JPH07156363A - Printer, printing method and printing mask - Google Patents

Abstract

PURPOSE:To more preferably print solder paste by providing a holding table and providing a suction force generator for bringing a printing mask into close contact with a printing board by suction, and a squeegee mechanism for pressing the paste into a through hole of the mask by moving. CONSTITUTION:A plurality of suction holes 11 opened at a holding surface 10a are provided in a holding table 10. After the holes 11 are coupled in the table 10, it is removed from a side of the table 10, and connected to a vacuum unit. Accordingly, a printing board 3 placed on the surface 10a of the table 10 is held by sucking on the surface 10 of the table 10 when the vacuum unit 12 is operated. First printing mask 16 is precisely aligned with the board 3 on the table 10 to be superposed. Then, solder paste 4 is supplied to the mask 16, and the paste 4 supplied to the mask 16 is moved in a direction of an arrow. Thus, the paste 4 is sequentially pressed into the holes 16a provided at the mask 16.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing apparatus, a printing method and a printing mask for printing and supplying a solder paste on a wiring of a printed circuit board.

[0002]

2. Description of the Related Art For example, on one printed circuit board, QF
There are cases where it is necessary to surface mount a large number of various electronic components such as P and various chip components at once. In such cases,
A reflow soldering method capable of collectively soldering a large number of various electronic components is widely used.

In this reflow soldering, a solder paste prepared by kneading solder powder with flux etc. is previously supplied onto each electrode pad of the wiring formed on the printed board.

Then, each electronic component to be mounted on this printed circuit board is mounted on this substrate in a state where the electrodes of this electronic component are in contact with the solder paste. When all the electronic components have been placed on the printed circuit board, the printed circuit board is inserted into the reflow oven together with the electronic components. As a result, the solder paste is re-melted, and the electronic components mounted on the board are collectively soldered (surface mounted) to the printed board.

In order to favorably perform such reflow soldering, it is important to accurately supply the solder paste onto each electrode pad of the wiring pattern. There is a screen printing method as a method for accurately supplying the solder paste onto the printed circuit board. For this screen printing, for example, a print mask indicated by 1 in FIG. 6 is used. As shown in FIG. 5, the print mask 1 is a screen-shaped thin plate provided with openings 1a corresponding to the respective wiring patterns of the printed circuit board.

At the time of printing, as shown in FIGS. 7A and 7B, first, the print mask 1 is overlaid on the upper surface of the printed circuit board 3. Then, the squeegee indicated by 2 in FIG. 2B presses the printing mask 1 downward to press it onto the printed circuit board 3, and the squeegee 2 presses the mask 1
The solder paste 4 supplied above is moved in the direction indicated by the arrow (a) in the figure. As a result, the solder paste 4 is pushed into the openings 1a of the print mask 1.

Next, when the print mask 1 is separated from the printed circuit board 3, the solder paste 4 pushed into the opening 1a of the print mask has an electrode pad (not shown) of the printed circuit board 3 shown in FIG. ) Is transcribed on. As a result, the solder paste on the printed circuit board 3
The strike 4 is printed and supplied in a predetermined pattern.

[0008]

By the way, in the above-mentioned screen printing, the printing conditions and the actual printing work are also important. First, as shown in FIG. 6, the print mask 1 has a size based on a certain standard (for example, 1 m × 1).
m) is stretched and held in the frame 6 (screen frame 6) with a constant tension by a stretchable mesh-shaped stretching member 7.

The reason why the print mask 1 is not directly attached to the screen frame 6 but is attached via the tension member 7 is that the print mask 1 expands or contracts due to temperature change. This is to absorb the deformation of the print mask 1 and prevent the print mask 1 from bending.

However, during printing, the squeegee 2 moves on the print mask 1 with a predetermined printing pressure,
The frictional force generated between the print mask 1 and the squeegee 2 may cause the print mask 1 to move against the tensioning force of the tensioning member 7.

In such a case, printing is completed and the
When the sheet 2 is separated from the print mask 1, the print mask 1 is returned to the initial position by the tension force of the tension member 7.

