JPH08244203A - Method and apparatus for screen printing - Google Patents

Abstract

PURPOSE: To provide a method for screen printing and a screen printer in which a plate can be snapped off at an optimum speed under printing conditions and no angle and no thread-forming occur at print paste and which has high resolution. CONSTITUTION: The method for screen printing comprises the step (b) of bringing a screen 4 provided with a desired printing pattern in an opening 4-1 into close contact with the entire surface of the print surface 3-1 of a matter 3 to be printed, the step (c) of sliding a squeegee 5 to selectively cover the surface 3-2 of the matter 3 to be printed from the opening 4-1 with print paste 6, and the step (d) of snapping off the screen 4 from the matter 3 to be printed in the direction perpendicular to the printing surface at a creep speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to stencil printing or screen printing technology, and more particularly to an industrial screen printing method and screen printing apparatus.

[0002]

2. Description of the Related Art In recent years, screen printing technology has been applied to manufacture miniaturized and high-density electronic devices. For example, in the manufacture of circuit boards for hybrid integrated circuits, reflow soldering is performed after screen-printing solder paste when forming wiring patterns by screen-printing conductive paste and when mounting electronic components on the circuit board. It is being appreciated.

In the screen printing of a printing paste containing such a conductive material, the mechanism that is decisive for the printing quality is the passage of the printing paste through the opening and the plate separation (also called blank).

FIG. 4 shows the structure of a screen in a conventional screen printing apparatus. The printed pattern is the opening 101
The metal mask 102 provided as is fixed to the plate frame 104 with a certain tension via the Tetron sheet 103.

FIG. 5 shows a printing mechanism in a conventional screen printing apparatus. The metal mask 102 is kept at a certain distance h (called snap-off distance) from the upper surface (printing surface) of the printing object 111 held on the printing table 110.
Is arranged. Then, by sliding the squeegee 112 to which a predetermined pressure is applied, the metal mask is brought into close contact with the object to be printed immediately below the squeegee, and the internal pressure of the printing paste 113 caused by the sliding of the squeegee causes the printing paste to move to the metal mask 102.
And is adhered to the printing object 111 through the opening. Squeegee 1
In the portion after 12 has passed, the metal mask 102 is peeled off from the printing object 111 due to the restoring force of the screen, causing plate separation.

FIG. 6 is a schematic cross-sectional view showing how the printing paste is divided during plate separation. In FIG. 6, the squeegee slides from left to right with a predetermined pressure applied from above. A to E show the state distribution of the print paste in the sliding direction of the squeegee at a certain time, and also show the time course of the same place.

In the right part A of the squeegee, the squeegee pressure causes the printing paste to fill one opening of the gauze. In the portion B directly below the squeegee, the printing paste receives a compressive force. By the next momentary plate separation operation, it is rapidly pulled between the gauze and the printing medium (C). Print paste
It is torn off (D). The torn printing paste is restored from the towed state due to its viscoelasticity (E).
The printing paste then flows into a smooth state until a film is formed on its surface.

Factors related to the transfer of the printing paste in the above process are the viscoelasticity of the printing paste, the speed of plate separation, the tension of the boundary surface between the printing paste and the gauze thread, and the acceptability of the printing paste of the printing medium. And so on.

[0009]

However, in the above-described conventional screen printing method, the plate separation speed is not constant depending on the printing conditions and the jigs such as the squeegee, and a preferable plate separation speed is obtained over the entire printing surface. Not being formed, the corners of the printing paste are generated, and pattern thinning occurs. In particular, the higher the plate separation speed, the higher the incidence of corners. Therefore, there have been problems that the resolution of screen printing is deteriorated, a short circuit or disconnection of a wiring pattern occurs, and a short circuit due to a solder bridge or a poor connection due to insufficient solder occurs during printing of a solder paste.

In view of the above problems, it is an object of the present invention to provide a screen printing method and a screen printing apparatus which can perform plate separation at a speed optimal for printing conditions and have a high resolution without corners or stringing in the printing paste. It is to be.

