Patent Publication Number: US-2023134317-A1

Title: Electrical connection structure and electronic device including the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority benefits of U.S. application Ser. No. 63/275,893, filed on Nov. 4, 2021 and Chinese application no. 202210891522.X, filed on Jul. 27, 2022. The entirety of each of the above-mentioned patent applications is hereby incorporated by reference herein and made a part of this specification. 
    
    
     BACKGROUND 
     Technical Field 
     The disclosure relates to a connection structure, and particularly relates to an electrical connection structure and an electronic device including the same. 
     Description of Related Art 
     Along with continuous expansion of applications and innovative technological development of electronic devices, requirements for an electrical connection structure and quality of the electronic devices are increasing so that the electronic devices are faced with different issues. Therefore, continuous update and adjustment for research and development of electronic devices may be required. 
     SUMMARY 
     The disclosure is directed to an electrical connection structure and an electronic device including the same. 
     According to an embodiment of the disclosure, an electrical connection structure includes a first substrate, a first conductive pad, a second substrate, a second conductive pad, a through hole, and a conductive material. The first conductive pad is disposed on the first substrate. The first conductive pad includes a first upper surface. The second conductive pad is disposed on the second substrate. The second conductive pad includes a second upper surface. The through hole penetrates the first substrate and exposes a part of the second upper surface. The conductive material is partially disposed in the through hole. The conductive material includes a narrowest portion and a first contact portion in contact with the second upper surface. A length of the first contact portion is greater than a length of the narrowest portion in a cross-sectional view. 
     According to an embodiment of the disclosure, an electronic device includes an electrical connection structure, an electronic component, a driving substrate; and a third conductive pad. The electrical connection structure includes a first substrate, a first conductive pad, a second substrate, a second conductive pad, a through hole, and a conductive material. The first conductive pad is disposed on the first substrate. The first conductive pad includes a first upper surface. The second conductive pad is disposed on the second substrate. The second conductive pad includes a second upper surface. The through hole penetrates the first substrate and exposes a part of the second upper surface. The conductive material is partially disposed in the through hole. The conductive material includes a narrowest portion and a first contact portion in contact with the second upper surface. A length of the first contact portion is greater than a length of the narrowest portion in a cross-sectional view. The electronic component is disposed on the first substrate, and electrically connected to the first conductive pad disposed on the first substrate. The third conductive pad is disposed on the driving substrate, and electrically connected to the second substrate. 
     Based on the above description, in the embodiments of the disclosure, the through hole penetrates the first substrate and exposes a part of the second upper surface of the second conductive pad, and the conductive material is partially disposed in the through hole, so that the first substrate and the second substrate have an electrical conduction path. Therefore, the electrical connection structure of the disclosure may achieve the effect of electrically connecting a plurality of substrates, and when it is subsequently applied to an electronic device, the electrical conduction path between the substrates may be shortened and a design of a peripheral region may be simplified, so as to achieve a slim border design of the electronic device. In addition, the conductive material includes the narrowest portion and the first contact portion in contact with the second upper surface. In a cross-sectional view, the length of the first contact portion is greater than the length of the narrowest portion, which increases a contact length between the conductive pad and the conductive material, and enhances a success rate of electrical connection of multiple substrates, so that the electrical connection structure of the disclosure may have better electrical reliability. 
     To make the aforementioned more comprehensible, several embodiments accompanied with drawings are described in detail as follows. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are included to provide a further understanding of the disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the disclosure and, together with the description, serve to explain the principles of the disclosure. 
         FIG.  1    is a schematic cross-sectional view of an electrical connection structure according to an embodiment of the disclosure. 
         FIG.  2    is a schematic cross-sectional view of an electrical connection structure according to another embodiment of the disclosure. 
         FIG.  3    is a schematic cross-sectional view of an electrical connection structure according to another embodiment of the disclosure. 
         FIG.  4    is a schematic cross-sectional view of an electrical connection structure according to another embodiment of the disclosure. 
         FIG.  5    is a schematic cross-sectional view of an electrical connection structure according to another embodiment of the disclosure. 
         FIG.  6    is a schematic cross-sectional view of an electrical connection structure according to another embodiment of the disclosure. 
         FIG.  7    is a schematic cross-sectional view of an electrical connection structure according to another embodiment of the disclosure. 
         FIG.  8    is a schematic cross-sectional view of an electrical connection structure according to another embodiment of the disclosure. 
         FIG.  9    is a schematic cross-sectional view of an electrical connection structure according to another embodiment of the disclosure. 
         FIG.  10    is a schematic cross-sectional view of an electronic device using the electrical connection structure of  FIG.  1   . 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     The disclosure may be understood by referring to the following detailed description in conjunction with the accompanying drawings. It should be noted that, in order to facilitate readers&#39; understanding and to simplify the drawings, the drawings in the disclosure only depict a part of an electronic device, and specific elements in the drawings are not drawn according to actual scale. In addition, the number and size of each element in the figures are for illustration only, and are not intended to limit a scope of the disclosure. 
