JP4246328B2 - Screen printing device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a screen printing apparatus and a screen printing method for screen printing a paste such as cream solder on a substrate.
[0002]
[Prior art]
Conventionally, a substrate set on a printing stage is overlaid on a mask sheet of a screen mask for screen printing, and paste such as cream solder, conductive paste, or resistance paste supplied on the mask sheet is expanded by a squeegee. A screen printing apparatus that prints (applies) a paste to a predetermined position of a substrate through an opening formed in a mask sheet is generally known.
[0003]
In such an apparatus, the squeegee slides on the mask sheet when expanding the paste, and the landing load of the squeegee on the mask sheet at that time (among the landing load, the printing load is particularly “printing pressure”. Must be optimally controlled. This is because if the printing pressure is too strong, the paste oozes out from the opening, and if it is too weak, insufficient application occurs.
[0004]
Therefore, proposals for optimally controlling the printing pressure of the squeegee have been made.
[0005]
Conventionally, the squeegee printing pressure is applied by an air cylinder, and the magnitude of the load is controlled by an electropneumatic regulator. However, in that case, since the responsiveness is low, the ultra-low printing pressure control requested in recent years cannot be performed. Therefore, a mechanism has also been proposed in which a plurality of urging members are combined to land a squeegee on the mask sheet, and the squeegee printing pressure determined by the resultant force of the urging member is adjusted by changing the length of the urging member. (See JP-A-11-010831).
[0006]
In that configuration, a squeegee holder carrying a squeegee and a lift connected to the squeegee via an elastic member are provided, and a lift drive mechanism using a ball screw is provided on the lift so that the squeegee can be raised and lowered. In addition, an elastic load control means is provided between the squeegee holder and the elevator.
[0007]
[Problems to be solved by the invention]
However, in the above configuration, since the drive mechanism (motor) for raising and lowering the squeegee is configured to move up and down integrally with the elevator, there is a problem that the entire mechanism becomes large. In addition, since the elevator is merely connected via an elastic member, there is a problem that it lacks agility when raising the squeegee.
[0008]
The present invention has been made in view of the above-described problems, and provides a screen printing apparatus and a screen printing method capable of performing high-precision adjustment of printing pressure, and capable of performing simple and quick squeegee lifting and lowering operations. The issue is to provide.
[0009]
[Means for Solving the Problems]
The present invention is capable of moving up and down over a predetermined range in a screen printing apparatus having a squeegee that performs screen printing on a substrate stacked on the lower surface of a mask sheet by expanding the paste supplied on the mask sheet. A lifting / lowering device, a lifting / lowering driving means for moving the lifting / lowering member up and down, and a biasing member provided between the lifting / lowering device and the squeegee for elastically applying a landing load on the mask sheet of the squeegee And a connecting means for connecting the elevator and the squeegee so that the squeegee can be directly driven up and down within a predetermined first stroke range in which the squeegee floats from the mask sheet. In the second stroke range below the first stroke range, the squeegee is masked with a landing load corresponding to the height position of the elevator. A screen printing device being characterized in that a possible landing on over and.
[0010]
In this invention, since the raising / lowering drive means which raises / lowers the raising / lowering element is employ | adopted, the raising / lowering drive of a squeegee can be performed with a very simple structure. In addition, since the squeegee is connected to the squeegee so that the squeegee can be directly driven up and down within a predetermined first stroke range in which the squeegee floats from the mask sheet, the squeegee is connected within the first stroke range. When the squeegee is moved up and down, the squeegee can be driven up and down in a state of being integrally connected to the lift, so that the squeegee can be moved up and down quickly and reliably. Further, in the second stroke range below the first stroke range, the squeegee can be landed on the mask sheet with the landing load corresponding to the height position of the lift, so that the lift of the lift is within this second stroke range. It becomes possible to adjust the urging force of the urging member only by adjusting the height position.
[0011]
In particular, the elevating drive means can be driven to rotate the ball screw bidirectionally at a fixed position so as to elevate the elevating element and a ball screw arranged along a vertical line and screwing the elevating element It is preferable to have a motor (claim 2).
