Abstract:
A liquid glass application is provided, which uses liquid glass to prepare a substrate having conductive posts, a substrate embedded with a circuit and a glass membrane. The liquid glass possesses a large number of usage convenience features. Therefore, a preparation cost can be greatly reduced. Besides, a traditional glass configuration limit is broken and a glass thickness can be reduced remarkably, thereby meeting nowadays requirements of lightness, thinness, shortness and smallness on electronic products.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to glass applications, and, more particularly, to a liquid glass application. 
         [0003]    2. Description of Related Art 
         [0004]    Along with the progress of semiconductor processing technologies, more and more electronic products have been applied in semiconductor processes. 
         [0005]    However, the conventional semiconductor processes can only use semiconductor materials as dielectric layers and insulating layers. The conventional semiconductor materials are generally required to be formed under a high-vacuum high-temperature environment by using expensive equipments and most of the semiconductor materials have a poor light transmittance. Therefore, the practical application of the semiconductor materials is seriously limited. 
         [0006]    Although glass substrates are later developed to replace semiconductor substrates, forming via holes, recesses or through holes on a glass substrate is quite difficult, not environment friendly (for example, due to the use of highly toxic hydrofluoric acid) and there are many limits on shapes. 
         [0007]    Therefore, how to overcome the above-described drawbacks and effectively use a glass material that eliminates the need of a high temperature process and expensive equipments and has a better light transmittance and a wider application area has become critical. 
       SUMMARY OF THE INVENTION 
       [0008]    In view of the above-described drawbacks, a primary object of the present invention is to provide a liquid glass application so as to greatly reduce a glass thickness and meet nowadays requirements of lightness, thinness, shortness and smallness on electronic products. 
         [0009]    The present invention provides a method for fabricating a substrate, which comprises: forming a plurality of conductive posts on a carrier board; coating a liquid glass layer on the carrier board to encapsulate the conductive posts, wherein a top surface of the liquid glass layer is flush with top ends of the conductive posts; baking at a baking temperature between 50 and 100° C.; irradiating with UV light; and removing the carrier board. 
         [0010]    The present invention provides a substrate, which comprises: a glass base having a thickness of 2 to 25 μm; and a plurality of conductive posts penetrating two surfaces of the glass base. 
         [0011]    The present invention provides a substrate, which comprises: a polyimide base having a thickness of 2 to 100 μm; and a plurality of conductive posts penetrating two surfaces of the polyimide base. 
         [0012]    The present invention provides a method for fabricating a substrate embedded with a circuit, which comprises: forming on a carrier board a redistribution layer (RDL) structure that is comprised of at least a circuit layer and at least a glass layer alternately stacked on each other, the glass layer being formed by sequentially performing the steps of coating a liquid glass layer, baking at a baking temperature between 50 and 100° C., and irradiating with UV light; and removing the carrier board. 
         [0013]    The present invention provides a substrate embedded with a circuit, which comprises: an RDL structure comprised of at least a circuit layer and at least a glass layer alternately stacked on each other, wherein the glass layer has a thickness of 2 to 25 μm. 
         [0014]    The present invention provides a method for fabricating a glass membrane, which comprises: coating a liquid glass layer on a carrier film; baking at a baking temperature between 50 and 100° C.; impressing a concave-convex pattern on a surface of the liquid glass layer and irradiating with UV light; and removing the carrier film. 
         [0015]    The present invention provides a glass membrane, which comprises: a glass board having a regular or irregular concave-convex pattern on a surface thereof, wherein the glass board has a thickness of 2 to 25 μm. 
         [0016]    Therefore, the photosensitive liquid glass application according to the present invention is operated with simple steps at a low temperature under a common atmosphere environment without the need of expensive equipments, and has a good light transmittance. Further, there is almost no limit on shape in formation of photosensitive liquid glass. As such, the cost is greatly reduced and the application area is expanded. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0017]      FIGS. 1A to 1J  are cross-sectional views showing a substrate and a method for fabricating the same according to the present invention. 
