TW201416991A - Capacitive fingerprint sensor and method of manufacturing the same - Google Patents

Abstract

The invention provides a capacitive fingerprint sensor and a method of manufacturing the same. The fingerprint sensor includes an insulation substrate, a sensing and front-end processing unit and a back-end processing unit. The sensing and front-end processing unit, formed on a front side of the insulation substrate, performs sensing and front-end signal processing on a fingerprint of a finger and generates analog fingerprint sensing signals. The back-end processing unit, disposed on the front side of the insulation substrate, is disposed on the insulation substrate and electrically connected to the sensing and front-end processing unit through an anisotropic conductive film, and receives and processes each of the analog fingerprint sensing signals into a resultant signal for output.

Description

Capacitive fingerprint sensor and manufacturing method thereof

The invention relates to a capacitive fingerprint sensor and a manufacturing method thereof, and in particular to a capacitive fingerprint sensor with low cost and external shock resistance and a manufacturing method thereof.

Compared with the traditional optical identification optical machine, the capacitive fingerprint identification chip has the functions of small volume and living body identification function, and is not easily deceived by fake fingers. Therefore, its application has only been removed from the identification system of large government agencies. In the past ten years, the application of fingerprint identification has been slowly growing in the electronic consumer market. Electronic devices including flash drives, portable hard disk cases, notebook computers, and mobile phones have fingerprint identification chips installed to increase consumer data. Security.

Whether it is an optical or capacitive fingerprint chip, it is necessary to sense the fingerprint of the finger of the test subject. The larger the area of contact between the finger and the wafer, the more complete the information is sensed, the more accurate the recognition rate will be, and the false positive rate will be greatly reduced. Capacitive fingerprint wafers are usually completed in a semiconductor process. The size of the wafer determines the number of wafers produced per wafer and the price of the unit wafer. However, since the capacitive fingerprint chip requires a minimum equivalent of the area of the adult finger fingerprint thread area (about 0.8 ^* 0.8 mm ² ) to fully sense the finger fingerprint pattern, the price of the press-type fingerprint recognition chip has been high, and the application is Extensiveness has been limited. Therefore, a large-area fingerprint sensing system usually uses an optical illuminator to read a fingerprint image.

Many fingerprint chip manufacturers are designing towards sliding fingerprint chips in response to the problem of over-the-counter fingerprint identification of wafers. It designs the area of the fingerprint wafer to be approximately the size of the human finger width, about 192 to 256 pixels, but the length is shortened to only 2 to 8 pixels, and the area of each pixel is about 50 ^* 50um ² . When using a sliding wafer to sense fingerprint information, a human finger must be slid in parallel to the wafer. The fingerprint chip continuously reads the frame information when the human finger slides over the surface of the wafer, and connects each segment into a complete fingerprint image. This method can achieve the function of the area type fingerprint recognition chip, and can be greatly By reducing wafer costs, sliding fingerprint chips are now mainstream in consumer electronics.

Because the image capture accuracy of the sliding fingerprint chip has a great relationship with the user's sliding behavior, the sliding speed is too fast, the finger can not flatten the surface of the wafer or may slide obliquely, which may cause fingerprint image reading. If the error is taken or the clip file cannot be connected, the user usually needs to slide several times to have a higher chance of obtaining a good fingerprint image. Sliding fingerprint chips sacrifice the convenience and accuracy of use while reducing costs. Furthermore, multiple sliding is required to obtain identification results, which also causes inconvenience to consumers.

Figure 1 shows a schematic structural view of a conventional fingerprint sensor. As shown in FIG. 1, the conventional sliding fingerprint sensor 500 is a packaged sensor. During the packaging process, the fingerprint chip 513 is placed on a printed circuit board (PCB) substrate 510, and the metal pad 517 is used to connect the wafer pad 515 and the PCB pad 516, and then a molding compound 512 is used as the molding compound. The protective layer protects the metal wire 517. The package form of commercially available capacitive fingerprint wafers is almost all similar to the package structure shown in FIG. The main sensing principle is divided into the principle of capacitive voltage division and the principle of RF sensing. However, the surface of the film is only about a few micrometers to a few tenths of a millimeter (um) thick. Since the cumulative insulating layer thickness of the semiconductor process is about several micrometers (um), if the surface of the wafer is increased by several tens of micrometers or more, the protective layer causes the reference capacitance C _ref generated during sensing to be generated with respect to the finger and the wafer sensing element. The capacitance C _finger will become too large, causing the finger contact difference to be too small, and it is difficult for the reading circuit to judge the difference between the two. Referring to US7099497, for example, V _sensing = V _dd ^* (C _ref / (C _ref + C _finger )), the architecture completed in a general semiconductor process, C _ref will be greater than 100fF, but the maximum area of each sensing unit is only 50 ^* 50um ² , assuming that the thickness of the protective layer is about 50um, the C _finger will be less than 1Ff, so if C _ref >>C _finger , V _sensing =V _dd , the difference between the peaks and valleys of the finger cannot be judged.

