JP2000062138A - Printing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printing device which ensures the positive filling of a cream solder and is capable of stably printing without fear that the printing paste to a substrate would be bridged in its supply, in a filling step to fill the interior of a printing mask opening part with the cream solder under such circumstances that a distance between adjacent parts in a printing pattern becomes ever shorter caused by a fine patterning trend. SOLUTION: A cream solder 5 is pressurized in a chamber 16 by supplying a compressed air into a paste tank 7 with the help of an air compresser. Thus a filling pressure can be controlled with high accuracy and therefore, the cream solder 5 can be packed into the through hole 2a of a screen mask 2 under an appropriate filling pressure from a discharge aperture 4. Consequently the cream solder 5 can be packed under an equal pressure free from a peak pressure and a leakage or a bridging phenomenon can be prevented from occurring.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing apparatus such as a flat plate stencil type (screen type) for printing cream solder on lands of a circuit board in order to mount electronic parts on the circuit board.

[0002]

2. Description of the Related Art In a conventional printing apparatus, as shown in FIGS. 8 and 9, for example, in a plate stencil (screen) type printing in which cream solder 31 is printed on a land 33 of a printed circuit board 32, a printed circuit board 32 is used. Of the screen mask (metal mask) 34 having through holes 35 arranged in a predetermined pattern corresponding to the lands 33 of the circuit board 32.
Position and contact the upper predetermined position. Next, the cream solder 31 is supplied to one end of the screen mask 34 [FIGS. 8A, 8 </ b> B and 9 </ b> A], and the squeegee 37 moves the cream solder 31 from one end of the screen mask 34 in a predetermined direction. Screen mask 3 by
The cream solder 31 is filled in the through hole 35 of No. 4. Next, the screen mask 34 is removed from the substrate 32 [FIGS. 8 (c) and 9 (d)] to move the cream solder 31 ′ in the through hole 35 of the screen mask 34 onto the land 33 of the substrate 32, Cream solder layer 3
1 ″ is formed on the board land 33 [FIG. 8 (d), FIG.
(E)].

[0003]

However, in the structure described above, as shown in FIG. 8B, when the cream solder 31 is filled in the opening of the through hole 35 of the screen mask 34, squeegeeing occurs. The internal pressure of the cream solder 31 generated by the temporary increase becomes too high, and the leak 31a leaks between the screen mask 34 and the board land 33.
Will occur. Also, at the time of filling, the screen mask 3
If a gap 39 is generated between the board 4 and the board land 33, a cream solder leak 31a is further induced. As a result, the cream solders 31 ″ of the adjacent patterns come into contact with each other, which causes printing failure due to the bridge. For example, FIG. 5 (a) shows the pressure profile due to this squeegee. At the moment, the filling pressure rapidly rises and a peak is generated, and this peak causes the printing bridge due to the excessive filling pressure.

Furthermore, with the recent trend toward lighter, thinner, shorter, and smaller electronic devices, there is an increasing demand for miniaturization of electronic devices and finer mounting patterns in the circuit board manufacturing process. Similarly, in the cream solder printing process as well. Adjacent print pattern pitch is smaller. Under such conditions, it is obvious that the printing defects such as the printing bridges mentioned above are drastically increased.

When mounting electronic components under such severe conditions, not only the printing quality of the main printing process but also the quality of the entire line from the mounting of the electronic components to the final reflow process is taken into consideration. Preventing one's own deterioration is also important.

Furthermore, when handling conventional cream solder, it is unavoidable that the cream solder adheres to the human body including the squeegee and screen mask, and maintenance such as cleaning takes a lot of time and effort. Was there.

Therefore, in order to solve the above problems, an object of the present invention is to provide a "reliable filling even under a narrow adjacent pitch in the filling step when filling the solder paste into the openings of the printing mask with the cream solder. It is possible to perform stable printing without bridging the supply of printing paste to the printer, and to "provide a clean printing device with significantly reduced maintenance time."