[0012]
In this way, when the motor rotates and drives the ball screw at a fixed position, the elevator that is screwed to the ball screw moves up and down, so that the elevator can be moved with a relatively small force compared to the structure in which the motor itself moves up and down. As a result of being able to move up and down, a small motor can be adopted, and the size of the lift itself can be reduced.
[0013]
Further, it is preferable that a cancel urging member for urging the squeegee in a direction to separate the squeegee from the mask sheet is provided.
[0014]
In this way, the urging force (or the squeegee's own weight) by the urging member can be canceled by the canceling urging member, and the printing pressure can be adjusted in a lower region.
[0015]
Furthermore, a squeegee holder for carrying the squeegee is provided, and the urging member and the urging member for cancellation are each constituted by a compression coil spring disposed with the squeegee holder interposed therebetween (Claim 4). preferable.
[0016]
If it does in this way, since a coil spring can be arrange | positioned in the raising / lowering range of a squeegee holder, it becomes possible to comprise a comparatively compact layout.
[0019]
In any invention ,in front And a lock means for fixing the squeegee on the mask sheet. 5 ) Is preferred.
[0020]
If it does in this way, a squeegee will be fixed in the state which contacted the mask sheet | seat by the locking means. Therefore, for example, in the peeling process of peeling the substrate from the mask sheet, when the substrate is peeled from the mask sheet by operating the locking means in advance and fixing the squeegee in the predetermined state, the deflection or vibration of the mask sheet. Can be suppressed. In addition, the effect of the paste remaining between the squeegee and the mask sheet is no longer affected by this peeling step, and the mask sheet is lifted when the squeegee is pulled away from the mask sheet, and the finish of the substrate is not adversely affected. .
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described with reference to the drawings.
[0024]
FIG. 1 is an exploded perspective view showing a main part of the present invention, and FIG. 2 is a schematic side view of the screen printing apparatus of FIG. First, referring to FIG. 2, on the base 2 of the screen printing apparatus 1, a carry-in conveyor 2 a and a carry-out conveyor 2 b for carrying in and carrying out the printed board W are sandwiched by a print stage 3 to be described in detail later. It is arrange | positioned at both sides (the left-right direction of FIG. 2, "X-axis direction" in this embodiment). Above the printing stage 3, a sheet holding unit 53 for stretching a mask sheet 51 of a screen mask 50 that is superimposed on the printed circuit board W, as in a known apparatus, and above the held mask sheet 51. And a pair of squeegees 61 and 62 of the squeegee unit 60 with respect to the printed circuit board W superimposed on the mask sheet 51 by the printing stage 3 as will be described later. Screen printing.
[0025]
The printing stage 3 includes a fixed table 4 installed at a fixed position on the base 2 and a left-right direction of FIG. 1 (this embodiment) with respect to the fixed table 4 via a pair of rails 5 and a ball screw unit 15. Y-axis table 6 that is relatively displaceable in the “Y-axis direction”), and an X-axis table 8 that is relatively displaceable in the X-axis direction with respect to the Y-axis table 6 via a pair of rails 7 and a ball screw unit 17; An R-axis table 10 that is rotatable about a vertical line (in this embodiment, “Z-axis direction”) via a rotation unit 9 provided on the X-axis table 8, and a ball against the R-axis table 10. A lifting table 12 that can be moved up and down relatively via a screw unit 11 is included. A clamp unit 20 is attached to the lifting table 12. The ball screw units 11, 15, 17 and the rotation unit 9 are each driven by a servo motor.
[0026]
The clamp unit 20 has a pair of clamp pieces 24a and 24b. Each of the clamp pieces 24a and 24b is a substantially plate-like member extending in the X-axis direction. One of the clamp pieces 24a and 24b is moved to the movable side by a belt drive mechanism (not shown) and is carried in from the carry-in conveyor 2a in cooperation with the other on the fixed side. The clamp 24 that sandwiches the printed board W is configured.
[0027]
A pin unit 25 is provided between the clamp pieces 24a and 24b. Although not shown, the pin unit 25 is configured to be movable up and down relatively with respect to the clamp pieces 24a and 24b. Thus, when the printed board W is carried in between the clamp pieces 24a and 24b from the carry-in conveyor 2a, the lower surface thereof is received by the pin 25a of the pin unit 25, and the printed board W is temporarily placed, and a press (not shown) The printed circuit board W is temporarily held in cooperation with the means and can be transferred to the clamp 24.
