Patent Publication Number: US-2023144564-A1

Title: Folding plate and method for manufacturing same

Description:
TECHNICAL FIELD 
     The present disclosure relates to a folding plate and a method of manufacturing the folding plate. More particularly, the present disclosure relates to a folding plate capable of finding application in a multi-step foldable phone that is foldable in a multi-stepped manner and supporting a display, and a method of manufacturing the folding plate. 
     BACKGROUND ART 
     A foldable phone is manufactured using a flexible OLED display in such a manner that a screen thereof is foldable. The foldability of the foldable phone can increase portability thereof, and provides the advantage of possibly using a wider screen when the foldable phone is spread out. 
     A screen of the folder phone is folded or spread out using a hinge. When a folding plate is arranged on a rear surface of a display and is folded, a folding portion of the folding plate is fully folded up. When the folding plate is spread out, a flat wide screen appears without leaving boundary regions noticeable. 
     Importantly, the folding plate has to have such a degree of durability that it is capable of being tens of thousands of times folded and unfolded, and such a degree of mechanical durability that it is capable of supporting a display portion and protect the display portion from mechanical stress that can occur when the folding plate is folded. 
     In addition, there is a need for the folding plate to be manufactured in such a manner as to have a small thickness and to perform a heat dissipating function of dissipating heat occurring in the display. 
     SUMMARY OF INVENTION 
     Technical Problem 
     An object of the present disclosure is to provide a folding plate capable of finding application in a multi-step foldable phone in such a manner as to realize a wide display and supporting a display, and a method of manufacturing the folding plate. With this configuration, the folding phone can provide a high-performance effect of dissipating heat and contribute to reducing a thickness of the multi-step foldable phone. 
     Solution to Problem 
     In order to accomplish the above-mentioned object, according to an aspect of the present disclosure, there is provided a folding plate including: a plurality of supporting plates arranged in a row; and a plurality of elastic supporting plates, each connecting the plurality of supporting plate to each other. 
     In the folding plate, the plurality of supporting plates and the plurality of elastic supporting plates each have an upper surface that may form the same plane and a lower surface that may form the same plane. 
     In the folding plate, a junction region may be formed on one lateral side of the supporting plate or both lateral sides thereof, and a junction portion corresponding to the junction region may be formed on both lateral sides of the elastic supporting plate. In the folding plate, the junction region and the junction portion may each have a stepped surface. 
     The folding plate may further include a brazing filler arranged on the junction region or the junction portion and joining the junction region and the junction portion to each other. 
     In the folding plate, the elastic supporting plate may include a mesh portion formed in a center portion of the elastic supporting plate, a mesh pattern being formed in a lengthwise direction in the mesh portion; and a supporting portion arranged on both lateral sides of the mesh portion, the junction portion being formed on the supporting portion. 
     In the folding plate, the plurality of elastic supporting plates may be arranged as to be vertically inverted to each other with at least one of the plurality of supporting plates in between. In the folding plate, the elastic supporting plate may be folded in such a manner that both sides of the broader of upper and lower surfaces thereof face each other. 
     According to another aspect of the present disclosure, there is provided a method of manufacturing a folding plate, the method may include steps of: preparing a plurality of supporting plates; preparing a plurality of elastic supporting plates; and connecting in a row the plurality of supporting plates to each other using the plurality of elastic supporting plates. 
     In the method, in the step of preparing the plurality of supporting plates, the supporting plate on whose one lateral side or whose both lateral sides a stepped junction region is formed may be prepared, and the junction region may be formed by half-etching the one lateral side of the supporting plate or the both sides thereof. 
     In the method, in the step of preparing the plurality of elastic supporting plates, a mesh portion in a center portion of the elastic supporting plate may be formed, a supporting portion on both lateral sides of the mesh portion may be arranged, the elastic supporting plate having the supporting portion on which a junction portion is formed may be prepared, the mesh portion may be formed by photo-etching in a lengthwise direction a center portion of the elastic supporting plate, and the junction portion may be formed, as a stepped surface corresponding to the stepped junction region, by half-etching an edge of the supporting portion. 
     In the method, the step of connecting in a row the plurality of supporting plates to each other may include steps of: arranging a brazing filler on the junction region or the junction portion; and joining, by brazing, the junction region and the junction portion to each other in a state where the junction region and the junction portion overlap each other. 
     In the method, in the step of joining, by brazing, the junction region and the junction portion to each other, the plurality of elastic supporting plates may be joined as to be vertically inverted to each other with at least one of the plurality of supporting plates in between. 
     In the method, in the step of preparing the plurality of supporting plates, the supporting plate may be prepared as a supporting plate made of copper (Cu) foil. 