[0008]

In order to achieve the above object, the present invention applies a printing unit in a chamber in which a discharge port is formed to a filling unit which is movable on a plate by a pressurizing unit. According to the above configuration, the printing paste in the chamber can be uniformly and appropriately pressurized by the pressurizing means to fill the through hole of the plate. Further, it is possible to prevent leakage and bridges due to excessive pressure, and improve print quality.

[0009]

DETAILED DESCRIPTION OF THE INVENTION The invention of claim 1 according to the present invention is as follows:
A printing device for arranging a plate on which a through hole is formed according to a predetermined printing pattern on a printing medium, and filling a printing paste into a through hole opening of the printing plate to print on the printing medium,
A filling unit movable on the plate, a chamber in which a discharge port is formed facing the plate and the printing paste is filled,
It is characterized by comprising a pressurizing means for pressurizing the printing paste in this chamber and extruding it from a discharge port,
According to the above configuration, in the filling step of filling the printing paste into the through hole opening of the screen mask, the pressure of the printing paste in the chamber is applied by the pressurizing means, thereby filling the printing paste into the through hole opening. The filling pressure can be controlled with a high degree of accuracy to maintain the value at an appropriate value, and the print quality can be improved.

According to a second aspect of the present invention, in the printing apparatus, a pair of scraping blades that are pressed against the plate and slide at the front and rear positions of the discharge port in the moving direction of the filling unit are provided. According to the above configuration, the scraping blade can scrape off the excess printing paste and completely bring the plate and the printing medium into close contact with each other, so that the occurrence of bridges and the defective printing paste can be effectively prevented. can do.

According to a third aspect of the present invention, in the printing apparatus, the chamber has a closed structure that shuts off the chamber from the atmosphere. According to the above configuration, the freshness of the printing paste is maintained, It is possible to prevent deterioration of the printing paste.

According to a fourth aspect of the present invention, in the printing apparatus of the fourth aspect, a paste tank constituting a part of the pressurizing means is detachably attached to the filling unit, and a supply port of the paste tank and the chamber are provided. A shutter mechanism that opens and closes the discharge port is provided by forming a passage that connects the discharge port with the shutter mechanism. By closing, the filling unit can be refrigerated and stored, and it is possible to reduce the burden on the operator for maintenance by eliminating the time and effort for cleaning the printing paste.

According to a fifth aspect of the present invention, in the printing apparatus according to the fourth aspect, the width of the passage is narrower than the width of the chamber and is formed over the entire length of the chamber. The printing paste in the paste tank can be extruded into a narrow passage by a pressurizing means and spread over a wide range so as to be uniformly supplied to the entire inside of the chamber and filled without forming a gap. Therefore, it becomes possible to uniformly and stably fill the print hole opening portion with the printing paste from the chamber through the discharge port by the pressurizing means, prevent printing defects such as omission, and further improve print quality. You can

According to a sixth aspect of the present invention, there is provided a printing apparatus according to the above-mentioned constitution, characterized in that the pressurizing means is provided with a pressure fluid supply device for pressing the printing paste with a predetermined pressure by the pressure fluid. According to this, uniform pressurization and pressure control of the printing paste can be easily performed, and the handling becomes easy.

An embodiment of a plate stencil (screen) type printing apparatus according to the present invention will be described in detail below with reference to FIGS. As shown in FIGS. 1 to 3, in this printing apparatus, a screen mask (metal mask) 2 is formed on a land 1a of a printed circuit board 1 which is an object to be printed by a through hole formed in accordance with a predetermined printing pattern. 2a is positioned so that it is positioned, and a filling unit 3 that is movable in the front-rear direction is provided from one end to the other end on the screen mask 2 by a moving mechanism (not shown). Then, the cream solder 5, which is a printing paste, is filled into the opening of the through hole 2a from the discharge port 4 formed in the lower portion of the filling unit 3 to print on the land 1a of the circuit board 1. The filling unit 3 and the discharge port 4 have a left-right width L = 260 mm so as to be compatible with all circuit boards 1.
It is formed to a degree.