     Throughout the specification and the appended claims of the disclosure, certain terms may be used to refer to specific elements. Those skilled in the art will understand that electronic device manufacturers may refer to the same element by different names. This document does not intend to distinguish between elements that have the same function but have different names. 
     In the following description and claims, the words “comprising” and “including” are open-ended words, so they should be interpreted as meaning “including but not limited to . . . ”. 
     In addition, relative terms, such as “below” or “bottom” and “above” or “top,” may be used in the embodiments to describe a relative relationship of one element of the drawings to another element. It will be understood that if a device in the figures is turned upside down, elements described on a “lower” side would become elements described on an “upper” side. 
     In some embodiments of the disclosure, terms related to bonding and connection, such as “connect”, “interconnect”, etc., unless otherwise defined, may refer to that two structures are in direct contact, or may also refer to that the two structures are not directly (indirectly) in contact with each other, and there are other structures between the two structures. And the terms of joining and connecting may also include the case where both structures are movable, or both structures are fixed. Furthermore, a term “couple” includes transfer of energy between two structures by means of direct or indirect electrical connection, or transfer of energy between two separate structures by means of mutual induction. 
     It will be understood that when an element or a film layer is referred to as being “on” or “connected to” another element or film layer, it may be directly on or directly connected to the other element or film layer, or there are intervening elements or film layers there between (indirect case). In contrast, when an element is referred to as being “directly on” or “directly connected to” another element or film layer, there are no intervening elements or film layers there between. 
     In the disclosure, lengths, widths, thicknesses, heights or areas, or a distance or spacing between components may be measured by using an optical microscope (OM), a scanning electron microscope (SEM), a film thickness profiler (α-step), an ellipsometer, or other suitable methods. In detail, according to some embodiments, the scanning electron microscope may be used to obtain cross-sectional structure images of the components to be measured, and measure a length, a width, a thickness, a height or an area of each component, or a distance or spacing between components, but the disclosure is not limited thereto. 
     In addition, phrases “a given range is from a first value to a second value”, “a given range falls within a range from the first value to the second value” means that the given range includes the first value, the second value and other values there between. If a first direction is perpendicular to a second direction, an angle between the first direction and the second direction may be between 80 degrees and 100 degrees; if the first direction is parallel to the second direction, the angle between the first direction and the second direction may be between 0 and 10 degrees. The terms “about”, “equal to”, “equal” or “same”, “substantially” or “approximately” are generally construed as within 20% of a given value or range, or construed as within 10%, 5%, 3%, 2%, 1%, or 0.5% of the given value or range. 
     As used herein, the terms “film” and/or “layer” may refer to any continuous or discontinuous structures and materials (such as materials deposited by the methods disclosed herein). For example, films and/or layers may include two-dimensional materials, three-dimensional materials, nanoparticles, or even partial or complete molecular layers, or partial or complete atomic layers, or atom and/or molecular clusters. The film or layer may comprise a material or layer having pinholes, which may be at least partially continuous. 
     Although the terms first, second, third . . . may be used to describe various constituent elements, the constituent elements are not limited by the terms. These terms are only used to distinguish a single constituent element from other constituent elements in the specification. 
     The same terms may not be used in the claims, but replaced by first, second, third, . . . in the order in which the elements are recited in the claims. Therefore, in the following description, the first constituent element may be the second constituent element in the claims. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
     It should be noted that, in the following embodiments, the technical features in several different embodiments may be replaced, reorganized, and mixed to complete other embodiments without departing from the spirit of the disclosure. 
     Reference will now be made in detail to the exemplary embodiments of the disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numerals are used in the drawings and description to refer to the same or like parts. 
       FIG.  1    is a schematic cross-sectional view of an electrical connection structure according to an embodiment of the disclosure. Referring to  FIG.  1   , in the embodiment, an electrical connection structure  100   a  includes a first substrate  110   a , a first conductive pad  120   a , a second substrate  130 , a second conductive pad  140 , a through hole  150   a , and a conductive material  160   a . The first conductive pad  120   a  is disposed on the first substrate  110   a , where the first conductive pad  120   a  includes a first upper surface  122   a . The second conductive pad  140  is disposed on the second substrate  130 , where the second conductive pad  140  includes a second upper surface  142 . The through hole  150   a  penetrates the first substrate  110   a  and exposes a part of the second upper surface  142 . The conductive material  160   a  is partially disposed in the through hole  150   a , where the conductive material  160   a  includes a narrowest portion  162   a  and a first contact portion  164   a  in contact with the second upper surface  142 . In a cross-sectional view, a length L 12  of the first contact portion  164   a  is greater than a length L 11  of the narrowest portion  162   a , which may increase a contact length between the second conductive pad  140  and the conductive material  160   a , and improve a success rate of electrical connection between the first substrate  110   a  and the second substrate  130 . In the embodiment, the through hole  150   a  substantially has a design of a wide top and a narrow bottom, but in order to avoid insufficient contact length between the conductive material  160   a  and the second conductive pad  140 , the through hole  150   a  of  FIG.  1    may include a design of a through hole wide portion WR 1  and a through hole wide portion WR 2  at left and right sides. In a direction from the narrowest portion  162   a  to the first contact portion  164   a , the through hole wide portion WR 1  and the through hole wide portion WR 2  include portions where a through hole diameter on the left and right sides of the through hole  150   a  gradually increases, and the through hole wide portion WR 1  and the through hole wide portion WR 2  are adjacent to the second conductive pad  140 . When the conductive material  160   a  fills the through hole wide portion WR 1  and the through hole wide portion WR 2 , the contact length between the second conductive pad  140  and the conductive material  160   a  may be increased, and the success rate of the electrical connection between the first substrate  110   a  and the second substrate  130  may also be improved. In some embodiments, the design of the through hole  150   a  may include one of the through hole wide portion WR 1  and the through hole wide portion WR 2 . When the conductive material  160   a  fills one of the through hole wide portion WR 1  and the through hole wide portion WR 2 , the contact length of the second conductive pad  140  and the conductive material  160   a  may also be improved, and the success rate of the electrical connection between the first substrate  110   a  and the second substrate  130  may be improved. 