[0028]
When the printed circuit board W is delivered to the clamp 24, the lifting table 12 of the printing stage 3 is raised, and the printed circuit board W is overlaid on the lower surface of the mask sheet 51 of the screen mask 50. A paste such as cream solder is applied to the superimposed printed circuit board W by a squeegee unit 60 described below.
[0029]
The squeegee unit 60 is located above the base 2 and is attached to a horizontal frame 2c that is horizontally mounted in the X-axis direction. The horizontal frame 2c is configured to be movable in the Y-axis direction by a pair of rails, and is reciprocated in the Y direction by a ball screw mechanism (not shown). As a result, the squeegees 61 and 62 can be reciprocated on the screen mask 50.
[0030]
Referring to FIG. 1, the squeegee unit 60 includes a squeegee holder 63 that supports the squeegees 61 and 62, and an elevating unit 64 (elevating drive means) that elevates and lowers the squeegees 61 and 62 via the squeegee holder 63. The body frame 65 of the elevating unit 64 is fixed to the horizontal frame 2c (see FIG. 2).
[0031]
3A and 3B are schematic cross-sectional views schematically showing the main part of the squeegee unit 60. FIG. 3A is a state where the squeegee is lowered to the mask sheet 51, and FIG. 3B is a state where the squeegee is raised from the mask sheet 51. Each state is shown.
[0032]
The squeegees 61 and 62 are inclined so as to form an acute angle toward the carry-in conveyor 2a and the forward squeegee 61 whose inclination angle is set so as to form an acute angle with the mask sheet 51 toward the carry-out conveyor 2b. It is opposite to the Y axis direction in a pair with the backward squeegee 62 having an angle set. These squeegees 61 and 62 are made of relatively hard urethane or special metal.
[0033]
The squeegees 61 and 62 are attached to rod ends (lower ends) of air cylinders 61a and 62a fixed to the squeegee holder 63, respectively, and the air cylinders 61a and 62a are individually moved up and down with respect to the squeegee holder 63. Supported as possible. The strokes of the air cylinders 61a and 62a are set so that the squeegees 61 and 62 can be landed on the mask sheet 51 when extended to the bottom dead center. If the strokes of the air cylinders 61a and 62b can be adjusted, it is possible to configure an adjusting means for adjusting the urging force of the compression spring 71 and the cancellation compression springs 89 and 90 described later. In FIG. 1, 61e and 62e are guide rods that make a pair for each air cylinder 61a and 62a.
[0034]
On the other hand, the elevating unit 64 is for adjusting the landing load of the squeegees 61 and 62 by moving the entire squeegee holder 63 up and down, and contributes to the adjustment of the printing pressure of the squeegees 61 and 62 during printing. . The frame 65 of the elevating unit 64 has a servo motor 66, a timing belt 67 coupled to the servo motor 66, a ball screw 68 that is rotationally driven via the timing belt 67, and an elevator coupled to the ball screw 68. 69 is included. Each of the servo motor 66 and the ball screw 68 has a vertical axis, and when the servo motor 66 rotationally drives the ball screw 68, the elevator 69 moves up and down.
[0035]
A spring holder 70 is fixed to the illustrated lift 69. The spring holder 70 is for holding the upper end portion of the compression spring 71 that urges the squeegee holder 63 in the direction of pushing down. On the other hand, a spring holder 72 that holds the lower end portion of the compression spring 71 is fixed to the back surface of the squeegee holder 63. By inserting the compression spring 71 between the holders 70 and 72 during assembly, the elevator The lifting driving force 69 is elastically transmitted to the squeegees 61 and 62 through the squeegee holder 63. In the illustrated embodiment, a pressure receiving plate 63 a (connecting means) is provided on the back surface of the squeegee holder 63. The pressure receiving plate 63a faces above the spring holder 72 in the vertical direction. As shown in FIG. 3A, within the range of the squeegee up / down stroke ST2 that has passed the switching position P after the elevating element 69 has moved up and passed through a certain spring pressurization stroke ST1, the spring holder 70 is the pressure receiving plate. The squeegees 61 and 62 are directly moved up and down through the squeegee holder 63 in contact with the lower surface of 63a. In the illustrated embodiment, the elevator 69 is guided up and down by a rail 69a, and the upper limit of the elevator 69 is defined by a stopper 69b provided at the upper end of the guide rail 69a (see FIG. (See FIG. 1).
