Conductive film forming apparatus and conductive film forming method

Abstract

To provide a conductive film forming apparatus and a conductive film forming method that can form a uniform conductive film in through holes formed in a substrate. [Solution] The conductive film forming apparatus according to the embodiment comprises a drum having an inner circumferential surface that forms a hollow structure and a holding portion provided on the inner circumferential surface for holding a substrate, an inkjet head for ejecting conductive ink, a rotating mechanism for rotating the drum, and a control unit that controls the inkjet head to eject the conductive ink into a plurality of through-holes in the substrate, and after the ejection of the conductive ink by the inkjet head is completed, controls the rotating mechanism to rotate the drum.

Description

Technical Field

[0001] Embodiments of the present invention relate to a conductive film forming apparatus and a conductive film forming method.

Background Art

[0002] There is a technique in which an inkjet head ejects conductive ink onto a glass substrate with fine through-holes formed therein (TGV (Through Glass Via)) to apply the conductive ink to the through-holes. Thereby, for example, through electrodes are formed.

Prior Art Literature

Patent Literature

[0003]

Patent Document 1

Summary of Invention

Problem to be Solved by the Invention

[0004] However, the diameter of the through-hole formed in the TGV substrate may be equal to or smaller than the diameter of one droplet of conductive ink ejected from the inkjet head (conductive ink droplet). FIG. 11 is a cross-sectional view of a substrate for explaining the relationship between through-holes and conductive ink droplets. For example, the inkjet head ejects conductive ink 94 from the main surface 91 side onto a glass substrate 90 that has two main surfaces 91 and 92 and is provided with through-holes 93 formed to penetrate from one main surface 91 to the other main surface 92 as shown in FIG. 11. However, the conductive ink 94 does not move to the main surface 92 side in the through-hole 93 but remains on the main surface 91 side, which may result in failure to form a uniform conductive film from the main surface 91 side to the main surface 92 side of the through-hole 93.

[0005] The present invention was made to solve the above-mentioned problems, and its objective is to provide a conductive film forming apparatus and a conductive film forming method that can form a uniform conductive film in through holes formed in a substrate. [Means for solving the problem]

[0006] To solve the above-mentioned problems and achieve the objective, a conductive film forming apparatus according to one aspect of the present invention comprises a drum having an inner circumferential surface that forms a hollow structure and a holding portion provided on the inner circumferential surface for holding a substrate, an inkjet head for ejecting conductive ink, a rotating mechanism for rotating the drum, and a control unit that controls the inkjet head to eject the conductive ink into a plurality of through-holes in the substrate, and after the ejection of the conductive ink by the inkjet head is completed, controls the rotating mechanism to rotate the drum.

[0007] Furthermore, in order to solve the above-mentioned problems and achieve the objective, another aspect of the present invention relates to a method for forming a conductive film, in which conductive ink is ejected from the first surface side into a plurality of through-holes in a plate-shaped substrate having a first surface and a second surface opposite to the first surface, and the substrate is moved such that a force is applied to the conductive ink adhering to the substrate in a direction from the first surface toward the second surface. [Effects of the Invention]

[0008] According to one aspect of the present invention, a conductive film forming apparatus and a conductive film forming method can be provided that can form a uniform conductive film in through holes formed in a substrate. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a schematic diagram showing the configuration of a conductive film forming apparatus according to the first embodiment. [Figure 2] Figure 2 is a schematic diagram showing the state in which the substrate is held by the holding part of the conductive film forming apparatus according to the first embodiment. [Figure 3] Figure 3 is a cross-sectional view showing a portion of the substrate according to the first embodiment. [Figure 4] Figure 4 is a cross-sectional view showing the state of a substrate on which conductive ink according to the embodiment has been ejected. [Figure 5] Figure 5 is a cross-sectional view showing the state of the substrate after centrifugal force has been applied to the conductive ink ejected onto the substrate according to the embodiment. [Figure 6] Figure 6 is a cross-sectional view showing another state of the substrate after centrifugal force has been applied to the conductive ink ejected onto the substrate according to the embodiment. [Figure 7] Figure 7 is a schematic diagram showing the configuration of a conductive film forming apparatus according to the second embodiment. [Figure 8] Figure 8 is a schematic diagram illustrating the shape of the drum in the modified example. [Figure 9] Figure 9 is a schematic diagram illustrating the shape of the drum in other modified cases. [Figure 10] Figure 10 is a plan view of a modified drum. [Figure 11] Figure 11 is a cross-sectional view of the substrate illustrating the relationship between through-holes and conductive ink droplets. [Modes for carrying out the invention]

[0010] Hereinafter, embodiments of the conductive film forming apparatus and conductive film forming method disclosed in this application will be described in detail with reference to the attached drawings. In the following embodiments, the case in which an inkjet head ejects conductive ink into fine through-holes (through-hole micro-holes) formed in a glass substrate to form a uniform conductive film in the through-hole micro-holes will be described. However, the inkjet head may also eject conductive ink into fine through-holes formed in a substrate other than a glass substrate, and a uniform conductive film may be formed in the fine through-holes by performing the same process as described below.

