Patent Publication Number: US-2018033755-A1

Title: Integrated circuit chip and display device including the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Korean Patent Application No. 10-2016-0097038 filed in the Korean Intellectual Property Office on Jul. 29, 2016, the entire contents of which are incorporated herein by reference. 
     BACKGROUND 
     (a) Technical Field 
     This disclosure relates to an integrated circuit chip and a display device including the same. 
     (b) Description of the Related Art 
     Display devices such as an organic light emitting device and a liquid crystal display include a display panel in which pixels for displaying an image are disposed. A pad portion for inputting or outputting signals is provided in the display panel to control an operation of the display panel, and an integrated circuit chip or a flexible printed circuit in which the integrated circuit chip is mounted is bonded in the pad portion. 
     An anisotropic conductive layer (ACF) is used for electrically and physically connecting the connection member and the pad portion. The anisotropic conductive layer as a film in which conductive particles are arranged on an insulating layer made of a resin material and the like has conductivity in a thickness direction thereof and has an insulation property in a surface direction. 
     The anisotropic conductive layer includes the conductive particles, and the conductive particles are positioned between a pad of the pad portion and a bump of the connection member while contacting them to electrically connect them. Further, as the resolution of the display device is increased, a size of the conductive particles is decreased, and the number of conductive particles is required to be increased in order to suppress an increase in resistance between pads and bumps. However, increasing the number of conductive particles may lead to short-circuit errors caused by aggregation of the conductive particles. Further, resistance deviation may be increased depending on the number of conductive particles positioned between the pads and the bumps. 
     The above information disclosed in this Background section is only for enhancement of understanding of the background and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. 
     SUMMARY 
     Exemplary embodiments have been made in an effort to provide an integrated circuit chip and a display device including the same, capable of improving reliability. 
     An exemplary embodiment provides a driving circuit chip including: a substrate; a terminal electrode disposed on the substrate; and an electrode pad disposed on the terminal electrode, wherein the electrode pad includes: a bump structure protruded from the substrate to include a short side and a long side; and a bump electrode disposed on the bump structure and connected with the terminal electrode around a short edge portion of the bump structure, wherein the bump electrode is disposed to not cover at least a part of a long edge portion of the bump structure. 
     The bump electrode may be disposed to not cover the long edge portion that is adjacent to the short edge portion of the bump structure. 
     The bump structure may have a planar shape that is substantially rectangular and a short-side directional cross-section that is substantially semi-circular. 
     The integrated circuit chip may further include an insulating layer disposed between the terminal electrode and the electrode pad, and the bump structure may not contact the terminal electrode. 
     The bump electrode may have a portion that contacts the insulating layer at opposite sides of the bump structure in a long-side direction of the bump structure. 
     The integrated circuit chip may further include an insulating layer disposed between the terminal electrode and the electrode pad, and the bump structure may contact the terminal electrode. 
     The bump electrode may have a portion that contacts the terminal electrode at opposite sides of the bump structure in a long-side direction of the bump structure. 
     The bump structure may be integrally disposed with the insulating layer. The bump structure may be overlapped with the terminal electrode, and a planar surface area of the terminal electrode may be wider than that of the bump structure. 
     The bump electrode may be disposed to not entirely cover the long edge portion of the bump structure. 
     An exemplary embodiment provides a display device including: a display panel including a pad portion; and an integrated circuit chip bonded to the pad portion. 
     According to the exemplary embodiments, it is possible to prevent crack generation by reducing a stress applied to the edge portion of the bump electrode of the driving circuit chip, and it is possible to prevent a crack which may be generated in the long edge portion from being expanded in the short-side direction. Accordingly, it is possible to improve connection reliability of the driving circuit chip. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top plan view schematically illustrating a display device according to an exemplary embodiment. 
         FIG. 2  is a top plan view schematically illustrating a driving circuit chip in the display device shown in  FIG. 1 . 
         FIG. 3  is a perspective view illustrating one electrode pad of a driving circuit chip according to an exemplary embodiment. 
