Flexible device and fabricating method thereof

A flexible device has a flexible panel, a driver, and a restraining component. The flexible panel includes a main region and a driver bonding region outside the main region. The driver is electrically connected to the driver bonding region. The restraining component is disposed adjacent to the driver bonding region. Rigidity of the restraining component is greater than rigidity of the flexible panel, and coefficient of thermal expansion of the restraining component is smaller than coefficient of thermal expansion of the flexible panel.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Taiwan application serial no. 99113983, filed on Apr. 30, 2010. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.

BACKGROUND OF THE PRESENT INVENTION

1. Field of the Present Invention

The present invention relates to a flexible device and a fabricating method thereof. More particularly, the present invention relates to a flexible display and a fabricating method thereof.

2. Description of Related Art

With rapid development of display technologies, conventional cathode ray tube (CRT) displays have been gradually replaced by flat panel displays (FPD). In comparison with the FPD formed by a rigid substrate (e.g. a glass substrate), a flexibly display in which an active device is formed on a flexible substrate has been developed according to recent researches because the flexible substrate (e.g. a plastic substrate) is characterized by flexibility and impact endurance.

In such case, the flexible substrate is often adhered to the rigid substrate, and then a series of film deposition processes can be performed to form a flexible display panel. Drivers (e.g. a scan driver and a data driver) are then adhered to the flexible display panel through an anisotropic conductive adhesive, such that conductive bumps of the drivers are electrically connected to pads of the flexible display panel through conductive particles in the anisotropic conductive adhesive, and that the flexible display panel is electrically connected to the drivers. After all the processes are completely performed, the flexible display panel is removed from the rigid substrate.

Since coefficient of thermal expansion (CTE) of the flexible substrate is relatively large in most cases, thermal stability of the flexible substrate is insufficient. During the fabricating process of the flexible display, significant stress is accumulated on the flexible substrate because the flexible substrate is expanded or contracted due to environmental variations in temperature. Therefore, when the flexible display panel is removed from the rigid substrate, the flexible substrate of the flexible display panel is contracted to a great extent, and the stress is released, which causes the conductive bumps between the drivers and the flexible display panel to be peeled off or broken. As such, electrical connection between the drivers and the flexible display panel is adversely affected, and the drivers cannot function. Besides, said stress may also deteriorate electrical connection between a flexible circuit board and the flexible display panel. On the other hand, in another conventional fabricating process, the active device is formed on the flexible substrate, and the flexible display panel is removed from the rigid substrate, so as to contract the flexible substrate. The drivers and the flexible display panel are then bonded, and subsequent package processes are performed. Nonetheless, during the bonding process of the drivers and the flexible display panel and other subsequent fabricating processes, the flexible substrate of the flexible display panel still undergoes different temperature variations. Accordingly, the expanded or contracted flexible substrate is likely to pose a negative impact on the electrical connection between the drivers and the flexible display panel or between the flexible circuit board and the flexible display panel.

SUMMARY OF THE PRESENT INVENTION

The present invention is directed to a flexible device and a fabricating method thereof in order to ensure favorable electrical connection between a flexible panel and a driver.

In the present invention, a flexible device including a flexible panel, a driver, and a restraining component is provided. The flexible panel has a main region and a driver bonding region outside the main region. The driver is electrically connected to the driver bonding region. The restraining component is disposed adjacent to the driver bonding region. Here, rigidity of the restraining component is greater than rigidity of the flexible panel, and coefficient of thermal expansion of the restraining component is smaller than coefficient of thermal expansion of the flexible panel

In the present invention, a fabricating method of a flexible device is provided as well. According to the fabricating method, a flexible panel is formed on a rigid substrate. The flexible panel has a main region and a driver bonding region outside the main region. A driver is bonded to the driver bonding region. A restraining component is formed adjacent to the driver bonding region. Here, rigidity of the restraining component is greater than rigidity of the flexible panel, and coefficient of thermal expansion of the restraining component is smaller than coefficient of thermal expansion of the flexible panel.

In the present invention, another flexible device including a flexible panel, a driver, and a restraining component is provided. The flexible panel has a main region and a driver bonding region outside the main region. The driver is electrically connected to the driver bonding region. The restraining component is disposed adjacent to the driver bonding region. Coefficient of thermal expansion of the restraining component is CTE, coefficient of thermal expansion of the flexible panel is CTEsSUB, and coefficient of thermal expansion of the driver is CTECHIP. Here, a difference |CTESUB−CTECHIP| between the coefficient of thermal expansion of the flexible panel and the coefficient of thermal expansion of the driver is greater than a difference |CTE−CTECHIP| between the coefficient of thermal expansion of the restraining component and the coefficient of thermal expansion of the driver.