[0011] (First embodiment) Figure 1 is a schematic diagram showing the configuration of a conductive film forming apparatus according to the first embodiment. As shown in Figure 1, the conductive film forming apparatus 100 comprises a drum 1, a holding unit 2, an inkjet head 3, a head lifting rail 4, a lifting rail holding mechanism 5, a rotating shaft 6, a control device 7, a moving drive mechanism (not shown), and a rotation drive mechanism (not shown).

[0012] In the specification and claims of this application, "up" indicates the direction away from the installation surface of the conductive film forming apparatus (for example, the factory floor), and "down" indicates the direction opposite to "up".

[0013] Drum 1 has a hexagonal prism shape with an open bottom on the upper side and a hollow interior. Drum 1 has an inner circumferential surface (inner wall surface) 11 and a bottom surface 12, and one end (lower side) of its rectangular tubular shape is covered by the bottom surface 12. The inner circumferential surface 11 is composed of six planes 111. Each of the six planes 111 is erected so as to extend vertically from each of the six sides of the bottom surface 12. The bottom surface 12 is a predetermined distance from the floor of the factory where the conductive film forming apparatus 100 is installed and is a plane parallel to the floor.

[0014] Each of the six planes 111 is provided with a plurality of holding parts 2. The holding parts 2 hold the substrate 80 (see Figure 2). For example, the holding parts 2 may be composed of shelf parts on which the substrate 80 is placed. By placing the substrate 80 on such shelf parts, the shelf parts hold the substrate 80. Alternatively, the holding parts 2 may be composed of suction parts that suction and hold one of the two main surfaces of the substrate 80. When the substrate 80 is suction and held by the suction parts, it is preferable that the substrate 80 is held by suction at a position on the substrate 80 where the through-holes 81 described later are not located. In this embodiment, the mechanism in which the holding parts 2 suction and hold one of the main surfaces of the substrate 80 will be described below.

[0015] In the example of Figure 1, on one flat surface 111, two rows each having four holding portions 2 arranged in the vertical direction are provided side by side in a direction orthogonal to the direction in which the rows extend. That is, eight holding portions 2 are provided on one flat surface 111. Note that Figure 1 illustrates the holding portions 2 of one row among the eight holding portions 2 provided on one flat surface 111, and omits illustration of the remaining holding portions 2 of the other row, and the plurality of holding portions 2 (40 (8×5) holding portions 2) provided on the other five flat surfaces 111. Here, the number and arrangement of the holding portions 2 included in the conductive film forming apparatus 100 are not limited to those described above. Moreover, although the case where one holding portion 2 holds one substrate 80 has been described, one holding portion 2 may hold a plurality of substrates 80. For example, one holding portion 2 may be provided over all of the six flat surfaces 111, and may hold one or a plurality of substrates 80 on each flat surface 111.

[0016] Figure 2 is a schematic diagram showing a state in which a substrate is held by the holding portion of the conductive film forming apparatus according to the first embodiment. Figure 2 illustrates only the drum 1 and the substrates 80 held on one flat surface 111 among the plurality of elements constituting the conductive film forming apparatus 100, and omits illustration of the other elements. As shown in Figure 2, eight substrates 80 are held by eight holding portions 2 on one flat surface 111. The substrates 80 are also held by a total of 40 holding portions 2 on the other five flat surfaces 111 respectively (illustration omitted). Therefore, in the present embodiment, eight substrates 80 are held by eight holding portions 2 for each angular range of 60 degrees (360 degrees / 6). The holding portion 2 supports the substrate 80 such that conductive ink can be ejected to the fine through-holes 81 described later by the inkjet head 3 described later.

[0017] In the present embodiment, description will be given by taking the case where the substrate 80 is a glass substrate as an example. A plurality of fine through-holes 81 are formed in the substrate 80 which is a rectangular glass substrate (TGV (Through Glass Via)). That is, a plurality of fine through-holes 81 penetrating from one main surface to the other main surface of the two main surfaces of the substrate 80 are formed. In the example of Fig. 2, on the substrate 80, 6 rows of 5 fine through-holes 81 arranged in the column direction are arranged in the row direction. That is, in the example of Fig. 2, 30 (5×6) fine through-holes 81 are formed on one substrate 80. However, the number and arrangement of the fine through-holes 81 formed on one substrate 80 are not limited thereto.

[0018] FIG. 3 is a cross-sectional view showing an example of a partial cross-section of the substrate according to the first embodiment. As shown in FIG. 3, the substrate 80 has two main surfaces (a main surface 82 and a main surface 83). The main surface 82 is, for example, an example of a first surface (front surface). The main surface 83 is, for example, an example of a second surface (back surface). The substrate 80 is formed with fine through-holes 81 penetrating from the main surface 82 to the main surface 83. As shown in FIG. 3, a liquid-repellent layer 84 is formed on the main surface 82 of the substrate 80. Note that the liquid-repellent layer 84 is not formed inside the fine through-holes 81. That is, the liquid-repellent layer 84 is provided in a region excluding the fine through-holes 81 out of the entire region of the main surface 82 of the substrate 80. The liquid-repellent layer 84 has a function of repelling conductive ink. Regarding the liquid-repellent processing, the liquid-repellent layer 84 is formed by spin coating before forming the fine through-holes 81 in the substrate 80, and then the fine through-holes 81 are opened, whereby the liquid-repellent layer 84 can be formed only on the main surface 82 of the substrate 80.

