JP4391391B2 - Manufacturing method of radiation detector - Google Patents

Description

  The present invention relates to a method of manufacturing a radiation detector used for detecting an incident position of radiation such as X-rays and γ-rays.

  Conventionally, as a radiation detector for detecting a radiation incident position, a plurality of through holes are formed in a cathode electrode (cathode) made of copper foil in an airtight case provided with a radiation transmission window. A substrate having a structure in which a pixel having a structure in which an anode electrode (anode) is disposed in the center with an insulating gap interposed therebetween is disposed and a rare gas or the like is enclosed therein is known.

  This radiation detector is installed and used at a position where radiation is expected to be incident, and detects that a rare gas in the passage path is ionized by the incidence of radiation and a current flows between electrodes of neighboring pixels, The incident radiation and the incident direction are detected.

Conventionally, the substrate of such a radiation detector was manufactured by the method shown below (refer patent document 1).
First, as shown in FIG. 6 (a), the copper foil 4a on the side that becomes the inner layer of the double-sided copper-clad plate 3 in which the interlayer connection part 2 by the silver paste bumps is formed through the synthetic resin sheet 1 A predetermined wiring pattern 5 is formed by a photolithography technique, and a substrate 8 in which a support substrate 7 made of polyimide is laminated and integrated thereon via a prepreg 6 is manufactured.

Next, as shown in FIG. 6 (b), a hole 9 is formed in the anode electrode formation position of the copper foil 4b on the other side of the double-sided copper-clad plate 3 by a photolithography technique to expose the synthetic resin sheet 1. .
As shown in FIG. 6 (c), a carbon dioxide laser 10 is irradiated from above the copper foil 4b in which the hole 9 is formed at the anode electrode formation position to form a through hole 11 reaching the wiring pattern 5 in the synthetic resin sheet 1. To do.

  Subsequently, the copper foil 4b is patterned to form the cathode electrode 12 and the lead wiring 13 as shown in FIG. Here, the lead wiring 13 is a connection terminal for connecting the anode electrode 15 to the outside of the radiation detector via the wiring pattern 5 and the interlayer connection portion 2.

  Next, as shown in FIG. 6 (e), a plating resist 14 is formed on the cathode electrode 12, and as shown in FIG. 6 (f), the through-hole 11 is filled with copper by electroplating to form the anode electrode 15 Form.

  Thereafter, when the plating resist 14 is removed, as shown in FIG. 6G, a substrate for a radiation detector in which the cathode electrode 12 surrounds the anode electrode 15 is obtained. The cathode electrode 12 is also connected to another lead wiring not shown.

JP 2002-90465 A

However, such a conventional manufacturing method has the following problems.
That is, when the copper filled in the through-hole 11 in the step of forming the anode electrode 15 reaches the substrate surface, the plating rate is rapidly increased. Therefore, a protrusion 15a is formed at the tip of the anode electrode 15, and this protrusion Discharge occurs between 15a and the cathode electrode 12 (FIG. 7A). When such a discharge occurs, a large current flows between the electrodes, causing the problem that the electrode is cut by the generated heat, or fragments scattered during the discharge adhere to the surface of the insulating layer exposed on the substrate surface. .

  Further, since the through-hole 11 is filled with copper after the plating resist is formed, the bottom of the through-hole 11 becomes deeper by the thickness of the plating resist, and it becomes difficult for copper to reach the bottom of the through-hole 11 partially. The height of the anode electrode 15 varies (FIG. 7B).

  To solve such a problem, the through hole 11 is directly filled with copper by electroplating without forming a plating resist. However, with this method, the anode 15 and the cathode are filled with copper to fill the substrate surface. This causes a short circuit with the electrode 12 (FIG. 7C).

  In addition, it is conceivable that the filling of copper by electroplating does not reach the substrate surface but halfway through the through-hole 11, but in this method, the tip of the anode electrode 15 does not reach the substrate surface, so the cathode electrode A dead space where no electric field is applied to 12 is generated, and the radiation incident position cannot be detected (FIG. 7 (d)).

  The present invention has been made to solve such a problem, and the radiation detector in which the height of the formed anode electrode reaches the surface of the substrate uniformly and no protrusion is formed at the tip of the electrode. It aims at providing the manufacturing method of.