     In the method, in the step of preparing the plurality of elastic supporting plates, the elastic supporting plate may be prepared as an elastic supporting plate made of stainless steel (SUS). 
     Advantageous Effects of Invention 
     According to the present disclosure, a plurality of elastic supporting plate in each of which a mesh portion is formed connect a plurality of supporting plates to each other. Thus, a wide flat folding plate can be formed. 
     In addition, according to the present disclosure, plates made of a rigid metal material are used as the plurality of elastic supporting plates, and plates made of a metal material having a heat dissipating property are used as the plurality of supporting plates. Thus, in a case where the foldable plate finds application in a multi-step foldable phone, a function of supporting a display and a function of dissipating heat occurring in the display can be effectively performed. 
     In addition, the mesh portion is formed by etching a center portion of the elastic supporting plate having rigidity and thus has an elastic force that occurs with folding of the mesh portion. Thus, a display, when folded, is fully folded up, and when spread out, forms a flat plane without leaving a boundary region noticeable. 
     In addition, according to the present disclosure, a supporting portion is arranged on both lateral sides of the mesh portion and thus provides an elastic restoring force. Thus, the display, when unfolded in a folded state, can be flatly spread out without leaving the boundary region noticeable. 
     In addition, according to the present disclosure, the plurality of supporting plates and the plurality of elastic supporting plates have a stepped surface and are brazed thus the thickness of the multi-step foldable phone can be reduced and a durability thereof can be increased. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a view illustrating an example of a three-step foldable phone. 
         FIG.  2    is a plan view illustrating a folding plate according to an embodiment of the present disclosure. 
         FIG.  3    is a cross-sectional view illustrating the folding plate according to an embodiment of the present disclosure. 
         FIG.  4    is a cross-sectional view illustrating a method of manufacturing a folding plate according to an embodiment of the present disclosure. 
         FIG.  5    is a cross-sectional view illustrating a state where the folding plate in  FIG.  3    is folded up. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. 
     A folding plate according to a first embodiment of the present disclosure may find application in multi-step foldable phones capable of being folded in a multi-stepped manner. 
     As an example, a shape of the folding plate according to the present disclosure that finds application in a three-step foldable phone, among the multi-step foldable phones, is described. 
     The folding plate according to the first embodiment of the present disclosure may be joined to a rear surface of a display of the three-step foldable phone and thus may perform a function of dissipating heat generated by the display and supporting the display. The three-step foldable phone is a foldable phone (smartphone) having a triple display in which three screens are folded into the shape of the letter “Z.” 
       FIG.  1    illustrates a three-step foldable phone  10  in which a display  11  is folded around two vertical axes into the shape of the letter “Z.” One surface of the display  11  may be exposed to the outside in a state where the three-step foldable phone  10  is folded. 
     When the three-step foldable phone  10  is folded with a folding plate  100  (in  FIG.  2   ) being arranged on a rear surface of the display  11 , folding portions A and B may be fully folded up. When the three-step foldable phone  10  is spread out, a flat wide screen may appear without leaving boundary regions noticeable. 
     The folding plate according to the first embodiment of the present disclosure is described, taking as an example the shape of the three-step foldable phone illustrated in  FIG.  1   . It should be noted that, for the purpose of description, each of the constituent elements according to the first embodiment of the present disclosure may be illustrated in an exaggerated manner in the drawings. 
       FIG.  2    is a plan view illustrating a folding plate according to the first embodiment of the present disclosure. 
     As illustrated in  FIG.  2   , the folding plate  100  includes a plurality of supporting plates  110 ,  120 , and  130  that are arranged in a row, and a plurality of elastic supporting plates  140  and  150  that connect the plurality of supporting plates  110 ,  120 , and  130  to each other. 
     Specifically, the folding plate  100  includes a first supporting plate  110 , a second supporting plate  120 , a third supporting plate  130 , a first elastic supporting plate  140 , and a second elastic supporting plate  150 . In the folding plate  100 , the first elastic supporting plate  140  connects the first supporting plate  110  and the second supporting plate  120  to each other, and the second elastic supporting plate  150  connects the second supporting plate  120  and the third supporting plate  130  to each other. 
     Upper surfaces of the first supporting plate  110 , the second supporting plate  120 , the third supporting plate  130 , the first elastic supporting plate  140 , and the second elastic supporting plate that  150  that constitute the folding plate  100  may each form the same plane, and lower surfaces thereof may each form the same plane. Therefore, the folding plate  100  may have a more decreased thickness than when formed as multiple layers stacked on top of each other, and this may contribute to decreasing the thickness of the foldable phone. 