An object of the present invention is to provide a method of fabricating a capacitive fingerprint wafer with an insulating substrate and a packaging method thereof.

Another object of the present invention is to achieve the same function as a single semiconductor wafer by utilizing the advantages of an insulating substrate process and a semiconductor wafer process, using a chip-on-chip (COG) or wire bonding method. , but the method of extremely low cost.

Still another object of the present invention is to set the ground potential of the reference electrode to the other side of the insulating substrate by utilizing the characteristics of the process of the insulating substrate, so that the reference capacitor is not uniquely formed by using the semiconductor deposition material as the dielectric layer. A method that has the same function as a single semiconductor wafer, but at a very low cost.

A further object of the present invention is to prevent the thickness of the protective layer on the wafer from being limited due to limitations of the manufacturing structure during the process of providing the package, thereby resulting in a weaker resistance to the external impact of the wafer, and at the same time providing a cheaper, simpler and stronger material. The form of the package.

To achieve the above objective, the present invention provides a capacitive fingerprint sensor comprising an insulating substrate, a sensing and front end processing unit, and a back end processing unit. The sensing and front-end processing unit is disposed on a front surface of the insulating substrate for sensing the texture of the finger and front-end signal processing to generate a plurality of fingerprint analog sensing signals. The back-end processing unit is disposed on the front surface of the insulating substrate, is disposed on the insulating substrate through an anisotropic conductive adhesive, and is electrically connected to the sensing and front-end processing unit, and receives the fingerprint analog sensing signals to sense the fingerprint analogies. The signal is processed into a result signal for output.

The invention also provides a method for manufacturing a capacitive fingerprint sensor, comprising the following steps. First, a sensing and front-end processing unit is formed on a front side of an insulating substrate. Then, a back end processing unit is disposed on the front surface of the insulating substrate. The back end processing unit is disposed on the insulating substrate through an anisotropic conductive paste and electrically connected to the sensing and front end processing unit. The sensing and front-end processing unit senses the texture of the finger and the front-end signal processing to generate a plurality of fingerprint analog sensing signals. The backend processing unit receives the fingerprint analog sensing signals to process each fingerprint analog sensing signal into a result signal for output.

According to the present invention, a liquid crystal display (Thin-Film Transistor (TFT) process is used in a single layer or double Forming a sensing array component including a reference capacitor and a sensing capacitor on the chip insulating substrate, or a sensing structure having a signal emitting source Tx and a signal receiving source Rx, and completing at least one of the insulating substrates Transistor switches, comparators, signal multiplexers, and signal amplifiers. The part of the sensing element circuit output is combined with another circuit element manufactured by a semiconductor wafer process, and the combination method uses the COG mode as the conduction end of the signal end, and the external circuit element includes an analog digital converter (Analog-to -Digital Converter, ADC) and the digital control circuit and image processing circuit, encryption and decryption circuit, memory and scratchpad required for the sensing circuit. Fingerprint image information processed by the circuit. The insulating substrate connected or sensed by the flexible circuit board and the insulating substrate is used as a medium for outputting the external system by a conventional IC package in a conventional IC package. In addition, the manner in which the capacitive fingerprint wafer is completed by the insulating substrate can be completed by completely covering the conventional molding compound or by adhering the reinforced insulating film to the surface.

With this sensing architecture, the possibility of a protective layer thickness on the wafer can be increased, and the packaging specificity of the existing capacitive fingerprint wafer can be avoided (because the wafer must be exposed), so that the wafer can be completely covered with a relatively inexpensive conventional molding compound. The package is completed or protected by reinforced insulation of about 50~150um thickness on the insulating surface. The above method can improve the disadvantage that the existing capacitive fingerprint chip is susceptible to external knocking or scratching, and is resistant to external impact.

The detailed description of the present invention, the technical contents, the features, and the effects achieved by the present invention will become more apparent from the detailed description.

The invention relates to a design structure and a packaging method of a capacitive fingerprint chip, which provides a low-cost capacitive fingerprint chip and a packaging method capable of withstanding external impact. More particularly, the present invention relates to an architecture for fabricating a fingerprint wafer by fabricating a sensing array component and a front-end signal processing circuit on an insulating substrate, and processing the wafer using a COG bonding back-end signal. The fingerprint chip can be externally connected by a flexible circuit board or a conventional semiconductor package.

