JP2003182044A - Screen printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a screen printer having a cleaning mechanism capable of efficiently and surely removing a solder paste adhered to a printing screen. <P>SOLUTION: The screen printer comprises a screen support frame 1 supporting a printing screen 2 and horizontally reciprocating, a net-like cleaning sheet 6 for wiping off the paste adhered to the lower surface by bringing the sheet 6 into contact with the lower surface of the screen 2 and reciprocating, a holding means 7 for holding the sheet 6 in the contact state with the lower surface in such a manner that the means 7 has a block member 71 having a flat surface 71a opposed to the lower surface, a pair of cleaning squeegees 72 disposed oppositely via gaps 73 to both sides of the member 71 of reciprocating and having an elastically deformable end 72a, and a suction unit 10 connected to communicate with the gaps 73, distal ends of the surface 71a and the ends 72a press the sheet 6 to the lower surface of the screen 2, and the unit 10 dives to suck the screen 2 via the sheet 6. <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 printing a solder paste on a circuit board, and more particularly to a screen printing machine having a cleaning mechanism for automatically removing the solder paste adhering to the printing screen.

[0002]

2. Description of the Related Art In a screen printing machine for printing a solder paste on a circuit board through a printing screen, generally, as the printing is repeated, the residue of the solder paste adheres to the openings and the printing surface of the printing screen. However, if printing is continued in that state, a predetermined amount of solder paste will not be printed at a predetermined position on the circuit board, causing bleeding or blurring of the print pattern, and eventually causing defects such as solder balls or bridges, Alternatively, since the circuit board and the printing screen are inadvertently brought into close contact with each other and a trouble may occur at the time of separation after printing, it is necessary to regularly clean the printing screen. This cleaning was previously performed manually, but in recent years, a cleaning mechanism has been provided in the screen printing machine itself to be automatically performed.

As a conventional example of the cleaning mechanism,
As shown in FIG. 3, largely, the screen support frame 10 that moves in the horizontal direction (the left direction shown by the arrow C in FIG. 3).
The cleaning sheet 106 is in the form of a mesh that is in contact with the lower surface of the printing screen 102 that is supported by the sheet 1, and a holding unit 107 that holds the upper surface of the cleaning sheet 106 and the lower surface of the printing screen 102 in contact with each other. The holding means 107 has a printing screen 102
Block member 1 having a flat surface 171a facing the lower surface of the
71 and one side of the block member 171 on the front side (the left side in FIG. 3) in the moving direction of the screen support frame 101, with a gap 173, and projecting toward the lower surface of the cleaning sheet 106 and elastic. Cleaning squeegee 172 having deformable end 172a
And a suction device (not shown) that is a suction unit that is connected in communication with the gap 173.

According to this structure, when the screen support frame 101 starts to move, the opening 102a of the printing screen 102, that is, the attached solder paste (not shown) is located on the rear side in the moving direction of the screen support frame 101 (see FIG. Cleaning sheet 10 so that it is located on the right side in 3)
6 and the holding means 107 (on the left side in FIG. 3), the flat surface 171a of the block member 171 and the tip of the end 172a of the cleaning squeegee 172 press the lower surface of the cleaning sheet 106 and the upper surface thereof and the printing screen 102. While keeping the lower surface of the printer in a contact state, the suction device is driven to suck the printing screen 102 through the cleaning sheet 106 to further strengthen the contact state.

When the screen support frame 101 moves horizontally (leftward in FIG. 3) in this state, the solder paste attached to the lower surface of the printing screen 102 is
The cleaning sheet 106 is wiped off in sequence.
Here, the solder paste adhering to the opening of the printing screen 102 is sucked through the mesh of the cleaning sheet 106 by driving the suction device, sucked and removed into the gap 173, and wiped off and deposited on the cleaning sheet 106. Part of the solder paste is also removed by suction.

[0006]

However, in the conventional screen printing machine as described above, since the movement of the printing screen with respect to the cleaning sheet is in only one direction,
The cleaning effect is low compared to the case of manually scrubbing the cleaning sheet on the printing screen.Especially when the solder paste is stuck to the printing screen, the solder paste is moved by moving the printing screen once. There was a problem that it was difficult to wipe it off completely.

To solve this problem, the cleaning effect can be expected to be improved by repeating the movement of the printing screen a plurality of times, but the movement is only in one direction. In order to wipe off, the number of movements increases remarkably and efficiency becomes extremely poor.

