Screen printing method including degassing bubbles in the coating material

ABSTRACT

A screen printing method is carried out by placing a material to be printed at a predetermined portion of a printing table, feeding a paste-state or ink-state coating material to a surface of a screen plate for printing, and sliding the surface of the screen plate relative to a squeegee to carry out screen printing. The above-mentioned paste-state or ink-state coating material is covered on the surface of the screen plate for printing with a thin thickness, and the paste-state or ink-state coating material coated on the surface of the screen plate for printing is printed to a material to be printed by the above-mentioned squeegee under vacuum or atmospheric pressure. After the above-mentioned coating step, a degassing step is provided to degas bubbles in the coated material by changing the pressure from high vaccum state to atmospheric pressure or low vacuum state.

INFORMATION

DETAILED DESCRIPTION OF THE INVENTION

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following, the screen printing method according to the present invention is explained in detail by referring to the drawings.

FIGS. 1A, B, C to FIG. 5 each show the screen printing method according to the present invention. In this embodiment, the present invention is explained by a screen printing method using a screen plate comprising a gauze-adhered plate. This embodiment can be similarly applied to a screen printing by using a stencil such as metal and the like. In FIGS. 1A, B, C, FIGS. 2A, B, and FIGS. 3A and 3B, a single coat screen printing method is shown. A screen printing apparatus has a squeegee for printing provided at above a material to be printed such as a substrate mounted on a platen on which a material to be printed is mounted, and has a scraper for squeezing ink. At a position above the material to be printed such as a substrate, a screen plate comprising a gauze adhered plate attached to a plate frame is provided.

Onto the surface of the above-mentioned screen plate , ink in the form of a paste-state or ink-state coating material is fed, and the above-mentioned squeegee and the scraper are driven in a front and rear direction or a right and left direction by a driving mechanism which is not shown in the drawing. In this embodiment of the present invention, screen printing on the surface of the material to be printed is carried out by sliding the surface of the screen plate in the right and left direction with respect to the above-mentioned squeegee and the scraper .

The above-mentioned screen printing apparatus is contained in a vacuum chamber , and a vacuum pump or valve which is not shown in the figure is connected to the vacuum chamber. The vacuum chamber is set to a low vacuum or a high vacuum (as compared to atmospheric pressure) by opening or closing a lid provided on the vacuum chamber .

An appropriate clearance L is provided between the screen plate and the surface of the material to be printed . At one end of the screen plate , ink in a paste-state or ink-state coating material is supplied from an ink feeding mechanism, and the ink from the ink feeding mechanism forms an ink fountain .

In FIG. 1A, a coating step is shown in which the ink at the ink fountain is coated from the first end side of the screen plate to the second end side by a scraper under atmospheric pressure. This coating is off-contact coating.

As shown in FIG. 1B, after completion of this coating step, a vacuum pump and the like provided at a vacuum chamber is operated, and a lid is opened and closed to change the pressure from a highly vacuum state to an atmospheric pressure or a lower vacuum state whereby a degassing step is carried out to degas bubbles in the ink which is a coating material. In the drawing, vacuum state and atmospheric pressure are schematically shown by opening and closing a lid , and the invention is not limited to only opening and closing the lid , but may be opening and closing of a valve. The above-mentioned high vacuum state is about 0.067 KPa, the low vacuum state is about 90 KPa, and the atmospheric pressure is about 101.3 KPa.

This degassing step of the ink filed at the printed portion of the screen plate and the ink portion spread over with a thin thickness is carried out by generating a higher vacuum state than the atmospheric pressure. Then the higher vacuum state is changed to the atmospheric pressure or a lower vacuum state to progress occurrence and expansion of bubbles under the higher vacuum state. Thereafter, the chamber is set to atmospheric pressure or a lower vacuum pressure. The degassing treatment under the atmospheric pressure or lower vacuum pressure than the higher vacuum pressure can be carried out repeatedly a plural number of times. Incidentally, a time period of the higher vacuum state and the atmospheric pressure state or the lower vacuum state can be optionally set depending on a size of the screen printing apparatus or the type of ink .

As shown in FIG. 1C, after the degassing step, a printing step is carried out. This printing step is carried out by printing ink , which is a paste-state or ink-state coating material coated on the surface of the screen plate for printing (obtained from an ink fountain at the second end of the surface of the screen plate ) is printed by pressing the above- mentioned squeegee to a material to be printed .

This printing step is carried out in a high-vacuum state. Also, the squeegee is moved in a reverse direction with respect to that of the coating step. In this step, ink is transferred to the material to be printed with only the ink being coated with a thin thickness on the screen plate from an ink fountain , and the ink is filled in the screen plate so that clear printing can be done without any oozing.

