Abstract:
An over-voltage protection device includes a substrate, an insulation layer having a depression over the substrate, a conductor layer having a first electrode and a second electrode over the insulation layer, wherein the first electrode and the second electrode form a discharge path, and the depression is under the discharge path. A method for preparing the over-voltage protection device includes the steps of forming an insulation layer over a substrate; forming a depression in the insulation layer; forming a photoresist pattern filling the depression and protruding the insulation layer; forming a conductor layer over the insulation layer; and removing the photoresist pattern, wherein the photoresist pattern divides the conductor layer into a first electrode and a second electrode that form a discharge path, and the depression is under the discharge path after the removal of the photoresist pattern.

Description:
TECHNICAL FIELD 
     The present disclosure relates to an over-voltage protection device and method for preparing the same, and more particularly, to an over-voltage protection device utilizing an air discharge technique and method for preparing the same. 
     DISCUSSION OF THE BACKGROUND 
     Abnormal voltages or electrostatic discharges (ESD) occurring in electronic circuit operations have the potential to severely damage electronic devices. To avoid such damage, it is typical to equip an over-voltage protection device to prevent the electronic devices from being influenced by the abnormal voltages or electrostatic discharges. 
     In current electronic products, the size of the electronic devices shrinks as the fabrication techniques advance, and as a result, the risk of damage by electrostatic discharge becomes more likely to occur. In addition, rapidly changing portable mobile electronics have an ever-increasing demand for electrostatic discharge protection. There are many electrostatic discharge protection techniques that are used to solve the above issues, and of these techniques, air discharge is the most frequently used. 
     However, the conventional air discharge technique is commonly implemented by forming electrodes on the substrate, which may generate a leakage problem and decrease the performance of the electrostatic discharge protection device. 
     This “Discussion of the Background” section is provided for background information only. The statements in this “Discussion of the Background” are not an admission that the subject matter disclosed in this “Discussion of the Background” section constitutes prior art to the present disclosure, and no part of this “Discussion of the Background” section may be used as an admission that any part of this application, including this “Discussion of the Background” section, constitutes prior art to the present disclosure. 
     SUMMARY 
     One aspect of the present disclosure provides an over-voltage is protection device utilizing an air discharge technique and method for preparing the same. 
     An over-voltage protection device, according to this aspect of the present disclosure, comprises a substrate; an insulation layer disposed over the substrate, wherein the insulation layer has a depression over the substrate; and a conductor layer disposed over the insulation layer, wherein the conductor layer has a first electrode and a second electrode over the insulation layer, the first electrode and the second electrode form a discharge path, and the depression is under the discharge path. 
     An over-voltage protection device, according to another aspect of the present disclosure, comprises an insulation substrate having a depression and a conductor layer disposed over the insulation substrate, wherein the conductor layer has a first electrode and a second electrode over the insulation layer, the first electrode and the second electrode form a discharge path, and the depression is under the discharge path. 
     A method for preparing an over-voltage protection device, according to this aspect of the present disclosure, comprises steps of forming an insulation layer over a substrate; forming a depression in the insulation layer; forming a photoresist pattern filling the depression and protruding the insulation layer; forming a conductor layer over the insulation substrate, wherein the photoresist pattern separates the conductor layer to form a first electrode and a second electrode; and removing the photoresist pattern to form a discharge path between the first electrode and the second electrode with the depression being under the discharge path. 
     A method for preparing an over-voltage protection device, according to another aspect of the present disclosure, comprises steps of forming a depression in an insulation substrate; forming a photoresist pattern filling the depression and protruding the insulation layer; forming a conductor layer over the insulation substrate, wherein the photoresist pattern separates the conductor layer to form a first electrode and a second electrode; and removing the photoresist pattern to form a discharge path between the first electrode and the second electrode with the depression being under the discharge path. 