At the top of the filling unit 3 is a mounting port 6
Three paste tanks 7 serving as solder supply sections are detachably set up in the width direction with a constant pitch P = 84 mm. The paste tank 7 is filled with the cream solder 5 and constitutes a part of the pressing means. That is, in this pressurizing means, an air compressor 9 which is a fluid supply device is connected to an input port 7a of the paste tank 7 via an air hose 8, and a pressure adjusting valve 12 is interposed in the air hose 8 to provide a filling pressure control device. 11 is configured to control the pressure of compressed air that is a pressure fluid.

Inside the filling unit 3, a passage 13 communicating with the mounting port 6 is formed by a package 14 which is an interior material made of resin or the like, and the package 14 is PP (polypropylene). ) Or the like resin molded product having a thickness of about 1 mm is molded and is detachably mounted in the filling unit 3. Since it can be made inexpensive, it can be discarded after use, or it can be washed and reused. The filling unit 3 itself may be resin-molded to form the passage 13.

Further, a pair of front and rear scraping blades 15, 15 are attached to the lower portion of the filling unit 3 in parallel with each other along the entire width direction, and a paste discharge port 6 is formed between the tip ends of the scraping blades 15, 15. Further, a chamber 16 having a substantially rhombic cross section is formed by the scraping blade 15 over the entire width direction except both end faces.

As a result, the cream solder 5 contained in the three paste tanks 7 is pushed out by the compressed air press-fitted from the input port 7a, the chamber 16 is filled through the passage 13 covered with the package 14, and The through hole 2 a of the screen mask 2 is filled from the ejection port 4 and applied onto the circuit board 1.

This chamber 16 is used for all circuit boards 1.
It is configured to have a length L that is compatible with the above, and the cream solder 5 is filled from the three mounting ports 6.
Has a high viscosity, the cream solder 5 may not spread sufficiently in the chamber 16. However, here, as a countermeasure, the front and rear clearances of the passage 13 are narrowed to about 2 to 3 mm, and the height of the passage 13 is made sufficiently long to about 60 mm, so that the cream solder 5 supplied from three places can pass through the passage 13. It is devised so that it spreads sufficiently in the width direction during passage and the cream solder 5 is quickly filled in the entire area of the chamber 5. In this way, once the chamber 16 is filled with the cream solder 5, the cream solder 5 is incompressible, so that the input port 7a
The pressure of the compressed air, which is more pressurized, remains unchanged in the chamber 1
6 can be propagated in and function as a filling pressure. Therefore, by operating the pressure adjusting valve 12 by the filling pressure control device 11 to control the pressure of the compressed air,
The filling pressure of the cream solder 5 can be accurately controlled.

However, as shown in the reference diagram of FIG. 7, when the volume of the chamber 16 ′ is large and the chamber 16 ′ cannot be filled with the cream solder 5, the filling unit 3 fills the cream solder 5 with the cream solder 5. When it moves on the screen mask 2, the cream solder 5 adheres to the screen mask 2 at the ejection port 4, the cream solder 5 flows and shifts inside the chamber 16 ′, and printing defects occur. Therefore, the chamber 16 preferably has a relatively small volume, and preferably has a size as shown in FIG. 1, for example, a front-rear gap of 30 mm and a height of 20 mm or less. Also, the shape of the chamber 16 is
Although it may have a rhombic cross section as shown in FIG. 1, it may have a circular or curved cross section to facilitate the flow of the cream solder 1 in the chamber 16.

Of the pair of scraping blades 15, the rear one is that the cream solder 5 is filled from the discharge port 4 into the opening of the through hole 2a of the screen mask 2 and then slid on the upper surface of the screen mask 2. , Extra cream solder 5
Scrape off. The scraping blade 15 has a thickness of 0.3.
It has been confirmed that good scraping is performed by using a thin metal plate of about mm and setting the attachment angle θ to the screen mask 2 to 45 degrees or less. Further, the pair of scraping blades 15 presses the screen mask 2 at the front and rear positions of the discharge port 4 to completely remove the gap 17 between the screen mask 2 and the circuit board 1 [see FIG.
(B)] can be eliminated.