           [0018]      FIGS. 2A to 2C  are cross-sectional views showing a substrate embedded with a circuit and a method for fabricating the same according to the present invention. 
           [0019]      FIGS. 3A to 3D  are cross-sectional views showing a substrate embedded with a circuit and a method for fabricating the same according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0020]    The following illustrative embodiments are provided to illustrate the disclosure of the present invention, these and other advantages and effects can be apparent to those in the art after reading this specification. 
         [0021]    It should be noted that the structures, scales, sizes etc. shown in the drawings of the specification are only used in combination with the contents disclosed in the specification so as to be understood and read by those in the art and are not intended to limit the present invention. Any modification to the structures, change in the scales or adjustment of the sizes should still fall within the scope covered by the technical means disclosed by the present invention provided that the functions and objects that can be achieved by the present invention are not affected. In addition, terms such as “on”, “top”, “flush”, “side”, “around”, “concave-convex”, “a” etc. used in the specification are merely for illustrative purposes and not used to limit the scope of implementation of the present invention. Any change or adjustment of the relative relationships is also considered as being within the scope of implementation of the present invention if there is no material change in the technical means. 
       First Embodiment 
       [0022]      FIGS. 1A to 1J  are cross-sectional views showing a substrate and a method for fabricating the same according to the present invention. 
         [0023]    Referring to  FIG. 1A , a metal foil  11  is formed on a carrier board  10 . 
         [0024]    Referring to  FIG. 1B , a first resist layer  12  having a plurality of openings  120  is formed on the metal foil  11 . 
         [0025]    Referring to  FIG. 1C , conductive posts  13  are respectively formed in the openings  120  by electroplating or deposition (for example, sputtering, evaporation, metal paste etc.), and an angle of 85 to 90° is formed between side walls of the conductive posts  13  and the carrier board  10  around the conductive posts  13 . That is, the side walls of the conductive posts  13  have a good verticality. 
         [0026]    Referring to  FIG. 1D , the first resist layer  12  is removed. 
         [0027]    Referring to  FIG. 1E , a liquid glass layer  14  is coated on the metal foil  11  to encapsulate the conductive posts  13 . The liquid glass layer  14  has a thickness of 2 to 25 μm, and a top surface of the liquid glass layer  14  is flush with top ends of the conductive posts  13 . The liquid glass layer  14  is baked at a baking temperature between 50 and 100° C., preferably between 70 and 95° C., and at best at 85° C., and the baking takes 3 to 55 minutes. Then, the liquid glass layer  14  is irradiated with UV light so as to be cured into a glass base  14 ′. 
         [0028]    Referring to  FIG. 1F , a conductive layer  15  is formed on the top surface of the glass base  14 ′ and the top ends of the conductive posts  13 . 
         [0029]    Referring to  FIG. 1G  a second resist layer  16  having a plurality of openings  160  is formed on the conductive layer  15 . 
         [0030]    Referring to  FIG. 1H , a first circuit layer  17  electrically connected to the conductive posts  13  is formed in the openings  160 . 
         [0031]    Referring to FIG. II, the second resist layer  16  and the conductive layer  15  covered by the second resist layer  16  are removed. 
         [0032]    Referring to  FIG. 1J , the carrier board  10  is removed, and the metal foil  11  is patterned into a second circuit layer  11 ′ electrically connected to the conductive posts  13 . 
         [0033]    In an embodiment, the metal foil  11 , the first resist layer  12 , the conductive layer  15  and the second resist layer  16  can be provided according to need, and are not essential components. 
         [0034]    The present invention further provides a substrate, which has: a glass base  14 ′ having a thickness of 2 to 25 μm; and a plurality of conductive posts  13  penetrating two surfaces of the glass base  14 ′. 
         [0035]    In an embodiment, an angle of 85 to 95° is formed between side walls of the conductive posts  13  and the surfaces of the glass base  14 ′. 