By utilizing the advantages of the current insulating substrate process, the reference electrode and the ground electrode can be respectively completed on the upper and lower sides of the insulating substrate, so that the distance between the two electrode plates of the reference capacitor can be increased, thereby increasing the thickness of the surface protective layer, that is, letting the finger The distance to the sensing electrode is increased to several tens of micrometers, and the gap between the reference capacitance and the sensing capacitance is not excessively large, which reduces the difficulty in reading the fingerprint signal.

Accordingly, the present invention provides a method of fabricating a capacitive fingerprint wafer and a method of packaging the same, the method of which is not limited to a method of manufacturing a push-type or slide-type fingerprint wafer. The sensing array and the front-end signal processing circuit, which require a larger manufacturing area, are completed on an insulating substrate, and the back-end signal processing chip is completed by the semiconductor wafer, and then the COG technology is used to bond the two together. This method can be fully utilized. At present, the advantages of the insulating substrate process and the semiconductor wafer process alone reduce the cost of the push-type fingerprint wafer to be similar to that of the sliding fingerprint chip, thereby increasing the market acceptance and the applicability of the push-type fingerprint wafer.

2A is a schematic view showing the structure of a capacitive fingerprint sensor 1 according to a first embodiment of the present invention. 2B shows a first embodiment of the present invention Block diagram of capacitive fingerprint sensor 1. Fig. 2C shows a partial enlarged view of Fig. 2A. As shown in FIG. 2A to FIG. 2C, the embodiment provides a capacitive fingerprint sensor 1, which is a fingerprint identification chip completed in a standard package type. The capacitive fingerprint sensor 1 includes an insulating substrate 10, a sensing and front end processing unit 20, and a back end processing unit 30.

The insulating substrate 10 is, for example, a TFT insulating substrate, such as glass or a flexible plastic. The thickness of the insulating substrate 10 is between 50 micrometers and 200 micrometers, preferably between 100 micrometers and 150 micrometers.

The sensing and front-end processing unit 20 is disposed on the front surface 10A of the insulating substrate 10 for sensing the texture of the finger F (see FIG. 4 and FIG. 5) and front-end signal processing to generate a plurality of fingerprint analog sensing signals. SA. In this embodiment, the sensing and front-end processing unit 20 includes a plurality of fingerprint sensing elements 21 and a front-end signal processing unit 26. The fingerprint sensing elements 21 are arranged in a two-dimensional array and are located on the front surface 10A of the insulating substrate 10. Each of the fingerprint sensing elements 21 includes two electrode plates 21A, 21B to form a capacitor, and senses the texture of the finger F during operation to generate a voltage or current sensing signal SR. The front-end signal processing unit 26 is located on the front surface 10A of the insulating substrate 10, is electrically connected to the fingerprint sensing elements 21, and processes the voltage or current sensing signal SR into the fingerprint analog sensing signals SA. The fingerprint sensing element 21 and the front end signal processing unit 26 can be completed simultaneously or at different times in the same series of processes.

The back end processing unit 30 is disposed on the front surface 10A of the insulating substrate 10, is disposed on the insulating substrate 10 through an anisotropic conductive adhesive 40, and is electrically connected to the sensing and front end processing unit 20, and receives the fingerprint analog sensing signals. The SA processes the fingerprint analog sensing signals SA into a result signal SD as a basis for grayscale image output.

In addition, the capacitive fingerprint sensor 1 may further include a plurality of first contacts 50 and a plurality of first pads 55. The first contact 50 and the first pad 55 are disposed on the insulating substrate 10 , and the first contacts 50 are electrically connected to the front end signal processing unit 26 and electrically connected to the back end processing unit 30 through the anisotropic conductive adhesive 40 . The plurality of input contacts 31 are electrically connected to the plurality of output contacts 32 of the back end processing unit 30 via the anisotropic conductive paste 40.

Furthermore, the capacitive fingerprint sensor 1 can further include a ground layer 60, a package substrate 70, a plurality of wires 75, and a mold plastic layer 80.

The ground layer 60 is disposed on the back surface 10B of one of the insulating substrates 10 and connected to the ground potential. The package substrate 70 has a plurality of second pads 72, and the ground layer 60 is connected to the package substrate 70 by a conductive paste 67. These wires 75 electrically connect the first pads 55 to the second pads 72, respectively. The molding compound layer 80 covers the insulating substrate 10, the sensing and front end processing unit 20, the back end processing unit 30, the first bonding pads 55, the second bonding pads 72, the bonding wires 75, and the package substrate 70.