     The manner in which the conductive material  160   a  is disposed in the through hole  150   a  may include solder paste printing, inkjet printing, chemical vapor deposition, physical vapor deposition, electroplating, or other suitable methods, or a combination of the above methods, but the disclosure is not limited thereto. A material of the conductive material  160   a  may include tantalum (Ta), niobium (Nb), hafnium (HO, nickel (Ni), chromium (Cr), cobalt (Co), zirconium (zirconium, Zr), tungsten (W), aluminum (Al), tin (Sn), copper (Cu), silver (Ag), aurum (Au) or other suitable metals, or alloys or combinations of the above materials, but the disclosure is not limited thereto. The through hole  150   a  may be fabricated by, for example, mechanical drilling, laser drilling, ultrasonic drilling, micro electrical discharge machining (μ-EDM), micro powder blasting or inductively coupled plasma reactive ion etching (ICP-RIE) or other suitable methods, or a combination of the above methods, but the disclosure is not limited thereto. 
     In detail, in the embodiment, the first substrate  110   a  and the second substrate  130  may be, for example, respectively rigid substrates, flexible substrates, or a combination thereof. A material of the first substrate  110   a  and a material of the second substrate  130  may be, for example, glass, quartz, sapphire, ceramic, polycarbonate (PC), polyimide (PI), polyethylene terephthalate (PET), other suitable substrate materials, or a combination of the above materials, but the disclosure is not limited thereto. Furthermore, as shown in  FIG.  1   , the electrical connection structure  100   a  of the embodiment further includes an intermediate layer  170  disposed between the first substrate  110   a  and the second substrate  130  and covering the second conductive pad  140 . The through hole  150   a  penetrates the first substrate  110   a  and a part of the intermediate layer  170  to expose a part of the second upper surface  142 . In other words, the intermediate layer  170  may be disposed between at least two of a plurality of substrates. A material of the intermediate layer  170  may include organic materials, inorganic materials, other suitable substrate materials, or a combination of the above materials, but the disclosure is not limited thereto. In some embodiments, the intermediate layer  170  may adhere at least two of the plurality of substrates. 
     Referring to  FIG.  1    again, in the embodiment, the through hole  150   a  penetrates the first conductive pad  120   a , the first substrate  110   a  and a part of the intermediate layer  170  to expose a part of the second upper surface  142  of the second conductive pad  140 . A diameter of the through hole  150   a  may be, for example, gradually reduced first and then gradually enlarged in a direction from the first substrate  110   a  toward the second upper surface  142 , but the disclosure is not limited thereto. The narrowest portion  162   a  may be located in the intermediate layer  170 , but the disclosure is not limited thereto. The conductive material  160   a  fills the through hole  150   a  and extends to the first upper surface  122   a  of the first conductive pad  120   a  located on both sides of the through hole  150   a , where the filled conductive material  160   a  electrically connects the first conductive pad  120   a  and the second conductive pad  140 , which achieves an effect of vertically conducting (i.e., electrically connecting) the first substrate  110   a  and the second substrate  130 . 
     Furthermore, the conductive material  160   a  of the embodiment further includes a second contact portion  166   a  in contact with the first upper surface  122   a , where a length L 13  of the second contact portion  166   a  is greater than the length L 11  of the narrowest portion  162   a , which may increase a contact length between the first conductive pad  120   a  and the conductive material  160   a , and improve the success rate of electrical connection between the first substrate  110   a  and the second substrate  130 . As shown in  FIG.  1   , the length L 13  of the second contact portion  166   a  in the embodiment is greater than the length L 12  of the first contact portion  164   a , and the length L 12  of the first contact portion  164   a  is greater than the length L 11  of the narrowest portion  162   a , which may increase the contact length between the first conductive pad  120   a  and the conductive material  160   a  and the contact length between the second conductive pad  140  and the conductive material  160   a , and improve the success rate of the electrical connection between the first substrate  110   a  and the second substrate  130 . Furthermore, the conductive material  160   a  of the embodiment has an arc-shaped upper surface  1605 , which may facilitate better sidewall step coverage during film deposition when film deposition is performed on the upper layer of the conductive material  160   a.    