Therefore, the present invention has been made in view of the above problems, and provides a screen printing machine having a cleaning mechanism capable of efficiently and reliably removing the solder paste attached to the printing screen. The purpose is.

[0009]

In order to achieve the above object, a screen printing machine according to the present invention relatively reciprocates while contacting one surface of a printing screen,
A net-like cleaning sheet for wiping the solder paste adhering to the one surface is provided, and a holding means for reciprocally moving relative to the cleaning sheet and holding the cleaning sheet in contact with the one surface. In the screen printing machine, the holding means is arranged so as to face a block member having a flat surface facing the one surface and a gap on both sides of the block member in the reciprocating direction. A pair of cleaning squeegees each having an end portion that is elastically deformable and projecting toward the surface of the block member, and a suction unit that is connected in communication with each of the gaps. The flat surface of the block member and each of the cleaning squeegees. The tip of the end portion of the presses the cleaning sheet against one surface of the printing screen, Pull stage is adapted to attract the printing screen through the cleaning sheet is driven.

Further, in consideration of practicality, the screen supporting frame which supports the printing screen and reciprocates in the horizontal direction, and the screen supporting frame which is in contact with the lower surface of the printing screen is attached to the lower surface by the reciprocating movement of the screen supporting frame. A screen printing machine comprising: a mesh-like cleaning sheet for wiping off solder paste; and a holding means for holding the cleaning sheet in contact with the lower surface, wherein the holding means is a block having a flat surface facing the lower surface. A member, a pair of cleaning squeegees, which are arranged opposite to each other on both sides of the block member in the direction of reciprocal movement with a gap, and project toward the lower surface and have elastically deformable ends. Suction means connected in communication with each of the gaps. It is preferable that the tip of the end portion of the leaning squeegee presses the cleaning sheet against the lower surface of the printing screen, and the suction unit is driven to suck the printing screen through the cleaning sheet. .

With this structure, the solder paste attached to the printing screen is wiped off by the cleaning sheet in the reciprocating direction, that is, in two directions.

Here, there is a possibility that the solder paste may be deposited on the cleaning sheet located outside the tip of the end portion of the cleaning squeegee that precedes the reciprocating movement by the reciprocating movement, and the deposition of the solder paste is remarkable. Then, the solder paste is left behind on the printing screen at both ends of the reciprocating movement. From the viewpoint of preventing this, for example, the end portions of the cleaning squeegees are tilted inwardly of each other so that the solder paste in the appearance of the reciprocating movement is received on the cleaning sheet inside the cleaning squeegee. A notch may be provided in each of the cleaning squeegees so that the cleaning squeegee is elastically deformed.

Further, in order to prevent the solder paste from being deposited on the cleaning sheet located outside the tip of the end of the preceding cleaning squeegee during the reciprocating movement, the solder paste attached to the lower surface of the printing screen is placed inside the cleaning squeegee. Each cleaning squeegee can be individually retracted with respect to the printing screen for the purpose of surely receiving it on the cleaning sheet, and the cleaning sheet is pressed by the tip of the end of the retracted cleaning squeegee. Is preferably released.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the screen printing machine of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic front view showing a main part of the screen printing machine of the present invention, and FIG. 2 is an enlarged view showing the cleaning mechanism of FIG. In the figure, the same reference numerals are given to the parts having the same names and the same functions.

In FIG. 1, reference numeral 1 denotes a screen support frame for supporting a printing screen 2, which reciprocates in a Y-axis direction (direction of arrow A) extending horizontally in a machine frame (not shown) of the screen printing machine. It is movably supported and is moved by a driving means (not shown) such as a motor.
The printing screen 2 has an opening 2a for forming a printing pattern on a circuit board (not shown).

A screen cleaning unit 3 is arranged below the screen support frame 1. The screen cleaning unit 3 is provided with a frame 5 rotatably supported in a vertical plane on a machine frame of a screen printing machine via a support shaft 4. The frame 5 is provided on the lower surface of the printing screen 2. A long cleaning sheet 6 for wiping off the attached solder paste, and this cleaning sheet 6
Holding means 7 for holding the upper surface of the cleaning screen 6 in contact with the lower surface of the printing screen 2, feeding mechanisms 8a to 8d for feeding the cleaning sheet 6 in the length direction, and the cleaning sheet
Solvent supply means 9 for supplying a solvent for dissolving solder paste to
And are attached.

