Abstract:
A fingerprint identification apparatus includes a fingerprint identification IC chip having a contact face and a plurality of metal bumps arranged on the contact face, a thin substrate having a first face, a second face opposite to the first face and a plurality of metal pads arranged on the first face, wherein at least part of the metal pads electrically connect with the metal bumps, a protection layer having a mounting face adjacent to the second face of the thin substrate, and a plurality of conductive electrodes arranged between the thin substrate and the protection layer. The metal bumps are not directly pressed or press-soldered to the protection layer, thus preventing the transparent conductive traces of the protection layer from damaging and enhancing the package yield.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    Field of the Invention 
         [0002]    The present invention relates to a fingerprint identification apparatus, especially to a fingerprint identification apparatus having low cost and high packaging yield. 
         [0003]    Description of Prior Art 
         [0004]    Biometric recognition technologies have rapid development due to the strong request from electronic security applications and automatic access control system. The biometric recognition technologies can be classified into fingerprint recognition, iris recognition and DNA recognition and so on. For the considerations of efficiency, safety and non-invasiveness, the fingerprint recognition becomes main stream technology. The fingerprint recognition device can scan fingerprint image by optical scanning, thermal imaging or capacitive imaging. For cost, power-saving, reliability and security concerns, the capacitive fingerprint sensor becomes popular for biometric recognition technology applied to portable electronic devices. 
         [0005]    The conventional capacitive fingerprint sensors can be classified into swipe type and area type (pressing type), and the area type has better identification correctness, efficiency and convenience. However, the area type capacitive fingerprint sensor generally integrates the sensing electrodes and the sensing circuit into one integrated circuit (IC) because the sensed signals are minute and the background noise is huge in comparison with the minute sensed signals. In conventional area type technique, holes are defined on the protection glass of the display to arrange the fingerprint identification IC chip therein and sapphire film is used to cover and protect the fingerprint identification IC chip. Through-silicon via (TSV) technique is used to lead the conductive wires to backside of the fingerprint identification IC chip. As a result, the material cost and package cost is high while the yield is influenced. There are development trends to simply the package the fingerprint identification IC chip and to enhance the sensing ability. The fingerprint identification IC chip is desirably packaged under the protection glass to reduce cost and enhance product lifetime/durability. 
       SUMMARY OF THE INVENTION 
       [0006]    It is an object of the present invention to provide a fingerprint identification apparatus having low cost and high packaging yield. 
         [0007]    Accordingly, the present invention provides a fingerprint identification apparatus comprising: 
         [0008]    a fingerprint identification IC chip having a contact face and a plurality of metal bumps arranged on the contact face; a thin substrate having a first face, a second face opposite to the first face and a plurality of metal pads arranged on the first face, wherein at least part of the metal pads electrically connect with the metal bumps; a protection layer having a mounting face adjacent to the second face of the thin substrate, and a plurality of conductive electrodes arranged between the thin substrate and the protection layer. 
         [0009]    In one aspect of the present invention, the fingerprint identification apparatus in further comprises a flexible circuit board electrically connected to the thin substrate. 
         [0010]    In another aspect of the present invention, the at least part of the metal pads on the thin substrate and the metal bumps of the fingerprint identification IC chip are in one by one correspondence. 
         [0011]    In still another aspect of the present invention, the conductive electrodes are arranged on the mounting face of the protection layer, and the at least part of the metal pads on the thin substrate and the conductive electrodes on the protection layer are in one by one correspondence. 
         [0012]    In still another aspect of the present invention, the thin substrate is glued to the protection layer. 
         [0013]    In still another aspect of the present invention, the fingerprint identification IC chip is pressed on the thin substrate through anisotropic conductive film (ACF), or the fingerprint identification IC chip is pressure soldered on the thin substrate through a low melting point metal material. 
         [0014]    In still another aspect of the present invention, the protection layer is a protection glass of a display or a thin film transistor substrate for a display. 
         [0015]    In still another aspect of the present invention, the protection layer is made from glass, ceramic, sapphire or polymer material. 
         [0016]    In still another aspect of the present invention, the thin substrate is polymer firm substrate. 
         [0017]    In still another aspect of the present invention, the fingerprint identification IC chip further comprises a fingerprint identification circuit and the fingerprint identification circuit comprises at least one self-capacitance sensing circuit. 
         [0018]    In still another aspect of the present invention, the thin substrate has thickness between 10 to 100 micrometers. 
