JP2010149301A - Screen printing method and device therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of forming a printing pattern of a high aspect ratio, by a screen printing method. <P>SOLUTION: This screen printing method includes a process for supplying a paste to at least one-parts of an upper face of a screen and a pattern opening part, by moving a scraper on the screen having the pattern opening part, while applying ultrasonic vibration onto at least one part of the paste, and a process for printing the paste onto a body to be printed through the pattern opening part of the screen, by moving a squeegee on the screen while contacting with and pressing the screen. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a screen printing method for printing a print pattern on a substrate, and more particularly to a screen printing method for printing a fine print pattern.

  Screen printing is a type of stencil printing, and is a printing method in which a pattern opening is provided in a screen and a paste such as ink is transferred to a printing medium through the pattern opening. For example, in the electronics field, a screen printing method for clean printing of conductive paste is used for forming electrodes for solar cells, forming internal electrodes for chip components such as chip inductors, chip capacitors and chip resistors, forming coils, and forming resistors. , Used widely. Moreover, the screen printing method of screen-printing an insulating paste is also used for forming partition walls such as PDP and electronic paper. Patterns printed with these pastes are becoming increasingly finer as electronic devices become more sophisticated and more sophisticated. In recent years, the line width of a required printing pattern (the shape of a printed paste) has been reduced to 100 μm or less, and a printing shape having a film thickness as thick as possible, that is, a printing shape having a high aspect ratio has been required.

  In the screen printing method, a screen printing method has been proposed in which the viscosity of the paste is reduced by vibrating the screen in order to facilitate the passage of the paste through the pattern opening. For example, as an apparatus for a screen printing method that vibrates a screen, Patent Document 1 discloses a screen printing apparatus that prints on a printing medium while supplying a paste on the screen, and is incorporated in a screen frame. There is disclosed a screen printing apparatus including a vibration element that transmits vibration of the vibration element to the screen through the screen frame.

  Further, in Patent Document 2, a screen in which through holes having a predetermined pattern are formed is superposed on a substrate, a paste is supplied onto the screen, the paste is filled into the through holes using a squeegee, After filling the through hole with the paste, after applying ultrasonic vibration to the screen or while applying ultrasonic vibration, the printed material and the screen are separated, and the paste in the through hole is removed from the inner surface of the through hole. A screen printing method is disclosed in which ultrasonic vibration is applied to the screen through the squeegee in a screen printing method that is separated from the screen and left on the printing medium.

  Patent Document 3 discloses a screen printing machine that prints a printing material on a substrate using a screen, and is provided with a vibration generating means for applying vibration to the screen. .

  Patent Document 4 includes a printed circuit board to which cream solder is applied and a screen in close contact with a predetermined surface of the printed circuit board, and the cream solder is printed on the printed circuit board through the screen. A solder printing apparatus, comprising: a vibrating head that is driven when the cream solder is printed and when the cream solder is printed. An apparatus is disclosed.

Patent Document 5 discloses a screen printing method in which a printing agent is printed on a printing plate by moving a squeegee along the upper surface of the screen, and then the screen and the printing plate are separated from each other. A screen printing method is disclosed in which at least one of the screen and the printing plate is vibrated between the end and the start of separation between the screen and the printing plate.
JP 2005-297226 A Japanese Patent Laid-Open No. 2002-1913 JP 05-147192 A Japanese Patent Laid-Open No. 06-91845 Japanese Patent Laid-Open No. 06-106705

  With the advancement of electronic devices, etc., the line width of the print pattern by the screen printing method has been refined. As the line width becomes finer, the paste remains on the wall of the pattern opening of the mask during screen printing, and the problem arises that the so-called plate removal property is deteriorated and the film thickness of the printed pattern is reduced. Sometimes. Due to this problem, not only the electric resistance value becomes high, but also disconnection due to printing failure such as fading may occur. Moreover, in order to print a printing pattern having a high aspect ratio, it is effective to use a high-viscosity paste. is there.

  In view of the above problems, an object of the present invention is to obtain a screen printing method for forming an excellent printing pattern having a high aspect ratio.

  The inventors of the present invention have found that it is effective to obtain an excellent print pattern having a high aspect ratio by applying ultrasonic vibration to the paste at a predetermined timing during screen printing. completed.

  The present invention supplies paste to at least part of the upper surface of the screen and the pattern opening by moving the scraper over the screen having the pattern opening while applying ultrasonic vibration to at least part of the paste. And a step of printing a paste on a printing medium through a pattern opening of the screen by moving the squeegee while pressing and pressing on the screen.

Preferred embodiments of the screen printing method of the present invention are shown below. In the present invention, these embodiments can be appropriately combined.
(1) The ultrasonic vibration is applied to the paste via a resonator disposed in front of the moving direction of the scraper in the step of supplying the paste.
(2) Ultrasonic vibration is applied to the paste through a scraper.
(3) Apply ultrasonic vibration to the paste through a squeegee.
(4) In the step of printing the paste on the substrate, the squeegee moves in the printing direction, and in the step of supplying the paste, the scraper moves in the direction opposite to the printing direction.
(5) The frequency of ultrasonic vibration is 10 KHz to 3 MHz.
(6) The ultrasonic vibration source is a Langevin type vibrator.
(7) The Langevin type vibrator is a vibrator containing lead zirconate titanate.
(8) The paste has a viscosity of 300 to 1000 Pa · s when measured at 25 ° C. and 10 rpm.
(9) The paste contains 85 to 95 wt% inorganic particles, 1 to 5 wt% binder, and 1 to 7 wt% solvent.

  The present invention also provides a squeegee for printing a paste on a printing medium by moving while contacting and pressing on the screen, and supplying the paste to the upper surface of the screen and the pattern opening by moving on the screen. A screen printing apparatus including a scraper and an ultrasonic vibration applying mechanism for applying ultrasonic vibration to at least a part of the paste, the ultrasonic vibration applying mechanism including an ultrasonic vibration source, and ultrasonic vibration A screen printing apparatus having a structure in which a source is connected to a scraper, a structure to be connected to a squeegee, or a structure to be connected to a resonator disposed in the moving direction of the scraper when supplying paste.

