JP2008221541A - Method and equipment for screen printing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a screen printing method which enables high-speed and high-accuracy filling a hole having a high aspect ratio with printing material. <P>SOLUTION: The printing material 3 is scraped by moving in the printing direction F a squeegee 1 which keeps the rear part in the printing direction F in contact with the surface of a printing mask 6, and the printing material 3 scraped and moved by the squeegee 1 is supplied onto the printing mask 6 through a gap G2 between first and second rollers 21 and 22 by the first and second rollers 21 and 22 being parallel to the printing mask 6, by rotating the first roller 22 toward the second roller 21 and the second roller 22 toward the first roller 21. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a screen printing method for printing a conductive printing material on an electronic circuit board.

  In the production of electronic circuit boards, conductive paste is printed on the board by screen printing, electronic parts such as chip parts are placed there, soldered, and electronic parts are mounted on the land of the wiring pattern. An electronic circuit is built.

An example of a conventional printing apparatus used for printing is shown in FIGS.
In the printing apparatus shown in FIG. 4, the mask 6 is set on the printing surface of the substrate 4, and the printing direction (arrow F direction) is set to the left in order to fill the opening 6 a formed in the mask 6 with the printing material. When viewed from the right, the roller 10 in front of the squeegee 1 is rotated counterclockwise to create a high pressure portion 12 where the printing material 11 convects against the printing surface at the rear of the roller 10. Thus, the opening 6a is filled with a printing material.

Alternatively, as shown in FIG. 5, a sealed space of the printing material 11 is created between the squeegee 1 and the roller 13, and the printing material 11 is scraped into the sealed space by rotating the roller 13 in the printing direction (arrow F direction). This creates a high pressure region and fills the opening 6a of the screen 6 with the printing material.
JP 09-239955 A Japanese Patent Laid-Open No. 2005-229094

  In the method of FIG. 4, since the pressure of the printing material in the opening 6a of the mask 6 is low, the printing material filling force into the high aspect ratio hole is insufficient. Further, in the method of FIG. 5, the generation of the component in the vertical direction is small with respect to the convection printing surface of the printing material, and the printing material filling force into the high aspect ratio hole is insufficient.

  Furthermore, in the above two methods, the space between the squeegee 1 at the rear of the roller 13 and the printing surface, particularly in the vicinity of the contact portion of the squeegee printing surface, is at high pressure, so as shown in FIG. There is also a problem that the printing material remains as shown in b).

  When the pressure on the printing surface of the squeegee is increased in order to solve the problem, damage to the mask 6, the substrate 4, and further the squeegee 1 occurs, and the durability of the printing member such as the squeegee 1 and the mask 6 is increased. This is a cause of deterioration of accuracy.

  Further, when the pressure immediately before the squeegee 1 is high and there is a large opening on the printing surface, the printing material at the rear of the squeegee is caused by the pressure at the front of the squeegee through the opening as shown in FIG. As shown in a), a phenomenon of rising occurs.

  Further, as shown in FIG. 7, when the squeegee 1 is made of a soft resin material or the like, if the squeegee 1 is highly pressed, the squeegee 1 is allowed to enter the opening 6a when the printing surface has a large opening. Therefore, as shown in (c), the printing material is filled less than the required amount. On the other hand, when the material of the squeegee 1 is hard, the decrease in the filling amount of the printing material is reduced, but damage to the mask 6 on the printing surface, the electronic circuit board, or the squeegee occurs, and the durability of each member is increased. Problems such as loss of printing performance and deterioration of printing accuracy occur.

  The present invention relates to a screen printing method and a screen printing apparatus capable of sufficiently filling a printing material into an opening having a high aspect ratio, sufficiently filling the printing material, and stably performing the operation at high speed. The purpose is to provide.

  In the screen printing method according to the first aspect of the present invention, the squeegee whose rear portion is in contact with the surface of the printing mask with respect to the printing direction is moved in the printing direction to scratch the printing material, and is moved by being scratched by the squeegee. The printing material is rotated by the first and second rollers parallel to the printing mask, the first roller is rotated toward the second roller, the second roller is rotated toward the first roller, The sheet is supplied from the gap between the first and second rollers toward the top of the printing mask.

According to a second aspect of the present invention, the screen printing method according to the first aspect is characterized in that the squeegee and the first and second rollers are moved in the printing direction at the same speed.
The screen printing apparatus according to claim 3 of the present invention is arranged in a squeegee whose rear portion is in contact with the surface of the printing mask with respect to the printing direction, and in the printing material accumulated between the squeegee and the printing mask. The first and second rollers parallel to the printing mask, the printing mask and the squeegee are moved relative to each other to scrape the printing material, and the first roller is rotated toward the second roller. Drive means for rotating the first roller toward the first roller and supplying the roller toward the top of the printing mask through a gap between the first and second rollers.