         [0036]    In an embodiment, the substrate according to the present embodiment is an interposer and the glass base  14 ′ according to the present embodiment can be replaced with a polyimide base that has a thickness of 2 to 100 μm, preferably 2 to 25 μm. The other features of the polyimide base are identical to the glass base  14 ′, and detailed description thereof is omitted herein. 
       Second Embodiment 
       [0037]      FIGS. 2A to 2C  are cross-sectional views showing a substrate embedded with a circuit and a method for fabricating the same according to the present invention. 
         [0038]    Referring to  FIG. 2A , a carrier board  20  is provided. 
         [0039]    Referring to  FIG. 2B , an RDL structure  21  is formed on the carrier board  20 , and includes at least a circuit layer  211  and at least a glass layer  212  alternately stacked on each other. In an embodiment, the glass layer  212  is formed by sequentially performing the steps of coating a liquid glass layer, baking at a baking temperature between 50 and 100° C., and irradiating with UV light. The baking temperature is preferably between 70 and 95° C. and at best at 85° C., and the baking takes 3 to 55 minutes depending on a thickness of the glass layer  212 . The thickness of the glass layer  212  is in a range of 2 to 25 μm. 
         [0040]    Referring to  FIG. 2C , the carrier board  20  is removed. 
         [0041]    The present invention further provides a substrate embedded with a circuit, which has: an RDL structure  21  consisting of at least a circuit layer  211  and at least a glass layer  212  alternately stacked on each other, wherein the glass layer  212  has a thickness of 2 to 25 μm. 
         [0042]    It an embodiment, the substrate according to the present embodiment can be a core board, and can be directly replaced with a conventional silicon interposer so as to redistribute a circuit directly in the core board. 
       Third Embodiment 
       [0043]      FIGS. 3A to 3D  are cross-sectional views showing a glass membrane and a method for fabricating the same according to the present invention. 
         [0044]    Referring to  FIG. 3A , a liquid glass layer  31  is coated on a carrier film  30  and baked at a baking temperature between 50 and 100° C. The baking temperature is preferably between 70 and 95° C. and at best at 85° C., and the baking takes 3 to 55 minute depending on a thickness of the liquid glass layer  31 . The thickness of the liquid glass layer  31  is in a range of 2 to 25 μm. 
         [0045]    Referring to  FIGS. 3B and 3C , a roller  32  is used to impress an irregular or regular concave-convex pattern  311  on a surface of the liquid glass layer  31 , and the liquid glass layer  31  is irradiated with UV light through the carrier film  30  so as to be cured into a glass board  31 ′. 
         [0046]    Referring to  FIG. 3D , the carrier film  30  is removed. 
         [0047]    The present invention further provides a glass membrane, which has: a glass board  31 ′ having an irregular or regular concave-convex pattern  311  on a surface thereof, wherein the glass board  31 ′ has a thickness of 2 to 25 μm. 
         [0048]    It an embodiment, a release layer can be formed on the carrier film before coating of the liquid glass layer so as to facilitate the final removal of the carrier film, and the glass membrane according to the present embodiment can be applied in screen protection, screen anti-glare, and light condensing or dispersing for light sources of displays. 
         [0049]    Therefore, compared with the prior art, since the photosensitive liquid glass application according to the present invention is operated with simple steps at a low temperature under a common atmosphere environment without the need of expensive equipments, and has a good light transmittance, the cost is effectively saved. In addition, the photosensitive liquid glass can be formed conveniently and there is almost no limit on shape. As such, through holes with a good verticality and a very thin thickness can be achieved and the application area is expanded. 
         [0050]    The description of the above embodiments is only to illustrate the principle and effect of the present invention, but is not intended to limit the present invention. Any person skilled in the art can make modification or variation to the above embodiments without departing from the sprit and scope of the present invention. Therefore, the scope of the present invention is set forth in the appended claims.