     The foregoing has outlined rather broadly the features and technical advantages of the present disclosure in order that the detailed description of the disclosure that follows may be better understood. Additional features and advantages of the disclosure will be described hereinafter, which form the subject of the claims of the disclosure. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures or processes for carrying out the same purposes of the present disclosure. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the disclosure as set forth in the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete understanding of the present disclosure may be derived by referring to the detailed description and claims when considered in connection with the Figures, where like reference numbers refer to similar elements throughout the Figures, and: 
         FIG. 1  is a cross-sectional view illustrating an over-voltage protection device according to one embodiment of the present invention; 
         FIG. 2  to  FIG. 10  are schematic views illustrating a method for preparing the over-voltage protection device shown in  FIG. 1  according to one embodiment of the present invention; 
         FIG. 11  is a cross-sectional view illustrating an over-voltage protection device according to another embodiment of the present invention; and 
         FIG. 12  to  FIG. 19  are schematic views illustrating a method for preparing the over-voltage protection device shown in  FIG. 11  according to one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The following description of the disclosure accompanies drawings, which are incorporated in and constitute a part of this specification, and illustrate embodiments of the disclosure, but the disclosure is not limited to the embodiments. In addition, the following embodiments can be properly integrated to complete another embodiment. 
     References to “one embodiment,” “an embodiment,” “exemplary embodiment,” “other embodiments,” “another embodiment,” etc. indicate that the embodiment(s) of the disclosure so described may include a particular feature, structure, or characteristic, but not every embodiment necessarily includes the particular feature, structure, or characteristic. Further, repeated use of the phrase “in the embodiment” does not necessarily refer to the same embodiment, although it may. 
     The present disclosure is directed to an over-voltage protection device utilizing an air discharge technique and method for preparing the same. In order to make the present disclosure completely comprehensible, detailed steps and structures are provided in the following description. Obviously, implementation of the present disclosure does not limit special details known by persons skilled in the art. In addition, known structures and steps are not described in detail, so as not to limit the present disclosure unnecessarily. Preferred embodiments of the present disclosure will be described below in detail. However, in addition to the detailed description, the present disclosure may also be widely implemented in other embodiments. The scope of the present disclosure is not limited to the detailed description, and is defined by the claims. 
       FIG. 1  is a cross-sectional view illustrating an over-voltage protection device  10  according to one embodiment of the present invention. In one embodiment of the present invention, the over-voltage protection device  10  comprises a substrate  11 , an insulation layer  13  disposed over the substrate  11 , a conductor layer  15  disposed over the insulation layer  13 , a gasket layer  17  disposed over the conductor layer  15 , and a protection layer  19  disposed over the gasket layer  17 . In the embodiment, the insulation layer  13  has a depression  13 A; the conductor layer  15  has a first electrode  15 A and a second electrode  15 B, wherein the first electrode  15 A and the second electrode  15 B form a discharge path  15 C, and the depression  13 A is under the discharge path  15 C, the gasket layer  17  has an opening  17 A exposing at least a portion of the first electrode  15 A and the second electrode  15 B, and the protection layer  19  shields the opening  17 A. 
     In the embodiment, a cross-sectional width of the opening  17 A is larger than a cross-sectional width of the depression  13 A; the first electrode  15 A has a first tip, the second electrode  15 B has a second tip facing the first tip, and the first tip and the second tip are disposed over the depression  13 A. Consequently, when a high voltage is applied to the first tip and the second tip, an air discharge, similar to an arc discharge, occurs between the first tip and the second tip, wherein electrode pieces may be generated from the first tip and the second tip by the air discharge. The depression  13 A can receive the electrode pieces generated during the air discharge so as to avoid the accumulation of the electrode pieces, which may cause a short circuit between the first tip and the second tip. As a result, the performance of the over-voltage protection device  10  can be ensured. 
     In one embodiment of the present disclosure, the substrate  11  comprises aluminum oxide or ceramic, the insulation layer  13  comprises polyimide, the conductor layer  15  comprises copper, the gasket layer  17  comprises epoxy resin or polyimide, and the protection layer  19  comprises epoxy resin or polyimide. In one embodiment of the present disclosure, the over-voltage protection device  10  is equipped with the protection layer  19  to isolate the conductor layer  15  from the external environment so as to prevent an external material from falling into the space between the first tip and the second tip, which may cause a short circuit between the first tip and the second tip. In one embodiment of the present disclosure, the gasket layer  17  separates the protection layer  19  from the conductor layer  15 ; in addition, the opening  17 A provides additional space, which allows the first tip and the second tip to conduct the air discharge through the additional space. 