A screen printing apparatus according to a fourth aspect of the present invention is the screen printing apparatus according to the third aspect, wherein the squeegee and the first and second rollers are moved in the printing direction at the same speed.
The screen printing apparatus according to claim 5 of the present invention is characterized in that, in claim 3, the gap between each roller and the printing mask is narrower than the gap between the first and second rollers.

  A screen printing apparatus according to a sixth aspect of the present invention is the screen printing apparatus according to the third aspect, wherein a gap between the second roller and the squeegee behind the first and second rollers in the printing direction is the second. It is characterized by being wider than the gap between the roller and the printing mask.

The screen printing apparatus according to claim 7 of the present invention is characterized in that, in claim 3, the first and second rollers have the same diameter.
The screen printing apparatus according to an eighth aspect of the present invention is the screen printing apparatus according to the fourth aspect, wherein the driving means has a speed of the surfaces of the first and second rollers higher than a traveling speed of the first and second rollers and the squeegee. The first and second rollers are rotationally driven so as to be faster.

A screen printing method according to a ninth aspect of the present invention is the screen printing method according to the first aspect, wherein the printing step is performed in a vacuum.
The screen printing method according to claim 10 of the present invention is characterized in that in claim 9, the printing apparatus includes a step of placing the printing apparatus in the atmosphere after printing.

  A screen printing apparatus according to an eleventh aspect of the present invention is the screen printing apparatus according to the eighth aspect, wherein the printing material is circulated around the squeegee and the first and second rollers in a vacuum to defoam.

  According to this configuration, it is possible to increase the filling force of the printing material onto the printing surface, thereby filling the printing material with high speed and high accuracy into the opening having a higher aspect ratio, and from the squeegee press. It is possible to solve the problems caused by the increased pressure of the printing material near the contact point between the squeegee and the printing mask.

Hereinafter, the screen printing method of the present invention will be described based on specific embodiments.
(Embodiment 1)
FIG. 1 shows a screen printing apparatus for executing the screen printing method of the present invention. Specifically, the electronic circuit board 4 is set on the stage 7. Printing is performed for the purpose of filling the conductive paste 3 as a printing material into the opening 6 a such as a hole of the electronic circuit board 4.

A mask 6 is disposed on the surface of the multilayer electronic circuit board 4 in which a large number of openings 6a are present. There are a variety of openings 6a, such as those that penetrate the substrate and holes that reach the middle of the substrate.
Then, the rear end of the plate-like squeegee 1 is arranged in contact with the surface of the mask 6. Then, the first and second rollers 21 and 22 are arranged in parallel with the mask 6 in a direction in which the axis intersects the printing direction F. Specifically, the electronic circuit board 4 and the mask 6 are the fixed side, and the arrow F direction is the printing direction.

  A cylindrical second roller 22 with respect to the fixed side is arranged in front of the squeegee 1 in the printing direction in parallel to the printing surface of the squeegee 1 and the electronic circuit board 4. The first roller 21 is arranged in front of the second roller 22 in the printing direction. The first roller 21 and the second roller 22 have the same diameter.

  The first and second rollers 21 and 22 are arranged with a gap G1 of 1 mm to 5 mm from the mask 6 with respect to the printing direction. The gap G2 between the first and second rollers 21 and 22 is adjusted to about 5 mm to 20 mm. The gap G3 at the closest part between the squeegee 1 and the second roller 22 is adjusted to about 5 mm to 10 mm, which is larger than the gap between the mask 6 and the first and second rollers 21 and 22.

  An amount of the conductive paste 3 is supplied to such an extent that both the first and second rollers 21 and 22 are hidden. The squeegee is made of hard rubber such as urethane rubber or metal.

  Here, the drive means is configured to move the squeegee 1 and the first and second rollers 21 and 22 in the printing direction F at the same speed. Further, at the time of printing, the driving unit rotates the first roller 21 in front of the printing direction in the reverse direction of the printing direction, and the second roller 22 behind in the printing direction rotates in the printing direction. . These rotational speeds are such that the peripheral speeds of the respective roller surfaces are larger than the speed at which the first and second rollers 21 and 22 move in the printing direction F during printing. In this state, the first and second rollers 21 and 22 and the squeegee 1 are moved in the printing direction F at the same speed. The printing direction is the right side of the figure, and more specifically, is a direction parallel to the electronic circuit board 4 and perpendicular to the squeegee.

