JP2003175583A - Screen printing machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively prevent a soldering paste from entering the rear side of a squeegee and adhering, and improve the printing quality. <P>SOLUTION: This screen printing machine has a squeegee mechanism which has squeegees 9a and 9b, and moves the squeegees 9a and 9b in the directions of the Y axis and the Z axis while switching them, and a main controlling means which controls the driving of the squeegee mechanism, and so forth. The main controlling means controls the driving of the squeegee mechanism in such a manner that the squeegee 9a (or 9b) located at a standing-by location above a mask sheet may be diagonally lowered from the downstream side to the upstream side in the applying direction by the squeegee 9a (or 9b) and may be brought into contact with a contact point P on the mask sheet 7. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screen printing machine for applying a solder paste composed of a mixture of solder powder and a paste-like flux onto a substrate.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 8A, a mask sheet 50 for screen printing is superposed on a substrate W set on a stage, and the solder paste supplied on the mask sheet is squeegees 52a and 52b. A screen printing machine is generally known in which a solder paste (indicated by hatching; abbreviated as paste) is applied to a predetermined position on the substrate W through an opening formed in the mask sheet 50 by spreading it by using a screen printing machine. .

In this type of screen printing machine, a pair of squeegees 52a and 52b (referred to as first squeegee 52a and second squeegee 52b) are provided as shown in FIG. The squeegees 52a and 52b are alternately used during and in the backward movement so that the paste can be efficiently applied. That is, as shown in the figure, the first squeegee 52a is applied to the mask sheet during the forward movement, and the paste is applied while the second squeegee 52b is retracted upward. ), The paste is applied by the second squeegee 52b in a state where the first squeegee 52a and the second squeegee 52b are switched.

[0004]

By the way, since the paste applied as described above has a high viscosity to some extent, the squeegees 52a, 5a, 5a are changed by switching the squeegees.
When the 2b is moved to the retracted position, the paste often adheres to the tip portions of the squeegees 52a and 52b in a stringed state (hanging state) as shown in FIG. 8B and the like.

[0005] The paste thus adhered (referred to as adhered paste) is then used when the squeegees 52a and 52b are set at the contact points on the mask sheet 50.
For example, as shown in FIG. 9, the squeegee (the second squeegee 52b in the figure) may adhere to the rear side of the squeegee, that is, the side opposite to the moving direction. When the viscosity of the paste is low, the paste drops from the squeegees 52a and 52b at the retracted position, and the squeegees 52a and 52b come into contact with the mask sheet 50 from directly above the dropped paste. The state becomes as shown in. In this case, for example, as the squeegee 52b subsequently moves, the adhered paste is dragged, and the adhered paste passes again over the substrate on which the paste has already been applied, so that the thickness of the paste applied on the substrate is not uniform. After printing, part of the paste remains around the lower end of the printing opening when the substrate W is separated from the mask sheet 50 after printing, and the unprinted substrate W ( When the next substrate W) contacts, the paste around the opening will
Between the mask sheet 50 and the mask sheet 50, which is one of the causes of impairing print quality. Therefore, it is desired to solve this point.

The present invention has been made in view of the above problems, and it is an object of the present invention to effectively prevent the solder paste from wrapping around and adhering to the rear side of the squeegee, thereby improving the print quality. I am trying.

[0007]

In order to solve the above problems, the invention according to claim 1 extends the solder paste supplied onto the mask sheet by moving a squeegee along the mask sheet, In a screen printing machine for coating a substrate laminated on a mask sheet, it has a moving means for moving the squeegee in a horizontal direction and a vertical direction parallel to the mask sheet, and a drive control means for controlling the driving of the moving means, At the start of the paste coating operation, the drive control means lowers the squeegee located at a predetermined retracted position above the mask sheet in an oblique direction from the downstream side to the upstream side in the paste coating direction by the squeegee to cause a predetermined amount on the mask sheet. Is configured to be brought into contact with the contact point.

