JP2017083332A - Detection element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a detection element capable of reducing erroneous detection.SOLUTION: A detection element includes: an insulation member; a plurality of first electrodes arranged on a first side of the insulation member and having a plurality of openings; a plurality of second electrodes arranged on a second side opposite to the first side of the insulation member and respectively arranged at a plurality of through holes of the insulation member; and a plurality of connection terminals connected to the plurality of second electrodes, respectively. The distance between a connection terminal and the first electrode is larger than that of the first electrode and the second electrode.SELECTED DRAWING: Figure 1

Description

The present invention relates to a detection element.

Research on gas electron amplification type radiation detectors using pixel-type electrodes is underway. The gas electron amplification type radiation detection apparatus has a feature that a large area and real-time imaging can be performed particularly in image imaging of a detection region, where radiation detection by a conventional detection apparatus is insufficient.

For the structure of the gas electron amplification type radiation detection apparatus, for example, Patent Documents 1 to 3 can be referred to.

Japanese Patent No. 3354551 Japanese Patent No. 4391391 Japanese Patent No. 3535045

In the conventional gas electron amplification type radiation detection apparatus, there has been a problem of erroneous detection that occurs when gas amplification occurs in a place other than the pixel electrode.

Accordingly, an object of the present invention is to provide a detection element that can reduce erroneous detection in a radiation detection apparatus.

According to an embodiment of the present invention, an insulating member, a plurality of first electrodes having a plurality of openings disposed on a first surface of the insulating member, and a side opposite to the first surface of the insulating member. A detection element comprising a plurality of second electrodes disposed on a second surface and respectively disposed in a plurality of through holes of the insulating member, and a plurality of connection terminals to which the plurality of second electrodes are respectively connected. Thus, a detection element is provided in which a distance between the connection terminal and the first electrode is larger than a distance between the first electrode and the second electrode.

The second electrodes may be arranged in a matrix.

Further, the connection terminal may be connected to an external circuit.

The distance between the connection terminal and the first electrode may be 400 μm or more.

According to an embodiment of the present invention, it is possible to provide a detection element with reduced false detection in a radiation detection apparatus.

It is a schematic block diagram of the detection element 100a of the radiation detection apparatus 100 of this invention which concerns on Embodiment 1. FIG. It is a figure which shows the principle of operation of the radiation detection apparatus 100 of this invention which concerns on Embodiment 1. FIG. It is the top view and sectional drawing of a part of detection element 100a of the present invention concerning Embodiment 1. It is a figure which shows the manufacturing process of the detection element 100a in Embodiment 1. FIG. It is a figure which shows the manufacturing process of the detection element 100a in Embodiment 1. FIG. It is the top view and sectional drawing of a part of detection element 100a of the present invention concerning Embodiment 2. It is the one part top view and sectional drawing of the detection element 100a of this invention which concern on Embodiment 3. FIG. It is a cross-sectional perspective view of the radiation detection apparatus (container module) 150 of the present invention according to Embodiment 4.

Hereinafter, the radiation detection apparatus and detection element of the present invention will be described in detail with reference to the drawings. The radiation detection apparatus and the detection element of the present invention are not limited to the following embodiments, and can be implemented with various modifications. In all the embodiments, the same components are described with the same reference numerals. In addition, the dimensional ratio in the drawing may be different from the actual ratio for convenience of explanation, or a part of the configuration may be omitted from the drawing.

(Background to the Invention)
In a radiation detection apparatus (hereinafter referred to as “conventional radiation detection apparatus”) as disclosed in Patent Document 2, a pixel-type electrode has a connection terminal provided on the outer periphery and an external circuit connected by wire bonding. ing.

In this conventional radiation detection apparatus, the anode electrode pattern 25 is connected to the lead wiring 27 on the surface layer through a via (through hole). As a result of repeated investigations by the present inventors, when the distance between the lead wiring 27 and the cathode electrode pattern 21 becomes smaller than the distance between the anode electrode 22 and the cathode electrode 21, discharge occurs here, and other than the pixel electrode. It has been found that there is a possibility of erroneous detection in which gas amplification occurs at a location.