As shown in FIG. 2, the filling unit 3 is provided with a shutter mechanism 23 including a pair of shutter blades 21 for opening and closing the discharge port 4 below the scraping blade 15 and a shutter opening / closing device 22. There is.
That is, in this shutter blade 21, the blade plates 21c are attached to the pair of L-shaped supports 21b that are movably moved toward and away from each other via the guide rods 21a in the front-rear direction. Mounted at angle δ. In addition, the shutter opening / closing device 22 uses the opening / closing cylinder 22a to move the pin 22 in the width direction.
a pair of front and rear L-shaped links 2 which are swung around b and 22b
The blades 21c, 21c are opened and closed by moving the L-shaped supports 21b, 21b close to and away from each other via 2c, 22c. The shutter mechanism 23 can close the discharge port 4 by the shutter drive device 23 as shown by a phantom line in FIG. 2 when the filling unit 3 is not used, and remains in the chamber 16 after use. The cream solder 5 can be hand-sealed when the shutter blade 21 is closed, and the paste tank 7 can be removed to store the filling unit 3 in a refrigerator. And time can be significantly reduced.

Next, a printing method by the printing apparatus having the above structure will be described with reference to FIG. First, a screen mask 2 having through holes 2a arranged in a fixed pattern corresponding to the lands 1a of the printed circuit board 1 is positioned and contacted at a predetermined position on the circuit board 1. Then, the filling unit 3 is arranged at one end of the screen mask 2, the pressure adjusting valve 12 is adjusted by the filling pressure control device 11, and compressed air of an appropriate pressure is input from the air compressor 9 to the input port 7a.
Is supplied to the paste tank 7 and the cream solder 5 is applied with a filling pressure in an appropriate range [FIG. 4 (a)]. Then, by moving the filling unit 3 forward, the cream solder 5 in the chamber 16 is pressurized from the passage 13 to fill the through hole 5 of the screen mask 2 from the discharge port 4 with an appropriate pressure [FIG. 4 (b)]. ]. Then, the screen mask 2 is peeled off from the circuit board 1 [FIG. 4 (c)], so that the cream solder 5 a filled in the through hole 2 a is removed from the circuit board 1.
And the cream solder layer 5b is formed on the land 1a of the substrate 1 [FIG. 4 (d)].

FIG. 5B is a diagram showing a profile of the filling pressure at an arbitrary point on the screen mask 2.
The profile of the filling unit of the present invention shows a substantially uniform filling pressure, and the conventional squeegee method [Fig.
Since the peak as in (a)] does not occur, the print bridge does not occur. According to the experiment, the necessary proper filling pressure range for filling is 0.1 to 0.1.
It has been found to be 5 kgf / cm ² , and by setting the pressure from the input port 7a in the range of 0.1 to 0.15 kgf / cm, the filling pressure can be accurately controlled within an appropriate range.

FIG. 6 is a graph showing the effect of reducing the gap between the screen mask 2 and the circuit board 1. From this data, screen mask 2 and circuit board 2
It is clear that the smaller the gap between the two is, the less the print defects are. In the present invention, since the screen mask 2 is pressed by the two scraping blades 15 before and after the ejection port 4, the gap can be almost eliminated. By this pressing, printing defects can be effectively prevented.

According to the above embodiment, in the filling step of filling the cream solder 5 into the opening of the through hole 2a of the screen mask 2, the pressing means 21 pressurizes the cream solder 5 in the chamber 16 with an appropriate pressure. As a result, the filling pressure can be controlled in a proper range with high accuracy, stable filling is possible, and print quality can be improved. Further, by pressing the screen mask 2 with the pair of scraping blades 15 at the front and rear positions of the discharge port 4 of the cream solder 5, it is possible to eliminate the gap between the screen mask 2 and the circuit board 1, and the cream solder 5 has a gap. It is possible to prevent leakage from the outside and prevent printing defects such as bridges. Further, by containing the cream solder 5 in the chamber 16 of the filling unit 3 and the passage 13 of the package 14 in a sealed state, contact with air can be avoided, deterioration can be prevented, and the freshness of the cream solder 15 can be maintained. Further, since the discharge port 4 can be closed by the shutter mechanism 23 and the paste tank 7 can be removed to store the filling unit 3 in a refrigerated state, maintenance can be facilitated and the burden on the operator can be reduced.

