JP4042491B2 - Screen printing apparatus and screen printing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a screen printing apparatus and a screen printing method for printing paste such as cream solder on a workpiece.
[0002]
[Prior art]
Known methods for soldering electronic components include solder bumps and solder precoat. In this method, a solder bump as a solder protruding electrode or a solder precoat as a solder film is formed on a workpiece electrode such as an electronic component or a substrate for solder bonding. Screen printing is widely used as a solder supply method in these solder formation processes. In this method, cream solder is printed on the upper surface of the workpiece through the pattern holes provided in the mask plate.
[0003]
[Problems to be solved by the invention]
By the way, in recent years, finer electronic components have progressed, and the pitch of electrodes formed on a workpiece has also been reduced, so that a large number of electrodes are densely formed at a narrow pitch. However, when screen printing conventionally used for such fine pitch electrodes is applied, good printing results cannot be obtained and various problems occur.
[0004]
In order to ensure good print quality in screen printing, the paste should be removed from the pattern hole when the plate is released to separate the mask plate from the workpiece after filling, as well as the filling ability to reliably fill the pattern hole with the paste. It is required that the separation property of the plate to be separated is good. However, the difficulty of printing increases with the fine pitch, and it is very difficult to ensure uniform and good plate release properties over the entire surface of the workpiece.
[0005]
SUMMARY OF THE INVENTION An object of the present invention is to provide a screen printing apparatus and a screen printing method that can ensure good plate release properties.
[0006]
[Means for Solving the Problems]
2. The screen printing apparatus according to claim 1, wherein a mask plate on which a pattern hole is formed is mounted on a work and a paste is printed on the work through the pattern hole, wherein the mask plate is placed on the upper surface of the work. A mask mounting means for mounting in contact with the mask plate, a squeegee for filling the pattern hole by moving on the mask plate in the mounted state, and a plate with the workpiece relatively spaced from the mask plate. A plate separating means for performing a separating operation, and a mask pressing mechanism as a mask following means for displacing the mask plate in the separation direction of the workpiece and following the workpiece at the start of the plate separating operation, , it is disposed in the vicinity of both end portions of the horizontal movement range of the squeegee unit, the mask plate An elongated rod-like member abutting the linear position corresponding to the peripheral portion of the upper surface of the workpiece, comprising a lifting mechanism for lifting the elongated bar-like member.
[0007]
3. The screen printing method according to claim 2, wherein a mask plate on which a pattern hole is formed is mounted on a work and a paste is printed on the work through the pattern hole, the mask plate being placed on the upper surface of the work. A mask mounting step for mounting in contact with the mask plate, a squeegeeing step for filling the pattern hole with paste by moving a squeegee on the mask plate in the mounted state, and the workpiece relative to the mask plate. A plate separation step of separating the plate and performing a plate separation operation, and performing a mask follow-up operation to follow the workpiece by displacing the mask plate in the separation direction of the workpiece at the start of the plate separation operation,
The mask following operation corresponds to the peripheral portion of the workpiece on the upper surface of the mask plate by driving a mask pressing mechanism disposed near both ends of the horizontal movement range of the squeegee unit. The mask plate is brought into linear contact with the position, and the mask plate is pushed down in the separation direction of the workpiece to follow the workpiece.
[0008]
According to the present invention, at the start of the plate separation operation for relatively separating the workpiece from the mask plate, the mask plate is moved by the contact portion that linearly contacts the position corresponding to the peripheral portion of the workpiece on the upper surface of the mask plate. By pushing down and displacing in the workpiece separation direction to follow the workpiece, the difference in plate separation speed between the peripheral part and the center part of the work is minimized, and the plate separation conditions are uniform over the entire work surface. Can be secured.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings. 1 is a perspective view of a screen printing apparatus according to an embodiment of the present invention, FIG. 2 is a partial sectional view of the screen printing apparatus according to an embodiment of the present invention, and FIG. 3 is a screen printing according to an embodiment of the present invention. It is process explanatory drawing of a method.
[0010]
First, the structure of the screen printing apparatus will be described with reference to FIGS. In FIG. 1, a substrate positioning portion 2 for positioning a substrate as a work is disposed on a base 1. The substrate positioning unit 2 stacks a Z-axis table 6 that is moved up and down by an X-axis table 3, a Y-axis table 4, and a feed screw 5, and a substrate holding unit 7 that holds a substrate 8 by a clamper 9 on the Z-axis table 6. It is arranged and configured. As shown in FIG. 2, the lower surface of the substrate 8 is received by the lower receiving portion 6 a, and the Z-axis table 6 is moved up and down by the Z-axis drive mechanism 19. The Z-axis drive mechanism 19 is controlled by the plate separation control unit 20.
[0011]
On the base 1, a screen printing unit 10 is disposed above the substrate positioning unit 2. The screen printing unit 10 includes a mask plate 12 held by a frame-shaped holder 11, a squeegee unit 13 including a squeegee 16 that slides on the mask plate 12, and a squeegee moving table 14.