         FIG. 4  is a top plan view of an electrode pad shown in  FIG. 3 . 
         FIG. 5  illustrates cross-sectional views taken along lines A-B, B-C, and C-D of  FIG. 4  according to an exemplary embodiment. 
         FIG. 6  illustrates a cross-sectional view taken along a line E-F of  FIG. 4  according to an exemplary embodiment. 
         FIG. 7  illustrates cross-sectional views taken along lines A-B, B-C, and C-D of  FIG. 4  according to an exemplary embodiment. 
         FIG. 8  illustrates cross-sectional views taken along lines A-B, B-C, and C-D of  FIG. 4  according to an exemplary embodiment. 
         FIG. 9  is a top plan view illustrating a mask used to form an electrode pad according to an exemplary embodiment. 
         FIG. 10  is a perspective view illustrating one electrode pad of a driving circuit chip according to an exemplary embodiment. 
         FIG. 11  is a perspective view illustrating one electrode pad of a driving circuit chip according to an exemplary embodiment. 
         FIG. 12  illustrates a stress simulation result of an electrode pad according to an example. 
         FIG. 13  illustrates a stress simulation result of an electrode pad according to a comparative example. 
         FIG. 14  is a cross-sectional view corresponding to one electrode pad and one pad region in the display device of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The inventive concept will be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the inventive concept are shown. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the inventive concept. 
     To clearly describe the embodiments, parts that are irrelevant to the description are omitted, and like numerals refer to like or similar constituent elements throughout the specification. 
     In the drawings, the size and thickness of each element are arbitrarily illustrated for ease of description, and the present disclosure is not necessarily limited to those illustrated in the drawings. In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. In the drawings, for better understanding and ease of description, the thicknesses of some layers and areas are exaggerated. 
     It will be understood that when an element such as a layer, film, region, or substrate is referred to as being “on” another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present. Further, in the specification, the word “on” or “above” means positioned on or above the object portion, and does not necessarily mean positioned on the upper side of the object portion based on a gravitational direction. 
     In addition, unless explicitly described to the contrary, the word “comprise” and variations such as “comprises” or “comprising” will be understood to imply the inclusion of stated elements but not the exclusion of any other elements. 
     Further, throughout the specification, the phrase “in a plan view” means viewing a target portion from the top, and the phrase “in a cross-sectional view” means viewing a cross-section formed by vertically cutting a target portion from the side 
     A display device according to an exemplary embodiment will now be described in detail with reference to the accompanying drawings. 
       FIG. 1  is a top plan view schematically illustrating a display device according to an exemplary embodiment. 
     Referring to  FIG. 1 , the display device according to an exemplary embodiment includes a display panel  10  and a flexible printed circuit  50  connected with the display panel  10 . The display panel  10  may be an organic light emitting device panel or a liquid crystal panel, but is not limited thereto. 
     The display panel  10  includes a display area DA for displaying an image, and a non-display area NA outside the display area DA in which elements and wires for generating and/or transmitting various signals applied to the display area DA and/or wiring are disposed. In  FIG. 1 , although only one side edge region (e.g., a lower region) of the display panel  10  is shown as the non-display area NA, the other side edge regions (e.g., left and right edges and/or an upper edge) of the display panel  10  may be the non-display area NA. The display area DA is shown to be quadrangular, but it may be circular, oval, or polygonal. 
     Pixels PX are disposed, for example, in a matrix in the display area DA of the display panel  10 . Further, signal lines such as gate lines (not shown), data lines (not shown), and the like are disposed in the display area DA. The gate lines substantially extend in a first direction D 1  (e.g., a row direction), and the data lines substantially extend in a second direction D 2  (e.g., a column direction) crossing the first direction D 1 . Each pixel PX may be connected to a gate line and a data line to receive a gate signal and a data signal from these lines. In the case of an organic light emitting device, driving voltage lines (not shown), which substantially extend, for example, in the second direction D 2  to transmit a driving voltage to the pixels PX, may be disposed in the display area DA. 