Based on the above, the restraining component is disposed between the flexible panel and the driver according to the present invention. The coefficient of thermal expansion of the restraining component is smaller than that of the flexible panel, and therefore the contraction amount of the flexible panel can be restrained by the restraining component in order to prevent significant contraction of the flexible panel due to variations in temperature. Thereby, satisfactory electrical connection between the flexible panel and the driver can be ensured.

In order to make the aforementioned and other features and advantages of the present invention more comprehensible, embodiments accompanying figures are described in detail below.

DESCRIPTION OF EMBODIMENTS

FIG. 1AtoFIG. 1Eare schematic top views illustrating processes in a fabricating method of a flexible device according to an embodiment of the present invention.FIG. 2AtoFIG. 2Eare schematic cross-sectional views taken along lines A-A′ and B-B′ depicted inFIG. 1AtoFIG. 1E. As shown inFIG. 1AandFIG. 2A, a flexible panel110(e.g. a flexible display panel) is formed on a rigid substrate102. The flexible panel110has a main region112(e.g. display region), a driver bonding region114outside the main region112, and a flexible printed circuit (FPC) bonding region116. In the present embodiment, the rigid substrate102, for example, is a glass substrate, a quartz substrate, a silicon substrate, or any other substrate made of solid materials. The flexible panel110includes a flexible substrate111and a display unit113. The flexible substrate111, for instance, is a plastic substrate featuring great flexibility, and the flexible substrate111of the flexible panel110is adhered to the rigid substrate102. The display unit113is disposed on the flexible substrate111and located in the main region112. In the present embodiment, coefficient of thermal expansion CTESUBof the flexible panel110ranges from about 4 ppm/c to about 100 ppm/c, for example. In another embodiment of the present application, the flexible panel110may be formed by a roll-to-roll process.

A driver120is bonded to the driver bonding region114, as shown inFIG. 1BandFIG. 2B. According to the present embodiment, for example, the driver120and the driver bonding region114are bonded to each other by adhering an anisotropic conductive film (ACF)118onto the driver bonding region114and then pressing the driver120onto the ACF118, such that a plurality of conductive bumps122of the driver120can be electrically connected to the driver bonding region114through conductive particles in the ACF118, and that the driver120can be electrically connected to the flexible panel110. Here, the driver120is, for example, a silicon IC and has a pair of long sides121a, a pair of short sides121b, and thickness t1. Coefficient of thermal expansion CTECHIPof the driver120ranges from about 1 ppm/c to about 20 ppm/c, for example.

The fabricating method of the flexible device100can further include a step of bonding a flexible circuit126to the FPC bonding region116of the flexible panel110. The flexible circuit126and the FPC bonding region116, for example, can be bonded to each other by adhering the ACF118onto the FPC bonding region116and pressing the flexible circuit126onto the ACF118, such that the flexible circuit126is electrically connected to the FPC bonding region116through the ACF118, and that the flexible circuit126can be electrically connected to the flexible panel110. According to the present embodiment, the ACF118is used for adhering the driver120to the driver bonding region114and adhering the flexible circuit126to the FPC bonding region116, while people having ordinary skill in the pertinent art can also bond the driver120to the driver bonding region114or bond the flexible circuit126to the FPC bonding region116through other ways, e.g. by means of an anisotropic conductive adhesive.

With reference toFIG. 1CandFIG. 2C, a restraining component130(e.g. a contraction restraining component) is formed adjacent to or around the driver bonding region114. Rigidity of the restraining component130, for example, is greater than rigidity of the flexible panel110, and coefficient of thermal expansion CTE of the restraining component130, for example, is smaller than the coefficient of thermal expansion CTECHIPof the flexible panel110. In the present embodiment, the coefficient of thermal expansion CTE of the restraining component130ranges from about 1 ppm/c to about 30 ppm/c, for example, and the rigidity of the restraining component130ranges from about 3 Gpa to about 400 Gpa, preferably from about 8 Gpa to about 400 Gpa, for example. In addition, the difference |CTESUB−CTECHIP|, for instance, is greater than the difference |CTE−CTECHIP|. In the present embodiment, a material of the restraining component130can include metal, plastic, curable adhesive, or any other material. Here, the curable adhesive can be light curable adhesive, thermal curable adhesive, or a combination thereof. When the material of the restraining component130includes the curable adhesive, a method of curing the restraining component130further includes light irradiation (e.g. with use of visible light or ultraviolet light) or heating.