     In brief, the through hole  150   a  penetrates the first substrate  110   a  and exposes a part of the second upper surface  142  of the second conductive pad  140 , and the conductive material  160   a  is partially disposed in the through hole  150   a , so that the first substrate  110   a  and the second substrate  130  may be electrically conducted. Therefore, the electrical connection structure  100   a  of the embodiment may achieve the effect of electrically connecting a plurality of substrates, and when the electrical connection structure  100   a  is subsequently applied to an electronic device, an electrical conduction path between the first substrate  110   a  and the second substrate  130  may be greatly shortened, the design of the peripheral regions of the first substrate  110   a  and the second substrate  130  may also be simplified, and the electronic device may achieve a design of slim border or even no border. In addition, in a cross-sectional view, the length L 12  of the first contact portion  164   a  of the conductive material  160   a  is greater than the length L 11  of the narrowest portion  162   a  of the conductive material  160   a , and the through hole  150   a  may be designed to include the through hole wide portion WR 1  and/or the through hole wide portion WR 2 , when the conductive material  160   a  fills the through hole wide portion WR 1  and/or the through hole wide portion WR 2 , the contact length between the second conductive pad  140  and the conductive material  160   a  may be increased, and the success rate of the electrical connection between the first substrate  110   a  and the second substrate  130  may also be improved, so that the electrical connection structure  100   a  of the disclosure may have better electrical reliability. 
     It should be noted here that the following embodiments adopt the element numbers and a part of the contents of the previous embodiments, where the same numbers are used to represent the same or similar elements, and the description of the same technical contents is omitted. For the description of the omitted part, reference may be made to the foregoing embodiments, and repeated descriptions thereof in the following embodiments will not be repeated. 
       FIG.  2    is a schematic cross-sectional view of an electrical connection structure according to another embodiment of the disclosure. Referring to  FIG.  1    and  FIG.  2    at the same time, an electrical connection structure  100   b  is similar to the electrical connection structure  100   a  of  FIG.  1   , and descriptions of similar parts thereof are not repeated here. A difference between  FIG.  1    and  FIG.  2    is: in the embodiment of  FIG.  2   , a first substrate  110   b  includes a base layer  112  and a dielectric layer  114 , where the dielectric layer  114  is disposed on the base layer  112 , and the first conductive pad  120   a  is disposed on the dielectric layer  114 . A material of the base layer  112  is, for example, a polymer, and a material of the dielectric layer  114  is, for example, an inorganic material, but the disclosure is not limited thereto. In some embodiments, a multi-layer stacked structure (not shown) may be designed between the base layer  112  and the first conductive pad  120   a , for example, a conductive layer, a semiconductor layer, an insulating layer, a passivation layer, a light-emitting layer, an encapsulation layer or other suitable stacked layers, or a combination of the above stacked layers may be added there between, but the disclosure is not limited thereto. 
       FIG.  3    is a schematic cross-sectional view of an electrical connection structure according to another embodiment of the disclosure. Referring to  FIG.  1    and  FIG.  3    at the same time, an electrical connection structure  100   c  is similar to the electrical connection structure  100   a  of  FIG.  1   , and descriptions of similar parts thereof are not repeated here. A difference between  FIG.  1    and  FIG.  3    is that in the embodiment of  FIG.  3   , an air gap G 1  is between a conductive material  160   c  and the through hole  150   a , i.e., the conductive material  160   c  fills the through hole wide portion WR 1  and the through hole wide portion WR 2  but not completely fill the through hole  150   a . In detail, in the embodiment, a first conductive pad  120   c  includes a side surface  124   c , where the side surface  124   c  is adjacent to the through hole  150   a . The conductive material  160   c  fills the through hole  150   a  and extends along the side surface  124   c  of the first conductive pad  120   c  to a first upper surface  122   c  of the first conductive pad  120   c . The conductive material  160   c  includes a narrowest portion  162   c , a first contact portion  164   c  in contact with the second upper surface  142 , and a second contact portion  166   c  in contact with the first upper surface  122   c , where a length L 33  of the second contact portion  166   c  is greater than a length L 31  of the narrowest portion  162   c , and a length L 32  of the first contact portion  164   c  is greater than the length L 31  of the narrowest portion  162   c , which may increase a contact length of the first conductive pad  120   c , the second conductive pad  140  and the conductive material  160   a , and improve a success rate of electrical connection between the first substrate  110   a  and the second substrate  130 . In the embodiment of  FIG.  3   , the length L 32  of the first contact portion  164   c  may be greater than the length L 33  of the second contact portion  166   c . Here, the conductive material  160   c  fills the through hole wide portion WR 1  and the through hole wide portion WR 2  and is in direct contact with the second conductive pad  140 , the side surface  124   c  and the first upper surface  122   c  of the first conductive pad  120   c , where the filled conductive material  160   c  is electrically connected to the first conductive pad  120   c  and the second conductive pad  140 , so as to achieve the effect of vertically conducting (i.e., electrically connecting) the first substrate  110   a  and the second substrate  130 . The electrical connection structure  100   c  of the embodiment may achieve the effect of electrically connecting a plurality of substrates, and when the electrical connection structure  100   c  is subsequently applied to an electronic device, the electrical conduction path between the first substrate  110   a  and the second substrate  130  may be greatly shortened, the design of the peripheral regions of the first substrate  110   a  and the second substrate  130  may also be simplified, and the electronic device may achieve a design of slim border or even no border. 
