KR100562874B1 - Method for assembling z-axis thin-film fluxgate device in a electronic compass - Google Patents

Abstract

The present invention relates to a method for assembling a thin film fluxgate device for a vertical axis (z-axis) fabricated on a wafer on a substrate, wherein the groove is formed along an electrical terminal end of the z-axis thin film fluxgate device arranged on the wafer. Forming a grooving step; Depositing an insulating thin film extending from the distal end of the electrical terminal to the side wall of the groove; Depositing the conductive thin film electrically connected to the electrical terminal and extending from the insulating thin film to the sidewall portion of the groove; Cutting the z-axis thin film fluxgate element having the connection terminal formed on the sidewall of the groove for each unit element; Die bonding the cut z-axis thin film fluxgate element to a substrate such that a connection terminal of the z-axis thin film fluxgate element faces upward on the substrate; Die bonding a driving element for driving the z-axis thin film fluxgate element to the substrate; Wire bonding the connection terminal of the z-axis thin film fluxgate element bonded to the substrate and the electrical terminal of the driving element. According to the present invention, there is an advantage in that each terminal of the thin film fluxgate device for the z-axis and the ASIC driving device for driving the thin film fluxgate device can be electrically coupled by a conventional vertically movable wire bonding process.

Fluxgate, electronic compass, wire bonding, vertical axis, z axis

Description

Assembly method of vertical axis thin film fluxgate device for electronic compass {METHOD FOR ASSEMBLING Z-AXIS THIN-FILM FLUXGATE DEVICE IN A ELECTRONIC COMPASS}

1 is an exemplary view of a thin film fluxgate device.

2 is a structural diagram of an electronic compass employing a three-axis thin film fluxgate sensor.

3 is a diagram illustrating a wire bonding process of the electronic compass shown in FIG.

4 is a diagram illustrating a state of connecting wires between terminals of a z-axis thin film fluxgate device and an ASIC driving device in a three-axis measurement electronic compass according to a preferred embodiment of the present invention.

Fig. 5 is a state diagram in which a thin film fluxgate element 16 'and a terminal thereof are formed on an upper surface of a silicon wafer.

FIG. 6 is a state diagram grooved in the silicon wafer of FIG. 5; FIG.

7 is a perspective view of a z-axis thin film fluxgate device in which groove processing is completed.

FIG. 8 is a state diagram in which a photoresist coating film for forming an insulating thin film is formed on the z-axis thin film fluxgate device of FIG. 7; FIG.

9 is a state in which an insulating thin film is formed subsequent to the photoresist process of FIG. 8 and the photoresist coating film is removed.

FIG. 10 is a state diagram in which a secondary photoresist coating film is formed to form a conductive thin film in a grooved vertical portion subsequent to formation of the insulating thin film of FIG. 9;

11 is a state in which a conductive thin film is formed subsequent to the secondary photoresist process of FIG. 10 and the above-described secondary photoresist coating film is removed.

FIG. 12 is a state diagram in which the z-axis thin film fluxgate element on the wafer is cut for each element following the formation of the conductive thin film of FIG. 11;

FIG. 13 is a diagram illustrating a state of die bonding a thin film fluxgate device for a z-axis according to a preferred embodiment of the present invention onto an electronic compass PCB substrate. FIG.

FIG. 14A is an exemplary diagram of a process of wire bonding a thin film fluxgate element for an z-axis and an ASIC drive element following die bonding of FIG. 13. FIG.

FIG. 14B is a state diagram in which wire bonding is completed between terminals of the z-axis thin film fluxgate device and the ASIC driving device according to the preferred embodiment of the present invention; FIG.

<Description of the symbols for the main parts of the drawings>

1, 24: silicon wafer 2, 4, 26, 36: insulating thin film

3: lower conductor 5: magnetic thin film

6: upper conductor 7, 7 ', 20: electrical terminal

10: PCB board for electronic compass

12: Thin film fluxgate element for x-axis

14: y-axis thin film fluxgate element

16, 16 ': z-axis thin film fluxgate element 18: ASIC drive element

22: wire bonding tip 28: groove

30 groove vertical portion 32 photoresist coating film

34: insulating thin film forming portion 38: secondary photoresist coating film

40: conductive thin film 42: connection terminal

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluxgate sensor, and more particularly, to a vertical axis thin film fluxgate device for an electron compass and a method for assembling thereof.