In the present embodiment, the restraining component130includes at least one first contraction restraining bar132and two second contraction restraining bars134, for instance. An extension direction of the first contraction restraining bar132is exemplarily parallel to a pair of long sides121aof the driver120, and the two second contraction restraining bars134are exemplarily connected to two ends of the first contraction restraining bar132. In addition, an extension direction of each of the second contraction restraining bars134, for example, is substantially perpendicular to the first contraction restraining bar132, i.e. the restraining component130is in a shape of the letter I, for instance. Thickness t2of the restraining component130(e.g. the second contraction restraining bar134) is greater than the thickness t1of the driver120, for instance. However, in other embodiments, the thickness t2of the restraining component130can also be smaller than or equal to the thickness t1of the driver120. In the present embodiment, a first direction D1is substantially parallel to the long sides121aof the driver120, and the contraction amount of the flexible panel110along the first direction D1is restrained by the restraining component130, for example. Namely, the rigidity of the restraining component130is greater than the rigidity of the flexible panel110, and the coefficient of thermal expansion CTE of the restraining component130is smaller than the coefficient of thermal expansion CTECHIPof the flexible panel110. Hence, on the condition of the same temperature variation, the flexible panel110is contracted or expanded to a better extent than the restraining component130with the relatively great rigidity, such that the restraining component130is capable of restraining expansion or contraction of the flexible panel110. The second contraction restraining bars134of the restraining component130can extend from the driver bonding region114to the FPC bonding region116according to the present embodiment, so as to better restrain contraction or expansion of the flexible panel110, which is however not limited in this invention. Based on actual design requirements, the restraining component130can exclusively cover the driver bonding region114or exclusively cover the FPC bonding region116.

A molding compound140is formed on the driver bonding region114to encapsulate the driver120, as shown inFIG. 1DandFIG. 2D. A material of the molding compound140is epoxy resin or any other insulating material, for example. In the present embodiment, the molding compound140further encapsulates the flexible circuit126that is connected to the flexible panel110, for instance. As such, the electrical connection between the driver120and the flexible panel110or the electrical connection between the flexible circuit126and the flexible panel110is not affected by the surroundings. Note that the step of forming the molding compound140can be omitted in other embodiments based on actual conditions and users' intention.

According to the present embodiment, after the restraining component130is formed, the fabricating method of the present embodiment further includes the step of removing the flexible panel110from the rigid substrate120to complete fabrication of the flexible device100, as shown inFIG. 1EandFIG. 2E.

In the previous embodiments, the flexible panel110is removed from the rigid substrate102after the restraining component130is formed. However, note that the flexible panel110can be removed from the rigid substrate102before the restraining component130is formed on the flexible panel110according to another embodiment. At this time, it is preferable to assess possible impact of temperature in the subsequent manufacturing processes and probable environmental impact on the flexible panel110, so as to allow the restraining component130to restrain contraction or expansion of the flexible panel110in the subsequent manufacturing processes. Besides, in an embodiment, the bonding process and the package process of the driver120and the flexible panel110can be performed after the flexible panel110is removed from the rigid substrate102, and the restraining component130can still effectively restrain contraction or expansion of the flexible panel110in the subsequent manufacturing processes, so as to protect an area where the flexible panel110is electrically connected to the driver120from being affected by the subsequently-performed thermal process or by environmental variations.

The flexible device100of the present embodiment includes the flexible panel110, the driver120, and the restraining component130. The flexible panel110has the main region112and the driver bonding region114outside the main region112. The driver120is electrically connected to the driver bonding region114. The restraining component130is disposed adjacent to the driver bonding region114. The rigidity of the restraining component130, for example, is greater than the rigidity of the flexible panel110, and the coefficient of thermal expansion CTE of the restraining component130, for example, is smaller than the coefficient of thermal expansion CTECHIPof the flexible panel110. Additionally, in the present embodiment, the flexible device100can further includes the flexible circuit126and the molding compound140. The flexible circuit126is disposed in the FPC bonding region116of the flexible panel110, and the molding compound140encapsulates the driver120.