With this structure, since the squeegee is slanted downward from the retracted position toward the contact point on the mask sheet, the paste (adhesive paste) attached to the tip of the squeegee may hang down, or When the squeegee is dropped, the attached paste is attached to a portion on the downstream side of the mask sheet in the paste application direction by the squeegee in the process of moving from the retracted position to the contact point. Therefore, when the squeegee comes into contact with the contact point, the attached paste or the dropping paste does not wrap around to the rear side of the squeegee, that is, the upstream side in the paste application direction by the squeegee.

In this case, the squeegee may be lowered straight obliquely from the retracted position to the contact point. For example, a vertical operation of lowering the squeegee straight from the retracted position and the squeegee upstream in the paste application direction. The squeegee may be configured to descend in an oblique direction by alternately repeating a horizontal operation of horizontally moving to the side (claim 2).

As the squeegee, a pair of squeegees are arranged side by side in the paste application direction, and the solder paste is applied to the substrate while the two squeegees are integrally reciprocally moved and the squeegee is selectively used for forward and backward movements. Regarding the one, after the paste application operation by the one side squeegee is completed, the one side squeegee is raised to the retracted position, and then both the squeegees are once returned to the upstream side in the paste application direction by the one side squeegee. It is preferable that the drive control means is configured to lower the squeegee on the other side to the contact point (claim 3).

That is, after the application operation by the squeegee on one side is completed, the squeegee may be raised and the squeegee on the other side may be lowered in that direction from that point, but in this case, the other side is squeegeeed. Since the squeegee is lowered in the diagonal direction, it is necessary to set the contact point of the squeegee farther from the completion point of the coating operation, and a lot of space is required outside the application completion point. On the other hand, as described above, if both squeegees are once returned in the opposite direction and then the other side squeegee is lowered obliquely, the contact point of the other side squeegee is located closer to the application completion point. It is possible to set it, and the space outside the application completion point is small. Therefore, the squeegee operation as described above can be performed in a small space.

Further, in the screen printing machine according to any one of claims 1 to 3, after the paste application operation by the squeegee is completed, the squeegee is obliquely lifted to the downstream side in the paste application direction by the squeegee and the squeegee is moved to the retracted position. More preferably, the squeegee is configured to move (claim 4).

According to this structure, after the coating is finished, the solder paste that has adhered to the squeegee and has been in a stringed state due to the rise is applied to the coating completed portion (the portion upstream of the coating completion point by the squeegee). It becomes possible to effectively prevent the adhesion.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment of a screen printing machine according to the present invention. This screen printing machine has
A printer main body 2 having a base 1 and a substrate supporting unit 3 for supporting a printed circuit board W are arranged, and a conveyor 3A for loading and unloading the substrate W is placed on the substrate supporting unit 3. It is fixed.

Although not shown in detail in the drawings, the substrate supporting unit 3 has an elevating and lowering rotary table 4 installed on the base 1, and in the elevating and lowering rotary table 4 or on the base 1. With the moving mechanism provided, the X-axis direction of the printer main body 2 (the loading / unloading direction of the substrate W by the conveyor 3A, that is, the direction orthogonal to the paper surface of FIG. 1), the Y-axis direction (the left-right direction of FIG. 1), The support position of the substrate W is movable in the Z-axis direction (vertical direction) and the θ direction (rotational direction around the Z-axis).

The main body 2 of the printing press has support columns 2a arranged at the four corners of the base 1, and support frames 2a at the four corners.
And a U-shaped upper frame 2b having an open front (left side in FIG. 1).

A frame member 8 fixed to the upper frame 2b is provided above the substrate supporting unit 3, and a mask sheet 7 is detachably fixed to the frame member 8.
As shown in FIG. 2, the frame member 8 has a plurality of sensors 20 a to 20 b (first sensor 2) for detecting the mask sheet 7.
0a to 4th sensor 20b) are assembled in a predetermined arrangement, and the size (type) of the mask sheet 7 set on the frame member 8 is determined by these sensors 20a to 20b as described in detail later. It is configured to be determined based on the above.

