JP5122935B2 - Manufacturing method of multilayer ceramic substrate for electronic component inspection jig - Google Patents

Description

  The present invention relates to a method for manufacturing a multilayer ceramic substrate for an electronic component inspection jig.

  2. Description of the Related Art Conventionally, in order to inspect the continuity and function of an IC (Integrated Circuit) which is one of electronic components, an IC inspection jig that performs inspection by bringing a probe into contact with each terminal of the IC has been used. As this type of IC inspection jig, a probe electrode is provided on one surface of a multilayer ceramic substrate, and an electrode electrically connected to the probe electrode through a via is provided on the other surface. It has been. The multilayer ceramic substrate is required to have high strength that can withstand repeated contact of the IC terminals and high dimensional accuracy that can reliably contact the IC terminals and the probe.

  Recently, there is a tendency that the size and interval of the IC terminals are reduced with the miniaturization of the IC. On the other hand, the size of the silicon wafer is increased, and recently, a 12-inch (about 300 mm) size wafer has appeared. Further, there is an increasing demand for IC inspection in units of silicon wafers that have been increased in size. For this reason, the characteristics required for the multilayer ceramic substrate are becoming more and more severe, and there is a demand for a multilayer ceramic substrate having high dimensional accuracy and high strength that can sufficiently cope with the miniaturization of ICs and the enlargement of wafers. Yes.

  In general, a multilayer ceramic substrate used for an IC inspection jig is manufactured by laminating a plurality of ceramic green sheets filled and coated with a conductive paste and firing them together. However, in such a method, since the shrinkage of each ceramic green sheet at the time of firing occurs, it is difficult to obtain the dimensional accuracy necessary for connection to the IC terminal.

  Therefore, in order to obtain higher dimensional accuracy, a manufacturing technique called a so-called non-shrinkage firing technique has been proposed (for example, see Patent Documents 1 and 2). In this technology, an unfired ceramic green sheet is laminated on a fired ceramic substrate, and then fired integrally. Therefore, it is considered that high dimensional accuracy can be obtained.

  However, these techniques have the following problems, although shrinkage in the XY direction of the ceramic green sheet laminated on the fired ceramic substrate is suppressed. That is, in the method described in Patent Document 1, firing is performed after forming a via hole in the first ceramic green sheet in the production of the fired ceramic substrate. For this reason, since the first ceramic green sheet is sintered while contracting in the XY direction, high dimensional accuracy cannot be obtained. As a result, even if the second ceramic green sheet is laminated on the obtained fired ceramic substrate and fired, the dimensional accuracy of the obtained substrate is not always sufficient. In Patent Document 2, there is no description of a method for forming a via hole in a fired ceramic substrate, and no reference is made to the dimensional accuracy of the fired ceramic substrate itself.

As described above, a technique for manufacturing a multilayer ceramic substrate having high strength and high dimensional accuracy as required recently has not yet been established.
JP 2002-344138 A JP 2003-158375 A

  The present invention has been made in response to the above problems of the prior art, and has high dimensional accuracy that can sufficiently cope with the miniaturization of electrode terminals of electronic components such as ICs and the enlargement of an assembly of electronic components such as wafers. It is an object of the present invention to provide a method capable of producing a multilayer ceramic substrate for an electronic component inspection jig having high strength.

(1) In the invention of claim 1 (a method for producing a multilayer ceramic substrate for an electronic component inspection jig), after firing a first ceramic green sheet at a first temperature to produce a first fired substrate, A step of forming a truncated cone-shaped first via hole in the first baked substrate, and then filling the first via hole with a conductive paste that can be baked at a second temperature lower than the first temperature ( a) and a first ceramic green sheet that can be fired at the second temperature or a laminate in which a plurality of the second ceramic green sheets are laminated, the first paste in which the conductive paste is filled (B) obtaining a composite laminate by laminating the fired substrate with the large-diameter side surface of the first via hole facing the second ceramic green sheet or the laminate; and Above And step (c) is fired at a second temperature, possess a (d) forming an electrode on the fired non-laminated surface of the first fired substrate of the composite laminate, the step (d ) Includes a step of polishing the non-stacked surface of the first baked substrate and a step of performing sputtering to form the electrode on the polished surface .