  Moreover, this invention is a screen printing apparatus used for the above-mentioned screen printing method.

  Moreover, this invention is an electronic device or circuit board which has the electrode, electrode terminal, wiring, and / or partition which were formed by the above-mentioned screen printing method. The electronic device is a solar cell, a chip inductor, electronic paper, or a plasma display panel, and the circuit board is preferably a printed board or a ceramic board.

  If the screen printing method of the present invention is used, an excellent printing pattern having a high aspect ratio can be formed.

  In the screen printing method of the present invention, in the step of supplying the paste to at least one of the upper surface of the screen and the pattern opening performed before the step of printing the paste on the printing body (printing step) (paste supply step), When the paste is applied on the screen by the scraper, the ultrasonic vibration is applied to at least a part of the paste.

  In the present invention, “a high-viscosity paste” refers to a paste having a viscosity of 300 Pa · s or more when measured at 10 rpm at 25 ° C. unless otherwise specified. In the present invention, “thixotropy” refers to the property that, when the paste is stirred, the viscosity is lower than before stirring.

  Hereinafter, the screen printing method of the present invention will be described in detail.

  First, a screen printing apparatus that can be used in the screen printing method of the present invention will be described. FIG. 1 is a schematic cross-sectional view of a part of a screen printing apparatus for explaining an example of a paste supplying process of the screen printing method of the present invention. As shown in FIG. 1, the screen printing apparatus used in the screen printing method of the present invention includes a squeegee 10 and a scraper 15. The squeegee 10 is a component for printing the print pattern 32 on the printing medium 30 by moving on the screen 20 while applying pressure to the screen 20 during the printing process. Further, the screen printing apparatus used in the screen printing method of the present invention has a scraper 15 for applying the paste 31 on the screen 20 in the paste supplying step.

  The screen printing apparatus used in the present invention further includes a holding portion (not shown) for holding the squeegee 10 and the scraper 15. The holding part not only holds the scraper 15 and the squeegee 10 but also has a structure capable of performing a predetermined vertical movement for contacting the scraper 15 and the squeegee 10 to the upper surface of the screen 20 and applying pressure. Have The screen printing apparatus used in the present invention can have one holding unit for holding both the squeegee 10 and the scraper 15. Further, the screen printing apparatus used in the present invention may have one holding part for each of the squeegee 10 and the scraper 15 so that the squeegee 10 and the scraper 15 can move independently. In addition, when it has the resonator 12 mentioned later, the holding | maintenance part of the resonator 12 can be used as the holding | maintenance part common to the scraper 15. FIG. In any case, the screen printing apparatus used in the present invention has a mechanism that allows the squeegee 10 and the scraper 15 to move up and down independently. The resonator 12 may have a mechanism that can move up and down independently, but may have a structure that moves up and down in conjunction with the up and down movement of the scraper 15, and a predetermined distance from the upper surface of the screen 20. It is also possible to have a structure in which the resonator 12 is fixed so that In the present invention, the state in which the scraper 15 and the squeegee 10 are in contact with the upper surface of the screen 20 (or the state in which they are close to each other with a slight gap) is the “lower position”, and is separated from the upper surface of the screen 20. This state is called “up position”.

  The screen printing apparatus used in the present invention further includes an ultrasonic vibration applying mechanism for applying ultrasonic vibration to at least a part of the paste 31 at least in the paste supplying step. The ultrasonic vibration application mechanism includes an ultrasonic vibration source 11.

  In the present invention, the method for applying the ultrasonic vibration generated by the ultrasonic vibration source 11 to the paste 31 is not particularly limited. Specifically, the ultrasonic vibration source 11 transmits the ultrasonic vibration to the resonator 12 that is at least one of the parts of the screen printing apparatus such as the scraper 15 and the squeegee 10 and / or a separate part. Connected and ultrasonic vibration can be applied to the paste 31 via these components. 1 and 2 are schematic cross-sectional views of examples in which the ultrasonic vibration source 11 is connected to the scraper 15. 3 and 4 are schematic cross-sectional views of examples in which the ultrasonic vibration source 11 is connected to the squeegee 10. 5 and 6 are schematic cross-sectional views of examples in which the ultrasonic vibration source 11 is connected to a resonator 12 that is a separate component.

  The present invention includes a screen printing apparatus that can be used in the screen printing method of the present invention. Specifically, the screen printing apparatus of the present invention moves on the screen 20 by moving on the screen 20 and the squeegee 10 for printing the paste 31 on the substrate 30 by moving while contacting and pressing the screen 20. The screen printing apparatus includes a scraper 15 that supplies paste 31 to the upper surface of the screen 20 and the pattern opening 23 and an ultrasonic vibration application mechanism for applying ultrasonic vibration to at least a part of the paste 31. In the screen printing apparatus of the present invention, the ultrasonic vibration application mechanism includes the ultrasonic vibration source 11, the ultrasonic vibration source 11 is connected to the scraper 15, the ultrasonic vibration source 11 is connected to the squeegee 10, or the ultrasonic wave It is preferable that the screen printing apparatus has at least one of the structures connected to the resonator 12 disposed in front of the moving direction of the scraper 15 when the vibration source 11 supplies the paste 31. In particular, since the shape of the resonator 12 is more flexible in design than the squeegee 10 and the scraper 15, it is easy to obtain an optimum shape for applying ultrasonic vibration to the paste 31. Therefore, the screen printing apparatus of the present invention preferably has a structure in which the ultrasonic vibration source 11 is connected to the resonator 12.

  When the ultrasonic vibration source 11 of the screen printing apparatus has a structure connected to the scraper 15, the ultrasonic vibration can be applied to the paste 31 through the scraper 15. In this case, since the scraper 15 is in contact with the paste 31 in the paste supplying step, no separate component (resonator 12) is required. Further, since the shape of the scraper 15 is more flexible in design than the squeegee 10, the shape of the scraper 15 can be made preferable for transmission of ultrasonic vibration.

  Next, the screen printing method of the present invention will be described. The screen printing method of the present invention includes a paste supplying step and a printing step.

