JP2005161783A - Screen printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a screen printer capable of improving reliability to printing quality by enabling stabilization of a paste filled amount. <P>SOLUTION: In the screen printer, a rolling image picking up camera 15 for picking up a rolling state of a paste 17 to a front side in a transfer direction of a squeegee 9 upside a metal mask 10, an image analyzer (a rolling speed calculation means) 25 for calculating a rolling speed q of the paste 17 by analyzing the picked up image, and a control unit (a squeegee speed control means) 12 for controlling a squeegee speed of the squeegee 9 based on the calculated rolling speed q are provided. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a screen printing apparatus that prints on a substrate by moving a paste supplied on a screen mask in one direction with a squeegee.

For example, when surface mounting electronic components, it is common to employ a printed circuit board on which a solder paste or a conductive adhesive is screen-printed. In order to print the solder paste on this printed circuit board, a screen mask having a printing opening is arranged on the printed circuit board, both are positioned, the solder paste is supplied to the upper surface of the screen mask, and the squeegee is moved in one direction. Thus, the solder paste is printed on the printed circuit board through the printing opening of the screen mask (for example, see Patent Document 1).

In such a screen printing apparatus, the printed material is stabilized by managing the rolling diameter of the solder paste using a squeegee speed or a laser sensor.
JP 2001-293842 A

However, the conventional method for managing the squeegee speed and the rolling diameter has a problem that the paste filling amount filled in the printing opening tends to vary, and the reliability with respect to the printing quality is low, and improvement in this respect is requested. Has been.

The present invention has been made in view of the above situation, and an object of the present invention is to provide a screen printing apparatus capable of stabilizing the paste filling amount and improving the reliability of print quality.

In order to meet the above-mentioned demand, the present inventors have observed the behavior of the paste during printing. As a result, it has been found that the amount of printing varies depending on the rolling state of the paste. From this observation result, the present inventors have found that the paste filling amount can be stabilized by directly managing the rolling state of the paste.

Accordingly, the invention according to claim 1 arranges a screen mask having a printing opening formed on the upper surface of the substrate, and moves the paste supplied on the screen mask in one direction with a squeegee to remove the paste from the screen mask. In a screen printing apparatus that fills the printing openings and prints on the substrate, a rolling imaging camera that images the rolling state of the paste above the screen mask and on the front side in the moving direction of the squeegee, and A rolling speed calculation unit that analyzes a captured image to calculate a rolling speed of the paste, and a squeegee speed control unit that controls the squeegee speed of the squeegee based on the calculated rolling speed. It is said.

The invention of claim 2 is characterized in that, in claim 1, the squeegee speed control means is configured to lower the squeegee speed when the calculated rolling speed is higher than a predetermined value.

The invention of claim 3 is characterized in that, in claim 1 or 2, the squeegee speed control means is configured to increase the squeegee speed when the calculated rolling speed is lower than a predetermined value.

According to a fourth aspect of the present invention, in any one of the first to third aspects, the squeegee speed control means is configured to supply a predetermined amount of paste to the screen mask when the calculated rolling speed is lower than a predetermined value. It is characterized by being.

The invention of claim 5 is characterized in that, in claim 1, the squeegee speed control means is configured to output an alarm signal when the calculated rolling speed is higher or lower than a predetermined value. .

According to a sixth aspect of the present invention, in any one of the first to fifth aspects of the present invention, a printing process for imaging a filling process of a paste filled in a printing opening of the screen mask below the printed material through the printed material. A process imaging camera is provided.

According to a seventh aspect of the present invention, in any one of the first to sixth aspects, a plate separation imaging camera for imaging a plate separation state of the screen mask is disposed above the screen mask. .

According to the screen printing apparatus of the first aspect of the invention, the squeegee speed is controlled based on the rolling speed of the paste obtained by imaging the rolling state of the paste with a camera and analyzing the captured image. Therefore, for example, as in the second and third aspects of the invention, the rolling speed of the paste is reduced by decreasing the squeegee speed when the rolling speed is higher than a predetermined value and increasing the squeegee speed when the rolling speed is lower than the predetermined value. Can be kept constant, and the filling amount of the paste can be stabilized. As a result, the reliability with respect to the print quality can be improved and the above-mentioned request can be met.