The fluxgate sensor applies an alternating current to a drive coil wound around the magnetic core of high magnetic permeability, and by means of a separate pick-up coil, an external magnetic field (eg, geomagnetic field) according to the magnetic saturation and nonlinear magnetic characteristics of the magnetic core. It is a device for measuring the magnitude of an external magnetic field by detecting a second harmonic component proportional to. The fluxgate sensor can be manufactured in a relatively high sensitivity and small size compared to other magnetic sensors, and has excellent output signal stability. Accordingly, it has been widely used in civil and military applications, ranging from electronic compass functions of portable devices, exploration of veins, target detection, and attitude control of satellites.

1 illustrates a structure of a fluxgate sensor manufactured in the form of a thin film device on a silicon wafer using a semiconductor process, and is filed in Korean Patent Application No. 2004-86695 (October 28, 2004) filed by the present applicant. ) As described in "Bar-like thin film fluxgate and method for manufacturing the same".

As shown, the thin film fluxgate element is an insulating thin film 2, a lower conductor 3, an insulating thin film 4, a magnetic thin film 5, an upper portion on the silicon wafer 1 based on the AA 'cutting plane. The conductor 6 has a stacked structure in a thin film form, and the insulating thin film 2 serves to prevent a short circuit between the silicon wafer 1 and the lower conductor 3. The lower conductor 3 and the upper conductor 6 may be electrically connected to each other and disposed along the length direction of the magnetic thin film 5 to form the drive coil and the pickup coil of the aforementioned fluxgate sensor. The drive coil electrical terminal (or current input electrical terminal) 7 applies alternating current to the drive coil, and the pickup coil electrical terminal (or current output electrical terminal) 7 'detects the output signal from the pickup coil. These electrical terminals 7 and 7 'are formed on the silicon wafer 1 in such a size that wire bonding with the driving circuit is possible.

By the way, when the orientation is measured by an electronic compass provided with one fluxgate sensor, the magnitude of the declination with the south pole or the north pole can be measured, but it is not possible to determine whether the direction of the deflection is east or west. Therefore, in order to grasp both east, west, north and south, two fluxgates (i.e., biaxial fluxgates) should be used to detect the horizontal component (components on the x and y axes) of the geomagnetic field, where each fluxgate is orthogonal to each other. It is preferably arranged to.

In addition, since the fluxgate sensor constituting the electronic compass detects only the horizontal component of the earth's magnetic field, a significant direction measurement error occurs when the electronic compass element is not leveled with the ground surface accurately. Therefore, the correct orientation can be calculated by detecting the vertical axis component (ie, the z-axis component) of the geomagnetic field and correcting an error when the fluxgate is out of horizontal. For this purpose, the three-axis fluxgate can be used.

Meanwhile, in recent years, geographic information services (GIS) provided through mobile terminals such as mobile phones and PDAs have become commonplace, and in order to use them more conveniently, a map displayed on the display of the portable terminal is used. It is necessary to match the direction of to the direction of the user. To this end, there is a need for a very small electronic compass that can be mounted on the portable terminal to detect the direction of the user.

2 illustrates a structure of an electronic compass employing a three-axis thin film fluxgate sensor to be mounted on a portable terminal.

As shown in FIG. 2, the three-dimensional measuring electronic compass includes three fluxgate elements 12, 14, and 16 disposed on the electronic compass PCB substrate 10 and an ASIC driving element 18 driving them. Consists of. Three fluxgate elements 12, 14 and 16 are arranged on the substrate in the x, y and z axes, and the fluxgate elements 12, 14 and 16 and the terminal 20 of the ASIC drive element 18 are conducting wires. They are electrically connected to each other via a bonding wire (not shown).

Each fluxgate element is made of a magnetic material, an insulator, a drive coil, and a pickup coil described above with reference to FIG. 1 in the form of a thin film element on a silicon wafer by a semiconductor process, and the drive coil and the pickup coil are replaced with an ASIC drive element 18. And a terminal 20 for wire bonding are formed together. After the thin film processing is completed, the fluxgate element is cut into individual element bodies using a dicing saw, and then the back surface is attached to the substrate 10 through die bonding. On the other hand, the configuration and manufacturing process of the thin film fluxgate device is disclosed in detail in a patent application filed by the applicant.