[0012]
By driving the X, Y, and Z axis tables of the substrate positioning unit 2 with the substrate holding unit 7 holding the substrate 8, the held substrate 8 is moved with respect to the mask plate 12 of the screen printing unit 10. It is possible to align and attach the lower surface of the mask plate 12 from below. Further, by lowering the Z-axis table 6 by the Z-axis drive mechanism 19 from this mask mounted state, the substrate 8 is separated from the lower surface of the mask plate 12 and the plate is separated.
[0013]
Therefore, the substrate positioning unit 2 and the substrate holding unit 7 serve as a mask mounting unit that mounts the mask plate 12 in contact with the upper surface of the substrate 8. The Z-axis table 6 including the substrate holding unit 7 and the Z-axis drive mechanism 19 serves as a plate separating unit that performs a plate separating operation by relatively separating the substrate 8 from the mask plate 12.
[0014]
In FIG. 1, the squeegee moving table 14 includes a feed screw 14b and a motor 14a. By driving the motor 14a, the squeegee unit 13 moves in the horizontal direction. As shown in FIG. 2, the squeegee unit 13 includes a pair of squeegees 16 that move up and down by a cylinder 15. The substrate 8 is positioned below the screen printing unit 10 and the mask plate 12 is brought into contact with the upper surface of the substrate 8. In this state, by driving the cylinder 15, the squeegee 16 is lowered and the lower end thereof comes into contact with the upper surface of the mask plate 12.
[0015]
The squeegee 16 scrapes the cream solder 17 on the mask plate 12 by driving the squeegee moving table 14 in a state where the cream solder 17 as paste is supplied onto the mask plate 12. By this squeezing operation, cream solder 17 is filled in the pattern holes 12a.
[0016]
A mask push-down mechanism 18 is disposed near the end of the horizontal movement range of the squeegee unit 13. The mask push-down mechanism 18 includes a contact portion 18 a that extends downward and contacts the mask plate 12 and a lifting mechanism that moves the contact portion 18 a up and down. The abutting portion 18a is a rod-like member that is elongated in the length direction of the substrate 8 (perpendicular to the paper surface in FIG. 2), linearly abuts at a position corresponding to the peripheral portion of the substrate 8 on the upper surface of the mask plate 12, The mask plate 12 is pressed against the periphery of the substrate 8. It should be noted that the position where the mask plate 12 is pushed down by the contact portion 18 a may be either inside or outside the end face of the substrate 8 as long as it is a peripheral portion of the substrate 8.
[0017]
The operation of the elevating mechanism of the mask depressing mechanism 18 is controlled by the plate separation control unit 20, whereby the mask plate 12 can be depressed with an arbitrary depressing amount and depressing speed by the abutting portion 18 a. By controlling by the plate separation control unit 20 so that the lowering operations of the mask pressing mechanism 18 and the Z-axis drive mechanism 19 are synchronized at the start of the plate separation operation, the mask plate 12 is made to follow the lowering operation of the substrate 8. Can do. That is, the mask push-down mechanism 18 and the plate separation control unit 20 serve as a mask follow-up unit that displaces the mask plate 12 in the separation direction of the substrate 8 and follows the substrate 8 at the start of the plate separation operation.
[0018]
This screen printing apparatus is configured as described above, and the screen printing operation will be described below with reference to FIG. First, the substrate 8 that is received by the lower support 6a of the substrate holder 7 and clamped by the clamper 9 is brought into contact with the lower surface of the mask plate 12, whereby the mask plate 12 is mounted on the substrate 8 (mask). Mounting process).
[0019]
Next, as shown in FIG. 3A, the squeegee 16 of the squeegee unit 13 is lowered and brought into contact with the mask plate 12 while the cream solder 17 is supplied onto the mask plate 12. Thereafter, by horizontally moving the squeegee unit 13, the squeegee 16 performs a squeezing operation of moving the cream solder 17 on the mask plate 12 while scraping it, and as shown in FIG. The cream solder 22 is filled (squeezing process).
[0020]
Thereafter, after the squeegee 16 is retracted, a plate separating operation for separating the substrate 8 from the mask plate 12 is performed (plate separating step). The plate separation is performed by lowering the Z-axis table 6 by the Z-axis drive mechanism 19. At the start of this plate separation operation, the Z-axis table 6 is lowered as shown in FIG. At the same time, a mask following operation is performed.
[0021]
That is, the mask pressing mechanism 18 is driven to bring the contact portion 18 a into contact with the mask plate 12. Then, the mask plate 12 is pushed down in the separation direction of the substrate 8 to follow the substrate 8. In the following operation of the mask plate 12, the lowering speed 18 of the mask pressing mechanism 18 may be smaller than the pressing speed of the Z-axis drive mechanism 19, and the mask pressing speed and the lowering speed of the Z-axis driving mechanism 19 are the same. May be made to follow completely.
[0022]
When the mask plate 12 is lowered by a predetermined follow-up amount h, the pressing by the mask pressing mechanism 18 is stopped. The follow-up amount h is determined by conditions such as the size of the printing range of the substrate 8 and the degree of elasticity of the mask plate 12, and an optimum value is obtained based on the trial result.
