JPH05200974A - Screen printing method - Google Patents

Abstract

PURPOSE:To make printing in specified pattern shapes with paste-like substances executable in highly accurate manner in a screen printing in which paste-like solder for reflow soldering and gold, silver or copper paste for thick film are employed for applying to desired locations on a circuit substrate, and to reduce frequency of cleaning to be made on a metal screen. CONSTITUTION:The reverse face of a metal screen 6 on a side to which a squeegee 10 proceeds is pushed down with a pushing member 20, and thereby the reverse face of the metal screen 6 on the side to which the squeegee 10 proceeds is brought into close contact with the surface of a circuit substrate 1, and mask apertures 7 are filled with a paste-like substance 3 as the squeegee 10 proceeds, and thereby patterning is made with the paste-like substance over the surface of the circuit substrate 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screen printing method in which a paste solder for reflow soldering, a thick film gold, silver, copper paste or the like is applied and formed on a desired portion of a circuit board.

As electronic devices have become smaller, faster, and more multifunctional, circuit components such as semiconductor components and other capacitors have been densely reflow-soldered on a circuit board for surface mounting. There is.

To surface-mount the above-mentioned circuit component on a circuit board, paste-like solder is screen-printed on the surface of each pad arrayed on the surface of the circuit board 1, and then leads or electrodes of the circuit component are padded. Then, the paste-like solder is heated for reflow soldering.

[0004]

2. Description of the Related Art FIG. 5 is a view of a conventional example, (A) is a sectional view,
(B) is a detailed cross-sectional view of a main part. In FIG. 5, reference numeral 1 is a circuit board on which circuit components are surface-mounted, and pads 2 are arranged on the surface.

In the state of being aligned with the circuit board 1, a mask hole 7 having a shape substantially equal to the shape of the pad 2 is formed at a position facing the pad 2, 150 μm to 200 μm.
It is a metal screen made of, for example, stainless steel with a plate thickness of μm.

Such a metal screen 6 is aligned and stretched on the circuit board 1, and the paste solder 3-1 is applied to the entire surface of the metal screen 6, and then the squeegee 8 is attached to the surface of the metal screen 6. Then, the mask hole 7 is filled with the paste-like solder 3-1 and then the metal screen 6 is removed, and the paste-like solder 3-1 having a thickness almost equal to the plate thickness of the metal screen 6 is placed on the pad 2. It is formed by coating.

[0007]

By the way, as shown in FIG. 5 (A), the gap C between the metal screen and the circuit board is 1 mm to 2 mm in order to improve the paste removal property of the paste-like solder. As described above, the metal screen is stretched on the circuit board and pressed by the squeegee, so that the back surface of the metal screen is screen-printed in close contact with the surface of the circuit board only at a portion directly below the squeegee.

Therefore, as shown in FIG. 5B, the metal screen portions on both sides of the squeegee are raised above the circuit board, and the paste-like solder 3 is formed below the edge of the mask hole in the traveling direction of the metal screen. -1 wraps around and the paste-like solder 3-1 is applied and applied at the position where the pad comes off.

For this reason, when pads are formed with a fine pitch, there is a problem that a bridge is generated between adjacent pads. In addition, since the paste-like solder wraps around and adheres to the back surface of the metal screen, the metal screen must be cleaned if the screen printing is performed more than ten times, and the workability of the screen printing is poor.

The present invention has been made in view of the above-mentioned points, and it is possible to screen-print a paste-like substance in a predetermined pattern shape, the printing quality is highly accurate, and the number of times of cleaning the metal screen is reduced. It is an object of the present invention to provide a screen printing method that can be performed and has good working efficiency.

[0011]

In order to achieve the above object, the present invention, as shown in FIG. 1, presses the surface of the metal screen 6 in the traveling direction of the squeegee 10 with a pressing member 20, The back surface of the metal screen 6 on the advancing direction side of the squeegee 10 is brought into close contact with the surface of the circuit board 1, and the squeegee 10 is moved to fill the mask hole 7 with the paste-like substance 3 and the surface of the circuit board 1 is covered. A pattern of the pasty substance 3 is formed.

Specifically, as illustrated in FIG. 2, a pair of cylinders having pressing plates 21-1, 22-1, each of which has a length substantially equal to the width of the metal screen, is attached to the lower portion of each piston rod. 22-1, 22-2 will be installed.