Moreover, in this conventional radiation detection apparatus, since the lead wiring 27 is subjected to wire bonding, the surface may be plated with gold in order to ensure sufficient connection strength. When a discharge occurs in the lead wiring 27 plated with gold on the surface, gold is scattered and the anode electrode and the cathode electrode are electrically connected, so that the detection device may not function or erroneous detection may occur.

Therefore, as a result of intensive studies on the phenomenon described above, the present inventor has arrived at the present invention.

<First Embodiment>
The schematic block diagram of the detection element 100a of the radiation detection apparatus 100 of this invention based on this embodiment is shown in FIG. The radiation detection apparatus 100 of the present invention according to the embodiment includes a pixel electrode unit 101, a detection element 100a having a connection terminal unit 109 (109a and 109b), a drift electrode 110, and a chamber 111. The pixel electrode portion 101 and the connection terminal portion 109 (109a and 109b) are collectively referred to as a detection element 100a. The radiation detection apparatus 100 is also referred to as a container module 100.

The pixel electrode unit 101 of the radiation detection apparatus 100 according to the present embodiment includes an insulating member 102, a cathode electrode 104, an anode electrode 106, an anode electrode pattern 108, and a substrate 130.

A plurality of cathode electrodes 104 are arranged on the first surface of the insulating member 102. The cathode electrode 104 has a plurality of openings 105. Since the cathode electrode 104 is formed in a strip shape, it is also referred to as a cathode strip electrode.

The anode electrode 106 is disposed in a through-hole provided in the insulating member 102 from the second surface opposite to the first surface of the insulating member 102. In the present embodiment, the tip of the anode electrode 106 is exposed at each of the plurality of openings 105 of the cathode electrode 104. In this embodiment, the anode electrode 106 has a shape in which the tip is exposed in each of the openings 105, but has a shape in which the tip is not exposed in each of the openings 105 (the tip is the insulating member 102. And a shape that roughly matches the top surface (the top surface of the through hole), or a shape in which the tip is located inside the through hole of the insulating member 102.

A plurality of anode electrodes 106 arranged in a plurality of openings 105 of one cathode electrode 104 are connected to a plurality of anode electrode patterns 108, respectively. The anode electrode pattern 108 extends to the connection terminal portion 109a. The direction in which the cathode electrode 104 extends is substantially perpendicular to the direction in which the anode electrode pattern 108 extends. In the present embodiment, the anode electrode 106 and the anode electrode pattern 108 are separately provided and electrically connected to each other. However, the present invention is not limited to this. 106 and the anode electrode pattern 108 to which each anode electrode 106 is connected may be integrally formed. Since the anode electrode pattern 108 is formed in a strip shape, it is also referred to as an anode strip pattern.

The cathode electrode 104 may be referred to as a first electrode, the anode electrode 106 may be referred to as a second electrode, and drift may be referred to as a third electrode.

The wiring terminal portion 109 a includes a via 126 connected to the anode electrode pattern 108, a first metal layer 120, a second metal layer 122, and a third metal layer 124. The first metal layer 120, the second metal layer 122, and the third metal layer 124 are stacked, and the third metal layer 124 is connected to the via 126. In the present embodiment, an example is shown in which the third metal layer 124 and the via 126 are formed separately, but they may be formed integrally. In the present embodiment, the anode electrode pattern 108 and the via 126 are formed separately. However, the present invention is not limited to this, and the anode electrode pattern 108 and the via 126 are formed of the same metal material. May be. In the present embodiment, the example in which the first metal layer 120 and the second metal layer 122 are stacked and disposed has been described. However, the present invention is not limited to this, and the second metal layer 122 is not limited thereto. The first metal layer 120 may be disposed on the via 126 (or on the third metal layer 124) and connected.

The wiring terminal portion 109b has an electrode 104a on which the cathode electrode 104 is extended.

A voltage is applied between the cathode electrode 104 and the anode electrode 106 to form an electric field.

The radiation detection apparatus 100 of the present invention according to this embodiment has a configuration in which the anode electrodes 106 are arranged in a matrix in the pixel electrode unit 101 by adopting the configuration as described above. In the radiation detection apparatus 100 of the present invention according to this embodiment, a plurality of “pixels” including the anode electrode 106 and a part of the cathode electrode 104 are arranged.

110 is a drift electrode. The cathode electrode 104 is connected to GND, and a voltage is applied between the drift electrode 110 and the cathode electrode 104 to form an electric field.