  The manufacturing method of the radiation detector of this invention WHEREIN: The process of forming a predetermined wiring pattern in the said 1st conductor layer of the 2 layer board | substrate which has a 1st conductor layer and a 2nd conductor layer, A step of forming an opening corresponding to the anode electrode in the second conductor layer, and irradiating the second conductor layer of the two-layer substrate with a high energy beam, and wiring of the first conductor layer at the position of the opening Forming a through-hole reaching a pattern, filling the through-hole with metal by metal plating, and further forming a metal plating layer on the filled through-hole and the second conductor layer by the metal plating; A step of removing the formed metal plating layer and the second conductor layer to a predetermined thickness, and an anode protruding from the through hole by patterning the second conductor layer removed to the predetermined thickness Electrode and anode electrode Characterized by a step of forming a cathode electrode surrounding.

  In the step of forming the opening, an opening corresponding to the interlayer connection portion is formed together with the opening corresponding to the anode electrode, and in the step of forming the through hole, the wiring pattern of the first conductor layer is reached at these opening positions. A through hole may be formed.

  In the present invention, after a predetermined wiring pattern is formed on the first conductor layer of the two-layer board, the two-layer board is bonded to the support substrate with the wiring pattern inside, and thereafter You may make it perform a process.

  The surface roughness of the roughened surface of the copper foil used for the second conductor layer is preferably Rz = 2.0 μm or less. By using a copper foil having such a surface roughness, it becomes difficult to generate discharge because the unevenness of the exposed insulating material surface between the anode electrode and the cathode electrode is suppressed, and a high voltage can be applied between the electrodes. It becomes possible.

  According to the present invention, the heights of the formed anode electrodes are almost equal from the surface of the substrate, respectively, and no protrusion is formed at the tip of the electrode, so that a high voltage can be applied between the electrodes, and the reliability of the electrode portion can be improved. Improves.

  Further, by using a copper foil having a surface roughness Rz of 2.0 μm or less for the second conductor layer, it is possible to further improve the insulation characteristics.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a plan view showing a configuration of a substrate of a radiation detector manufactured by applying the embodiment of the present invention, and FIG. 2 is a cross-sectional view taken along line AA ′ of FIG.

  As shown in FIG. 1, the cathode electrode 21 is formed to have a circular opening centered on the anode electrode 22.

  On the other hand, as shown in FIG. 2, the anode electrode 22 is connected to a wiring pattern 25 arranged at a pitch of 300 μm and 400 μm via a polyimide prepreg 24 on a support substrate 23 made of polyimide, and a polyimide film 26 is connected. It is formed to penetrate.

  A lead wiring 27 is provided on the substrate surface, and the anode electrode 22 is connected to the lead wiring 27 via the wiring pattern 25 and the interlayer connection portion 28.

The radiation detector has a detection area of 10 cm × 10 cm. The width and pitch of the cathode and anode electrodes on the substrate of such a radiation detector are as follows.
Width of cathode electrode: 350 μm
Cathode electrode pitch: 400 μm
Anode electrode pitch: 400 μm in the vertical and horizontal directions
Number of anode electrodes: about 60,000 Spacing between cathode electrode and anode electrode: 70 to 150 μm

Next, the operation principle of the radiation detector of the present invention will be described.
Such a substrate is placed in a case sealed with a rare gas or the like, and a high voltage is applied between the anode electrode and the cathode electrode. When radiation is incident, a current is applied to any anode electrode and cathode electrode. The radiation incident position is detected by capturing the signal generated at that time.

  Next, the process of manufacturing the radiation detector shown in FIGS. 1 and 2 will be described with reference to FIG.

[First Embodiment]
FIG. 3 is a diagram for explaining the manufacturing method according to the first embodiment of the present invention.
First, an electrolytic copper foil 32a having a thickness of 18 μm and an electrolytic copper foil 32b having a surface roughness Rz = 1.9 μm and a thickness of 18 μm are laminated on a polyimide film 31 having a thickness of 100 μm, and silver paste bumps are used. A laminated board 34 having an interlayer connection 33 is prepared.

  A predetermined wiring pattern (32p) is formed on the copper foil 32a, which is the first conductor layer of the laminate, by a known photolithography technique. With the wiring pattern 32p on the inside, this laminate 34 is adhered to a support substrate 36 made of polyimide via a prepreg 35 to form a substrate 37 (FIG. 3A).