[0023]
Thereafter, the Z-axis drive mechanism 19 is continuously driven to further separate the substrate 8 from the mask plate 12, whereby the cream solder 17 filled in the pattern hole 12a is detached from the pattern hole 12a and separated from the plate. Next, by raising the mask push-down mechanism 18, the cream solder 17 is detached from the pattern hole 12a as shown in FIG. 3D, and the printing operation on the substrate 8 is completed.
[0024]
In this plate separation process, the mask plate 12 is pressed from the upper surface side at a position corresponding to the peripheral portion of the substrate 8, so that the mask plate 12, the substrate 8, and the like are separated as in the conventional plate separation operation in screen printing. There is no time delay phenomenon at the time of detaching the plate, which is sequentially separated from the peripheral part toward the central part. Thereby, the separation between the upper surface of the substrate 8 and the lower surface of the mask plate 12 is performed at substantially the same timing over the entire surface of the printing range on the substrate 8.
[0025]
That is, the plate separation speed when the cream solder 17 is separated from the pattern holes 12a is kept constant for all the pattern holes 12a, and the plate separation conditions can be made constant. Therefore, unlike the plate separation operation in the conventional screen printing apparatus, there is no variation in print quality due to the difference in the plate separation speed between the central portion and the peripheral portion of the printing range, and stable printing quality can be ensured. it can.
[0026]
Since the plate separation conditions are constant over the entire printing range, the plate separation conditions can be efficiently calculated under fine conditions. For this reason, even when a high-density substrate having a large number of electrodes formed at a narrow pitch and having a high degree of plate separation difficulty is to be printed, uniform and good plate separation properties are ensured over the entire printing range by fine plate separation control. be able to.
[0027]
In the above-described embodiment, the mask plate 12 is pushed down by the mask push-down mechanism 18 provided with the lifting mechanism as the mask follow-up means. However, strict follow-up is not required depending on the type of the mask plate to be used. In some cases, the mask follower may be configured such that the peripheral portion of the mask plate 12 is simply pushed down by the biasing force or weight of the spring. In short, it is sufficient that the separation of the mask plate 12 and the substrate 8 is not started partially from the peripheral portion at the start of the plate separation operation, but the plate separation is performed over the entire printing range. In addition, instead of pressing down from the upper surface of the mask plate 12, the mask plate 12 may be sucked and pulled down from the lower surface side.
[0028]
【The invention's effect】
According to the present invention, at the start of the plate separation operation for relatively separating the workpiece from the mask plate, the mask plate is moved by the contact portion that linearly contacts the position corresponding to the peripheral portion of the workpiece on the upper surface of the mask plate. Since it is pushed down and displaced in the workpiece separation direction to follow the workpiece, the difference in plate separation speed between the peripheral part and the central part of the work is minimized, and the plate separation conditions are made uniform over the entire work surface. And good releasability can be ensured.
[Brief description of the drawings]
FIG. 1 is a perspective view of a screen printing apparatus according to an embodiment of the present invention. FIG. 2 is a partial sectional view of a screen printing apparatus according to an embodiment of the present invention. Process description of printing method 【Explanation of symbols】
2 Substrate positioning unit 7 Substrate holding unit 8 Substrate 10 Screen printing unit 12 Mask plate 12a Pattern hole 13 Squeegee unit 16 Squeegee 17 Cream solder 18 Mask pressing mechanism 19 Z-axis drive mechanism 20 Plate separation control unit

Claims (2)

A screen printing apparatus for mounting a mask plate on which a pattern hole is formed on a work and printing a paste on the work through the pattern hole, the mask mounting means for mounting the mask plate in contact with the upper surface of the work A squeegee that fills the pattern hole with a paste by moving on the mounted mask plate, and a plate separating means for separating the workpiece from the mask plate to perform a plate separating operation; A mask push-down mechanism as a mask follow-up means for displacing the mask plate in the separation direction of the workpiece and following the workpiece at the start of the plate separation operation, and the mask push-down mechanism has both ends of the horizontal movement range of the squeegee unit. A position corresponding to the peripheral part of the workpiece on the upper surface of the mask plate, which is disposed in the vicinity of the part An elongated rod-like member abutting on the linear, screen printing apparatus characterized by comprising a lift mechanism for lifting the elongated bar-like member. A screen printing method for mounting a mask plate on which a pattern hole is formed on a work and printing a paste on the work through the pattern hole, the mask mounting process for mounting the mask plate in contact with the upper surface of the work A squeegeeing step for filling the pattern holes with paste by moving a squeegee on the mounted mask plate, and a plate for separating the workpiece from the mask plate to perform a plate separating operation. Including a separation step, and at the start of the plate separation operation, a mask follow operation is performed in which the mask plate is displaced in the separation direction of the workpiece to follow the workpiece,
The mask following operation corresponds to the peripheral portion of the workpiece on the upper surface of the mask plate by driving a mask pressing mechanism disposed near both ends of the horizontal movement range of the squeegee unit. A screen printing method comprising: bringing a mask plate into contact with a position linearly;

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