FIG. 3A is a block diagram showing the structure of a capacitive fingerprint sensor 1' according to a second embodiment of the present invention. This is a fingerprint identification wafer completed by FPC on Glass (FOG), the embodiment of which is described in detail later. This embodiment is similar to the first embodiment except that the capacitive fingerprint sensor 1 ′ further includes a ground layer 60 , two flexible circuit boards 92 , 94 , a second insulating substrate 80 ′ and a protective adhesive 85 . . The ground layer 60 is disposed on the back surface 10B of one of the insulating substrates 10 and connected to the ground potential. The two flexible circuit boards 92 and 94 are respectively connected to the first pad 55 and the ground layer 60. The ground layer 60 is connected to the flexible circuit board 92 via the flexible circuit board 94. The front end processing unit 20 and the back end processing unit are connected. 30 forms an electrical common ground to form a reference capacitance C _ref and a parasitic capacitance C _{par of} FIG. The second insulating substrate 80 ′ covers the insulating substrate 10 and the sensing and front end processing unit 20 . The protective glue 85 covers the rear end processing unit 30.

FIG. 3B is a block diagram showing the structure of a capacitive fingerprint sensor 1'A according to a modification of the second embodiment of the present invention. This is a fingerprint identification wafer completed by FPC on Glass (FOG). This embodiment is similar to the first embodiment except that the capacitive fingerprint sensor 1'A further includes a ground layer 60, two flexible circuit boards 92, 94, and a second insulating substrate 80'. The ground layer 60 is disposed on the back surface 10B of one of the insulating substrates 10 and connected to the ground potential. Two flexible circuit boards 92, 94 are connected to the first pads 55 and the ground layer 60, respectively. The second insulating substrate 80 ′ covers the insulating substrate 10 and the sensing and front end processing unit 20 . The back end processing unit 30 is disposed on the flexible circuit board 92 by electrically bonding the pad 30P of the back end processing unit 30 and the pad 92P on the flexible circuit board 92, and is electrically connected to the sensing and front end processing unit. 20. In this way, the fabrication of the back end processing unit 30 and the flexible circuit board 92 can be integrated, and then the flexible circuit board 92 can be electrically connected to the first pad 55. Therefore, the capacitive fingerprint sensor 1'A of the present example includes an insulating substrate 10, a sensing and front end processing unit 20, a flexible circuit board 92, and a back end processing unit 40. The sensing and front-end processing unit 20 is disposed on the front surface 10A of the insulating substrate 10 for sensing the texture of the finger and the front The signal processing is performed to generate a plurality of fingerprint analog sensing signals. The flexible circuit board 92 is electrically connected to the plurality of first pads 55 on the insulating substrate 10, the first pads 55 are electrically connected to the sensing and front end processing unit 20, and the back end processing unit 30 is passed through the back end processing unit 30. The pad 30P and the pad 92P on the flexible circuit board 92 are bonded to each other and disposed on the flexible circuit board 92 and electrically connected to the sensing and front end processing unit 20, and receive the fingerprint analog sensing signals SA to compare the fingerprints. The sensing signal SA is processed into a result signal SD for output.

4 and 5 are schematic diagrams showing two sensing principles of the capacitive fingerprint sensor of the present invention. The sensing principle of the front end processing unit 20 and the implementation principle of the front end processing unit 20 are shown in FIG. 4 , which is a schematic diagram of a fingerprint sensing unit of a capacitor voltage division principle. The finger F touches the molding compound layer 80, the sensing electrode plate 21A forms a sensing capacitance C _finger with the finger F through the molding compound layer 80, and the reference electrode plate 21B forms a reference capacitance with the grounding layer 60 of the sensing circuit. C _ref , the sensing electrode plate 21A and the ground layer 60 form a parasitic capacitance C _par . A transistor switch TR is connected to the sensing electrode plate 21A and the reference electrode plate 21B to form a metal oxide semiconductor (MOS) capacitor Cud. If the fingerprint wafer requires a thicker molding layer 80 (>50um) as the protective layer, the parasitic capacitance C _par and the reference capacitance C _{ref of} the semiconductor fingerprint wafer may be due to the insulating layer of the complementary metal oxide semiconductor (CMOS) process. The cumulative thickness is typically only a few microns (<4um), causing the parasitic capacitance C _par and the reference capacitance C _{ref to} be much larger than the sensing capacitance C _finger . This will cause the change of the sensing capacitance C _finger to be easily detected by the sensing circuit, C _ref is about one hundred fF, and the C _finger is less than about 5fF. However, the insulating substrate 10 is an insulating dielectric layer having a thickness of 100 to 200 um, which causes mutual inductance to be generated at a level of about 1 fF, which also makes the design on the circuit easier. In this example, the two electrode plates 21A, 21B face each other and are located at different heights on the front surface 10A of the insulating substrate 10.