     In some embodiments, the design of the through hole  150   a  may include one of the through hole wide portion WR 1  and the through hole wide portion WR 2 , and when the conductive material  160   c  fills one of the through hole wide portion WR 1  and the through hole wide portion WR 2 , the contact length between the second conductive pad  140  and the conductive material  160   c  may also be increased to improve the success rate of electrical connection between the first substrate  110   a  and the second substrate  130 . 
       FIG.  4    is a schematic cross-sectional view of an electrical connection structure according to another embodiment of the disclosure. Referring to  FIG.  1    and  FIG.  4    at the same time, an electrical connection structure  100   d  is similar to the electrical connection structure  100   a  of  FIG.  1   , and descriptions of similar parts thereof are not repeated here. One of the differences between  FIG.  1    and  FIG.  4    is that in  FIG.  4    of the embodiment, an air gap G 2  is between a conductive material  160   d  and a through hole  150   d , i.e., the conductive material  160   d  fills the through hole wide portion WR 1  and the through hole wide portion WR 2  but does not completely fill the through hole  150   d . In detail, the conductive material  160   d  is filled into the through hole  150   d , and the conductive material  160   d  includes a narrowest portion  162   d , a first contact portion  164   d  in contact with the second upper surface  142 , and a second contact portion  166   d  in contact with the first upper surface  122   a , where a length L 43  of the second contact portion  166   d  is greater than a length L 42  of the first contact portion  164   d , and the length L 42  of the first contact portion  164   d  is greater than a length L 41  of the narrowest portion  162   d , so that the contact length between the first conductive pad  120   a , the second conductive pad  140  and the conductive material  160   d  may be increased to improve the success rate of the electrical connection between the first substrate  110   a  and the second substrate  130 . Here, the filled conductive material  160   d  is electrically connected to the first conductive pad  120   a  and the second conductive pad  140 , so as to achieve the effect of vertically conducting (i.e., electrically connecting) the first substrate  110   a  and the second substrate  130 . The electrical connection structure  100   d  of the embodiment may achieve the effect of electrically connecting a plurality of substrates, and when the electrical connection structure  100   d  is subsequently applied to an electronic device, the electrical conduction path between the first substrate  110   a  and the second substrate  130  may be greatly shortened, the design of the peripheral regions of the first substrate  110   a  and the second substrate  130  may also be simplified, and the electronic device may achieve a design of slim border or even no border. 
     Moreover, the design of the through hole  150   d  in  FIG.  4    may have a relatively uniform through hole diameter at the beginning, and then further include the through hole wide portion WR 1  and the through hole wide portion WR 2  at a place adjacent to the second upper surface  142 . In some embodiments, the design of the through hole  150   d  may include one of the through hole wide portion WR 1  and the through hole wide portion WR 2 , and when the conductive material  160   d  fills one of the through hole wide portion WR 1  and the through hole wide portion WR 2 , the contact length between the second conductive pad  140  and the conductive material  160   d  may also be improved to enhance the success rate of the electrical connection between the first substrate  110   a  and the second substrate  130 . 