         [0019]    Accordingly, the present invention provides a fingerprint identification apparatus comprising: 
         [0020]    a fingerprint identification IC chip having a contact face and a plurality of metal bumps arranged on the contact face; an intermediate layer having a first face, a second face opposite to the first face and a plurality of metal pads arranged on the first face and the second face respectively, the metal pads on the first face and the metal pads on the second face being one by one correspondence and electrically connected by corresponding metal pillars, wherein at least part of the metal pads on the first face of the intermediate layer electrically connected to the metal bumps; and a protection layer having a mounting face adjacent to the second face of the intermediate layer. 
         [0021]    In one aspect of the present invention, the fingerprint identification apparatus in further comprises a flexible circuit board electrically connected to the thin substrate. 
         [0022]    In another aspect of the present invention, the at least part of the metal pads on the first face of the intermediate layer and the metal bumps of the fingerprint identification IC chip are in one by one correspondence. 
         [0023]    In still another aspect of the present invention, the protection layer has a plurality of conductive electrodes on the mounting face, at least part of the metal pads on the second face of the intermediate layer and the conductive electrodes are in one by one correspondence. 
         [0024]    In still another aspect of the present invention, the fingerprint identification IC chip is pressed on the intermediate layer through anisotropic conductive film (ACF), or the fingerprint identification IC chip is pressure soldered on the intermediate layer through a low melting point metal material. 
         [0025]    In still another aspect of the present invention, the protection layer is a protection glass of a display. 
         [0026]    In still another aspect of the present invention, the protection layer is made from glass, ceramic, sapphire or polymer material. 
         [0027]    In still another aspect of the present invention, the fingerprint identification IC chip further comprises a fingerprint identification circuit and the fingerprint identification circuit comprises at least one self-capacitance sensing circuit. 
         [0028]    By above-mentioned fingerprint identification apparatus, the fingerprint identification IC chip is assembled with the protection through a thin substrate or an intermediate layer, whereby the cost of the fingerprint identification apparatus is reduced and the yield of the fingerprint identification apparatus is enhanced. 
     
    
     
       BRIEF DESCRIPTION OF DRAWING 
         [0029]    One or more embodiments of the present disclosure are illustrated by way of example and not limitation in the figures of the accompanying drawings, in which like references indicate similar elements. These drawings are not necessarily drawn to scale. 
           [0030]      FIG. 1  is a schematic diagram showing the fingerprint identification apparatus according to the first embodiment of the present invention. 
           [0031]      FIG. 2  shows is a schematic diagram showing the fingerprint identification apparatus according to the second embodiment of the present invention. 
           [0032]      FIG. 3  shows the circuit diagram of the self-capacitance sensing circuit according to an embodiment of the present invention. 
           [0033]      FIG. 4  is a schematic diagram showing the fingerprint identification apparatus according to the third embodiment of the present invention. 
           [0034]      FIG. 5  is a schematic diagram showing the fingerprint identification apparatus according to the fourth embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0035]      FIG. 1  is a schematic diagram showing the fingerprint identification apparatus  10  according to the first embodiment of the present invention. The fingerprint identification apparatus  10  of the present invention is applied to bio-identifying technology. The fingerprint identification apparatus  10  comprises a fingerprint identification IC chip  100 , a thin substrate  200 , a protection layer  300  and a plurality of conductive electrodes  700 . The fingerprint identification IC chip  100  comprises a contact face  100   a , a plurality of metal bumps  102 , a fingerprint identification circuit  104  and a self-capacitance sensing circuit  106 , where the metal bumps  102  are arranged on the contact face  100   a  of the fingerprint identification IC chip  100 . The thin substrate  200  comprises a first face  200   a , a second face  200   b  opposite to the first face  200   a , and a plurality of metal pads  202 , where the metal pads  202  are arranged on the first face  200   a . The protection layer  300  comprises a mounting face  300   a , and an operative face  300   b  opposite to the mounting face  300   a , where the mounting face  300   a  of the protection layer  300  is adjacent to the second face  200   b  of the thin substrate  200 . The conductive electrodes  700  are arranged between the thin substrate  200  and the protection layer  300 . As shown in  FIG. 1 , the user finger is operated on the operative face  300   b  of the protection layer  300 . 