  In the present invention, since the first via hole is formed in the first baked substrate, the position and shape of the via hole have high dimensional accuracy. In addition, since the second ceramic green sheet is laminated and fired on the first fired substrate having a via hole with high dimensional accuracy in this way, the dimensional accuracy of the entire multilayer ceramic substrate obtained is also high. Furthermore, it becomes possible to use a low-resistance metal material such as Ag or Cu as the conductive paste filled in the first via hole formed on the first baked substrate, thereby improving inspection accuracy and reducing power consumption. Can be achieved.

  (2) The invention of claim 2 is characterized in that the first temperature is 1350 ° C. or higher and the second temperature is 800 to 1000 ° C.

  In the present invention, the first temperature for firing the first fired substrate and the second temperature for firing the composite laminate in which the second ceramic green sheet and the first fired substrate are laminated are exemplified. Yes, when the first temperature is 1350 ° C. or higher and the second temperature is 800 to 1000 ° C., the multilayer ceramic substrate for an IC inspection jig has high strength, high dimensional accuracy, and low via resistance. Can be obtained easily and reliably.

  (3) The invention of claim 3 is characterized in that, in the step (b), the conductive paste previously filled in the first fired substrate is fired.

  In the present invention, since the conductive paste filled in the first baked substrate is baked in advance, conductor pastes having different compositions and shrinkage behavior can be arranged on the first baked substrate. It becomes possible to arrange a conductor having high characteristics.

  (4) The invention of claim 4 is characterized in that the formation of the first via hole is performed by laser processing.

  In the present invention, the first via hole having a desired shape and size can be easily and economically formed at a desired position of the first baked substrate.

  (5) The invention of claim 5 is characterized in that the diameter of the first via hole is 30 μm or more and 100 μm or less.

  In the present invention, since the diameter of the first via hole is not less than 30 μm and not more than 100 μm, a via and a wiring pattern that can sufficiently cope with the miniaturization of the IC can be formed. If the diameter of the first via hole is less than 30 μm, a slight misalignment with the via provided in the lower layer may cause a connection failure, and it becomes difficult to fill the via hole with the conductor. Further, if the diameter of the first via hole exceeds 100 μm, it becomes difficult to form a fine electrode pattern, and it becomes impossible to sufficiently cope with the miniaturization of the IC.

  (6) The invention of claim 6 is characterized in that the thickness of the first baked substrate is 0.1 mm or more and 0.5 mm or less.

  In the present invention, since the thickness of the first baked substrate is 0.1 mm or more and 0.5 mm or less, the second ceramic green sheet or a laminate thereof can be easily laminated, and via holes can be formed. In particular, it is easy to form a via hole by laser processing. When the thickness of the first fired substrate is less than 0.1 mm, it is difficult to laminate the second ceramic green sheet or its laminate. If the thickness of the first baked substrate exceeds 0.5 mm, it becomes difficult to form a via hole having a desired size and shape.

  (7) The invention of claim 7 is characterized in that the conductive paste contains at least one selected from the group consisting of Ag, Cu, Au, Pd and Pt.

  In the present invention, since the conductive paste filled in the first via hole contains at least one selected from the group consisting of Ag, Cu, Au, Pd and Pt, the first fired substrate has a low resistance via. A conductor can be formed, thereby improving inspection accuracy and reducing power consumption.

  (8) In the invention of claim 8, in the step (b), there is provided a conductor paste that communicates with the first via hole formed in the first fired substrate and can be fired at the second temperature. A second ceramic green sheet having a filled second via hole is laminated.

  In the present invention, vias that are electrically and reliably connected to vias formed on the first fired substrate can be formed in the fired second ceramic green sheet.

  According to the present invention, a multilayer ceramic for an electronic component inspection jig having high dimensional accuracy and high strength that can sufficiently cope with miniaturization of terminal electrode patterns of IC (electronic components) and enlargement of wafers (electronic component assemblies). A substrate can be manufactured.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. Although the description will be made based on the drawings, the drawings are provided for illustration only, and the present invention is not limited to the drawings.

(First embodiment)
FIG. 1 is a cross-sectional view showing a process of a method for manufacturing a multilayer ceramic substrate for an electronic component (IC) inspection jig according to a first embodiment of the present invention.