  In the paste supplying step, the scraper 15 moves on the screen 20 having the pattern openings 23 while applying ultrasonic vibration to at least a part of the paste 31, so that the upper surface of the screen 20 and the pattern openings 23 This is a step of supplying the paste 31 to at least one. The screen printing method of the present invention is characterized in that ultrasonic vibration is applied to at least a part of the paste 31 in the paste supplying step. The paste 31 has thixotropy. Therefore, in the paste supplying step, the viscosity of the paste 31 can be temporarily reduced by applying ultrasonic vibration. As a result, even when the high-viscosity paste 31 is used, the paste 31 can be more uniformly applied on the screen 20, and the paste 31 is filled into the pattern openings 23 of the screen 20 prior to the next printing step. can do. That is, even when the pattern opening 23 is a fine pattern by applying ultrasonic vibration to the paste 31, the paste 31 having a reduced viscosity due to thixotropy can easily enter the pattern opening 23. The pattern opening 23 can be filled with 31.

  Application of ultrasonic vibration to the paste 31 can be performed using the above-described ultrasonic vibration application mechanism. In the paste supply process shown in FIG. 1, an example is shown in which an ultrasonic vibration application mechanism in which the ultrasonic vibration source 11 is connected to the scraper 15 is used. In the paste supply step shown in FIG. 1, the squeegee 10 is in the upper position and the scraper 15 is in the lower position. At this time, the scraper 15 and the screen 20 may be in contact with each other, or may be in close proximity with a slight gap.

  In the paste supply step shown in FIG. 1, the scraper 15 moves while contacting the paste 31 in the direction indicated by reference numeral 51. At this time, when a gap is provided between the upper surface of the screen 20 and the lower end of the scraper 15, a part of the paste 31 that is pushed and carried by the scraper 15 remains on the screen 20 from the gap. The paste 31 can be supplied to the upper surface of the screen 20 and at least a part of the pattern opening. Further, even when the scraper 15 and the screen 20 are in contact with each other, the upper surface of the screen 20 is a mesh, so that the paste 31 is supplied to at least a part of the upper surface of the screen 20 and the pattern opening. be able to.

  Further, in the paste supplying step, since the ultrasonic vibration generated by the ultrasonic vibration source 11 is applied to at least a part of the paste 31, the viscosity of the paste 31 decreases due to the thixotropy of the paste 31. In the example of FIG. 1, since the ultrasonic vibration source 11 is connected to the scraper 15, the ultrasonic vibration generated by the ultrasonic vibration source 11 can be applied to the paste 31 via the scraper 15. . Therefore, prior to the printing process, the paste 31 can be more uniformly applied on the screen 20, and the paste 31 can be filled into the pattern openings 23 of the screen 20.

  The screen printing method of the present invention includes a printing process after the paste supplying process. The printing process is a process in which the paste 31 is printed on the printing medium 30 through the pattern opening 23 of the screen 20 by the squeegee 10 moving on the screen 20 while being pressed and pressed. A printing pattern 32 (printed paste) can be formed on the surface of the substrate 30 by the printing process.

  FIG. 2 is a schematic sectional view of a part of the screen printing apparatus for explaining an example of the printing process. The printing process shown in FIG. 2 is a printing process after the paste supplying process shown in FIG. In the printing process shown in FIG. 2, the squeegee 10 is in the lower position and the scraper 15 is in the upper position. In the printing step, the paste 31 is printed on the printing medium 30 through the pattern opening 23 of the screen 20 by moving in the direction of the arrow 50 in FIG. Can do. As described above, since ultrasonic vibration is applied to the paste 31 in the paste supplying step, the paste 31 on the upper surface of the screen 20 is uniform and the pattern opening 23 is filled with the paste 31 well. Therefore, when the squeegee 10 contacts and presses on the screen 20, the paste 33 in the pattern opening 23 adheres to the surface of the printing medium 30 and can be easily detached from the pattern opening 23. In addition, it is possible to form the printed pattern 32 having an excellent shape with a high aspect ratio with respect to the printing medium 30. Note that the pressure of pressing the screen 20 by the squeegee 10 is appropriately selected depending on printing conditions such as paste viscosity and squeegee speed. Specifically, at least the back surface of the screen 20 is in contact with the surface of the printing medium 30. Any pressure can be used.

  In the printing process shown in FIG. 2, since the scraper 15 is in the upper position, the case where ultrasonic vibration is not applied to the paste 31 is shown. However, if necessary, the scraper 15 can be arranged at a position that does not contact the screen 20 but contacts the paste 31 and applies ultrasonic vibration to the paste 31 during the printing process. . Similarly, also in the printing process shown in FIGS. 4 and 6 to be described later, ultrasonic vibration can be applied to the paste 31 during the printing process, if necessary.

  3 and 4 are schematic cross-sectional views for explaining the screen printing method of the present invention in which application of ultrasonic vibration to the paste 31 is performed through the squeegee 10. FIG.

  FIG. 3 shows a paste supplying step of the screen printing method of the present invention. In the paste supplying step shown in FIG. 3, an ultrasonic vibration application mechanism in which the ultrasonic vibration source 11 is connected to the squeegee 10 is used. In the paste supply step shown in FIG. 3, the scraper 15 is in the lower position. Further, although the squeegee 10 is in the upper position, the squeegee 10 is positioned so as to be in the paste 31 during the paste supplying step. In the paste supplying step shown in FIG. 3, the scraper 15 moves in the direction indicated by reference numeral 51. By generating ultrasonic vibration from the ultrasonic vibration source 11 during the paste supplying step, the ultrasonic vibration can be applied to the paste 31 via the squeegee 10.

  FIG. 4 is a schematic sectional view of a part of the screen printing apparatus for explaining an example of the printing process. The printing process shown in FIG. 4 is a printing process after the paste supply process shown in FIG. In the printing process shown in FIG. 4, the squeegee 10 is in the lower position and the scraper 15 is in the upper position. In the printing step, the paste 31 can be printed on the printing medium 30 through the pattern opening 23 of the screen 20 by the squeegee 10 moving on the screen 20 while being pressed. As described above, since ultrasonic vibration is applied to the paste 31 in the paste supplying step, the paste 31 on the upper surface of the screen 20 is uniform and the pattern opening 23 is filled with the paste 31 well. Therefore, when the squeegee 10 contacts and presses on the screen 20, the paste 33 in the pattern opening 23 adheres to the surface of the printing medium 30 and can be easily detached from the pattern opening 23. In addition, it is possible to form the printed pattern 32 having an excellent shape with a high aspect ratio with respect to the printing medium 30.