         [0036]    At least part of the metal pads  202  on the first face  200   a  of the thin substrate  200  are electrically connected to the metal bumps  102  of the fingerprint identification IC chip  100 . For example, the fingerprint identification IC chip  100  may be arranged on the thin substrate  200  through anisotropic conductive film (ACF) to achieve above electrical connection. Besides, the fingerprint identification IC chip  100  may be soldered on the thin substrate  200  through pressure soldering of a low melting point metal material to achieve electrical connection between part of the metal pads  202  and the corresponding metal bumps  102 . Moreover, the metal bumps  102  and part of the metal pads  202  are in one by one correspondence (one by one relationship) with respect to their locations. Another part of the metal pads  202  can be electrically connected to metal pads  402  on a flexible circuit board  400  such that the fingerprint identification signal generated by the fingerprint identification IC chip  100  can be sent to the flexible circuit board  400  through the thin substrate  200  for further processing. As shown in  FIG. 1 , the metal pads  402  of the flexible circuit board  400  can be electrically connected to the fingerprint identification IC chip  100  through the metal pad  202  and the conductive trace  206  of the thin substrate  200 . The fingerprint identification IC chip  100  further comprises a fingerprint identification circuit  104 , which comprises a self-capacitance sensing circuit  106 . The detail of the self-capacitance sensing circuit  106  can be referred to U.S. Pat. No. 8,704,539 (corresponding to Taiwan patent No. 1473001) filed by the same applicant. Part of the description for the self-capacitance sensing circuit  106  will also be made later with reference to  FIG. 3 . The thin substrate  200  is ultra-thin substrate with thickness between 10 to 100 micrometers and can be, for example, a polymer thin film substrate. 
         [0037]    The protection layer  300  is faced down and attached to (for example, glued by optical glue) a surface of the thin substrate  200 , namely, the mounting face  300   a  of the protection layer  300  is attached to the second face  200   b  of the thin substrate  200  such that the signal transmission between the protection layer  300  and the fingerprint identification IC chip  100  can be made through the thin substrate  200 . More particularly, the conductive electrodes  700  and above-mentioned part of the metal pads  202  (those having electrical connection with the metal bumps  102 ) are in one by one correspondence with respect to their locations. In this embodiment, the conductive electrodes  700  may be arranged on the mounting face  300   a  of the protection layer  300  or on the second face  200   b  of the thin substrate  200 . When the user finger is pressed on (or in proximity to) the operative face  300   b  of the protection layer  300 , a first capacitor C 1  is formed between a contact point of user finger and the corresponding conductive electrode  700 ; while a second capacitor C 2  is formed between the corresponding conductive electrode  700  and the metal pad  202  related to the corresponding conductive electrode  700  as shown in  FIG. 1 . The thickness of the thin substrate  200  is far less than the thickness of the protection layer  300  such that the capacitance of the second capacitor C 2  is far larger than the capacitance of the first capacitor Cl. Therefore, the capacitance of the serially connected first capacitor C 1  and second capacitor C 2  is almost the same as the capacitance of the first capacitor C 1  alone. The insertion of the thin substrate  200  between the protection layer  300  and the fingerprint identification IC chip  100  will not influence the precision of fingerprint identification. In the present invention, the metal bumps  102  of the fingerprint identification IC chip  100  are attached to the thin substrate  200  through anisotropic conductive film (ACF), or soldered on the thin substrate  200  through pressure soldering of a low melting point metal material. Afterward, the thin substrate  200  is attached to the protection layer  300 . Namely, the fingerprint identification IC chip  100  is not directly attached to or soldered to the protection layer  300 . When the protection layer  300  is a protection glass of a display, the arrangement of the fingerprint identification IC chip  100  will not damage the transparent wiring (such as ITO) on the mounting face  300   a  of the protection layer  300 . Besides being the protection glass of a display, the protection layer  300  may be thin film transistor substrate. In other embodiments, the protection layer  300  may be anti-scratch film or membrane (such as film or membrane made from glass, ceramic, sapphire or polymer material) with size larger enough to cover the fingerprint identification IC chip  100 . 
         [0038]      FIG. 2  shows is a schematic diagram showing the fingerprint identification apparatus  10  according to the second embodiment of the present invention. The embodiment shown in  FIG. 2  is similar to that shown in  FIG. 1  except that the thin substrate  200  of the fingerprint identification apparatus  10  further comprises a plurality of metal pads  204 . At this time, the conductive electrodes  302  are arranged on the protection layer  300 . More particularly, the metal pads  204  are arranged on the second face  200   b  of the thin substrate  200  while the conductive electrodes  302  are arranged on the mounting face  300   a  of the protection layer  300 . The metal pads  204  and the conductive electrodes  302  are in one by one correspondence with respect to their locations. Moreover, the metal pads  204  also have one by one correspondence with part of the metal pads  202  with respect to their locations and have one by one correspondence with part of the metal bumps  102  with respect to their locations. Namely, the mounting face  300   a  is attached to the metal pads  204  on second face  200   b  of the thin substrate  200 . Similarly, the embodiment in  FIG. 2  also has the advantages of simple package to arrange the fingerprint identification IC chip  100  below the protection layer  300 . In other embodiments, the conductive electrodes  302  may be dispensed with, and the protection layer  300  can be alternatively formed on the second face  200   b  of the thin substrate  200  by coating or deposition (such as physical deposition). 
