JPH09201940A - Screen printer and printing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high precision print having no projection at the corner and substantially similar to a circuit pattern provided on a screen plate by elevating a matter to be printed only by an amount corresponding to push-in stroke while controlling the speed and acceleration of a printing squeegee before it is separated downward from the lower surface of screen plate. SOLUTION: A left squeegee 5a is lowered down to a squeegee push-in stroke position and then it is shifted in X-direction before printing is started. The left squeegee 5a is then elevated, while controlling the speed and acceleration, only by an amount corresponding to the push-in stroke of a screen plate 4 due to a printing squeegee to a position where the left squeegee 5a comes into contact with the upper surface of screen plate 4. Subsequently, a part 1 to be printed is separated from the screen plate 4 and the left squeegee 5a is elevated to an elevation waiting position. Similar printing operation is performed on the right squeegee 5b side and the operation is repeated alternately thus separating the matter to be printed from the screen plate held in horizontal state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to a screen printing method and a screen printing apparatus for printing a printing paste such as cream solder and a thick film circuit forming paste on an electronic circuit forming substrate such as a printed circuit board. Is.

[0002]

2. Description of the Related Art In recent years, a screen printing apparatus has been used in a cream solder printing process in a circuit mounting process of electronic parts, and the miniaturization of electronic parts mounting boards has progressed with the miniaturization of electronic devices. Accordingly, high precision printing such as cream solder is also required. In such a situation
A variety of devices have been elaborated on the screen printing device for printing with high accuracy.

An example of a conventional screen printing apparatus and screen printing method will be described below with reference to the drawings.

FIG. 5 is a schematic view for explaining an example of a conventional general screen printing apparatus and screen printing method, FIG. 6 is an operation flowchart showing the operation of FIG. 5, and FIG.
Shows a printing state flow chart showing the printing process of FIGS. 5 and 6. In FIG. 5, 1 is an object to be printed, 2 is a positioning stage, 3 is a lifting / lowering driving means for the positioning stage, 4 is a screen plate, 5a is a left squeegee, 5b is a right squeegee, 6a is a lifting / lowering driving means for a left squeegee, and 6b is right. Squeegee lifting drive means, 7a and 7b are left squeegee 5a and right squeegee 5b
Is a stopper for adjusting the lower limit position, 8 is a horizontal reciprocating movement driving means, and 9 is a printing paste such as cream solder.

The substrate 1 can be positioned and fixed on the positioning stage 2. The positioning stage 2 can be moved up and down by the positioning stage up-and-down driving means 3, and during normal printing, it moves up to a position where the upper surface of the substrate 1 comes into contact with the lower surface of the screen plate 4. An air cylinder, a pulse motor, an AC servomotor or the like is generally used as the positioning stage elevating / lowering driving means 3. However, when lowered at a low speed, an accurate printing state with less bleeding and blurring can be easily obtained. A motor is suitable. The left squeegee 5a and the right squeegee 5b are mainly elastic bodies, and urethane rubber (hardness is H
s60 to 90 °) is common. The left squeegee raising / lowering drive means 6a and the right squeegee raising / lowering drive means 6b are generally air cylinders of both rods, and the lower limit position of the squeegees 5a, 5b, that is, the pushing stroke to the screen plate 4 is adjusted by the position adjustment of the stoppers 7a, 7b. Decide. The horizontal reciprocating movement driving means 8 is generally an AC servomotor, and horizontally moves (X direction) while the left squeegee 5a and the right squeegee 5b are in contact with the screen plate 4 when they descend. Operations of the screen printing apparatus and the screen printing method configured as described above will be described below.