A squeegee mechanism 5 (moving means) is arranged above the mask sheet 7. The squeegee mechanism 5 includes rail members 5a respectively provided on a pair of front and rear upper frames 2b arranged in a direction orthogonal to the plane of FIG. 1, and along the rail members 5a in the Y-axis direction (see FIG. 1). The Y-axis servomotor 2 is supported so as to be movable in the left-right direction.
A girder member 5b driven by a single-axis robot (not shown) whose driving source is 2 (shown in FIG. 3), and a pair of squeegees 9a elongated in the X-axis direction for spreading and spreading the solder paste on the mask sheet 7, 9b (referred to as a first squeegee 9a and a second squeegee 9b), and an elevating means which is arranged on the girder member 5b to elevate and lower the squeegees 9a, 9b.

The elevating means is supported by the girder member 5b so as to be able to ascend and descend, and elevates and lowers by a drive mechanism having a Z-axis servomotor 24 (shown in FIG. 3) as a drive source.
And the air cylinder 1 mounted on the lifting frame 10.
Mounting holder 13 driven up and down by 2a and 12b
a and 13b, these mounting holders 13a,
The squeegees 9a and 9b are attached to 13b.
Then, the elevating frame 10 by the Z-axis servomotor 24
Of the squeegees 9a, 9b by lifting and lowering the mounting holders 13a, 13b by the air cylinders 12a, 12b.
b is configured to be displaced between a retracted position separated above the mask sheet and an operating position where the mask sheet 7 is pressed against the mask sheet 7.

Although not shown in detail, each squeegee 9a, 9b comprises a squeegee body made of, for example, hard urethane or stainless steel, and a squeegee holder made of a light alloy such as an aluminum alloy for holding the squeegee body. The attachment holders 13a and 13b are detachably assembled.

A cleaning unit 16 is installed on the base 1 beside the substrate supporting unit 3. The cleaning unit 16 is movably provided at a central cleaning position corresponding to a printing position by the squeegee mechanism 5 and the like and a standby position (a position shown by a solid line in FIG. 1) provided on a side portion of the base 1. In addition, it is configured to be connectable to the substrate support unit 3. That is, it is configured to move between these positions together with the substrate support unit 3 by being connected to the substrate support unit 3.

FIG. 3 is a block diagram showing the construction of a portion mainly controlling the squeegee mechanism 5 in the control system of the screen printing machine.

As shown in this figure, the screen printer is
It has a control unit 30 including a well-known CPU that executes logical operations, a ROM that stores various programs for controlling the CPU in advance, and a RAM that temporarily stores various data during operation of the device. The servomotors 22 and 24, the encoders 23 and 25 mounted on the motors 22 and 24, and the first to fourth sensors 20a to 20
d and electromagnetic valves 26a and 26b for switching the air supply and discharge of the air cylinders 12a and 12b are connected to the control device 30. Further, an input means 35 for inputting various printing conditions described later is connected to the control device 30.

The control device 30 includes an axis control means 31, a size discrimination means 32, a storage means 33 and a main control means 34.

The axis control means 31 controls the driving of the Y-axis servo motor 22 and the Z-axis servo motor 24 to move the squeegees 9a and 9b in the Y-axis direction and the Z-axis direction (elevation by the elevating frame 10). Is. In this embodiment, the axis control means 31 and the main control means 34 described later correspond to the drive control means of the present invention.

The size discriminating means 32 discriminates the size of the mask sheet 7 set on the frame member 8 according to the state of detection of the mask sheet 7 by the first to fourth sensors 20a to 20d, and the detection result is shown. It is output to the main control means 34. The specific determination method will be described later.

The storage means 33 stores a series of basic operation programs of the screen printing machine and also stores printing conditions corresponding to the size of the mask sheet 7, for example, moving stroke conditions of the squeegees 9a and 9b as table data. is there.

The main control means 34 comprehensively controls the operation of each part of the screen printing machine based on the basic operation program stored in the storage means 33. During the coating operation by the squeegee mechanism 5, the size determination is performed. The printing condition corresponding to the size of the mask sheet 7 is read from the control device 30 according to the determination result by the means 32, and the drive of the squeegee mechanism 5 and the like is controlled based on the condition.