According to the present embodiment, note that the rigidity of the restraining component130is greater than the rigidity of the flexible panel110, and the coefficient of thermal expansion CTE of the restraining component130is smaller than the coefficient of thermal expansion CTECHIPof the flexible panel110. However, in another embodiment, the rigidity of the restraining component130is not defined, while the coefficient of thermal expansion CTE of the restraining component130is required to comply with following conditions: the difference |CTESUB−CTECHIP| between the coefficient of thermal expansion CTESUBof the flexible panel110and the coefficient of thermal expansion CTECHIPof the driver120is greater than the difference |CTE−CTECHIP| between the coefficient of thermal expansion CTE of the restraining component130and the coefficient of thermal expansion CTECHIPof the driver120, for instance. In other words, the difference between the thermal expansion of the restraining component130and the thermal expansion of the driver120is less than the difference between the thermal expansion of the flexible panel110and the thermal expansion of the driver120, and thereby the restraining component130is able to restrain the contraction amount of the flexible panel110. Here, the coefficient of thermal expansion CTE of the restraining component130, for example, is between the coefficient of thermal expansion CTECHIPof the driver120and the coefficient of thermal expansion CTESUBof the flexible panel110. In an alternative, the coefficient of thermal expansion CTE of the restraining component130, for example, is smaller than the coefficient of thermal expansion CTECHIPof the driver120. Here, the coefficient of thermal expansion CTE of the restraining component130exemplarily ranges from about 1 ppm/c to about 30 ppm/c, the coefficient of thermal expansion CTESUBof the flexible panel110exemplarily ranges from about 4 ppm/c to about 100 ppm/c, and the coefficient of thermal expansion CTECHIPof the driver120exemplarily ranges from about 1 ppm/c to about 20 ppm/c. The rigidity of the restraining component130, for example, ranges from about 3 Gpa to about 400 Gpa, preferably from about 8 Gpa to about 400 Gpa.

Moreover, in the present embodiment, the restraining component130is formed after the driver120is bonded to the driver bonding region114, while the restraining component130in another embodiment can also be formed before the driver120is bonded to the driver bonding region114. In other words, the present invention does not limit the order of forming the restraining component130and bonding the driver120to the driver bonding region114. In addition, the material, the shape, and the thickness t2of the restraining component130(e.g. the second contraction restraining bar134), whether the molding compound140is formed, or the coverage of the molding compound140are not limited in the present invention.FIG. 3AtoFIG. 7Aare schematic top views illustrating a flexible device according to an embodiment of the present invention, andFIG. 3BtoFIG. 7Bare schematic cross-sectional views taken along the line A-A′ depicted inFIG. 1AtoFIG. 7A. As shown inFIG. 3AandFIG. 3B, the restraining component130in a flexible device100aof an embodiment includes a first contraction restraining bar132, two second contraction restraining bars134, and a third contraction restraining bar136, for instance. The two second contraction restraining bars134are connected to two ends of the first contraction restraining bar132. The third contraction restraining bar136is connected to a top of the first contraction restraining bar132and the tops of the second contraction restraining bars134, and the third contraction restraining bar136is located on the driver120. That is to say, the restraining component130has a lid structure, i.e. the first contraction restraining bar132and the two second contraction restraining bars134serve as sidewalls, and the third contraction restraining bar136serves as an upper lid. Thereby, the contraction amount of the flexible panel110can be restrained by the restraining component130. Besides, the restraining component130covers the driver120and a portion of the flexible circuit126, so as to further protect the electrical connection between the driver120and the flexible panel110or the electrical connection between the flexible circuit126and the flexible panel110from being affected by external surroundings.

It should be mentioned that the flexible device100aexemplarily shown inFIG. 3AandFIG. 3Bdoes not include the molding compound140, while a flexible device100a′ exemplarily shown inFIG. 4AandFIG. 4Bincludes the molding compound140. Space surrounded by the restraining component130is filled with the molding compound140, so as to encapsulate the driver120and cover the restraining component130and a portion of the flexible circuit126. In other embodiments not illustrated in the drawings, the molding compound140can exclusively cover the restraining component130but does not fill the space surrounded by the restraining component130.

As shown inFIG. 5AandFIG. 5B, the restraining component130in the flexible device100bof an embodiment includes two first contraction restraining bars132and two second contraction restraining bars134, for instance. Each of the second contraction restraining bars134is connected to two ends of each of the first contraction restraining bars132. According to the present embodiment, the thickness t2of the restraining component130is exemplarily smaller than the thickness t1of the driver120. However, the thickness t2of the restraining component130(e.g. the second contraction restraining bar134) can also be greater than or equal to the thickness t1of the driver120. A material of the restraining component130can include metal, plastic, curable adhesive, or any other material. Here, the curable adhesive can be light curable adhesive, thermal curable adhesive, or a combination thereof. When the material of the restraining component130includes the curable adhesive, a method of curing the restraining component130further includes light irradiation (e.g. with use of visible light or ultraviolet light) or heating. The flexible device100bexemplarily shown inFIG. 5AandFIG. 5Bdoes not include the molding compound140, while a flexible device100b′ exemplarily shown inFIG. 6AandFIG. 6Bfurther includes the molding compound140that encapsulates the driver120and covers the restraining component130and a portion of the flexible circuit126. During fabrication of the flexible devices100band100b′, the restraining component130is often formed before the driver120is formed.