The pair of cylinders 22-1, 22-2 are attached to the main body of the screen printing apparatus so as to face each other above and below the metal screen 6. Then, the cylinder on the moving direction side of the squeegee 10 is driven to press the front surface of the metal screen 6 with the pressing plate, and the back surface of the metal screen 6 on the moving direction side of the squeegee 10 is brought into close contact with the surface of the circuit board 1.
Fill the mask hole 7 with the squeegee 10 and paste-like substance 3,
A pattern of the paste-like substance 3 is formed on the surface of the circuit board 1.

Alternatively, as illustrated in FIG. 3, a pair of cylinders 26-1 and 25-2, each of which has rollers 25-1 and 25-2 each having a length substantially equal to the width of the metal screen, is attached to the lower portion of each piston rod. 26-2 is provided, and the cylinders 26-1 and 26-2 are attached to the front and rear of the squeegee 10 so as to face each other.

Then, the cylinder on the traveling side of the squeegee 10 is driven to press the metal screen 6 with the roller,
The back surface of the metal screen 6 on the advancing direction side of the squeegee 10 is brought into close contact with the surface of the circuit board 1, and the squeegee 10 is moved to fill the mask holes 7 with the paste-like substance 3 and paste on the surface of the circuit board 1. A pattern of the particulate matter 3 is formed.

Alternatively, as illustrated in FIG. 4, the front and rear side walls of the dispenser 40 that discharges the paste-like substance 3 are composed of a pair of squeegees 30-1 and 30-2. By pressing the front surface of the metal screen 6 with the pair of squeegees 30-1 and 30-2, the back surface of the metal screen 6 between the squeegees is brought into close contact with the front surface of the circuit board 1, and the dispenser 40 is attached to the circuit board 1. It is assumed that the paste material 3 is moved in parallel and the paste holes 3 are filled in the mask holes 7 with a squeegee on the side opposite to the traveling direction to form a pattern of the paste materials 3 on the surface of the circuit board 1.

[0017]

According to the method of the present invention, the back surface of the metal screen stretched over the circuit board with a predetermined gap is in close contact with the front surface of the circuit board only on the advancing direction side of the squeegee.

Therefore, it is possible to prevent the paste-like substance with which the mask hole is filled from flowing around to the back surface side of the metal screen. That is, since the paste-like substance is not printed outside the region corresponding to the mask hole on the surface of the circuit board, the print quality is improved.

Further, since the paste-like substance does not adhere to the back surface of the metal screen, the number of times of cleaning the metal screen can be reduced. That is, the work efficiency of screen printing is improved.

On the other hand, the rear metal screen on which the squeegee has moved floats above the circuit board. Therefore, the plate-removing property of the pasty substance is almost the same as the conventional one and is good.

[0021]

The present invention will be described in detail with reference to the drawings. The same reference numerals denote the same objects throughout the drawings.

FIG. 1 is a diagram showing the principle of the present invention, FIG. 2 is a diagram of an embodiment of the present invention, FIG. 3 is a diagram of another embodiment of the present invention, and FIG. 4 is a further embodiment of the present invention. FIG. 2 to 4, 3 is a paste-like substance such as paste-like solder.

Reference numeral 6 denotes a metal screen made of, for example, stainless steel having a plate thickness of 150 μm to 200 μm, which has a shape substantially equal to the shape of the pad 2 at a position facing the pad 2 when aligned with the circuit board 1. The mask hole 7 is drilled.

In FIG. 2, 22-1 and 22-2 are a pair of pressing plates 21-1 and 22-1 each having a length substantially equal to the width of the metal screen 6 attached to the lower part of each piston rod. For example, a cylinder driven by air pressure.

The one cylinder 22-1 is a metal screen 6
It is attached to the main body of the screen printing apparatus with the pressing plate 21-1 facing downward so as to be located above the front side edge (right side in the figure) of the.

The other cylinder 22-2 is attached to the main body of the screen printing apparatus with the pressing plate 21-2 on the lower side so that it is located above the rear edge (left side in the figure) of the metal screen 6. ing.

