JPH04284249A - Screen printer and screen printing method - Google Patents

Abstract

PURPOSE:To provide a screen printer and a printing method, in which a printing agent is housed in a sealed vessel and printing is conducted on a plate to be printed under the state in which a contact with atmospheric air is interrupted while the printing agent is not left on a screen. CONSTITUTION:Creamy solder 70 interrupted from atmospheric air and housed in a syringe 72 is agitated in viscosity proper to printing by an agitating roller 124 in a casing 90, discharged from a discharge opening 129 by the pushing force of nitrogen gas fed to the syringe 72 and its own weight, and printed on a printed board by a squeegee member 128. A squeegee 76 can be separated from a screen 26 without leaving creamy solder 70 on the screen 26 by lifting the squeegee 76 while being moved in the horizontal direction.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a screen printing machine and a screen printing method for printing a printing agent such as an adhesive or cream solder on a predetermined portion of a printed board such as a printed circuit board. It concerns handling.

0002

[Prior Art] A screen printing machine prints a printing agent at a predetermined position on a printing board, such as when applying adhesive or creamy solder to the positions where electronic components are bonded or where lead wires are connected on a printed circuit board. It is a device, and is published in Utility Model Application Publication No. 1-63169.
It is known from the publication No. This screen printing machine includes a printing plate support, a screen support, and a squeegee device, and by moving the squeegee of the squeegee device over the screen supported by the screen support,
A printing agent is printed on a printing plate supported by a printing plate support. The printing agent is placed on the screen before printing starts, and is printed on the printing plate through small holes formed in the screen while being moved by a squeegee.

0003

However, when printing is performed by placing the printing agent on the screen in this way, various problems occur. The printing agent placed on the screen oxidizes when exposed to the atmosphere. Therefore, for example, when creamy solder is used as a printing agent, problems arise such as the formation of solder balls during reflow of the creamy solder due to oxidation and a decrease in wettability when the solder is melted. Moreover, creamy solder consists of solder grains and flux for making the solder creamy. Flux contains pine tar, alcohol, binder, etc., and when kneaded, it mixes with solder particles to obtain a creamy solder with a viscosity suitable for printing.However, when placed in the atmosphere, the alcohol and other solvents evaporate, causing the viscosity to decrease. This increases the solder's strength, making it impossible to print smoothly, and the solder's fixing strength decreases, potentially causing the electronic components to shift. Furthermore, in the case of printing agents such as creamy solder whose properties change due to contact with the atmosphere, such as oxidation or increased viscosity, even if they remain on the screen after printing, they cannot be used in the same way as unused printing agents. It can't be done and it's a waste. Furthermore, screens are replaced when the type of printed circuit board changes, but when printing on one type of printed circuit board is finished, there is usually creamy solder left on the screen, and when the screen is replaced, It is necessary to collect this remaining printing agent. However, this collection work has traditionally been done by workers, which has been a bottleneck in automating screen replacement.

[0004] The first invention has been made with the object of providing a screen printing machine capable of printing on a printing plate in a state where the printing agent is shielded from the atmosphere. The second invention has been made with the object of providing a screen printing method capable of printing without leaving any printing agent on the screen.

[0005]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the first invention provides a squeegee device for a screen printing press that is equipped with the printing plate support stand, a screen support stand, and a squeegee device. a closed container that is housed in a state that is shielded from the atmosphere; a squeegee that is connected to the closed container and has a printing agent discharge port that is in close contact with the screen;
The present invention is characterized in that it includes a moving device that moves the squeegee on the screen. Note that the term "printing agent discharge port in close contact with the screen" as used herein includes not only a case where the printing agent discharge port contacts the screen without any gap at all, but also a state in which the print agent discharge port contacts the screen with a slight gap. It is only necessary that the printing agent outlet is in substantially close contact with the screen so that the printing agent does not leak out from the printing agent outlet. The screen printing method of the second invention is
In order to solve the above problems, the printing agent is printed on the printing plate by moving the squeegee on the screen, and the squeegee is moved in a direction parallel to the screen and at a right angle to the screen to separate it from the screen. It is characterized by causing

[0006]

[Operation] In the screen printing machine of the first invention, the printing agent contained in the closed container is discharged from the printing agent discharge port and printed on the printing plate. The printing agent contained in the closed container does not come into contact with the atmosphere, and since the printing agent outlet is brought into substantially close contact with the screen, the printing agent inside the printing agent outlet also does not come into contact with the atmosphere. The printing agent is printed on the printing plate without being exposed to the atmosphere. According to the screen printing method of the second invention, the squeegee is separated from the screen in a direction parallel to the screen and a direction perpendicular to the screen. By separating the squeegee in this manner, less printing agent remains on the screen than when the squeegee is separated in a direction perpendicular to the screen.