[0019] Further, the holding unit 2 sucks and holds the main surface 83 side of the substrate 80 such that the main surface 82 and the main surface 83 are parallel to the plane 111 on which the holding unit 2 is provided. Therefore, the main surface 82 and the main surface 83 of the substrate 80 held by the holding unit 2 are arranged parallel to the vertical plane. In this way, the holding unit 2 holds the substrate 80 so that an inkjet head 3 to be described later can discharge conductive ink to the fine through-holes 81 from the main surface 82 side.

[0020] Returning to the explanation of Figure 1, the inkjet head 3 ejects conductive ink. The inkjet head 3 has an ejection surface 31. Multiple nozzles (holes) are formed on the ejection surface 31. Conductive ink is supplied to the inside of the inkjet head 3 from a tank (not shown), and this conductive ink is pushed out from the nozzles of the inkjet head 3, causing the inkjet head 3 to eject conductive ink from the ejection surface 31 in the direction indicated by the arrow 32. In this embodiment, the ejection surface 31 is a surface parallel to the vertical plane, and the multiple nozzles are arranged in a row at equal intervals along the longitudinal direction of the ejection surface 31. In this embodiment, the pitch (spacing) between two adjacent nozzles formed on the ejection surface 31 matches the spacing between two adjacent through-holes 81 formed on the substrate 80. In other words, the inkjet head 3 can eject conductive ink to the same number of through-holes 81 as the number of nozzles formed on the ejection surface 31. Alternatively, if an integer multiple of the nozzle pitch matches the distance between two adjacent through-holes 81 formed in the substrate, conductive ink can be ejected by using a number of nozzles obtained by dividing the total number of nozzles in the inkjet head 3 by that integer, thereby matching the distance between the through-holes 81 and the nozzle pitch.

[0021] The head lifting rail 4 is a rail that extends in the vertical direction. The head lifting rail 4 supports the inkjet head 3 so that it can move along the rail that extends in the vertical direction.

[0022] The not-shown moving drive mechanism (an example of a moving mechanism) is a mechanism including a motor and gears, which receives instructions from the control device 7 and moves the inkjet head 3 vertically along the head lifting rail 4 based on the received instructions. The moving drive mechanism only needs to be a mechanism that moves the drum 1 and the inkjet head 3 relatively vertically, and may be configured to move the drum 1 vertically, or to move both the drum 1 and the inkjet head 3 vertically.

[0023] The lifting rail holding mechanism 5 holds the head lifting rail 4. The lifting rail holding mechanism 5 is an elongated rectangular prism-shaped member and is fixed to the stand of the conductive film forming apparatus 100. The upper end of the head lifting rail 4 is connected to one end of the lower surface of the lifting rail holding mechanism 5. The other end of the lifting rail holding mechanism 5 is connected to a drive mechanism (an example of a moving mechanism) not shown, and holds the head lifting rail 4 (and the inkjet head 3) so that it can move in a direction perpendicular to the direction of arrow 33.

[0024] The rotating shaft 6 is a cylindrical member that extends vertically. The lower end of the rotating shaft 6 is connected to the center of the hexagonal base 12. That is, the lengths of the perpendiculars drawn from the point where the rotating shaft 6 is connected to the base 12 (the center of the rotating shaft 6) to the midpoints of each of the six sides of the base 12 are all the same. The upper end of the rotating shaft 6 is connected to a rotational drive mechanism (not shown). The drum 1 rotates as the rotating shaft 6 is rotated by the rotational drive mechanism.

[0025] The rotary drive mechanism (rotation mechanism) is a mechanism that includes a motor, etc., and rotates the rotating shaft 6 under the control of the control device 7.

[0026] The control unit 7 comprises a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), HDD (Hard Disk Drive), and a communication interface. These are connected via an internal bus.

[0027] The CPU executes various processes while using the RAM memory area as a temporary storage area for data used in various processes. The ROM and HDD store programs for executing various processes, as well as various databases and tables used when executing various processes. The CPU executes various processes by executing programs stored in the ROM and HDD. The CPU also executes various processes using various databases and tables stored in the ROM and HDD. The communication interface can communicate with the inkjet head 3, the moving drive mechanism, and the rotating drive mechanism. Therefore, the CPU can control each of the inkjet head 3, the moving drive mechanism, and the rotating drive mechanism. That is, the CPU can send instructions to each of the inkjet head 3, the moving drive mechanism, and the rotating drive mechanism. The control device 7 is, for example, an example of a control unit.

[0028] The above describes an example of the configuration of the conductive film forming apparatus 100 according to the first embodiment. Next, an example of the operation of the conductive film forming apparatus 100 will be described.