  5 and 6 are schematic sectional views for explaining the screen printing method of the present invention in which application of ultrasonic vibration to the paste 31 is performed through the resonator 12.

  FIG. 5 shows a paste supplying step of the screen printing method of the present invention. In the paste supplying step shown in FIG. 5, an ultrasonic vibration applying mechanism in which the ultrasonic vibration source 11 is connected to the resonator 12 as a further component is used. The resonator 12 can be disposed in front of the moving direction of the scraper 15 in the paste supplying step. In the paste supply process shown in FIG. 5, the scraper 15 is in the lower position and the squeegee 10 is in the upper position. In addition, the resonator 12 is disposed at a position where at least a part of the resonator 12 is in the paste 31 during the paste supplying step. In the paste supplying step shown in FIG. 5, the scraper 15 moves in the direction indicated by reference numeral 51. Therefore, ultrasonic vibration can be applied to the paste 31 via the resonator 12 by generating ultrasonic vibration from the ultrasonic vibration source 11 during the paste supplying step.

  FIG. 6 is a schematic cross-sectional view of a part of the screen printing apparatus for explaining an example of the printing process. The printing process shown in FIG. 6 is a printing process after the paste supply process shown in FIG. In the printing process shown in FIG. 6, the squeegee 10 is in the lower position and the scraper 15 is in the upper position. In the printing step, the paste 31 can be printed on the printing medium 30 through the pattern opening 23 of the screen 20 by the squeegee 10 moving on the screen 20 while being pressed. As described above, since ultrasonic vibration is applied to the paste 31 in the paste supplying step, the paste 31 on the upper surface of the screen 20 is uniform and the pattern opening 23 is filled with the paste 31 well. Therefore, when the squeegee 10 contacts and presses on the screen 20, the paste 33 in the pattern opening 23 adheres to the surface of the printing medium 30 and can be easily detached from the pattern opening 23. In addition, it is possible to form the printed pattern 32 having an excellent shape with a high aspect ratio with respect to the printing medium 30.

  In the example shown in FIGS. 5 and 6, the resonator 12 moves up and down in synchronization with the scraper 15. However, the holding portion of the resonator 12 does not necessarily have a mechanism that can move up and down. That is, the holding portion of the resonator 12 is configured to fix the resonator 12 at a predetermined distance from the upper surface of the screen 20 so that at least a part of the resonator 12 is in the paste 31 during the paste supplying process. Can have. The holding portion of the resonator 12 has a structure in which the resonator 12 moves up and down independently of the scraper 15, and the resonator 12 contacts the screen 20 in the printing process, and ultrasonic vibration is applied to the screen 20. It can also be a structure that can.

  1 to 6 show an example in which the squeegee 10 moves in the printing direction in the printing process, and the scraper 15 moves in the direction opposite to the printing direction in the paste supplying process. However, the movement direction of the squeegee 10 and the scraper 15 is any direction as long as it satisfies the feature of the present invention that the ultrasonic vibration is applied to the paste 31 in the paste supplying step. Also good. Moreover, the moving directions of the squeegee 10 and the scraper 15 can be the same or different. Further, the squeegee 10 and the scraper 15 are not necessarily moved at the same time, and may be moved at different timings. The same applies to the resonator 12.

  In the screen printing method of the present invention, a known screen 20 can be used. In general, the screen 20 has a structure in which an emulsion (emulsion) is attached on a metal mesh or the like, and a portion of the emulsion corresponding to the shape of the print pattern 32 is removed to form a pattern opening 23. By passing the paste 31 through the pattern opening 23, a predetermined print pattern 32 can be printed on the printing medium 30. In the screen printing method of the present invention, when screen printing is performed, the screen 20 is disposed so that the emulsion of the screen 20 and the printing material 30 face each other.

  In the screen printing method of the present invention, a known squeegee 10 can be used. As a material for the squeegee 10, rubber compositions such as urethane rubber and silicone rubber, metal materials, and the like can be used. Since the angle at which the squeegee 10 contacts the screen 20 (squeegee angle) affects the screen printing performance, it is preferable to select an optimum squeegee angle.

  The speed at which the squeegee 10 moves on the screen 20 (squeegee speed) also affects the screen printing performance. In the off-contact type screen printing method, the plate can be separated (the screen 20 is separated from the printing medium 30) almost simultaneously with the printing of the paste 31, so that the squeegee speed is about 100 to 300 mm / second. Printing can be performed.

  As the ultrasonic vibration source 11 used in the screen printing method of the present invention, a known one can be used. In the screen printing method of the present invention, since the attachment position of the ultrasonic vibration source 11 is limited, it is preferable to use a relatively compact Langevin type vibrator. A Langevin type vibrator is an element that generates ultrasonic vibrations by applying an alternating voltage at a resonance frequency to piezoelectric ceramics such as barium titanate or PZT (lead zirconate titanate). Many types are used. The Langevin type vibrator used in the ultrasonic vibration source 11 used in the screen printing method of the present invention in order to stably generate high-energy ultrasonic vibration is a vibrator containing lead zirconate titanate as piezoelectric ceramics. Preferably there is.

  Further, the ultrasonic vibration source 11 used in the screen printing method of the present invention preferably has a frequency of generated ultrasonic vibration of 10 KHz to 3 MHz, and more preferably 15 KHz to 100 MHz. This is because when the frequency of the ultrasonic vibration is in such a range, the viscosity change of the paste 31 occurs effectively.

  Further, in the screen printing method of the present invention, when applying the ultrasonic vibration generated by the ultrasonic vibration source 11 to at least a part of the paste 31, the ultrasonic vibration generated by the ultrasonic vibration source 11 is It is preferable that transmission is performed to the resonator 12 that resonates with the ultrasonic vibration, and the ultrasonic vibration resonated in the resonator 12 is transmitted to at least a part of the paste 31. By using the resonator 12, the ultrasonic vibration generated by the ultrasonic vibration source 11 can be more effectively applied to the paste 31 on the screen 20 and the pattern opening 23 of the screen 20. As a result, the viscosity of the paste 31 can be reduced more effectively.