At this time, the print mask 1 in which the solder paste 4 is pressed into the opening 1a and the printed circuit board 3 are provided.
Therefore, the solder paste 4 may wrap around between the print mask 1 and the printed circuit board 3, and "bleeding" of the solder paste 4 may occur.

When the print mask 1 is separated from the printed circuit board 3 in this state, the printed solder paste 4 loses its shape and "drip" occurs. When "Who" of Solder Paste 4 occurs, Solder Paste 4
When is re-melted, the solder pastes 4 supplied to the other adjacent electrode pads may come into contact with each other, causing a defect such as a solder bridge.

Secondly, even if the print mask 1 and the printed circuit board 3 are not displaced as described above, the amount of the solder paste 4 to be printed is large and the printing pressure of the squeegee 2 is large. Then, as shown in FIG. 8, the mask 1
The solder paste 4 may wrap around a gap (shown by (B) in the figure) between the lower surface of the solder paste 4 and the upper surface of the printed circuit board 3, and the solder paste 4 may also bleed.

Further, the lower surface of the print mask 1 is soiled due to the occurrence of such bleeding. When the lower surface of the print mask 1 is soiled in this way, the bleeding occurs more greatly. Therefore, it is necessary to periodically remove the print mask 1 from the apparatus and clean it.

However, since it is necessary to frequently remove stains on the lower surface of the print mask 1, cleaning must be performed every printing in an extreme case, and the production efficiency is correspondingly increased. There is a problem of decrease.

Thirdly, when various types of electronic components (chip components, QFPs, etc.) are mounted on the printed circuit board 3, the shape and size of the terminals (electrodes) differ depending on the type of electronic components. It is necessary to change the amount and shape of the solder paste 4 to be printed and supplied on the printed circuit board 3.

For example, the electrodes of the chip component are relatively large and the intervals between the electrodes are wide, but the outer leads, which are the electrodes of the QFP, have small contact portions with the printed circuit board 3 and are provided at narrow intervals. Many.

Conventionally, in the case of performing such printing, as shown in FIG. 6, printing is performed by providing openings 1a of various sizes in a print mask having a thickness of 150 to 300 μm.
However, if the opening 1a is too small, the printing mask 1 having the above-described thickness causes the solder paste 4 to be out of print and causes clogging, so that the printing mask 1 is partially thinned for printing. Techniques such as adjusting the amount of solder paste 4 are also incorporated.

However, when the thickness of the print mask 1 is partially thinned, the step formed at the boundary between the thin portion and the thick portion rubs against the squeegee 2, and thus the squeegee 2 is cracked. May occur and its life may be shortened.

On the other hand, when the thickness of the print mask 1 is gently changed, a certain distance is required to change the thickness.
It may not be applicable due to lack of space.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a printing apparatus, a printing method, and a printing mask which can print solder paste more favorably. is there.

[0023]

A first means is a printing apparatus for printing a solder paste on a printed circuit board with a predetermined pattern, a holding table for holding the printed circuit board, and the solder paste. And a through-hole having a shape corresponding to a predetermined pattern for printing, and a thin plate-shaped printing mask to be overlaid on the printed circuit board held on the holding table, and the holding table. , A suction force generation device for sucking the print mask to bring the print mask into close contact with the printed circuit board, and moving the print mask on the print mask to place a solder paste in the through hole provided in the print mask. And a squeegee mechanism for pushing in.

A second means is characterized in that, in the printing apparatus of the first means, the suction force generating device is a magnetic force generating device which sucks the print mask by a magnetic force.

A third means is a printing apparatus for printing a solder paste on a printed circuit board with a predetermined pattern, and a holding table for holding the printed circuit board and a predetermined pattern for printing the solder paste. A print mask in the form of a thin plate which has a through hole having a shape corresponding to that of the printed circuit board and is stacked on the printed circuit board held on the holding table, and is provided on the print mask by moving the print mask. The squeegee mechanism for pushing the solder paste into the through hole and the holding table are provided. When the squeegee moves, the print mask prints the print as the squeegee moves. It is characterized in that it is provided with a restricting means for restricting displacement with respect to the substrate.