In the invention of claim 4, since the paste is replenished when the rolling speed is lower than the predetermined value, that is, it is possible to judge the remaining amount of paste on the screen mask from the rolling speed, and the replenishment of the paste is possible. Automatic operation enables continuous operation.

According to the fifth aspect of the invention, an alarm is issued when the rolling speed is outside the predetermined value, so that the operator can set the squeegee speed or check the remaining amount of paste by this alarm, and the paste filling amount varies. Can be prevented in advance.

In the invention of claim 6, since the filling process of the paste filling the printing opening of the screen mask is imaged by the camera, the filling state of the paste during printing can be directly monitored, and the quality control is accurately performed. Can be done.

According to the seventh aspect of the present invention, since the screen-release state of the screen mask is imaged by the camera, the adhesion state of the paste to the substrate is managed by directly monitoring the screen-mask release state at the end of printing. And quality control can be performed accurately.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is an overall configuration diagram for explaining a screen printing apparatus according to an embodiment (first embodiment) of the present invention.

The screen printing apparatus 1 according to the present embodiment is for printing, for example, solder for mounting electronic components on a printed circuit board, and includes a box-shaped printing stand 2 that opens upward, and a bottom of the printing stand 2. A printing table driving unit 3 having a pulse motor 3a connected to the wall 2a and driving the printing table 2 to move up and down, a screen support frame 4 disposed in the opening 2b of the printing table 2, and the screen support A squeegee head 5 disposed above the frame 4 and a squeegee driving unit 6 for reciprocatingly driving the squeegee head 5 are provided. The raising / lowering speed of the printing stand 2 can be varied in the range of 0.01 mm / s to 100 mm / s.

The squeegee driving unit 6 is formed by fitting a nut 6c to a ball screw 6b that is rotationally driven by a servo motor 6a. The squeegee speed is controlled by controlling the rotation speed of the ball screw 6b, and the squeegee movement amount is controlled by controlling the rotation amount and rotation angle of the ball screw 6b. The squeegee speed can be varied in the range of 1 mm / s to 80 mm / s.

The squeegee head 5 has a structure in which a squeegee holder 8 is fixed to a lower end of a pneumatic cylinder 7 supported by the nut 6c so as to be movable up and down, and the squeegee 9 is held by the squeegee holder 8 so that the angle can be adjusted. A squeegee pressure of a squeegee 9 to a metal mask 10 to be described later can be adjusted by the pneumatic cylinder 7. The squeegee 9 is made of, for example, urethane rubber having a hardness of 80, and is variable with respect to the metal mask 10 within an inclination angle range of 30 to 90 degrees. Note that v indicates the moving direction (printing direction) of the squeegee 9.

A transparent glass substrate (substrate) 11 is disposed on the screen support frame 4, and the glass substrate 11 is positioned and fixed to the screen support frame 4 by vacuum suction using a vacuum suction mechanism (not shown). The glass substrate 11 is automatically carried in and out by a carrying device (not shown).

The metal mask 10 is disposed on the upper surface of the glass substrate 11 of the screen support frame 4, and the metal mask 10 has a printing opening 10 a having a predetermined size and shape. The metal mask 10 is positioned and fixed to the screen support frame 4 via a clamper (not shown), and is aligned with the glass substrate 11.

The screen printing apparatus 1 images a first camera 15 that captures the rolling state of the solder paste 17 that moves on the metal mask 10, and a process that fills the printing process of the solder paste 17 into the printing opening 10 a of the metal mask 10. 2 camera 14 and a third camera 16 for imaging the state of separation of the metal mask 10.

The first camera 15 is disposed above the metal mask 10 and on the front side in the moving direction v of the squeegee 9 and is connected to the first monitor 19. The second camera 14 is disposed below the glass substrate 11 on the bottom wall 2 a in the printing stand 2 and is connected to the second monitor 18. The third camera 16 is disposed above the metal mask 10 and behind the squeegee 9 and is connected to the third monitor 20. The first and third cameras 15 and 16 are attached to a support arm 21 attached to the squeegee head 5 so as to move together with the squeegee 9. The first camera 15 captures the entire or part of the paste filling area of the glass substrate 11, and the third camera 16 pastes the metal mask 10 when the squeegee 9 moves to the printing end position. The entire filling area is imaged. As each of the cameras 14 to 16, commercially available cameras such as XC-75 manufactured by Sony Corporation or FASTCAM-PCI manufactured by Photoron Corporation are employed. Here, the third camera is attached to a support arm attached to the squeegee head so as to move together with the squeegee. However, since the third camera is for confirming separation of the plate, a screen mask is used. What is necessary is just to be arrange | positioned above. That is, it may not be attached to the squeegee head and may be fixed.