The discrimination of the mask sheet 7 by the size discriminating means 32 will now be described.

The frame member 8 on which the mask sheet 7 is mounted has a plurality of sensors 20a-20b (first
Sensor 20a to fourth sensor 20b) are provided,
The first to fourth sensors 20a to 20d are the mask sheet 7
It is arranged as follows in relation to the size of. That is, the printing machine of the present embodiment can use five types of mask sheets 7 of extra large size to extra small size (LL, L, M, S, SS), and these mask sheets 7 are used at the printing position. It is configured to be set at its center position with respect to. Then, as shown in FIG. 2, the fourth sensor 20d and the first to third sensors 20 are sequentially arranged from the Y-axis direction outer side (right side in the figure) with respect to the center position of the printing position.
a to 20c are arranged, and when the mask sheet 7 is attached, the detection states (ON states) of the first to fourth sensors 20a to 20d are in accordance with the size thereof according to the following table. The arrangement of ~ 20d is defined.

[0032]

[Table 1]

That is, the size discriminating means 32 is constructed so as to discriminate the size of the mask sheet 7 from the correspondence relationship in the above table based on the detection states of the first to fourth sensors 20a to 20d.

The brackets in the above table indicate the first to fourth sensors 20 in relation to the frame size of the mask sheet 7.
Since the detection statuses of a to 20d may be slightly different, this is taken into consideration. For example, for the mask sheet 7 of size LL, the first sensor 20a is basically ON.
In that case, it is configured to determine that the mask sheet 7 is the LL size in either case where only the first sensor 20a is ON or when the first to third sensors 20a to 20c are ON.

As for the minimum size SS, although not shown, the mask sheet 7 is mounted on the frame member 8 in a state where a dedicated adapter is mounted. The fourth sensor 20d is configured to detect.

Although not shown in detail, the first, fourth
The sensors 20a and 20d are contact type sensors such as microswitches, and are configured so that when the mask sheet 7 is set, the mask sheet 7 is detected by coming into contact with the frame portion from the outside of the mask sheet 7. On the other hand, the second
The third sensors 20b and 20c are non-contact type sensors such as a reflective photo sensor, and detect the frame portion of the mask sheet 7 from the lower side thereof to detect the mask sheet 7.
Is configured to detect. However, these are merely examples, and it is of course possible to use other sensors.

Next, the printing operation of the screen printing machine based on the control of the main control means 34 will be described.

First, as a preparatory work before printing, the mask sheet 7 corresponding to the substrate W to be printed is attached to the frame member 8.
Is set to. When the mask sheet 7 is set in this way, the size of the mask sheet 7 is determined based on the detection states of the first to fourth sensors 20a to 20d, and the printing conditions of the substrate W corresponding to the mask sheet 7 are determined. Is read and the operating program is initialized.

When the preparatory work is completed, the substrate supporting unit 3 is moved to a predetermined substrate receiving position by the operation of the lifting / lowering rotary table 4, and the substrate W is conveyed along the conveyor 3A, so that the substrate supporting unit 3 is moved onto the substrate supporting unit 3. W is delivered and held.

Next, the substrate supporting unit 3 is moved below the mask sheet 7 to position the substrate W with respect to the mask sheet 7 in the X, Y and θ directions, and then the substrate supporting unit 3 is lifted, whereby the substrate is moved. W is set at a predetermined printing position where it abuts the back surface of the mask sheet 7.

When the substrate W is set at the printing position, the squeegee 9a (or 9b) on one side of the squeegees 9a, 9b has a predetermined height at the work start position, that is, its tip (lower end) is on the mask sheet 7. After the squeegee mechanism 5 is driven, the squeegee 9a (9b) is moved in the Y-axis direction after being set at a height position where the squeegee contacts the predetermined contact point. Thereby, the first squeegee 9a and the second squeegee 9b slide along the surface of the mask sheet 7 according to the moving direction to spread and spread the paste on the mask sheet 7, and as a result, the paste is formed on the mask sheet 7. It will be applied to the substrate W through the opening.