Incidentally, the step of printing, in which the screen plate for printing arranged the ink fountain is printed by the squeegee , may be applied to contact printing using a metal plate.

As shown FIGS. 2A, B, and FIGS. 3A and 3B, the material to be printed is subjected to screen printing with the next coating step, degassing step, and printing step. As shown in FIG. 2A, the above-mentioned squeegee and scraper are transferred to an ink fountain positioned at the second end of the screen plate . As shown in FIG. 2B, off contact coating (coating without contact) is carried out by moving the scraper from the second end of the screen plate to the first end under atmospheric pressure.

Then, as shown in FIG. 3A, the above-mentioned squeegee and scraper are moved from the first end of the screen plate to the second end , and as mentioned above, the degassing step in which bubbles in the ink which is the coating material is degassed by changing the pressure to a highly vacuum state, and to atmospheric pressure or a lower vacuum pressure is carried out. Then, as shown in FIG. 3B, under high-vacuum conditions, the ink of the screen plate is pressed to the material to be printed by the above- mentioned squeegee to carry out printing.

In FIGS. 4A, B, C and FIG. 5, a double-coating vacuum degassing printing method is shown. After subjecting the material to be coated to the coating step which is the first ink coating step and the degassing step according to the above-mentioned FIGS. () and (), as shown in FIG. (), the second ink coating step is carried out. That is, the coating step is carried out a plural number of times. Incidentally, a plural number of the coating step and a plural number of the degassing step are combined with each other, for example, a plural number of the coating steps and the degassing steps are repeated.

As shown in FIG. 5, a height of the scraper at the time of the second ink coating is set higher than a height of the scraper at the time of the first ink coating (which is the prior coating). That is, the height of the scraper at the first ink coating is A, and the height of the scraper at the second ink coating is B, and B is larger than A as shown. According to this constitution, an amount of the ink at the printing can be made larger so that a decrease in bulk at the time of degassing can be supplemented. Incidentally, in this embodiment, although the height of the scraper at the time of ink coating is made a different height, it may be the same height. When the height is made the same, it has an effect of correcting unevenness in the printing plane.

After completion of the coating step comprising the above- mentioned first ink-coating and the second ink-coating, as shown in FIG. 4B, the squeegee and the scraper are transferred from the first end of the screen plate , and the pressure was changed to a high-vacuum state and atmospheric pressure or a low-vacuum state to carry out the degassing step of degassing bubbles in the ink which is a coating material. Then, as shown in FIG. 4C, the printing step is carried out under the high-vacuum state by pressing the ink of the screen plate by the above-mentioned squeegee to the material to be printed .

As explained above, according to the screen printing method of the first embodiment of the present invention, the method comprises a coating step of covering the paste-state or ink-state coating material on the surface of the screen plate for printing with a thin thickness, and a printing step in which the paste-state or ink-state coating material coated on the surface of the screen plate for printing is printed on a material to be printed by the above-mentioned squeegee under vacuum or atmospheric pressure. After the above-mentioned coating step, a degassing step is provided to degas bubbles in the coated material by changing the pressure from a high-vacuum state to atmospheric pressure or a low-vacuum state, so that degassing can be carried out from the paste-state or ink-state coating material before printing, occurrence of unevenness on the surface of the printing surface due to the effect of bubbles split at the surface of the printed resin encapsulating portion can be minimized, an amount or a thickness of the paste-state or ink-state coating materials to be printed can be made uniform, and screen printing of high quality and high performance can be carried out.

Also, according to the screen printing method of the second embodiment of the present invention, a paste-state or ink-state coating material is coated on the surface of the screen plate for printing with a thin thickness, and the paste-state or ink-state coating material coated on the surface of the screen plate for printing (which is obtained from an ink fountain at a side of a first edge of the surface of the screen plate in the coating step) is printed by the above-mentioned squeegee in a vacuum or atmospheric pressure. Therefore, an amount or a thickness of the paste state or ink state coating materials to be printed can be made uniform, screen printing of high quality and high performance can be carried out, attachment of a coating material to an unintentional portion of the surface of a material to be printed by migrating the coating material from a pore portion of the stencil to the back surface side of the stencil can be prevented, and excessive printing material, or attachment of a coating material to a portion other than a desired portion of the material to be printed or causing oozing, can be prevented.