  The positions of the squeegee 1 and the first and second rollers 21 and 22 are independently adjustable, and the squeegee 1 is mounted so that it can automatically move up and down.

  Further, at the time of printing, the screen printing apparatus shown in FIG. 1 is disposed in a closed space, for example, a vacuum environment, and a printing operation is performed after being in a vacuum state, and then an atmospheric pressure that is higher than the printing state. The printing operation is performed once again.

By printing by this screen printing method, the following phenomenon occurs.
First, as shown in FIG. 1, the A part, the B part, and the C part are considered, the pressure outside the paste is P0, the pressure of the A part before the roller from the paste surface part is P1, the first and second rollers 21 and 22 P2 is the pressure in the B portion, which is a region pressurized by the paste flow generated by the above, and P3 is the pressure in the portion between the rear roller, the squeegee, and the printing surface at the end in the printing direction.

  In part A, the paste surface is almost equal to the external pressure P0. And pressure becomes high as it becomes the paste inside. In addition, the flow is generated by the first and second rollers 21 and 22, and the region B that is the destination of the flow is the gap between the first and second rollers 21 and 22 and the mask 6 as described above. Since it is narrower than the distance between the two rollers that are the inflow source of the paste, the amount of paste that flows out from the region B is smaller than the amount that flows into the region B. Therefore, the pressure of P2 becomes high.

  The pressure of P3 is such that the paste tends to concentrate on the contact portion between the squeegee 1 and the mask 6 due to the friction between the mask 6 and the printing material as the first and second rollers 21 and 22 and the squeegee 1 advance. Since the printing material is scraped forward and upward by the rear second roller 22 and the pressure is reduced, the pressure of P3 is lowered. This pressure can be adjusted by the rotational speed of the second roller 22 at the rear portion.

These pressures vary depending on the degree of vacuum around the printing material and the printing area, printing speed, roller rotation speed, squeegee angle, etc., but by adjusting them appropriately,
P0 <P3 <P1 <P2
It can be.

  In addition, since the paste flow between the first and second rollers 21 and 22 is generated from the upper side to the mask 6 due to the rotation of the first and second rollers 21 and 22, the inertia and the pushing from the upper side also occur. The paste filling force into the opening 6a of the mask 6 is increased.

  By simultaneously increasing the pressure of the paste in the filling area and the inertia and indentation force due to flow, the paste can be filled accurately and at high speed into holes with a high aspect ratio, which was impossible with conventional printing methods. It becomes possible.

  At the same time, since the pressure near the contact portion between the squeegee and the mask 6 can be reduced, damage to the mask 6, the substrate 4, and the squeegee 1 due to paste scraping leakage and increased squeegee pressure can be reduced.

  Further, it is possible to prevent a shortage of paste filling amount resulting from squeegee deformation caused by squeegee pressing at the large opening 6a, which can be considered when a soft material is used as the squeegee 1.

  Furthermore, since the paste 3 circulates around the squeegee 1 and the first and second rollers 21 and 22 and convects, the defoaming of the paste 3 can be performed simultaneously by performing the printing in a vacuum.

  When printing is performed in a vacuum, if the pressure is returned to atmospheric pressure after the printing operation, the printing material may drop into the opening of the printing surface, and the printing surface may become uneven. In this case, high final printing accuracy can be ensured by performing another printing operation at atmospheric pressure.

  Further, in this embodiment, when the diameters of the first and second rollers 21 and 22 are the same and the amount of the gap between each roller and the printing surface is the same, the squeegee 1 is placed in front of the printing direction and the front and rear are opposite. By arranging the squeegee up and down in such a way that the vertical movement of the squeegee can be set separately for the forward path and the return path, printing can be performed not only on the forward path but also on the return path.

(Embodiment 2)
FIG. 2 shows a second embodiment of the present invention.
In FIG. 1 showing the first embodiment, the first and second rollers 21 and 22 have the same diameter. However, in the second embodiment, the first roller 21 has a diameter larger than that of the second roller 22. Is thick. The arrangement of the electronic circuit board 4, the squeegee 1, and the rollers is almost the same as that in the first embodiment. Specifically, the diameter of the first roller 21 was made approximately 1 to 10 mm larger than the diameter of the second roller 22.