Regarding another application example, the sensing and front-end processing unit 20 is completed on the insulating substrate 10. As shown in FIG. 5, the sensing principle of each sensing unit (including the sensing electrode plate 21A and the reference electrode plate 21B) is Based on the transmitted signal and the received signal. The sensing electrode plate 21A and the reference electrode plate 21B are electrically connected to a radio frequency (RF) emission source Tx and a receiving source Rx, respectively. In this example, the sensing electrode plate 21A and the reference electrode plate 21B are referred to as a group of emission. With the receiving unit. The finger contact molding layer 80 generates a capacitance Cfinger, which causes the receiving source Rx to receive the change of the RF signal, and the fingerprint image is sensed by the signal change at the receiving end. In this example, the two electrode plates 21A, 21B are located at the same height on the front surface 10A of the insulating substrate 10, and the two electrode plates 21A, 21B are respectively connected to the transmitting source Tx and the receiving source Rx, respectively, by the signal received at the receiving source. An image of the texture of the finger is sensed. It is worth noting that in Figure 5, there is no presence of the ground plane 60.

6A to 6D are structural diagrams showing the steps of a method of manufacturing the capacitive fingerprint sensor 1 according to the first embodiment of the present invention. The manufacturing method of the capacitive fingerprint sensor 1 of the present embodiment includes the following steps.

First, as shown in FIG. 6A, the sensing and front end processing unit 20 is formed on the front surface 10A of the insulating substrate 10. In this step, together with FIG. 2A to FIG. 2C, a plurality of fingerprint sensing elements 21 are formed on the front surface 10A of the insulating substrate 10, and the front end signal processing unit 26 is formed on the insulating substrate. 10 on the front 10A. In addition, a plurality of first contacts 50 and a plurality of first pads 55 may be simultaneously formed on the insulating substrate 10. Therefore, the sensing and front end processing unit 20, the ground layer 60, and the first pad 55 can be completed by a TFT or Low Temperature Poly-Silicon (LTPS) process. In order to mass-produce to reduce the cost, the step of forming the sensing and front-end processing unit 20 on the front surface 10A of the insulating substrate 10 can be performed in the following manner. As shown in FIG. 6A, first, a plurality of sensing and front end processing units 20 and a plurality of first pads 55 are formed on one front surface 10AM of a general insulating substrate 10M. Next, a bulk ground layer 60M is formed on one of the back faces 10BM of the overall insulating substrate 10M. It should be noted that the overall ground plane 60M may be formed earlier than the sensing and front end processing unit 20 and the plurality of first pads 55. Then, cutting along the cutting line CT to separate the paired sensing and front end processing unit 20 and the first pad 55 while separating the overall ground layer 60M into a plurality of ground layers 60, each ground layer 60 It is combined with the sensing and front end processing unit 20 and the first pad 55. The single structure after the cutting is completed is shown in Fig. 6B.

Next, as shown in FIG. 6C, after the sensing and front-end processing unit 20 is formed, the back-end processing unit 30 is disposed on the front surface 10A of the insulating substrate 10. In implementation, the back end processing unit 30 can be attached to the insulating substrate 10 by a COG bonding method. The backend processing unit 30 involves relatively complex functionality in circuit design and can be implemented using a semiconductor process. Referring to FIGS. 2B to 2C , the back end processing unit 30 is disposed on the insulating substrate 10 through the anisotropic conductive adhesive 40 and electrically connected to the sensing and front end processing unit 20 . The anisotropic conductive adhesive 40 has a vertical conduction characteristic, and can easily electrically connect two upper and lower components to achieve a signal. Input and output functions.

Further, the above manufacturing method may further include the following steps. First, the ground layer 60 is formed on the back surface 10B of the insulating substrate 10. Then, the ground layer 60 is disposed on a package substrate (such as a PCB substrate) 70 having a plurality of second pads 72 using a conductive paste 67 (see FIG. 1). Then, the first pads 55 are electrically connected to the second pads 72 by a plurality of wires 75, respectively. Then, a molding plastic layer 80 is provided to cover the insulating substrate 10, the sensing and front end processing unit 20, the back end processing unit 30, the first bonding pads 55, the second bonding pads 72, the wires 75 and the package substrate 70. The formed capacitive fingerprint sensor 1 is as shown in FIG. 6D. Therefore, it is possible to complete a finished standard package, similar to a quad flat no-lead (QFN) implemented fingerprint wafer finished product.