  The resonator 12 is also called a horn, and the amplitude of the ultrasonic vibration generated in the ultrasonic vibration source 11 can be increased by the resonator 12 having an appropriate resonance frequency. FIG. 7 is a schematic perspective view of the resonator 12. In order to connect the ultrasonic vibration source 11 to the resonator 12, the resonator 12 has at least one ultrasonic vibration source connection hole 14. By connecting a plurality of ultrasonic vibration sources 11 to the resonator 12, sufficient ultrasonic vibration can be supplied. FIG. 8 is a schematic cross-sectional view in which the ultrasonic vibration source 11 is connected to the resonator 12.

  In the screen printing method of the present invention, it is preferable to use the resonator 12 as the scraper 15 when applying ultrasonic vibration to the paste 31 via the scraper 15.

  In the screen printing method of the present invention, when ultrasonic vibration is applied to the paste 31 via the squeegee 10, it is preferable to use a structure in which the squeegee 10 is attached to the resonator 12. In this case, as shown in a schematic cross-sectional view in FIG. 9, a squeegee 10 having a structure in which the squeegee 10 is attached to the resonator 12 to which the ultrasonic vibration source 11 is connected can be used. Further, as shown in the schematic cross-sectional view of FIG. 10, the squeegee 10 may have a structure in which the squeegee 10 is attached only to the corner that contacts the screen 20 in the printing process.

  According to the screen printing method of the present invention, the shape (printing shape) of the paste 32 printed on the substrate 30 can be obtained with an aspect ratio of 0.3 or more. The aspect ratio is a value obtained by dividing the height of the printed shape by the line width.

  In the screen printing method of the present invention, the paste 31 preferably has a viscosity of 300 to 1000 Pa · s when measured at 25 ° C. and 10 rpm. When the viscosity of the paste 31 is in such a range, when the printing method of the present invention is used, it is possible to obtain both a good plate slip-off property and a high aspect ratio printed shape.

  Next, the paste 31 that is preferably used in the screen printing method of the present invention will be described.

  In the screen printing method of the present invention, the paste 31 preferably contains 85 to 95% by weight of inorganic particles, 1 to 5% by weight of a binder, and 1 to 7% by weight of a solvent. When the paste 31 has such a composition, when the printing method of the present invention is used, it is possible to surely obtain both good plate loss and a high aspect ratio printed shape. Hereinafter, a specific composition of the paste 31 will be described by taking a surface electrode forming paste of a solar cell as an example. In addition, in FIG. 11, the cross-sectional schematic diagram of the structure of the electrode vicinity of a solar cell is illustrated. In the example shown in FIG. 11, the solar cell has a structure having a surface electrode 1, an antireflection film 2, a substrate 6 having an n-type diffusion layer 3 and p-type silicon 4, and a back electrode 5.

  The paste for forming a surface electrode of a solar cell can contain conductive particles and glass frit as inorganic particles.

  The conductive particles contained in the paste for forming a surface electrode of a solar cell need to have an appropriate metal type, particle size, particle shape, and particle surface state (presence or absence of surface treatment). In order to form a surface electrode of a solar cell whose main material is silver, the conductive particles contained in the conductive paste are particles whose main material is silver, specifically, particles containing 50% by weight or more of silver. It is preferable that In addition, the conductive paste can contain other metal particles other than silver particles as long as the performance of the surface electrode is not impaired. However, since silver has a low electric resistance and is excellent as a solar cell electrode material, the conductive particles are preferably made of silver.

  It is preferable that the conductive particles have a predetermined particle shape and particle size. That is, in the electrode of the solar cell of the present invention, the conductive particles can be scale-like or spherical, and a mixture thereof can be used. Further, fine particles having a particle size of several μm or less can be used.

  Specifically, as the conductive particles, scaly silver particles having a long particle size of 5 to 10 μm and a short particle size of 2 to 5 μm can be used. The long particle size refers to the length of the longest straight line among the straight lines connecting any two points in the projected view having the maximum area among the projected views in which the shape of the particle is projected onto a plane. Further, the short particle diameter means the length of the longest straight line among straight lines connecting arbitrary two points of the contours of the projections of the particles and orthogonal to a straight line indicating the long particle diameter. For example, when the shape of the particle is an elliptical thin flat plate, the projection with the maximum area is an ellipse, so the long particle size means the length of the major axis of the ellipse (major axis), The particle diameter means the length of the minor axis of the ellipse (minor axis).

  The conductive particles can be used by mixing spherical silver particles having an average particle diameter of 0.1 μm with scale-like silver particles. In addition, an average particle diameter is calculated | required as a value of the particle size (D50) of the integrated value 50% of all the particles. In the present specification, the “average particle diameter” is the same for particles other than silver particles.

  As inorganic particles of the paste for forming the surface electrode of the solar cell, glass frit can be further contained. In order to obtain predetermined solar cell characteristics, it is necessary to make the composition, softening temperature, particle size, and particle shape of the glass frit appropriate.

As the glass frit contained in the conductive paste, one having a composition corresponding to the glass frit constituting the electrode can be used. That is, the glass frit contained in the conductive paste is composed of PbO—SiO ₂ —B ₂ O ₃ system, Bi ₂ O ₃ —PbO—SiO ₂ —B ₂ O ₃ system, and ZnO—SiO ₂ —B ₂ O ₃ system. It can be at least one selected. The glass frit is a Pb-free glass frit (for example, Bi ₂ O ₃ —B ₂ O ₃ —SiO ₂ —CeO ₂ —LiO ₂ —NaO ₂ or SiO ₂ —B ₂ O ₃ —Li ₂ O). Can be. As the glass frit, a glass frit containing zinc oxide and boron oxide and further containing one selected from SiO ₂ , CeO ₂ , LiO ₂ and NaO ₂ can be used.