[0029] First, the substrate 80 is held by the holding parts 2 across the entire inner surface 11. For example, the operator (user) of the conductive film forming apparatus 100 may manually hold the substrate 80 in all of the holding parts 2. Alternatively, a robot may automatically hold the substrate 80 in all of the holding parts 2.

[0030] The control device 7 of the conductive film forming apparatus 100 first transmits an instruction to the rotation drive mechanism to position the drum 1 to a first rotation position. This positions the drum 1 to a rotation position (first rotation position) that enables the ejection of conductive ink from the inkjet head 3 onto eight substrates 80 held on one of the six planes 111. If the rotation position of the drum 1 is already at the first rotation position before such control is performed, this control is unnecessary.

[0031] The control device 7 then controls the moving drive mechanism and the inkjet head 3 so that conductive ink is ejected to all of the through-holes 81 of the eight substrates 80 at the first rotation position.

[0032] Here, the width of the region on the ejection surface 31 of the inkjet head 3 where multiple nozzles are formed (the dimension in the direction perpendicular to the arrow 33) is smaller than the sum of the widths of the two substrates 80 aligned in the short direction of the plane 111 and the width between them. Therefore, the inkjet head 3 moves in the vertical direction and in the direction perpendicular to the vertical direction (the short direction of the plane 111), repeatedly ejecting conductive ink from the multiple nozzles formed on the ejection surface 31 toward the substrates 80, thereby enabling the ejection of conductive ink to all the through-holes 81 in the eight substrates 80 on a single plane 111. Hereinafter, the eight substrates 80 on a single plane 111 will also be referred to as a "substrate group". Alternatively, multiple inkjet heads 3 may be provided to cover the entire substrate group, and conductive ink may be ejected to all the through-holes 81 included in the substrate group without moving the inkjet heads 3. Alternatively, multiple inkjet heads 3 may be provided so as to cover the entire width of the substrate group in the short-side direction of the plane 111, and conductive ink may be ejected into all of the through-holes 81 included in the substrate group by moving the inkjet heads 3 only in the vertical direction.

[0033] The control device 7 transmits an instruction to the movement drive mechanism to move the inkjet head 3 vertically at a predetermined speed at the first rotation position. As a result, the movement drive mechanism positions the inkjet heads 3 so that they face each other in order from the through-hole micro-hole 81 located at the top, and moves them downward while ejecting conductive ink. The control device 7 moves the inkjet head 3 to the top position as described above before the start of coating.

[0034] Next, the control device 7 sends a signal to the moving drive mechanism to move the inkjet head 3 back to the top position, and also sends a signal to a drive mechanism (not shown) to move the lifting rail holding mechanism 5 along the shorter direction of the plane 111. As a result, the inkjet head 3 is positioned to face the substrate 80 in the substrate group that has not yet had conductive ink applied to it. The moving drive mechanism then moves the inkjet head 3 downwards while ejecting conductive ink again.

[0035] The control device 7 repeatedly performs the above-described process until the discharge of conductive ink to all through-holes 81 in the substrate group is completed at the first rotation position. As a result, the discharge of conductive ink to all through-holes 81 in the eight substrates 80 is completed at the first rotation position.

[0036] Here, as described above, the inner circumferential surface 11, which is composed of six planes 111, has a hexagonal shape in plan view. Therefore, the rotation position obtained by rotating the drum 1 60 degrees in a predetermined direction from the first rotation position is defined as the second rotation position, the rotation position obtained by rotating the drum 1 120 degrees in a predetermined direction from the first rotation position is defined as the third rotation position, the rotation position obtained by rotating the drum 1 180 degrees in a predetermined direction from the first rotation position is defined as the fourth rotation position, the rotation position obtained by rotating the drum 1 240 degrees in a predetermined direction from the first rotation position is defined as the fifth rotation position, and the rotation position obtained by rotating the drum 1 300 degrees in a predetermined direction from the first rotation position is defined as the sixth rotation position.

[0037] The control device 7 then controls the rotary drive mechanism to rotate the drum 1 in a predetermined direction at a first rotational speed, and to stop the drum 1 at each rotational position in the order from the second rotational position to the sixth rotational position. That is, the control device 7 rotates the drum 1 in a predetermined direction at a first rotational speed from the Nth rotational position (where N is an integer between 1 and 5) to the (N+1)th rotational position, and stops the drum 1 at the (N+1)th rotational position. Then, at each rotational position from the second to the sixth rotational position, with the drum 1 stopped, the control device 7 performs the same processing as described above at the first rotational position. As a result, at each rotational position from the second to the sixth rotational position, the discharge of conductive ink into all the through-holes 81 of the eight substrates 80 is completed.

[0038] Through the process described above, the discharge of conductive ink to all through-holes 81 in all substrates 80 is completed in the six planes 111. An example of the state of the conductive ink adhering to the substrate 80 at this time will be described. Figure 4 is a cross-sectional view showing the state of the substrate on which the conductive ink according to the embodiment has been discharged. As shown in Figure 4, the diameter of the conductive ink 85 discharged onto the substrate 80 is approximately the same size as the diameter of the through-holes 81, so the conductive ink 85 remains on the main surface 82 side in the through-holes 81 without moving to the main surface 83 side. Furthermore, since the liquid-repellent layer 84 is formed on the main surface 82 side, the conductive ink 85 can be kept in the through-holes 81 without spreading onto the liquid-repellent layer 84.

