and Figure 3 , coating an adhesive layer 30 on the circuit back plate 10, wherein the adhesive layer 30 covers the plurality of pads 20;

[0073] Please refer to Figure 3 and Figure 4a , patterning the adhesive layer 30 to form a plurality of protruding structures 31 .

[0074] In this embodiment, the adhesive layer 30 is made of an adhesive material. The thickness of the adhesive layer 30 is the height H1 of the protruding structure 31 formed later. The adhesive layer 30 covers the pad 20, so that the height H1 of the protruding structure 31 can be greater than the height H2 of the pad 20, so that the protruding structure 31 can connect the light-emitting element 60 and the circuit backplane 10 after melting. The patterned adhesive layer 30 is used to form multiple protruding structures 31, and the process is simple and easy to implement.

[0075] In one embodiment, please refer to Figure 3 and Figure 4a , the patterned adhesive layer 30 comprises:

[0076] The glue layer 30 is etched by exposure, development and etching to remove the glue layer 30 on the pads 20 and retain the glue layer 30 in the gaps between the plurality of pads 20 to form a protruding structure 31 .

[0077] Optionally, the main process of forming the protrusion structure 31 may include:

[0078] A layer of photoresist is coated on the glue layer 30, and the photoresist is irradiated by light through a mask, and then the photoresist is developed, so that the illuminated part of the photoresist is retained and the unilluminated part is removed (or the illuminated part is removed and the unilluminated part is retained) to expose the glue layer 30, and then the exposed part of the glue layer 30 is etched, and the photoresist is subsequently removed to obtain the protruding structure 31. The etching can specifically adopt a plasma etching process.

[0079] Optionally, the protruding structure 31 may be obtained by directly exposing and developing the adhesive layer 30 and then etching the adhesive layer 30 .

[0080] Since a group of pads 20 includes a first pad 21 and a second pad 22, and the first pad 21 and the second pad 22 are spaced apart by a first spacing W1, when the adhesive layer 30 is applied, the adhesive layer 30 simultaneously fills the gap between the first pad 21 and the second pad 22 in a group of pads 20, and the gap between two adjacent groups. When the adhesive layer 30 is removed, the adhesive layer 30 covering the pads 20 and the adhesive layer 30 at the gap between the first pad 21 and the second pad 22 in a group of pads 20 are removed simultaneously, while the adhesive layer 30 at the gap between two adjacent groups of pads 20 is retained.

[0081] In this embodiment, the protruding structure 31 is formed by coating the adhesive layer 30 , removing part of the adhesive layer 30 , and retaining part of the adhesive layer 30 . The process is simple and easy to implement.

[0082] In one embodiment, please refer to Figure 4a and Figure 5 In step S200, bonding the light emitting element 60 on the temporary substrate 40 to the pad 20 may include:

[0083] Coating an adhesive layer 50 on the temporary substrate 40;

[0084] Bonding the temporary substrate 40 and the adhesive layer 50 to the plurality of light emitting elements 60 on the growth substrate (not shown);

[0085] The temporary substrate 40 transfers the plurality of light emitting elements 60 from the growth substrate onto the circuit backplane 10. After the light emitting elements 60 are aligned with the pads 20, the temporary substrate 40 and the circuit backplane 10 are brought close to each other so that the light emitting elements 60 are in contact with the pads 20.

[0086] The heating causes the solder on the pad 20 to be fixedly bonded to the electrode of the light emitting element 60 by soldering.

[0087] The growth substrate and the temporary substrate 40 can both be glass substrates.

[0088] Please refer to Figure 1 , Figure 5 and Figure 6 In step S300, the light emitting element 60 and the pad 20 are bonded by heating, and the protruding structure 31 is heated and melted during the bonding process of the light emitting element 60 and the pad 20. Since the light emitting element 60 and the pad 20 need to be heated to melt the solder on the pad 20 to fix the light emitting element 60, in this embodiment, the protruding structure 31 is melted during the bonding process of the light emitting element 60 and the pad 20, which can save the step of heating to melt the protruding structure 31, save labor time, and avoid damage to the light emitting element 60 and other structures caused by multiple heating.

[0089] Specifically, the material of the solder can be set to In, whose melting temperature is about 180°C, and the material of the protruding structure 31 can be set to a low melting point glue material, such as the low-temperature black glue of the Hans packaging glue series, whose melting temperature is about 70°C-100°C. In the process of heating the solder, when the temperature reaches the melting temperature of the protruding structure 31, the protruding structure 31 melts first to form a connecting layer 35 surrounding the pad 20 and the light-emitting element 60. At this time, the connecting layer 35 is wrapped around the periphery of the solder. When the temperature continues to rise to melt the solder, due to the wrapping of the connecting layer 35, the solder is confined to flow in a fixed space, which can prevent the solder from overflowing and connecting with other pads 20 to cause a short circuit.