  The particle shape and particle size of the glass frit particles need to be predetermined as in the case of the conductive particles. However, in general, the amount of conductive particles added is much larger than the amount of glass frit particles added. Therefore, in order to obtain a solar cell with good performance, the size and shape of the conductive particles are set to a predetermined value. It is important to be. Specifically, for the glass frit particles, for example, an amorphous particle shape can be used. The particle diameter is preferably 0.01 to 50 μm, more preferably 0.05 to 20 μm, and particularly preferably 0.1 to 5 μm from the viewpoint of workability.

  The paste for forming a surface electrode of a solar cell can contain an organic binder as a binder. As the organic binder, those selected from cellulose resins (for example, ethyl cellulose and nitrocellulose) and (meth) acrylic resins (for example, polymethyl acrylate and polymethyl methacrylate) can be used. The addition amount of the organic binder is usually 0.5 to 30 parts by weight, preferably 1 to 7 parts by weight with respect to 100 parts by weight of the conductive particles.

  Examples of the solvent contained in the paste for forming the surface electrode of the solar cell include alcohols (for example, terpineol, α-terpineol, β-terpineol, etc.), esters (for example, hydroxy group-containing esters, 2,2,4-trimethyl-1). , 3-pentanediol monoisobutyrate and butyl carbitol acetate, etc.) can be used. The addition amount of the solvent is usually 0.5 to 30 parts by weight, preferably 1 to 25 parts by weight with respect to 100 parts by weight of the conductive particles.

  Furthermore, the paste for forming the surface electrode of the solar cell may be blended with additives selected from plasticizers, antifoaming agents, dispersants, leveling agents, stabilizers, adhesion promoters, and the like as necessary. it can. Among these, as the plasticizer, phthalic acid esters, glycolic acid esters, phosphoric acid esters, sebacic acid esters, adipic acid esters, and citrate esters can be used.

  Next, a surface electrode forming paste for a solar cell that is preferably used in the screen printing method of the present invention will be described.

  As the conductive particles contained in the paste for forming a surface electrode of a solar cell that is preferably used in the screen printing method of the present invention, spherical silver particles having an average particle diameter of 0.1 μm can be used.

  As a binder contained in the paste for forming a surface electrode of a solar cell which is preferably used in the screen printing method of the present invention, ethyl cellulose can be used. Moreover, butyl carbitol acetate can be used as a solvent.

PbO—SiO ₂ —B ₂ O ₃ -based glass can be used as the glass frit contained in the paste for forming a surface electrode of a solar cell that is preferably used in the screen printing method of the present invention. The glass frit may have an amorphous particle shape. Moreover, an average particle diameter of 0.1-5 micrometers can be used.

  The composition of the paste for forming a surface electrode of a solar cell that is preferably used in the screen printing method of the present invention is 85 to 95% by weight of inorganic particles made of conductive particles or glass frit, 1 to 3% by weight of a binder, and 1 to 7 of a solvent. It is preferable that it is the ratio of weight%. Moreover, it is preferable that the viscosity range of the paste for surface electrode formation of a preferable solar cell is 300 to 1000 Pa · s when measured at 25 rpm and 10 rpm.

  The paste for forming a surface electrode of a solar cell preferably used in the screen printing method of the present invention can be made into a paste by stirring and dispersing the above materials with a planetary mixer and three rolls. The paste thus obtained is higher than the viscosity of a general paste (300 Pa · s or less under the same conditions as described above), but is suitable for forming a high aspect ratio print pattern of the present invention.

  The paste for forming a surface electrode of a solar cell that is preferably used in the screen printing method of the present invention has a viscosity of 300 to 500 Pa · s measured at a temperature of 25 ° C. and a rotation speed of 10 rpm using a 3 ° cone in an E-type viscometer. As a preferable paste for forming a surface electrode of a solar cell, a paste having a thixo index (TI value) of about 1 to 1/10 rpm can be used. Here, the thixo index (TI value) is an index indicating the thixotropy. The thixo index (TI value) is the ratio of viscosities measured at different rotational speeds. The viscosity is measured at 25 ° C. using a Brookfield viscometer (E type viscometer) and using a 3 ° cone. In the present specification, for example, the thixo index (TI value) can be obtained as a ratio of viscosity measured at two selected rotational speeds such as 0.5 rpm / 2.5 rpm, 1 rpm / 10 rpm, 5 rpm / 50 rpm, and the like. The above-mentioned “0.5 rpm / 2.5 rpm” means a value (thixo index) obtained by dividing the viscosity measurement value at a rotation speed of 0.5 rpm by the viscosity measurement value at a rotation speed of 2.5 rpm.

  By the screen printing method of the present invention, an electrode, an electrode terminal, a wiring, and / or a partition can be formed on an electronic device or a circuit board in a shape with a high aspect ratio. That is, the electrodes, electrode terminals, wirings, and / or partitions on the electronic device or circuit board are preferably formed by the screen printing method of the present invention.

  Moreover, it is preferable that the electronic device in which an electrode etc. are formed by the screen printing method of this invention is a solar cell, a chip inductor, electronic paper, or a plasma display panel. The circuit board on which electrodes and the like are formed by the screen printing method of the present invention is preferably an electronic device or a circuit board that is a printed board or a ceramic board.

  In order to improve the conversion efficiency of the solar cell, the surface electrode of the solar cell must have a fine shape with a high aspect ratio. Therefore, the screen printing method of the present invention can be preferably used for forming a surface electrode of a solar cell.

<Example 1>
A horn (resonator) with a vibrator was attached in front of the scraper position of the screen printing apparatus, and screen printing was performed by the screen printing method of the present invention.

  The aluminum block is cut into the shape shown in FIG. 7 to produce a horn (resonator) having a height (H) of 50 mm, a width (L) of 50 mm, an upper thickness (D1) of 10 mm, and a horn tip thickness (D2) of 6 mm. did. One Langevin type vibrator that vibrates at 50 KHz was attached to a 10 mm thick portion at the top of the horn. As shown in FIGS. 5 and 6, the vibrator-equipped horn was installed in front of the scraper so as to be close to the screen. The scraper was brought into contact with the screen in the paste supplying step.