     A pad portion PP 1  for receiving an external signal is disposed in the non-display area NA of the display panel  10 . One end of the flexible printed circuit  50  is connected to the pad portion PP 1 . The other end of the flexible printed circuit  50  may be connected to, for example, an external printed circuit board (PCB) to transmit a signal such as an image data signal or a control signal thereto. 
     A driver for generating and/or processing various signals for driving the display panel  10  may be disposed in the non-display area NA of the display panel  10 , the flexible printed circuit  50 , or the external printed circuit board (PCB). The driver may include a data driver for applying a data signal to the data line, a gate driver for applying a gate signal to the gate line, and a signal controller for controlling the data driver and the gate driver. 
     In the shown exemplary embodiment, the data driver as a form of an integrated circuit chip  400  is mounted on a pad portion PP 2  disposed between the display area DA and the pad portion PP 1 . A non-conductive film (NCF) (not illustrated) including an adhesive may be disposed between the pad portion PP 2  and the integrated circuit chip  400  to bond the integrated circuit chip  400  to the pad portion PP 2 . In this case, electrode pads (not illustrated) of the integrated circuit chip  400  contact the pads (not illustrated) of the pad portion PP 2  and are electrically connected thereto. Unlike as illustrated, the data driver may be mounted on the flexible printed circuit  50  in a form of the integrated circuit chip to be connected to the pad portion PP 1  in a form of a tape carrier package (TCP). The gate driver may be integrated in the non-display area (not shown) of left and/or right edges of the display panel  10 , or may be provided as an integrated circuit chip. The signal controller may be formed as the integrated circuit chip  400  such as the data driver, or may be provided as a separate integrated circuit chip. 
     The overall configuration of the display device has been described. Hereinafter, the driving circuit chip  400  bonded to the pad portion PP 2  will be described in detail with reference to  FIG. 2  to  FIG. 6 .  FIG. 1  may also be referred to describe a relationship with the display panel  10 , and all the drawings previously referred to may be re-referred to without any special description. 
       FIG. 2  is a top plan view schematically illustrating a driving circuit chip in the display device shown in  FIG. 1 ,  FIG. 3  is a perspective view illustrating one electrode pad of a driving circuit chip according to an exemplary embodiment,  FIG. 4  is a top plan view of an electrode pad shown in  FIG. 3 ,  FIG. 5  illustrates cross-sectional views taken along lines A-B, B-C, and C-D of  FIG. 4  according to an exemplary embodiment, and  FIG. 6  illustrates a cross-sectional view taken along a line E-F of  FIG. 4  according to an exemplary embodiment. 
     Referring to  FIG. 2 , the driving circuit chip  400  includes a substrate  410  and electrode pads EP disposed on the substrate  410 . The electrode pads EP are independently formed. Each of the electrode pads EP has a planar shape that is substantially rectangular. Each electrode pad EP has long sides and short sides, and a long-side direction of the electrode pads EP attached to the display panel  10  may be substantially parallel with the second direction D 2 . Unlike the shown exemplary embodiment, each of the electrode pads EP may have another planar shape such as a parallelogram, and a long-side direction may be inclined to some degree with respect to the second direction D 2 . In each of the electrode pads EP, the long sides may be substantially the same as the short sides, and the planar shape may be modified in various ways. 
     A detailed structure of each electrode pad EP will be described with reference to  FIG. 3  to  FIG. 6 . Each of the electrode pads EP includes a bump structure  440  protruded from the substrate  410 , and a bump electrode  450  formed to surround the bump structure  440  while upwardly contacting the bump structure  440  but exposing a corner of the bump structure  440 . A terminal electrode  420  and a protection layer  430  are disposed between the substrate  410  and the electrode pads EP. 
     The substrate  410  may be a silicon substrate formed from a wafer. The terminal electrode  420  may be an output electrode or an input electrode of the integrated circuit. The terminal electrode  420  may be formed of a metal such as aluminum (Al), titanium (Ti), gold (Au), tungsten (W), copper (Cu), silver (Ag), and a metal alloy thereof. The terminal electrode  420  may be formed as a single layer or a multi-layer. For example, the terminal electrode  420  may be formed as a single layer including aluminum, and may be formed as a double layer including a lower layer including titanium and an upper layer including gold. The terminal electrode  420  may have a planar shape that is substantially rectangular including short sides and long sides. 
