Patent Publication Number: US-2021193896-A1

Title: Method for manufacturing side wire for substrate and substrate structure

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority of Chinese patent application No. 201910285864.5, filed on Apr. 10, 2019, the content of which is incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     The present disclosure relates to the field of display technologies, and in particular to a method for manufacturing a side wire for a substrate and a substrate structure. 
     BACKGROUND 
     A structure of a relevant micro light emitting diode (Micro LED) display substrate may include: a substrate, an array of Micro LEDs arranged on a top surface of the substrate, and a flexible printed circuit board bound on a bottom surface of the substrate. A line on the top surface of the substrate is connected to a line on the bottom surface of the substrate via a line on a side surface of the substrate. Typically, a length-to-width ratio (i.e., aspect ratio) of the side surface of the substrate is relatively large and a width of the side surface of the substrate is relatively small, and thus it is not suitable for forming a line on the side surface of the substrate by using a process such as a photolithography process. 
     SUMMARY 
     Embodiments of the present disclosure provide a method for manufacturing a side wire for a substrate and a substrate structure. 
     According to a first aspect of the present disclosure, there is provided a method for manufacturing a side wire for a substrate, the method including: 
     Forming a plurality of first pattern structures on a side surface of the substrate, wherein a gap between any adjacent two of the plurality of first pattern structures connects a top surface and a bottom surface of the substrate to each other; 
     Forming a conductive material film covering the side surface of the substrate; and 
     Removing the plurality of first pattern structures and a portion of the conductive material film attached on the plurality of first pattern structures, and maintaining a portion of the conductive material film located between any adjacent two of the plurality of first pattern structures as the side wire. 
     In an embodiment, the forming a plurality of first pattern structures on a side surface of the substrate includes: 
     Forming a plurality of first pattern preliminary structures on the side surface of the substrate by using a predetermined ink, wherein a gap between any adjacent two of the plurality of first pattern preliminary structures connects the top surface and the bottom surface of the substrate to each other, and the predetermined ink includes a first solvent and a self-assembly material; and 
     Removing the first solvent in the predetermined ink to cause the self-assembly material to combine into a unitary structure so as to obtain the plurality of first pattern structures. 
     In an embodiment, the removing the plurality of first pattern structures and a portion of the conductive material film attached on the plurality of first pattern structures includes: removing the self-assembly material by using a second solvent. 
     In an embodiment, both ends of each of the plurality of first pattern structures extend to an edge region of the top surface of the substrate and an edge region of the bottom surface of the substrate, respectively, and both ends of the portion of the conductive material film located between any adjacent two of the first pattern structures extend to the edge region of the top surface of the substrate and the edge region of the bottom surface of the substrate, respectively. 
     In an embodiment, the self-assembly material includes colloidal microspheres, and the colloidal microspheres include polystyrene microspheres. 
     In an embodiment, a mass percentage of the colloidal microspheres in the predetermined ink is between 5% and 30%. 
     In an embodiment, the removing the first solvent in the predetermined ink to cause the self-assembly material to combine into a unitary structure includes: 
     Evaporating the first solvent to cause the colloidal microspheres to be attached to the substrate; and 
     Drying the colloidal microspheres at a preset temperature to combine the colloidal microspheres into the unitary structure. 
     In an embodiment, the forming a plurality of first pattern preliminary structures on the side surface of the substrate by using a predetermined ink includes: letting the predetermined ink on the substrate stand still for a preset time. 
     In an embodiment, prior to forming the plurality of first pattern structures, the method further includes: 
     Attaching protective films onto the top surface and the bottom surface of the substrate, respectively, wherein a boundary of the protective film on the top surface of the substrate is in contact with an outer contour of the edge region of the top surface of the substrate, and a boundary of the protective film on the bottom surface of the substrate is in contact with an outer contour of the edge region of the bottom surface of the substrate, respectively. 
     In an embodiment, the side wire has a generally U-shape, and an opening of the U-shape is directed toward the side surface of the substrate on which the plurality of first pattern structures are formed. 
     In an embodiment, a diameter of each of the polystyrene microspheres is between 50 nm and 300 nm. 
     In an embodiment, the self-assembly material includes polystyrene microspheres, and the preset time is between 2 mins and 10 mins. 