Regarding the arrangement of these four unit elements 12, 14, 16 and 18, the thin film fluxgate elements 12 and 14 for the x-axis and the y-axis and the ASIC drive element 18 are thin film elements fabricated on the silicon wafer surface. And an electrical terminal face upward. On the other hand, for the z-axis thin film fluxgate device, the surface where the thin film device is formed, that is, the surface on which the thin film device and the electrode pattern are formed (hereinafter referred to as the “element surface”) for the z-axis geomagnetic measurement, is an electronic compass PCB board. It should be mounted perpendicular to (10).

According to this configuration, since the thin film fluxgate elements 12 and 14 and the ASIC drive element 18 for the x- and y-axes have an element surface parallel to the PCB substrate 10 and the terminals requiring electrical connection are directed upward, It can be easily electrically connected by the usual vertical movable wire bonding. However, in the case of the thin film fluxgate element 16 for the z-axis whose element surface faces the side, the conductor connection of the terminal cannot be performed with a conventional vertically movable wire bonding machine. In this regard, FIG. 3 illustrates a wire bonding process for assembling the electronic compass of FIG. 2.

As shown in FIG. 3, in order to electrically connect the terminal of the ASIC drive element 18 and the terminals of the thin film fluxgate elements 12 and 14, for example, a conductor made of Al (aluminum) or Au (gold). Position the wire to the terminal portion to be connected, and connect the terminal by moving the wire bonding tip (wire bonding tip) 22 vertically. For example, the head (not shown) of the wire bonding machine provided with the above-described wire bonding tip 22 moves vertically in the portion A to take the electrical terminal of the ASIC drive element and return vertically. Subsequently, after horizontally moving to the position of B, vertically moving downward to take the portion B, electrical connection between the two unit elements is made.

However, since the z-axis thin film fluxgate device is disposed so that the device surface faces to the side, the terminal is perpendicular to the PCB substrate 10 so that there is a problem in that electrical contact cannot be formed by the above-described vertical wire bonding process. .

In order to solve the above problems, the present invention, in the assembly of a three-axis measuring electronic compass having three thin-film flux element, the wire bonding of the terminal of the z-axis thin-film fluxgate element and the ASIC drive element for driving the same The purpose is to be able to be electrically coupled by the process.

In order to achieve the above object, according to the first aspect of the present invention, there is provided a method for assembling a thin film fluxgate element for a vertical axis (z-axis) manufactured on a wafer on a substrate, and arranged on the wafer a groove forming step of forming a groove along an electrical terminal end of the z-axis thin film fluxgate element; Depositing a conductive thin film extending from the electrical terminal to the sidewall portion of the groove to form a connection terminal on the sidewall portion of the groove; Cutting the z-axis thin film fluxgate element having the connection terminal formed on the sidewall of the groove for each unit element; Die bonding the cut z-axis thin film fluxgate element to a substrate such that a connection terminal of the z-axis thin film fluxgate element faces upward on the substrate; Die bonding a driving element for driving the z-axis thin film fluxgate element to the substrate; Wire bonding the connection terminal of the z-axis thin film fluxgate element bonded to the substrate and the electrical terminal of the driving element.

At this time, the groove processing step preferably forms a groove parallel to the distal end of the electrical terminals arranged horizontally on the wafer. The connecting terminal forming step may include forming an insulating thin film extending from the end side of the electrical terminal to the side wall portion of the groove, and electrically connecting to the electrical terminal and extending to the side wall portion of the groove on the insulating thin film. And forming the conductive thin film.

In the conductive thin film deposition step, the conductive thin film is formed to have a smaller width than the insulating thin film.

According to a second aspect of the present invention, there is provided a thin film fluxgate device for z-axis having a thin film element and an electrical terminal formed on an element surface and having a connection terminal perpendicular to the element surface, wherein an end portion of the electrical terminal arranged on the element surface is provided. An insulating thin film extending from the sidewall portion perpendicular to the element surface; And a connection terminal electrically connected to the electrical terminal and formed on the insulating thin film to the sidewall with a narrower width than the insulating thin film.