Here, the frame 5 is connected to a rod of an air cylinder (not shown). When the air cylinder is driven, the frame 5 rotates around the axis of the support shaft 4, and the holding means 7 cleans. A position where the upper surface of the sheet 6 and the lower surface of the printing screen 2 are held in contact with each other (a position shown by a solid line), and a position where the holding means 7 is spaced downwardly from the printing screen 2 together with the cleaning sheet 6 (in a two-dot chain line). The position shown) can be taken.

The cleaning sheet 6 is made of a breathable mesh-like material such as cloth, and is attached to the supply roller 8a of the feeding mechanism in a state of being wound into a roll, the conveying roller 8b and the solvent supply means. It is conveyed in the direction of the arrow B so as to pass through 9, the holding means 7, and the conveying roller 8c, and is taken up by the take-up roller 8d.

As shown in FIG. 2, the holding means 7 faces the lower surface of the printing screen 2 when the upper surface of the cleaning sheet 6 and the lower surface of the printing screen 2 are in contact with each other (the position shown by the solid line in FIG. 1). The block 71 having a flat surface 71a and the cleaning sheet 6 are arranged to face each other with gaps 73 and 73 on both sides (left and right in FIG. 2) of the block member 71 in the moving direction of the screen support frame 1. A pair of cleaning squeegees 72, 72 having elastically deformable end portions 72a projecting toward the lower surface of the nozzle, and a suction device 10 (see FIG. 1) which is a suction means connected to the gaps 73, 73 for communication. It consists of

Therefore, the flat surface 71a of the block member 71 and the end portion 72 of each cleaning squeegee 72 that elastically deforms.
While the tip of a presses the lower surface of the cleaning sheet 6 to bring the upper surface and the lower surface of the printing screen 2 into contact with each other,
The suction device 10 is driven to suck the printing screen 2 through the mesh-like cleaning sheet 6 to strengthen the contact state.

Here, a notch 72b is provided inside each cleaning squeegee 72 so that the ends 72a of each cleaning squeegee 72 are tilted inward and elastically deformed due to stress concentration. This is because in the cleaning operation described later in detail, when the reciprocating movement is performed, the solder paste in a state of being deposited on the cleaning sheet 6 positioned outside the tip of the end portion 72a of the preceding cleaning squeegee 72 is inside the cleaning squeegee 72. It is to be easily received on the cleaning sheet 6 in.

The solvent supplying means 9 is a cleaning sheet 6.
A nozzle 9a for discharging a solvent such as a general alcohol for dissolving the solder paste, which is arranged in the preceding stage of the holding means 7 in the transport path of No. 7, a tank (not shown) for storing the solvent, and the nozzle 9a and the tank are connected for communication. The cleaning sheet 6 is composed of a solvent intake pipe 9b, a solenoid valve (not shown) provided in the path of the solvent intake pipe 9b for adjusting the discharge amount of the solvent, and the like. It is designed to be discharged and supplied. By selectively controlling the opening and closing of the solenoid valve, it is possible to select a wet type in which the solvent is supplied to the cleaning sheet 6 or a dry type in which the solvent is not supplied.

Although not shown, a circuit board for screen printing is placed on the side of the screen cleaning unit 3 and is movable in the X-axis direction extending in the vertical and horizontal directions. A substrate support table rotatable in a horizontal plane and a conveyer conveyor for supplying a circuit board to the substrate support table and conveying the printed circuit board to the next step are provided above the printing screen 2. Is provided with solder paste supplying means for supplying the solder paste onto the printing screen 2, and a printing means having a squeegee for sweeping the solder paste supplied by the solder paste supplying means onto the opening 2a of the printing screen 2. Has been.

The operation of the screen printing machine having such a configuration will be described below. First, the printing operation will be described.
When the circuit board is supplied onto the substrate support table by the transfer conveyor, the substrate support table is raised to the printing position. Then, the solder paste is supplied onto the printing screen 2 supported by the screen support frame 1 by the solder paste supply means, and the squeegee sweeps the solder paste onto the opening 2 a of the printing screen 2 to perform printing. At this time,
A part of the solder paste pushed into the opening 2a may ooze to the lower surface side of the printing screen 2 and adhere to the lower surface of the printing screen 2. Then, the board supporting table descends and the circuit board separates from the printing screen 2,
At this time, a part of the solder paste may remain in the opening 2a of the printing screen 2.