7A to 7D are structural diagrams showing the steps of a method of manufacturing a capacitive fingerprint sensor 1' according to a second embodiment of the present invention. This embodiment is similar to the first embodiment, except that after the ground layer 60 is formed on the back surface 10B of the insulating substrate 10, the two first flexible pads 92 and 94 are respectively connected to the first pads 55 and connected. Formation 60. For mass production, as shown in FIG. 7A, after the sensing and front end processing unit 20 and the overall ground layer 60M are respectively formed on the front and back surfaces of the overall insulating substrate 10M, an overall second insulating substrate 80M' is provided to cover the entire insulating substrate 10M and These sensing and front end processing units 20 are shown in Figure 7B. The overall second insulating substrate 80M' is used as a protective insulating layer, and the bonding manner thereof can be adhered to the non-conductor material. The coating range of the bonding material is sensed and the front end processing unit 20 does not affect the bonding processing of the back end processing unit 30. limit. The protective insulating layer can be selected to have an appropriate thickness, or The method of grinding reaches the thickness of the signal processing circuit suitable for the design of the fingerprint chip circuit. Next, two cuts are made along the two cut lines CT to complete a plurality of unpackaged sense wafers (referred to as double layer insulation sense array units), one of which is shown in Figure 7C. Then, the back end processing unit 30 is connected to the insulating substrate 10 by the COG bonding method, and a protective adhesive 85 is provided to cover the back end processing unit 30, and is connected to the first bonding pad 55 by the flexible circuit boards 92 and 94, respectively. The formation 60 completes the above-described wire bonding and completes the signal output path to complete the capacitive fingerprint sensor 1', as shown in FIG. 7D.

8A to 8D are structural diagrams showing the steps of a method of manufacturing a capacitive fingerprint sensor 1" according to a third embodiment of the present invention. This embodiment is similar to the second embodiment except that the embodiment is After the structure of FIG. 8A is formed, a total protective layer 90M is further formed on the overall second insulating substrate 80M', as shown in FIG. 8B. The overall protective layer 90M may be a color coating, which is used in conjunction with the application product. To achieve an aesthetic function, the color can be any color that can be adjusted. Then, cutting along the cutting line to form the structure of FIG. 8C, and then performing the packaging process as shown in FIG. 7D to obtain FIG. 8D. The capacitive fingerprint sensor shown is 1". Thus, the capacitive fingerprint sensor 1" includes a protective layer 90 on the sensing and front end processing unit 20 to protect the sensing and front end processing unit 20 or to provide a color appearance for the entire product.

Therefore, the present invention provides a method for manufacturing a capacitive fingerprint wafer and a package method thereof, and the structure of the sensing array including the reference capacitor and the sensing capacitor is completed on the single-layer or double-layer insulating substrate by using the LCD TFT process, or has a signal Sensing structure of the source and signal receiving source, and One of the insulating substrates completes the front-end signal processing circuit, and the front-end signal processing circuit circuit can include at least one transistor switching switch, a comparator, a signal multiplexer, and a signal amplifier or any circuit architecture that can implement a signal processing. The signal output processed by the front sensing signal processing circuit is combined with the rear end signal processing chip manufactured by at least one semiconductor wafer process on the insulating substrate, and the combination method uses the COG method as the conduction end of the signal end point. The rear signal processing chip can include an analog digital converter ADC and a digital control circuit required for the sensing circuit, a parallel, serial or USB transmission interface, an image processing circuit, an encryption and decryption circuit, a memory, a register, and a fingerprint. A fully functional circuit component of a wafer. The fingerprint image processed by the back-end signal processing chip is connected to the insulating substrate by a flexible circuit board or the insulating substrate is used as a medium for external output by a conventional IC package. The method of encapsulating the capacitive fingerprint wafer by the insulating substrate can be completely covered by a conventional molding compound or attached to the surface by reinforced insulation. The method avoids the problem that the conventional semiconductor capacitive fingerprint sensing component requires a large area due to the sensing of the finger, and the manufacturing cost is too high, and the external exposure of the germanium wafer is caused by ESD and resistance. The problem of insufficient impact capability.

Therefore, the design structure and the packaging method of the capacitive fingerprint wafer completed by the insulating substrate provided by the present invention have the advantages that the area of the general insulating substrate is much larger than the area of the wafer. Compared with the middle generation 4.5G panel of 730×920mm ² and the 12吋 wafer 150×150×π, the fingerprint sensing array cut by about 1cm ^{2 has} a difference of 25 times. Furthermore, by using a semiconductor wafer process, the circuit that requires a fine process is miniaturized, and the structure of the fingerprint chip is completed by using a conventional COG process adhered to the unit insulating substrate, which can effectively save the manufacturing cost of the pressed fingerprint chip. . It should be noted that the structure and manufacturing method of the present invention are equally applicable to a sliding fingerprint sensing wafer.

With this sensing architecture, the possibility of a protective layer thickness on the wafer can be increased, and the packaging specificity of the existing capacitive fingerprint wafer can be avoided (because the wafer must be exposed), so that the wafer can be completely covered with a relatively inexpensive conventional molding compound. The package is completed or protected by reinforced insulation of approximately 100~200um thickness on the insulating surface. The above method can improve the disadvantage that the existing capacitive fingerprint chip is susceptible to external knocking or scratching, and is resistant to external impact.