     The protection layer  430  disposed on the terminal electrode  420  may include an inorganic insulating material such as a silicon nitride (SiNx) or a silicon oxide (SiOx). The protection layer  430  may be formed to entirely cover the substrate  410  and the terminal electrode  420  except for a contact hole  435  contacted by the bump electrode  450 . 
     The bump structures  440  of the electrode pads EP are disposed on the protection layer  430 . The bump structures  440  are protruded from the substrate  410  at a predetermined height. Each of the bump structures  440  may have a planar shape that is substantially rectangular including short sides and long sides as shown in  FIG. 4  by dotted lines. The bump structures  440  may have a short-side (x) directional cross-section that is substantially semi-circular as shown in  FIG. 5 , and may have a long-side (y) directional cross-section that is substantially trapezoidal as shown in  FIG. 6 . Accordingly, each bump structure  440  may have a similar shape to a tunnel, but is not limited thereto. The bump structure  440  may have various  3 D shapes. The bump structure  440  is independently formed for each of electrode pads EP. 
     The bump structure  440  may have a curved surface except for a lower surface that contacts the protection layer  430 . In this specification, a portion of the curved surface of the bump structure  440  is referred to as an edge portion. Accordingly, the bump structure  440  includes two edge portions (hereinafter referred to as short edge portions) that are parallel with the short-side (x) direction and two edge portions (hereinafter referred to as long edge portions) that are parallel with the long-side (y) direction. 
     The bump structure  440  may be formed of an organic material or an inorganic material having appropriate elastic modulus, elastic deformation, and resiliency, and may include a polymer such as a resin. The bump structure  440  may include a conductive polymer. 
     The bump electrode  450  may be disposed on the bump structure  440 . When the integrated circuit chip  400  is bonded to the pad portion PP 2  of the display panel  10 , the bump electrode  450  contacts pads of the pad portion PP 2  to electrically connect the integrated circuit chip  400  to the display panel  10 . The bump electrode  450  is connected with the terminal electrode  420  through contact holes  435  formed in the protection layer  430  which is disposed at opposite sides of the bump structure  440  in the long-side (y) direction (accordingly, adjacent to the short edge portion of the bump structure  440 ). The number and position of the contact hole  435  may be variously changed. 
     The bump electrode  450  may be a multi-layer including a seed layer  452  and a metal layer  451 . The seed layer  452  serves as a base layer for growing the bump electrode  450  by, e.g., plating such as electroplating or electroless plating. The seed layer  452  may include a metal such as titanium, tungsten, chromium, and gold, and the metal layer  451  may include a metal such as gold, copper, silver, platinum, palladium, nickel, and aluminum. Unlike the shown exemplary embodiment, the bump electrode  450  may be a single layer, and may be formed by depositing a metal on the bump structure  440  by sputtering. 
     The bump electrode  450  entirely covers the bump structure  440  by surrounding the bump structure  440 . The bump electrode  450  may be formed to be generally wider than the bump structure  440 , and an edge portion of the bump electrode  450  that is not overlapped with the bump structure  440  may contact the protection layer  430  except for a portion that contacts the terminal electrode  420 . For example, as shown in a left side of  FIG. 5 , an edge portion of the bump electrode  450  in the long-side (y) direction may contact the protection layer  430 . As such, when the bump electrode  450  is formed to contact the protection layer  430  while covering the bump structure  440 , it is possible to prevent the bump electrode  450  from being pulled out or coming off. For example, when the integrated circuit chip  400  is manufactured, a back grinding process of grinding a rear surface of the substrate  410  in a state in which the integrated circuit chip  400  is fixed by attaching the electrode pads EP to an adhesive tape may be performed in order to reduce a thickness of the substrate  410 . While the adhesive tape is peeled off after the rear surface of the substrate  410  is ground, the bump electrode  450  may be separated by adhesiveness of the adhesive tape. According to the present exemplary embodiment, as the edge portion of the bump electrode  450  is formed to contact the protection layer  430  in the short-side (x) direction as well as in the long-side (y) direction, fixing power (attachment strength) of the bump electrode  450  may be increased to prevent the bump electrode  450  from being separated from the protection layer  430 . 