  When the substrate 37 is formed, a hole 38 having a diameter of 65 μm is formed by a known photolithography technique at the anode electrode formation position of the copper foil 32b as the second conductor layer (FIG. 3B), and this copper foil 32b. Is used as a mask to irradiate the carbon dioxide laser 39 to form a through hole 40 reaching the wiring pattern 32p (FIG. 3C).

  Next, a metal layer 41 made of copper having a thickness of 0.4 to 1 μm is deposited on the inside of the through hole 40 and on the copper foil 32b by electroless copper plating (FIG. 3D). Then, the inside of the through hole 40 is filled with copper by electroplating, and a conductive metal layer 42 made of copper of 15 to 40 μm is laminated on the through hole 40 filled with copper (FIG. 3E). In addition, although a plating solution has copper sulfate as a main component, in order to make copper precipitate easily, you may add a surface active agent.

  Subsequently, the metal layer 41 and the conductive metal layer 42 are removed by etching with a solvent mainly composed of hydrogen peroxide and sulfuric acid, and etching is further performed until the thickness of the copper foil 32b becomes 10 to 25 μm (FIG. 3 (f)).

  Next, after a resist 43 is applied to the lead wiring formation position and the cathode electrode formation position as shown in FIG. 3G, the cathode electrode 44, the lead wiring 45 and the anode electrode 46 are formed by etching, and FIG. ) Is obtained.

  According to the first embodiment, by using the copper foil 32b whose surface roughness Rz of the roughened surface is 2.0 μm or less for the second conductor layer, in the conventional manufacturing method, discharge occurs at the protruding portion. Therefore, it is possible to apply a high voltage of 750 to 1500 V, which was impossible.

Fig.4 (a) is the figure which expanded and showed the surface S of the polyimide film 31 of FIG.3 (h).
As shown to Fig.4 (a), the unevenness | corrugation of the roughening surface of the copper foil 32b is transcribe | transferred on the surface S of the polyimide film 31 after removing the copper foil 32b by an etching. Compared with the case where a copper foil having a roughened surface roughness Rz of 7.0 μm is used for the second conductor layer (FIG. 4B), the surface roughness of the copper foil is small. The unevenness transferred to the surface S is also reduced.

  That is, by using a copper foil having a roughened surface with a surface roughness Rz of 2.0 μm or less for the second conductor layer, it becomes difficult to accumulate charges by reducing the unevenness of the surface of the polyimide film 31. As a result, the insulation is improved and a high voltage can be applied.

  Furthermore, according to the first embodiment, there is no variation in the height of the anode electrode, and the occurrence of protrusions on the electrode can be suppressed.

  That is, since the copper foil 32b having a surface roughness Rz of 2.0 μm or less on the roughened surface is removed by etching, the electrode end adjacent to the polyimide film 31 to which the irregularities are transferred can be formed in a smooth shape. As a result, it is possible to prevent discharge from occurring even when a high voltage is applied.

[Second Embodiment]
FIG. 5 is a diagram for explaining the manufacturing method according to the second embodiment of the present invention.
First, a 0.8 mm thick double-sided copper-clad plate in which 18 μm thick copper foils 52 a and 52 b are laminated on both sides of the polyimide film 51 is prepared.

  A predetermined wiring pattern 52p is formed on the copper foil 52b of the double-sided copper-clad plate as the first conductor layer by a known photolithography technique, and the other copper foil 52a is removed by etching.

  Next, 100 μm thick polyimide prepregs 53a and 53b and 18 μm thick copper foils 54a and 54b having a surface roughness Rz of 1.9 μm are stacked on top and bottom of the double-sided copper-clad plates, A lamination press by pressurization is performed to form a substrate 55 (FIG. 5A).

  The copper foil 54a of the substrate 55 was removed by etching, and a hole 38 having a diameter of 65 μm was formed by a known photolithography technique at the anode electrode forming position and the interlayer connection forming position of the copper foil 54b as the second conductor layer. Thereafter (FIG. 5B), carbon dioxide laser 39 is irradiated using the copper foil 54b in which the hole 38 is formed as a mask to form a through hole 40 reaching the wiring pattern 52p (FIG. 5C).

  Subsequent steps are the same as those in the first embodiment as shown in FIGS. 5D to 5G, and the configuration shown in FIG. 5H is obtained.