A chamber 111 surrounds the pixel electrode portion 101, the connection terminal portion 109, and the drift electrode 110, and a mixed gas of a rare gas such as argon or xenon and a molecular gas such as ethane or methane exists therein.

Here, the operation principle of the radiation detection apparatus 100 of the present invention according to this embodiment is shown in FIG. In the radiation detection apparatus 100 of the present invention according to this embodiment, electrons generated by the interaction with a gas in which incident radiation exists due to the influence of an electric field generated between the drift electrode 110 and the cathode electrode 104. Forms an electron cloud and is attracted to the pixel electrode portion 101. At this time, the attracted electrons collide with gas atoms and ionize the gas atoms. Furthermore, the ionized electrons multiply like an avalanche, and the group of electrons collected by the anode electrode 106 reaches a level where it can be read out as an electric signal. Then, this electric signal can be read out from the connection terminal portion 109 a through the anode electrode pattern 108. On the other hand, positive charges induced in the electron group are generated in the cathode electrode 104, and an electric signal obtained therefrom can be read out from the connection terminal portion 109b. By measuring these electrical signals in time series, the track of the charged particles can be measured.

Next, a plan view and a cross-sectional view of a part of the detection element 100a of the present invention according to the present embodiment are shown in FIG. FIG. 3B shows a plan view of the pixel electrode portion 101 and the connection terminal portion 109a of the detection element 100a of the present invention according to this embodiment, and FIG. 3A shows the A of FIG. FIG. 10 is a cross-sectional view of the pixel electrode portion 101 and the connection terminal portion 109a taken along line -A ′.

As shown in FIG. 3A, the connection terminal portion 109a of the detection element 100a according to the present embodiment includes the first metal layer 120, the second metal layer 122, the third metal layer 124, and the via 126. have. In the present embodiment, gold is used for the first metal layer and nickel is used for the second metal layer 122. In the present embodiment, copper is used for the via 126, but the present invention is not limited to this. The second metal layer 122 (nickel) interposed between the first metal layer (gold) and the via 126 (copper) is connected to a bonding wire connected to an external circuit on the first metal layer. At this time, gold on the surface is prevented from diffusing into copper and hindering bonding, and has a role of ensuring hardness necessary for bonding. Further, nickel of the second metal layer 122 has a function of a low diffusion coefficient and high hardness. In the present embodiment, the connection terminal portion 109 a is electrically connected to the anode electrode pattern 108 through the via 126. In the present embodiment, the anode electrode pattern 108, the via 126, and the third metal layer 124 are shown as examples formed by different members. However, the anode electrode pattern 108, the via 126, and the third metal layer 124 are illustrated as examples. The metal layer 124 may be integrally formed. The second metal layer 122 may have a stacked structure of nickel and palladium. Further, aluminum or silver may be used for the first metal layer 120.

In the connection terminal portion 109a of the detection element 100a of the present invention according to this embodiment, the first metal layer 120, the second metal layer 122, the third metal layer 124, the pixel electrode (the cathode electrode 104 and the anode electrode 106). ) Are metal layers that satisfy the following conditions (1) to (3), respectively.

Third metal layer = material constituting pixel electrode (1)
Melting point of first metal layer 120 <melting point of third metal layer 124 <melting point of second metal layer 122 (2)
Ionization tendency of the first metal layer 120 <Ionization tendency of the third metal layer 124 <Ionization tendency of the second metal layer (easily oxidized) (3)

The second metal layer is disposed between the first metal layer and the third metal layer, and plays a role of preventing diffusion of metal from the first metal layer to the third metal layer.

The first metal layer 120 is preferably made of a metal material different from that of the anode electrode 106 and the cathode electrode 104.

In this embodiment, gold is used for the first metal layer 120 disposed in the wiring terminal portion 109a, and copper (which may be copper oxide) having a melting point higher than that of gold is used for the cathode electrode 104 and the anode electrode 106. Used. The melting point of gold is 1064 ° C., whereas the melting point of copper (copper oxide) is 1326 ° C. In this embodiment, the copper constituting the cathode electrode 104 and the anode electrode 106 is oxidized by the heat treatment of the sealing resin after wire bonding, and the surface becomes copper oxide. Therefore, the pixel electrode (cathode electrode 104 and anode electrode 106) is formed of a metal material having a melting point higher than that of the metal material of the first metal layer 120 of the wiring terminal portion 109a, whereby the cathode electrode 104 and the anode electrode 106 are formed. It is possible to prevent the metal from scattering when a discharge occurs in the meantime. In the present embodiment, the oxide film thickness of copper oxide is preferably 10 nm or less.