       FIG.  5    is a schematic cross-sectional view of an electrical connection structure according to another embodiment of the disclosure. Referring to  FIG.  1    and  FIG.  5    at the same time, an electrical connection structure  100   e  is similar to the electrical connection structure  100   a  of  FIG.  1   , and similar part thereof are will not be repeated here. A difference between  FIG.  1    and  FIG.  5    is that in the embodiment in  FIG.  5   , a through hole  150   e  is generally narrow at the top and wide at the bottom, and penetrates a first conductive pad  120   e , the first substrate  110   a  and a part of the intermediate layer  170  to expose a part of the second upper surface  142  of the second conductive pad  140 , where a diameter of the through hole  150   e  gradually increases in a direction from the first substrate  110   a  toward the second upper surface  142 . When the through hole  150   e  penetrates the first conductive pad  120   e , a part of the first substrate  110   a  is exposed, and a conductive material  160   e  includes a narrowest portion  162   e , a first contact portion  164   e  in contact with the second upper surface  142 , and a second contact portion  166   e  in contact with a first upper surface  122   e , where a length of the narrowest portion  162   e  is L 51 , and the length L 51  may be substantially a diameter of the through hole  150   e  corresponding to the upper surface of the first substrate  110   a . Furthermore, a length L 53  of the second contact portion  166   e  is greater than a length L 52  of the first contact portion  164   e , and the length L 52  of the first contact portion  164   e  is greater than the length L 51  of the narrowest portion  162   e , which may increase the contact length between the first conductive pad  120   e  and the second conductive pad  140  and the conductive material  160   e  to enhance the success rate of the electrical connection between the first substrate  110   a  and the second substrate  130 . In addition, the filled conductive material  160   e  electrically connects the first conductive pad  120   e  and the second conductive pad  140  to achieve the effect of vertically conducting (i.e., electrically connecting) the first substrate  110   a  and the second substrate  130 . The electrical connection structure  100   e  of the embodiment may achieve the effect of electrically connecting a plurality of substrates, and when the electrical connection structure  100   e  is subsequently applied to an electronic device, the electrical conduction path between the first substrate  110   a  and the second substrate  130  may be greatly shortened, the design of the peripheral regions of the first substrate  110   a  and the second substrate  130  may also be simplified, and the electronic device may achieve a design of slim border or even no border. 
       FIG.  6    is a schematic cross-sectional view of an electrical connection structure according to another embodiment of the disclosure. Referring to  FIG.  1    and  FIG.  6    at the same time, an electrical connection structure  100   f  is similar to the electrical connection structure  100   e  of  FIG.  5   , and descriptions of similar parts thereof are not repeated here. A difference between  FIG.  5    and  FIG.  6    is that in the embodiment in  FIG.  6   , a through hole  150   f  includes the through hole wide portion WR 1  and the through hole wide portion WR 2 . The through hole  150   f  penetrates the first conductive pad  120   e , the first substrate  110   a , and a part of the intermediate layer  170  to expose a part of the second upper surface  142  of the second conductive pad  140 , where a diameter of the through hole  150   f  includes the through hole wide portion WR 1  and the through hole wide portion WR 2 , and a shape of the through hole  150   f  from the first substrate  110   a  to the second upper surface  142  is like a stepped through hole (increasing gradually in two stages in a stepped manner). A conductive material  160   f  includes a narrowest portion  162   f , a first contact portion  164   f  in contact with the second upper surface  142 , and a second contact portion  166   f  in contact with the first upper surface  122   e , where a length L 63  of the second contact portion  166   f  is greater than a length L 62  of the first contact portion  164   f , and the length L 62  of the first contact portion  164   f  is greater than a length L 61  of the narrowest portion  162   f , which may increase the contact length of the first conductive pad  120   e , the second conductive pad  140  and the conductive material  160   f , and enhance the success rate of electrical connection between the first substrate  110   a  and the second substrate  130 . In addition, the filled conductive material  160   f  electrically connects the first conductive pad  120   e  and the second conductive pad  140  to achieve the effect of vertically conducting (i.e., electrically connecting) the first substrate  110   a  and the second substrate  130 . The electrical connection structure  100   f  of the embodiment may achieve the effect of electrically connecting a plurality of substrates, and when the electrical connection structure  100   f  is subsequently applied to an electronic device, the electrical conduction path between the first substrate  110   a  and the second substrate  130  may be greatly shortened, the design of the peripheral regions of the first substrate  110   a  and the second substrate  130  may also be simplified, and the electronic device may achieve a design of slim border or even no border. In some embodiments, the design of the through hole  150   f  may include one of the through hole wide portion WR 1  and the through hole wide portion WR 2 . When the conductive material  160   f  fills one of the through hole wide portion WR 1  and the through hole wide portion WR 2 , the contact length between the second conductive pad  140  and the conductive material  160   f  may be increased to enhance the success rate of electrical connection between the first substrate  110   a  and the second substrate  130 . 
       FIG.  7    is a schematic cross-sectional view of an electrical connection structure according to another embodiment of the disclosure. Referring to  FIG.  6    and  FIG.  7    at the same time, an electrical connection structure  100   g  is similar to the electrical connection structure  100   f  of  FIG.  6   , and descriptions of similar parts thereof are not repeated here. A difference between  FIG.  6    and  FIG.  7    is that: in the embodiment of  FIG.  7   , the first substrate  110   b  includes the base layer  112  and the dielectric layer  114 , where the dielectric layer  114  is disposed on the base layer  112 , and the first conductive pad  120   e  is disposed on the dielectric layer  114 . A material of the base layer  112  is, for example, a polymer, and a material of the dielectric layer  114  is, for example, an inorganic material, but the disclosure is not limited thereto. In some embodiments, a multi-layer stacked structure (not shown) may be designed between the base layer  112  and the first conductive pad  120   e , for example, a conductive layer, a semiconductor layer, an insulating layer, a passivation layer, a light-emitting layer, an encapsulation layer, or other suitable stacked layers, or a combination of the stacked layers may be added there between, but the disclosure is not limited thereto. 