[0007]

[Effects of the Invention] As described above, according to the screen printing machine of the first invention, it is possible to print on a printing plate without bringing the printing agent into contact with the atmosphere, and it is possible to avoid problems caused by oxidation of the printing agent. . Furthermore, in the case of a printing agent containing a solvent such as alcohol, such as creamy solder, the viscosity does not change due to evaporation of the solvent, and printing can be performed smoothly in the same state from the start to the end of printing. Furthermore, since the printing agent inside the closed container does not come into contact with the atmosphere, its properties remain unchanged, and even if printing agent remains inside the closed container at the end of printing, it can be used for the next printing. Since no printing agent remains and is wasted, printing costs can be reduced. Furthermore, since the printing agent is printed with the printing agent discharge port substantially in close contact with the screen, the printing agent does not protrude in the direction crossing the direction of movement of the squeegee, and the printing agent is stored in the closed container. The effect that all of the printing agent is used for printing without waste can be obtained.

According to the screen printing method of the second invention,
Almost no printing agent remains on the screen when the squeegee is separated from the screen, eliminating waste of printing agent, eliminating the need to collect printing agent when replacing the screen, and allowing automatic screen replacement. The effect that is possible can be obtained.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples in which the first and second inventions are applied to a printed circuit board screen printing machine and a printing method will be described below in detail with reference to the drawings. FIG. 4 is a diagram showing a screen positioning support device 10 and a squeegee device 12 of a printed circuit board screen printing machine. These screen positioning support device 10 and squeegee device 12
is provided above a printed circuit board positioning and supporting device, a board conveyor, and a board holding device (not shown). The printed circuit board positioning and supporting device positions the printed circuit board 16 that has been conveyed by the board conveyor, and also suctions and fixes the printed circuit board 16 onto the board support stand 18 with a vacuum while the printed circuit board 16 is being held down from above by the board holding device. This device moves the substrate support stand 18 between a printing position and a non-printing position by raising and lowering it. These devices are
This is the same as the screen printing machine described in Japanese Utility Model Application Publication No. 1-63169, and illustrations and detailed description thereof will be omitted.

The frame 20 of the screen positioning and supporting device 10 is rotatably provided on a support stand (not shown) on which the printed circuit board positioning and supporting device and the board holding device are provided, about a horizontal shaft 22. frame 20
A part of the screen is used as a screen support stand 24, and on the screen support stand 24, a screen 26 and a screen frame 28 fixed to its periphery are positioned by a positioning block 30 and a dial gauge 32, and fixed by a fixed cylinder 34. It is now possible to do so. The position of the screen frame 28 is accurately adjusted by bringing the adjustment bolt 36 screwed into the screen frame 28 into contact with the dial gauge 32 and rotating the adjustment bolt 36 while observing the instructions. Thereby, the large number of small holes formed in the screen 26 can be accurately aligned with the areas on the printed circuit board 16 to which creamy solder is to be applied.

The squeegee device 12 includes two guide rods 50 that are disposed horizontally and parallel to each other on the frame 20 of the screen positioning and supporting device 10, and a slide 52 that slides on the guide rods 50. ing. Two guide rods 54 (only one is shown in FIG. 4) are fitted into the slide 52 so as to be slidable in the vertical direction, and a squeegee unit 56 is attached to the lower end of the guide rods 54 (only one is shown in FIG. 4). It is raised and lowered by a lifting cylinder 58 provided at 52. The slide 52 also has a nut 6
2 is fixed, and a feed screw 64 rotatably but immovably attached to the frame 20 is screwed together. When the feed screw 64 is rotated by a servo motor 66, the squeegee unit 56 is rotated. It is linearly reciprocated along the screen 26. In this embodiment, a guide rod 50, a slide 52,
The nut 62, feed screw 64, and servo motor 66 constitute a moving device.

As shown in FIG. 1, the squeegee unit 56 includes a syringe 72 as a closed container containing creamy solder 70, an agitator 74, and a squeegee 76. At the lower end of the guide rod 54, there are shown FIGS. 2 and 3.
As shown in FIG.
A connecting plate 84 connecting a pair of L-shaped support arms 82 is attached to a bracket 80 having a U-shaped cross section fixed to the support frame 78 so as to be rotatable around a horizontal axis 85. It is being The rotational position of the connecting bar 84 is defined by two adjustment bolts 86 screwed into the bracket 80, thereby adjusting the horizontal position of the squeegee 76. A stirrer 74 is attached to the support arm 82.
A casing 90 is rotatably supported around a horizontal axis. Inside the casing 90, as shown in FIG.
A through hole 92 with a circular cross section extending in the width direction of the screen 26
The openings at both ends of the through hole 92 are each closed by a side plate 94, and a bush 96 that is fitted and fixed to the side plate 94 is rotatably fitted to the support arm 82.