     The bump electrode  450  entirely covers the bump structure  440 , but does not cover a portion of an external circumferential surface of the bump structure  440 , particularly, the long edge portion of the bump structure  440  that is adjacent to the short edge portion of the bump structure  440 . Accordingly, the bump electrode  450  has openings  455  for exposing the long edge portion of the bump structure  440 . A height h 2  of the openings  455  from a surface of the protection layer  430  may be substantially ⅔ or less, ½ or less, or ⅓ or less as compared with a height h 1  of the bump structure  440 , but the embodiments are not limited thereto. The height h 2  may be variously designed. 
     The integrated circuit chip  400  is compressed in an operation in which the integrated circuit chip  400  is bonded to the pad portion PP 2  of the display panel  10 . In this case, the bump structure  440  is pushed and expanded by elasticity in a lateral direction (e.g., in a direction that crosses the pushing direction), and the bump electrode  450  surrounding the bump structure  440  is also expanded in the lateral direction. By a  3 D shape of the bump structure  440 , a stress caused by expansion of a first portion of the bump electrode  450  which is positioned around the long edge portion of the bump structure  440  (hereinafter referred to as a long edge portion of the bump electrode  450 ) is stronger than that of a second portion thereof which is positioned around the short edge portion of the bump structure  440  (hereinafter referred to as a short edge portion of the bump electrode  450 ). Accordingly, the short edge portion of the bump electrode  450  is more easily cracked or burst than the short edge portion of the bump electrode  450 . 
     The crack generated at a part of the long edge portion of the bump electrode  450  may be expanded to the short edge portion without being confined to the part. When the crack is expanded to the short edge portion, a connection between the bump electrode  450  and the terminal electrode  420  may be cut off, or resistance therein may be increased. According to the present exemplary embodiment, the openings  455  of the bump electrode  450  are formed at the long edge portion of the bump electrode  450  that is adjacent to the short edge portion thereof, and thus it is possible to block the crack from being expanded from the long edge portion to the short edge portion. Further, it is possible to maintain the fixing power by the long edge portion which contacts the protection layer  430  by forming the opening  455  at a portion that is adjacent to the short edge portion instead of entirely forming the opening  455  at the long edge portion. Meanwhile, when the bump structure  440  is gradually formed, e.g., the long edge portion of the bump structure  440  is formed at a lower height, the crack generation may be reduced at the long edge portion of the bump electrode  450 . 
     Hereinafter, electrode pads EP according to some other exemplary embodiments will be described based on differences thereof from the aforementioned exemplary embodiment with reference to  FIG. 7  and  FIG. 8 . 
       FIG. 7  and  FIG. 8  illustrate cross-sectional views taken along lines A-B, B-C, and C-D of  FIG. 4  according to an exemplary embodiment. 
     Referring to  FIG. 7 , in the present exemplary embodiment, the protection layer  430  is not disposed between the terminal electrode  420  and the bump structure  440  unlike in the aforementioned exemplary embodiments of  FIG. 3  to  FIG. 6  in which the protection layer  430  covers the terminal electrode  420  except for the contact hole  435 . Accordingly, a lower surface of the bump structure  440  contacts the terminal electrode  420 . The protection layer  430  is not disposed in a region in which the long edge portion of the bump electrode  450  is overlapped with the terminal electrode  420 . As a result, the long edge portion of the bump electrode  450  contacts the terminal electrode  420 . 
     According to the present exemplary embodiment, as an area of the bump electrode  450  contacting the terminal electrode  420  is increased, contact resistance may be ameliorated. As in the aforementioned exemplary embodiment, the openings  455  are formed at a portion that is adjacent to the short edge portion to block the crack generated at the long edge portion of the bump electrode  450  from being expanded to the short edge portion. Further, it is possible to maintain the separation strength by the long edge portion of the bump electrode  450  contacting the terminal electrode  420 . 