The specific embodiments of the present invention are intended to be illustrative only and not to limit the invention to the above embodiments, without departing from the spirit of the invention and the following claims. The scope of the invention and the various changes made are within the scope of the invention.

C _finger ‧‧‧ Sense capacitance

C _par ‧‧‧Parasitic capacitance

C _ref ‧‧‧reference capacitor

CT‧‧‧ cutting line

C _ud ‧‧‧ capacitor

F‧‧‧ finger

Rx‧‧‧ receiving source

SA‧‧‧ analog analog signal

SD‧‧‧ result signal

SR‧‧‧Sensior signal

TR‧‧‧Chip Switch

Tx‧‧‧ source

1, 1', 1'A, 1"‧‧‧ Capacitive fingerprint sensor

10‧‧‧Insert substrate

10A, 10AM‧‧‧ positive

10B, 10BM‧‧‧ back

10M‧‧‧General insulating substrate

20‧‧‧Sensing and front-end processing unit

21‧‧‧Finger sensing element

21A‧‧‧Sensor electrode plate

21B‧‧‧Reference electrode plate

26‧‧‧ Front-end signal processing unit

30‧‧‧Back-end processing unit

30P‧‧‧ solder pads

31‧‧‧Input contacts

32‧‧‧Output contacts

40‧‧‧ anisotropic conductive adhesive

50‧‧‧First contact

55‧‧‧First pad

60‧‧‧ Grounding layer

60M‧‧‧ overall ground plane

67‧‧‧Electrical adhesive

70‧‧‧Package substrate

72‧‧‧Second pad

75‧‧‧Line

80‧‧‧Molded plastic layer

80'‧‧‧second insulating substrate

80M'‧‧‧ overall second insulating substrate

85‧‧‧Protective adhesive

90‧‧‧Protective layer

90M‧‧‧ overall protective layer

92, 94‧‧‧Soft circuit board

92P‧‧‧ pads

500‧‧‧Finger sensor

510‧‧‧Printed circuit board substrate

512‧‧‧Molded plastic

513‧‧‧ fingerprint chip

515‧‧‧ wafer pads

516‧‧‧PCB pads

517‧‧‧Line

FIG. 1 shows a schematic structural view of a conventional sliding fingerprint sensor.

2A is a schematic view showing the structure of a capacitive fingerprint sensor according to a first embodiment of the present invention.

2B is a block diagram showing a capacitive fingerprint sensor in accordance with a first embodiment of the present invention.

Fig. 2C shows a partial enlarged view of Fig. 2A.

3A is a block diagram showing the structure of a capacitive fingerprint sensor in accordance with a second embodiment of the present invention.

3B is a block diagram showing the structure of a capacitive fingerprint sensor according to a modification of the second embodiment of the present invention.

4 and 5 are schematic diagrams showing two sensing principles of the capacitive fingerprint sensor of the present invention.

6A to 6D are structural diagrams showing the steps of a method of manufacturing a capacitive fingerprint sensor according to a first embodiment of the present invention.

7A to 7D are structural diagrams showing the steps of a method of manufacturing a capacitive fingerprint sensor according to a second embodiment of the present invention.

8A to 8D are structural diagrams showing the steps of a method of manufacturing a capacitive fingerprint sensor according to a third embodiment of the present invention.

1‧‧‧Capacitive fingerprint sensor

10‧‧‧Insert substrate

10A‧‧‧ positive

10B‧‧‧Back

20‧‧‧Sensing and front-end processing unit

30‧‧‧Back-end processing unit

40‧‧‧ anisotropic conductive adhesive

55‧‧‧First pad

60‧‧‧ Grounding layer

67‧‧‧Electrical adhesive

70‧‧‧Package substrate

72‧‧‧Second pad

75‧‧‧Line

80‧‧‧Molded plastic layer

Claims (12)