A fourth means is the printing apparatus according to the third means, wherein the regulating means has a surface having a coefficient of friction larger than that of the surface of the printed circuit board, and the holding table and the print mask are provided during printing. It is characterized by being a friction member interposed between.

The fifth means has a plurality of through holes corresponding to the wirings provided on the printed board, and the solder paste is pushed into the through holes by being superposed on the printed board and the solder paste is pressed. In a print mask for printing a strike on the wiring provided on the printed circuit board, the through hole is not provided at a portion of the printed circuit board corresponding to the wiring on which the solder paste is already printed, and the printed circuit board is in contact with the printed circuit board. It is characterized in that a concave portion that opens to the surface side is provided.

A sixth means is a printing method in which a solder mask is screen-printed on a printed circuit board with a predetermined pattern using a printing mask, and a fine pattern is printed using the first printing mask. -The first step of performing screen printing of the ink and a second printing mask thicker than the first printing mask, except for the portion where the solder paste is printed by the first printing mask And a second step of printing the solder paste on the part (1).

[0029]

According to the first and second means, the print mask and the printed circuit board can be brought into close contact with each other. According to the third and fourth means, it is possible to prevent the print mask and the printed circuit board from being displaced when the squeegee is moved. According to the fifth and sixth means, even when the amount and shape of the solder paste to be printed vary,
They can be printed well.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS. The same components as those of the conventional example are designated by the same reference numerals and the description thereof will be omitted. First, a first embodiment of the present invention will be described.

In FIG. 1 (a), reference numeral 10 designates the upper surface of the holding surface 10a.
The holding table holds the printed circuit board 3 on the holding surface 10a. As shown in FIG. 2, this holding table
Inside the bull 10, a plurality of suction holes 11 that are open to the holding surface 10a are provided. And these suction holes 1
After being connected in the holding table 10, 1 is taken out from the side surface of the holding table 10 and connected to a vacuum device shown by 12 in the drawing.

Therefore, the printed circuit board 3 placed on the holding surface 10a of the holding table 10 is sucked and held on the holding surface 10a of the holding table 10 by the operation of the vacuum device 12. It has become so.

In addition, inside the holding table 10,
Electromagnetic coil device 14 (suction force generator, magnetic force generator)
Is buried. The electromagnetic coil device 14 is connected to a power supply controller 15 provided outside the holding table 10. Then, by being supplied with electric power by the power supply control unit 15, the first and second print masks 16 and 17 stacked on the printed circuit board 3 are attracted by magnetic force, as will be described later.

Further, as shown in FIG. 1 (a), on the holding surface 10a of the holding table 10, a strip-shaped material made of a material having a high friction coefficient such as rubber is provided on the outside of the printed board 3 held. The friction member 18 (regulating means) is attached along the side of the printed circuit board 3. The friction member 18 has substantially the same thickness as the printed circuit board 3.

The holding surface 10 of such a holding table 10
When the printed circuit board 3 is suction-held on a, a first print mask 16 is overlaid on the printed circuit board 10 as shown in FIGS. 1 (a) and 2.

By the way, for printing the solder paste 4, a second print mask 17 shown in FIG. 1B is prepared in addition to the first print mask 16. That is, when the electronic components mounted on the printed circuit board 3 are various, such as a chip component or a semiconductor package (QFP) having a narrow pitch lead, the paste solder 4 to be printed is printed. A first printing mask 16 is prepared for a small amount of solder paste printing, and a second printing mask 17 is prepared for a large amount of solder paste printing.

Therefore, in the first print mask 16, for example, only the portion corresponding to each outer lead of the QFP having the outer lead provided at a narrow (fine) pitch on the printed circuit board 3. A through hole 1a for printing the solder paste 4 is provided.

The first print mask 16 is made of a magnetic material and has a thickness of about 50 to 100 .mu.m in order to improve the capability of removing a small amount of the solder paste 4.
It is formed by m. And, like the conventional example, the screen
It is stretched and held in the frame 6 via a stretchable stretchable member 7.