[0036]
A pair of guide rails 83, 84 are provided in parallel along the vertical direction on both sides of the ball screw 68, and the sliders 83 a, 84 a of each guide rail 83, 84 are fixed to the back surface of the squeegee holder 63, The power of the elevator 69 can be smoothly transmitted to the squeegee holder 63. Further, a pair of spring seats 85, 86 arranged at the lower end of the frame 65 protrude from both outer sides of the guide rails 83, 84. The spring seats 85 and 86 are for supporting the lower ends of the compression springs 89 and 90 for cancellation interposed between a pair of spring holders 87 and 88 fixed to both sides of the squeegee holder 63. The squeegee holder 63 is urged upward by the cancellation compression springs 89 and 90, and the load due to the weight of the squeegee holder 63 and the members assembled thereto is canceled. As a result, the squeegee holder 63 elastically lands the squeegees 61 and 62 on the mask sheet 51 by the urging force of the compression spring 71.
[0037]
As shown in FIG. 3, in order to detect the landing load of the squeegees 61 and 62, load cells 61c and 62c (load detecting means) are attached to the rods 61b and 62b of the air cylinders 61a and 62a. The load (or printing pressure) when 61 and 62 land on the mask sheet 51 can be detected individually.
[0038]
FIG. 4 is a block diagram showing a control configuration for controlling the servo motor 66.
[0039]
As shown in the figure, the control unit 80 for controlling the servo motor 66 is provided with a memory 81 for storing the landing load set value, and the input values of the load cells 61 c and 62 c input to the work area of the control unit 80. And the landing load set value can be compared.
Then, regarding the squeegee 61 (62) in operation, when the landing load (input value of the load cell) is larger than the landing load set value, the lift 69 is raised to lower the landing load. Are set so as to raise the landing load by lowering the lift 69. The set value stored in the memory 81 stores a plurality of printing pressures according to the type of the printed circuit board W to be printed.
[0040]
Further, the squeegee unit 60 is provided with a lock unit 100 as a lock means for fixing the squeegees 61 and 62 in the peeling step after printing. The lock unit 100 includes an elevating rod 102 erected on a bracket 101 fixed to the back surface of the squeegee holder 63 and an air brake 103 that can lock the elevating rod 102. The positions of the squeegees 61 and 62 can be kept constant by fixing the squeegees 61 and 62 via the squeegee holder 63 within a stroke range elastically connected to the elevating unit 64.
[0041]
FIG. 5 is a diagram showing a printing process of the screen printing apparatus 1 according to the embodiment of FIG.
[0042]
First, referring to FIG. 2 and FIG. 5, in the above configuration, when the printed board W is loaded from the carry-in conveyor 2 a as in the conventional configuration, the printed board W is moved by the clamp 24 of the printing stage 3. Clamped. Next, the printing stage 3 conveys the printed circuit board W below the mask sheet 51, raises the lifting table 12 of the printing stage 3, and overlaps the printed circuit board W on the lower surface of the mask sheet 51 (FIG. 5A). reference).
[0043]
When the printed circuit board W is stacked on the mask sheet 51, a predetermined amount of paste is supplied onto the mask sheet 51 by a paste supply nozzle or the like (not shown), and the elevating unit 64 of the squeegee unit 60 lowers the squeegee holder 63. And is reciprocated along the X-axis direction. At this time, the forward moving air cylinder 61a and the backward moving air cylinder 62a are selectively extended corresponding to the reciprocating motion of the squeegee holder 63, and the squeegees 61 and 62 are slid on the mask sheet 51 to slide. Thus, the paste on the mask sheet 51 is expanded and a printing operation is performed (see FIG. 5B).