[0039] Next, the control device 7 controls the rotation drive mechanism to make the drum 1 rotate at high speed. For example, the control device 7 makes the rotation drive mechanism rotate the drum 1 at a second rotation speed that is faster than the first rotation speed. The direction of rotation at this time may be the same as the predetermined direction described above, or it may be the opposite direction. After rotating a predetermined number of times in the predetermined direction, it may be rotated a predetermined number of times in the opposite direction. As a result, a centrifugal force acts on the conductive ink 85 attached to the substrate 80 in the direction from the main surface 82 to the main surface 83 of the substrate 80. For example, if the angular velocity corresponding to the second rotation speed is ω [rad / s], the mass of the conductive ink 85 attached to the substrate 80 is m [kg], and the distance from the rotation axis 6 to the main surface 82 of the substrate 80 (the radius of the circular motion of the conductive ink 85) is r [m], then a centrifugal force of mrω² [N] is applied to the conductive ink 85 attached to the substrate 80. As a result, as shown in Figure 5, the conductive ink 85 fills the through-holes 81 all the way to the main surface 83, that is, to the back of the through-holes 81. Alternatively, as shown in Figure 6, the conductive ink 85 adheres to the inner wall surface of the substrate 80 forming the through-holes 81, all the way to the back of the through-holes 81. Therefore, when the conductive ink 85 is fired, a uniform conductive film can be formed in the through-holes 81. This conductive film may be used as a through-electrode or as a seed during plating.

[0040] Here, we will explain the case in which a conductive material (metal) is inserted into through-holes formed in a glass substrate by sputtering to form a through-electrode. First, a conductive film (metal film) is formed on the entire surface of the glass substrate where the through-holes are formed by sputtering. Then, the conductive film formed on the surface is scraped off by CMP (Chemical Mechanical Polishing) or the like. Since conductive film formation is only necessary inside the through-holes of the through-electrode, the conductive film on the surface is removed.

[0041] However, this technique of forming through-holes in a glass substrate by sputtering conductive material to create through-hole electrodes has four main problems. The first problem is that, because sputtered particles do not always fly perpendicular to the glass substrate, a relatively large amount of film is deposited in the shallower parts of the through-holes, while the amount deposited in the deeper parts is relatively small. The second problem is that, because sputtering does not allow for the selective formation of conductive films in the through-holes, a relatively large amount of conductive material is consumed, resulting in relatively high running costs. The third problem is that, because sputtering is performed in a vacuum, the sputtering equipment becomes large and expensive. The fourth problem is that, because most of the formed conductive film is removed, the amount of waste material increases, and the use of chemicals during CMP also generates waste liquid, resulting in a large environmental burden.

[0042] On the other hand, in this embodiment, the conductive ink ejected by the inkjet head 3 can fill the through-pores 81 to a relatively deep extent. Therefore, when the conductive ink is fired, a uniform conductive film can be formed in the through-pores 81, and a homogeneous, low-resistance, and highly reliable through-electrode can be formed. Furthermore, in this embodiment, since the inkjet head 3 selectively ejects conductive ink into the through-pores 81 and fills them, the increase in waste material is suppressed, and low cost and low environmental impact can be achieved.

[0043] The conductive film forming apparatus 100 according to the first embodiment has been described above. As described above, the conductive film forming apparatus 100 includes a drum 1 having an inner circumferential surface 11 that forms a hollow structure and a holding part 2 provided on the inner circumferential surface 11 for holding a substrate 80, an inkjet head 3 for ejecting conductive ink, a rotating mechanism consisting of a rotation drive mechanism and a rotating shaft 6 for rotating the drum 1, and a control device 7 that controls the inkjet head 3 to eject conductive ink into a plurality of through-holes 81 in the substrate 80, and after the ejection of conductive ink by the inkjet head 3 is completed, controls the rotating mechanism to rotate the drum 1 on the rotating mechanism.

[0044] Furthermore, the conductive film forming apparatus 100 is equipped with a moving mechanism that moves the inkjet head 3 relative to the drum 1 in a direction different from the direction of movement by the rotation mechanism, and the control device 7 moves the inkjet head 3 relative to the drum 1 by the moving mechanism so that the inkjet head 3 can eject conductive ink into all of the multiple through-holes 81 in the substrate 80 held by the holding unit 2, and completes the ejection of conductive ink by the inkjet head 3 by moving the inkjet head 3 relative to the drum 1.