As described above, the first print mask 16 is precisely aligned with the printed circuit board 3 held on the holding table 10 and is overlaid thereon. Then, the power supply controller 15 operates the electromagnetic coil device 14.

As a result, the print mask 16 is held in the holding table 1 by the magnetic force of the electromagnetic coil device 14.
The first print mask 16 and the printed circuit board 3 are attracted to each other in the direction of 0 and are in close contact with each other. At this time, the lower surface of the print mask 16 is brought into close contact with the friction member 18 (shown in FIG. 1A) provided on the holding surface 10a of the holding table 10 so as to be in contact with the friction member 18. A predetermined frictional force is generated between them.

Next, the solder paste 4 is supplied onto the first print mask 16, and the solder paste supplied onto the first print mask 16 is caused by a squeegee 2 shown in FIG. 4 in the direction indicated by the arrow in the figure.
As a result, the solder paste 4 is sequentially pushed into the through holes 16a provided in the first print mask 16.

When the pressing of the solder paste 4 is completed, the power supply controller 15 causes the electromagnetic coil device 14 to operate.
Is stopped, and the suction state of the first print mask 16 is released. Next, when the first print mask 16 and the printed circuit board 3 are separated from each other at a predetermined speed, the solder paste 4 comes out of the through hole 16a of the first print mask 16 and has a predetermined pattern. The above printed circuit board 3
Is transcribed to.

Next, printing is performed using the second print mask 17. The second print mask 17 is for printing on a portion requiring a relatively large amount of solder paste that cannot be handled by the first print mask 16. Therefore, the second print mask 17 is formed to have a thickness of about 100 to 250 μm, which is thicker than the first print mask 16, and the first print mask 16 is also formed.
The solder paste printed on the printed circuit board 3 by
A through hole 17a larger than the through hole 16a formed in the first print mask 16 is formed at a position where it does not interfere with the strike 4.

Then, as shown in FIG. 3, the first print mask 16 is provided on the lower surface side of the second print mask 17.
A concave portion 17b is formed at a position corresponding to the solder paste 4 printed on the printed circuit board 3 in order to prevent the second print mask 17 from coming into contact with the solder paste 4. The recess 17b is formed by etching, for example.

Like the first print mask 16, the second print mask 17 is also stretched and held in the screen frame 6 via a stretch member 7. The holding table 10
Moves below the second print mask 17 so that the printed circuit board 3 faces the lower surface of the second print mask 17.

Then, the screen frame 6 is lowered, and the second print mask 17 is placed on the printed circuit board 3. At this time, as in the case of the first print mask 17, the electromagnetic coil device 14 is actuated to be attracted by magnetic force in the direction of the holding table 10. As a result, the lower surface of the second print mask 17 comes into close contact with the surface of the printed circuit board 3 and also comes into contact with the friction member 18 with a predetermined friction force.

The solder paste 4 is supplied to the upper surface of the second print mask 17 as in the case of the first print mask 16, and the squeegee 2 moves to cause the printed circuit board 3 to move. The solder paste 4 is printed on top.

According to this structure, the following effects can be obtained. First, the first and second print masks 1 described above.
Since 6 and 17 are attracted by the magnetic force of the electromagnetic coil device 14 and are in close contact with the printed circuit board 3,
It is rare that the solder paste 4 wraps between the first and second print masks 16 and 17 and the printed circuit board 3 to cause bleeding.

Further, the first and second print masks 16,
The squeegee 2 is pulled by 17 in the traveling direction of the squeegee 2 as the squeegee 2 moves, but the squeegee 2 moves in that direction by the frictional force generated between the squeegee 2 and the friction member 18. Is regulated. Therefore, when the squeegee is raised, the bleeding of the solder paste printed by the mask is prevented.

This effectively prevents sagging of the printed solder paste 4 and enables good reflow soldering. Also,
Since the amount of the solder paste 4 attached to the back surfaces of the first and second print masks 16 and 17 is reduced, the number of times these cleanings are performed can be reduced, and the working efficiency is improved.