The casing 90 has an upper surface and a through hole 9.
A communication hole 100 is formed that opens to the syringe 2, and a pair of engagement pieces 102 are fixed, so that the syringe 72 can be detachably attached. Syringe 7
2 has an opening 104 formed on its lower surface, and a pair of engagement protrusions 106 extending radially outward at the lower end of the opening 104.
is located above the communication hole 100, and the engagement protrusion 106 and the engagement piece 1
After the syringe 72 is placed on the casing 90 with the phase shifted from that of the syringe 72, the engagement protrusion 106 and the engagement piece 102 are engaged with each other by rotating the syringe 72 by a predetermined angle, and the syringe 72 is placed on the casing 90. It is attached. The creamy solder 70 housed in the syringe 72 is made of solder grains and a flux containing pine resin, alcohol, a binder, etc., and when the syringe 72 is attached to the casing 90, it passes through the opening 104 and the communication hole 100. It flows into the casing 90. Further, a float 108 is floated on the creamy solder 70 housed in the syringe 72. This float 108 is made up of a synthetic resin disk with an iron ring fitted around the outer periphery, and by detecting this ring with a magnetic switch 109 provided outside the syringe 72, the remaining amount of creamy solder 70 is detected. Ru. Furthermore, the syringe 72 is connected to a nitrogen gas supply source (not shown) through a connection port 110 provided at its upper end opening, a hose (not shown), etc., and nitrogen gas is supplied at 0.1
It is supplied at a pressure of ~0.5 kg/cm2, and the creamy solder 70 is pushed into the casing 90 not only by its own weight but also by the pushing force of the supplied nitrogen gas.

A rotary shaft 112 is fitted within the casing 90 so as to be rotatable about a horizontal axis. Rotating shaft 11
2 is rotatably supported by the bush 96, and one end protrudes from the bush 96 and has a pulley 114 fixed thereon, and is connected to a stirring motor 120 via a belt 116 and another pulley 118. Rotation is transmitted. A stirring roller 124 is attached eccentrically to a portion of the rotating shaft 112 inside the casing 90, and when the rotating shaft 112 is rotated by the stirring motor 120, the stirring roller 124 stirs the creamy solder 70.

As shown in FIG. 1, the casing 90 also has an opening 126 formed on its lower surface and long in the width direction of the screen 26, and an opening 126 on both edges parallel to the longitudinal direction of the opening 128. A squeegee member 128 is fixed. These squeegee members 128 are made of rubber, and their tips are bent away from each other so that the distance between the pair of squeegee members 128 becomes wider toward the lower end, and the sides of these squeegee members 128 have through-holes. It is closed by side plates 94 that close the openings at both ends of 92,
A discharge port 129 is formed that is long in the width direction of the screen 26 and opens downward.

Further, the casing 90 is connected to a piston rod 136 of an air cylinder 134 via a bracket 130 fixed to the upper surface of the casing 90 and a link 132 connected to the bracket 130 so as to be rotatable around a horizontal axis. Due to the expansion and contraction of the piston rod 136, the casing 90
is rotated around the horizontal axis and moved to positions rotated by the same angle clockwise and counterclockwise from the position shown by the solid line in FIG. 3, thereby changing the contact angle of the squeegee 76 with the screen 26. It looks like this. This rotation angle is determined by the contact of two adjustment bolts 138 vertically screwed onto the bracket 130 with the support arm 82, and in this embodiment is tilted by 2 degrees.

Next, the operation will be explained. When printing the creamy solder 70 on the printed circuit board 16, the screen 26 is first set on the screen support stand 24. Then, the printed circuit board 16 is transported, positioned and supported by the printed circuit board positioning and supporting device, and the screen 26 is
After being brought into contact with the lower surface of the printed circuit board 16, the squeegee 76 reciprocates over the screen 26 to print creamy solder 70 on the printed circuit board 16. At this time, the rotating shaft 112 of the stirrer 74 is rotated, and nitrogen gas is supplied to the syringe 72. The rotational speed of the rotating shaft 112 is set at a height at which the creamy solder 70 is kneaded to a viscosity suitable for printing, and the creamy solder 70 is printed by constantly rotating the rotating shaft 112 during printing. During this time, the mixture is kneaded and automatically made to have a viscosity suitable for printing, and is discharged from the discharge port 129 by its own weight and the extrusion force of nitrogen gas to be printed on the printed circuit board 16. A pair of squeegee members 128
Since the distance between the lower edges of the squeegee member 128 is made wider as it goes downward, the creamy solder 70 is
It is smoothly discharged along the sloping inner surface of the