  In order to confirm the effect of applying ultrasonic vibration in the paste supplying step, ultrasonic vibration having a vibration frequency of 50 KHz and an amplitude of about 20 μm is applied to at least one of the upper surface of the screen and the pattern opening while applying vibration to the paste through a horn. The paste was supplied to the part with a scraper. Thereafter, a paste for solar cell (manufactured by NAMICS) was printed on a mirror-polished p-type silicon substrate. For comparison, the paste was supplied and printed without applying any ultrasonic vibration.

  The shape of the pattern opening of the screen used was 5 types of length 50 mm and width 120 μm, 100 μm, 80 μm, 50 μm and 30 μm. After the paste was printed on the substrate and dried at 150 ° C. for 1 minute, the aspect ratio of the printed shape was measured.

Screen printing was performed under the following printing conditions.
Screen emulsion thickness: 20-30 μm
(The screen emulsion thickness was 30 μm in the case of 120 μm, 100 μm and 80 μm wide pattern openings. The screen emulsion thickness was 20 μm in the case of 50 μm and 30 μm wide pattern openings.)
Screen mesh: 325 mesh Screen mesh wire diameter: φ23μm
Printing speed: 100 mm / sec Squeegee angle: 70 degrees Distance between substrate and screen: 1.5 mm
Paste viscosity: 400 Pa · s (measured at 10 rpm), 170 Pa · s (measured at 50 rpm)

  Table 1 shows the print shape of the printed pattern on the substrate as a result of screen printing under the above conditions.

  From this result, it can be seen that when the paste is supplied while applying ultrasonic vibration and the pattern opening is filled, the printing width is slightly increased, but the effect of improving the plate slippage and leveling is improved. It was confirmed that a fine line with less surface irregularities can be obtained by the ratio.

<Example 2>
Next, in order to form the surface electrode of a solar cell, the Example using the screen printing method of this invention is shown. FIG. 11 shows a schematic cross-sectional view of the structure of a prototype solar cell. This schematic cross-sectional view shows the structure near the electrode.

  The application of ultrasonic vibration during screen printing for forming the surface electrode was performed in the same manner as in Example 1. The application conditions of ultrasonic vibration are the same as in the first embodiment.

As the solar cell substrate, a p-type polycrystalline substrate having a square of 156 mm on a side and a thickness of 220 μm was used. A texture structure (uneven structure) is provided on one side (surface) of the substrate by alkali etching, POCl ₃ is applied to the surface in order to use phosphorus as a diffusion source, and phosphorus is thermally diffused at 1000 ° C. for 30 minutes. A mold diffusion layer was formed. Thereafter, a silicon nitride (SiN) film having a thickness of about 70 nm as an antireflection film was formed on the surface by plasma CVD.

  Next, as in the first embodiment, as shown in FIG. 5, at least a part of the upper surface of the screen and the pattern opening are applied while applying ultrasonic vibrations to the paste through a horn installed in front of the scraper. Then, as shown in FIG. 6, the solar cell surface electrode pattern was printed on the antireflection film of the substrate without applying ultrasonic vibration. The surface electrode screen had a finger width (pattern opening width) of 80 μm. A squeegee having a width of 190 mm was used. The horn (resonator) used in front of the scraper was the same size as the horn used in Example 1 except that the width (L) was 190 mm. As a paste for forming the surface electrode, a silver paste for solar cells (viscosity: 400 Pa · s) manufactured by NAMICS was used.

  After printing the surface electrode pattern, it was dried at a temperature of 150 ° C. for 1 minute using a far infrared fixed furnace. Next, an aluminum paste manufactured by Namics Co., Ltd. was printed on the entire back surface of the substrate as a back electrode, and dried at a temperature of 150 ° C. for 1 minute. The back electrode pattern was printed using a conventional screen printing method without applying ultrasonic vibration. This is because it is not necessary to provide a fine pattern on the back electrode pattern.

  Next, the substrate was baked at 800 ° C. for about 1 minute using a near-infrared furnace using a halogen lamp as a heat source, so that the front electrode and the back electrode were simultaneously baked to form both electrodes.

  As Comparative Example 2, when the surface electrode pattern of the solar cell was printed on the antireflection film of the substrate, the paste having a paste viscosity of 180 Pa · s used in normal solar cell electrode formation was used, and the paste was supplied A solar cell was manufactured in the same manner as in Example 2 except that no ultrasonic vibration was applied during the process.

The solar cell characteristics were measured by irradiating with 100 mW / cm ² of solar simulator light (AM1.5). In each of the examples and comparative examples, 10 solar cells were produced. The solar cell characteristics were compared by means of a curve factor (FF, [Fill Factor]) that can be obtained from measurement of current-voltage characteristics of the solar cell and an average value of conversion efficiency. The results are shown in Table 2.

  From the results shown in Table 2, when the screen printing method of the present invention is used, non-uniformity in film thickness caused by finger disconnection or poor leveling is reduced as compared with the case of normal printing conditions. As a result, it was clarified that a decrease in fill factor (FF) can be suppressed and high conversion efficiency can be realized.

<Example 3>
On a ferrite sheet having a side of 150 mm and a thickness of 200 μm, a rectangular coil-shaped pattern (4 turns, outer shape of about 1.5 mm square) having a line width of 60 μm and a space of 60 μm between lines was screen-printed. The coil-shaped pattern was printed using silver paste for chip inductors (manufactured by NAMICS, viscosity of 300 Pa · s). After screen printing, drying was performed at 150 ° C. for 1 minute.

  Note that the application of ultrasonic vibration during screen printing is similar to the first embodiment, as shown in FIG. 5, while applying ultrasonic vibration to the paste via a horn placed in front of the scraper. After supplying the paste to at least a part of the pattern opening, screen printing was performed without applying ultrasonic vibration as shown in FIG. 6 (Example 3). The application conditions of ultrasonic vibration are the same as in the first embodiment. For comparison, a coiled pattern was printed in the same manner as in Example 3 except that no ultrasonic vibration was applied during the paste supplying step (Comparative Example 3).

  The screen printing frequency was 1, 5, 10, 15, 25, and 30 times, and the printed shape of the printed pattern after drying was observed for each printing frequency.