     Referring to  FIG. 8 , in the present exemplary embodiment, the protection layer  430  and the bump structure  440  are integrally formed and are integral, unlike in the aforementioned exemplary embodiments of  FIG. 3  to  FIG. 6  in which the protection layer  430  and the bump structure  440  are separately formed. Specifically, the protection layer  430  and the bump structure  440  may be formed of the same material without layer division. For example, the protection layer  430  and the bump structure  440  may be formed by making a region corresponding to the protection layer  430  relatively thinner through photolithography by thickly coating an organic material such as a photoresist on the substrate  410  and the terminal electrode  420  and using a two-tone mask such as a slit mask or a halftone mask. An example of the employed organic material may include a polymer material such as a polyimide-based material, a polybenzoxazole-based material, an acryl-based material, a phenol-based material, a silicon-based material, a silicon-modified polyimide-based material, an epoxy-based material, or the like. The protection layer  430  and the bump structure  440  may be cured by applying heat or irradiating UV. In this case, a surface of the bump structure  440  may be curvedly formed. 
     According to the present exemplary embodiment, the protection layer  430  and the bump structure  440  may be formed together by using one mask, thereby reducing processes and accomplishing cost efficiency. As in the aforementioned exemplary embodiment, the openings  455  may be opened at a portion that is adjacent to the short edge portion of the bump electrode  450 , and it is possible to maintain the separation strength by the long edge portion of the bump electrode  450  contacting the protection layer  430 . 
       FIG. 9  is a top plan view illustrating a mask used to form an electrode pad according to an exemplary embodiment. 
     The mask M shown in  FIG. 9  may be used to form the bump electrode  450  having the openings  455  by plating as in the aforementioned exemplary embodiments. For example, when the bump electrode  450  is formed by using a positive photoresist, the mask M includes transmissive regions TR corresponding to a planar shape of the bump electrode  450  shown in  FIG. 4 . The transmissive regions TR are disposed at distances corresponding to distances of the electrode pads EP to be formed. Non-transmissive regions NR are positioned to surround the transmissive regions TR. Accordingly, it is possible to form the bump electrode  450  having the openings  455  at the long edge portion that is adjacent to the short edge portion by removing a photoresist corresponding to the shape of the bump electrode  450  and growing the bump electrode  450  (specifically, the metal layer  451  disposed on the seed layer  452 ). When a negative photoresist is employed, positions of the transmissive regions TR and the non-transmissive regions NR of the mask M are opposite to each other. 
       FIG. 10  and  FIG. 11  are perspective views illustrating one electrode pad of a driving circuit chip according to an exemplary embodiment. 
     Referring to  FIG. 10 , the openings  455  are entirely formed at the long edge portion of the bump electrode  450 . In the exemplary embodiment of  FIG. 3 , the openings  455  are formed at opposite ends of the long edge portion of the bump electrode  450 . However, in the present exemplary embodiment, the openings  455  are connected to constitute one opening  455 . In this case, the long edge portion of the bump electrode  450  does not contact the protection layer  430  or the terminal electrode  420 , and thus the separation strength may be deteriorated, but the long edge portion may be prevented from being cracked or burst. 
     Referring to  FIG. 11 , the openings  455  are separately formed at the long edge portion of the bump electrode  450 . Compared with the exemplary embodiment of  FIG. 3 , at least one opening  455  is formed between the openings  455  formed at opposite ends of the long edge portion of the bump electrode  450 . In this case, it is possible to maintain fixing power while reducing a region of the long edge portion of the bump electrode  450  that may be cracked. 
     The exemplary embodiments of  FIG. 10  and  FIG. 11  are the same as the aforementioned exemplary embodiments in that the bump electrode  450  does not cover the long edge portion that is adjacent to the short edge portion of the bump structure  440 . Accordingly, it is possible to prevent crack expansion to the short edge portion. 