First, as shown in FIG. 1A, a first ceramic green sheet 11 that can be fired at a first temperature is prepared. The first temperature is preferably 1350 ° C. or higher and more preferably 1350 to 1600 ° C. from the viewpoint of obtaining a substrate having high strength. Specifically, an alumina powder (average particle size of 3 μm, specific surface area of 1.0 m ² / g) is added with a solvent such as acrylic resin (binder), toluene, and a plasticizer such as DOP (dioctyl phthalate). After mixing to make a ceramic slurry, the first ceramic green sheet 11 is obtained by applying a doctor blade method to this slurry.

  Next, as shown in FIG. 1B, the first ceramic green sheet 11 is fired at a first temperature, specifically 1400 ° C., to obtain a first fired substrate 12. The thickness of the first fired substrate 12 is preferably 0.1 mm or more and 0.5 mm or less, and more preferably 0.15 mm or more and 0.3 mm or less. If the thickness is less than 0.1 mm, the strength becomes insufficient, and it becomes difficult to perform lamination with a second ceramic green sheet described later. On the other hand, if the thickness exceeds 0.5 mm, it becomes difficult to form a via hole described later.

Next, as shown in FIG. 1C, the first baked substrate 12 is irradiated with laser to form via holes (first via holes) 13 that are through holes. The via hole 13 can be formed by laser using a gas laser such as a CO ₂ laser or an excimer laser, or a solid laser such as a YAG laser or a YVO ₄ laser, but is not particularly limited thereto. In addition, blasting or drilling can be applied regardless of laser processing. However, in the blast processing, it is difficult to form the fine via hole 13, while in the drill processing, a large processing cost is required and it is not economical. From such a viewpoint, laser processing is preferable.

The diameter of the first via hole 13 is preferably 30 μm or more and 100 μm or less, more preferably 50 μm or more and 85 μm or less, as will be apparent from experiments described later. If the diameter of the first via hole 13 is less than 30 μm, the filling property of the conductive paste becomes poor, and there is a possibility that highly reliable electrical connection becomes difficult. Also, very high accuracy is required for alignment with vias and wiring layers formed in the second ceramic green sheet, which will be described later, and there is a possibility that electrical connection cannot be obtained with a slight misalignment. . In addition, when the diameter exceeds 100 μm, it becomes difficult to deal with a miniaturized IC.

  Next, as shown in FIG. 1D, the first via hole 13 is filled with a conductive paste 14 that can be fired at a second temperature lower than the first temperature, and then shown in FIG. As described above, the first fired substrate 12 filled with the conductive paste is heated, and the conductive paste 14 is fired to form a via (first via) 15. It is preferable that 2nd temperature is 800-1000 degreeC. Here, the “conductive paste that can be fired at a second temperature lower than the first temperature” means a conductive paste containing a metal powder having a melting point between the first temperature and the second temperature. Say. In the present invention, among those satisfying such conditions, low resistance metals such as Ag, Cu, etc., from the viewpoint of improving the inspection accuracy of the multilayer ceramic substrate for IC inspection jigs obtained and reducing power consumption, etc. It is preferable to use a conductive paste containing at least one selected from the group consisting of Au, Pd and Pt.

  Next, as shown in FIG. 1 (f), one or more (four in the example of the drawing) second temperature, preferably 800 to one surface of the first baked substrate 12. Second ceramic green sheets 16A to 16D that can be fired at a temperature of 1000 ° C. are stacked.

Specifically, a borosilicate glass powder (average particle size 3 μm, specific surface area 1.0 m ² / g) containing SiO ₂ , Al ₂ O ₃ and B ₂ O ₃ as main components, and alumina powder (average particle size) 3 μm, specific surface area 1.0 m ² / g) (weight ratio 1: 1 of both components) Add a solvent such as acrylic resin (binder), toluene, and plasticizer such as DOP (dioctyl phthalate) and mix thoroughly. Then, after making a ceramic slurry, the doctor blade method is applied to the slurry to obtain second ceramic green sheets 16A to 16D. Then, via holes (second via holes) 17 are formed in the second ceramic green sheets 16 </ b> A to 16 </ b> D by punching, and the conductive paste 14 is filled in the second via holes 17. Moreover, the wiring pattern 18 is printed on the surface of each of the second ceramic green sheets 16 </ b> A to 16 </ b> D using a conductive paste similar to the conductive paste 14. Thereafter, the second ceramic green sheets 16A to 16D are sequentially laminated on one surface of the first fired substrate 12 to obtain a composite laminate. The second ceramic green sheets 16 </ b> A to 16 </ b> D may be laminated in advance to form a laminated body, and this may be laminated on one surface of the first fired substrate 12.