  The results are shown in Table 3. “X” and “◯” in Table 3 indicate “x” when the line in the direction perpendicular to the printing direction (moving direction of the squeegee) is conducted, and when not conducting. Was determined to be “◯”. In the example of the present invention, even when the number of screen printings exceeded 15, the coil pattern could still be screen printed. Further, the smoothness of the printed coil surface could be improved by the effect of applying ultrasonic vibration in the method of the present invention.

  From the above results, it was confirmed that a fine coil shape can be stably obtained by the screen printing method of the present invention.

<Example 4>
Using a metal mask (SUS304, thickness 50 μm, 100 openings 0.1 × 0.1 mm) on a copper-clad printed circuit board, cream solder was screen-printed to compare the plate release characteristics.

  A eutectic solder powder of Pb: Sn = 37: 63 was used as the solder powder contained in the cream solder. As the average particle size of the solder powder, a slightly larger 30 μm was used, which is not good for detaching the plate. The printed pattern was dried after screen printing. The shape of the printed pattern was observed with an optical microscope. The evaluation was performed by comparing the number of plate missing defects per 100 printing patterns.

  Note that the application of ultrasonic vibration during screen printing is the same as in Example 1, as shown in FIG. 5, while applying ultrasonic vibration to the paste through a horn, at least the upper surface of the metal mask and the pattern opening. Part of the paste was supplied with a scraper. Thereafter, screen printing was performed without applying ultrasonic vibration (Example 4). The application conditions of ultrasonic vibration are the same as in the first embodiment. For comparison, a printing pattern was printed in the same manner as in Example 4 except that no ultrasonic vibration was applied during the paste supplying process (Comparative Example 4).

  Table 4 shows the results of Example 4. From this result, it has been found that the screen printing method of the present invention improves the plate slippage and enables printing of a fine print pattern.

It is a cross-sectional schematic diagram of a part of the screen printing apparatus for explaining an example of the paste supplying step of the screen printing method of the present invention. It is a partial cross section schematic diagram of a screen printing apparatus for explaining an example of a printing process of the screen printing method of the present invention. It is a partial cross section schematic diagram of a screen printing apparatus for demonstrating another example of the paste supply process of the screen printing method of this invention. It is a cross-sectional schematic diagram of a part of the screen printing apparatus for explaining another example of the printing process of the screen printing method of the present invention. It is a partial cross-sectional schematic diagram of the screen printing apparatus for demonstrating another example of the paste supply process of the screen printing method of this invention. It is a partial cross-sectional schematic diagram of the screen printing apparatus for demonstrating another example of the printing process of the screen printing method of this invention. It is a perspective schematic diagram of the resonator (horn) used for the screen printing method of the present invention. It is the cross-sectional schematic diagram which connected the ultrasonic vibration source to the resonator. It is a cross-sectional schematic diagram of the squeegee of the structure where the squeegee was attached to the resonator which connected the ultrasonic vibration source. It is a cross-sectional schematic diagram of the squeegee of the structure where the squeegee was attached to the resonator which connected the ultrasonic vibration source. It is a cross-sectional schematic diagram of the electrode vicinity of a solar cell.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Front surface electrode 2 Antireflection film 3 N type diffused layer 4 P type silicon 5 Back surface electrode 6 Substrate 10 Squeegee 11 Ultrasonic vibration source 12 Resonator (horn)
14 Ultrasonic vibration source connection hole 15 Scraper 20 Screen 23 Pattern opening 30 Substrate 31 Paste 32 Print pattern (printed paste)
33 Paste in pattern opening 40 Printing stand 50 Moving direction of squeegee in printing process 51 Moving direction of scraper in paste supplying process

Claims (14)

Supplying the paste to at least a part of the upper surface of the screen and the pattern opening by moving the scraper on the screen having the pattern opening while applying ultrasonic vibration to at least a part of the paste;
And a step of printing a paste on a printing medium through a pattern opening of the screen by moving the squeegee on the screen while pressing and pressing the screen.   The screen printing method according to claim 1, wherein the ultrasonic vibration is applied to the paste through a resonator disposed in front of the moving direction of the scraper in the step of supplying the paste.   The screen printing method according to claim 1, wherein ultrasonic vibration is applied to the paste through a scraper.   The screen printing method according to claim 1, wherein ultrasonic vibration is applied to the paste through a squeegee.   The squeegee moves in the printing direction in the step of printing the paste on the substrate, and the scraper moves in the direction opposite to the printing direction in the step of supplying the paste. Screen printing method.   The screen printing method according to claim 1, wherein the frequency of ultrasonic vibration is 10 KHz to 3 MHz.   The screen printing method according to claim 1, wherein the ultrasonic vibration source is a Langevin type vibrator.   The screen printing method according to claim 7, wherein the Langevin type vibrator is a vibrator containing lead zirconate titanate.   The screen printing method according to claim 1, wherein the paste has a viscosity of 300 to 1000 Pa · s when measured at 25 ° C. and 10 rpm.   The screen printing method according to claim 1, wherein the paste contains 85 to 95 wt% inorganic particles, 1 to 5 wt% binder, and 1 to 7 wt% solvent. A squeegee for printing the paste on the printing material by moving while contacting and pressing on the screen, a scraper for supplying the paste to the upper surface of the screen and the pattern opening by moving on the screen, and ultrasonic vibration A screen printing apparatus including an ultrasonic vibration applying mechanism for applying at least a part of the paste,
The structure in which the ultrasonic vibration application mechanism includes an ultrasonic vibration source, the ultrasonic vibration source is connected to the scraper, the structure in which the ultrasonic vibration source is connected to the squeegee, or the moving direction of the scraper when the ultrasonic vibration source supplies the paste The screen printing apparatus which has at least 1 structure of the structure connected to the resonator arrange | positioned ahead of.   The screen printing apparatus used for the screen printing method of any one of Claims 1-10.   The electronic device or circuit board which has an electrode, an electrode terminal, wiring, and / or a partition formed by the screen printing method of any one of Claims 1-12.   The electronic device or circuit board according to claim 13, wherein the electronic device is a solar cell, a chip inductor, electronic paper, or a plasma display panel, and the circuit board is a printed board or a ceramic board.

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