         [0039]      FIG. 3  shows the circuit diagram of the self-capacitance sensing circuit according to an embodiment of the present invention. The self-capacitance sensing circuit  160  mainly comprises a differential amplifier  500 , a first impedance  502 , a second impedance  504 , a first capacitor  506 , a sensing electrode  508 , an input signal source  510 , a first stray capacitance  514 , a second stray capacitance  516  and a third impedance  518 . The differential amplifier  500  has a first input end  600 , a second input end  602  and an output end  604 . 
         [0040]    The input signal source  510  is electrically coupled with the third impedance  518 . The third impedance  518  is electrically coupled with the first impedance  502  and the second impedance  504 . The first impedance  502  is electrically coupled with the first capacitor  506  and the first capacitor  506  is electrically coupled with the first input end  600  of the differential amplifier  500 . The second impedance  504  is electrically coupled with the second input end  602  of the differential amplifier  500 . The sensing electrode  508  is electrically coupled to the second impedance  504  and the second input end  602  through an IC pin  512  of the self-capacitance sensing circuit  160 . The first stray capacitance  514  is electrically coupled to the IC pin  512  and the second stray capacitance  516  is electrically coupled to the sensing electrode  508 . In the self-capacitance sensing circuit  160  shown in  FIG. 3 , the sensing electrode  508  receives a touch signal when a finger or a conductor is touched thereon. The input signal source  510  is a periodical signal and sent to the first impedance  502  and the second impedance  504  through the third impedance  518 . Due to the equivalence of the resistance values for the first impedance  502  and the second impedance  504 , the differential amplifier  500  will generate a differential touch signal after receiving the input signal source  510  and the touch signal from the sensing electrode  508 . In this embodiment, the capacitance of the first capacitor  506  is equal to the resulting capacitance of the first stray capacitance  514  in parallel connection with the second stray capacitance  516 . The capacitance of the second stray capacitance  516  changes when user finger approaches or touches the sensing electrode  508 . Therefore, the voltages fed to the first input end  600  and the second input end  602  will be different such that the differential amplifier  500  has a (non-zero) differential output at the output end  604 . In this way, the minute capacitance change on the sensing electrode  508  can be detected by the differential amplifier  500 . Moreover, the noise from circuits or power source can be advantageously removed. 
         [0041]      FIG. 4  is a schematic diagram showing the fingerprint identification apparatus  10  according to the third embodiment of the present invention. The fingerprint identification apparatus  10  of the present invention is applied to bio-identifying technology. The fingerprint identification apparatus  10  comprises a fingerprint identification IC chip  100 , an intermediate layer  220  and a protection layer  300 . The fingerprint identification IC chip  100  comprises a contact face  100   a , a plurality of metal bumps  102 , a fingerprint identification circuit  104  and a self-capacitance sensing circuit  106 , where the metal bumps  102  are arranged on the contact face  100   a  of the fingerprint identification IC chip  100 . 
         [0042]    The intermediate layer  220  comprises a first face  220   a , a second face  220   b  opposite to the first face  220   a , a plurality of metal pillars  221  arranged between the first face  220   a  and the second face  220   b , and a plurality of metal pads  222  and  224 . The metal pads  222  are arranged on the first face  220   a  of the intermediate layer  220  and part of the metal pads  222  have one by one correspondence with the metal pillars  221 . The metal pads  224  are arranged on the second face  220   b  of the intermediate layer  220  and have one by one correspondence with the metal pillars  221 . The protection layer  300  comprises a mounting face  300   a  and an operative face  300   b  opposite to the mounting face  300   a . As shown in  FIG. 4 , the user finger is operated on the operative face  300   b  of the protection layer  300 . 