     In an embodiment, the first solvent is selected from a group consisting of carbon tetrachloride, dichloroethane, chloroform, tetrahydrofuran, nitrobenzene, toluene, and carbon disulfide. 
     In an embodiment, the self-assembly material is dissolved in the second solvent. 
     In an embodiment, the second solvent is trichlorotoluene. 
     In an embodiment, the conductive material film is formed by a process of local sputtering or a process of printing a metal paste. 
     In an embodiment, each of the plurality of first pattern structures has a strip shape, and a thickness of the conductive material film is smaller than a thickness of each of the plurality of first pattern structures. 
     According to a second aspect of the present disclosure, there is provided a substrate structure, which is manufactured by the method according to any one of the embodiments of the first aspect of the present disclosure. 
     According to a third aspect of the present disclosure, there is provided a substrate structure, including: a substrate; and a side wire on a side surface of the substrate. Both ends of the side wire extend to an edge region of a top surface of the substrate and an edge region of a bottom surface of the substrate, respectively. 
     In an embodiment, the side wire has a substantially U-shape, and an opening of the U-shape is directed toward the side surface of the substrate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic flowchart of a method for manufacturing a side wire for a substrate according to an embodiment of the present disclosure; 
         FIG. 2  is a schematic flowchart of an example of a method for manufacturing a side wire for a substrate according to an embodiment of the present disclosure; 
         FIG. 3  is a schematic structural view of an intermediate state of a method for manufacturing a side wire for a substrate according to an embodiment of the present disclosure; 
         FIG. 4  is a schematic structural view of a finished stage of a method for manufacturing a side wire for a substrate according to an embodiment of the present disclosure; 
         FIG. 5  is a schematic cross-sectional view of the substrate structure shown in  FIG. 4  taken along line AA′; and 
         FIG. 6  is a schematic diagram showing that protective films are provided on the top and bottom surfaces of the substrate structure shown in  FIG. 5 , respectively. 
     
    
    
     DETAILED DESCRIPTION 
     To enable one of ordinary skill in the art to better understand technical solutions of the present disclosure, the present disclosure will be further described in detail below with reference to the accompanying drawings and exemplary embodiments. 
     The inventors of the present inventive concept have found that, in the related art, a wire (or a conductive line) is formed directly on a side of a substrate typically by using a transfer printing method. However, the wire formed by using the transfer printing method generally has a nonuniform thickness and is prone to breakage. 
     Embodiments of the present disclosure provide a method for manufacturing a side wire (i.e., side conductive line)  12  on a side surface of a substrate  1 , and the method may include the following steps S 11  to S 13 , as shown in  FIGS. 1 to 5 . 
     Firstly, in step S 11 , a plurality of first pattern structures  11  are formed on a side surface of the substrate  1  (e.g., a right side surface of the substrate  1  as shown in  FIG. 3 ). For example, each of the plurality of first pattern structures  11  has a strip shape (e.g., each of a portion of each first pattern structure  11  on the top surface of the substrate  1 , a portion of the first pattern structure  11  on the side surface of the substrate  1 , and a portion of each first pattern structure  11  on the bottom surface of the substrate  1  may have a strip shape), and a gap between any adjacent two of the plurality of first pattern structures  11  connects the top surface (e.g., the upper surface in  FIG. 3 ) and the bottom surface (e.g., the lower surface in  FIG. 3 ) of the substrate  1  together. A material of each of the plurality of first pattern structures  11  should be a material that can be removed in a subsequent process. Each of the plurality of first pattern structures  11  is located at a position where the side wire  12  is not desired to be formed. The position of the gap between any adjacent two of the plurality of first pattern structures  11  is a position where it is desired to form the side wire  12 . For example, each of the plurality of first pattern structures  11  covers a portion of the top surface of the substrate  1 , a portion of the side surface (e.g., the right side surface in  FIG. 3 ) of the substrate  1 , and a portion of the bottom surface of the substrate  1 . In other words, each of the plurality of first pattern structures  11  has a substantially U-shape (e.g., an orthogonal projection of each of the plurality of first pattern structures  11  on a plane perpendicular to the side surface of the substrate  1  on which the first pattern structure  11  is located has a substantially U-shape), and an opening of the U-shape is proximal to (or directed to) the side surface of the substrate  1  on which the plurality of first pattern structures  11  are formed. Each of the portions of each first pattern structure  11  located on the top surface of the substrate  1 , on the side surface of the substrate  1 , and on the bottom surface of the substrate  1  may be a parallelogram (e.g., a rectangle). However, the present disclosure is not limited thereto, it is feasible as long as each of the plurality of first pattern structures  11  covers a portion of the top surface of the substrate  1 , a portion of a side surface (e.g., the right side surface in  FIG. 3 ) of the substrate  1 , and a portion of the bottom surface of the substrate  1 , and has a uniform thickness (i.e., a size in a direction perpendicular to the side surface or the top surface of the substrate  1 ). Further, an aspect ratio of each of the plurality of first pattern structures  11  is not particularly limited. Further, a distance between any adjacent two of the plurality of first pattern structures  11  may be equal to a width of the side wire  12  to be formed between the adjacent two of the plurality of first pattern structures  11 . 