Second, in order to mount a large number of various electronic components, two types of first and second print masks 1 having different thicknesses are used.
6 and 17 were used. And a thin first print mask 16
After printing with, the thick second print mask 17 is used for printing, and the second print mask 17 has
The second print mask 17 is the first print mask 16 described above.
The recessed portion 17b is provided so as not to contact the solder paste 4'printed by.

As a result, the solder paste can be printed with an appropriate shape and quantity corresponding to each of a wide variety of electronic components. Therefore, there is an effect that good reflow soldering can be performed.

Further, since it is not necessary to provide a step on the print mask as in the conventional example, the damage of the squeegee is reduced. Next, a second embodiment will be described.

The same components as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted. 10 'in the figure
Is a holding table for holding the printed circuit board 3.

In the holding table 10 ', in addition to the suction hole 11 for sucking and holding the printed circuit board 3, a print mask suction hole 20 for sucking and holding the print mask 16 is provided. ing. This printing mask suction hole 2
0 are connected to each other in the holding table device 10 ',
It is connected to a vacuum device 21 provided outside the holding table device 10 '.

The printed circuit board 3 is provided with a plurality of through holes 3a penetrating from the back surface to the front surface of the printed circuit board 3 at a portion corresponding to the opening position of the suction hole 20.

On the other hand, on the holding table 10 ', a pin 22 for engaging with the printing mask 16 is provided outside the position where the printed board 3 is held. Then, the print mask 16 held in the screen frame 6
An insertion hole 23 into which the pin 22 is inserted is provided at the edge portion of the.

At the time of printing, the screen frame 6 is lowered and the holding tape is inserted into the insertion hole 23 of the print mask 16.
The pin 22 protruding from the bull 10 'is inserted. When the lower surface of the print mask 16 comes into contact with the surface of the printed circuit board 3, the vacuum device 21 is operated to generate a suction force in the mask holding suction hole 20, so that the suction holes provided on the printed circuit board 3 are passed through. Through the hole 3a, the printing mask 1
6 is adsorbed and held. As a result, the printing mask 16 and the printed board 1 are in close contact with each other.

When the print mask 16 and the printed circuit board 1 are brought into close contact with each other in this way, the solder paste 4 is printed by using the squeegee 2 as in the first embodiment, and at the same time the above-mentioned first embodiment is performed. The second printing is performed using the second printing mask 17.

According to this structure, the printed circuit board 3 and the print mask 16 can be brought into close contact with each other by generating a vacuum force in the mask suction hole 20, and the holding table 10 'can be provided. By locking the protruding pin 22 and the insertion hole 23 provided in the print mask 16, it is effective that the print mask 16 is displaced from the printed circuit board 3 when the squeegee 2 is moved. Can be prevented.

Therefore, as in the first embodiment,
There is an effect that the bleeding of the solder paste 4 can be prevented and good reflow soldering can be performed. It should be noted that the present invention is not limited to the above-mentioned one embodiment, and can be variously modified without changing the gist of the invention.

For example, in the above-mentioned first and second embodiments, the two first and second print masks 16 and 17 are used to print the solder paste 4 on the printed circuit board 3. The present invention is not limited to this, and three or more print masks may be used if necessary.

Further, in the above-mentioned one embodiment, the friction member 18 is used in the first embodiment and the pin 22 is used in the second embodiment as the restricting means. However, the restricting means is not limited to this, for example, a plane gear shape. A member having a surface of
Alternatively, the movement of the print mask 16 may be restricted by fixing the print mask 16 on the surface of the print mask 0 and engaging the print mask 16 with the print mask 16.

[0064]

As is apparent from the above-described structure, the present invention has the following effects. First, the holding table
A suction force generator provided in the bull sucks the print mask stacked on the printed circuit board to bring the print mask into close contact with the printed circuit board.

As a result, it is possible to effectively prevent the solder paste from sneaking in between the print mask and the printed circuit board to cause bleeding, and it is possible to perform good printing.

Secondly, when the squeegee moves, a regulation means is provided to prevent the print mask from being displaced due to the movement of the squeegee. As a result, it is possible to effectively prevent the print mask and the printed circuit board from being displaced from each other after printing is completed, so that the bleeding of the solder paste can be prevented.