[0090] In combination with the aforementioned height H1 of the protruding structure 31 being greater than the height H2 of the pad 20, and less than the total height (H2+H3) of the pad 20 and the light-emitting element 60, in addition, the light-emitting element 60 includes an epitaxial layer 61, a first electrode 62, and a second electrode 63. In this embodiment, the thickness of the connecting layer 35 formed after the protruding structure 31 is melted is greater than the height H2 of the pad 20, less than the total height (H2+H3) of the pad 20 and the light-emitting element 60, and also less than the height of the protruding structure 31. Optionally, the connecting layer 35 is at least partially connected to the epitaxial layer 61, that is, the thickness of the connecting layer 35 is greater than the total height of the pad 20 and the first electrode 62 (or the second electrode 63). Optionally, the connecting layer 35 may also only connect the first electrode 62 and the second electrode 63, and have no connection with the epitaxial layer 61, that is, the thickness of the connecting layer 35 is less than the total height of the pad 20 and the first electrode 62 (or the second electrode 63).

[0091] Please refer to Figure 6 and Figure 7 , the mass transfer method of the present application also includes:

[0092] The connection layer 35 is cured, and the temporary substrate 40 and the adhesive layer 50 are peeled off.

[0093] When the protruding structure 31 is melted into the connection layer 35, and the solder bonds and fixes the light emitting element 60 and the pad 20, the connection layer 35 is solidified. Since the material of the connection layer 35 is adhesive, the solidified connection layer 35 can firmly fix the light emitting element 60 on the circuit back plate 10. In addition, the bonding force between the pad 20 and the light emitting element 60 can ensure that when the temporary substrate 40 and the adhesive layer 50 are peeled off, the light emitting element 60 will not be peeled off. The temporary substrate 40 and the adhesive layer 50 are peeled off to facilitate subsequent packaging.

[0094] In one embodiment, please refer to Figure 7 and Figure 8 , the mass transfer method of the present application also includes:

[0095] The encapsulation layer 70 is formed on the connection layer 35 , and the encapsulation layer 70 wraps the plurality of light emitting elements 60 .

[0096] The encapsulation layer 70 is used to encapsulate the plurality of light emitting elements 60 to protect the light emitting elements 60. The process for forming the encapsulation layer 70 may adopt any feasible process and is not limited here. The material of the encapsulation layer 70 should be a transparent material so that the light emitted by the light emitting element 60 can pass through. The material of the encapsulation layer 70 and the connecting layer 35 may be the same.

[0097] In the existing process, after the light emitting element 60 is bonded to the pad 20, during packaging, since there is no connection layer 35 to fix the light emitting element 60, the packaging layer 70 will squeeze the light emitting element 60, causing the light emitting element 60 to shift relative to the circuit backplane 10, affecting the yield.

[0098] In this embodiment, a connection layer 35 is first formed to fix the light-emitting element 60 to the circuit backplane 10, and then a packaging layer 70 is formed on the connection layer 35. When the packaging layer 70 squeezes the light-emitting element 60, the light-emitting element 60 will not be offset due to the fixing effect of the connection layer 35 on the light-emitting element 60, thereby improving the yield.

[0099] It should be understood that the application of the present invention is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A mass transfer method, characterized in that: include: forming a plurality of protruding structures on the circuit backplane, wherein the protruding structures are arranged between two adjacent pads on the circuit backplane; bonding the light emitting element on the transient substrate to the pad; The protruding structure is melted by heating to form a connection layer, and the connection layer fills the gap between two adjacent pads and fills at least part of the gap between two adjacent light-emitting elements.

2. The method for mass transfer according to claim 1, wherein: The melting temperature of the protrusion structure is 70°C-100°C.

3. The mass transfer method according to claim 1, wherein: In a direction perpendicular to the pad surface of the circuit backplane, the height of the protruding structure is greater than the height of the pad and less than the total height of the pad and the light emitting element.

4. The method for mass transfer according to claim 1, wherein: The raised structure is in the shape of a table, the area of ​​the surface of the raised structure connected to the circuit back plate is not less than the area of ​​the end surface facing away from the circuit back plate, and the shape of the longitudinal section of the raised structure is a polygon, wherein each side of the polygon is a straight line or a combination of a straight line and a curve.

5. The mass transfer method according to claim 1, wherein: The plurality of pads form a plurality of groups, each group of pads comprises a first pad and a second pad, a group of pads is bonded to a light emitting element, and the protruding structure is arranged between two adjacent groups of pads.

6. The method for mass transfer according to any one of claims 1 to 5, characterized in that: A plurality of protruding structures are formed on the circuit backplane, including: Coating a glue layer on the circuit backplane, wherein the glue layer covers the plurality of pads; The adhesive layer is patterned to form a plurality of protruding structures.

7. The method for mass transfer according to claim 6, wherein: Patterning the glue layer, comprising: The glue layer is etched by exposure, development and removal to remove the glue layer on the pads and retain the glue layer between two adjacent pads to form the protruding structure.

8. The method for mass transfer according to any one of claims 1 to 5, characterized in that: The light emitting element is bonded to the pad by heating. During the bonding process of the light emitting element and the pad, the protruding structure is heated and melted.

9. The method for mass transfer according to any one of claims 1 to 5, characterized in that: The mass transfer method further includes: The connecting layer is cured and the temporary substrate is peeled off.

10. The mass transfer method according to claim 9, wherein: The mass transfer method further includes: A packaging layer is formed on the connection layer, and the packaging layer encapsulates the plurality of light emitting elements.

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