       FIG. 12  illustrates a stress simulation result of an electrode pad according to an example, and  FIG. 13  illustrates a stress simulation result of an electrode pad according to a comparative example. 
       FIG. 12  illustrates the case in which the bump electrode  450  is formed to not cover the long edge portion that is adjacent to the short edge portion of the bump structure  440  as in the exemplary embodiments, and  FIG. 13  illustrates the case in which the bump electrode  450  is formed to completely cover the long edge portion of the bump structure  440  (i.e., the bump electrode  450  has no opening). In the case of an analytic model shape, a radius of the bump structure  440  is 3 μm, and a thickness of the bump electrode  450  is 700 nm. When a predetermined pressure is applied to the bump electrode  450 , stresses were respectively measured at a point  1  which is a short-side center of the bump electrode  450  and a point  2  which is a long-side end as 1360 and 3630 MPa in the comparative example of  FIG. 13 . However, stresses respectively measured at the point  1  and the point  2  were respectively reduced to 1020 and 653 MPa in the example of  FIG. 12 . Accordingly, according to an exemplary embodiment, the stress is reduced at a short side of the bump electrode  450 , and thus it is possible to reduce crack generation possibility. 
     The integrated circuit chip  400  has been described. Hereinafter, a state in which the integrated circuit chip  400  is bonded to the pad portion PP 2  of the display panel  10  will be described. 
       FIG. 14  is a cross-sectional view corresponding to one electrode pad and one pad region in the display device of  FIG. 1 . 
     Electrode pads EP bonded to the pad portion PP 2  bonded to the display panel  10  will be described by using the electrode pads EP as an example. 
     The pad portion PP 2  includes pads P. The pads P may be arranged in, e.g., the first direction D 1  at a predetermined interval, and may be arranged in a single row or in a plurality of rows. 
     The pads P are disposed on the substrate  110  formed of glass or plastic, and each of the pads P includes a first pad electrode  210  and a second pad electrode  220 . A first end of the first pad electrode  210  may be connected with a signal line, such as a data line, of the display panel  10 . A protection layer  140  is disposed between the substrate  110  and the pads P. The protection layer  140  may be a barrier layer for preventing moisture penetration, a buffer layer, a gate insulating layer for insulating a semiconductor and a gate electrode, or a multilayer in which they are stacked. An interlayer insulating layer  160  is disposed between the first pad electrode  210  and the second pad electrode  220 . The second pad electrode  220  is connected with the first pad electrode  210  through a contact hole formed in the interlayer insulating layer  160 . 
     The electrode pads EP are disposed to overlap the pads P, and are downwardly protruded from the substrate  410  toward the pads P. The bump electrode  450  contacts the second pad electrode  220  corresponding to an upper layer of each of the pads P to electrically connect the terminal electrode  420  of the integrated circuit chip  400  to the pads P of the display panel  10 . Accordingly, a signal outputted from the terminal electrode  420  of the integrated circuit chip  400  may be transferred to the signal line of the display panel  10  through the bump electrode  450  and the pad P, and vice versa. 
     Most space between the integrated circuit chip  400  and the pad portion PP 2  is filled with a non-conductive adhesive layer  20 , and thus the integrated circuit chip  400  is bonded to the pad portion PP 2  by the adhesive layer  20 . The integrated circuit chip  400  may be bonded to the bump structure  440 , and may be bonded to the pad portion PP 2  in a state in which the bump electrode  450  is slightly compressed. In this case, for example, after a time has elapsed after bonding, even when a gap between the integrated circuit chip  400  and the pad portion PP 2  is increased, it is possible to maintain the contact between the bump electrode  450  and the pad P by an elastic restoring force of the bump structure  440 . The integrated circuit chip  400  is compressed in an operation in which the integrated circuit chip  400  is bonded to the pad portion PP 2 . In this case, the long edge portion of the bump electrode  450  may be cracked. The exemplary embodiments provide a structure of electrode pads EP capable of preventing crack expansion to the short edge portion. 
     While the inventive concept has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the inventive concept is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.