[0011]

In order to achieve the above object, the present invention has the following constitution. That is, according to the invention of claim 1, a step of bringing a screen provided with a desired print pattern as an opening into close contact with the entire printing surface of a printing medium, and sliding a squeegee to apply the printing paste from the opening. A screen printing method comprising: a step of selectively adhering to a printing surface of a printing body; and a step of separating the screen and the printing object from each other at a slight speed in a direction perpendicular to the printing surface. Is.

The invention according to claim 2 is the screen printing method according to the invention according to claim 1, characterized in that the plate separation speed is any of 0.03 mm / sec to 0.3 mm / sec. Is.

According to a third aspect of the present invention, there is provided a holding base for holding the object to be printed, and a screen holding means for holding a screen provided with a desired printing pattern as an opening in parallel with the printing surface of the object to be printed. A screen elevating mechanism capable of lowering the screen until it comes into close contact with the printing surface, and raising the screen in close contact with the printing surface at a minute speed; and a squeegee driving means for sliding a squeegee over the screen. And a screen printing device.

According to a fourth aspect of the present invention, there is provided a holding base for holding the object to be printed, and a screen holding means for holding a screen provided with a desired print pattern as an opening in parallel with the printing surface of the object to be printed. And a holding platform elevating mechanism capable of raising the holding platform until the screen is in close contact with the printing surface of the printing medium, and lowering the printing medium in close contact with the screen at a slow speed, A squeegee driving means for sliding a squeegee on a screen, and a screen printing device.

[0015]

With the above construction, in the invention according to claim 1, the screen is brought into close contact with the entire printing surface of the object to be printed, and then the squeegee is slid to apply the printing paste from the opening to the printing surface of the object to be printed. Apply selectively. Then, by separating the screen and the printing medium from each other at a slight speed in the direction perpendicular to the printing surface, the operation of the squeegee and the operation of separating the plate can be performed independently, and the optimum speed can be achieved over the entire printing surface. You can perform plate separation with.

In the invention according to claim 2, the plate separation speed can be 0.03 mm / sec to 0.3 mm / sec.

According to the third aspect of the invention, the object to be printed is held on a fixed holding base, and the screen is lowered by an elevating device until it comes into close contact with the printing surface. Then, the squeegee is slid by the squeegee driving means. Then
By raising the screen in close contact with the printing surface at a slight speed, it is possible to perform plate separation at the optimum speed over the entire printing surface.

Further, in the invention according to claim 4, the holding table holding the material to be printed is raised to bring the screen and the printing surface of the material to be printed into close contact with each other. Then, the squeegee is slid by the squeegee driving means. Next, by lowering the printing medium that is in close contact with the screen at a slight speed, the plate can be separated over the entire printing surface at an optimum speed.

[0019]

Embodiments of the present invention will now be described in detail with reference to the drawings. 1A to 1C are sectional views in order of the steps, showing the steps of the screen printing method according to the present invention.

In FIG. 1, first, the printing medium 3 is held on the holding table 2 with the plate frame 1 raised (a). In order to hold the body 3 to be printed, suction by vacuum is usually used. Next, the plate frame 1 is lowered to bring the screen 4 into close contact with the upper surface (printing surface) 3-1 of the printing target body 3 (b).
Next, the squeegee 5 is slid on the screen 4, and the printing paste 6 is applied to the printing medium 3 from the opening of the screen 4 (c). Next, the plate frame 1 is raised at a very low speed to separate the plate (d). In the step of separating the plate, instead of raising the plate frame 1, the holding table 2 may be lowered at a very low speed while holding the body 3 to be printed.
Next, after the printing paste 6 has come off the screen 4 (usually, a rising width of about 1 mm), in order to ensure workability,
The plate frame 1 is raised at high speed (e).

According to an experimental example, when a conductive paste was used as the printing paste, the plate separation speed was 0.03 mm / sec to 0.3 under the printing conditions shown in Table 1 below.
mm / sec is appropriate, of which 0.05 mm /
The best print quality was obtained in sec.