When the printing is completed, the squeegees 9a and 9b are reset to the ascending end position, the substrate supporting unit 3 is moved to the substrate delivering position, and the substrate W is conveyed along the conveyor 3A. As a result, the substrate W is sent from the substrate supporting unit 3 to the next step. The paste is automatically or manually replenished on the mask sheet 7 during printing as appropriate.

Then, thereafter, while the next substrate W is similarly carried in and out of the substrate supporting unit 3, the paste is applied to the substrate W, and during the printing operation of such a substrate W, a certain amount is maintained. The cleaning unit 16 and the substrate supporting unit 3 are connected at a timing, and the cleaning unit 16 is pulled out from the standby position to the cleaning position, whereby the mask sheet 7 is cleaned.

During such a series of printing operations, the squeegee mechanism 5 moves both squeegees 9a and 9b to Y.
It is driven so as to apply the paste while reciprocating in the axial direction and switching the squeegee used during forward and backward movements.

The specific switching operation will be described below based on the timing chart of FIG. 4 with reference to FIGS. 5 to 7, and its operation will be described together.

At time t0 in FIG. 4, the state of FIG. 5 (a) is shown. That is, the state is shown in which the first squeegee 9a is pressed against the mask sheet. Also, hatching indicates paste.

From this state, the Y-axis servomotor 22 is operated to drive the girder member 5b at a predetermined moving speed, so that the second squeegee 9b slides on the mask sheet in the arrow direction (right direction). When the first squeegee 9a reaches the predetermined application end position by extending the paste (forward pressing paste state), the girder member 5b stops (time t1; FIG. 5).
(B)) After that, the operation proceeds to the squeegee switching operation.

First, at time t2, both squeegees 9a, 9b rise together with the elevating frame 10, and the beam member 5b moves again (moves to the right in FIG. 5) in the middle (time t3). As a result, both squeegees 9a and 9b slightly move to the downstream side in the application direction by the first squeegee 9a.
That is, as shown in FIGS. 5B and 5C, the first squeegee 9a rises obliquely upward from the application end point, so that the paste in the string-drawing state with the rise of the squeegee 9a is applied. Adhesion to a portion (a portion on the upstream side of the application end point by the first squeegee 9a; a portion on the left side in FIG. 5) is prevented.

Next, at time t4, the operating state of the air cylinder 12a is switched, whereby the first squeegee 9a rises to a height position in line with the second squeegee 9b, and further t
At time 5, the girder member 5b moves, and the squeegees 9a and 9b are once in opposite directions, that is, in the opposite direction to the application direction by the first squeegee 9a (downstream side in the application direction by the second squeegee 9b;
It is slightly returned to the left side in FIG. 5 (FIG. 5 (d),
(E)). Specifically, as shown in FIG. 5 (e), the girder member 5b is moved so that the second squeegee 9b is located right above the paste collecting portion on the mask sheet.

At time t6, the operating state of the air cylinder 12b is switched and the second squeegee 9b is lowered to the predetermined height position (FIG. 6 (a)). 9b is integrally the second squeegee 9b
While moving to the upstream side (the right side in FIG. 5) in the coating direction, the elevating frame 10 descends at the same time. As a result, as shown in FIGS. 6B and 6C, the second squeegee 9b comes into contact with the predetermined contact point P on the mask sheet while descending diagonally.

That is, in this way, the second squeegee 9
By bringing b into contact with the contact point P, the paste attached to the tip of the second squeegee 9b (attached paste)
In the case where the second squeegee 9b moves to the contact point when the second squeegee 9b hangs down or drops, as shown in FIG. It will adhere to the downstream portion. Therefore, at the contact point P, it is possible to effectively prevent the attached paste from wrapping around to the rear side of the second squeegee 9b, that is, the upstream side in the coating direction.