Regarding the operation, the operation flow of the first to seventh steps shown in FIG. 6 is general. Printed material 1 in the first step
Is fixed to the positioning stage 2, and in the second step, the material to be printed 1 rises to near the lower surface of the screen plate 4. Printing is performed by lowering the left squeegee 5a in the third step and moving the left squeegee 5a in the X direction in the fourth step. afterwards,
After the substrate 1 is separated from the screen plate 4 at a low speed in the fifth step, the left squeegee 5a is raised in the sixth step, and the substrate 1 is removed in the seventh step. Next, the printing operation on the right squeegee 5b side is performed in the same manner as above, and thereafter, the operation is repeated alternately.

[0007]

However, in the screen printing apparatus and the screen printing method of the above-mentioned conventional configuration, good printing without blurring or blurring can be continuously obtained, but the circuit pattern shape provided on the screen plate 4 is almost the same. Equally, it is not possible to print with high precision, and as shown in the state (c) of FIG. 7, the horns 10 are formed at the corners, and the printing paste 9 of the horns 10 gradually drops after printing, There is a problem that it falls onto the article to be printed 1 and causes defective printing. As an example, in an electronic component mounting process typified by cream solder printing, after the soldering reflow in the subsequent process, the cream solder dropped and caused soldering defects such as solder balls and solder bridges.

The mechanism by which this horn 10 is generated is shown in FIG.
The states (a) to (c) are shown in this order.

State (a) shows the fourth step finished state in FIG. 6, state (b) shows the initial state of the fifth step, and state (c) shows the final state of the fifth step. In the state (a), the printing state 11a is formed with relatively high accuracy. At this time, the left squeegee 5a is curved only for the pushing stroke into the screen plate 4. In the state (b), the left squeegee 5a pushes down the screen plate 4 only for the pushing stroke, and the screen plate 4 tilts. Due to this, the print shape begins to gradually collapse like the print state 11b, and finally the state (c )
As shown in the printed state 11c shown in FIG.

In order to prevent bending of the screen plate 4 by the pushing stroke, the order of the fifth step of separating the substrate 1 from the screen plate 4 at a low speed and the sixth step of raising the left squeegee 5a is reversed. Then, since the left squeegee 5a pulls up the screen plate 4, the screen plate 4 moves up and down to deteriorate the print shape.

The present invention solves the above problems, and provides a screen printing apparatus and a screen printing method which are substantially the same as the circuit pattern shape provided on the screen plate 4 and have no horns 10 at the corners and which enable accurate printing. It is a thing.

[0012]

In order to solve the above-mentioned problems, the screen printing apparatus of the present invention comprises:
The squeegee for printing presses the screen squeegee on the screen plate only by the pressing stroke, it is possible to raise the squeegee for printing while controlling the speed and acceleration, and, after the printing plate is separated from the lower surface of the screen plate by the positioning stage, downward, A screen printing apparatus equipped with a printing squeegee lifting drive means and a positioning control means for the printing squeegee, which can raise a printing squeegee to a predetermined standby position above a screen plate.

Further, the screen printing method of the present invention has substantially the same circuit pattern shape as that provided on the screen plate 4 before the substrate to be pulled down from the lower surface of the screen plate by the positioning stage and has no horns 10 at the corners. Provided is a screen printing device and a screen printing method capable of performing accurate printing.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claims 1 to 6 of the present invention is for printing an upper surface of a screen plate on which a circuit pattern is formed, on an object to be printed which is positioned and fixed on a positioning stage which can be raised and lowered. A screen printing method in which a squeegee horizontally moves while being pushed in, and a printing paste is applied by printing to print a circuit pattern printing unit, before the printing target is separated downward from the lower surface of the printing screen plate by the positioning stage. , After the printing squeegee is raised while controlling the speed and acceleration only by the pushing stroke in which the printing squeegee is pushing on the screen plate, the printing target is moved downward from the lower surface of the screen plate by the positioning stage. The printing squeegee is then lifted up, Fruit, while maintaining a horizontal state in which the screen plate 4 is not tilted, it is possible to separate the printing medium 1 from the screen plate 4, approximately equal to the circuit pattern provided on the screen plate, there is no horn 10 to the corner portion,
Highly accurate printing is possible.