Each of the monitors 18 to 20 is connected to recording / storing means 22 for recording and storing images taken by the cameras 14 to 16. The record storage means 22 is a general video recorder or personal computer. For example, when the FASTCAM-PCI camera is used, an image can be captured by a personal computer at a frame rate of less than 1 millisecond.

A dispenser 23 for supplying a solder paste 17 to the metal mask 10 is disposed above the metal mask 10, and the paste supply port 23 a of the dispenser 23 is positioned between the squeegee 9 and the metal mask 10. doing. The dispenser 23 moves with the squeegee 9. A paste supply drive unit 24 is connected to the dispenser 23, and the paste supply drive unit 24 supplies the solder paste 17 to the front portion of the squeegee 9 in the moving direction.

The first camera 15 is connected to an image analysis device 25 as a rolling speed calculation means. The image analysis device 25 is configured to analyze the rolling state of the solder paste 17 imaged by the first camera 15 based on the image and calculate the rolling speed of the solder paste 17.

Here, as shown in FIG. 2, the rolling speed refers to the moving speed q of the surface of the solder paste 17 that rolls in the moving direction as the squeegee 9 moves. The rolling speed q is substantially proportional to the squeegee speed and the rolling diameter, and the filling amount of the solder paste 17 changes depending on the rolling speed q. The rolling diameter refers to the distance r from the contact point between the squeegee 9 and the metal mask 10 to the outer peripheral surface of the solder paste 17.

The screen printing apparatus 1 includes a control unit 12 as squeegee speed control means for driving and controlling the printing table driving unit 3, the squeegee driving unit 6 and the paste supply driving unit 24. The control unit 12 is configured to control the squeegee speed based on the rolling speed calculated by the image analysis device 25. Specifically, the rolling speed is in a range of 18 ± 2 mm / s as a predetermined value. The squeegee speed is controlled to be inside. Specifically, when the rolling speed is higher than the predetermined value, the squeegee speed is decreased, and when the rolling speed is lower than the predetermined value, the predetermined value is maintained by increasing the squeegee speed.

Further, the control unit 12 drives the paste supply drive unit 24 when the rolling speed is lower than a predetermined value and the rolling speed does not increase even if the set value of the squeegee speed is increased, and a predetermined amount of solder is applied to the metal mask 10. It is configured to replenish the paste.

Here, the area where the squeegee speed is adjusted based on the rolling speed is set between the printing start position where the squeegee 9 abuts the metal mask 10 and the printing area where the printing opening 10a of the metal mask 10 is formed. . By doing so, waste of the glass substrate can be eliminated.

Next, the operation of the screen printing apparatus 1 will be described with reference to the flowchart of FIG.

As the operation starts, the glass substrate 11 is conveyed to the screen support frame 4, the glass substrate 11 and the metal mask 10 are aligned, and the both 10 and 11 are brought into close contact with each other (steps S <b> 1 to S <b> 3). The squeegee 9 descends and comes into contact with the printing start position of the metal mask 10 with a predetermined squeegee pressure, and a predetermined amount of solder paste 17 is supplied (step S4).

Next, the squeegee 9 starts to move. At the same time, the rolling state of the solder paste 17 is imaged by the first camera 15 and the rolling speed is calculated by analyzing the image of the paste 17, and the rolling speed is within a predetermined value range. It is determined whether it is within (steps S5 to S8).

If the rolling speed is within a predetermined value, the printing is continued by moving the squeegee 9 as it is, and stops when the squeegee 9 moves to the printing end position, and then the metal mask 10 is separated from the glass substrate 11 (step). S9 to S11). Thereafter, the squeegee 9 rises and returns to the original print start position, and the glass substrate 11 is carried out (steps S12 and S13). In this way, a predetermined pattern is printed on the glass substrate 11.