The metal screen 6 is aligned with the circuit board 1, and the metal screen 6 is stretched on the circuit board 1 so that the gap between the front surface of the metal screen 6 and the back surface of the metal screen 6 is 1 mm to 2 mm. To do.

After the paste-like substance 3 is applied to the entire surface of the metal screen 6, the cylinder 22-1 on the advancing direction side of the squeegee 10 is driven to press the surface of the metal screen 6 with the pressing plate 21-1. By pressing, the back surface of the metal screen 6 directly below the pressing plate 21-1 is brought into close contact with the front surface of the circuit board 1.

Next, the squeegee 10 is pushed down to bring the portion of the metal screen 6 immediately below the squeegee 10 into close contact with the surface of the circuit board 1. As a result, only the metal screen portion between the pressing plate 21-1 on the advancing side of the squeegee 10 and the portion directly below the squeegee 10 is in close contact with the circuit board 1, and the other portions are lifted from the circuit board 1.

In this state, the squeegee is moved toward the cylinder 22-1.
The mask material 7 is filled with the paste-like substance 3 by traveling in the forward path through 10. Then, when the squeegee 10 reaches one side edge of the metal screen 6, the cylinder that has descended
22-1 is driven to pull up the pressing plate 21-1, and the cylinder 22-2 on the opposite side is driven to press the surface of the metal screen 6 with the pressing plate 21-2. The back surface of the metal screen 6 immediately below is brought into close contact with the front surface of the circuit board 1, and only the metal screen portion between the pressing plate 21-2 on the return path side and the squeegee 10 is brought into close contact with the circuit board 1.

Then, the mask-like hole 7 is filled with the paste-like substance 3 by traveling in the returning direction in the direction of the cylinder 22-2, that is, the squeegee 10. After repeating the above several times, the metal screen 6 is removed, and the paste-like substance 3 is applied and formed on the pad 2 on the surface of the pad 2 with a thickness substantially equal to the plate thickness of the metal screen 6.

According to the present invention, the metal screen 6 is in close contact with the surface of the circuit board 1 only on the advancing direction side of the squeegee 10. Therefore, the paste-like substance 3 with which the mask hole 7 is filled is prevented from flowing around to the back surface side of the metal screen 6.

That is, the print quality is improved. It should be noted that a paste-like substance such as silver paste may be screen-printed on the surface of the circuit board to form a thick film pattern by the same means as described above to obtain a desired highly accurate pattern. is there.

In FIG. 3, reference numerals 26-1 and 26-2 denote rollers (rubber rollers, for example) 25-1 and 25- each having a length substantially equal to the width of the metal screen 6 at the bottom of each piston rod.
2 is a pair of cylinders in which 2 is rotatably mounted and driven by air pressure, for example.

One cylinder 26-1 is fixed to the front side (right side in the figure) of the squeegee 10 with the roller 25-1 being the lower side, and the other cylinder 26-2 is rear side of the squeegee 10 (left side in the figure). The roller 25-2 is fixed to the lower side.

The metal screen 6 is aligned with the circuit board 1, and the metal screen 6 is stretched on the circuit board 1 so that the gap between the front surface of the metal screen 6 and the back surface of the metal screen 6 is 1 mm to 2 mm. To do.

Then, the cylinder 26-1 is driven to drive the roller.
Press the surface of the metal screen 6 with 25-1 and press the squeegee.
While traveling 10 onward, rolling the roller 25-1 while squeegeeing
The cylinder 26-1 is moved together with 10, and the metal screen portion in the traveling direction is brought into close contact with the surface of the circuit board 1 for screen printing.

On the outward path, the roller 25-1 is pulled up,
The other cylinder 26-2 is driven so that the roller 25-2 presses the surface of the metal screen 6 for screen printing.

In FIG. 4, reference numeral 40 denotes a dispenser having a rectangular frame shape in plan view, the length of which is substantially equal to the width of the metal screen 6. The front and rear side walls of the dispenser 40 are composed of a pair of squeegees 30-1 and 30-2.

The dispenser 40 is one in which the pasty substance 3 is continuously applied to the surface of the circuit board 1 by introducing the pasty substance 3 into the frame and blowing compressed air from the upper suction port.

As described above, when the front surface of the metal screen 6 is pressed by the pair of squeegees 30-1 and 30-2 mounted so as to face the dispenser 40, the back surface of the metal screen 6 between the squeegees is the front surface of the circuit board 1. Close to.