[0022]

[Table 1] FIG. 2 is a cross-sectional view of essential parts showing the configuration of the first embodiment (plate frame elevating type) of the screen printing apparatus according to the present invention. In FIG. 2, the screen printing apparatus includes a holding table 12 that holds the object 11 to be printed horizontally, a metal mask 13 that is a screen provided with a desired printing pattern as an opening,
A plate frame 14 for horizontally holding the metal mask 13, a screen elevating mechanism 15 for elevating and lowering the plate frame 14 including the speed reduction mechanism 15-1 and the ball / screw mechanism 15-2 and holding the metal mask 13, and a screen elevating mechanism. A motor 16 which is a prime mover for driving the motor 15, and a control circuit 17 which controls the rotation speed of the motor 16 to control the screen lifting speed.
And a squeegee drive mechanism 19 for sliding the squeegee 18 on the metal mask 13.

Next, the operation of the screen printing apparatus shown in FIG. 2 will be described. First, the motor 16 is positively rotated at a steady speed, and the rotation of this motor is decelerated by the speed reduction mechanism 15-1 and converted into a linear motion by the ball screw mechanism 15-2 to raise the plate frame 14 to a predetermined position. To stop. With the plate frame 14 raised, the printing medium 11 is held by the holding table 1.
2 is loaded and held. To hold the printing medium 11, suction by a vacuum mechanism (not shown) is used. Next, the motor 16 is rotated in the reverse direction, and the plate elevating mechanism 15 lowers the plate frame 14. Then, when the metal mask 13 descends until it comes into close contact with the upper surface of the printing target 11, the motor 16 is stopped.

Then, the squeegee driving mechanism 19 slides the squeegee 18 on the metal mask 13 to selectively deposit a printing paste (not shown) on the printing medium 11 through the opening of the metal mask 13. Next, the motor 16 is normally rotated at a low speed to raise the plate frame 14 at a very low speed to separate the plate. This plate separation speed is 0.03 mm
The control is possible within the range of 1 / second to 0.3 mm / second. Next, when the plate frame 14 rises by about 1 mm, the motor 16 is rotated at a constant speed to ensure workability,
The plate frame 14 is raised at high speed. The steady speed rotation and the low speed rotation of the motor 16 are performed by changing the frequency supplied to the motor 16 by the inverter control of the control circuit 17.

FIG. 3 is a cross-sectional view of the essential parts showing the configuration of the second embodiment (holding platform elevating type) of the screen printing apparatus according to the present invention. In FIG. 3, the screen printing apparatus includes a holding table 22 that horizontally holds the object 11 to be printed, a metal mask 13 provided with a desired printing pattern as an opening, and a plate frame 14 that horizontally holds the metal mask 13. And a holding table elevating mechanism 25 that includes the deceleration mechanism 25-1 and the ball screw mechanism 25-2 to elevate the holding table 22 with respect to the printing machine body 20, and a motor that is a prime mover that drives the holding table elevating mechanism 25. 26, a control circuit 27 for controlling the rotation speed of the motor 26 to control the lifting speed of the holding table, and a squeegee driving mechanism 1 for sliding the squeegee 18 on the metal mask 13.
9 is provided. In addition, in FIG.
The same components as those in FIG. 2 are designated by the same reference numerals.

Next, the operation of the screen printing apparatus shown in FIG. 3 will be described. First, the motor 26 is positively rotated at a steady speed, the rotation of the motor is decelerated by the speed reduction mechanism 25-1, and converted into a linear motion by the ball screw mechanism 25-2, and the holding table 22 is lowered to a predetermined position. To stop. With the holding table 22 lowered, the printing medium 11 is loaded and held on the holding table 22. To hold the printing medium 11, suction by a vacuum mechanism (not shown) is used. Next, the motor 26 is rotated in the reverse direction, and the holding table elevating mechanism 25 raises the holding table 22. Then, the holder 2 is held until the upper surface of the printed body 11 comes into close contact with the metal mask 13.
When 2 rises, the motor 26 is stopped.