Embodiments of the present invention will be described below with reference to the drawings. It should be noted that components having the same functions as those of the conventional screen printing apparatus and screen printing method are denoted by the same reference numerals, description thereof will be omitted, and operation description will be simplified.

(Embodiment 1) FIG. 1 is a schematic diagram illustrating a screen printing apparatus and a screen printing method according to the present invention, and FIG. 2 is an operation flowchart showing the operation of FIG.
FIG. 3 is a print state flow chart of FIGS. 1 and 2, and FIG. 4 is a relationship diagram of plate separation speed, plate separation acceleration and time in the squeegee operation shown in FIG.

In FIG. 1, reference numeral 12a is a left squeegee lifting pulse motor for driving the left squeegee 5a up and down.
2b is a right squeegee lifting pulse motor for driving the right squeegee 5b up and down, 13a is a left ball screw, 13b is a right ball screw, 14a is a left ball screw nut, 14b is a right ball screw nut. Means are configured.

Numeral 15 is a positioning control means, which is used for raising and lowering the left squeegee 5a and the right squeegee 5b, the position of the squeegee pushing stroke, and the position of the squeegee at the moment when the squeegee comes into contact with the upper surface of the screen plate 4. Positioning can be done at each predetermined position by inputting numerical values from the numeric keypad or calling up program data from memory storage.

The operation of the screen printing apparatus and the screen printing method configured as described above will be described below.

The operation is shown in the operation flow of the first to eighth steps shown in FIG. The main difference from the conventional technique is that the fifth process is added between the fourth and fifth processes of FIG. 2 in the description of the conventional technique.

After the first step and the second step, the left squeegee 5a is lowered to the position of the squeegee pushing stroke in the third step, and the left squeegee 5a is moved in the X direction in the fourth step to perform printing. The state is shown in the state (a) of FIG. Then, in the fifth step, the left squeegee 5a is moved up to the position at the moment when the left squeegee 5a comes into contact with the upper surface of the screen plate 4 by controlling the speed and acceleration by the pushing stroke in which the printing squeegee is pressed on the screen plate 4. The state is shown in the state (b) of FIG. In the sixth step, the substrate 1 is separated from the screen plate 4 as shown in the state (c) of FIG. 3, and then in the seventh step, the left squeegee 5a is raised to the raising standby position, and the eighth step is performed. Next, the printing operation on the right squeegee 5b side is performed in the same manner as above, and thereafter, the operation is repeated alternately.

In the above fifth step, the plate separation speed and plate separation when raising the left squeegee 5a to the position at the moment of contacting the upper surface of the screen plate 4 only by the pressing stroke in which the printing squeegee is pressed on the screen plate 4 in the fifth step. The relationship between acceleration and time is shown in FIG. As shown in Fig. 4 (a), the speed of plate separation and the acceleration of plate separation are set to low speed (10 mm / s ⇒ 0.5 mm / s) and low acceleration (100 mm / s ⇒ 25 mm / s), so that the left squeegee 5 a The vertical movement of the screen plate 4 due to the lifting of the screen plate 4 can be suppressed, and accurate printing can be performed.

Further, as shown in FIG. 4B, by setting a plurality of plate separation speeds and plate separation accelerations, vertical movement of the screen plate 4 due to the left squeegee 5a pulling up the screen plate 4 is suppressed, In addition, the cycle time can be shortened and accurate and efficient printing can be performed.

Further, as shown in FIG. 4 (c), by controlling the plate separation speed and the plate separation acceleration by an S-shaped curve (sin curve), the left squeegee 5a pulls up the screen plate 4 to cause the screen plate 4 to rise. It is possible to further suppress the vertical movement of the sheet and perform accurate printing.