     Then, in step S 12 , a conductive material film is formed on the side surface to cover the side surface. For example, a large portion of the conductive material film is located in the gap between any adjacent two of the plurality of first pattern structures  11 , and a small portion of the conductive material film is attached on the adjacent two of the plurality of first pattern structures  11 . It should be noted that, a thickness of the conductive material film should be at least smaller than the thickness of each of the adjacent two of the plurality of first pattern structures  11 , such that the conductive material in the gap between any adjacent two of the plurality of first pattern structures  11  and the conductive material on the adjacent two of the plurality of first pattern structures  11  are not connected together, thereby facilitating the formation of the final side wire  12 . In order to prevent the conductive material in the gap between any adjacent two of the plurality of first pattern structures  11  and the conductive material on the adjacent two of the plurality of first pattern structures  11  from being connected to each other, one of ordinary skill in the art may determine a difference between the thickness of the conductive material film and the thickness of each first pattern structure  11  by an experiment in advance. 
     Finally, in step S 13 , the plurality of first pattern structures  11  and the portions of the conductive material film that are attached to the plurality of first pattern structures  11  are removed from the substrate  1 , and the portions of the conductive material film that are located between any adjacent two of the plurality of first pattern structures  11  are maintained on the substrate  1  as side wires  12 . As each of the plurality of first pattern structures  11  is removed, the portion of the conductive material film attached onto each of the first pattern structures  11  is also removed together therewith. The portion of the conductive material film between any adjacent two of the plurality of first pattern structures  11  is left to form the side wire  12  on the side surface of the substrate  1 . 
     In the prior art, a transfer printing process is generally used to manufacture a conductive material film on a side surface of a substrate, and a thickness of the manufactured conductive material film has poor uniformity. In the method of the present disclosure, for example, the conductive material film is manufactured by using a process of local sputtering or a process of printing a metal paste, and the quality of the manufactured entire conductive material film is higher than that of a conductive material film formed by using the transfer printing process. Thus, the quality of the side wire  12  formed by the remaining conductive material film is also better than that of a side wire formed by using the transfer printing process. 
       FIG. 2  illustrates an example method of the method illustrated in  FIG. 1 , and the example method may include the following steps S 21  to S 24 . 
     In step S 21 , a plurality of first pattern preliminary structures are formed on the side surface of the substrate  1  using a predetermined ink, to form a gap between any adjacent two of the first pattern preliminary structures that connects the top surface and the bottom surface of the substrate  1  to each other, and the predetermined ink includes a first solvent and a self-assembly material. 
     For example, the plurality of first pattern preliminary structures may be formed by using an existing transfer printing process. Each of the plurality of first pattern preliminary structures is processed into a first pattern structure  11  in a subsequent step. Since each first pattern structure  11  will be finally removed, the requirement on a thickness uniformity and integrity of each first pattern preliminary structure in this step is not high. 
     The self-assembly material may be polystyrene microspheres. In this case the first solvent may be any one selected from carbon tetrachloride, dichloroethane, chloroform, tetrahydrofuran, nitrobenzene, toluene and carbon disulfide, and for example may be carbon tetrachloride. 
     In order to stabilize a state of each of the plurality of first pattern preliminary structures, each of the plurality of first pattern preliminary structures may be left to stand still (or may be let stand still) for a preset time (e.g., the preset time may be one as described below). 