Finally, according to the third aspect of the present invention, there is provided a three-axis measuring electronic compass in which a thin film fluxgate element for x, y and z axes and a driving element are assembled on a substrate. In this case, the z-axis thin film fluxgate element may include an insulating thin film extending from a distal end of an electrical terminal arranged on an element surface to a sidewall portion perpendicular to the element surface, and electrically insulated from the electrical terminal and on the insulating thin film. It includes a connection terminal formed to the side wall portion narrower than the thin film. The electronic compass is die-bonded such that a sidewall portion of the z-axis thin film fluxgate element faces upward on the substrate, and wire bonding is performed between the x, y, and z-axis thin film fluxgate elements and the terminal of the driving element. The bonding surface is parallel to the substrate.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings, and like reference numerals refer to like or similar components throughout the drawings.

FIG. 4 is a diagram illustrating a state of connecting wires between terminals of a z-axis thin film fluxgate device and an ASIC driving device in a three-axis measurement electronic compass according to a preferred embodiment of the present invention.

As shown in FIG. 4, the z-axis thin film fluxgate device 16 ′ according to the preferred embodiment of the present invention has a conductive thin film electrically connected to a terminal of the thin film device on an element body that forms 90 degrees with the device surface. By further forming, a separate electrical terminal (hereinafter referred to as a "connection terminal") extending from the thin film element is provided on the element body parallel to the substrate 10.

According to this configuration, the thin film fluxgate element 16 'for the z-axis has a connection terminal on an upper portion parallel to the substrate 10 in a state where the device surface is vertically mounted on the substrate 10, as shown. Since it is provided, the terminal and the conductor connection of the ASIC drive element 12 can be easily performed by the above-described normal vertically movable wire bonding process. A more detailed structure of the z-axis thin film fluxgate element 16 'and a manufacturing process thereof will be described in detail with reference to FIGS. 5 to 12.

FIG. 5 illustrates a state in which a plurality of z-axis thin film fluxgate elements 16 'are fabricated through an etching process and a thin film manufacturing process on an upper surface of the silicon wafer 24. An electrical terminal 20 for carrying out is provided together. On the other hand, the insulating thin film 26 is formed in the form of an oxide film such as Si0 _2, and serves to prevent a short circuit between the thin film element and the electrical terminals.

FIG. 6 illustrates a state in which the grooves 28 are formed on the upper surface of the silicon wafer 24 on which the plurality of z-axis thin film fluxgate elements 16 'are fabricated by a dicing process.

This dicing process utilizes a dicing saw to form grooves 28 in parallel along the distal ends of the electrical terminals 20 arranged horizontally. Accordingly, the grooving vertical portion 30 corresponding to the sidewall portion of the groove 28 is substantially perpendicular to the wafer surface on which the thin film element is formed. This grooving is ultimately performed by forming a wide insulating film on the portion where the electrical terminal 20 on the upper surface of the wafer is located, and then forming a conductive thin film connected to the terminal of the thin film element on the insulating film. This is for forming the connecting terminal extending from the electrical terminal 20 of the thin film element in the grooved vertical portion 30.

On the other hand, the grooves 28 formed by the dicing process can reach a part of the wafer 24 region through the insulating thin film 26 as shown, so that a short circuit between the connection terminals may occur due to the conductive wafer region. Can be. Therefore, before forming the connection terminal extending from the electrical terminal 20 of the thin film element in the grooved vertical portion 30, an insulating thin film having a wider width than the connection terminal in the portion where the connection terminal is to be formed as described above. It is preferable to form

FIG. 7 illustrates a z-axis thin film fluxgate device of a unit device in a state where groove processing is completed. The above-described dicing process and the subsequent process may be performed collectively for a plurality of thin film elements at the wafer level, but for the convenience of description, the subsequent subsequent processes will be described based on the unit elements.

FIG. 8 illustrates a state in which a photoresist coating film 32 for forming an insulating thin film is formed on a grooved z-axis thin film fluxgate element.

The photoresist is applied to the upper surface of the wafer in the state where the above-described groove processing is completed, and the insulating thin film forming portion 34 extending from the end side of each electrical terminal 20 to the bottom of the groove via the groove processing vertical portion 30 is selectively selected. By exposing to and developing, the photoresist coating film 32 is formed in the state which the photoresist structure of the insulating thin film formation part was removed as shown. At this time, the insulating thin film forming portion 34 is designed to be wider than the width of the connecting terminal to be described later, preferably in contact with the distal end of the electrical terminal 20.