[0045] Furthermore, multiple holding parts 2 are provided on the inner circumferential surface 11. The substrates 80 are arranged in groups according to a range corresponding to a predetermined angle (60 degrees) on the inner circumferential surface 11. The predetermined angle is set in advance in the rotation direction of the drum 1. Multiple substrate groups are arranged in a line in the rotation direction of the drum 1. The control device 7 repeatedly controls the rotation mechanism to rotate the drum 1 by a predetermined angle at a first rotation speed and then stop the drum 1 so that when the drum 1 stops, the ejection surface 31 of the inkjet head 3 and the substrate groups corresponding to the predetermined angle face each other. In addition, each time the drum 1 stops, the control device 7 controls the rotation mechanism and the inkjet head 3 so that conductive ink is ejected into the multiple through-holes of the substrate groups. After the ejection of conductive ink to all substrate groups is completed, the control device 7 rotates the drum 1 at a second rotation speed that is faster than the first rotation speed.

[0046] Furthermore, a liquid-repellent layer 84 is provided on the main surface 82 of the substrate 80 facing the inkjet head 3, and the control device 7 causes conductive ink to be ejected from the liquid-repellent layer 84 side to the inkjet head 3 through multiple through-holes 81 of the substrate 80 on which the liquid-repellent layer 84 is provided.

[0047] Furthermore, the conductive film forming apparatus 100 performs a conductive film forming method in which conductive ink is ejected from the main surface 82 side into a plurality of through-holes 81 in a plate-shaped substrate 80 having a main surface 82 and a main surface 83 opposite to the main surface 82, and the substrate 80 is moved so that a force is applied to the conductive ink attached to the substrate 80 in the direction from the main surface 82 to the main surface 83.

[0048] According to the conductive film forming apparatus 100 of the first embodiment, as described above, a uniform conductive film can be formed in the through-hole micropores 81.

[0049] In the first embodiment, the conductive film forming apparatus 100 was described in which conductive ink is ejected into multiple through-holes 81 in eight substrates 80 on each of the six planes 111 of the drum 1 using one inkjet head 3, one head lifting rail 4, and a rotary drive unit. However, the conductive film forming apparatus 100 may also eject conductive ink into multiple through-holes 81 in each of the substrate groups on each of the six planes 111 without rotating the drum 1, using each of the six inkjet heads 3 and each of the six head lifting rails 4 corresponding to each of the six planes 111.

[0050] Furthermore, in the first embodiment, the conductive film forming apparatus 100 was exemplified by defining the position where the plane 111 and the ejection surface 31 of the inkjet head 3 are parallel as the first to sixth rotation positions, but it is not limited to this. As long as conductive ink can be ejected from the inkjet head 3 into the through-holes 81, the position where the drum 1 is stopped in order to eject from the inkjet head 3 does not have to be a position where the ejection surface 31 of the inkjet head 3 and the plane 111 are parallel.

[0051] Furthermore, in the first embodiment, the conductive film forming apparatus 100 is shown as moving the head lifting rail 4 and the inkjet head 3 along the shorter direction of the plane 111 by controlling the drive mechanism of the lifting rail holding mechanism 5, thereby aligning the uncoated substrate 80 with the inkjet head 3, but the apparatus is not limited to this. For example, the drum 1 may be rotated to align the uncoated substrate 80 with the inkjet head 3. In this case, the angle of the inkjet head 3 (the rotation angle around a line extending vertically through the longitudinal center of the inkjet head 3) may be adjusted by the drive mechanism of the lifting rail holding mechanism 5.

[0052] Furthermore, in the first embodiment, the conductive film forming apparatus 100 is exemplified as rotating the drum 1 at a second rotational speed after the conductive ink is applied by the inkjet head 3, but it is not limited to this. After the application of conductive ink and the rotation of the drum 1 at the second rotational speed are completed, the application of conductive ink and the rotation of the drum 1 at the second rotational speed may be performed again. Alternatively, conductive ink may be applied multiple times (multiple times) to a single through-hole micro-hole 81, and then the rotation of the drum 1 at the second rotational speed may be performed.

[0053] (Second embodiment) Next, a conductive film forming apparatus according to the second embodiment will be described. In describing the second embodiment, the differences from the first embodiment will be mainly described, and descriptions of the same components may be omitted.

[0054] Figure 7 is a schematic diagram showing the configuration of a conductive film forming apparatus according to the second embodiment. The conductive film forming apparatus 101 shown in Figure 7 is the conductive film forming apparatus 100 shown in Figure 1, with all elements except the control device 7 rotated 90 degrees relative to the floor. As a result, the inkjet head 3 can move horizontally (in the direction indicated by the double arrow 37) instead of vertically, and the direction in which the rotation axis 6 extends becomes horizontal instead of vertically. The conductive film forming apparatus 101 performs the same processing as the conductive film forming apparatus 100.

[0055] In the second embodiment, the ejection surface 31 of the inkjet head 3 is positioned facing downward in the vertical direction. This means that droplets of conductive ink from the inkjet head 3 are ejected vertically downward. As a result, compared to the first embodiment, it becomes unnecessary to consider the difference in water head between the supply tank and the ejection surface 31 of the inkjet head 3, as well as the gravity of droplets adhering to the nozzle surface, when supplying conductive ink to the inkjet head 3 and when ejecting conductive ink from the inkjet head 3.