     In step S 22 , the first solvent in the predetermined ink is removed and the self-assembly material is combined into a unitary structure (i.e., a one-piece structure) to obtain the plurality of first pattern structures  11 . The purpose of step S 22  is to bring each of the plurality of first pattern preliminary structures into a stable and coherent solid state. 
     For example, step S 22  may include: rapidly evaporating the first solvent to attach colloidal microspheres in the first solvent to the substrate  1 , and then drying the colloidal microspheres at a preset temperature (e.g., in a range from 23 degrees Celsius to 40 degrees Celsius) to combine the colloidal microspheres into the unitary structure. For example, the colloidal microspheres are dried to form colloidal crystals. The resulted substrate structure formed in step S 22  is shown in  FIG. 3 . 
     In step S 23 , a conductive material film is formed on the side surface (i.e., the side surface on which the plurality of first pattern structures  11  are formed) of the substrate  1  so as to cover the side surface. The conductive material film is, for example, a metal film, and the thickness of the metal film may be controlled to be between 2 μm and 6 μm. For example, the metal film may be a silver (Ag) film. 
     In step S 24 , the self-assembly material is removed by using a second solvent and the portions of the conductive material film attached on the plurality of first pattern structures  11  are separated from the substrate  1 . In the case where the self-assembly material is polystyrene microspheres, the second solvent may be trichlorotoluene. For example, the second solvent and the self-assembly material may undergo a dissolution reaction (i.e., the self-assembly material may be dissolved in the second solvent). The resulted substrate structure formed in this step is shown in  FIG. 4 . 
       FIG. 5  is a schematic cross-sectional view of the substrate structure shown in  FIG. 4  taken along line AA′. As shown in  FIG. 5 , each of the plurality of first pattern structures  11  covers a portion of the top surface of the substrate  1 , a portion of the side surface (e.g., the right side surface in  FIG. 5 ) of the substrate  1 , and a portion of the bottom surface of the substrate  1 . In other words, each of the plurality of first pattern structures  11  has a substantially U-shape, and an opening of the U-shape is directed toward the side surface of the substrate  1  on which the plurality of first pattern structures  11  are formed. Each of a portion of each first pattern structure  11  located on the top surface of the substrate  1 , a portion of the first pattern structure  11  located on the side surface of the substrate  1 , and a portion of the first pattern structure  11  located on the bottom surface of the substrate  1  may have a shape of parallelogram (e.g., a shape of rectangle). 
     In the above embodiments, the self-assembly material may have three properties: being capable of being in a form of an ink, being capable of being incorporated into a stable, unitary solid structure, and being capable of being removed by a solvent after being incorporated into the stable, unitary solid structure. 
     Based on the above, one type of material that may be selected as the self-assembly material is colloidal microspheres. 
     Specifically, the colloidal microspheres may be, for example, polystyrene microspheres. A diameter of each of the polystyrene microspheres may be selected to be 50 nm to 300 nm. In the case of adopting the polystyrene microspheres, a stand-still time of each of the plurality of first pattern structures  11  is, for example, between 2 mins and 10 mins. 
     It should be noted that a mass percentage of the colloidal microspheres in the predetermined ink is between 5% and 30% (e.g., may be further between 5% and 20%). If the mass percentage of the colloidal microspheres is too small, each of the plurality of first pattern structures  11  formed is too thin to separate a portion of the conductive material to be removed from a portion of the conductive material to be remained. If the mass percentage of the colloidal microspheres is too large, it may not be advantageous to form a predetermined pattern from the predetermined ink by using a process such as the transfer printing. 