       FIG.  8    is a schematic cross-sectional view of an electrical connection structure according to another embodiment of the disclosure. Referring to  FIG.  6    and  FIG.  8    at the same time, an electrical connection structure  100   h  is similar to the electrical connection structure  100   f  of  FIG.  6   , and descriptions of similar parts thereof are not repeated here. A difference between  FIG.  6    and  FIG.  8    is that: in the embodiment of  FIG.  8   , an air gap G 3  is between a conductive material  160   h  and the through hole  150   f , i.e., the conductive material  160   h  fills the through hole wide portion WR 1  and the through hole wide portion WR 2  but does not completely fill the through hole  150   f . In detail, in the embodiment, a first conductive pad  120   h  includes a side surface  124   h , where the side surface  124   h  is adjacent to the through hole  150   f . The conductive material  160   h  is filled into the through hole  150   f  and extends along the side surface  124   h  of the first conductive pad  120   h  to a first upper surface  122   h  of the first conductive pad  120   h . The conductive material  160   h  includes a narrowest portion  162   h , a first contact portion  164   h  in contact with the second upper surface  142 , and a second contact portion  166   h  in contact with the first upper surface  122   h , where a length L 83  of the second contact portion  166   h  is greater than a length L 81  of the narrowest portion  162   h , and a length L 82  of the first contact portion  164   h  is greater than the length L 81  of the narrowest portion  162   h , which increases a contact length of the first conductive pad  120   h , the second conductive pad  140  and the conductive material  160   h , and enhances a success rate of electrical connection between the first substrate  110   a  and the second substrate  130 . In the embodiment of  FIG.  8   , the length L 82  of the first contact portion  164   h  may be greater than the length L 83  of the second contact portion  166   h . Here, the conductive material  160   h  fills the through hole wide portion WR 1  and the through hole wide portion WR 2  and is in direct contact with the second conductive pad  140 , the side surface  124   h  of the first conductive pad  120   h , and the first upper surface  122   h , where the filled conductive material  160   h  electrically connects the first conductive pad  120   h  and the second conductive pad  140  to achieve the effect of vertically conducting (i.e., electrically connecting) the first substrate  110   a  and the second substrate  130 . The electrical connection structure  100   h  of the embodiment may achieve the effect of electrically connecting a plurality of substrates, and when the electrical connection structure  100   h  is subsequently applied to an electronic device, the electrical conduction path between the first substrate  110   a  and the second substrate  130  may be greatly shortened, the design of the peripheral regions of the first substrate  110   a  and the second substrate  130  may also be simplified, and the electronic device may achieve a design of slim border or even no border. 
     In some embodiments, the design of a through hole  150   h  may include one of the through hole wide portion WR 1  and the through hole wide portion WR 2 . When the conductive material  160   h  fills one of the through hole wide portion WR 1  and the through hole wide portion WR 2 , the contact length between the second conductive pad  140  and the conductive material  160   h  may be increased to enhance the success rate of electrical connection between the first substrate  110   a  and the second substrate  130 . 
       FIG.  9    is a schematic cross-sectional view of an electrical connection structure according to another embodiment of the disclosure. Referring to  FIG.  6    and  FIG.  9    at the same time, an electrical connection structure  100   i  is similar to the electrical connection structure  100   f  of  FIG.  6   , and descriptions of similar parts thereof are not repeated here. A difference between  FIG.  6    and  FIG.  9    is that: in the embodiment of  FIG.  9   , an air gap G 4  is between a conductive material  160   i  and the through hole  150   f , i.e., the conductive material  160   i  fills the through hole wide portion WR 1  and the through hole wide portion WR 2  but does not completely fill the through hole  150   f . In detail, the conductive material  160   i  is filled into the through hole  150   f , and the conductive material  160   i  includes a narrowest portion  162   i , a first contact portion  164   i  in contact with the second upper surface  142 , and a second contact portion  166   i  in contact with the first upper surface  122   e , where a length L 93  of the second contact portion  166   i  is greater than a length L 92  of the first contact portion  164   i , and the length L 92  of the first contact portion  164   i  is greater than a length L 91  of the narrowest portion  162   i , which increases a contact length of the first conductive pad  120   e , and the second conductive pad  140  with the conductive material  160   i  to enhance a success rate of electrical connection between the first substrate  110   a  and the second substrate  130 . The filled conductive material  160   i  electrically connects the first conductive pad  120   e  and the second conductive pad  140  to achieve the effect of vertically conducting (i.e., electrically connecting) the first substrate  110   a  and the second substrate  130 . The electrical connection structure  100   i  of the embodiment may achieve the effect of electrically connecting a plurality of substrates, and when the electrical connection structure  100   i  is subsequently applied to an electronic device, the electrical conduction path between the first substrate  110   a  and the second substrate  130  may be greatly shortened, the design of the peripheral regions of the first substrate  110   a  and the second substrate  130  may also be simplified, and the electronic device may achieve a design of slim border or even no border. 