Also, according to the screen printing method of the third embodiment of the present invention, it comprises a coating step of covering a paste-state or ink-state coating material on the surface of the screen plate for printing with a thin thickness, and a printing step in which the paste-state or ink-state coating material coated on the surface of the screen plate for printing (obtained from an ink fountain at an end of the surface of the screen plate in the coating step) is printed by the above-mentioned squeegee in a vacuum or atmospheric pressure. After the above-mentioned coating step, a degassing step is performed to degas bubbles in the coated material by changing the pressure from a high-vacuum state to atmospheric pressure or a low-vacuum state, so that degassing can be carried out from the paste-state or ink-state coating material before printing, occurrence of unevenness on the surface of the printing surface due to the effect of bubbles split at the surface of the printed resin encapsulating portion can be minimized, an amount or a thickness of the paste-state or ink-state coating materials to be printed can be made uniform, screen printing of high quality and high performance can be carried out, attachment of a coating material to an unintentional portion of the surface of a material to be printed by migrating the coating material from a pore portion of the stencil to the back surface side of the stencil can be prevented, and an excessive printing material being printed to the material to be printed from a screen plate, or attachment of a coating material to a portion other than a desired portion of the material to be printed or causing oozing, can be prevented.

Also, according to the screen printing method of the fourth embodiment of the present invention, a paste-state or ink-state coating material is covered on the surface of the screen plate for printing with a thin thickness, and a printing step in which the paste-state or ink-state coating material coated on the surface of the screen plate for printing (obtained from an ink fountain at an end of the surface of the screen plate in the coating step) is printed by the above-mentioned squeegee in a vacuum or atmospheric pressure. After completion of the above- mentioned coating step and before the printing step, a degassing step is performed to degas bubbles in the coated material by changing the pressure from a high-vacuum state to atmospheric pressure or a low-vacuum state, and the printing step is carried out in vacuum atmosphere. Therefore, degassing can be carried out from the paste-state or ink-state coating material before printing, occurrence of unevenness on the surface of the printing surface due to the effect of bubbles split at the surface of the printed resin encapsulating portion can be minimized, an amount or a thickness of the paste-state or ink-state coating materials to be printed can be made uniform, screen printing of high quality and high performance can be carried out, attachment of a coating material to an unintentional portion of the surface of a material to be printed by migrating the coating material from a pore portion of the stencil to the back surface side of the stencil can be prevented, and an excessive printing material being printed to the material to be printed from a screen plate, or attachment of a coating material to a portion other than a desired portion of the material to be printed or causing oozing, can be prevented.

Also, according to the screen printing method of the fifth embodiment of the present invention, a paste-state or ink-state coating material is covered on the surface of a screen plate for printing with a thin thickness by a scraper with a plural number of times, and a height of the scraper at the latter coating is made the same or different than the height of the scraper at the former coating. Therefore, an amount of the paste-state or ink-state coating material at the time of printing can be increased or decreased, and a decrease in bulk at the time of degassing can be supplemented.

Also, according to the screen printing method of the sixth embodiment of the present invention, the above-mentioned screen plate for printing is a gauze-adhered plate or stencil, so that the present invention can be applied to any of the screen plates.

According to the present invention, a screen printing method which can degas a paste-state or ink-state coating material before printing, can prevent unevenness of the surface of a printed surface due to bubbles popped from the surface of a printed resin encapsulated portion, can carry out screen printing of a high quality for high performance electronic parts by making an amount or thickness of a paste-state or ink-state coating material to be printed uniform, can avoid attaching a coating material to an unintentional portion of the surface of a material to be printed, and can prevent printing an excessive printing material on the material to be printed from a screen plate, attaching a coating material to a portion other than a desired portion of the material to be printed or causing oozing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1C are drawings showing that the screen printing method of the present invention is applied to a single coat screen printing method, wherein FIG. 1A is a front sectional view showing a coating step, FIG. 1B is a front sectional view showing a degassing step, and FIG. 1C is a front sectional view showing a printing step in which the reference numeral is a screen printing apparatus, is a platen on which a material to be printed is mounted, is a material to be printed, is a plate frame, is a squeegee, is a scraper, is a screen plate, is the first end, is the second end of the screen plate, is ink, is an ink fountain, is a vacuum chamber and is a lid.

FIGS. 2A and 2B are drawings showing a step of printing in which a second sheet of the material to be printed is printed according to the screen printing method of the present invention, wherein FIG. 2A is a front sectional view showing the state of returning a squeegee and a scraper, and FIG. 2B is a front sectional view showing a coating state in a coating step.

FIGS. 3A and 3B are drawings showing a step of printing in which a second sheet of the material to be printed is printed according to the screen printing method of the present invention, wherein FIG. 3A is a front sectional view showing a degassing step, and FIG. 3B is a front sectional view showing a printing step.