When the second squeegee 9b comes into contact with the contact point P in this way, the elevating frame 10 is further lowered at the time t8, whereby the second squeegee 9b is pressed against the mask sheet 7 with a predetermined pressure (see FIG. d)). Then, when such a pressure adjusting operation is completed, the girder member 5b moves at time t9, and as shown in FIG.
While b slides on the mask sheet, the coating operation by the squeegee 9b is started. The time axis in FIG. 4 is a deformed display, and the printing time (t0 to t1 and t9 to t10) and the time interval from t1 to t9 after printing are set to be substantially equal.

Although the squeegee switching by the first squeegee 9a after the coating operation is completed has been described above, the squeegee switching by the second squeegee 9b after the coating operation is completed is performed in the same manner. That is, after time t10, the squeegee replacement corresponding to time t1 to time t9 and the operation corresponding to the load control are performed (in this case, the display of the first squeegee 9a and the second squeegee 9b in FIG. 4 is switched. ). In the above operation, the printing completed substrate W and the unprinted substrate W are exchanged using the time points t1 to t9.
By adjusting the time interval from 1 to t2, the timing with the replacement time of the substrate W can be adjusted.

As described above, in the screen printing machine, when the squeegees 9a and 9b are switched, the squeegee 9a (or 9b) is changed to the squeegee 9a (or 9) as described above.
Paste application direction by b) It is made to descend diagonally from the downstream side to the upstream side to contact the contact point P, thereby preventing the adhered paste from wrapping around the rear side of the squeegees 9a and 9b at the contact point P. Therefore, the problem caused by the adhering paste wrapping around the squeegees 9a and 9b, that is, the adhering paste is dragged from the back as the squeegee moves, and passes through the applied portion.
As a result, it is possible to effectively solve the problem that the uniformity of the paste thickness is hindered (unevenness of coating occurs).

In particular, in the conventional apparatus of this type, when the substrate is separated from the mask sheet due to coating unevenness, the paste in the thick portion is at the bottom end of the opening (through hole) of the mask sheet. When the next substrate is overlaid on the mask sheet, the paste spreads between the mask sheet and the substrate W and sticks out of the print pattern formed by the openings to print the paste, or The contact pressure when the squeegee passes through many parts becomes larger than other parts, and as a result,
The paste spreads from the opening of the mask sheet between the mask sheet and the substrate, and similarly, printing defects may occur, but according to the screen printing machine of the above embodiment, the uneven coating of the paste is eliminated as described above. Alternatively, since it can be reduced, it is possible to effectively prevent the occurrence of such a printing defect and improve the print quality.

Moreover, before lowering the squeegees 9a and 9b to the contact point P, the squeegees 9a and 9b are once returned in the opposite direction, that is, in the direction opposite to the lowering direction in the Y-axis direction (see FIG. e)), and thereafter, the squeegees 9a and 9b are lowered, which is advantageous in terms of space.

That is, after the application operation by the first squeegee 9a (or the second squeegee 9b) is completed, the squeegee 9a is
(Or 9b) may be raised and the second squeegee 9b (or the first squeegee 9a) may be lowered from that point in an oblique direction. However, in this case, the second squeegee 9b is lowered diagonally. It is necessary to set the contact point P farther from the application completion point, and a lot of space is required outside the application completion point. On the other hand, if the squeegees 9a and 9b are once returned in the opposite directions and then the second squeegee 9b is lowered in the oblique direction as described above, the contact point P is located at a position close to the application completion point.
Can be set, and the space outside the application completion point can be small. Therefore, the operations of the squeegees 9a and 9b as described above can be performed in a small space.

In this printing press, when the squeegees 9a, 9a are separated from the mask sheet 7 after the coating operation is completed, the squeegees 9a, 9b are raised obliquely upward toward the downstream side in the coating direction as described above. This makes the squeegee 9
Since it is prevented that the attached paste in the stringed state due to the rise of a and 9b is attached to the already-applied portion, the printing quality can be improved in this respect as well.

The screen printing machine described above is
It is one embodiment of the screen printing machine according to the present invention, and its specific configuration can be appropriately changed without departing from the scope of the present invention.