Next, the cleaning operation of the printing screen 2 will be described. After the above printing operation is completed, the screen support frame 1 is moved to a predetermined position (cleaning start position) above the screen cleaning unit 3, and then the screen cleaning unit 3 is rotated upward around the axis of the support shaft 4. , Drive the suction device 10. As a result, as shown in FIG. 2, the cleaning sheet 6 is pressed against the lower surface of the printing screen 2 by the flat surface 71a of the block member 71 and the tips of the end portions 72a of the elastically deformable cleaning squeegees 72 to be in contact with each other, The suction state of the suction device 10 makes the contact state stronger.

Here, the cleaning start position is not particularly limited, but in FIG. 2, for example, it is a position corresponding to one of both ends of the reciprocating movement of the screen support frame 1 described later, and the opening of the printing screen 2. The portion 2a, that is, the portion to which the solder paste (not shown) is attached is set so as to be located on the right side of the cleaning sheet 6 and the holding means 7. Further, prior to these cleaning operations, the cleaning sheet 6 is fed by the feeding mechanisms 8a to 8d, and the cleaning sheet 6 to which the solvent is supplied is positioned on the holding means 7.

Next, when the screen support frame 1 is moved to the left in that state, the solder paste attached to the lower surface of the printing screen 2 is held by the holding means 7 in the cleaning sheet 6 in contact with the printing screen 2. Are wiped off in sequence.

Here, the cleaning squeegee 72 on the right side
On the cleaning sheet 6 located outside the tip of the end portion 72a of the sheet, the wiped solder paste is gradually deposited. However, as the screen support frame 1 moves leftward, the edge of the cleaning squeegee 72 on the right side is A frictional force to the left acts on the tip of the portion 72a via the cleaning sheet 6, so that the end portion 72a of the cleaning squeegee 72 on the right side of the portion 72a tilts inward (leftward) about the notch 72b. It is elastically deformed, so that the deposited solder paste is received on the cleaning sheet 6 inside the cleaning squeegee 72 on the right side. Then, the wiped solder paste including the received solder paste is sucked through the mesh of the cleaning sheet 6 by driving the suction device 10, and the gap 7 is removed.
3 is sucked and removed.

The solder paste adhering to the opening 2a of the printing screen 2 is also sucked through the mesh of the cleaning sheet 6 by driving the suction device 10 and sucked and removed into the gap 73.

When the screen support frame 1 reaches the leftward moving end in this way, the moving direction of the screen support frame 1 is reversed while the contact state of the cleaning sheet 6 and the holding means 7 with the printing screen 2 remains unchanged. This time, the screen support frame 1 is moved to the right. Here, at the position of the moving end, the opening 2a of the printing screen 2, that is, all the portions where the solder paste (not shown) is completely wiped off and adhered to the left side of the cleaning sheet 6 and the holding means 7. It is set to be located.

As the screen support frame 1 moves to the right, the solder paste attached to the lower surface of the printing screen 2 is sequentially wiped off again by the cleaning sheet 6. In this case, the cleaning squeegee 7 on the right side described above
The function of 2 is performed by replacing the cleaning squeegee 72 on the left side.

When the screen support frame 1 reaches the moving end in the right direction and reciprocates once to return to the cleaning start position, the screen support frame 1 stops and the screen cleaning unit 3 rotates around the axis of the support shaft 4. The cleaning operation is completed by pivoting downwards and away from the printing screen 2. After that, the screen support frame 1 moves to a predetermined position during printing to prepare for the next printing operation, and the holding means 7
The feed mechanisms 8a to 8d are operated so that the new cleaning sheet 6 to which the solvent has been supplied is positioned above to prepare for the next cleaning operation.

As described above, the solder paste attached to the printing screen 2 is wiped off by the cleaning sheet 6 in the left and right directions of the reciprocating movement, that is, two directions, so that the solder paste can be efficiently and completely removed. In particular, it is effective when the solder paste is fixed to the printing screen 2.

In the cleaning operation described above, the screen support frame 1 is not limited to one reciprocation, but it is also possible to set it so that it reciprocates a plurality of times. This is because the solder paste attached to the printing screen 2 is completely removed. It is effective when it is necessary to remove it completely.

Next, another embodiment of the present invention will be described. The feature of this embodiment is that in the cleaning operation of the above embodiment, printing is performed so that the solder paste is not deposited on the cleaning sheet 6 located outside the tip of the end 72a of the preceding cleaning squeegee 72 during reciprocating movement. The solder paste attached to the lower surface of the screen 2 is used to clean the cleaning sheet 6 inside the cleaning squeegee 72.
In addition to the configuration of the above embodiment, each cleaning squeegee 72 can be individually retracted with respect to the printing screen 2 in the point that it is surely received.