Furthermore, each time the direction of movement of the casing 90 changes, the upper end of the casing 90 is tilted toward the upstream side with respect to the direction of movement. When the squeegee member 128 has a shape inclined with respect to the printed circuit board 16, a large amount of creamy solder 70 gathers on the upstream squeegee member 128 side in the moving direction of the pair of squeegee members 128, and the creamy solder 70 collects on the squeegee member 128 side on the downstream side in the moving direction. There is less creamy solder 70 on the casing 90 side, which causes abnormal noise when moving, and stick-slip may occur in the downstream squeegee member 128. However, if the casing 90 is tilted in this way, the downstream squeegee member 128 The contact of the member 128 with the printed circuit board 16 is maintained, and the creamy solder 70 is prevented from protruding, while the contact surface pressure is reduced, and the occurrence of abnormal noise and stick-slip is reduced.

When printing on one printed circuit board 16 is completed, the printed circuit board 16 is separated from the screen 26 and then ejected, and the next printed circuit board 16 is conveyed and creamy solder is printed on it. And printed circuit board 1
When the type of screen 6 changes and the screen 26 is replaced, the squeegee 76 is moved away from the screen 26. At this time, the squeegee 76 is moved horizontally by a moving device such as a servo motor 66 and raised and lowered. It is raised by cylinder 58. Therefore, the discharge port 12
The creamy solder 70 in contact with the screen 26 in the squeegee member 1 on the upstream side in the moving direction
The casing 90 is wiped from the screen 26 by the casing 28 due to its viscosity.
The squeegee 76 is moved away from the screen 26 without leaving any creamy solder 70 on the screen 26. In this embodiment, the moving speed of the squeegee 76 when separating the squeegee 76 from the screen 26 is the same as that during printing, and is 20 mm/s to 20 mm/s.
It is 70mm/s. Also, the rising speed is squeegee 76
moves in the horizontal direction by a distance approximately three times the width of the opening 126 of the casing 90 (approximately 36 mm in this embodiment), it rises by 2 to 3 mm. Note that screen printing is performed, and the creamy solder 70 inside the syringe 72 is
decreases, the float 108 descends, and the magnetic switch 109
If detected, the syringe 72 is automatically replaced. At this time, an alarm may be issued.

As described above, according to the screen printing machine of this embodiment, the creamy solder 70 is housed in the syringe 72 and is shielded from the atmosphere, which prevents the increase in viscosity due to evaporation of solvents such as alcohol and the oxidation of the solder. will not occur,
The coating can be applied to the printed circuit board 16 under the same conditions from the start to the end of printing. Also, cream solder 7
In order to use 0 for printing, it is necessary to knead solder grains and flux to obtain a viscosity suitable for printing. Conventionally, it was necessary for a skilled worker to properly knead the solder particles and place it on the screen. On the other hand, in this embodiment, the creamy solder 70 is stirred by the stirring roller 124 and automatically has a viscosity suitable for printing, so even non-experts can easily perform screen printing. . moreover,
Previously, it was necessary for a worker to knead creamy solder and place it on the screen each time the screen was replaced, but since the creamy solder is kneaded automatically, the worker does not have to do the kneading work when replacing the screen. This eliminates the need for screen replacement, making it easy to automate screen replacement. Furthermore, the syringe 72
Since the printer is automatically replaced when the remaining amount becomes low, the effect of making it easy to fully automate screen printing is obtained in this respect as well. Furthermore, since the squeegee 76 can be separated from the screen 26 without leaving any creamy solder 70, it becomes unnecessary for the operator to collect the creamy solder 70 on the screen 26 when replacing the screen 26, and 26 can be replaced automatically. Further, since no creamy solder 70 remains on the screen 26, there is no waste of the creamy solder 70, and the screen 26 can be easily cleaned.