Thirdly, in order to mount a large number of various electronic components, printing with the first and second printing masks having different thicknesses is used, and after printing with the thin first printing mask, the thick first printing mask is printed. The second printing mask is printed with a second printing mask, and the second printing mask is provided with a recess for preventing the second printing mask from contacting the solder paste printed by the first printing mask. did.

As a result, the solder paste can be printed with an appropriate shape and quantity corresponding to each of a wide variety of electronic components. Therefore, there is an effect that good reflow soldering can be performed.

[Brief description of drawings]

1A and 1B are perspective views showing a first embodiment of the present invention.

FIG. 2 is a vertical sectional view showing a main part of the first printing process.

FIG. 3 is a vertical sectional view showing a main part of the second printing process.

FIG. 4 is a vertical cross-sectional view showing the main parts of the second embodiment.

FIG. 5 is a perspective view of the same.

FIG. 6 is a perspective view showing a general screen printing apparatus.

7A and 7B are process diagrams of the same.

FIG. 8 is an enlarged vertical sectional view of the same.

[Explanation of symbols]

2 ... Squeegee (squeegee mechanism), 3 ... Printed circuit board, 4
... solder paste, 10 ... holding table, 14 ... electromagnetic coil device (suction force generating device, magnetic force generating device), 16 ... first printing mask (printing mask), 16a ... through hole, 17
... second print mask, 17a ... through hole, 17b ... recessed portion, 18 ... friction member (regulating means), 22 ... pin (regulating means).

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical location H05K 3/34 505 D 7128-4E (72) Inventor Mitsuyoshi Tanimoto Shinisogo-cho, Isogo-ku, Yokohama-shi, Kanagawa No. 33 Incorporated Toshiba Production Engineering Laboratory (72) Inventor Noriyuki Oba No. 33 Shinisogo-cho, Isogo-ku, Yokohama, Kanagawa Prefecture

Claims (6)

[Claims] 1. A printing apparatus for printing a solder paste on a printed circuit board with a predetermined pattern, which supports a holding table for holding the printed circuit board and a predetermined pattern for printing the solder paste. A thin plate-shaped printing mask that has a through-hole having a shape that overlaps the printed circuit board that is held on the holding table; and a suction mask that is provided on the holding table and sucks the printing mask. A suction force generator for bringing the print mask into close contact with the printed circuit board, and a mechanism for moving the print mask over the print mask to push the solder paste into the through holes provided in the print mask.
And a printing mechanism. 2. The printing device according to claim 1, wherein the suction force generation device is a magnetic force generation device that attracts the print mask by a magnetic force. 3. A printing apparatus for printing a solder paste on a printed circuit board with a predetermined pattern, which corresponds to a holding table for holding the printed circuit board and a predetermined pattern for printing the solder paste. And a through-hole provided in the print mask by moving the print mask in the form of a thin plate, which has a through-hole having a shape to be overlapped with the printed circuit board held on the holding table. Skies to push solder paste into
And a holding mechanism that is provided on the holding table and that prevents the print mask from shifting with respect to the printed circuit board when the squeegee moves when the squeegee moves. A printing apparatus comprising: 4. The printing apparatus according to claim 3, wherein the regulating means has a surface having a coefficient of friction larger than that of the surface of the printed circuit board, and is interposed between the holding table and the printing mask during printing. A printing device, which is a friction member mounted. 5. A printed circuit board is provided with a plurality of through holes corresponding to wirings, the printed circuit board is overlaid, and a solder paste is pushed into the through holes to print the solder paste. In a print mask for printing on wiring provided on a board, a concave portion is provided on a surface side of the printed board, which corresponds to the wiring on which the solder paste is printed, in contact with the printed board. And a print mask. 6. A printing method for screen-printing a solder paste on a printed circuit board with a predetermined pattern using a printing mask, wherein a fine pattern screen is printed using the first printing mask. −
And a second printing mask thicker than the first printing mask is used to print the solder paste on a portion other than the portion where the solder paste is printed by the first printing mask. A second step of printing a strike.