FIGS. 4A-4C are drawings showing that the screen printing method according to the present invention is applied to a screen printing method of double coating, wherein FIG. 4A is a front sectional view showing a second coating state as a coating step, FIG. 4B is a front sectional view showing a degassing step, and FIG. 4C is a front sectional view showing a printing step.

FIG. 5 is a partially enlarged front view showing that the screen printing method according to the present invention is applied to a screen printing method of double coating.

CLAIMS

1. A screen printing method comprising: placing a material to be printed at a predetermined portion of a printing table; feeding one of a paste-state coating material and an ink-state coating material to a surface of a screen plate; coating a thickness of the one of the paste-state coating material and the ink-state coating material onto the surface of the screen plate to form a coated material layer; degassing bubbles in the coated material layer by changing a pressure surrounding the coated material layer from a high-vacuum state to one of an atmospheric-pressure state and a low-vacuum state; and printing the coated material layer onto the material to be printed by sliding the surface of the screen plate and a surface of a squeegee relative to each other while the pressure surrounding the coated material layer is at one of a vacuum state or the atmospheric-pressure state.

2. The screen printing method of claim 1, wherein the screen plate is one of a gauze-adhered plate and a stencil.

3. The screen printing method of claim 1, wherein said coating comprises moving a scraper and the surface of the screen plate relative to each other while the pressure surrounding the coated material layer is at the atmospheric-pressure state.

4. The screen printing method of claim 3, wherein said coating comprises moving the scraper in a first direction relative to the screen plate, and said printing comprises moving the squeegee in a second direction relative to the screen plate, the second direction being opposite the first direction.

5. A screen printing method comprising: placing a material to be printed at a predetermined portion of a printing table; feeding one of a paste-state coating material and an ink-state coating material to a surface of a screen plate from an ink fountain located at an end of the surface of the screen plate; coating a thickness of the one of the paste-state coating material and the ink-state coating material onto the surface of the screen plate to form a coated material layer; degassing bubbles in the coated material layer by changing a pressure surrounding the coated material layer from a high-vacuum state to one of an atmospheric-pressure state and a low-vacuum state; and printing the coated material layer onto the material to be printed by sliding the surface of the screen plate and a surface of a squeegee relative to each other while the pressure surrounding the coated material layer is at one of a vacuum state or the atmospheric-pressure state.

6. The screen printing method of claim 5, wherein said coating is repeated a plurality of times by moving a scraper and the screen plate relative to each other a plurality of times.

7. The screen printing method of claim 6, wherein said degassing is performed after each of said coating repetitions.

8. The screen printing method of claim 5, wherein the screen plate is one of a gauze-adhered plate and a stencil.

9. The screen printing method of claim 5, wherein said coating comprises moving a scraper and the surface of the screen plate relative to each other while the pressure surrounding the coated material layer is at the atmospheric-pressure state.

10. The screen printing method of claim 9, wherein said coating comprises moving the scraper in a first direction relative to the screen plate, and said printing comprises moving the squeegee in a second direction relative to the screen plate, the second direction being opposite the first direction.

11. A screen printing method comprising: placing a material to be printed at a predetermined portion of a printing table; feeding one of a paste-state coating material and an ink-state coating material to a surface of a screen plate from an ink fountain located at an end of the surface of the screen plate; coating a thickness of the one of the paste-state coating material and the ink-state coating material onto the surface of the screen plate to form a coated material layer; degassing bubbles in the coated material layer by changing a pressure surrounding the coated material layer from a high-vacuum state to one of an atmospheric-pressure state and a low-vacuum state; and after said degassing of the coated material layer, printing the coated material layer onto the material to be printed by sliding the surface of the screen plate and a surface of a squeegee relative to each other while the pressure surrounding the coated material layer is at a vacuum state.

12. The screen printing method of claim 11, wherein said coating is repeated a plurality of times by moving a scraper and the screen plate relative to each other a plurality of times.

13. The screen printing method of claim 12, wherein said degassing is performed after each of said coating repetitions.

14. The screen printing method of claim 11, wherein the screen plate is one of a gauze-adhered plate and a stencil.

15. The screen printing method of claim 11, wherein said coating comprises moving a scraper and the surface of the screen plate relative to each other while the pressure surrounding the coated material layer is at the atmospheric-pressure state.

16. The screen printing method of claim 15, wherein said coating comprises moving the scraper in a first direction relative to the screen plate, and said printing comprises moving the squeegee in a second direction relative to the screen plate, the second direction being opposite the first direction.

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