[0044]
FIG. 6 is a flowchart according to the embodiment of the present invention.
[0045]
As shown in the figure, in step S1, the control unit 80 reads the load setting value of the squeegee 61 (or 62) at the time of printing. In step S2, the controller 80 lands from the load cell 61c (62c) of the corresponding squeegee 61 (62). Read the load (printing pressure). Then, the set value is compared with the value of the load cell 61c (62c), and if they match, the printing is continued as it is, and the squeegee 61 (62) is masked until the printing is completed (step S4). 51 slides on. On the other hand, if the set value and the value of the load cell 61c (62c) do not match, in step S5 to step S7, adjustment of pressurization or depressurization is performed by the control of the servo motor 66, and the process returns to step S2 to be appropriate. The above steps are repeated until a printing pressure is obtained.
[0046]
The printing pressure of the squeegees 61 and 62 at the time of printing is performed with a load set according to the type of the printed circuit board W. In the illustrated embodiment, since the load due to the weight of the squeegee holder 63 and the like is canceled by the canceling compression springs 89 and 90, it is possible to cope with ultra-low printing pressure control.
[0047]
When this printing process is completed, a peeling process for peeling the printed board W from the mask sheet 51 is performed by lowering the lifting table 12 (see FIG. 1) of the printing stage 3 again.
[0048]
In this peeling process, the squeegees 61 and 62 are locked by the lock unit 100.
[0049]
When the squeegee holder 63 is locked, the lifting table 12 of the printing stage 3 is lowered and the printed board W is peeled off. At this time, the load by the compression spring 71 is received by the lock unit 100, the landing load on the mask sheet 51 becomes 0, and the mask sheet 51 does not bend by the landing load. Further, due to the viscosity of the paste adhered to the mask sheet 51, the mask sheet 51 may bend downward following the printed circuit board W. The reaction force is in contact with the mask sheet 51 with a slight load. The squeegee 61 elastically absorbs the vibration of the mask sheet 51 as much as possible. As a result, it is possible to obtain a good printed surface without deteriorating the printing characteristics of the paste applied to the printed circuit board W.
[0050]
As described above, in the above-described embodiment, during printing, the squeegees 61 and 62 are pressed against the mask sheet 51 with an appropriate landing load (printing pressure) by the compression spring 71 and the lift 69 as pressing means. After printing, the squeegees 61 and 62 are fixed in a predetermined state by the lock unit 100 as a lock unit, so that the deflection and vibration of the mask sheet 51 can be prevented when the printed circuit board W is peeled from the mask sheet 51. .
[0051]
In particular, the compression spring 71 is interposed between the elevating unit 64 and the squeegee holder 63 and urges the squeegees 61 and 62 to the mask sheet 51, and the urging force of the compression spring 71 is adjusted. Therefore, when the adjusting member (servo motor 66 or the like) for adjusting the landing load of the squeegees 61 and 62 is provided, the squeegees 61 and 62 are elastically biased to the mask sheet 51 by the compression spring 71. In addition, since the biasing force of the compression spring 71 is adjusted by the adjustment member, the mask sheet 51 can be biased with a predetermined spring load, and it is counteracted when the printed circuit board W is uneven. Force passive can be absorbed elastically.
[0052]
Further, since the springs 89 and 90 are provided as canceling biasing members, the weights of the squeegee holder 63 and the squeegees 61 and 62 attached thereto are canceled by the canceling compression springs 89 and 90, and the lower region As a result, the desired landing load can be obtained, and there is an advantage that the ultra low printing pressure control and the landing load control in the peeling process can be precisely performed.
[0053]
Further, connecting members (spring holder 70, pressure receiving plate 63a) are provided on the squeegee holder 63 and the lifting unit 64, respectively, so that the lifting drive force by the lifting unit 64 is directly transmitted to the squeegee holder 63 with a predetermined stroke. Therefore, there is an advantage that the squeegees 61 and 62 can be driven with quick and highly reproducible characteristics.
[0054]
The above-described embodiments are merely examples of preferred specific examples of the present invention, and the present invention is not limited to the above-described embodiments.
[0055]
For example, an air cushion cylinder or the like can be used instead of the springs 71, 89, 90 described above.