         [0043]    As shown in  FIG. 4 , part of the metal pads  222  on the first face  220   a  of the intermediate layer  220  are electrically connected to the metal bumps  102  of the fingerprint identification IC chip  100 . For example, the fingerprint identification IC chip  100  may be arranged on the intermediate layer  220  through anisotropic conductive film (ACF) to achieve above electrical connection. Besides, the fingerprint identification IC chip  100  may be soldered on the intermediate layer  220  through pressure soldering of a low melting point metal material to achieve electrical connection between part of the metal pads  222  and the corresponding metal bumps  102 . Moreover, the metal bumps  102  and part of the metal pads  222  on the first face  220   a  of the intermediate layer  220  are in one by one correspondence (one by one relationship) with respect to their locations. Another part of the metal pads  222  on the first face  220   a  of the intermediate layer  220  can be electrically connected to metal pads  402  on a flexible circuit board  400  such that the fingerprint identification signal generated by the fingerprint identification IC chip  100  can be sent to the flexible circuit board  400  through the intermediate layer  220  for further processing. As shown in  FIG. 4 , the metal pads  402  of the flexible circuit board  400  can be electrically connected to the fingerprint identification IC chip  100  through the metal pad  222  and the conductive trace  226  of the intermediate layer  220 . The fingerprint identification IC chip  100  further comprises a fingerprint identification circuit  104 , which comprises a self-capacitance sensing circuit  106 . The detail of the self-capacitance sensing circuit  106  can be referred to U.S. Pat. No. 8,704,539 (corresponding to Taiwan patent No. 1473001) filed by the same applicant. Part of the description for the self-capacitance sensing circuit  106  will also be made later with reference to  FIG. 3 . 
         [0044]    The protection layer  300  is faced down and attached to (for example, glued by optical glue) the second face  220   b  of the intermediate layer  220  or the protection layer  300  is formed on the second face  220   b  of the intermediate layer  220  by deposition or coating. Namely, the mounting face  300   a  of the protection layer  300  is attached to the second face  220   b  of the intermediate layer  220  such that the signal transmission between the protection layer  300  and the fingerprint identification IC chip  100  can be made through the intermediate layer  220 . When the user finger is pressed on (or in proximity to) the operative face  300   b  of the protection layer  300 , a capacitor C is formed between a contact point of user finger and the corresponding metal pad  224  on the second face  220   b  of the intermediate layer  220 . The metal pad  224  and the corresponding metal pad  222  on opposite faces of the intermediate layer have direct signal connection due to the metal pillar  221 . Therefore, the provision the intermediate layer  220  will not change the value of the capacitor C and will not influence the precision of fingerprint identification. In the present invention, the metal bumps  102  of the fingerprint identification IC chip  100  are attached to the intermediate layer  220  through anisotropic conductive film (ACF), or soldered on the intermediate layer  220  through pressure soldering. Afterward, the intermediate layer  220  is attached to the protection layer  300 . Namely, the fingerprint identification IC chip  100  is not directly attached to or soldered to the protection layer  300 . When the protection layer  300  is a protection glass of a display, the arrangement of the fingerprint identification IC chip  100  will not damage the transparent electrode (such as ITO) on the mounting face  300   a  of the protection layer  300 . Besides being the protection glass of a display, the protection layer  300  may be thin film transistor substrate. In other embodiments, the protection layer  300  may be anti-scratch film or membrane (such as film or membrane made from glass, ceramic, sapphire or polymer material) with size larger enough to cover the fingerprint identification IC chip  100 . 
         [0045]      FIG. 5  is a schematic diagram showing the fingerprint identification apparatus  10  according to the fourth embodiment of the present invention. The embodiment shown in  FIG. 5  is similar to that shown in  FIG. 4  except that the protection layer  300  further comprises a plurality of conductive electrodes  302 . The conductive electrodes  302  are arranged on the mounting face  300   a  of the protection layer  300  and have one by one correspondence with the metal pads  224  on the second face  220   b  of the intermediate layer  220  (with respect to their locations). When the user finger is pressed on (or in proximity to) the operative face  300   b  of the protection layer  300 , a capacitor C is formed between a contact point of user finger and the corresponding conductive electrode  302  arranged on the mounting face  300   a  of the protection layer  300 . The conductive electrode  302  and the corresponding metal pad  222  on bottom face of the intermediate layer  220  have direct signal connection due to the metal pillar  221 . Therefore, the provision the intermediate layer  220  will not change the value of the capacitor C and will not influence the precision of fingerprint identification. Similarly, the embodiment in  FIG. 5  also has the advantages of simple package to arrange the fingerprint identification IC chip  100  below the protection layer  300 . 
         [0046]    Thus, particular embodiments have been described. Other embodiments are within the scope of the following claims. For example, the actions recited in the claims may be performed in a different order and still achieve desirable results.