[0021] In the above embodiment, the case where the cream solder 70 is printed with the screen 26 in close contact with the printed circuit board 16 was explained as an example, but the screen was separated from the printed circuit board by a small distance. Printing may also be performed in the current state. In this way, the screen is separated from the printed circuit board except for the part that is pressed against the printed circuit board by the squeegee, and the part of the screen that is pressed against the printing board for printing will be moved as the squeegee moves after printing. There is an advantage in that the solder can be gradually separated from the printed circuit board and the printed cream solder can be separated from the printed circuit board without losing its shape. However, in this case, the creamy solder enters the back side of the screen through the small hole provided in the part of the screen that is pressed against the printed circuit board by the squeegee and away from the printed circuit board, and Creamy solder may adhere to areas other than the printing position, or creamy solder may adhere to the back side of the screen, staining the screen. In particular, when the creamy solder is sealed in a container and discharged under pressure as in the above embodiment, the creamy solder tends to enter the back side of the screen. Therefore, when printing creamy solder with the screen separated from the printed circuit board, as shown in FIG.
Press rollers 152 are respectively attached to the upstream side and the downstream side with respect to the moving direction of the squeegee 76 so as to be rotatable around a horizontal axis extending in the width direction of the screen 154. In this way, the front and rear parts of the screen 154, including the part where the creamy solder is printed by the squeegee 76, are brought into close contact with the printed circuit board 156, and the creamy solder does not get into the back side of the screen 154. .

Further, in the above embodiment, nitrogen gas was supplied to the syringe to apply pressure to the creamy solder and push it out, but this is not essential and may be omitted. The syringe is installed vertically, and moves downward due to its own weight and is discharged even without supplying an inert gas such as nitrogen gas.

[0023] Furthermore, in the above embodiment, the casing 90
The creamy solder 70 inside is stirred by the stirring roller 124, but this may be omitted if the printing material does not require stirring to keep the viscosity at an appropriate level.

Further, in the above embodiment, the squeegee member 128 is inclined with respect to the screen 26, but it may also be in contact with the screen 26 at right angles, and the squeegee member 128 is not limited to a plate-shaped rubber material. It may be made of other materials such as resin, and the cross-sectional shape of the portion that contacts the screen may be triangular or diamond-shaped.

Furthermore, a stirring motor for rotating the stirring roller may be provided on the squeegee unit side, and the entire squeegee unit may be detachably attached to a slide that moves horizontally along the screen. In this way, multiple types of squeegee units having squeegee members with widths corresponding to the screen used can be prepared, the squeegee units can be automatically replaced when replacing the screen, and the squeegee members can be used according to the size of the screen. By doing so, it is possible to obtain effects such as eliminating wastage of creamy solder.

Furthermore, the moving speed and rising speed of the squeegee 76 when separating the squeegee 76 from the screen 26 are as follows:
It may be set appropriately depending on the type of printing agent, etc.

In addition, the present invention can be implemented with various modifications and improvements based on the knowledge of those skilled in the art without departing from the scope of the claims.

[Brief explanation of the drawing]

FIG. 1 is a side cross-sectional view showing a squeegee unit of a squeegee device provided in a screen printing machine that is an embodiment of the first invention and is preferably used in carrying out the second invention.

FIG. 2 is a front view (partially in section) showing the squeegee unit and its surroundings.

FIG. 3 is a side view showing the squeegee unit and its surroundings.

FIG. 4 is a front view showing a screen positioning support device and a squeegee device of the screen printing machine.

FIG. 5 is a diagram showing a case where printing is performed with the screen separated from the printed circuit board.

[Explanation of symbols]

10 Screen positioning support device 12 Squeegee device 16 Printed circuit board 18 Board support stand 24 Screen support stand 26 Screen 52 Slide 56 Squeegee unit 58 Lifting cylinder 62 Nut 64 Feed screw 66 Servo motor 70 Creamy solder 72 Syringe 74 Stirrer 76 Squeegee 112 Rotation axis 114 Pulley 116 Belt 118 Pulley 120 Stirring motor 124 Stirring roller 129 Discharge port 152 Holding roller 154 Screen 156 Printed circuit board

Claims (2)

[Claims] 1. A printing plate support stand, a screen support stand, and a squeegee device, the squeegee of the squeegee device moves over the screen supported by the screen support stand, so that the printing plate support stand can be moved. In a screen printing machine that prints a printing agent such as an adhesive or a creamy solder on a supported printing plate, the squeegee device is housed in a closed container in which the printing agent is shielded from the atmosphere, and the container is closed. 1. A screen printing machine comprising: a squeegee having a printing agent discharge port connected to a container and in close contact with the screen; and a moving device for moving the squeegee over the screen. 2. The screen printing machine according to claim 1, wherein the squeegee is moved on the screen to print the printing agent on the printing plate, and the squeegee is moved in a direction parallel to the screen and a direction perpendicular to the screen. A screen printing method characterized by separating the screen from the screen by moving the screen.