When the dispenser 40 is driven in this state to reciprocate on the circuit board, the paste-like substance 3 is pushed into the mask hole 7 by the squeegee on the side opposite to the traveling direction. Therefore, the paste-like substance 3 is applied and formed on the surface of the circuit board 1 in the same pattern as the mask holes 7.

[0043]

As described above, according to the present invention, the metal screen portion in the traveling direction of the squeegee is brought into close contact with the surface of the circuit board, and the metal screen portion in the opposite direction to the traveling direction is floated from the surface of the circuit board. By performing the screen printing, the paste-like substance filled in the mask holes is prevented from wrapping around on the back surface side of the metal screen, and the printing quality is improved.

Moreover, since the paste-like substance does not adhere to the back surface of the metal screen, the number of times the metal screen is cleaned can be reduced, and the work efficiency of screen printing is improved. In addition, the plate release property of the paste-like substance is
Almost as good as the conventional one.

Furthermore, by using squeegees on both the front and rear walls of the dispenser, it is possible to easily replenish the paste-like substance.

[Brief description of drawings]

FIG. 1 is a diagram showing the principle of the present invention.

FIG. 2 is a diagram of an embodiment of the present invention.

FIG. 3 is a diagram of another embodiment of the present invention.

FIG. 4 is a diagram of yet another embodiment of the present invention.

FIG. 5 is a diagram of a conventional example, (A) is a sectional view, and (B) is a detailed sectional view of a main part.

[Explanation of symbols] 1 circuit board 2 pad 3 paste material 3-1 paste solder 6 metal screen 7 mask hole 8, 10 squeegee 20 pressing member 21-1,21-2 pressing plate 22-1,22-2, 26-1,26-2 Cylinder 25-1,25-2 Roller

Claims (4)

[Claims] 1. The back surface of the metal screen (6) on the advancing direction side of the squeegee (10) by pressing the surface of the metal screen (6) in the advancing direction of the squeegee (10) with a pressing member (20). Closely contact the surface of the circuit board (1), move the squeegee (10) to fill the mask holes (7) with the paste-like substance (3), and paste the paste-like substance onto the surface of the circuit board (1). A screen printing method, which comprises forming a pattern of a substance (3). 2. A pressure plate (21-) having a length substantially equal to the width of the metal screen (6) is provided at the bottom of each piston rod.
1,22-1) attached to a pair of cylinders (22-1,22-2)
The metal screen (6) is attached to the main body of the device so as to be opposed to the upper and lower sides, and the cylinder on the advancing direction side of the squeegee (10) is driven to press the surface of the metal screen (6) with the pressing plate. The back surface of the metal screen (6) on the advancing direction side of the squeegee (10) is brought into close contact with the front surface of the circuit board (1), and the squeegee (10) is moved and moved to paste into the mask hole (7). A screen printing method comprising filling a substance (3) and forming a pattern of the pasty substance (3) on the surface of the circuit board (1). 3. A roller (25) having a length approximately equal to the width of the metal screen (6) is provided at the bottom of each piston rod.
-1,25-2) attached to a pair of cylinders (26-1,26-2)
Of the squeegee (10) are installed so as to face each other, and the cylinder on the advancing direction side of the squeegee (10) is driven to press the surface of the metal screen (6) with the roller, The back surface of the metal screen (6) on the advancing direction side is brought into close contact with the surface of the circuit board (1), and the squeegee (10) is moved to fill the mask hole (7) with the paste-like substance (3). A screen printing method comprising forming a pattern of the paste-like substance (3) on the surface of the circuit board (1). 4. A pair of squeegees (30-1, 30-2) formed on the front and rear side walls of a dispenser (40) for discharging the pasty substance (3).
The metal screen is composed of a pair of the squeegees (30-1, 30-2)
While pressing the front surface of (6) to bring the back surface of the metal screen (6) between the squeegees into close contact with the front surface of the circuit board (1), the dispenser (40) is moved and moved in the direction opposite to the traveling direction. The pasty substance (3) is filled on the surface of the circuit board (1) by filling the mask hole (7) with the pasty substance (3) with the squeegee on the side.
A screen printing method, which comprises forming a pattern.