     The first supporting plate  110 , the second supporting plate  120 , and the third supporting plate  130  serve to perform a heat dissipating function and a supporting function. The first supporting plate  110 , the second supporting plate  120 , and the third supporting plate  130  are made of a metal material having a heat dissipation property. The first supporting plate  110 , the second supporting plate  120 , and the third supporting plate  130  may be made of Cu foil. Cu foil has the heat dissipating function and the supporting function. 
     The first elastic supporting plate  140  and the second elastic supporting plate  150  serve to perform the supporting function and a bending function. In order to perform the supporting function, the first elastic supporting plate  140  and the second elastic supporting plate  150  are made of a rigid metal material. 
     The first elastic supporting plate  140  and the second elastic supporting plate  150  may be made of a non-crystalline alloy or a stainless steel plate. For example, an amorphous alloy may be used as the non-crystalline alloy. The amorphous alloy has rigidity, but has a low etchability. In contract, the stainless steel plate has a high etchability, as well as rigidity. Therefore, the first elastic supporting plate  140  and the second elastic supporting plate  150  are made from the stainless steel plate. As an example, the stainless steel plate is made of SUS 304 stainless steel. 
       FIG.  3    is a cross-sectional view illustrating the folding plate according to the first embodiment of the present disclosure. 
     As illustrated in  FIG.  3   , in order to be bendable, the first elastic supporting plate  140  and the second elastic supporting plate  150  include mesh portions  141  and  151 , respectively. Specifically, the first elastic supporting plate  140  includes the mesh portion  141 , supporting portions  142 , and junction portions  143  and  144 , and the second elastic supporting plate  150  includes the mesh portion  151 , supporting portions  152 , and junction portions  153  and  154 . 
     The mesh portions  141  and  151  are formed in the lengthwise direction in center portions, respectively, of the first elastic supporting plate  140  and the second elastic supporting plate  150 . The supporting portions  142  are arranged on both lateral sides, respectively, of the mesh portions  141 . The supporting portions  152  are arranged on both lateral sides, respectively, of the mesh portions  151 . The junction portions  143  and  144  are formed on edges, respectively, of the supporting portion  142 . The junction portions  153  and  154  are formed on edges, respectively, of the supporting portion  152 . The mesh portions  141  and  151  serve to improve bendability of the elastic supporting plate  140  and bendability of the elastic supporting portion  150 , respectively. The supporting portions  142  and  152  serve to improve restoring forces, respectively, of the elastic supporting plates  140  and  150 . That is, the elastic supporting plates  140  and  150  are fully foldable with the mesh portions  141  and  151 , respectively, and may be flatly unfolded with the supporting portions  142  and  152 , respectively. 
     It is difficult to fold the first elastic supporting plate  140  and the second elastic supporting plate  150  that have rigidity. For this reason, the mesh portions  141  and  151  are formed in the center portions thereof, respectively. Accordingly, the first elastic supporting plate  140  and the second elastic supporting plate  150  may be provided with elastic forces, respectively, that occur with the folding of the mesh portions  141  and  151 . In addition, the supporting portions  142  in the shape of a plate may be formed on both lateral sides, respectively, of the mesh portion  141 , thereby providing restoring forces at the same time therefrom, and the supporting portions  152  in the shape of a plate may be formed on both lateral sides, respectively, of the mesh portion  151 , thereby providing restoring forces at the same time therefrom. Therefore, the elastic supporting plates  140  and  150 , when spread out, may each have a flat plane without leaving the boundary regions noticeable. 
     The junction portions  143  and  144  serve to join the elastic supporting plate  140  to the supporting plates  110  and  120 . The junction portions  153  and  154  serve to join the elastic supporting plate  150  to the supporting plates  120  and  130 . The junction portions  143  and  144  are referred to as a first junction portion  143  and a second junction portion  144 , respectively, that are formed on both lateral sides, respectively, of the first elastic supporting plate  140 . The junction portions  153  and  154  may be referred to as a third junction portion  153  and a fourth junction portion  154 , respectively, that are formed on both lateral sides, respectively, of the second elastic supporting plate  150 . 
     The mesh portions  141  and  151  are formed in the lengthwise direction in the center portions, respectively, of the elastic supporting plates  140  and  150 . The mesh portions  141  and  151  each has a fixed width and are foldable in the widthwise direction. The mesh portions  141  and  151  may each serve as both a support body and a spring. 
     The first elastic supporting plate  140  may be formed between the first supporting plate  110  and the second supporting plate  120  of the folding plate  100  in such a manner as to join them to each other. The second elastic supporting plate  150  may be formed between the second supporting plate  120  and the third supporting plate  130  of the folding plate  100  in such a manner as to join them to each other. 