As described above, according to the present embodiment, the printing squeegee lifting drive means and the positioning control means 15 which are main components of the left squeegee lifting pulse motor 12a and the right squeegee lifting pulse motor 12b are provided. By this, the position, speed and acceleration at the moment when the left squeegee 5a and the right squeegee 5b come into contact with the upper surface of the screen plate 4 can be arbitrarily set and the left squeegee 5a, The right squeegee 5b
As a result, the speed and acceleration can be controlled to the position at the moment of contact with the upper surface of the screen plate 4, and the printing plate 1 can be separated from the screen plate 4 while keeping the screen plate 4 in a horizontal state without tilting. 4 is almost the same as the circuit pattern shape, there are no horns 10 at the corners, and accurate printing like the printing state 16 can be performed.

[0026]

As described above, according to the present invention, the printing squeegee lifting drive means and the positioning control means, which are main components such as the squeegee lifting pulse motor and the like, are provided, and the object to be printed is positioned on the lower surface of the screen plate by the positioning stage. The printing squeegee pushes the screen squeegee on the screen plate before pulling it down.By raising the printing squeegee by controlling the speed and acceleration, the printing plate is kept horizontal without tilting. Since the portion can be separated from the screen plate, the circuit pattern shape is almost the same as that provided on the screen plate, and there is no horn at the corner portion, and accurate printing can be performed.

[Brief description of drawings]

FIG. 1 is a schematic diagram illustrating a screen printing apparatus and a screen printing method of the present invention.

FIG. 2 is an operation flowchart showing the operation of FIG.

FIG. 3 is a diagram showing a printing process of FIGS. 1 and 2;

FIG. 4 is a diagram showing the relationship between plate separation speed, plate separation acceleration, and time in the squeegee operation shown in FIG.

FIG. 5 is a schematic diagram illustrating an example of a conventional general screen printing apparatus and screen printing method.

6 is an operation flowchart showing the operation of FIG.

FIG. 7 is a diagram showing a printing process of FIGS. 5 and 6;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Printed material 2 Positioning stage 3 Lifting / driving means for positioning stage 4 Screen plate 5a Left squeegee 5b Right squeegee 9 Printing paste 12a Left squeegee lifting pulse motor 12b Right squeegee lifting pulse motor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takao Naito 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (6)

[Claims] 1. A circuit pattern is printed by printing a printing paste by moving horizontally while a printing squeegee presses on the upper surface of a screen plate on which the circuit pattern is formed, on a printing object set on a vertically movable positioning stage. In this case, before the positioning stage moves downward to separate the substrate to be printed from the lower surface of the screen plate, the printing squeegee presses the screen squeegee on the screen plate while controlling the speed and acceleration only for the pressing stroke. A screen printing method in which the squeegee is raised and the positioning stage moves downward to separate the printing material from the lower surface of the screen plate. 2. A circuit pattern is printed by printing and applying a printing paste by moving horizontally while a printing squeegee presses on the upper surface of a screen plate on which the circuit pattern is formed, on an object to be printed set on a vertically movable positioning stage. In the screen printing apparatus, the positioning stage moves downward and separates the object to be printed from the lower surface of the screen plate, while controlling the speed and acceleration only for the pressing stroke in which the printing squeegee is pressing on the screen plate. A screen provided with control means for operating the elevation drive unit for the printing squeegee and the elevation drive unit for the positioning stage so that the positioning stage moves downward after the printing squeegee is raised and the printing object is separated from the lower surface of the screen plate. Printing device. 3. The screen printing method according to claim 1, wherein when the printing squeegee is raised, control is performed so that a plurality of speeds and accelerations can be set in multiple stages. 4. The screen printing apparatus according to claim 2, further comprising means for performing a control in which a plurality of speeds and accelerations can be set in multiple stages when the printing squeegee is raised. 5. The S-curve (sin curve) according to claim 1, wherein the speed and the acceleration are raised when the printing squeegee is raised.
Screen printing method controlled by. 6. The S-curve (sin curve) according to claim 2, wherein the speed and the acceleration are increased when the printing squeegee is raised.
A screen printing device provided with means for controlling by.