By adopting such a configuration, metal scattering due to the occurrence of discharge is prevented during the operation of the radiation detection apparatus 100 that applies a high voltage between the cathode electrode 104 and the anode electrode 106, and the cathode electrode 104. And the anode electrode 106 can be prevented from conducting.

Next, a manufacturing process of the detection element 100a of the present invention in the present embodiment will be described with reference to FIG. FIG. 4 shows a cross-sectional view of the detection element 100a of the present invention in this embodiment.

As shown in FIG. 4A, in addition to the third metal layer 124, the anode electrode pattern 108, the anode electrode 106, the cathode electrode 104, and the third metal layer 124 arranged on the substrate 130 are arranged. A resist mask 140 is formed (FIG. 4B). Then, by forming nickel plating, the second metal layer 122 made of nickel is formed only on the connection terminal portion 109a (FIG. 4C). Thereafter, gold plating is formed on the second metal layer 122 made of nickel, thereby forming the first metal layer 120 made of gold. Then, by removing the resist mask 140, the first electrode 120 made of gold is disposed only on the connection terminal portion 109a (FIG. 4D). Thereafter, the wire bonding 132 is connected onto the first metal layer 120 (FIG. 4E).

Further, as another aspect of the detection element 100a in the present embodiment, as shown in FIG. 5, the melting point of the copper cathode electrode 104, the anode electrode 106, and the third metal layer 124 is higher than that of the first electrode 120 to be formed later. The second metal layer 122 having a high height is formed. In this embodiment, nickel by electroless plating is used for the second metal layer. Thereby, nickel (melting point 1455 degreeC) whose melting | fusing point is higher than copper (copper oxide) is formed in the surface of each electrode, and it can improve discharge resistance. In addition to nickel, tungsten (melting point: 3422 ° C.), tantalum (3020 ° C.), molybdenum (2623 ° C.), or the like may be used. The subsequent processes (FIGS. 5B to 5D are the same as the processes described in FIGS. 4B to 4E).

(Embodiment 2)
FIG. 6 shows a plan view and a sectional view of a part of the detection element 100a of the present invention according to this embodiment. FIG. 6B shows a plan view of the pixel electrode portion 101 and the connection terminal portion 109a of the detection element 100a of the present invention according to this embodiment, and FIG. 6A shows A in FIG. FIG. 10 is a cross-sectional view of the pixel electrode portion 101 and the connection terminal portion 109a taken along line -A ′. Since this embodiment has the same configuration as that of the first embodiment, the same configuration will not be described again.

In the present embodiment, the distance X between the connection terminal portion 109a connected to the external circuit and the cathode electrode 104 adjacent to the connection terminal portion 109a, and the cathode electrode 104 and the anode electrode 106 disposed in the opening 105 thereof. The relationship with the distance Y satisfies the following condition (4).
X> Y (4)

By satisfying such condition (4), it is possible to prevent discharge from occurring in the connection terminal portion 109a other than the pixel electrode portion 101 where the anode electrode 106 and the cathode electrode 104 are located, and to prevent erroneous detection. Can do.

Here, the distance X between the connection terminal portion 109a connected to the external circuit and the cathode electrode 104 adjacent to the connection terminal portion 109a, and the distance Y between the cathode electrode 104 and the anode electrode 106 disposed in the opening 105 thereof, Table 1 below shows an example in which the discharge resistance characteristics of the detection element 100a of the present invention were verified by changing the above. The applied voltage between the anode electrode 106 and the cathode electrode 104 was 600 V, and the pixel pitch Z was 400 μm.

In Table 1, the meanings of “◎”, “◯”, “×”, and “xxx” are as follows.
A: There is no erroneous detection at the connection terminal portion 109a and the cathode electrode 104, metal scattering of the first metal layer 120 can be prevented, and the operation of the detection element 100a according to the present embodiment is good.
◯: There is no erroneous detection at the connection terminal portion 109a and the cathode electrode 104, and the operation of the detection element 100a according to the present embodiment is good.
X: An erroneous detection (including the occurrence of noise) occurs, and the detection element 100a according to the present embodiment does not function.
XX: Discharge occurs frequently at the connection terminal portion 109a and the cathode electrode 104, and the detection element 100a according to the present embodiment does not function.