For example, the lowering operation of each squeegee 9a (or h9b) at the time of squeegee switching is performed by the squeegee 9a (or 9).
It is only necessary to move diagonally from the downstream side toward the upstream side in the paste application direction according to b), and its specific operation does not necessarily have to be the same as that of the embodiment. For example, depending on the clay of the paste used, the squeegees 9a, 9b
It is considered that the way of adhering the paste to the squeegee also changes, so the squeegees 9a and 9b are lowered so that the squeegees 9a and 9b can be effectively prevented from wrapping around to the rear side of the squeegees 9a and 9b. You can do it like this.

[0061]

As described above, according to the present invention, in the screen printing machine, when the application of the solder paste is started,
Place the squeegee at the specified retracted position above the mask sheet,
Application direction by the squeegee Since the squeegee is configured to descend diagonally from the downstream side toward the upstream side to contact a predetermined contact point on the mask sheet, for example, when the squeegee is lowered from the retracted position to the contact point. In addition, it is possible to effectively prevent the solder pace attached to the tip end of the squeegee from wrapping around and adhering to the rear side of the squeegee. Therefore, it is possible to effectively avoid the phenomenon that the solder paste that has sneak up to the rear side of the squeegee is dragged by the movement of the squeegee and then passes through the applied portion, resulting in non-uniform paste thickness of the substrate. This makes it possible to improve the print quality.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing a screen printing machine according to the present invention.

FIG. 2 is a schematic plan view of a frame member for explaining the arrangement of sensors for detecting a mask sheet.

FIG. 3 is a block configuration diagram showing a part mainly controlling driving of a squeegee mechanism in a control system of the screen printing machine.

FIG. 4 is a timing chart for explaining a squeegee switching operation.

FIG. 5 is a schematic diagram illustrating a squeegee switching operation.

FIG. 6 is a schematic diagram illustrating a squeegee switching operation.

FIG. 7 is a schematic diagram showing a state in which a squeegee is in contact with a contact point on a mask sheet.

FIG. 8 is a schematic diagram illustrating a squeegee switching operation in a conventional screen printing machine.

FIG. 9 is a schematic view showing a state in which a squeegee is in contact with a contact point on a mask sheet in a conventional screen printing machine.

[Explanation of symbols]

9a 1st squeegee 9b Second squeegee 30 control device 31 axis control means 32 size determination means 33 storage means 34 Main control means 35 input means

Claims (4)

[Claims] 1. A screen printing machine for spreading a solder paste supplied onto a mask sheet by moving a squeegee along the mask sheet to apply the paste to a substrate laminated on the mask sheet, wherein the squeegee is used as a mask sheet. It has moving means for moving in parallel horizontal and vertical directions, and drive control means for controlling the drive of this moving means, and this drive control means comprises:
At the start of the paste application operation, the squeegee at a predetermined retracted position above the mask sheet is obliquely lowered from the downstream side to the upstream side in the paste application direction of the squeegee to contact a predetermined contact point on the mask sheet. A screen printing machine characterized by being configured as follows. 2. The screen printing machine according to claim 1, wherein the drive control unit vertically moves the squeegee straight down from the retracted position and horizontally moves the squeegee upstream in the paste application direction. A screen printing machine characterized in that the squeegee is descended in an oblique direction by alternately repeating the operation and the operation. 3. The screen printing machine according to claim 1, wherein a pair of squeegees are arranged side by side in the paste application direction as the squeegee, and both squeegees are moved forward and backward while integrally reciprocating. While applying the solder paste to the substrate while properly using the squeegee, the drive control means, after the paste application operation by the squeegee on one side is completed, raises the squeegee on the one side to the retracted position, and thereafter, A screen printing machine characterized in that both squeegees are once returned to the upstream side in the paste application direction by the squeegee on one side, and then the squeegee on the other side is lowered to the contact point. 4. The screen printing machine according to claim 1, wherein the drive control means, after the paste application operation by the squeegee is completed, moves the squeegee diagonally to the downstream side in the paste application direction by the squeegee. A screen printing machine configured to move the squeegee to the retracted position while moving up.