     A plurality of mesh portions  141  and  151  may be formed, by etching, in a large-sized metal plate having rigidity. Then, the resulting large-sized metal plate may be cut into a plurality of elastic supporting plates  140  and  150  to be used. Accordingly, unnecessary etching is not performed, and the cost for etching can be reduced. 
       FIG.  4    is a cross-sectional view illustrating a method of manufacturing a folding plate according to an embodiment of the present disclosure. 
     As illustrated in  FIG.  4   , the first supporting plate  110  includes a first plate portion  111  and a first junction region  112 . The first junction region  112  is formed on a bottom surface at one side of the first supporting plate  110 . The second supporting plate  120  includes a second plate portion  121 , a second junction region  122 , and a third junction region  123 . The second junction region  122  is formed on a bottom surface at one side of the second supporting plate  120 , and the third junction region  123  is formed on an upper surface at the other side of the second supporting plate  120 . The third supporting plate  130  includes a third plate portion  131  and a fourth junction region  132 . The fourth junction region  132  is formed on an upper surface at one side of the third supporting plate  130 . 
     The first junction portion  143  that is joined to the first junction region  112  of the first supporting plate  110  is formed on an upper surface at one side of the first elastic supporting plate  140 . The second junction portion  144  that is joined to the second junction region  122  of the second supporting plate  120  is formed on an opposite upper surface at the other side of the first elastic supporting plate  140 . 
     The third junction portion  153  that is joined to the third junction region  123  of the second supporting plate  120  is formed on a lower surface at one side of the second elastic supporting plate  150 . The fourth junction portion  154  that is joined to the fourth junction region  132  of the third supporting plate  130  is formed on an opposite lower surface at the other side of the second elastic supporting plate  150 . 
     In this configuration, the first elastic supporting plate  140  and the second elastic supporting plate  150  may be arranged as to be vertically inverted to each other with at least one of the plurality of supporting plates  110 ,  120 , and  130  in between. In the folding plate according to an embodiment of the present disclosure, the first elastic supporting plate  140  and the second elastic supporting plate  150  may be arranged as to be vertically inverted to each other with the second supporting plate  120  in between, and may connect between the plurality of support plates  110 ,  120 , and  130 . 
     Specifically, the first junction portion  143  at one side of the first elastic supporting plate  140  may be joined to the first junction region  112  of the first supporting plate  110 , and the second junction portion  144  at the other side of the first elastic supporting plate  140  may be joined to the second junction region  122  of the second supporting plate  120 . Thus, the first supporting plate  110  and the second supporting plate  120  may be connected to each other. 
     The third junction portion  153  at one side of the second elastic supporting plate  150  may be joined to the third junction region  123  of the second supporting plate  120 , and the fourth junction portion  154  at the other side of the second elastic supporting plate  150  may be joined to the fourth junction region  132  of the third supporting plate  130 . Thus, the second supporting plate  120  and the third supporting plate  130  may be connected to each other. 
     The first to fourth junction regions  112 ,  122 ,  123 , and  132 , and the first to fourth junction portions  143 ,  144 ,  153 , and  154  are stepped surfaces. Specifically, the first junction region  112  of the first supporting plate  110 , the second junction region  122  and the third junction region  123  of the second supporting plate  120 , and the fourth junction region  132  of the third supporting plate  130  are stepped surfaces formed by half-etching the first supporting plate  110 , the second supporting plate  120 , and the third supporting plate  130 , respectively. The first junction portion  143  and the second junction portion  144  of the first elastic supporting plate  140  are stepped surfaces formed by half-etching both lateral sides, respectively, of the first elastic supporting plates  140 . The third junction portion  153  and the fourth junction portion  154  of the second elastic supporting plate  150  are stepped surfaces formed by half-etching both lateral sides, respectively, of the second elastic supporting plate  150 . 
     The first supporting plate  110 , the second supporting plate  120 , the third supporting plate  130 , the first elastic supporting plate  140 , and the second elastic supporting plate  150  have the same thickness. In addition, the first to fourth junction regions  112 ,  122 ,  123 , and  132  and the first to fourth junction portions  143 ,  144 ,  153 , and  154  are each thinned by half-etching in such manner as to have a thickness that is half a thickness of each of the plurality of supporting plates  110 ,  120 , and  130  and the elastic supporting plates  140  and  150 . 