With this configuration, the pressure P1 is applied by the air pressure P0 outside the paste 3, the pressure P1 of the portion A before the first roller 21 from the surface portion of the paste 3, and the flow of the paste generated by the first roller 21. The pressure P21 of the B1 portion that is the area that has been printed, the pressure of B2 that is between the first and second rollers 21 and 22 and the printing surface P22, the second roller 22 and the squeegee 1 at the end of the printing direction The relationship of the pressure P3 of the part C part between the surfaces is
P0 <P3 <P1 <P21 <P22
Compared to the first embodiment, it can be expected that the pressure on the printing surface at the B2 portion is further increased. In addition, since it is possible to simultaneously generate a component in the paste flow direction perpendicular to the printing surface in the high-pressure portion of the paste, it is possible to fill the paste into a hole with a high aspect ratio. At the same time, similarly to the first embodiment, the pressure of P3 can be kept low, so that damage to the mask, the substrate, and the squeegee due to paste scraping leakage and increased squeegee press can be reduced.

(Embodiment 3)
FIG. 3 shows a third embodiment of the present invention, in which the printing material pressurizing portion constituted by the first and second rollers 21 and 22 is replaced with the first, second and third rollers 21, 22 and 23. By arranging three or more like as described above, the same effect can be obtained by adjusting the high pressure of the B part and the flow direction of the paste in the same manner. Here, the first and second rollers 21 and 22 are rotationally driven in the same direction as in the first embodiment, and the third roller 23 is rotationally driven in the same direction as the first roller 21.

  In each of the above embodiments, even in printing in which the roller of the printing material pressurizing unit is not buried in the printing material, the printing material can be flowed and the pressure between the printing surface and the plurality of rollers can be increased. If there is, the same effect can be expected.

In each of the above-described embodiments, even if the roller of the printing material pressurizing unit has a shape other than the cylindrical shape, the pressure changes with time, but the same effect can be expected.
In each of the above embodiments, the finish is obtained by changing the diameter and the shape of the roller of the printing material pressurizing unit in the axial direction according to the filling location of the paste 3, the paste state, and the opening location of the printing object. It is also possible to adjust the accuracy and the printing accuracy uniformity of the printing surface.

The block diagram which looked at the screen printing apparatus of Embodiment 1 of this invention from the cross section perpendicular | vertical to a printing direction. The block diagram which looked at the screen printing apparatus of Embodiment 2 of this invention from the cross section perpendicular | vertical to a printing direction. The block diagram which looked at the screen printing apparatus of Embodiment 3 of this invention from the cross section perpendicular | vertical to a printing direction. Configuration diagram of a conventional printing device using resin convection Configuration diagram of a conventional printing device that prints by increasing the resin pressure Diagram showing conventional printing with high pressure near the contact area between the squeegee and printing surface Figure showing conventional printing with soft squeegee material and increased squeegee pressure

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Squeegee 21 1st roller 22 2nd roller 3 Conductive paste (printing material)
4 Electronic circuit board 6a Opening 6 Mask 7 Stage

Claims (11)

The squeegee whose rear part is in contact with the surface of the printing mask with respect to the printing direction is moved in the printing direction to scratch the printing material, and the printing material that is scratched and moved by the squeegee is parallel to the printing mask. By the second roller, the first roller is rotated toward the second roller, the second roller is rotated toward the first roller, and the gap between the first and second rollers is A screen printing method for supplying a printing mask. The screen printing method according to claim 1, wherein the squeegee and the first and second rollers are moved in the printing direction at the same speed. A squeegee whose rear part is in contact with the surface of the printing mask with respect to the printing direction;
First and second rollers disposed in a printing material collected between the squeegee and the printing mask and parallel to the printing mask;
The printing mask and the squeegee are moved relative to each other to scrape the printing material, the first roller is rotated toward the second roller, the second roller is rotated toward the first roller, and the first roller is rotated. , A screen printing apparatus provided with driving means for supplying the printing mask from above the gap between the second rollers. The screen printing apparatus according to claim 3, wherein the squeegee and the first and second rollers are moved in the printing direction at the same speed. 4. The screen printing apparatus according to claim 3, wherein a gap between each roller and the printing mask is narrower than a gap between the first and second rollers. The clearance gap between the 2nd roller and the said squeegee of back with respect to the said printing direction among the 1st, 2nd rollers is wider than the clearance gap between a 2nd roller and the said mask for printing. Screen printing equipment. The screen printing apparatus according to claim 3, wherein the first and second rollers have the same diameter. The driving means includes
5. The first and second rollers are configured to be rotationally driven so that the surface speeds of the first and second rollers are faster than the traveling speeds of the first and second rollers and the squeegee. Screen printing equipment. The screen printing method according to claim 1, wherein the printing step is performed in a vacuum. The screen printing method according to claim 9, further comprising the step of placing the printing apparatus in the atmosphere after printing. The screen printing apparatus according to claim 8, wherein the printing material is defoamed by circulating the printing material around the squeegee and the first and second rollers in a vacuum.

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