  Next, as shown in FIG.1 (g), the said composite laminated body is baked at 2nd temperature, specifically, 850 degreeC for 1 hour. By this firing, the second ceramic green sheets 16A to 16D become the second fired substrates 20A to 20D in which the vias (second vias) 19 are formed. It is also possible to fire while applying pressure. Alternatively, the conductive paste 14 filled in the first fired substrate 12 may be fired in this step without being fired in advance.

  Next, as shown in FIG. 1 (h), by sputtering, vapor deposition, electrolytic plating, electroless plating, etc. on both surfaces of the fired composite laminate or the surface of the first fired substrate 12, that is, the non-laminated surface. An electrode 21 made of Ti, Mo, Cu, Ni, Au or the like is formed. Specifically, a Ti layer and a Cu layer are formed by sputtering, and then a Cu layer, a Ni layer, and an Au layer are formed by electrolytic plating. Thereby, the multilayer ceramic substrate 100 for IC inspection jig is completed.

  Next, a method of using the multilayer ceramic substrate 100 for electronic component (IC) inspection jig obtained according to the present embodiment will be described with reference to FIG.

  As schematically shown in FIG. 2, the multilayer ceramic substrate 100 is used as a substrate for an IC inspection jig 23 used for inspection of an IC 22, and a terminal (probe) is connected to an electrode 21 formed on one surface thereof. 24 is provided.

  When inspecting the IC 22, the terminals 24 are brought into contact with the terminals 25 of the IC 22, the IC electrical characteristic inspection device 26 is connected to the electrode 21 on the other surface of the multilayer ceramic substrate 100, and the IC 22 is inspected.

  In the present embodiment, since the via hole 13 is formed in the first baked substrate 12, the first baked substrate 12 itself (in particular, the position and shape of the via 15) has high dimensional accuracy. Further, since the second ceramic green sheets 16A to 16D are laminated and fired on the first fired substrate 12 with high dimensional accuracy, the resulting multilayer ceramic substrate 100 also has high dimensional accuracy. Therefore, when the electrode 21 formed on one surface of the first baked substrate 12 is in contact with the terminal 25 of the IC 22 via the terminal (probe) 24 for inspection, the electrode 21 and the terminal 25 of the IC 22 are surely connected. Can be electrically connected.

  Further, since the first baked substrate 12 is made of a high-strength substrate having an alumina component of 95% by weight, it can sufficiently withstand repeated contact with the IC terminal 25 via the probe.

(Second Embodiment)
FIG. 3 is a cross-sectional view showing steps of a method for manufacturing a multilayer ceramic substrate for an IC inspection jig according to the second embodiment of the present invention. Here, in order to avoid overlapping description, description of points that are common to the first embodiment will be omitted, and differences will be mainly described.

  In the present embodiment, first, as shown in FIG. 3A, two first ceramic green sheets 11A and 11B are produced using the same material as in the first embodiment.

  Next, as shown in FIG. 3B, these two first ceramic green sheets 11A and 11B are fired to obtain two first fired substrates 12A and 12B.

  Next, as shown in FIG. 3C, via holes (first via holes) 13 are formed in the first baked substrates 12A and 12B.

  Next, as shown in FIG. 3 (d), the first via hole 13 is filled with the conductive paste 14, and then, as shown in FIG. The vias 15 are formed by heating the substrates 12A and 12B and baking the conductive paste 14. As in the case of the first embodiment, the conductive paste 14 may be baked in a later step.

  Next, as shown in FIG. 3F, two first fired substrates 12A and 12B and one or more (four in the illustrated example) second ceramic green sheets 16A to 16D. Are laminated so that the first fired substrates 12A and 12B are arranged on both sides of the second ceramic green sheets 16A to 16D to obtain a composite laminate.

  Next, as shown in FIG. 3 (g), the composite laminate is fired under pressure, and as shown in FIG. 3 (h), electrodes 21 are formed on one or both sides of the fired composite laminate. . Thereby, the multilayer ceramic substrate 200 for IC inspection jig is completed.