     Therefore, respective joined portions of the first junction region  112  and the first junction portion  143 , respective joined portions of the second junction region  122  and the second junction portion  144 , respective joined portions of the third junction region  123  and the third junction portion  153 , and respective joined portions of the fourth junction region  132  and the fourth junction portion  154  have the same thickness as the plurality of supporting plates  110 ,  120 , and  130  and the plurality of elastic supporting plates  140  and  150 . In addition, upper surfaces of the plurality of supporting plates  110 ,  120 , and  130  and the plurality of elastic supporting plates  140  and  150  may form the same plane with respect to each other, and lower surfaces thereof may also form the same plane with respect to each other. 
     The mesh portions  141  and  151  may each be formed in a mesh pattern in which a plurality of lines long in the upward-downward direction intersect. The mesh portions  141  and  151  have to have such a degree of durability that they are capable of being tens of thousands of times folded and unfolded. Therefore, in mesh patterns of the mesh portions  141  and  151 , the plurality of lines long in the upward-downward direction are arranged in such a manner as to be spaced away from each other in a transverse direction, but in such a manner as to partly intersect each other in an overlapping fashion. Thus, the durability can be increased. 
     The mesh portions  141  and  151  are formed by photo-etching the center portions, respectively, of the elastic supporting plates  140  and  150 . When the mesh portions  141  and  151  are formed by perforating by a press, the mesh patterns thereof are not precise. When the mesh patterns are not precise, it is difficult to form the mesh portions that have a desired elastic force. 
     The elastic supporting plates  140  and  150  may be made of SUS 304 stainless steel. The elastic supporting plates  140  and  150 , when made of SUS 304, has a high etchability and thus may form a mesh pattern in a desired shape. SUS 304 stainless steel may be used with a thickness of 0.1 mm to 0.5 mm (100 μm to 150 μm). 
     In the mesh patterns of the mesh portions  141  and  151 , the plurality of lines each have a line-width L of 80 μm to 120 μm, and a distance S between each of the plurality of lines is 100 μm to 300 μm. As one practical example of the present disclosure, in the mesh patterns of the mesh portions  141  and  151 , the plurality of lines each have the line-width L of 100 μm, and the distance S between each of the plurality of lines is 200 μm. In the mesh patterns of the mesh portions  141  and  151 , it is preferable that the plurality of lines each have the line-width L of 100 μm. 
     A brazing filler  160  may be arranged in the first to fourth junction regions  112 ,  122 ,  123 , and  132  or the first to fourth junction portions  143 ,  144 ,  153 , and  154 . The brazing filler  160  may be formed as a multi-layered thin film. The multi-layered thin film serves to compensate for insufficient function and increase an adhesive power. 
     The brazing filler  160  may be a brazing alloy layer and may include an Ag layer and a Cu layer. The brazing filler  160  may further include a seed layer for increasing a force for attaching the brazing alloy layer and a base metal to each other. Examples of the base metal include the first elastic supporting plate  140 , the second elastic supporting plate  150 , the first supporting plate  110 , the second supporting plate  120 , and the third supporting plate  130 . 
     The seed layer may contain at least one of copper (Cu) and titanium (Ti). The seed layer may include a first seed layer and a second seed layer. In this case, the first seed layer may be formed of titanium (Ti), and the second seed layer may be formed of copper Cu. 
     The brazing filler  160  may be used to join, by brazing, the supporting plates  110 ,  120 , and  130  made of copper (Cu), a metal having a high melting point, to the elastic supporting plates  140  and  150  made of stainless steel. The brazing filler  160  may have a thickness of 5 μm to 10 μm. For example, the brazing filler  160  may include an Ag layer and a Cu layer formed on an upper layer of the Ag layer and may have a thickness of 5 μm. Alternatively, the brazing filler  160  may include the Ag layer, the Cu layer formed on the upper surface of the Ag layer, and an Ag layer formed on an upper surface of the Cu layer and may have a thickness of 5 μm. 
     A Ti layer may be formed in such a manner as to have a thickness of 0.1 μm to 0.2 μm. The Cu layer may be formed in such a manner as to have a thickness of 0.2 μm to 0.5 μm. The Ag layer formed on top of the Cu layer may be formed in such a manner as to have a thickness of 1.5 μm. The Cu layer formed on top of the Ag layer may be formed in such a manner as to have a thickness of 1.5 μm. The Ag layer formed on top of the Cu layer may be formed in such a manner as to have a thickness of 2 μm. 
     Alternatively, the Ti layer may be formed in such a manner as to have a thickness of 0.1 μm to 0.2 μm, the Cu layer may be formed in such a manner as to have a thickness of 0.2 μm to 0.5 μm, the Ag layer formed on top of the Cu layer may be formed in such a manner as to have a thickness of 1.5 μm, the Cu layer formed on top of the Ag layer may be formed in such a manner as to have a thickness of 2 μm, and the Ag layer formed on top of the Cu layer may be formed in such a manner as to have a thickness of 1.5 μm. 