     In some embodiments, the design of the through hole  150   f  may include one of the through hole wide portion WR 1  and the through hole wide portion WR 2 . When the conductive material  160   i  fills one of the through hole wide portion WR 1  and the through hole wide portion WR 2 , the contact length between the second conductive pad  140  and the conductive material  160   i  may be increased to enhance the success rate of electrical connection between the first substrate  110   a  and the second substrate  130 . 
       FIG.  10    is a schematic cross-sectional view of an electronic device using the electrical connection structure of  FIG.  1   . Referring to  FIG.  10   , in the embodiment, an electronic device  10  includes the electrical connection structure  100   a  of  FIG.  1   , an electronic component  20 , a driving substrate  30  and a third conductive pad  180 , where the second substrate  130  further includes a conductive via  135  electrically connected to the second conductive pad  140 . The electronic component  20  is disposed on the first substrate  110   a  and are electrically connected to the first conductive pad  120   a  disposed on the first substrate  110   a . The third conductive pad  180  is disposed on the driving substrate  30  and is electrically connected to the conductive via  135  of the second substrate  130 . In other words, the electronic device  10  of the embodiment may realize the electrical connection of a plurality of substrates through the electrical connection structure  100   a . In addition, the electronic device  10  of the embodiment may be provided with any electrical connection structure (i.e., any one of the electrical connection structures  100   a  to  100   i ) in the above-mentioned specification. In some embodiments, a plurality of electrical connection structures may be provided in the electronic device  10 , where the electrical connection structures may be provided with any one of the electrical connection structures in the above specification or a combination of the above electrical connection structures, but the disclosure is not limited thereto. Here, the electronic device  10  of the embodiment may include a display device, an antenna device, a sensing device, a light-emitting device, a touch display device, a packaging device, a curved display, a free-form display, or a splicing device, but the disclosure is not limited thereto. The electronic device  10  may include a bendable or flexible electronic device. The electronic device  10  may include a plurality of light boards electrically connected to each other. The electronic device  10  includes, for example, a liquid crystal layer or light emitting diodes (LED). The electronic component  20  may include passive components and active components, such as capacitors, resistors, inductors, variable capacitors, filters, diodes, transistors, inductors, MEMS, liquid crystal chips, etc., but the disclosure is not limited thereto. The diodes may include light emitting diodes or photodiodes. The light emitting diodes may include, for example, organic light emitting diodes (OLEDs), mini LEDs, micro LEDs, quantum dot LEDs, fluorescence, phosphor or other suitable materials, or a combination thereof, but the disclosure is not limited thereto. The sensors may include, for example, capacitive sensors, optical sensors, electromagnetic sensors, fingerprint sensors (FPS), touch sensors, antennas, or styluses (pen sensors), etc., but the disclosure is not limited thereto. The antenna is, but not limited to, a liquid crystal antenna, a diode antenna. An antenna device may include, but is not limited to, an antenna splicing device. It should be noted that, the electronic device  10  may be any arrangement and combination of the above, but the disclosure is not limited thereto. In addition, the electronic device  10  may have a rectangular shape, a circular shape, a polygonal shape, a shape with curved edges, or other suitable shapes in appearance. The electronic device  10  may have peripheral systems such as a driving system, a control system, a light source system, a shelf system, etc., to support a display device, an antenna device or a splicing device. 
     It should be noted that, in the above-mentioned embodiments, the number of electrical connection structures is schematically shown as one, and the number of substrates is schematically shown as two or three, but the disclosure is not limited thereto. In other not-shown embodiments, the number of electrical connection structures and the number of substrates may be increased according to actual requirements, which still fall within the scope of the disclosure. Moreover, the electrical connection structure may be selected from any one of the electrical connection structures in the above-mentioned specification or a combination of the above-mentioned electrical connection structures, but the disclosure is not limited thereto. 
     In summary, in the embodiments of the disclosure, the through hole penetrates the first substrate and exposes a part of the second upper surface of the second conductive pad, and the conductive material is partially disposed in the through hole, so that the first substrate and the second substrate may be electrically conducted. Therefore, the electrical connection structure of the disclosure may achieve the effect of electrically connecting a plurality of substrates, and when it is subsequently applied to an electronic device, the electrical conduction path between the substrates may be shortened and a design of a peripheral region of the substrate may be simplified, so as to achieve a slim border design or even no border design of the electronic device. In addition, the conductive material includes the narrowest portion and the first contact portion in contact with the second upper surface. In a cross-sectional view, the length of the first contact portion is greater than the length of the narrowest portion, which increases a contact length between the conductive pad and the conductive material, and enhances a success rate of electrical connection of multiple substrates, so that the electrical connection structure of the disclosure may have better electrical reliability. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed embodiments without departing from the scope or spirit of the disclosure. In view of the foregoing, it is intended that the disclosure covers modifications and variations provided they fall within the scope of the following claims and their equivalents.