In step S8, when the rolling speed is higher than a predetermined value, the squeegee speed is lowered (step S14). Thereafter, the process returns to step S5.

On the other hand, in step 8, when the rolling speed is lower than a predetermined value, the squeegee speed is increased. In this case, the squeegee speed is selected from the built-in library, or the speed command value is changed in a predetermined step, and the squeegee speed is changed based on the speed command value (steps S15 to S17). Subsequently, while imaging the rolling state of the solder paste 17, the image of the paste 17 is analyzed to calculate the rolling speed, and it is determined whether or not the rolling speed increases as instructed (steps S18 to S20). . When the rolling speed is increasing, the process returns to step S5.

When the rolling speed is not increased, it is determined that the remaining amount of solder paste is low, and the paste supply drive unit 24 is driven to replenish a predetermined amount of solder paste (steps S21 to S23). Thereafter, the process returns to step S5.

As described above, according to the present embodiment, the rolling state of the solder paste 17 is captured by the first camera 15, the captured image is analyzed to calculate the rolling speed of the solder paste 17, and based on the rolling speed. Since the squeegee speed of the squeegee 9 is controlled, the squeegee speed is decreased when the calculated rolling speed is higher than a predetermined value (18 ± 2 mm / s), and the squeegee speed is increased when the rolling speed is lower than the predetermined value. Thus, the rolling speed of the solder paste 17 can be kept constant, and the paste filling amount can be stabilized. As a result, the reliability with respect to the print quality can be improved.

Further, since the solder paste 17 is replenished when the rolling speed is lower than the predetermined value, the remaining state of the solder paste 17 on the metal mask 10 can be determined from the rolling speed, and the refill of the solder paste 17 can be performed. It can be performed automatically and continuous operation is possible.

In the present embodiment, since the filling process of the solder paste 17 filling the printing opening 10a of the metal mask 10 is imaged by the second camera 14, the solder paste 17 filling the glass substrate 11 during printing is performed. The state can be directly monitored, and quality control can be performed with high accuracy.

In the present embodiment, since the image separation state of the metal mask 10 is imaged by the third camera 16, the glass substrate of the solder paste 17 is directly monitored by directly monitoring the image separation state of the metal mask 10 at the end of printing. 11 can be managed, and quality control can be performed with high accuracy.

FIG. 4 is a flowchart for explaining a screen printing apparatus according to one embodiment (second embodiment) of claim 5. In the figure, steps S1 to S13 indicate the same operations as steps S1 to S13 of FIG.

In the present embodiment, in step S8, it is determined whether or not the solder paste rolling speed is within a predetermined value range. When the rolling speed is higher or lower than the predetermined value, an alarm is issued and the printing apparatus is stopped (step S24). ).

Then, the operator confirms the rolling speed, and when the rolling speed is lower than a predetermined value, the rolling diameter of the solder paste is measured, and when the rolling diameter is not more than a set value (for example, 20 mm), the solder paste is replenished (steps S25 to S27). ). Thereafter, the screen printing apparatus is restarted (step S28). Thereby, it returns to step S5 and automatic driving | operation is restarted.

On the other hand, when the rolling speed is higher than the predetermined value in step S25, the operator decreases the set value of the squeegee speed (step S29). Thereafter, the screen printing apparatus is restarted, and the process returns to step S5 to resume the automatic operation.

In the above embodiment, when the rolling speed is other than the predetermined value, an alarm is issued and the printing apparatus is stopped, so that the operator can set the squeegee speed or check the remaining amount of paste by this alarm. Variations in the filling amount can be prevented in advance.

Next, experiments and experimental results conducted to confirm the effects of this embodiment will be described.

In Example 1, the filling process of the solder paste 17 filled in the printing opening 10 a of the metal mask 10 was observed by the second camera 14. In Example 1, a metal mask 10 having printing openings 10a of □ 300 μm and 500 μm is used, urethane rubber having a hardness of 80 is used for the squeegee 9, printing conditions are an attack angle of 60 degrees, a squeegee pressure of 0.1 MPa, The squeegee speed was 10 mm / s and the printing gap was 0 mm.