     The stepped junction regions  112  and  122  may be formed on opposing lateral sides, respectively, of the supporting plate  110  and  120 . The stepped junction regions  123  and  132  may be formed on opposing lateral sides, respectively, of the supporting plate  120  and  130 . The stepped junction portions  143  and  144  may be formed on both lateral sides, respectively, of the elastic supporting plate  140 . The stepped junction portions  153  and  154  may be formed on both lateral sides, respectively, of the elastic supporting plate  150 . The junction portions  143  and  144  may be joined, by brazing, to the junction regions  112  and  122 , respectively. The junction portions  153  and  154  may be joined, by brazing, to the junction regions  123  and  132 , respectively. Because of this, the folding plate  100  according to the first embodiment of the present disclosure may be integrally formed thinly in such a manner as to have a minimum thickness of 0.1 mm. A thickness of the folding plate  100  may be suitably designed, considering a thickness of the display  11 . 
     In addition, the folding plate  100  is formed by joining a copper plate to both sides of a plate made of a stainless material. This has the excellent effect of dissipating heat. Moreover, the advantage of possibly further simplifying a manufacturing process can be provided. A temperature when joining is performed by brazing may range 850° C. to 950° C. 
       FIG.  5    is a cross-sectional view illustrating a state where the folding plate in  FIG.  3    is folded.  FIG.  5    illustrates in an exaggerated manner the state where the folding plate  100  is folded. For convenience, an illustration of the display  11  (in  FIG.  1   ) that is folded along with the folding plate  100  is omitted. 
     As illustrated in  FIG.  5   , the mesh portion  141  of the first elastic supporting plate  140  is folded outward, and thus the first supporting plate  110  and the second supporting plate  120  of the folding plate  100  may face each other with a space S 1  in between, In addition, the mesh portion  151  of the second elastic supporting plate  150  is folded inward, and thus the second supporting plate  120  and the third supporting plate  130  may face each other with a space S 2  in between. 
     In this manner, since the mesh portions  141  and  151  have the elastic forces that occur with the folding thereof, the folding plate  100  may be fully folded outward and inward, respectively. In addition, the folding plate  100 , when spread out in a folded state, may be flatly unfolded by the restoring forces provided by the supporting portions  142  and  152  in the shape of a plate without leaving the boundary regions noticeable (refer to  FIG.  3   ). 
     In addition, the first elastic supporting plate  140  may be folded in such a manner that both sides of the broader of upper and lower surfaces of the first elastic supporting plate  140  face each other. In the same manner, the second elastic supporting plate  150  may be folded in such a manner that both sides of the broader of upper and lower surfaces of the second elastic supporting plate  150  face each other. The supporting portions  142  arranged on both lateral sides, respectively, of the mesh portion  141 , and the supporting portions  152  arranged on both lateral sides, respectively, of the mesh portion  151  serve to provide elastic restoring forces. The broader of the upper and lower surfaces of the elastic supporting plate  140  corresponds to a portion of the supporting portion  142  that is formed to have a greater area. The broader of the upper and lower surfaces of the elastic supporting plate  150  corresponds to a portion of the supporting portion  152  that is formed to have a greater area. In this manner, when the portion of the supporting portion  142  that is formed to have a greater area is folded in such a manner that both sides thereof face each other, in a case where the supporting portion  142  is spread out, the elastic restoring force is easier to provide than when the portion of the supporting portion  142  that is formed to have a smaller area is folded. This is true for the supporting portion  152 . The display  11 , when spread out in the folded state, may be flatly unfolded by the elastic restoring forces of the supporting portions  142  and  152 , without leaving the boundary regions noticeable. 
     A method of manufacturing a folding plate according to a second embodiment of the present disclosure may include: a step of preparing a plurality of supporting plates  110 ,  120 , and  130 ; a step of preparing a plurality of elastic supporting plates  140  and  150 ; and a step of connecting the plurality of supporting plates  110 ,  120 , and  130  in a row using the plurality of elastic supporting plates  140  and  150 . 