     For example, as shown in  FIGS. 4 and 5 , both ends of each of the plurality of first pattern structures  11  extend to an edge region of the top surface and an edge region of the bottom surface of the substrate  1 , respectively, and both ends of a portion of the conductive material film located between any adjacent two of first pattern structures  11  extend to the edge region of the top surface and the edge region of the bottom surface of the substrate  1 , respectively. For example, both ends of the portion (i.e., the side wire  12 ) of the conductive material film between any adjacent two of the plurality of first pattern structures  11  are respectively flush with both ends of another portion (i.e., another side wire  12 ) adjacent to the portion. For example, the side wire  12  shown in  FIG. 4  may be formed between the adjacent two first pattern structures  11  shown in  FIG. 3 , an end of the side wire  12  on the top surface of the substrate  1  may be flush with (e.g., aligned with) an end of any one of the adjacent two first pattern structures  11  on the top surface of the substrate  1 , and an end of the side wire  12  on the bottom surface of the substrate  1  may be flush with (e.g., aligned with) an end of any one of the adjacent two first pattern structures  11  on the bottom surface of the substrate  1 . That is, the gap between any adjacent two of the plurality of first pattern structures  11  also extends to the top surface and the bottom surface of the substrate  1 , such that the side wire  12  formed in a subsequent step also extends to the top surface and the bottom surface of the substrate  1 . The portion of the side wire  12  extending to the top surface of the substrate  1  may be used for electrically connecting to the Micro LEDs  13  (or connecting to a driving circuit of the Micro LEDs  13 ), and the portion of the side wire  12  extending to the bottom surface of the substrate  1  may be used for electrically connecting a structure such as a flexible printed circuit board (FPC) or the like. 
     It should be noted that, when the side wires  12  located on the side surface of the substrate  1  are manufactured, some circuit structures (e.g., the Micro LEDs  13 ) are already arranged on the top surface or the bottom surface of the substrate  1  in some cases. In these cases, the manufacturing method may further include, before forming the first pattern structures  11 : attaching protective films  2  onto the top and bottom surfaces of the substrate  1 , respectively, such that boundaries of the protective films  2  on the top and bottom surfaces of the substrate  1  are in contact with outer contours of the edge regions of the top and bottom surfaces of the substrate  1 , respectively, as shown in  FIG. 6 . That is, the boundary of the protective film  2  is the boundary of the portion of each side wire  12  extending to the bottom surface or the boundary of the portion of each side wire  12  extending to the top surface. In other words, each of the protective films  2  may be located on a portion of the top surface or bottom surface of the substrate  1  that is not covered by the plurality of first pattern structures  11 . That is, one end of each protective film  2  may be in contact with one end of each side wire  12  (and/or one end of each first pattern structure  11 ), as shown in  FIG. 6 . Apparently, the protective films  2  should be removable (e.g., peelable) in a subsequent process. 
     It should be noted that, some lines (not shown) are usually formed on both the top surface and the bottom surface of the substrate  1  before the side wires  12  of the substrate  1  are formed. The side wires  12  may be required to be electrically connected to these existing lines, whether the side wires  12  are provided only on the side surfaces of the substrate  1  or are provided to further extend to the top and/or bottom surface of the substrate  1 . Although only one side wire  12  is shown in the drawings, actually the number of the side wires  12  is not limited to one. Further, a length of each side wire  12  extending on the top surface or the bottom surface of the substrate  1  may be adjusted according to actual requirements. Each of the side wires  12  may have a substantially U-shape, and an opening of the U-shape may be directed toward the side surface of the substrate  1  on which the plurality of first pattern structures  11  are formed. 
     Each of the side wires manufactured by the method according to the above embodiments of the present disclosure has a uniform thickness and is not easily to be broken, thereby improving the reliability and the performance of the resulting substrate structure. 
     The embodiments of the present disclosure further provide a substrate structure manufactured by the manufacturing method according to the above-described embodiments of the present disclosure. 
     As shown in  FIGS. 4 and 5 , the substrate structure may include the substrate  1  and a side wire  12  located at a side surface of the substrate  1 . Both ends of the side wire  12  extend onto the edge region of the top surface and the edge region of the bottom surface of the substrate  1 , respectively. The side wire  12  has a substantially U-shape with an opening proximal to (i.e., directed toward) the side of the substrate  1 . 
     Compared with the prior art, the thickness of the side wire  12  of the substrate structure has an improved uniformity, and defects such as breakage of the side wire  12  are reduced. 
     It should be understood that the above embodiments are merely exemplary embodiments adopted to illustrate the principles of the present disclosure, and the present disclosure is not limited thereto. It will be apparent to one of ordinary skill in the art that various changes and modifications may be made without departing from the scope of the present disclosure as defined in the appended claims, and such changes and modifications also fall within the scope of the present disclosure.