  In the present embodiment, the same effects as in the first embodiment can be obtained, and the first fired substrates 12A and 12B are disposed on both sides of the second ceramic green sheets 16A to 16D and fired. Therefore, deformation during firing of the second ceramic green sheets 16A to 16D is further suppressed, and the reliability of electrical connection by the vias 15 and 19 can be further improved.

  In the present embodiment, the first fired substrate 12, that is, the fired substrate produced by the same method and the same method, is arranged on both sides of the second ceramic green sheets 16 </ b> A to 16 </ b> D. It is also possible to arrange the first baked substrate 12 and use a third baked substrate made of a material and a method different from those of the first baked substrate 12 on the other side. However, for the purposes of the present invention, it is preferred to use a substrate fired at a temperature at least higher than the second temperature, preferably at a temperature of 1350 ° C. or higher, as in the case of the first fired substrate 12. . Moreover, it is preferable to use a conductive paste having a low resistance as exemplified as the conductive paste 14 for reducing the resistance of the via as the conductive paste filling the via hole formed in such a substrate.

Next, experiments conducted to confirm the effects of the present invention and the results thereof will be described.
(Experiment)
An experiment to investigate the effect of the thickness of the first fired substrate / the via hole diameter provided on the first fired substrate on the characteristics of the multilayer ceramic substrate (reliability of electrical connection and adhesion of test terminals (electrodes)) went.

In this experiment, 13 types of multilayer ceramic substrates (samples Nos. 1 to 13) for IC inspection jigs having different thicknesses of the first fired substrate as shown in Table 1 were produced.
[Sample No. Preparation of 1]
1 kg of alumina powder (average particle size 3 μm, specific surface area 1.0 m ² / g) and 120 g of acrylic resin (binder) are put in an alumina pot, and then appropriate amounts of MEK (methyl ethyl ketone) and DOP (plasticizer) are added. Mixing for a time, a ceramic slurry was obtained. Using the obtained ceramic slurry, a ceramic green sheet (first ceramic green sheet) having a thickness of 0.30 mm was obtained by a doctor blade method.

Next, the two first ceramic green sheets were heated and fired at 1400 ° C. for 10 hours. Each of these baked substrates (first baked substrate) is formed with a required number of via holes having a diameter of 85 μm using a CO ₂ laser, and then filled with Ag-based conductive paste in the via holes, and 0 ° C. at 900 ° C. The conductive paste was fired by heating for .5 hours.

Further, borosilicate glass powder (average particle size 3 μm, specific surface area 1.0 m ² / g) mainly composed of SiO ₂ , Al ₂ O ₃ and B ₂ O ₃ and alumina powder (average particle size 3 μm, ratio) (Surface area 1.0 m ² / g) is weighed to a weight ratio of 1: 1 and a total amount of 1 kg and put into an alumina pot, and then add appropriate amounts of MEK (methyl ethyl ketone) and DOP (plasticizer). The ceramic slurry was obtained by mixing for 5 hours. Using the obtained ceramic slurry, a ceramic green sheet (second ceramic green sheet) having a thickness of 0.15 mm was obtained by a doctor blade method.

  A required number of via holes were formed in each of the 20 second ceramic green sheets by punching, and the via holes were filled with an Ag-based conductive paste, and a wiring pattern was formed by a conventional method using the same type of conductive paste.

  After laminating these 20 second ceramic green sheets and further laminating a first fired substrate filled with a conductive paste and firing on both sides to form a composite laminate, heating at 850 ° C. for 1 hour Baked.

  After both surfaces of the fired composite laminate were polished, electrodes (vertical 2 mm × horizontal 2 mm × thickness 0.01 mm) were formed by sputtering and electrolytic plating to produce a multilayer ceramic substrate for an IC inspection jig.

[Sample No. Production of 2 to 13]
Except for changing the kind of raw material powder used in the manufacture of the first fired substrate, the thickness of the green sheet, the via hole diameter, and the conductor material as shown in Table 1, sample No. In the same manner as in No. 1, a multilayer ceramic substrate for IC inspection jig was produced. In addition, as raw material powder, No. No. 8, silicon nitride (average particle size 1 μm, specific surface area 7 m ² / g) In No. 9, mullite (average particle size 2 μm, specific surface area 5 m ² / g) was added to other No. 2-7 and no. 10-13, no. The same alumina as 1 was used.