[0028]

According to the above invention, the pressurizing means can control the proper filling pressure of the printing paste in the chamber to stably fill the through holes of the plate, so that the leakage of the bridge or the bridge due to the excessive pressure can be prevented. Occurrence can be prevented, and print quality can be improved.

[Brief description of drawings]

FIG. 1 is a side sectional view of a filling unit showing an embodiment of a printing apparatus according to the present invention.

FIG. 2 is a side view of the filling unit.

FIG. 3 is a front half sectional view showing the filling unit.

4A to 4D show printing states by the same printing device, FIG. 4A is a cross-sectional view showing a state of cream solder at the start of cream solder filling, and FIG. 4B is a cream at the end of filling. Sectional view showing the state of solder, (c) is a sectional view showing the state of cream solder when the screen mask and the circuit board are separated, (d) is a sectional view showing the state of cream solder at the end of printing .

5A and 5B are filling pressure profiles, FIG. 5A is a graph showing a conventional squeezing profile, and FIG. 5B is a graph showing a profile according to the printing apparatus of the present invention.

6A is a diagram showing a change in a print defect occurrence rate depending on a gap amount between a screen mask and a substrate, and FIG. 6B is an explanatory diagram of the gap amount.

FIG. 7 is a cross-sectional view showing a modified comparative example of the filling unit of the present invention.

8A to 8D show a printing state by a conventional printing device, FIG. 8A is a sectional view showing a state of cream solder at the start of cream solder filling, and FIG. 8B is a cream at the end of filling. Sectional view showing the state of solder, (c) is a sectional view showing the state of cream solder when the screen mask and the circuit board are separated, (d) is a sectional view showing the state of cream solder at the end of printing .

9A to 9E are explanatory views of a conventional printing procedure, FIG. 9A is a perspective view illustrating a conventional printing apparatus, and FIG. 9B is a front view illustrating a conventional printing apparatus. , (C)
Is a cross-sectional view showing a filled state of cream solder, (d) is a cross-sectional view illustrating a detached state of the mask screen,
(E) is a perspective view showing a printing state.

[Explanation of symbols]

1 circuit board 2 screen mask 2a through hole 3 filling unit 4 outlets 5 cream solder 7 paste tank 9 Air compressor 11 Filling pressure controller 12 Pressure control valve 13 passages 14 packages 15 Scraping blade 16 chambers 17 Gap 21 shutter blade 22 Shutter open / close device 23 Shutter mechanism

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Toshinori Mimura             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Dai Yamauchi             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. F-term (reference) 2C035 AA06 FC04 FD01 FD27 FD35                       FD37 FD44 FF26                 5E319 BB05 CC33 CD29 GG05                 5E343 BB72 DD03 DD64 ER50 FF02

Claims (6)

[Claims] 1. A printing apparatus in which a plate having through holes formed according to a predetermined printing pattern is arranged on a printing medium, and printing paste is filled in the through hole openings of the printing plate to print on the printing medium. There is a filling unit that is movable on the plate, a chamber that is formed with discharge ports facing the plate and is filled with printing paste,
A printing apparatus comprising: a pressurizing unit that pressurizes the printing paste in the chamber and pushes it out from a discharge port. 2. The printing apparatus according to claim 1, further comprising a pair of scraping blades which are pressed against the plate and slide at the front and rear positions of the discharge port in the moving direction of the filling unit. 3. The printing apparatus according to claim 1, wherein the chamber has a closed structure that shuts off the chamber from the atmosphere. 4. A paste tank constituting a part of the pressurizing means is detachably attached to the filling unit, and a passage connecting the supply port of the paste tank and the chamber is formed, and the discharge port is provided. The printing apparatus according to claim 1, further comprising a shutter mechanism that can be opened and closed. 5. The printing apparatus according to claim 4, wherein the width of the passage is narrower than the width of the chamber and is formed over the entire length of the chamber. 6. The printing apparatus according to claim 1, further comprising a pressure fluid supply device that presses the printing paste with a predetermined pressure by the pressure fluid.