       FIG. 2  to  FIG. 10  are schematic views illustrating a method for preparing the over-voltage protection device  10  shown in  FIG. 1  according to one embodiment of the present invention. In one embodiment of the present disclosure, referring to  FIG. 2 , an insulation layer  13  comprising photosensitive polyimide is formed over a substrate  11  comprising aluminum oxide or ceramic. An exposure process is then performed on a predetermined portion  13 B of the insulation layer  13 , and the predetermined portion  13 B is removed by a developing process to form a depression  13 A in the insulation layer  13 , as shown in  FIG. 3 . 
     Referring to  FIG. 4 , a sputtering process is performed to form a seeding layer  14 , comprising tungsten-titanium alloy, copper, or nickel-chromium alloy, on the insulation layer  13  and the substrate  11 . A photoresist layer  16  is then coated on the seeding layer  14 , and an exposure process is then performed on a predetermined portion  16 A of the photoresist layer  16 . Subsequently, a developing process is performed to remove the predetermined portion  16 A so as to form a photoresist pattern  16 B, which fills the depression  13 A and protrudes the insulation layer  13 , as shown in  FIG. 5 . In one embodiment of the present disclosure, the photoresist pattern  16 B has a tapered profile. 
     Referring to  FIG. 6 , an electroplating process is performed to form a conductor layer  15  on the insulation layer  13 , and the photoresist pattern  16 B separates the conductor layer  15  to form a first electrode  15 A and a second electrode  15 B. The photoresist pattern  16 B is then removed to form a discharge path between the first electrode  15 A and the second electrode  15 B, and the depression  13 A is under the discharge path, as shown in  FIG. 7 . In  FIG. 6  and  FIG. 7 , the seeding layer  14  is incorporated into the conductor layer  15 , and not shown in the drawings. In one embodiment of the present disclosure, because the photoresist pattern  16 B has the tapered profile, the first electrode  15 A has a first tip, the second electrode  15 B has a second tip, and the first tip and the second tip are disposed over the depression  13 A. 
     Referring to  FIG. 8 , a photoresist layer  18  is coated on the conductor layer  15 , an exposure process is performed on a predetermined portion  18 A of the photoresist layer  18 , and a developing process is then performed to remove the predetermined portion  18 A so as to form a photoresist pattern  18 B. Subsequently, the photoresist pattern  18 B is used to form a gasket layer  17  on the conductor layer  15 , as shown in  FIG. 9 . In one embodiment of the present invention, the gasket layer  17  is a conductor layer or an insulation layer, which can be prepared by fabrication processes for preparing the conductor layer  15 . 
     Referring to  FIG. 10 , the photoresist pattern  18 B is removed to form an opening  17 A in the gasket layer  17 , which exposes at least a portion of the first electrode  15 A and the second electrode  15 B, and a cross-sectional width of the opening  17 A is larger than a cross-sectional width of the depression  13 A. Subsequently, a protection layer  19  comprising a dry polyimide film is adhered to the gasket layer  17 , and the protection layer  19  shields the opening  17 A. 
       FIG. 11  is a cross-sectional view illustrating an over-voltage protection device  60  according to another embodiment of the present invention. In one embodiment of the present invention, the over-voltage protection device  60  comprises an insulation substrate  61  having a depression  61 A, a conductor layer  65  disposed over the insulation substrate  61 , a gasket layer  67  disposed over the conductor layer  65 , and a protection layer  69  disposed over the gasket layer  67 . In the embodiment, the conductor layer  65  has a first electrode  65 A and a second electrode  65 B, wherein the first electrode  65 A and the second electrode  65 B form a discharge path  65 C, and the depression  61 A is under the discharge path  65 C; the gasket layer  67  has an opening  67 A exposing at least a portion of the first electrode  65 A and the second electrode  65 B; and the protection layer  69  shields the opening  67 A. In one embodiment of the present disclosure, the insulation substrate  61  comprises aluminum oxide or ceramic, the conductor layer  65  comprises copper, the gasket layer  67  comprises epoxy resin or polyimide, and the protection layer  69  comprises epoxy resin or polyimide. 