[0056] Furthermore, during the process in which the inkjet head 3 ejects conductive ink and applies it to the substrate 80, the substrate 80, after the conductive ink has been applied, may be positioned above the drum 1. However, only about 1 to 3 drops of ink are ejected from the inkjet head 3 into the through-holes 81, and one drop of ink is about 2 pL. Therefore, the possibility of it moving due to gravity is extremely low, and there is no problem even if it is upside down. It is preferable to prevent the substrate 80 from falling from the drum 1 by securely holding the substrate 80 with the holding part 2. For example, if the holding part 2 is a type of holding part that holds the substrate 80 by suction, in this embodiment, a stronger suction force than in the first embodiment may be applied.

[0057] After the discharge of conductive ink (coating of conductive ink) to all substrates 80 is completed, the control device 7 retracts the inkjet head 3 to a predetermined retracted position, rotates (raises) the elements other than the control device 7 90 degrees relative to the floor so that they are in the same state as in the first embodiment, and controls the rotation drive mechanism so that the drum 1 rotates at the second rotation speed. Alternatively, the control device 7 may control the rotation drive mechanism so that the drum 1 rotates at the second rotation speed while the drum 1 and inkjet head 3 are in the same state as when the conductive ink was coated (as shown in Figure 7).

[0058] The conductive film forming apparatus 101 according to the second embodiment has been described above. According to the conductive film forming apparatus 101 according to the second embodiment, a uniform conductive film can be formed in the through-hole micropores 81, similar to the conductive film forming apparatus 100 according to the first embodiment.

[0059] (A variation of the drum) In the first and second embodiments, the shape of the drum 1 in the conductive film forming apparatus 100, 101 was described as a rectangular tube shape, particularly a shape in which one end of the bottom surface 12 is hexagonal and covered. However, the shape of the drum 1 does not need to be hexagonal; it can be a polygon such as a triangle, square, or pentagon. Furthermore, it does not have to be a rectangular tube shape; as shown in Figure 8, it may be a cylindrical shape with one end covered, or as shown in Figure 9, it may be a conical shape with the apex portion cut off, forming a cavity inside where the cut-off portion opens. Figure 8 is a schematic diagram illustrating the shape of a modified drum. Figure 9 is a schematic diagram illustrating the shape of a drum according to another modified drum.

[0060] In both Figures 8 and 9, the positions corresponding to the 1st to 6th rotation positions described in Embodiment 1 (positions where the drum 1 is stopped when ink is applied from the inkjet head 3) can be determined in advance by determining a predetermined range in which conductive ink can be ejected from the inkjet head 3 into the through-holes 81, and setting the positions corresponding to this predetermined range in advance.

[0061] Figure 10 is a plan view of a modified drum. As shown in Figure 10, the conductive film forming apparatus 100, 101 may be equipped with a plurality of inkjet heads 3 that eject conductive ink in different directions (the directions in which the conductive ink is ejected are not parallel), and a set of a plurality of planes 112 such that the direction of the normal vector coincides with the ejection direction of the plurality of conductive inks by the plurality of inkjet heads 3 may be provided at predetermined angle ranges (45 degrees in the example of Figure 10). Furthermore, at least one holding part 2 may be provided for each plane 112.

[0062] (Other variations of the drum) In the case of the drum 1 according to the first embodiment, when conductive ink is ejected into the multiple through-holes 81 of the substrate 80, all six planes 111 may be arranged so that they are parallel to the horizontal plane. That is, the shape is unfolded around the bottom surface 12. The lower ends of the six planes 111 are in contact with each side of the bottom surface 12 and are arranged on a horizontal plane. The inkjet head 3 is positioned so that the ejection surface 31 is parallel to the floor, as shown in Figure 7. In this state, conductive ink is ejected from above by the inkjet head 3 into the multiple through-holes 81 of the substrate 80 held by the holding parts l2 of each plane 111. That is, droplets of conductive ink from the inkjet head 3 are ejected vertically downward. As a result, compared to the first embodiment, it is no longer necessary to consider the difference in water head between the supply tank and the ejection surface 31 of the inkjet head 3, or the gravity of droplets adhering to the nozzle surface, when supplying conductive ink to the inkjet head 3 or when ejecting conductive ink from the inkjet head 3.

[0063] Then, after the discharge of conductive ink into the multiple through-holes 81 of all substrates 80 is complete, the six plate-shaped members arranged on the horizontal plane are raised to assemble a rectangular cylindrical member (drum 1) that is hexagonal in plan view. After the drum 1 is assembled, the drum 1 is rotated at a second rotational speed, similar to the first embodiment.

[0064] Alternatively, the six planes 111 may be arranged horizontally, connected by edges shared with adjacent planes 111. The bottom plane 12 may be connected to the lower end of any of the planes 111, or it may be positioned separately from the six planes 111. When conductive ink is ejected into the multiple through-holes 81 of the substrate 80, the six planes 111 are arranged so that they are parallel to the horizontal plane, and the inkjet head 3 is positioned so that its ejection surface 31 is parallel to the floor, as shown in Figure 7. In this state, conductive ink is ejected from above by the inkjet head 3 into the multiple through-holes 81 of the substrate 80 held by the holding parts 2 of each plane 111. That is, droplets of conductive ink from the inkjet head 3 are ejected vertically downward. Therefore, even in this case, compared to the first embodiment, it is no longer necessary to consider the difference in water head between the supply tank and the ejection surface 31 of the inkjet head 3, or the gravity of droplets adhering to the nozzle surface, when supplying conductive ink to the inkjet head 3 or ejecting conductive ink from the inkjet head 3.