     Specifically, the method of manufacturing a folding plate may include: a step of preparing a first supporting plate  110 , a second supporting plate  120 , and a third supporting plate  130  on which junction regions  112 ,  122 ,  123 , and  132 , respectively, are formed; a step of forming junction portions  143 ,  144 ,  153 , and  154  that correspond to the junction regions  112 ,  122 ,  123 , and  132 , respectively, and preparing a first elastic supporting plate  140  and a second elastic supporting plate  150 , mesh portions  141  and  151  being formed in a lengthwise direction on center portions, respectively, of the first elastic supporting plate  140  and the second elastic supporting plate  150 ; a step of arranging a brazing filler  160  on the junction regions  112 ,  122 ,  123 , and  132  or junction portions  143 ,  144 ,  153 , and  154 ; a step of arranging the first elastic supporting plate  140  between the first supporting plate  110  and the second supporting plate  120  and arranging the second elastic supporting plate  150  between the second supporting plate  120  and the third supporting plate  130  in such a manner that the junction regions  112 ,  122 ,  123 , and  132  overlap the junction portions  143 ,  144 ,  153 , and  154 , respectively; and a step of joining, by brazing, the junction regions  112 ,  122 ,  123 , and  132  and the junction portions  143 ,  144 ,  153 , and  154 , respectively. 
     In the step of preparing the first supporting plate, the second supporting plate, and the third supporting plate, the stepped junction region  112  may be formed by half-etching one lateral side of the first supporting plate  110 , the stepped junction regions  122  and  123  by half-etching both lateral sides, respectively, of the second supporting plate  120 , and the stepped junction region  132  by half-etching one lateral side of the third supporting plate  130 . 
     In the step of preparing the first elastic supporting plate and the second elastic supporting plate, the junction portions  143  and  144  may be formed, as stepped surfaces, by half-etching edges, respectively, of supporting portions  142  arranged on both lateral sides, respectively, of the mesh portion  141 . The junction portions  153  and  154  may be formed, as stepped surfaces, by half-etching edges, respectively, of supporting portions  152  arranged on both lateral sides, respectively, of the mesh portion  151 . In addition, the mesh portions  141  and  151  may be formed by photo-etching center portions, respectively, of the first elastic supporting plate  140  and the second elastic supporting plate  150 . 
     When the mesh portions  141  and  151  are formed by perforating by a press, a mesh pattern is difficult to precisely form, and thus is formed by photo-etching. In a case where the mesh portions  141  and  151  are formed by the photo-etching, the mesh pattern may be precisely formed. As illustrated in  FIG.  2   , the mesh pattern is formed by arranging the plurality of lines long in the upward-downward direction in such a manner as to intersect each other. 
     In the step of preparing the first supporting plate, the second supporting plate, and the third supporting plate, the first supporting plate  110 , the second supporting plate  120 , and the third supporting plate  130  may be prepared as supporting plates made of Cu foil. 
     In the step of preparing the first elastic supporting plate and the second elastic supporting plate, the first elastic supporting plate  140  and the second elastic supporting plate  150  may be prepared as elastic supporting plates made of stainless steel (SUS). 
     A stainless steel (SUS grade stainless steel) plate has rigidity and thus is readily used as a supporting plate for supporting the display, but has a low-level heat dissipation property. Therefore, the first supporting plate  110 , the second supporting plate  120 , and the third supporting plate  130  are made of copper foil, and the heat dissipation properties thereof may be enhanced. The elastic supporting plates  140  and  150  may be prepared as elastic supporting plates made of SUS 304 stainless steel. 
     The brazing filler  160  may include an Ag layer and a Cu layer. 
     The brazing filler  160  may be arranged, in the form of Bag  8  foil, plating filler metal, or paste, on the junction region  112  of the supporting plate  110 , the junction regions  122  and  123  of the supporting plate  120 , and the junction region  132  of the supporting plate  130 , or the junction portions  143  and  144  of the elastic supporting plate  140  and the junction portions  153  and  154  of the elastic supporting plate  150 . 
     In the step of joining, by brazing, the junction regions  112 ,  122 ,  123 , and  132  and the junction portions  143 ,  144 ,  153 , and  154 , respectively, the first elastic supporting plate  140  and the second elastic supporting plate  150  may be arranged as to be vertically inverted to each other with one of the plurality of supporting plates  110 ,  120 , and  130  in between, and may connect between the plurality of support plates  110 ,  120 , and  130 . Specifically, the first elastic supporting plate  140  and the second elastic supporting plate  150  may be joined as to be vertically inverted to each other with the second supporting plate  120  in between, and may connect the supporting plates  110 ,  120 , and  130 . 