As shown inFIG. 7AandFIG. 7B, the restraining component130in a flexible device100cof an embodiment includes a first contraction restraining bar132, two second contraction restraining bars134, and a third contraction restraining bar136, for example. The second contraction restraining bars134are connected to two ends of the first contraction restraining bar132. The third contraction restraining bar136is connected to the tops of the second contraction restraining bars134and is located on the flexible circuit126. Besides, the third contraction restraining bar136covers at least a portion of the FPC bonding region116and the flexible circuit126. Thereby, the contraction amount of the flexible panel110can be restrained by the restraining component130. Besides, the restraining component130covers the flexible circuit126, so as to further protect the electrical connection between the flexible circuit126and the flexible panel110from being affected by external surroundings. The flexible device100cexemplarily shown inFIG. 7AandFIG. 7Bdoes not include the molding compound140, while the flexible device100ccan further include the molding compound140that encapsulates the driver120and covers the restraining component130according to another embodiment that is not illustrated in the drawings.

According to the previous embodiments, the rigidity of the restraining component130is greater than the rigidity of the flexible panel110, and the coefficient of thermal expansion CTE of the restraining component130is smaller than the coefficient of thermal expansion CTECHIPof the flexible panel110. Alternatively, the difference |CTESUB−CTECHIP| between the coefficient of thermal expansion CTESUBof the flexible panel110and the coefficient of thermal expansion CTECHIPof the driver120is greater than the difference |CTE−CTECHIP| between the coefficient of thermal expansion CTE of the restraining component130and the coefficient of thermal expansion CTECHIPof the driver120. Therefore, the contraction amount of the flexible panel110can be restrained by the restraining component130in order to prevent significant contraction of the flexible panel110due to variations in temperature. Thereby, physical contact and satisfactory electrical connection between the flexible panel110and the driver120can be ensured. Furthermore, when the flexible panel110is removed from the rigid substrate102, the contraction amount of the flexible panel110is restrained by the restraining component130; therefore, the flexible panel110is not significantly contracted, and stress is not released thereby. As such, the conductive bumps122between the driver120and the flexible panel110are not peeled off or broken, satisfactory electrical connection between the driver120and the flexible panel110can be ensured, and the driver120can function in a normal manner.

Moreover, the restraining component130is disposed adjacent to the flexible circuit126, and thus electrical connection between the flexible panel110and the flexible circuit126can be further enhanced. Accordingly, the flexible device of the present invention has great electrical properties and improved yield.

In light of the foregoing, the restraining component is disposed between the flexible panel and the driver according to the present invention. The rigidity of the restraining component is greater than the rigidity of the flexible panel, and the coefficient of thermal expansion of the restraining component is smaller than the coefficient of thermal expansion of the flexible panel. Alternatively, the difference |CTESUB−CTECHIP| between the coefficient of thermal expansion of the flexible panel and the coefficient of thermal expansion of the driver is greater than the difference |CTE−CTECHIP| between the coefficient of thermal expansion of the restraining component and the coefficient of thermal expansion of the driver. Therefore, the contraction amount of the flexible panel can be restrained by the restraining component in order to prevent significant contraction or expansion of the flexible panel due to variations in temperature. In particular, when the flexible panel is removed from the rigid substrate, the contraction amount of the flexible panel can be restrained by the restraining component; therefore, the flexible panel is not significantly contracted, and thus stress is not released thereby. As such, the conductive bumps between the driver and the flexible panel are not peeled off or broken, satisfactory electrical connection between the driver and the flexible panel110can be ensured, and the driver can function in a normal manner. Moreover, the restraining component is disposed adjacent to the flexible circuit, and the electrical connection between the flexible panel and the flexible circuit can be further enhanced. Besides, in the process of removing the flexible panel from the rigid substrate and then bonding the flexible panel to the driver, the restraining component can effectively restrain contraction or expansion of the flexible panel in the subsequent manufacturing processes, so as to protect the flexible panel, the driver, and an area where the flexible panel is electrically connected to the driver from being affected by the subsequently-performed thermal process or by environmental variations. As a result, the flexible device of the present invention has great electrical properties and improved yield.

Although the present invention has been described with reference to the above embodiments, it will be apparent to one of the ordinary skill in the art that modifications to the described embodiment may be made without departing from the spirit of the present invention. Accordingly, the scope of the present invention will be defined by the attached claims not by the above detailed descriptions.