FIG. 9 shows a state in which the insulating thin film 36 is formed and the above-described photoresist coating film is removed following the photoresist process of FIG. 8.

After the insulating thin film is formed on the entire surface of the wafer on which the photoresist coating film is formed by the photoresist process of FIG. 8, ultrasonic cleaning is performed by putting in an organic solvent such as acetone. Accordingly, the insulating thin film 36 is formed only in the portion where the photoresist does not exist (34 in FIG. 8), and the insulating thin film formed on the photoresist coating film (32 in FIG. 8) is neatly removed after the ultrasonic cleaning. That is, as shown, the insulating thin film 36 has a predetermined width extending from the distal end of each electrical terminal 20 of the thin film element to the bottom of the groove along the side wall of the groove, the electrical terminal 20 is All or at least part of the insulating thin film 36 is not exposed to the entire surface.

FIG. 10 shows a state in which a secondary photoresist coating film 38 is formed in order to form a conductive thin film in the vertical grooved portion.

As shown in the drawing, the secondary photoresist coating film 38 has a narrower width than that of the insulating thin film on the electrical terminal 20 and the insulating thin film 36 by the photoresist coating, exposure, and developing processes as described above. The mask region is exposed.

FIG. 11 illustrates a state in which the conductive thin film 40 is formed following the secondary photoresist process of FIG. 10 and the above-described secondary photoresist coating film is removed.

A conductive thin film 40 made of, for example, aluminum (Al), copper (Cu), or the like is formed on the secondary photoresist coating film of FIG. 10, and the secondary photoresist coating film is removed as described above. Accordingly, the conductive thin film 40 is electrically connected to the electrical terminal (20 in FIG. 10) exposed to the top surface of the silicon wafer in FIG. 10, and extends at least to the grooved vertical portion 30 along the insulating thin film 36. do. In this case, the conductive thin film 40 may be formed to be narrower than the width of the insulating thin film 36 to prevent a short circuit caused by the conductive thin film 40 and the silicon wafer. Preferably, the wire bonding is performed in the grooved vertical portion 30. In order to enable this, the film can be formed to have the same width as the electrical terminal (20 in FIG. 10) of the thin film element.

According to the method described above, the conductive thin film 40 formed on the grooving vertical part 30 is disposed horizontally toward the front when the z-axis thin film fluxgate element is rotated 90 degrees, and is wire-bonded with the terminal of the ASIC driving element. It functions as a connection terminal.

FIG. 12 illustrates a process of cutting the z-axis thin film fluxgate element on a wafer for each element after the formation of the conductive thin film of FIG. 11.

As shown, the z-axis thin film fluxgate element is cut close to the grooving vertical portion 30 along the longitudinal direction of the groove so that only the grooving vertical portion 30 remains. Further, by cutting the other surface of the element body, it is possible to finally obtain each unit element body.

FIG. 13 is a side view illustrating a state in which the z-axis thin film fluxgate element is die-bonded onto the electronic compass PCB substrate 10 following the above-described manufacturing process of the z-axis thin film fluxgate element.

As shown, the z-axis thin film fluxgate element 16 'has a device surface mounted perpendicular to the electronic compass PCB substrate 10, and the grooved vertical portion 30 is horizontally upwards (front) on the substrate. It is arranged to be. That is, the connection terminal 42 extended from the electrical terminal of the thin film element is horizontal with the substrate in the grooved vertical portion 30. On the other hand, the ASIC drive element 18 and the thin film fluxgate element (not shown) for the x-axis and y-axis are arranged so that the surface on which the thin film element is formed is horizontal in accordance with a conventional die bonding method.

14A illustrates a process of wire bonding the z-axis thin film fluxgate element 16 ′ and the ASIC drive element 18 attached to the substrate 10 following the die bonding of FIG. 13.