[0056]
It goes without saying that various modifications can be made within the scope of the claims of the present invention.
[0057]
【The invention's effect】
As described above, according to the present invention, the printing pressure can be adjusted with high accuracy, and the squeegee can be lifted and lowered easily and quickly.
[0058]
In particular, the squeegee is applied to the mask sheet with a predetermined spring load during printing by including an urging member for urging the squeegee against the mask sheet, and an elevator and an elevating drive means capable of adjusting the urging force of the urging member. While being able to press, the force transmitted to the mask sheet can be absorbed elastically.
[0059]
Furthermore, since the squeegee is directly raised and lowered within the predetermined first stroke range by the raising / lowering driving means, there is an advantage that the squeegee can be raised and lowered with quick and highly reproducible characteristics.
[0060]
Further, when the canceling biasing member is provided, the weight of the squeegee or the like can be canceled by the canceling biasing member, and the printing pressure can be adjusted in a lower region, so that a desired landing load can be obtained. Thus, there is an advantage that the ultra-low printing pressure control and the landing load control in the peeling process can be precisely performed.
[0061]
Also, during printing, the squeegee is pressed against the mask sheet with an appropriate landing load (printing pressure) by the pressing means, and after printing, the squeegee is fixed in a predetermined state by the locking means, so that the substrate is peeled off from the mask sheet. It is possible to prevent the mask sheet from being bent or vibrated.
[0062]
Further, when the printing pressure of the squeegee is adjusted by feedback control, there is an advantage that the printing adjustment can be performed with high accuracy.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view showing a main part of the present invention.
FIG. 2 is a schematic side view of the screen printing apparatus of FIG. 1;
FIG. 3 is a schematic cross-sectional view schematically showing the main part of the squeegee unit, where (A) shows a state where the squeegee is lowered to the mask sheet, and (B) shows a state where the squeegee is raised from the mask sheet. Each is shown.
FIG. 4 is a block diagram showing a control configuration for controlling a servo motor.
FIG. 5 is a diagram illustrating a printing process of the screen printing apparatus according to the embodiment of FIG. 1;
FIG. 6 is a flowchart showing a procedure when the screen printing apparatus according to the embodiment of FIG. 1 is locked.
[Explanation of symbols]
1 Screen printer
3 Printing stage
51 Mask sheet
60 squeegee units
61c, 62c Load cell
61, 62 Reverse squeegee
63 Squeegee holder
64 Lifting unit
66 Servo motor
69 Elevator (Adjustment member)
71 Compression spring (biasing member)
89, 90 Compression spring for cancellation
100 Brake unit (locking means)
103 Air brake
W Printed circuit board

Claims (5)

  In a screen printing apparatus provided with a squeegee for performing screen printing by expanding the paste supplied on the mask sheet to a substrate stacked on the lower surface of the mask sheet, a lift that can be moved up and down over a predetermined range; Elevating drive means for elevating the elevating element up and down, an urging member provided between the elevating element and the squeegee to elastically apply a landing load on the mask sheet of the squeegee, and the squeegee The elevator includes a connecting means for connecting the elevator and the squeegee so that the squeegee can be directly driven up and down within a predetermined first stroke range levitating from the mask sheet, and the first of the elevator drive ranges by the elevator drive means. In the second stroke range below the stroke range, the squeegee is placed on the mask sheet with a landing load according to the height position of the elevator. Screen printing apparatus being characterized in that to allow the earth.   The elevating drive means includes a ball screw disposed along a vertical line and screwing the elevating element, and a motor capable of rotating the ball screw bidirectionally at a fixed position to elevate and lower the elevating element. The screen printing apparatus according to claim 1, further comprising:   The screen printing apparatus according to claim 1, further comprising a canceling biasing member that biases the squeegee in a direction in which the squeegee is pulled away from the mask sheet.   4. A squeegee holder for carrying the squeegee is provided, and the urging member and the urging member for cancellation are each constituted by a compression coil spring disposed with the squeegee holder interposed therebetween. Screen printing equipment.   The screen printing apparatus according to claim 1, further comprising a lock unit that fixes the squeegee on the mask sheet.

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