  According to the second embodiment, since the interlayer connection portion is formed together with the anode electrode by metal plating, the work efficiency can be increased at low cost.

  According to the method for manufacturing a radiation detector of the present invention as described above, it is possible to apply a high voltage, which is impossible because a discharge occurs in the conventional manufacturing method. In other words, the height of the formed anode electrode reaches the substrate surface uniformly, and there is no protrusion at the tip of the electrode, so a high voltage is applied to the anode electrode and the cathode electrode, and the lines of electric force are applied to the anode electrode. Discharge does not occur even if it is concentrated.

  In addition, since a high voltage can be applied, a high gas amplification factor exceeding 10,000 can be obtained, and not only X-rays but also γ-ray incident positions can be detected.

  The radiation detector of the present invention can be suitably used in a wide range including medical diagnostic images, nuclear waste monitoring, industrial process monitoring, and space astronomy.

It is a top view of the radiation detector manufactured by this invention. It is sectional drawing of the radiation detector manufactured by this invention. It is a figure explaining the 1st Embodiment of this invention. It is the figure which expanded and showed the surface of the polyimide film. It is a figure explaining the 2nd Embodiment of this invention. It is a figure explaining the manufacturing method of the conventional radiation detector. It is a figure explaining the conventional radiation detector.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Synthetic resin sheet, 2 ... Interlayer connection part, 3 ... Double-sided copper clad board, 4a, 4b ... Copper foil, 5 ... Wiring pattern, 6 ... Pre-preg, 7 ... Support substrate, 8 ... Substrate, 9 ... Hole, 10 DESCRIPTION OF SYMBOLS ... Carbon dioxide laser, 11 ... Through-hole, 12 ... Cathode electrode, 13 ... Lead wiring, 14 ... Plating resist, 15 ... Anode electrode, 15a ... Projection, 21 ... Cathode electrode, 22 ... Anode electrode, 23 ... Support substrate, 24 ... polyimide prepreg, 25 ... wiring pattern, 26 ... polyimide film, 27 ... lead wiring, 28 ... interlayer connection, 31 ... polyimide film, 32a, 32b ... copper foil, 32p ... wiring pattern, 33 ... interlayer connection, 34 ... Two-layer substrate, 35 ... prepreg, 36 ... support substrate, 37 ... substrate, 38 ... hole, 39 ... carbon dioxide laser, 40 ... through-hole, 41 ... metal layer, 42 ... conductive metal layer, 4 DESCRIPTION OF SYMBOLS 3 ... Resist, 44 ... Cathode electrode, 45 ... Lead wiring, 46 ... Anode electrode, 51 ... Polyimide film, 52a, 52b ... Copper foil, 53a, 53b ... Polyimide prepreg, 54a, 54b ... Copper foil, 55 ... Substrate

Claims (4)

Forming a predetermined wiring pattern on the first conductor layer of the two-layer substrate having the first conductor layer and the second conductor layer;
Forming an opening corresponding to the anode electrode in the second conductor layer of the two-layer substrate;
Irradiating the second conductor layer of the two-layer substrate with a high energy beam to form a through hole reaching the wiring pattern of the first conductor layer at the position of the opening;
Filling the through hole with metal by metal plating, and further forming a metal plating layer on the filled through hole and the second conductor layer by the metal plating; and
Removing the formed metal plating layer and the second conductor layer to a predetermined thickness;
And a step of patterning the second conductor layer removed to the predetermined thickness to form an anode electrode protruding from the through hole and a cathode electrode surrounding the anode electrode. Manufacturing method.   The step of forming the metal plating layer includes a step of forming a metal layer by electroless plating on the through hole and the second conductor layer of the two-layer substrate, and filling the through hole with a conductive metal by electroplating. The method of manufacturing a radiation detector according to claim 1, further comprising a step of forming a conductive metal layer on the filled through hole and the second conductor layer by the electroplating.   The step of forming the opening is a step of forming an opening corresponding to the interlayer connection portion together with the opening corresponding to the anode electrode, and the step of forming the through hole corresponds to the opening corresponding to the anode electrode and the interlayer connection portion. The method of manufacturing a radiation detector according to claim 1, wherein the through hole is formed at a position of the opening to be formed.   4. The method of manufacturing a radiation detector according to claim 1, wherein the second conductor layer is made of a copper foil having a surface roughness Rz of 2.0 μm or less. 5.

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