[0065] Then, after the discharge of conductive ink into the multiple through-holes 81 of all substrates 80 is complete, each of the six plate-shaped members having six planes 111 is positioned on the member having the bottom surface 12 such that the angle between the bottom surface 12 and each of the six planes 111 is 90 degrees. This assembles the drum 1. After the drum 1 is assembled, it is rotated at a second rotational speed, similar to the first embodiment.

[0066] (Other variations) In the embodiments described above, it is illustrated that the substrate 80 is provided parallel to the plane 111, but the invention is not limited to this. The ink can be filled into the through-holes 81 most efficiently when the direction of the centrifugal force acting on the substrate 80, which is held by the inner circumferential surface 11 as the drum 1 rotates, coincides with the direction in which the through-holes 81 provided in the substrate 80 extend. In other words, if the through-holes 81 are provided perpendicular to the main surfaces 82 and 83, it is desirable to arrange the substrate 80 so that the main surfaces 82 and 83 are parallel to the plane 111. If the through-holes 81 are provided not perpendicular to the main surfaces 82 and 83, it is desirable to arrange the substrate 80 so that the direction in which the through-holes 81 extend coincides with the direction of the centrifugal force acting on the substrate 80 as the drum 1 rotates.

[0067] In the embodiments described above, it was illustrated that the pitch between the nozzles of the inkjet head 3 and the pitch of the through-holes 81 provided in the substrate 80 are the same or are integer multiples of each other, but the invention is not limited to this. If the pitch between the nozzles of the inkjet head 3 and the pitch of the through-holes 81 are not the same or are not integer multiples of each other, the inkjet head 3 and the drum 1 can be moved relative to each other along the rotational direction of the drum 1 to make the positions of the nozzles of the inkjet head 3 and the positions of the through-holes 81 coincide, thereby enabling ink to be ejected.

[0068] Although embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, modifications, and combinations can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of Symbols]

[0069] 1 Drum 2 Holding part 3. Inkjet head 4. Head lifting rail 6 rotation axes 7 Control device

Claims

1. A drum having an inner circumferential surface that forms a hollow structure, and a holding portion provided on the inner circumferential surface for holding a substrate, An inkjet head that ejects conductive ink, A rotating mechanism for rotating the drum, A control unit controls the inkjet head to eject the conductive ink into a plurality of through-holes in the substrate, and after the ejection of the conductive ink by the inkjet head is completed, controls the rotating mechanism to rotate the drum in the rotating mechanism, A conductive film forming apparatus equipped with the following features.

2. The system further comprises a moving mechanism that moves the inkjet head relative to the drum in a direction different from the direction of movement by the rotation mechanism, The control unit, The moving mechanism moves the inkjet head relative to the drum so that the inkjet head can eject the conductive ink into all of the plurality of through-holes in the substrate held by the holding part. The ejection of the conductive ink by the inkjet head is completed by moving the inkjet head relative to the drum. The conductive film forming apparatus according to claim 1.

3. Multiple holding portions are provided on the inner circumferential surface. The substrates are arranged in groups corresponding to a range of predetermined angles on the inner surface. The predetermined angle is set in advance in the direction of rotation of the drum. The aforementioned group of substrates is arranged so as to be aligned in the rotational direction of the drum. The control unit, The rotation mechanism is repeatedly controlled to rotate the drum by a predetermined angle at a first rotational speed, and then stop the drum, so that when the drum stops, the ejection surface of the inkjet head and the substrate group corresponding to the predetermined angle face each other. Each time the drum is stopped, the rotating mechanism and the inkjet head are controlled so that the conductive ink is ejected into the plurality of through-holes in the substrate group. After the discharge of the conductive ink to all substrates is completed, the rotating mechanism is instructed to rotate the drum at a second rotational speed faster than the first rotational speed. The conductive film forming apparatus according to claim 1.

4. The shape of the drum is a rectangular tube with one end covered, a cylindrical shape with one end covered, or a cone shape with the apex portion cut off, forming a cavity inside where the cut-off portion is open. The conductive film forming apparatus according to claim 1.

5. A liquid-repellent layer is provided on the surface of the substrate facing the inkjet head. The control unit causes the conductive ink to be ejected from the liquid-repellent layer side to the inkjet head into the plurality of through-holes in the substrate on which the liquid-repellent layer is provided. The conductive film forming apparatus according to claim 1.

6. Conductive ink is ejected from the first surface side into a plurality of through-holes in a plate-shaped substrate having a first surface and a second surface opposite to the first surface. The substrate is moved such that a force is applied to the conductive ink adhering to the substrate in a direction from the first surface toward the second surface. Conductive film formation method.

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