That is, referring to FIG. 2,
When the screen support frame 1 is moved to the left, the cleaning squeegee 72 on the right side that precedes the screen support frame 1 is retracted downward, and the cleaning squeegee 7 on the right side is moved downward.
The cleaning sheet 6 located at the tip of the second end 72a
And the printing screen 2 are released, and the cleaning squeegee 7 on the flat surface 71a of the block member 71 and on the left side is released.
The contact state is maintained by pressing the tip of the second end 72a. By doing so, the solder paste attached to the lower surface of the printing screen 2 is not wiped off on the cleaning sheet 6 located at the tip of the end portion 72a of the right cleaning squeegee 72, and the right cleaning squeegee 72 is provided.
The sheet is received on the cleaning sheet 6 inside the sheet, that is, on the flat surface 71a of the block member 71, and is wiped off here.

On the other hand, when moving the screen support frame 1 to the right, contrary to the above, the left cleaning squeegee 72, which precedes the movement of the screen supporting frame 1, is retracted downward, and the cleaning squeegee 72 on the left side of the cleaning squeegee 72 is moved downward. End 72a
The contact state between the cleaning sheet 6 located at the tip of the block and the printing screen 2 is released, and the flat surface 7 of the block member 71 is released.
1a and the end 72a of the cleaning squeegee 72 on the right side
The contact state is maintained by pressing the tip of the. By doing this, the end portion 72 of the cleaning squeegee 72 on the left side is
On the cleaning sheet 6 located at the tip of a, the solder paste adhered to the lower surface of the printing screen 2 is not wiped off, and is received on the cleaning sheet 6 inside the cleaning squeegee 72 on the left side, that is, on the flat surface 71a of the block member 71. It is wiped off here.

Therefore, the solder paste does not deposit on the cleaning sheet 6 located outside the tip of the end 72a of each cleaning squeegee 72 preceding and following the reciprocating movement, and the screen support frame 1 does not deposit the solder paste by the reciprocating movement. The solder paste is not left on the printing screen 2 at both ends of the reciprocating movement of the.

Incidentally, as the construction in which each cleaning squeegee 72 can be individually retracted with respect to the printing screen 2 as described above, the cleaning sheet 6 and the holding means 7 are attached depending on the moving direction of the screen support frame 1. The amount of rod extension of the air cylinder that controls the rotating operation of the frame 5 is changed, or a rotary coaxial (not shown) is provided below the block member 71, and the holding means 7 is tilted around the rotary coaxial. It is enough to do.

In addition, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, even if the cleaning sheet and the holding means are reciprocally moved with respect to the printing screen (screen support frame), the same effect can be obtained. Further, the shape of the end of each cleaning squeegee is not particularly limited.

[0041]

As described above, according to the screen printing machine of the present invention, the screen is reciprocally moved while being in contact with one surface of the printing screen to wipe the solder paste adhering to the one surface. In a screen printing machine comprising: a cleaning sheet having a sheet-like shape; and a holding means that relatively reciprocates together with the cleaning sheet and holds the cleaning sheet in contact with the one surface, Of the block member and a block member having a flat surface facing the surface of the block member, and the block member is arranged so as to face both sides of the block member in the reciprocating direction with a gap, respectively, and protrudes toward the one surface and is elastically deformable. A pair of cleaning squeegees having ends,
Suction means connected to each of the gaps, and the flat surface of the block member and the tip of the end of each cleaning squeegee press the cleaning sheet against one surface of the printing screen. The suction means is driven to suck the printing screen through the cleaning sheet. Therefore,
The solder paste attached to the printing screen is wiped off by the cleaning sheet in the reciprocating direction, that is, in two directions, so that the solder paste can be efficiently and completely removed.