     In the embodiment, a cross-sectional width of the opening  67 A is larger than a cross-sectional width of the depression  61 A; the first electrode  65 A has a first tip, the second electrode  65 B has a second tip facing the first tip, and the first tip and the second tip are disposed over the depression  61 A. Consequently, when a high voltage is applied to the first tip and the second tip, an air discharge, similar to an arc discharge, occurs between the first tip and the second tip, wherein electrode pieces may be generated from the first tip and the second tip by the air discharge. The depression  61 A can receive the electrode pieces generated during the air discharge so as to avoid the accumulation of the electrode pieces, which may cause a short circuit between the first tip and the second tip. As a result, the performance of the over-voltage protection device  60  can be ensured. 
     In one embodiment of the present disclosure, the over-voltage protection device  60  is equipped with the protection layer  69  to isolate the conductor layer  65  from the external environment so as to prevent an external material from falling into the space between the first tip and the second tip, which may cause a short circuit between the first tip and the second tip. In one embodiment of the present disclosure, the gasket layer  67  separates the protection layer  69  from the conductor layer  65 ; in addition, the opening  67 A provides additional space, which allows the first tip and the second tip to conduct the air discharge through the additional space. 
       FIG. 12  to  FIG. 19  are schematic views illustrating a method for preparing the over-voltage protection device  60  shown in  FIG. 11  according to one embodiment of the present invention. In one embodiment of the present disclosure, referring to  FIG. 12 , a depression  61 A is formed in an insulation substrate  61  comprising aluminum oxide or ceramic, and the depression  61 A can be formed by irradiating an infra-red laser or ultra-violet laser on the insulation substrate  61 . 
     Referring to  FIG. 13 , a sputtering process is performed to form a seeding layer  64 , comprising tungsten-titanium alloy, copper, or nickel-chromium alloy, on the insulation substrate  61 . A photoresist layer  66  is then coated on the seeding layer  64 , and an exposure process is then performed on a predetermined portion  66 A of the photoresist layer  66 . Subsequently, a developing process is performed to remove the predetermined portion  66 A so as to form a photoresist pattern  66 B, which fills the depression  61 A and protrudes the insulation substrate  61 , as shown in  FIG. 14 . In one embodiment of the present disclosure, the photoresist pattern  66 B has a tapered profile. 
     Referring to  FIG. 15 , an electroplating process is performed to form a conductor layer  65  on the insulation substrate  61 , and the photoresist pattern  66 B separates the conductor layer  65  to form a first electrode  65 A and a second electrode  65 B. The photoresist pattern  66 B is then removed to form a discharge path between the first electrode  65 A and the second electrode  65 B, and the depression  61 A is under the discharge path, as shown in  FIG. 16 . In  FIG. 15  and  FIG. 16 , the seeding layer  64  is incorporated into the conductor layer  65 , and not shown in the drawings. In one embodiment of the present disclosure, because the photoresist pattern  66 B has the tapered profile, the first electrode  65 A has a first tip, the second electrode  65 B has a second tip, and the first tip and the second tip are disposed over the depression  61 A. 
     Referring to  FIG. 17 , a photoresist layer  68  is coated on the conductor layer  65 , an exposure process is performed on a predetermined portion  68 A of the photoresist layer  68 , and a developing process is then performed to remove the predetermined portion  68 A so as to form a photoresist pattern  68 B. Subsequently, the photoresist pattern  68 B is used to form a gasket layer  67  on the conductor layer  65 , as shown in  FIG. 18 . In one embodiment of the present invention, the gasket layer  67  is a conductor layer or an insulation layer, which can be prepared by fabrication processes for preparing the conductor layer  65 . 
     Referring to  FIG. 19 , the photoresist pattern  68 B is removed to form an opening  67 A in the gasket layer  67 , which exposes at least a portion of the first electrode  65 A and the second electrode  65 B, and a cross-sectional width of the opening  67 A is larger than a cross-sectional width of the depression  61 A. Subsequently, a protection layer  69  comprising a dry polyimide film is adhered to the gasket layer  67 , and the protection layer  69  shields the opening  67 A. 
     Although the present disclosure and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the disclosure as defined by the appended claims. For example, many of the processes discussed above can be implemented in different methodologies and replaced by other processes, or a combination thereof. 
     Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present disclosure, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed, that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present disclosure. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.