The process in which the solder paste 17 is filled in each printing opening 10a of the metal mask 10 is imaged by the second camera 14 through the glass substrate 11, and this image is directly observed by the first monitor 18. Recorded and saved.

FIG. 5 shows the observation results. FIGS. 5A to 5D are diagrams schematically showing paste-filled images captured by the second camera, and FIGS. 5A to 5D are based on observation results from the side. It is the schematic diagram of the paste filling state. Note that v is the moving direction (printing direction) of the squeegee.

The events revealed by the observation of the filling process are the initial stage of filling of the solder paste (first stage), the solder paste slip (second stage), the filling near the squeegee (third stage), and the squeegee tip. It was found that it can be divided into four stages of pushing in (fourth stage). Such a filling process is a new discovery different from what has been said so far.

Looking at the filling process in detail, in the first stage, the tip 17a of the solder paste 17 starts to pass over the printing opening 10a, and at the next moment when the printing opening 10a passes through the printing opening 10a, the tip 17a is printed in the printing opening 10a. It is approaching while being pressed against the front inner wall 10b (see FIGS. 5A and 5A). In the second stage, the solder paste 17 slips on the printing opening 10a and moves as it is (see FIGS. 5B and 5B). In the third stage, when the squeegee 9 moves to the edge of the printing opening 10a, the solder paste 17 is filled at once (see FIGS. 5C and 5C). In the fourth stage, the squeegee 9 pushes in the solder paste 17 while passing over the printing opening 10a (see FIGS. 5D and 5D).

In the first stage described above, the tip 17a of the solder paste 17 that has entered first is pressed firmly against the front inner wall 10b of the printing opening 10a, resulting in deterioration of plate separation described later, It was found that a stable printing thickness could not be obtained.

From this observation result, it is possible to prevent deterioration of plate separation by setting the printing conditions so that the amount of solder paste 17 entering in the first stage is as small as possible and the solder paste 17 is mainly filled in the third stage. I found. Specifically, the filling amount can be stabilized by increasing the squeegee speed.

In Example 2, the rolling state of the solder paste 17 was observed with the first camera 15. Specifically, using the image analysis software, the moving speed of the surface of the solder paste 17, that is, the rolling speed, was measured from the rolling diameter and squeegee speed of the solder paste 17.

As a result of image analysis in the rolling state, it is found that the rolling speed q is substantially proportional to the squeegee speed and the rolling diameter r, and the filling amount of the solder paste 17 in the first stage changes depending on the rolling speed q. did. This is because the rolling state of the solder paste 17 can be observed stably and accurately by moving the second camera 15 together with the squeegee 9.

FIGS. 6A to 6D are diagrams schematically illustrating images obtained by capturing the solder paste filling state in the first stage with the first camera when the rolling diameter and the squeegee speed are changed. The mask opening depth was 60 μm, and the printing opening was □ 500 μm.

According to this observation result, when the rolling diameter is 15 mm and 20 mm and the squeegee speed is slowed down to 10 mm / s, a paste having a width of about 200 μm is filled in the first stage (FIGS. 6A and 6B). c) See arrow ⇔). On the other hand, when the rolling diameter is set to 15 mm and 20 mm and the squeegee speed is increased to 75 mm / s, the paste is hardly filled in the first stage (see FIGS. 6B and 6D). This indicates that the filling amount of the solder paste in the first stage varies depending on the rolling diameter and the squeegee speed.

Such fluctuations in the filling amount are considered to be related to the rolling speed. That is, when the image of FIG. 6C is seen, the rolling speed is high, so that the amount of rotation of the solder paste surface per unit time is large, so that more paste is supplied to the printing openings. It can be seen that the filling amount of is increasing. 6B shows that although the rolling speed is high, the squeegee speed is also high, so that the paste passes before the printing opening enters and is not filled. . Further, when viewing the image in FIG. 6 (d), it can be seen that as a result of increasing the rolling diameter and increasing the rolling speed, the paste is slightly filled even at a squeegee speed equivalent to that in FIG. 6 (b). .