In the screen printing machine of the present invention, a screen supporting frame which supports the printing screen and reciprocates in the horizontal direction, and a reciprocating movement of the screen supporting frame while contacting the lower surface of the printing screen are provided on the lower surface. In a screen printing machine including a mesh-shaped cleaning sheet for wiping off the attached solder paste and a holding means for holding the cleaning sheet in contact with the lower surface, the holding means has a flat surface facing the lower surface. And a pair of cleaning squeegees, which are arranged facing each other on both sides of the block member in the direction of the reciprocating movement with a gap, and which have end portions that project toward the lower surface and that are elastically deformable. And suction means connected in communication with each of the gaps. Since the tip of the end of each cleaning squeegee presses the cleaning sheet against the lower surface of the printing screen, the suction unit is driven to suck the printing screen through the cleaning sheet. , Equipped with a practical cleaning mechanism. Further, since the solder paste attached to the printing screen is wiped off by the cleaning sheet in the reciprocating direction, that is, in two directions, the solder paste can be efficiently and completely removed.

Here, for example, when each cleaning squeegee is provided with a notch so that the end portions of each cleaning squeegee are tilted inward relative to each other and elastically deformed, the cleaning squeegee preceding the cleaning squeegee is reciprocated. Since the solder paste that appears to be deposited on the cleaning sheet located outside the tip of the end can be received on the cleaning sheet inside the cleaning squeegee, the solder paste remains on the printing screen at both ends of the reciprocating movement. It does not get lost and can be reliably removed.

Further, each of the cleaning squeegees can be individually retracted with respect to the printing screen, and the pressing of the cleaning sheet by the tip of the retracted end of the cleaning squeegee is released. When this occurs, the preceding cleaning squeegee can be retracted during reciprocating movement, and the contact state between the cleaning sheet located at the tip of the end of the cleaning squeegee and the printing screen can be released. The attached solder paste can be reliably received on the cleaning sheet inside the cleaning squeegee, which leads to more reliable removal of the solder paste.

[Brief description of drawings]

FIG. 1 is a front view showing a main part of a screen printing machine according to the present invention.

FIG. 2 is an enlarged view showing a cleaning mechanism in the screen printing machine of FIG.

FIG. 3 is an enlarged view showing a cleaning mechanism in a conventional screen printing machine.

[Explanation of symbols] 1 screen support frame 2 printing screen 2a opening 3 Screen cleaning unit 4 spindles 5 frames 6 cleaning sheet 7 holding means 8a-8d feeding mechanism 9 Solvent supply means 9a nozzle 9b Solvent intake pipe 10 Suction device 71 Block member 71a plane 72 Cleaning Squeegee 72a end 72b Notch

Continued front page    F term (reference) 2C035 AA05 FA22 FC01 FC07                 2C250 FA06 FB02 FB03 FB07 FB12                       FB17                 5E319 BB05 CD29 GG15

Claims (4)

[Claims] 1. A mesh-like cleaning sheet that relatively reciprocates while contacting one surface of a printing screen to wipe off solder paste adhering to the one surface, and reciprocally relatively with the cleaning sheet. In a screen printing machine provided with a holding unit that moves and holds the cleaning sheet in contact with the one surface, the holding unit includes a block member having a flat surface facing the one surface, A pair of cleaning squeegees, which are opposed to each other in the direction of the reciprocating movement of the block member with a gap, respectively, have a pair of cleaning squeegees protruding toward the one surface and having elastically deformable ends, and the gaps. And a suction means connected to and connected to the flat surface of the block member and the tips of the end portions of the cleaning squeegees. Screen printing machine, characterized in that said with pressing the cleaning sheet on one surface of the printing screen, wherein the suction means is driven to suck the printing screen through the cleaning sheet. 2. A screen support frame that supports a printing screen and reciprocates in the horizontal direction, and a mesh shape that wipes the solder paste adhering to the lower surface by reciprocating the screen support frame while contacting the lower surface of the printing screen. A cleaning sheet and a holding means for holding the cleaning sheet in contact with the lower surface, the holding means includes a block member having a flat surface facing the lower surface, and the block member. And a pair of cleaning squeegees, which are arranged opposite to each other in the direction of the reciprocating movement with a gap, respectively, and which project toward the lower surface and have elastically deformable end portions, and are connected to communicate with the gaps. Suction means, and the flat surface of the block member and the end of each cleaning squeegee. The tip, while pressing the cleaning sheet to the lower surface of the printing screen, a screen printing machine, characterized by sucking the printing screen through the cleaning sheet said suction means is driven. 3. The screen according to claim 1, wherein each cleaning squeegee is provided with a notch so that the end portions of each cleaning squeegee are tilted inward and elastically deformed. Printer. 4. The cleaning squeegee can be individually retracted from the printing screen, and the pressing of the cleaning sheet by the tip end of the retracted cleaning squeegee is released. The screen printing machine according to any one of claims 1 to 3.