Referring to FIG. 14A, after the wire bonding tip 22 installed at the bonding head of the wire bonding machine first bonds the terminals of the ASIC drive element 18 (C position), the thin film fluxgate element 16 for the z-axis is then used. By secondary bonding the connection terminals of ') (position D), electrical connection is made between the two elements. It should be noted that since the terminals of the z-axis thin film fluxgate element 16 'and the ASIC drive element 18 face upwards, wire bonding is possible by a conventional vertically movable wire bonding machine.

FIG. 14B is a perspective view of wire bonding between terminals of the z-axis thin film fluxgate element 16 'and the ASIC driving element 18, and the substrate of FIG. 14A is omitted for convenience. As shown, the bonding surface (that is, the terminal surface) where wire bonding is made between the connection terminal of the z-axis thin film fluxgate element 16 'and the terminal of the ASIC drive element 18 is a thin film fluxgate element for the x and y axes. And the wire bonding surface of the ASIC driving element are parallel to the substrate.

Meanwhile, the thin film fluxgate device for the x and y axes and the ASIC driving device are wire bonded according to a conventional method, as shown in FIG. 4 described above. When the wire bonding is completed, packaging molding may be performed to mold the thin film fluxgate device for the x, y, and z axes and the ASIC driving device with an epoxy resin or the like as necessary.

Although the preferred embodiment according to the present invention has been described above, this is merely exemplary and those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Therefore, the protection scope of the present invention should be defined by the following claims.

As described above, according to the present invention, since the z-axis thin film fluxgate element includes a connection terminal extending from a terminal of the element surface and perpendicular to the element surface, the z-axis thin film fluxgate element and the ASIC drive element for driving the same There is an advantage in that each terminal can be electrically coupled by a conventional vertically movable wire bonding process.

Claims (6)

A method of assembling a thin film fluxgate device for a vertical axis (z-axis) manufactured on a wafer on a substrate, A groove processing step of forming a groove along an electric terminal end of the z-axis thin film fluxgate element arranged on the wafer; Depositing a conductive thin film extending from the electrical terminal to the sidewall portion of the groove to form a connection terminal in the sidewall portion of the groove; Cutting the z-axis thin film fluxgate element having the connection terminal formed on the sidewall of the groove for each unit element; Die bonding the cut z-axis thin film fluxgate element to a substrate such that a connection terminal of the z-axis thin film fluxgate element faces upward on the substrate; Die bonding a driving element for driving the z-axis thin film fluxgate element to the substrate; Wire bonding a connection terminal of the z-axis thin film fluxgate element bonded to the substrate and an electrical terminal of the driving element; Assembly method of a thin film fluxgate device for z-axis comprising a. The method of claim 1, wherein the groove processing step And forming grooves in parallel with the distal ends of the electrical terminals arranged horizontally on the wafer. The method of claim 1, wherein the forming of the connection terminal comprises: Depositing an insulating thin film extending from the distal side of the electrical terminal to the side wall of the groove; Depositing the conductive thin film electrically connected to the electrical terminal and extending from the insulating thin film to the sidewall portion of the groove Assembly method of a thin film fluxgate device for z-axis comprising a. The method of claim 3, wherein the conductive thin film deposition step A method of assembling a thin film fluxgate element for z-axis, wherein the conductive thin film is formed into a narrower width than the insulating thin film. A thin film fluxgate device for a vertical axis (z-axis) having a thin film element and an electrical terminal formed on an element surface, and having a connection terminal perpendicular to the element surface. An insulating thin film extending from a distal end of an electrical terminal arranged on an element surface to a side wall portion perpendicular to the element surface; A connection terminal electrically connected to the electrical terminal and formed on the insulating thin film to the sidewall portion with a narrower width than the insulating thin film; Thin film fluxgate device for z-axis comprising a. A three-axis measurement electronic compass in which thin film fluxgate elements and driving elements for x, y, and z axes are assembled on a substrate, The z-axis thin film fluxgate device, An insulating thin film extending from a distal end of an electrical terminal arranged on an element surface to a side wall portion perpendicular to the element surface; A connection terminal electrically connected to the electrical terminal and formed on the insulating thin film to the sidewall portion with a narrower width than the insulating thin film; To include, The electronic compass, Side-wall portions of the z-axis thin film fluxgate elements are die bonded upward on the substrate, Bonding surface of the x, y, z axis thin film fluxgate element and the terminal of the drive element is a bonding surface parallel to the substrate Electronic compass for 3-axis measurement.

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