The erroneous detection is determined when an abnormal signal is generated at the cathode electrode 104 along the connection terminal portion 109a. That is, as a result of the measurement, it can be seen that a signal unrelated to the obtained electron track is obtained from a location related to the cathode electrode 104 in the vicinity of the connection terminal portion 109a.

The discharge can be seen by measuring the leakage current flowing between the anode electrode 106 and the cathode electrode 104 at a value exceeding 10 nA. Normally, the leakage current is 1 nA or less, but exceeds 10 nA when discharge occurs.

The scattering of the metal causes the anode electrode 106 and the cathode electrode 104 to become conductive due to electric discharge, and when the detection element 100a of the present invention according to the present embodiment stops operating, by observing the surface with a microscope, Can be confirmed.

According to the results shown in Table 1, when the pixel pitch Z is 400 μm or more, the distance X between the connection terminal portion 109a connected to the external circuit and the cathode electrode 104 adjacent to the connection terminal portion 109a is set to 400 μm or more. In addition, there is no false detection at the connection terminal portion 109a and the cathode electrode 104, and not only can the metal scattering of the first metal layer 120 be prevented, but also high bonding connection reliability can be ensured. Therefore, the operation of the detection element 100a of the present invention according to this embodiment can be improved.

In the detection element 100a of the present invention according to this embodiment, since a high voltage is applied between the anode electrode 106 and the cathode electrode 104, the distance Y between the anode electrode 106 and the cathode electrode 104 is equal to that of the present invention. The performance of the radiation detection apparatus 100 is affected. When the distance Y is large, discharge is less likely to occur, but the gas amplification factor decreases, so the performance of the radiation detection apparatus 100 of the present invention is degraded. On the contrary, if the distance Y is small, discharge is likely to occur, but the gas amplification factor is improved, so that the performance of the radiation detection apparatus 100 of the present invention is improved. Therefore, the distance Y between the anode electrode 106 and the cathode electrode 104 is set to about 95 μm in this embodiment based on the trade-off relationship between discharge and gas amplification factor.

However, when the distance Y is set to about 95 μm, when a large amount of radiation is irradiated locally, a discharge occurs, and the metal constituting the anode electrode 106 and the cathode electrode 104 is melted and scattered by the heat generated by the discharge. There has been a problem in that radiation detection cannot be continued due to conduction between the electrodes.

In order to solve this problem, it was found that scattering was eliminated by preheating the pixel electrode to oxidize the copper surface. This is because the surface of pure copper having a melting point of 1085 ° C., which is a metal of the pixel electrode, becomes copper oxide having a melting point of 1326 ° C. and is difficult to melt.

On the other hand, the connection terminal 109a provided around the pixel electrode may be connected to an external circuit by bonding using a gold wire that can support multi-pin narrow pitch connection. When the metal surface constituting the connection terminal 109a is oxidized, the bonding strength of wire bonding deteriorates. Therefore, in this embodiment, the metal surface of the connection terminal 109a is plated with gold and the first metal layer 120 is disposed. did. Since gold has the smallest ionization tendency and is not easily oxidized, wire bonding with good bonding strength can be performed regardless of the storage state of the pixel electrode. In the gold plating, a nickel layer of the second metal layer 124 serving as a base is formed on copper by electroless plating, and is formed on the nickel layer by electroless plating. Nickel intervening between gold and copper functions as a diffusion preventing film, has a role of preventing gold from diffusing into copper and disappearing of gold, and ensuring hardness required for bonding.

The same high voltage as that between the anode electrode 106 and the cathode electrode 104 is also applied between the connection terminal 109 a to the external circuit and the cathode electrode 104. In a state where the distance X between the connection terminal 109a to the external circuit 109 and the cathode electrode 104 is equal to or less than the distance Y between the anode electrode 106 and the cathode electrode 104, gas amplification occurs in a place other than the pixel electrode portion 101, Misdetection that causes noise occurs. Therefore, the distance X must be larger than the distance Y.