Therefore, in order to stabilize the paste filling amount, it is desirable to control the paste filling amount in the first stage. Specifically, it is necessary to manage the rolling speed determined by the rolling diameter and the squeegee speed, and the quality of screen printing can be improved by managing the rolling speed.

In Example 3, the state of separation of the metal mask 10 was observed with the third camera 16. In the third embodiment, the aspect ratio of the printing opening 10a is 0.27 in the A mode (opening diameter φ220 μm × opening depth t60 μm), 0.60 in the B mode (φ200 μm × t120 μm), and 0.66 in the C mode. (Φ180 μm × t120 μm), and the behavior of the solder paste at the time of releasing the plate was observed.

FIG. 7 is a schematic diagram showing the behavior of the solder paste when the plate is released. 7 (a) and 7 (a ') show the plate separation state in the A mode, and FIGS. 7 (b) and 7 (b') show the plate separation state in the B mode. Indicates a plate separation state in the C mode.

From the above observation results, it is new that when the solder paste 17 is separated from the metal mask 10, the paste 17 in close contact with the glass substrate 11 is stretched and deformed, and the solder paste 17 is divided when the plate separation further proceeds. Turned out.

In the case of the A mode with a reduced aspect ratio, it can be seen that the adhesiveness of the solder paste 17 to the glass substrate 11 is strong and the plate separation is good (see FIGS. 7A and 7A). On the other hand, in the case of the C mode, it can be seen that the adhesiveness between the solder paste 17 and the inner wall of the metal mask 10 is stronger than the adhesiveness between the solder paste 17 and the glass substrate 11, and the separation of the plate is deteriorated.

It is a block diagram for demonstrating the screen printing apparatus by one Embodiment of this invention. It is explanatory drawing of the rolling speed of the solder paste of the said screen printing apparatus. It is a flowchart for demonstrating operation | movement of the said screen printing apparatus. FIG. 9 is a flowchart for explaining the operation of the screen printing apparatus according to one embodiment of the invention of claim 5. It is a figure which shows the experimental result done in order to confirm the effect of the said embodiment. It is a figure which shows the experimental result done in order to confirm the effect of the said embodiment. It is a figure which shows the experimental result done in order to confirm the effect of the said embodiment.

Explanation of symbols

1 Screen printer 9 Squeegee 10 Metal mask (screen mask)
10a printing opening 11 glass substrate (substrate)
12 Control unit (squeegee speed control means)
17 Solder paste 14 First camera (printing process imaging camera)
15 Second camera (rolling imaging camera)
16 Third camera (separating camera)
23 Dispenser 24 Paste supply drive unit 25 Image analysis device (rolling speed calculation means)
q Rolling speed

Claims (7)

A screen mask in which a printing opening is formed is arranged on the upper surface of the substrate, and the paste supplied on the screen mask is moved in one direction by a squeegee to fill the paste in the printing opening of the screen mask. In a screen printing apparatus configured to print on a substrate, a rolling imaging camera that images the rolling state of the paste above the screen mask and on the front side in the moving direction of the squeegee, and analyzing the captured image A screen printing apparatus comprising: a rolling speed calculating means for calculating the rolling speed of the paste; and a squeegee speed controlling means for controlling the squeegee speed of the squeegee based on the calculated rolling speed. 2. The screen printing apparatus according to claim 1, wherein the squeegee speed control means is configured to lower the squeegee speed when the calculated rolling speed is higher than a predetermined value. 3. The screen printing apparatus according to claim 1, wherein the squeegee speed control means is configured to increase the squeegee speed when the calculated rolling speed is lower than a predetermined value. 4. The squeegee speed control means according to claim 1, wherein the squeegee speed control means is configured to supply a predetermined amount of paste to the screen mask when the calculated rolling speed is lower than a predetermined value. Screen printing device. 2. The screen printing apparatus according to claim 1, wherein the squeegee speed control means is configured to output an alarm signal when the calculated rolling speed is higher or lower than a predetermined value. 6. The printing process imaging camera according to claim 1, wherein a printing process imaging camera that images a filling process of a paste filled in a printing opening of the screen mask through the printing object is provided below the printing object. A screen printing apparatus. 7. The screen printing apparatus according to claim 1, wherein a plate separation imaging camera for imaging a screen separation state of the screen mask is disposed above the screen mask.

Images