Next, the squeegee driving mechanism 19 slides the squeegee 18 on the metal mask 13 to selectively deposit a printing paste (not shown) on the printing medium 11 through the opening of the metal mask 13. Next, the motor 26 is normally rotated at a low speed, and the holding table 22 is lowered at a very low speed to separate the plate. This plate release speed is 0.03m
It can be controlled in the range of m / sec to 0.3 mm / sec. Next, when the holding table 22 descends about 1 mm,
In order to ensure workability, the motor 26 is rotated at a constant speed and the holding table 22 is lowered at a high speed. The steady speed rotation and the low speed rotation of the motor 26 are performed by changing the frequency supplied to the motor 26 by the inverter control of the control circuit 27.

While the preferred embodiment has been described above, this is not meant to limit the invention. For example, the distance at which the plate is separated at a very low speed is set to about 1 mm, but it may be set arbitrarily according to the viscosity of the printing paste. Various types of mechanisms are known for the screen lifting mechanism, the holding platform lifting mechanism, and the squeegee driving mechanism.
It goes without saying that either format may be adopted.

[0029]

As described above, according to the present invention, after the screen is brought into close contact with the entire printing surface of the printing medium and printing is performed, the screen and the printing medium are moved at a slight speed in the direction perpendicular to the printing surface. By separating the plates, there is an effect that printing can be performed with high resolution without corners and stringing, especially when a high-viscosity printing paste such as a conductive paste is used.

[Brief description of drawings]

1A to 1C are cross-sectional views in order of steps, showing steps in a screen printing method according to the present invention.

FIG. 2 is a cross-sectional view of essential parts showing the configuration of the first embodiment of the screen printing apparatus according to the present invention.

FIG. 3 is a cross-sectional view of main parts showing the configuration of a second embodiment of the screen printing apparatus according to the present invention.

FIG. 4 is a plan view showing a structural example of a screen in the screen printing apparatus.

FIG. 5 is a cross-sectional view illustrating a printing mechanism in a conventional screen printing device.

FIG. 6 is a schematic cross-sectional view showing how the printing paste is divided during plate separation.

[Explanation of symbols]

1 plate frame 2 holding base 3 material to be printed 4 screen 5 squeegee 6 printing paste

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location // H05K 3/12 7511-4E H05K 3/12 C

Claims (4)

[Claims] 1. A step of bringing a screen provided with a desired print pattern as an opening into close contact with the entire printing surface of a printing medium, and a squeegee is slid to print a printing paste from the opening to the printing medium. A screen printing method comprising: a step of selectively adhering to a surface; and a step of separating the screen and the printing medium from each other at a slight speed in a direction perpendicular to the printing surface. 2. In the step of separating the screen and the printing medium from each other at a slight speed in a direction perpendicular to the printing surface, the plate separation speed is 0.03 mm / sec to 0.3 mm / sec. The screen printing method according to claim 1, wherein the screen printing method is provided. 3. A holding base for holding a printing medium, a screen holding means for holding a screen provided with a desired printing pattern as an opening in parallel with a printing surface of the printing medium, and the screen for printing the screen. A screen elevating mechanism capable of lowering the screen in close contact with the printing surface and lifting the screen in close contact with the printing surface at a minute speed; and a squeegee driving means for sliding a squeegee on the screen. Characteristic screen printing device. 4. A holding table for holding an object to be printed, a screen holding means for holding a screen provided with a desired printing pattern as an opening in parallel with a printing surface of the object to be printed, and the screen being the object to be covered. A holding table elevating mechanism capable of raising the holding table until it comes into close contact with the printing surface of the printing body and lowering the printing object that comes into close contact with the screen at a fine speed, and sliding a squeegee over the screen. A screen printing apparatus comprising: a squeegee driving unit for causing the squeegee.