Gold plating, which is the first metal layer 120 on the metal surface of the connection terminal 109a, has a melting point of 1064 ° C., which is lower than that of pure copper, and is melted and scattered by heat generated by discharge, and between the adjacent cathode electrode 104 and the anode electrode There is a possibility of causing a problem that the radiation detection cannot be continued due to conduction between 106 and the cathode electrode 104. In this embodiment, the distance X between the connection terminal 109a to the external circuit 109 and the cathode electrode 104 is ensured to be 400 μm or more, and the metal surface of the connection terminal 109a is plated with gold so that false detection and metal scattering can be achieved. In addition to preventing this, there is an excellent effect that connection reliability with an external circuit can be ensured.

(Embodiment 3)
FIG. 7 shows a plan view and a sectional view of a part of the detection element 100a of the present invention according to this embodiment. FIG. 7B shows a plan view of the pixel electrode portion 101 and the connection terminal portion 109a of the detection element 100a of the present invention according to this embodiment, and FIG. 7A shows the A of FIG. FIG. 10 is a cross-sectional view of the pixel electrode portion 101 and the connection terminal portion 109a taken along line -A ′. In the present embodiment, except for the configuration of the connection terminal portion 109a, the configuration is the same as that of the first and second embodiments, and therefore the same configuration will not be described again.

As shown in FIG. 7, in the present embodiment, the first metal layer 120 of the connection terminal portion 109a is not disposed on the entire surface of the connection terminal portion 109a, and a part on the outer end side of the connection terminal portion 109a. It has the structure arrange | positioned only in. This is because the first metal layer 120 of the connection terminal portion 109a is formed in a part of the connection terminal portion 109a by changing the arrangement of the resist 140 in FIG. 4B described in the first embodiment. it can. In the present embodiment, gold is used for the first metal layer 120 as in the first embodiment.

By adopting such a configuration, even when a discharge occurs between the connection terminal portion 109a and the cathode electrode 104 adjacent to the connection terminal portion 109a, the metal of the first metal layer 120 is scattered. Can be prevented, and the problem that peripheral pixel electrode portions cannot be used can be further reduced. As a result, the distance X between the connection terminal portion 109a and the cathode electrode 104 adjacent to the connection terminal portion 109a can be set further smaller.

(Embodiment 4)
In the present embodiment, another example of the detection element 100a of the present invention will be described. Since the configuration is the same as that of the first, second, and third embodiments, the same configuration will not be described again.

FIG. 8 is a cross-sectional perspective view of the radiation detection apparatus 150 of the present invention according to this embodiment. As in the first to third embodiments, the radiation detection apparatus 150 of the present invention according to the present embodiment includes the detection element 100a (pixel electrode unit 101, connection terminal unit 109 (109a and 109b)), drift electrode 110, and chamber 111. doing. Further, in the radiation detection apparatus 150 of the present invention according to the present embodiment, drift cages 152a and 152b are provided. The drift cages 152a and 152b are provided to make the electric field distribution between the drift electrode 110 and the pixel electrode portion 101 uniform.

DESCRIPTION OF SYMBOLS 100 Radiation detection apparatus 100a Detection element 101 Pixel electrode part 109 (109a and 109b) Connection terminal part 110 Drift electrode 111 Chamber 102 Insulating member 104 Cathode electrode 105 Opening part 106 Anode electrode 108 Anode electrode pattern 111 Chamber 120 1st metal layer 122 1st 2 metal layers 124 3rd metal layer 126 via 130 substrate 150 radiation detection device (container module)
152a, 152b Drift cage

Claims (4)

An insulating member;
A plurality of first electrodes having a plurality of openings disposed on the first surface of the insulating member;
A plurality of second electrodes disposed on a second surface of the insulating member opposite to the first surface and disposed in a plurality of through holes of the insulating member;
A plurality of connection terminals to which the plurality of second electrodes are respectively connected;
A sensing element comprising:
The distance between the connection terminal and the first electrode is larger than the distance between the first electrode and the second electrode. The detection element according to claim 1, wherein the second electrodes are arranged in a matrix. The detection element according to claim 1, wherein the connection terminal is connected to an external circuit. 4. The detection element according to claim 1, wherein a distance between the connection terminal and the first electrode is 400 μm or more. 5.

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