[Characteristic evaluation]
Characteristic evaluation of the obtained multilayer ceramic substrate for IC inspection jig was performed by the method shown below. The results are also shown in Table 1.
(A) Electrical connection reliability The electrical connection between the electrodes provided on both surfaces of the multilayer ceramic substrate for IC inspection jig was confirmed, and the ratio of the electrodes with which electrical connection was obtained was examined.
(B) Adhesiveness of electrode A load (peel strength) when a copper wire is soldered to an electrode provided on one surface of a multilayer ceramic substrate for an IC inspection jig and pulled at 20 mm / min to break the substrate. Was measured.

  As is apparent from Table 1, particularly good results are obtained when the via hole diameter is 30 μm or more and 100 μm or less and the thickness of the first fired substrate is 0.1 mm or more and 0.5 mm or less. ing.

  It should be noted that the present invention is not limited to the above-described embodiments and the like, and it goes without saying that the present invention can be implemented in various modes without departing from the present invention.

It is sectional drawing which shows the process of the manufacturing method of the multilayer ceramic substrate for IC inspection jigs concerning the 1st Embodiment of this invention. It is a figure which shows typically the usage method of the jig | tool for IC test | inspection using a multilayer ceramic substrate. It is sectional drawing which shows the process of the manufacturing method of the multilayer ceramic substrate for IC inspection jigs concerning the 2nd Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11, 11A, 11B ... 1st ceramic green sheet, 12, 12A, 12B ... 1st baked board | substrate, 13 ... (1st) via hole, 14 ... Conductive paste, 15 ... (1st) via, 16A ˜16D: second ceramic green sheet, 17: (second) via hole, 19: (second) via, 20A-20D: second fired substrate, 21: electrode, 100, 200: IC inspection treatment Multi-layer ceramic substrate.

Claims (8)

After the first ceramic green sheet is fired at a first temperature to produce a first fired substrate, a truncated cone-shaped first via hole is formed in the first fired substrate, and then the first fired substrate is formed. Filling a via hole with a conductive paste that can be fired at a second temperature lower than the first temperature (a);
A first fired substrate filled with the conductive paste on at least one main surface of a second ceramic green sheet that can be fired at the second temperature or a laminate in which a plurality of the second ceramic green sheets are laminated. A step (b) of obtaining a composite laminate by laminating the surface on the large diameter side of the first via hole toward the second ceramic green sheet or the laminate ,
Firing the composite laminate at the second temperature (c);
Possess the (d) forming an electrode on the non-laminated surface of the first fired substrate of the fired composite laminate,
The step (d) includes a step of polishing the non-laminated side surface of the first baked substrate and a step of performing sputtering to form the electrode on the polished surface. Manufacturing method of multilayer ceramic substrate for jig.   2. The method of manufacturing a multilayer ceramic substrate for an electronic component inspection jig according to claim 1, wherein the first temperature is 1350 ° C. or higher and the second temperature is 800 to 1000 ° C. 3.   3. The method of manufacturing a multilayer ceramic substrate for an electronic component inspection jig according to claim 1, wherein in the step (b), the conductive paste previously filled in the first fired substrate is fired. .   4. The method of manufacturing a multilayer ceramic substrate for an electronic component inspection jig according to claim 1, wherein the first via hole is formed by laser processing.   5. The method of manufacturing a multilayer ceramic substrate for an electronic component inspection jig according to claim 1, wherein a diameter of the first via hole is 30 μm or more and 100 μm or less.   The multilayer ceramic substrate for an electronic component inspection jig according to any one of claims 1 to 5, wherein the thickness of the first fired substrate is 0.1 mm or more and 0.5 mm or less. Method.   The multilayer ceramic substrate for an electronic component inspection jig according to claim 1, wherein the conductive paste contains at least one selected from the group consisting of Ag, Cu, Au, Pd, and Pt. Manufacturing method.   In the step (b), there is provided a second via hole that communicates with the first via hole formed in the first fired substrate and is filled with a conductive paste that can be fired at the second temperature. The method of manufacturing a multilayer ceramic substrate for an electronic component inspection jig according to claim 1, wherein two ceramic green sheets are laminated.

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