A capacitive fingerprint sensor includes: an insulating substrate; a sensing and front-end processing unit disposed on a front surface of the insulating substrate for sensing a finger pattern and front-end signal processing to generate a plurality of a fingerprint analog sensing signal; and a back-end processing unit disposed on the front surface of the insulating substrate, disposed on the insulating substrate through an anisotropic conductive paste, and electrically connected to the sensing and front-end processing unit, and receiving the The fingerprint analog sensing signal is used to process each of the fingerprint analog sensing signals into a result signal for output. The capacitive fingerprint sensor of claim 1, wherein the sensing and front-end processing unit comprises: a plurality of fingerprint sensing elements on the front surface of the insulating substrate, each of the fingerprint sensing elements comprises The two electrode plates are formed to form a capacitor or a group of transmitting and receiving units, and sense the texture of the finger to generate a sensing signal; and a front end signal processing unit is disposed on the front surface of the insulating substrate and electrically connected to The fingerprint sensing elements are processed into the fingerprint analog sensing signals. The capacitive fingerprint sensor of claim 2, further comprising: a plurality of first contacts and a plurality of first pads disposed on the insulating substrate, the first contacts being electrically connected to The front-end signal processing unit is electrically connected to the plurality of input contacts of the back-end processing unit through the anisotropic conductive adhesive, and the first pads are electrically connected to the rear through the anisotropic conductive adhesive A plurality of output contacts of the end processing unit. The capacitive fingerprint sensor of claim 3, further comprising: a ground layer disposed on a back surface of the insulating substrate and connected to the ground potential; a package substrate having a plurality of second pads The ground layer is connected to the package substrate by using a conductive adhesive material; a plurality of wires are electrically connected to the second pads respectively; and a molding plastic layer covering the insulating substrate, the a sensing and front end processing unit, the back end processing unit, the first bonding pads, the second bonding pads, the bonding wires, and the package substrate. The capacitive fingerprint sensor of claim 3, further comprising: a ground layer disposed on a back surface of the insulating substrate and connected to the ground potential; and two flexible circuit boards respectively connected to the first a solder pad and the ground layer; a second insulating substrate covering the insulating substrate and the sensing and front end processing unit; and a protective glue covering the back end processing unit. A capacitive fingerprint sensor includes: an insulating substrate; a sensing and front-end processing unit disposed on a front surface of the insulating substrate for sensing a finger pattern and front-end signal processing Generating a plurality of fingerprint analog sensing signals; a flexible circuit board electrically connected to the plurality of first pads on the insulating substrate, the first pads electrically connected to the sensing and front end processing unit; and a back end The processing unit is disposed on the flexible circuit board and electrically connected to the sensing and front-end processing unit by bonding the pads of the back-end processing unit and the pads on the flexible circuit board to each other, and receiving the fingerprint analogy The test signal is used to process each of the fingerprint analog sensing signals into a result signal for output. A method for manufacturing a capacitive fingerprint sensor, comprising the steps of: forming a sensing and front-end processing unit on a front surface of an insulating substrate; and providing a rear-end processing unit on the front surface of the insulating substrate, The end processing unit is disposed on the insulating substrate through an anisotropic conductive adhesive and electrically connected to the sensing and front-end processing unit, wherein the sensing and front-end processing unit is configured to sense the texture of the finger and front-end signal processing. A plurality of fingerprint analog sensing signals are generated, and the back-end processing unit receives the fingerprint analog sensing signals to process each of the fingerprint analog sensing signals into a result signal for output. The manufacturing method of claim 7, wherein the step of forming the sensing and front-end processing unit comprises: forming a plurality of fingerprint sensing elements on the front surface of the insulating substrate; and simultaneously forming a front-end signal processing unit On the front surface of the insulating substrate, each of the fingerprint sensing elements senses the texture of the finger to A sensing signal is generated, and the front-end signal processing unit is electrically connected to the fingerprint sensing elements, and the sensing signals are processed into the fingerprint analog sensing signals. The manufacturing method of claim 8, further comprising the steps of: forming a plurality of first contacts and a plurality of first pads on the insulating substrate, the first contacts being electrically connected to the front end signal The processing unit is electrically connected to the plurality of input contacts of the back end processing unit through the anisotropic conductive glue, and the first pads are electrically connected to the plurality of back end processing units through the anisotropic conductive adhesive Output contact. The manufacturing method of claim 9, further comprising the steps of: forming a ground layer on a back surface of the insulating substrate; and disposing the ground layer on a package substrate having a plurality of second pads; Electrically connecting the first pads to the second pads by using a plurality of wires; and providing a molding plastic layer covering the insulating substrate, the sensing and front end processing unit, the back end processing unit, the first a pad, the second pad, the wire, and the package substrate. The manufacturing method of claim 9, further comprising the steps of: forming a ground layer on a back surface of the insulating substrate; and connecting the first bonding pad and the ground layer by using two flexible circuit boards. Providing a second insulating substrate covering the insulating substrate and the sensing and front end processing unit; and providing a protective adhesive covering the back end processing unit. The manufacturing method of claim 7, wherein the step of forming the sensing and front-end processing unit on the front surface of the insulating substrate comprises: forming a plurality of sensing and front-end processing units and a plurality of first pads On a front side of one of the overall insulating substrates; and performing cutting to separate the sensing and front end processing unit and the first bonding pad that are grouped together.