     The reason for arranging the elastic supporting plates  140  and  150  in this manner is to arrange a flat surface of the elastic supporting plates  140  and  150  on which the junction portions  153  and  154  are not formed and which has a broader area, at a position for inward folding, that is, at a position for positioning both sides of the flat surface in such a manner as to face each other when the elastic supporting plates  140  and  150  is folded. When the portion of the elastic supporting plate  140  that has a greater area, as described above, is positioned at the position for inward folding, it is easier for the supporting portions  142  arranged on both lateral sides, respectively, of the mesh portion  141  to provide the elastic restoring force. When the portion of the elastic supporting plate  150  that has a greater area, as described above, is positioned at the position for inward folding, it is easier for the supporting portions  152  arranged on both lateral sides, respectively, of the mesh portion  151  to provide the elastic restoring force. 
     The junction regions  112 ,  122 ,  123 , and  132  and the junction portions  143 ,  144 ,  153 , and  154  are formed as stepped surfaces. Accordingly, the elastic supporting plate  140  is joined to each of the supporting plates  110  and  120  by bringing the stepped surfaces into contact with each other, and the elastic supporting plate  150  is joined to each of the supporting plates  120  and  130  by bringing the stepped surfaces into contact with each other. Accordingly, the effect of increasing respective junction areas of the elastic supporting plates  140  and  150  and the supporting plates  110 ,  120 , and  130  and thus enhancing a joining strength is provided. The stepped surface, when formed by flattening by a press, has a low level of flatness, and thus the joining strength is decreased. For this reason, the stepped surface is formed by half-etching. The etching improves the level of flatness and contributes to increasing the joining strength. 
     In the step of performing joining by brazing, a temperature for joining by brazing may range from 850° C. to 950° C. 
     In the folding plate  100  manufactured by the method according to an embodiment of the present disclosure, upper surfaces of the elastic supporting plates  140  and  150  and the supporting plates  110 ,  120 , and  130  form the same plane, and lower surfaces thereof form the same plane. The elastic supporting plates  140  and  150  and the supporting plates  110 ,  120 , and  130  may each have a thickness of 0.1 mm to 0.15 mm (100 μm to 150 μm). As an example, when the elastic supporting plates  140  and  150  and the supporting plates  110 ,  120 , and  130  each have a thickness of 150 μm, the junction regions  112 ,  122 ,  123 , and  132  and the junction portions  143 ,  144 ,  153 , and  154 , which are formed by half-etching, each have a thickness of 75 μm. 
     In addition, the supporting plates  110 ,  120 , and  130  joined to both lateral sides, respectively, of the elastic supporting plates  140  and  150  are made of a heat dissipating material. Thus, the folding plate  100  has a high-level heat dissipating property. 
     In addition, the elastic supporting plates  140  and  150  are made of a material having rigidity. The elastic supporting plates  140  and  150  include the mesh portions  141  and  151 , respectively, in the center portions thereof, and thus each have the elastic forces that occur with the folding thereof. Accordingly, the folding plate  100 , when bent, may be fully folded up, and when spread out, may have a flat surface without leaving the boundary regions noticeable. 
     In addition, the mesh portions  141  and  151  are formed in a mesh pattern in the folding plate  100 . In the mesh pattern, the plurality of lines long in the upward-downward direction are arranged in such a manner as to intersect. Thus, the durability of the mesh portions can be secured. 
     The folding plate described above finds application in the three-step foldable phone that has the triple display in which three screens are folded into the shape of the letter “Z,” and thus may support the display. 
     The folding plate  100  described above is attached to the rear surface of the display  11 . While the mesh portions  141  and  151  of the folding plate  100  are folded, the display is folded in an elastically transformed manner. When the display is spread out, the supporting portions  142  arranged on both lateral sides, respectively, of the mesh portion  141  and the supporting portions  152  arranged on both lateral sides, respectively, of the mesh portion  151  provide the elastic restoring forces. Thus, the display may be flatly unfolded without leaving the boundary regions noticeable. 
     In addition, in the folding plate  100 , the first supporting plate  110  and the second supporting plate  120  joined to both lateral sides, respectively, of the first elastic supporting plate  140 , and the second supporting plate  120  and the third supporting plate  130  joined to both lateral sides, respectively, of the second elastic supporting plate  150  are made of a heat dissipating material. Thus, heat occurring in the display may be quickly dissipated. 
     The folding plate  100  may find application in a four-step or five-step foldable phone, depending on the number of supporting plates and the number of elastic supporting plates connecting the supporting plates to each other. 
     The preferred embodiments of the present disclosure are described above with reference to the drawings. Specific terms are used throughout the specification for the purpose of describing the embodiments of the present disclosure, without any limitation being imposed on the meanings thereof and the scope of the present disclosure that is defined by the claims. From the present specification, it would be understandable to a person of ordinary skill in the art that various modifications to the embodiments and other equivalent embodiments are possible. Therefore, the proper technical scope of the present disclosure should be determined by the technical idea that is defined in the following claims.